Damper rod forks, emulators, intminators and progressive springs

[Robert Taylor]

A interesting note re the RaceTech link above and the comment re Hagon. You may have been surprised at what could have been supplied for similar coin to your Hagons. I was.

As a recent customer of Roberts fork springs I join the CKT congregation as a convert of his local experience. I'd picked out the spring rate based on the on-line calculator and he recommended going down one (lighter). Plus he could supply Ohlins units cheaper (hey - everyone loves gold ).

Turns out the spring rate is perfect and if I'd gone by the on-line calculator in the above link my front end ride would be less compliant.


I did discover one negative to improving the front end - the short comings of the rear are now extremely apparent Nothing a email could not fit!

The sexy scandinavian suspender left Stockholm yesterday!

[White trash]

So a progressive spring would not be an improvement on the stock spring for an old bandit? I ask this as anything more expensive couldn't be justified with my budget/riding style. (and especially to the boss)

Can you not read man? I promise you, altering the oil level (''SECONDARY TRAPPED AIR SPRING COMPRESSION RATIO'')will be far cheaper than buying a set of progressive springs.

[Robert Taylor]

So a progressive spring would not be an improvement on the stock spring for an old bandit? I ask this as anything more expensive couldn't be justified with my budget/riding style. (and especially to the boss)

Well yes it likely would be an improvement but in all such scenarios linear wind springs in a rate appropriate for you work a lot better, especially at absorbing bumps. Plus the progressivity can be easily fine tuned by adjusting the oil level. Many progressive springs can be too aggressive in end rate and that can require a significant lowering of oil level to reduce last third of stroke ''secondary air spring compression ratio''. A much lower oil level means that upper bushing wear will be accelerated as lubrication is by dispersal and vapour only, the oil has further to travel.
When you find that the start rate of that progressive spring is initially too light ( causing the forks to initially feel sloppy and blow through their stroke ) but then ramps up too aggressively later in the stroke ( causing terrible compliance over abrupt bumps ) then you will be stuck with them but not struck them.
As I brutally said at the start of this thread they are a 70s solution and thats 40 odd years or nearly half a century ago! And at least 50% of the problem is very poor hydraulic control. Oversimplistically springs are primarily about ''position'', damping is about controlling rate of change of position.

[Robert Taylor]

Not wanting to get off topic, but having only seen them in pics (an article you did for BRM I think) I was surprised that the ports were so small on such a big piston. I mean I can see on a small piston you need complex machining to increase the size, but on those big mothers there appeared room to at least improve the issue with a bigger drill bit.

But why? Does Paul pay them a retainer to cripple themselves so he still has a market?
Its a conspiracy?

God only knows. Maybe in part its about slowing down the damping ( or rate of change of position ) so that when very well fed people hop on such bikes they dont have a tendency to blow through their stroke and bottom out. And then approaching the manufacturer demanding warranty. This is also another reason that on conventional ( and I think better ) cartridges have longish hydraulic bottoming out cones

[Robert Taylor]

Interesting stuff!

If I've understood it correctly (reading it involved a lot of googling part names so I'm not sure on this point) the first/most important thing to sort is the spring rates? Are sag checks a decent indicator of how suitable the current spring rates are?

And is rear suspension a different story with regards to the progressive spring issue, as most linkages cause both progressive spring and damping rates right?

edit: also, any more news/info on semi/active suspension systems?

Thanks. Yes spring rates first and foremost but sometimes the arrangement of the damping can allow a slight change of spring rate, also in the racing world the choice of tyre construction can have a major affect on spring rate choice, preload and damping.
Sag checks and the ratio between rider sag and resultant free sag is an indicator but the numbers are not gospel. The preload required on the spring is also an indicator. You know what, when we go testing with top riders we have a big box of springs and we change and test, change and test. We are looking for the best lap times and also monitor tye temperature. We are also of course looking for the slowest possible tyre degradation and some circuits are a real challenge, anyone that says different is full of BS. We may end up with numbers that look ''nuts'' but if it works it works.
Throw in rear shock internal top out springs in various rates and lengths and the neccessity to balance the selection of those against main spring selection and preload. Sometimes we have too many parts in the box!
We generally only use progressive spings in the rear ends of twin shock bikes because there is very little rising rate effect. Even then the springs we use ( Ohlins ) have their progression so late its at about the last 10 or 20% of travel, affected by such variables as available suspension stroke.
Rear rising rate links are there only to accelerate the shock shaft velocity deeper into its stroke. The faster you move that shaft the more it damps. Again its there very much for keeping the bike ''off the bottom'' when ridden by a very well fed person with his wife and worldly goods. ''All things to all men" Crudely so.

