Question on Pro Twin front forks

[Ivan]

Hey someone in the know

Would youplease beable to explain what is the best option to do to a SV650 front end for when I get myne to still be able to race it under Pro Twin rules.

What would be the best valving kit to get for it
And what other internal mods can you do I have had aread through rules but currently cant view PDF files so cant re read and there are a few guys who have actually developed protwins so just wondering

Ivan

[speights_bud]

APPENDIX F
650cc PRO TWIN
This class rules will apply to all National Championship and Endurance championship races.
At other meetings these rules will apply unless varied in the supplementary regulations, but
not contradicting the class rules.
Capacity Group
This class of motorcycle requires an MNZ Homologation with a minimum of 10 units sold of

that model per year.
This class to be called the 650cc Pro Twins.
All items not mentioned in the following articles must remain as originally produced by the
manufacturers remain fitted and operational for that homologated model.

1. Twin cylinder four strokes up to 650cc standard engines. (Only OEM engine
parts for that model may be fitted).

2. Number Plate Colours – Orange background with black numbers.

3. Fuel
This class must function on normal unleaded fuel with a maximum lead content
of 0.013g/l (unleaded) and a maximum RON of 98.

4. Tyres
Tyres V or Z rating must be used. Only tyres on general sale to the public in
New Zealand as road legal fitment will be permitted. For all events other than
endurance races only one set of tyres per meeting will be allowed for races
counting towards the MNZ championship.
Tyre warmers are allowed.
Wet tyres.
In the event that the track is damp/wet the choice of tyre is at the discretion of
the rider.
The DOT rule requirement for sports production wet tyres is suspended.
A full race wet tyre marked NOT FOR HIGHWAY USE may be used providing
that the tyre has a moulded tread pattern, any number of wets may be used.
Hand cut DOT approved sports production tyres and hand cut slicks may not be
used.

5. Machine Specifications (General)
All machines must comply with the relevant general competition Rules such as
Chapter 10.
Machines with rebored cylinders must remain within that models OEM
capacity limits (ie: second oversize, .5mm).

6. Modifications Allowed
a. The front fork inner (slide pipe stanchion) and the outer (outer stanchion)
must remain as per the original manufacturers OEM parts for that

[speights_bud]

homologated model. Damper Rods, fitment of emulators, springs and valving
may be changed for suspension timing purposes.
Complete cartridge replacement with non-OEM parts is not permitted.
Quality and quantity of oil in forks.
The height and position of the front fork in relation to the top yoke (fork crown)
is free.
b. Cam wheels (sprockets) may be slotted.
c. Undercutting and shimming of gearbox.
d. Rear Suspension unit (Rear Shock) may be replaced. The link arm may be
changed or modified but the suspension linkage must remain standard,
original attachments to the frame must be used.
e. Exhaust system
f. Drive sprockets
g. Steering damper
h. Handle bars
i. Instrument panel
j. Foot rest/Foot controls, must be mounted to the frame at the original
mounting point.
k. Small protective cones may be fitted to minimize accident damage.
l. Brake disc pads.
m. Brake lines front and rear.
n. Spark plugs
o. Carburettor jetting and slides
p. A fuel tuning device ie Power commander may be used.
q. Ignition, Engine control module/unit (ICM, ECU, ECM) and wiring loom
must remain standard.
Fairing/Body Work
Accessory aftermarket fairing, front guard and bodywork may be fitted.
The use of carbon fibre is restricted to the reinforcing mounting parts (area) only.
Windscreen may be replaced.
The original combination instrument/fairing brackets.
The following items must be altered or removed
Passenger footrests/grab rails, chain guard
Safety bars, centre stands (fixed welded brackets must remain)
Where breather or over flow pipes are fitted they must discharge via existing outlet. The
original closed system must be retained; no direct atmospheric emission is permitted.
Headlight, rear light and blinkers must be removed.
Horn
Licence plate bracket

[speights_bud]

The following may be removed
Instruments, brackets and associated cables
Toolbox
Speedometer
Radiator fan and wiring
Items not allowed
No Data logging
Additional equipment not on the original homologated motorcycle may not be added (ie; data
acquisition computers, recording equipment)
The fitment of aftermarket Traction Control units is not permitted.

