road race suspension

[semi old guy]

jer what ever became of your testing with the road racer. you mentioned the high shaft speeds you measured under braking. do you have to increase the high speed compression to reduce dive?

 

[Jeremy Wilkey]

SOG,
We had quite a season actualy. Thisngs went very well. Our biggest problem ended up not being able to adjust ride ht or preload externaly. We did a fine job of making the suspension work well but had a hard time making quick chassis alterations that the high line penske, ohlins, wp offer.

Right now Muddy is regrouping and making plans for his team next year but hopefully we will win the AU titles.

As for the speed issues we found that the best solution was not in the highspeed compression but actualy the midspeed provided the best answer. By making the fork stiffer here we had a postive effect on the high speed but did not actually pay such a negative price as as adding true high speed damping.

I beilve if you looked at in a graphical form the midsection would be swelled..

Regars,
Jer

 

[svi]

I have been reading this article on the web about GSXR 1000 forks, are they really that bad ?http://venus.13x.com/roadracingworld/issues/mar01/susp.htm

 

[Jeremy Wilkey]

Max had a intresting take on the suspension. I agree and disagree with his assement. Overall I will agree that stock pistons are questionable, but he has a bigger port is better physiosohy that squews his veiws on midspeed vavling in road race forks. (maybe I'm wrong here we are not asking him about this speciifcaly.) I've never heard anything but good things about his RR bikes so... I'll just say our approach has been very diffrent from his, and honestly far more limited in scope.

To further my ealier post I think I can now say...Muddy has just signed on to be the offical Racing serivce for Ohlins, and has allso inked a deal with Ford. MXT Fatory rqcing of AU team will be much bigger next year, and hence our reasearch will continue..

Thanks for bring about that Cool Post! Have you ridden the bikes in question?

Jer

 

[svi]

I borrowed a friends for an hour but I was that busy scaring myself with the awesome power I didn't bother thinking about the suspension. Considering I ride a TL1000s which I admit does not have a brilliant shock, but not that bad I can be bothered to do anything about it, my judgement would probably not be the best.

 

[svi]

Jer,
With forks like these using a checkplate, would you describe midspeed as the transition from lowspeed bleed and the initial opening of the shim stack, the low speed bleed adjustment in combination with the shim stacks properties determining the resultant damping force?
With the maximum shaft speeds encountered by a street bike being perhaps a tenth of those of a motocross bike do you see any place for midvalves in street bikes?

 

[Jeremy Wilkey]

SVI,

A road race fork travels faster than 1/10 the speed of MX or at least as far as I can tell. Speciifcally we set up our forks with a midvalve. A road race fork has some of it's highest speeds when braking and the fork is in what would be a mid-speed compression. We've found we can massively improve traction and feel (tire wear) by running less compression on the base-valve and runing a low float but soft midvalve set-up.

Regards,
Jer

 

[svi]

Last year talking to a data engineer at a road race meeting he gave me a printout of some old data to show the power and capabilities of the system he was using, fork shaft speeds under braking generally reached a maximum of 0.6m/s, a figure John Bradley says WP use as a maximum in his book. I remember seeing a post here in the past by Shocknut with velocities for mx forks of up to 10m/s.

 

[Jeremy Wilkey]

The .6m/s seemes very low. I'll get with Muddy and see if he has any of his data. In reference to your shocknut info...Rob Mann has been saying he has Data aquistion for offroad bikes, but I don't think much has ever come of it. Evryone who tries seems to a run out of money or still be working on something durable enough. Even the almighty RT has had troubles bring there system to the market on time.. I can't say with facts one way or the other at this moment however .6m/s is parked! So I guess We should both check our numbers..

 

[semi old guy]

it seems like acceleration should be more important than speed

 

[svi]

S.O.G.
If I select points where there is a rapid change in velocity and work out the acceleration it gives figures in excess of 10m/s/s but they are generally only 0.02./ 0.03. s in duration. How or what effects would this have ?

 

[semi old guy]

i would think that the feel of harshness is related to acceleration or the lack there of. in other words that few hundreths of a second may be important

 

[svi]

With no significant gas pressure would the forks be able to generate the damping force in such a short period of time to cause harshness? Or would that have more to do with the amount of stroke used were looking at 5-10mm?

 

[semi old guy]

are you saying the forks actually push a void into the oil at the beginning of the stroke?

 

[svi]

No I'm not suggesting that. I was questioning the rate of reaction to such a short input if you had a 12mm shaft and 10 mm travel there would be a tiny amount of oil displaced by the shaft. In such a short period would this be sufficient to cause harshness? The rate of reaction being related to the pressure in the system. :think ( I'm not sure what I'm on about but bear with me I'm only Irish.)
Would you valve the system to suit peak acceleration or peak velocity?

 

[Jeremy Wilkey]

SVI,
Well I finnally have had a chance to get back to my Forum.. I spoke with Muddy (our AU importer and now the offical Ohlins Road race racing service) and your info is very cooorect in terms of operational speeds. The intresting part is the peak for MX is only slighlty higher, so this helps exsplain the success we've had with midvalves in RR.. I was really conceptually struggling till I learned that most of the speed issues talked about here are flat wrong.. (in terms of absolute speed)

I only wsh someone would actually bring to market a DATA system that can work, and last..

Thanks for the good string..

Also I do belive that is a non-twin tube design at the top of the stroke the forks do caviatae due to lack of internal pressure. The problem is not so much compression on the first hit, (the piston can't push the fluid in a high speed if it's full as that would be stiffer yet. ) The problem actually starts as the forks return to full exstension under low pressure and don't completly refill.


Regards,
Jer

 

[robmann]

The data equipment is still being used but we have been in a transition to Windows based program and this has been somewhat of a struggle we hope to have this worked out by the end of September. We will be doing some more testing Sept 8 with it on the 02 KTM125.

They are also working on a smaller unit for me. The one complaint that I have from the riders is the unit is heavy, mounted on the front number plate.