[bogan]

Thanks. Yes spring rates first and foremost but sometimes the arrangement of the damping can allow a slight change of spring rate, also in the racing world the choice of tyre construction can have a major affect on spring rate choice, preload and damping.
Sag checks and the ratio between rider sag and resultant free sag is an indicator but the numbers are not gospel. The preload required on the spring is also an indicator.

Probably getting about time for me to recheck my sag again, from memory the recommendation was 25-30mm with rider, and about 5mm without for both front and rear was judged good for the average rider on the road, sound about right?

Rear rising rate links are there only to accelerate the shock shaft velocity deeper into its stroke. The faster you move that shaft the more it damps. Again its there very much for keeping the bike ''off the bottom'' when ridden by a very well fed person with his wife and worldly goods. ''All things to all men" Crudely so.

Hmmm, so if one were to retrofit a rising rate linkage to his bike (non linked standard) this would be a silly thing to do? I always thought rising rate allowed it to be plusher for small bumps, but keep it from bottoming and kicking like a mule on the bigger ones.

[Robert Taylor]

Probably getting about time for me to recheck my sag again, from memory the recommendation was 25-30mm with rider, and about 5mm without for both front and rear was judged good for the average rider on the road, sound about right?



Hmmm, so if one were to retrofit a rising rate linkage to his bike (non linked standard) this would be a silly thing to do? I always thought rising rate allowed it to be plusher for small bumps, but keep it from bottoming and kicking like a mule on the bigger ones.

E-mail to me at robert@crownkiwi.co.nz and Ill forward you a setup manual that explains all of the sag settings for various applications

A certain amount of rising rate is a positive and can be your friend on bumpy roads with ''g out'' hollows / upramps. So yes plush initially but not so free it blows through its stroke and ''hits'' the rising rate curve. But enough rising rate to ''catch'' sudden and potentially full stroke movements initiated by g out.
Personally I think also that ''digressive damping curves'' have their limitations and often we valve with more ''slope'' to ''keep away'' from the link.

[SWERVE]

Keep it coming Robert........fascinating stuff.

[Robert Taylor]