[Robert Taylor]

Hey someone in the know

Would youplease beable to explain what is the best option to do to a SV650 front end for when I get myne to still be able to race it under Pro Twin rules.

What would be the best valving kit to get for it
And what other internal mods can you do I have had aread through rules but currently cant view PDF files so cant re read and there are a few guys who have actually developed protwins so just wondering

Ivan

Essentially for that bike you are allowed to fit emulators and springs but are not allowed to fit aftermarket cartridges.

This is a relatively low cost mod but its also easy to do it badly. Enlarging and adding extra holes in the bottom of the damper rods ( as per Race Tech suggested method ) MUST NOT be done in this way as you actually end up with a dead area of high speed rebound damping. Dirt bikes with 300mm of travel can get away with it, but not road race bikes with 120mm of travel. I have had this conversation directly with Paul Thede and he agrees with what I have stated.

As a brazen pitch for my business doing the job we supply Ohlins superbike springs as part of the package, the advantage here being is that we stock all the rates. If you find that you end up needing a slightly different rate to those supplied we exchange at no cost excepting courier recovery costs. Further advantages of these springs is that they are highly polished so there is less internal wall rubbing friction and they are very short but still with adequate stroke integrity. Short springs means less coils to rub and create friction and rapid oil contamination, also weight reduction.
Another thing to bear in mind is that damper rod forks are very viscosity and ambient temperature sensitive. Because there is so much badly controlled bleed they must neccessarily run around 15 weight oil in winter and 20 weight in summer, although personally I prefer to see only what centistroke rating the oils are as the only true indicator of flow rate. Such relatively thick oils can vary in characteristic enormously over the course of a day. First thing in the morning the rebound speed can be very lethargic, and yet in the middle of the day when the suns out the rebound speed is appreciably faster. For that reason dont fill it with a cheap oil that has widely varying flow chracteristics according to temperature. I dare not say it in print but there is also one high profile brand of oil that a lot of people have been duped into using in their forks that has very poor corrosion resistance properties.
The set up we provide is very well dialed and we are always available for set up advice.

[cowpoos]

Hey someone in the know

Would youplease beable to explain what is the best option to do to a SV650 front end for when I get myne to still be able to race it under Pro Twin rules.

What would be the best valving kit to get for it
And what other internal mods can you do I have had aread through rules but currently cant view PDF files so cant re read and there are a few guys who have actually developed protwins so just wondering

Ivan
I got a question for you...why don't you keep racing your rs125?? like so many people reckon you should??..and save any money you have for the mean time??

[Ivan]

I got a question for you...why don't you keep racing your rs125?? like so many people reckon you should??..and save any money you have for the mean time??


Ive talked to a few people and they believe its the right step for me to take.
Also its alot more practical for me. me being 6"1 and 67kgs on a 125 is INSTANT horsepower loss the power to weight ratio is set against me big time.

I also want the challenge of a new bike and working with it and plus I dont own my 125. but I will own this bike and I wpuld preferto own my own race bike.

[Ivan]

Essentially for that bike you are allowed to fit emulators and springs but are not allowed to fit aftermarket cartridges.

This is a relatively low cost mod but its also easy to do it badly. Enlarging and adding extra holes in the bottom of the damper rods ( as per Race Tech suggested method ) MUST NOT be done in this way as you actually end up with a dead area of high speed rebound damping. Dirt bikes with 300mm of travel can get away with it, but not road race bikes with 120mm of travel. I have had this conversation directly with Paul Thede and he agrees with what I have stated.

