Puke suspension, soft or hard ?

[Quasievil]

on the GSXR400 F3 bike Ive got my front set up so it dives about half way under brakes at the end of the straight at puke, is that right ?
I was in at F1 engineering yesterday Steve reckons I need to have it travel up to about 20mm of its total travel capacity.
On the last track day I found the bike very unsettled onto and out of the front straight especially coming into jenian with the bumps it made me go out a bit wider than planned.
Keen to hear your thoughts

Also what and where should the rear be set in relation to the front ?

Thanks guys n gals

[Riff Raff]

Well I imagine if you puke on your suspension, over time it will become quite soft.

[Hoon]

It depends on how bumpy the rest of the track is for you. Just because you have travel to spare doesn't necessarily mean you have to use it. If its too hard for the rest of the track you can afford to go softer but I wouldn't want to go any harder.

Also consider whether you are braking at the limits at the hairpin. If you are wussing out on the brakes then it will show less front dive.

Best bet is to talk to other gsxr400 racers on Sun and compare settings. Also don't get too hung up on bike settings. At this stage 90% of your gains will come from upstairs and messing with the bike all the time can distract you from where you should be focusing.

[Quasievil]

It depends on how bumpy the rest of the track is for you. Just because you have travel to spare doesn't necessarily mean you have to use it. If its too hard for the rest of the track you can afford to go softer but I wouldn't want to go any harder.

Also consider whether you are braking at the limits at the hairpin. If you are wussing out on the brakes then it will show less front dive.

Best bet is to talk to other gsxr400 racers on Sun and compare settings. Also don't get too hung up on bike settings. At this stage 90% of your gains will come from upstairs and messing with the bike all the time can distract you from where you should be focusing.


Cheers mate long time no hear to, see you on Sunday mate

[geoffm]

on the GSXR400 F3 bike Ive got my front set up so it dives about half way under brakes at the end of the straight at puke, is that right ?
I was in at F1 engineering yesterday Steve reckons I need to have it travel up to about 20mm of its total travel capacity.
On the last track day I found the bike very unsettled onto and out of the front straight especially coming into jenian with the bumps it made me go out a bit wider than planned.
Keen to hear your thoughts

Also what and where should the rear be set in relation to the front ?

Thanks guys n gals

Have you set the static sag? You want to use around 25-30% of the travel when you sit on it from fully unloaded (wheels off the ground). This is to allow the wheel to follow bumps without topping out. Adjust this with the preload. Preload doesn't affect the spring rate, once the fork is moving, but it affects the initial stiffness until it starts moving. To high and it will skip over the bumps without moving, and you won't have the travel for the wheel to follow dips.
Put a cable tie around the fork leg and see how much it dives under brakes. It shouldn't bottom out but use most of the travel. Adjust this with the spring rate. Without different springs, you will have to use different weight oil. Increasing the oil weight increases both the compression damping and rebound damping. If it is to high, the forks move to slowly and will top out over a series of bumps and skip (Jacking up) and will dive and not bounce back in time for the next bump (jacking down). To low and it pogos as it can't control the spring travel rate. It is a try it and see exercise.


When I am finally back in Auckland permanently, we should have a get-together on a track day, and I will sort out my Datamite on-board data aquisition system and people can have a go with it.
It is the black box that runs my dyno, but i have a spare loom, and should use it. Any electronic geeks out there want to look at a linear potentiometer system as the sensor component for the suspension travel? At present it just picks up RPM and wheel rotation
Geoff

[GSVR]

I downloaded a manual from here some time back. Think it was the "Road and Track" one.

http://www.ohlins.com/mc_manuals.shtml

Has excellent section on setting up suspension for someone like me that doesn't know alot.

All the info on correct sag dampening etc. And what to do to fix various handling problems.

Good luck on Sunday.

[FROSTY]

Quazi if it helps --From my limited experience a softer setting at the rear made jennian a bit motre managable -and again if it helps i get a head shake almost every time I go over the top of the "hill"

[Two Smoker]

-and again if it helps i get a head shake almost every time I go over the top of the "hill"

der is a smoover line daniel san....