In Pro Twins racing we have installed and developed the lions share of Race Tech Emulators into SV650s, happily married to Traxxion Dynamics damper rods and Ohlins linear wind fork springs.
The fork springs we use are significantly shorter than stock and also all of the regular aftermarket options. This must be consistent with having enough stroke integrity left so that the springs dont coil bind at full closed position. The benefits of running much shorter springs is that there are a lot less coils, that means less rubbing against the inner fork walls, that support them. That means less friction and also less chards of metal being slowly scraped off the inner tube walls, in turn contaminating the oil and embedding in the fork glide bushings. Also less weight given that much of the space is then taken up instead by a long thin wall alloy preload spacer tube. The oil capacity is also greater given that there is less spring to displace oil. The springs we use are Ohlins Superbike springs, these are finished very nicely and accurately on their ends and have a much higher finish polish, in turn reducing friction even more. Looking at a lot of brands of aftermarket fork springs the finish and rough end conditions leaves a lot to be desired. There are always good reasons why some products are cheaper
Fork seals used are genuine as they are the highest quality but most importantly the lowest drag. We see red when we come across those red HIGH DRAG multilip seals and refuse point blank to fit them. Why would you want to make your fork action sticky?
The RACE TECH EMULATORS themselves are not just a straight drop in, contrary to the marketing philosophy of self instal. We change the bypass hole size which is rather easy to do with brass as its solderable. We also change the rate of the main poppett spring and its preload.
Its fair to say that we have a very very well developed spec and both Geoff Booth and Johny Small used this very developed spec to very good effect over the last 2 years to win their respective NZ Pro Twins championships.
But we are always game to try different things and Ricor Intiminators captured our attention so we acquired a set specifically spec'd for racing SV650s to test. We didnt wish to pre-guess the settings so we initially installed as per the instructions.
Its fair to say that with most American made products its easy to get euphoric about all the loud hype that these companies are so predisposed to doing to peddle their products. We have seen this time and time again over the decades with American product and I think English reserve teaches you to not be intimidated by it but to also keep an open mind. Those US reality shows such as ''Extreme Makeover'' really typify about how loud and over the top our American cousins all too often are and I make no apology for being put off by it.
Anyway we installed a set and ( as you do ) we initially pushed on them to see how the feel was compared to the well developed RACE TECH EMULATOR forks. Frankly they felt excessively firm but the most noticable thing was that there was a very audible click at even a very moderate push. Concurrent with that we could feel a little cavitation, a bad sign. This we initially thought was the ''Inertia valve'' but after looking at it again and thinking it through the reason was obvious, the Intiminator was momentarily lifting off its seat and then reseating. This was further exacerbated by an overaggressive ''shim stack'' spec.
As with Emulators the only thing that holds them in place is a degree of clamping pressure of the main fork spring sitting on it, its essentially sandwiched inbetween the top of the damper rod and the bottom of the main fork spring. So by implication Emulators ( genuine and low quality pirate rip offs ) will also momentarily lift off their seats, even moreso if the spring rate and preload is weak and the damping setting aggressively strong. Only they dont ( seemingly ) make any noise in doing so.
Anyway we rang the manuafcturer and said hey the setting is too aggressive and concurred on a lighter''shim stack''. We duly installed that and the clicking was less pronounced but nonetheless it was still there, along with cavitation. But we took it to Manfield and as we had two sets of forks, best Race Tech setup / Intiminator setup we were able to back to back on the day in rotation very quickly and totally plausibly. The end result was the Intiminator bike was not able to lap as fast and the rider complained that feel / feedback was inferior to the well sorted Race Tech Emulator equipped forks.
Here is a list of comments of Intiminators, from lengthy analysis and our own very methodical testing
1)) The bottoms of the Intiminators are a flat face so they just sit on the tops of the damper rods. There are no hat type steps to engage / centralise into the top of the damper rod as with a Race Tech Emulator. If as is all too often the case the damper rod is cocked to one side and is not perpendicular to the centreline of the fork then its not going to sit properly and ''assists'' in abutting the spring more firmly against one side of the inner fork tube wall. FRICTION, FRICTION, FRICTION.
2) To its credit the Intiminator has its own piston ring, that will help to stop it rubbing against the inner fork tube wall and will catch some of the UNCONTROLLED BLEED that passes the piston ring in the top hat of the damper rod. But it will also exacerbate the lifting off of the seat. To not put too fine a point on it this is bandaid engineering
3) Inertia valve. It sounds great in theory and its very hyped up but it certainly didnt deliver the goods in our extreme testing environment. And to me its a very poor substitute for a sophisticated modualting shim stack that the Intiminator clearly lacks
4)The shim stack. Its not really a shim stack and the manufacturer really dropped the ball over what was possible. Lack of proper well modulated flow contributes to the cavitation we felt, as well as the clicking we heard
5) Unlike Race Tech there is no instruction to remove the damper rods and to oversize the existing damping holes in the bottoms of the damper rods to remove them having a possible influence as a flow restriction. There are a number of models of bike out there with very tiny damping holes. These create a very real flow restriction on harsh bumps. Intiminator or no Intiminator, Emulator or no Emulator.
6) They recommend going to thin oil and in part they get away with it and its just as well given the very real cavitation thats going on. This in part but not wholly will compensate for not processing to a bigger size those damping holes and the two way flow restriction helps to deliver a modicum of rebound damping control, but very crudely and very incorrectly. By product, cavitation. Those that have studied the flow path circuits of rebound ''control'' in damper rod forks will understand exactly what I am driving at. Intiminators do not modulate rebound damping ( nor does an Emulator nor can they both ) Intiminators crudely restrict rebound flow.

On the face of it these are marketed for the consumer expectation of ''drop dead easy self instal'' when in reality its an extreme band aid. Sure as an average road going rider you will notice an improvement but ( cynically ) the flow restriction holds the forks up in their stroke much moreso, keeping the suspension from too readily blowing through its stroke and precompressing the springs so much that the suspension will get harsher. And if you hit something really abrupt the Intiminator will momentarily unseat off the top of the unsquare damper rod allowing a mass of thinner oil to bypass. Cavitation may also ''assist'' in delivering bump compliance!!!! Long term users of Intiminators will on stripdown witness ''activity on the bottom face of the Intiminator and top of the damper rod. indeed and in fairness we also evidence a degree of that with Emualtors, especially the nasty pirate ones that have a veneer anodising and are rapidly wearing through that to their soft alloy underbelly. Photographic evidence will follow in a future post.