As a brazen pitch for my business doing the job we supply Ohlins superbike springs as part of the package, the advantage here being is that we stock all the rates. If you find that you end up needing a slightly different rate to those supplied we exchange at no cost excepting courier recovery costs. Further advantages of these springs is that they are highly polished so there is less internal wall rubbing friction and they are very short but still with adequate stroke integrity. Short springs means less coils to rub and create friction and rapid oil contamination, also weight reduction.
Another thing to bear in mind is that damper rod forks are very viscosity and ambient temperature sensitive. Because there is so much badly controlled bleed they must neccessarily run around 15 weight oil in winter and 20 weight in summer, although personally I prefer to see only what centistroke rating the oils are as the only true indicator of flow rate. Such relatively thick oils can vary in characteristic enormously over the course of a day. First thing in the morning the rebound speed can be very lethargic, and yet in the middle of the day when the suns out the rebound speed is appreciably faster. For that reason dont fill it with a cheap oil that has widely varying flow chracteristics according to temperature. I dare not say it in print but there is also one high profile brand of oil that a lot of people have been duped into using in their forks that has very poor corrosion resistance properties.
The set up we provide is very well dialed and we are always available for set up advice.

Cool I may have a bike already set up but I may get hold of you about it and send up and get you yo pull it down and service it and also set it up if you can for my weight etc?

[speights_bud]

i rode a completely stock SV650 (naked Version) except for a short scorpion ex pipe , at manfield a few weeks ago, it was my first time on a big bike at manfield and first time riding since december.
I was doing 1:20's on it. whats that like for pro twins?

The bike was running lean from about 10k to the red and suspension was stock/nothing flash, not to mention the stock brake pads :pinch:.

[Shaun]

1 23 Karl Morgan 1:15.419 15 144.775 15 -
2 45 Tom Bos 1:17.693 7 140.538 2.274 2.274 11 -
3 12 David Cook 1:17.802 5 140.341 2.383 0.109 5 -
4 67 Geoff Booth 1:17.993 6 139.997 2.574 0.191 8 -
5 212 Anthony Stephens 1:18.677 6 138.780 3.258 0.684 16 -
6 210 Alan Zitnik 1:18.826 8 138.518 3.407 0.149 8 -
7 217 Paul Barnard 1:25.149 14 128.232 9.730 6.323 14 -
8 204 Raymond Nairn 1:28.131 5 123.893 12.712 2.982 13 -

[johnsv650]

hi ivan,
good luck with protwins, theres about 4 or 5 more down in the south island, some older guys and some from the super strong streetstock class....
robert Taylor and shawn on kb will helping you with suspension, just one tip , get the best first time, helps develope faster......dunlop tyres also.

[Ivan]

My tires will be Conti Race Attacks

[speights_bud]

1 23 Karl Morgan 1:15.419 15 144.775 15 -
2 45 Tom Bos 1:17.693 7 140.538 2.274 2.274 11 -
3 12 David Cook 1:17.802 5 140.341 2.383 0.109 5 -
4 67 Geoff Booth 1:17.993 6 139.997 2.574 0.191 8 -
5 212 Anthony Stephens 1:18.677 6 138.780 3.258 0.684 16 -
6 210 Alan Zitnik 1:18.826 8 138.518 3.407 0.149 8 -
7 217 Paul Barnard 1:25.149 14 128.232 9.730 6.323 14 -
8 204 Raymond Nairn 1:28.131 5 123.893 12.712 2.982 13 -

Cheers Shaun,
I've got a bit of work to do then :) a challenge is always good!

[Ivan]

Yeah I am only worried about getting the front end set up as i have said I am going to buy and race a Penske in the back and believe from waht have seen the Conti Race Attack tires are the bees knees as well.
Hoping to have me a bike soon and get some pre season Testing done.

[quallman1234]

Don't be blaming the bike now Ivan, Might pop round on friday with glen. Catch ya.

[HDTboy]

I am going to buy and race a Penske in the back

Why not talk directly with your Penske supplier for the best option to compliment his shock? Rather than treating your motorcycle like it's a parts catalog special, perhaps you could build it as a package.

[Ivan]

Allready have talked to him
This is an old thread now lol.

[Shaun]

Why not talk directly with your Penske supplier for the best option to compliment his shock? Rather than treating your motorcycle like it's a parts catalog special, perhaps you could build it as a package.



Thanks for that mate. As of NOW THOUGH, Robert Taylor ( And who i really hope) from CKT will be doing all my fork work! I have done a sub contractor deal with Robert, where any fork work I have said I will do for a customer, WILL BE DONE @ CKT ( Robert T)

I will be a sales rep and set up person for riders with either Penske, (Ohlins and other CKT Product) and Traxxion fork kits, GAS CHARGED or AK20.