Go for slightly softer Brett, its a bumpy track...

[FROSTY]

der is a smoover line daniel san....

Go for slightly softer Brett, its a bumpy track...
its not rough/smooth -its the front end going light that does it for me

[cowpoos]

der is a smoover line daniel san....

Go for slightly softer Brett, its a bumpy track...

Firmer springs...[ie slightly harder preload....about 30-35mm rider sag front...15-20mm rear]softer compresion and quik-ish rebound!!!

at both ends...

[cowpoos]

Preload doesn't affect the spring rate, once the fork is moving, but it affects the initial stiffness until it starts moving. To high and it will skip over the bumps without moving, and you won't have the travel for the wheel to follow dips.
Put a cable tie around the fork leg and see how much it dives under brakes. It shouldn't bottom out but use most of the travel. Adjust this with the spring rate. Without different springs, you will have to use different weight oil. Increasing the oil weight increases both the compression damping and rebound damping. If it is to high, the forks move to slowly and will top out over a series of bumps and skip (Jacking up) and will dive and not bounce back in time for the next bump (jacking down). To low and it pogos as it can't control the spring travel rate. It is a try it and see exercise.



EWrrr....right....first...preload does affect the spring rate...you have wound on extra force so it is a theretical higher rated spring...using different rate oils affects comp and rebound...nothing to do with spring's....another subject...and again...nothing to do with springs...

interesting how you go straight to oil levels with out explaining how your theory affects springs...hmmm...what you seem to be explaining about oil levels...has more relievence to rebound damping...oil levels affect both rebound and comp damping...

It seems to me you do alot of trial and error....and I would say...you have alot of error...

There is alot of contradictions in what you have said...best you stop giving advice until you go and learn more about the subject of suspension tuning...okay :laugh:

[TwoSeven]

I would say, set the bike up for the average bump damping at your average track speed and bugger the corner at the end of the straight. Unless you have modded your forks for both high and low speed damping, I suspect you wont get a one size fits all setting.

Basically under your heaviest braking you still want the rear wheel on the ground. If its lifting you are two hard on the front. If its too soft, you'll probably encounter some form of head shake. Its good for a ballpark.

[dss3]

Jeeze mate have you managed to make any sense from all these answers? Back to the soft v hard question... YOUR SOFT, practise RIDING HARD!! :whistle: :devil2:

[mikey]

just ride faster. worrying about shit like that is goign to slow you down. when your as quick as (someone reaaaaaaaaaaaaaaally fasts name or me or not) then start worrying about that type of shit.

[Quasievil]

Jeeze mate have you managed to make any sense from all these answers? Back to the soft v hard question... YOUR SOFT, practise RIDING HARD!! :whistle: :devil2:

Good call Darryl, wanna get drunk tomorrow night mate ?

[geoffm]

EWrrr....right....first...preload does affect the spring rate...you have wound on extra force so it is a theretical higher rated spring...using different rate oils affects comp and rebound...nothing to do with spring's....another subject...and again...nothing to do with springs...


Ahh, no. Preload is for the static sag, it doesn't affect the spring rate (slope of the force/distance plot). http://www.sportrider.com/tech/146_9510_tech/ explains it nicely. This assumes you haven't got progressive or variable rate springs that will coil bind as they get shorter.



interesting how you go straight to oil levels with out explaining how your theory affects springs...hmmm...what you seem to be explaining about oil levels...has more relievence to rebound damping...oil levels affect both rebound and comp damping...


Something I didn't make clear. Oil level affects the effective spring rate by changing the air gap above the oil. The air gap is effectively a progressive rate spring. By increasing the oil level, you can have a softer fork for small travel distances, to take out the small bumps, but still not bottom out under braking. Make the air gap to small and you will pop the fork seals...



It seems to me you do alot of trial and error....and I would say...you have alot of error...

There is alot of contradictions in what you have said...best you stop giving advice until you go and learn more about the subject of suspension tuning...okay :laugh:
Oh, I think I have managed ok so far.
Geoff