Consumers are in part to blame because everyone wants an affordable product that will deliver a miracle cure and doesnt require a rocket scientist to instal and optimise. But I make no apology in re-emphasising that this is bandaid engineering to a very high degree. But then to a lesser degree so is the Emulator.
If you dynoed a Intiminator kitted fork the amount of hysteris that you would evidence would be huge. We havent dynoed such a fork but we have certainly felt it.

NEXT, The ''perfect'' Emulator and how it would work.

[johan]

Great thread, but it needs more pictures!
cheers

[Pussy]

Great thread, but it needs more pictures!
cheers

An example of aftermarket valving......

[Owl]

An example of aftermarket valving......

Quality plus

My CKT stickers fell off.

[SWERVE]

As you say Robert a "band aid" and in most cases on a "broken leg" makes you fell better initially but still hurts like hell at bedtime
Great posts....... having to print them so i can re-read and take notes.....
keep it coming

[Robert Taylor]

Illustrated is the folly of soft anodised alloy as a material choice for pirate copies of Race Tech emulators. Text to explain why will follow in a successive post

[Robert Taylor]

Illustrated is the folly of soft anodised alloy as a material choice for pirate copies of Race Tech emulators. Text to explain why will follow in a successive post

Up to a couple of years ago I expressed concerns about the longevity of cheap pirate copies made of alloy. The copies pictured have been in service for about 1 year and we have removed them to make the things actually work properly!
Heres a reminder of some of the main issues with damper rod forks:

1) Poor damper rod alignment meaning that the seating surface is not square / perpendicular to the centreline of the fork

2) The ''end conditions'' of many oem and budget priced fork springs are often unsquare and poorly finished with sharp edges that will ''bite'' into softer metals in short order

3) The reality that Emulators and Intiminators are actually not fully seated under all and varying deflection velocities. They hammer, bump and grind off and on the seating surfaces

Therefore any untruth in seating, rough spring end conditions matched to soft material choices is a recipe for disaster. In the images I posted you can see on their top surfaces where the spring ends have been digging in, on the opposite surface ( poorly focused image ) you can see advanced wear through the ''hard" ( ? )anodising where its through to the parent metal. Further use will be accompanied by rapidly accelerated wear, oil contamination and particles being embedded in the glide bushings. Not nice.

Id question if the anodising is little better than decorative grade anodising as it certainly doesnt imbue confidence that its true 1st world quality hard anodising. A test with a file on the exposed parent alloy also appears to indicate that the grade of aluminium alloy used is a basic grade with very few alloying elements to add hardness.

Another issue we found is that the one way check shims installed were in fact 2mm smaller in internal diameter than they should have been, and also 2mm smaller in id than the main high speed through flow port when the poppett valve opens. So it shadows the edge flow of the port ( in itself creating cavitation ) and adds unneccessary high speed flow restriction. In the attached topside image we have already corrected that issue.

Another practical issue is that the high speed poppett itself is also made of alloy. In genuine Race Tech emulators the parent metal is brass, itself a relatively low cost and easily machined material. Its more resistant to wear but also as the material is brass its easily solderable. In the poppetts are drilled one or two bypass holes for low speed compression flow. That is a tuning element we use quite often, tuning the size of that bypass hole. With a brass poppett its easy to solder up the existing hole and drilling another one opposite to it if you wish to downsize the hole. Try soldering aluminium!

You only get what you pay for, caveat emptor.

SO WHAT WOULD BE A PERFECT EMULATOR?

To my mind it would be a housing that threads into a damper rod that sits perfectly square in the forks with good sealing. No low cost bandaids here. Within the centre of that housing would sit a high flow piston the same as is used in many cartridge forks, with a proper modulating shim stack ( much more precise at initial flow control than a spring loaded poppett ) And in the centre of that housing would be an adjustable bypass needle for tuning low speed damping. Is it possible, you betcha. But like all interpretaions of Emulators it only has control over compression damping. Rebound flow is a more difficult issue, excepting that with careful attention to clearances and alignment you can produce a very decent result. Fixed orifice damping is more '' in tune'' with whats needed with a rebound force curve.