This means, that any rider using either product, can use me or CKT at the race track or on here, to help them make there bikes handle better/safer!

Working together with Robert again closely like this, is a win win for all involved, riders and us as well.

[svr]

This is a relatively low cost mod but its also easy to do it badly. Enlarging and adding extra holes in the bottom of the damper rods ( as per Race Tech suggested method ) MUST NOT be done in this way as you actually end up with a dead area of high speed rebound damping. Dirt bikes with 300mm of travel can get away with it, but not road race bikes with 120mm of travel. I have had this conversation directly with Paul Thede and he agrees with what I have stated.

As a brazen pitch for my business doing the job we supply Ohlins superbike springs as part of the package, the advantage here being is that we stock all the rates. If you find that you end up needing a slightly different rate to those supplied we exchange at no cost excepting courier recovery costs. Further advantages of these springs is that they are highly polished so there is less internal wall rubbing friction and they are very short but still with adequate stroke integrity. Short springs means less coils to rub and create friction and rapid oil contamination, also weight reduction.
Another thing to bear in mind is that damper rod forks are very viscosity and ambient temperature sensitive. Because there is so much badly controlled bleed they must neccessarily run around 15 weight oil in winter and 20 weight in summer, although personally I prefer to see only what centistroke rating the oils are as the only true indicator of flow rate. Such relatively thick oils can vary in characteristic enormously over the course of a day. First thing in the morning the rebound speed can be very lethargic, and yet in the middle of the day when the suns out the rebound speed is appreciably faster. For that reason dont fill it with a cheap oil that has widely varying flow chracteristics according to temperature. I dare not say it in print but there is also one high profile brand of oil that a lot of people have been duped into using in their forks that has very poor corrosion resistance properties.
The set up we provide is very well dialed and we are always available for set up advice.

Exactly! I rode my SV with a GSXR1000k2 front end for 4 years and swapped back to standard with springs and emulators for some summer protwin races - the big thing is that the oil viscosity varies HEAPS with temperature changes (thanks Robert), adjustment is a pain in the arse, and having the fork set up with enough overall compression damping means harsh high speed compression damping. Is that from crude damping or high stiction?

[Robert Taylor]

Exactly! I rode my SV with a GSXR1000k2 front end for 4 years and swapped back to standard with springs and emulators for some summer protwin races - the big thing is that the oil viscosity varies HEAPS with temperature changes (thanks Robert), adjustment is a pain in the arse, and having the fork set up with enough overall compression damping means harsh high speed compression damping. Is that from crude damping or high stiction?

A bit of both but given time ( and there is never enough of that ) I would like to experiment with a set of emulators with smaller size low speed bleed bypass holes in the poppett, combined with less preload on the stock 64lb springs or slightly more preloaded 40lb poppett springs. Essentially more low speed damping combined with less high speed. So many ways to skin the cat!

One day I am going to dyno an emulated fork.

[Ivan]

Quick question.

I rode my SV yesterday it was great.
Only problem is it has racetech emulators in it and 9 KG springs which I dont think the springs are suited for me, It was Geoff Booths old K1.
The problem I was having was under braking at Taupo especially off the long back straight I was having quite a big Dive in the suspension and I want a firmer front end, to make myself more confident of harder braking.

Could I resolve this issue by putting 10KG springs?

Any Help Appreciated

[HDTboy]

Why not talk directly with your Penske supplier for the best option to compliment his shock? Rather than treating your motorcycle like it's a parts catalog special, perhaps you could build it as a package.

This guy'd be good to listen to

[Ivan]

This guy'd be good to listen to

Im not running a Penske in it at the mo I will be tho when Finances allow.
its just a GSXR750 shock in it at momment.
I asked on here incase Robert or Shaun replyed.

I dont like PMing people its annoying for them and I dont want to waste anyones time on a question like this when Joe Average may know of a reason etc.

[Robert Taylor]

Quick question.

I rode my SV yesterday it was great.
Only problem is it has racetech emulators in it and 9 KG springs which I dont think the springs are suited for me, It was Geoff Booths old K1.
The problem I was having was under braking at Taupo especially off the long back straight I was having quite a big Dive in the suspension and I want a firmer front end, to make myself more confident of harder braking.

Could I resolve this issue by putting 10KG springs?

Any Help Appreciated

The 9s will indeed be too light but 10s may be too heavy. What is your personal height and weight in your everyday clothes?

[GSVR]

Im not running a Penske in it at the mo I will be tho when Finances allow.
its just a GSXR750 shock in it at momment.
I asked on here incase Robert or Shaun replyed.

I dont like PMing people its annoying for them and I dont want to waste anyones time on a question like this when Joe Average may know of a reason etc.

As well as the springs you could check to make sure you have the right oil level in each fork leg. And also check that the emulator relieve port springs are wound up to the sportier recommendation.

Another thing you could do it put some spacers in to put more preload on the springs. Just 5 or 10mm can make a big difference to how the bike feels.

I'd like to know what year GSXR shock you have fitted and if the spring is standard. These are generally to soft. That and the fact you have the fork legs up through the triples may make your pegs bottom out early. Aftermarket rearsets are around 25mm up and back. Was Geoff running standard rearsets when he raced it?

Congrats on the bike Ivan you will have a blast.

[Ivan]

The 9s will indeed be too light but 10s may be too heavy. What is your personal height and weight in your everyday clothes?

Ok I will find some scales and weigh myself but my height is 6 foot 1
and my rough guess to weight is 67kgs

[Ivan]

As well as the springs you could check to make sure you have the right oil level in each fork leg. And also check that the emulator relieve port springs are wound up to the sportier recommendation.

Another thing you could do it put some spacers in to put more preload on the springs. Just 5 or 10mm can make a big difference to how the bike feels.

I'd like to know what year GSXR shock you have fitted and if the spring is standard. These are generally to soft. That and the fact you have the fork legs up through the triples may make your pegs bottom out early. Aftermarket rearsets are around 25mm up and back. Was Geoff running standard rearsets when he raced it?

Congrats on the bike Ivan you will have a blast.

Geoff said he put heavier oil in the rear shock. The spring has a sticker on it with a number its yellow I can get you that number if you like I do not know what year 750 it is but it has compression and rebound as well as preload for the spring.
I was actually thinking of spacers but didnt know if this was the right way to skin the cat.
I think I might get omeone who knows a thing or 2 about these to check the emulators out asI dont want to muck around and make a pile of junk.
I dont know if Geoff was because there are no peg scrape marks on the peg from him and I guessed he would have pegged it.
I was going to get a aluminum bracket machined up that raises them I dont really wanna put them back as they fell fine were they are.


What are these spacers you talk of can I buy them through a bike shop?

[GSVR]

Geoff said he put heavier oil in the rear shock. The spring has a sticker on it with a number its yellow I can get you that number if you like I do not know what year 750 it is but it has compression and rebound as well as preload for the spring.
I was actually thinking of spacers but didnt know if this was the right way to skin the cat.
I think I might get omeone who knows a thing or 2 about these to check the emulators out asI dont want to muck around and make a pile of junk.
I dont know if Geoff was because there are no peg scrape marks on the peg from him and I guessed he would have pegged it.
I was going to get a aluminum bracket machined up that raises them I dont really wanna put them back as they fell fine were they are.


What are these spacers you talk of can I buy them through a bike shop?

Geoff was quick on it when he was racing and would have it set up ok.

The rearset risers are an easy way to go but you should also carry some spares for these parts as one minor off can ruin your day if you happen to snap a rearset and don't have a spare.

The spacers are nothing special and even washers the right size would do. If you know someone with a lathe they could machine up a couple of sizes in a short time.

Probably the best preparation you can do at the moment is just riding the bike. Your've identified a couple of things you want to change ie the forks diving and the footpegs. After your've done that then decide what you next thing will be. Good new sticky tyres are always a plus but it comes down to budget how often you put new ones on.

Didn't Terry Fitzgerald borrow this bike for a race down south this year when he binned his bike?

[Ivan]

Geoff was quick on it when he was racing and would have it set up ok.

The rearset risers are an easy way to go but you should also carry some spares for these parts as one minor off can ruin your day if you happen to snap a rearset and don't have a spare.

The spacers are nothing special and even washers the right size would do. If you know someone with a lathe they could machine up a couple of sizes in a short time.

Probably the best preparation you can do at the moment is just riding the bike. Your've identified a couple of things you want to change ie the forks diving and the footpegs. After your've done that then decide what you next thing will be. Good new sticky tyres are always a plus but it comes down to budget how often you put new ones on.

Didn't Terry Fitzgerald borrow this bike for a race down south this year when he binned his bike?

He Might have.

Yeah i am not one for liking to muck around but I want ti so I feel comfortable pushing into corners without huge front end dive.
The tires are probably a meeting old and are Conti Race Attacks I cant say anything about them they were just brilliant once they got heat in them and surprisingly low tire pressures in the rear 23PSI!!!!!
I have done a quick fix and removed the peg Bobbons as that gives me an extra 10 mm clearence. Currently the budgetis low and am planning onjust riding the thing. Just want to sort mainly the suspension issue and itl be perfect

[Robert Taylor]

Ok I will find some scales and weigh myself but my height is 6 foot 1
and my rough guess to weight is 67kgs

You need .95 SPRINGS with preload set so that static sag is between 20 -25mm depending on available grip. PM me for the rest of the info.

[JJ58]

One day I am going to dyno an emulated fork.

You'll be shocked... The emulators are definetly only band aids. The cartridges offer a much better feel but are a pain to adjust, unlike the emulators which can be popped out in less than 15mins and adjusted between sessions.

With the SV fork there is a hydrualic bottom out device that needs to be modified to reduce it's stiction, otherwise you'll find your forks hydrualic locked under braking.

[Robert Taylor]

You'll be shocked... The emulators are definetly only band aids. The cartridges offer a much better feel but are a pain to adjust, unlike the emulators which can be popped out in less than 15mins and adjusted between sessions.

With the SV fork there is a hydrualic bottom out device that needs to be modified to reduce it's stiction, otherwise you'll find your forks hydrualic locked under braking.

I agree with what you are saying but that is all the rules will allow to pay credence to a ''it must be as cheap as possible'' philosophy in those rules.
Moreover with all damper rod forks there is so much relatively uncontrolled rebound bleed that you have to run a ''heavy'' fork oil. That means that damper rod forks are way way more sensitive to the atmospheric temperature of the day.
If anyone wants to verify what I am saying remove a damper rod fork from your bike and bounce up and down on it on a less than 10 degree celsius day. Then warm the fork lower with a heat gun and let it heat soak for 20 minutes or more, stabilised temperature of around 20 to 25 degrees celsius ( i.e to emulate summer racing temps ). You will be shocked at the massive difference in rebound return speed. If you run cheap ''budget'' oil the difference will be more marked as there will be a much wider disparity between cold and hot flow ratings.
Emulators only sort out part of the problem with these stone age technology forks. Cheapness comes at a price, sometimes that includes crashing because the rebound speed is way too lethargic at cold temps and the team hasnt changed the oil viscosity to account for those conditions.

[FROSTY]

Does this suggest then Robert that a clever pro towins guy would not only have tyre warmers but perhaps fork leg warmers too?
semi serious question


Advantage there I supose is the pretty boy racers could style their hair between races :whistle:

[cowpoos]

Does this suggest then Robert that a clever pro towins guy would not only have tyre warmers but perhaps fork leg warmers too?
semi serious question


Advantage there I supose is the pretty boy racers could style their hair between races :whistle:
I would imagine that with the forks would quickly drop to the ambient temp of the day or less if its wet.

[Robert Taylor]

Does this suggest then Robert that a clever pro towins guy would not only have tyre warmers but perhaps fork leg warmers too?
semi serious question


Advantage there I supose is the pretty boy racers could style their hair between races :whistle:

Poos has answered the question, forks run at slightly less than ambient temperature due to being right in the cooling airstream. So the guys that are serious would change oil viscosity for the conditions.

It does though make sense to have a shock warmer

[GSVR]

Don't hydraulic systems warm up when they are doing work like absorbing shock loads? What happends to all the energy thats absorbed?

Some guy on here was saying his standard rear shock got so hot he couldn't touch it. Why are the front forks any different?

[FROSTY]

Don't hydraulic systems warm up when they are doing work like absorbing shock loads? What happends to all the energy thats absorbed?

Some guy on here was saying his standard rear shock got so hot he couldn't touch it. Why are the front forks any different?
My thinkin exactly --kinda like tyre warmers--the work of goin upn down would keep the legs warm.
Holey shit---I can see it now. Mr speedracer 123 is up due for his first race of his career. His ever vigulent crew wait thill the last moment before removing tyre warmers,front shock warmers,rear shock warmers and patented seat warmer.
With a full grid of 35 bikes the national grid heaves a sigh of releif as all this gear is turned off.

[cowpoos]

Don't hydraulic systems warm up when they are doing work like absorbing shock loads? What happends to all the energy thats absorbed?

Some guy on here was saying his standard rear shock got so hot he couldn't touch it. Why are the front forks any different?


forks run at slightly less than ambient temperature due to being right in the cooling airstream.

It does though make sense to have a shock warmer
and the rear shock is out of the airstream and is also warmed by engine heat aswell.

[GSVR]

I'm thinking heated handgrips might be a better investment for the winter series. 10 mins waiting on the dummy grid and everything is stone cold anyway.

[Robert Taylor]

and the rear shock is out of the airstream and is also warmed by engine heat aswell.

And there is so much mass of metal to absorb heat as well. We have tested this sometime ago.

[cowpoos]

I'm thinking heated handgrips might be a better investment for the winter series. 10 mins waiting on the dummy grid and everything is stone cold anyway.
lol good call gary!! heated hand grips and a hotwater bottle!!

there should still be plenty of heat left in tyres,etc after 10mins waiting on the dummy grid...the surface of the tyres may be cold..but the carcuss and rim should and would have heat still in it.

[GSVR]

and the rear shock is out of the airstream and is also warmed by engine heat aswell.

Yeah that rear shock on the SV must really be a hard on to get right in winter with the exhaust and engine heat. Its temp range must be huge compared to the front. Rear shock heater would be a necessity to get it even close to working right.

[Pussy]

Even in a road bike set up, we ended up getting RT to put lighter weight oil in the forks of Gassit girl's K1 SV650 for the winter months. The rebound was too lethargic otherwise. For some reason the K5 SV650 was able to run the same weight oil year round

[Robert Taylor]

And there is so much mass of metal to absorb heat as well. We have tested this sometime ago.

I also hasten to add that there is approximately 5 - 6 times the volume of oil across two forks compared to a typical rear shock, so there is a massive amount more oil to heat. Allied to that each fork leg has approximately only 15 - 20% of the damping force of a typical rear shock at kerb strike velocity. Less damping equals much less heat build up

[Robert Taylor]

Even in a road bike set up, we ended up getting RT to put lighter weight oil in the forks of Gassit girl's K1 SV650 for the winter months. The rebound was too lethargic otherwise. For some reason the K5 SV650 was able to run the same weight oil year round

There in fact would still have been variance, just less obvious. And this was because of precision remachining on the damper rods to actually get them to sit on the same centreline as the fork tubes! Thereby giving less bypass, but this adds to the cost, inevitably.

[Pussy]

There in fact would still have been variance, just less obvious. And this was because of precision remachining on the damper rods to actually get them to sit on the same centreline as the fork tubes! Thereby giving less bypass, but this adds to the cost, inevitably.

It was worth the coin though, Rob. Those forks performed great!

[Robert Taylor]

Yeah that rear shock on the SV must really be a hard on to get right in winter with the exhaust and engine heat. Its temp range must be huge compared to the front. Rear shock heater would be a necessity to get it even close to working right.

Please beat me with a stick if you havent thought about it in this way, plus to clarify for all those reading this thread;

1) Forks will run at ambient temperature or slightly below due to being in the cooling airstream, having relatively light damping which lessens any heat build up, ''generous'' oil volume and lots of highly heat conductive alloy to carry heat away, etc.
The ideal trick is to engineer the forks so you can run as light an oil viscosity as possible, light viscosity oils are much less affected by temperature variance compared to heavier oils. Sadly the cost of re-engineering many oem forks to run very thin oils can be a chequebook exercise.
Dont use cheap oil! Because among other reasons the flow characteristics with cheap oil has a much greater variance than with more refined / sophisticated oils.
More and more we have been using Ohlins oil as we have found fork performance is much much better at low temperatures than anything else we had previously used...and we always selected on quality and performance as opposed to cost. Craig Shirriffs will verify.
There must be something with this Ohlins oil, they make a big number of snowmobile shocks which obviously get operated at cold temps, neccessitating oil with great cold flow characteristics. Sorry if this sounds like a commercial plug but we have conclusively proven the performance of this oil.

2) Rear shocks have much more aggressive damping and typically in a road / road race shock the oil capacity may only be 150 to 200mls. Also operating behind a hot engine / exhaust that all means a recipe for heat build up.
The first outing of the day will start with a relatively cold shock which means slightly lethargic performance. ( Excepting if the damping is already weak meaning youd want to keep that shock chilled! )
If you can therefore pre-heat that shock with a warmer ( I dont want any moronic suggestions about using heat guns or a kettle ) then you will have achieved first laps performance a lot closer to how the shock will ''temperature stabilise'' a few laps in.
Again, running a high quality oil and ensuring that the oil is as air free as posssible is an obvious. Shocks with gas bladders ( oem ) require much more frequent service than floating piston type.
Nothing magic about all this, its just physics and sitting down and thinking about it.

[GSVR]

Quite a difference with winter vs summer. Havent really given the suspension warmup times any thought but have heard it mentioned at race meets.

So the front end doesn't need any warm up as the temp of is components stays pretty close to ambient. Little confussed now over those fork leg warmers people sell.

And the back I can see gets a big workout. And can start from cold and get hot from various sources which stangely it isn't sheilded from nor is there any ducting to supply cooling to this area.

Front forks are like overkill and its a wonder wishbone suspensions aren't more common on bikes as they seem to have advantages like only one shock to tune.

[Pussy]

Front forks are like overkill and its a wonder wishbone suspensions aren't more common on bikes as they seem to have advantages like only one shock to tune.
I reckon weight and complexity might be a factor. Forks have come a long way in the last 20 or so years. On my wishlist is for a system to be invented for damper rod forks to upgrade the compression AND rebound performance... sort of like the present emulators, but with a controlled rebound too

[Robert Taylor]

Quite a difference with winter vs summer. Havent really given the suspension warmup times any thought but have heard it mentioned at race meets.

So the front end doesn't need any warm up as the temp of is components stays pretty close to ambient. Little confussed now over those fork leg warmers people sell.

And the back I can see gets a big workout. And can start from cold and get hot from various sources which stangely it isn't sheilded from nor is there any ducting to supply cooling to this area.

Front forks are like overkill and its a wonder wishbone suspensions aren't more common on bikes as they seem to have advantages like only one shock to tune.

In fact quality shocks with excellent thermal expansion characteristics and QUALITY shock oil are calibrated to run at high temps. The right rear shock on a Toyota racing series car runs at close to 120 degrees celsius because it is right next to the exhaust muffler. As long as high quality oil is used they can run a full season of racing. High temps like this are common in Formula cars as many damper installations are on top of the gearbox which runs very hot.
I suspect fork warmers are there purely for some people to make money, its a little akin to thermal barrier coatings on two stroke exhausts, technically its a crock. Its also a bit like those low crotch hanging pants that homies wear, they make think its fashionable but just how stupid and impractical they are!
We are not seeing wishbone front suspension en-masse because the reality will be that the market wont accept it en-masse, despite the technical benefits, albeit it with some shortcomings ( but Im not of sate of mind to get into that one! ) For example the early 90s GTS1000 Yamaha.

[Robert Taylor]

I reckon weight and complexity might be a factor. Forks have come a long way in the last 20 or so years. On my wishlist is for a system to be invented for damper rod forks to upgrade the compression AND rebound performance... sort of like the present emulators, but with a controlled rebound too

Dont hold your breath on that one.