Race Tech pistons in stock cartridges

[FilthyLuka]

MOD WARNING: keep it on track, technical details only.

If you wan't to convince rob to go open source do it over PM

[Shaun]

MOD WARNING: keep it on track, technical details only.

If you wan't to convince rob to go open source do it over PM

You have a PM question to awnser about this

[Shaun]

Could you please awnser this TECHNICAL quetion Robert "Quote from you" Rob.


So prior to this last weekend we installed Race Tech compression pistons and their relatively new ''high frequency'' rebound pistons. These discard the inferior ''checkplate midvalve'' and employ a bending shim stack midvalve, copying Ohlins lead with their 25mm FGK cartridges.


Are Ohlin's the owners of Race Tech as well? or just happy for another to copy them?

[White trash]

MOD WARNING: keep it on track, technical details only.

If you wan't to convince rob to go open source do it over PM

What? Are you mental?

We can't ask non technical questions in this forum, is that what you're saying? You're dictating to people what they can and can't ask?

Seen it all now.......

Robert: Is there a website (Ohlins or otherwise) that thoroughly describes in laymans terms the actual physics of what a bending shim stack or a checkplate mid valve is doing during operation?

[Robert Taylor]

Quoted from Rob

I think you should divulge details of any forums that you may be involved in in your country so that we can continue such a debate on your patch? Or have you not got the intestinal fortitude to do so?

O thats write, you are GOD! Relax rob, Or do you not like to be challenged/guided/advised by a man with obviously has as much and more experience than you.

I am one of the KB members who really enjoy the extra input in the suspension thread from a freind, would you mind NOT tryng to push him away from this web site please, OR Have you invested over 100K into this site as well

There is a time for flippancy and there is a time where it is not so appropriate and that is the EXACT point I was trying to make. You were trying to achieve god knows what and so was someone else and for what reasons?
I dont have to divulge any of my own accumulated experience but have taken considerable time to do so, and will continue to do so as long as it is recieved in the spirit it is given.
I have often enjoyed the comments from JD but what I do strongly object to is he enjoys the luxury of occassional sniping from a position of anonymity. That is cowardly and hardly a level playing field.
I would therefore ask anyone reading this post if they would like me to continue offering help or short articles re what I have personally learnt with suspension systems????????????????????

[HDTboy]

As selfish as it sounds, I'd like to read as much as you can type on the subject Robert.

[Kickaha]

As selfish as it sounds, I'd like to read as much as you can type on the subject Robert.

As would I

[Robert Taylor]

What? Are you mental?

We can't ask non technical questions in this forum, is that what you're saying? You're dictating to people what they can and can't ask?

Seen it all now.......

Robert: Is there a website (Ohlins or otherwise) that thoroughly describes in laymans terms the actual physics of what a bending shim stack or a checkplate mid valve is doing during operation?

Not as such, but suffice to say the checkplate lifts relatively easily and dumps oil from one side of the piston to the other with relative ease, thereby dictating that most of the compression control is on the base valve. With the bending shim stack system it works exactly like a shim stack and places a greater degree of control at that part of the assembly. It will also modulate flow way way better than a check valve.
You cannot get too aggressive with it otherwise you will introduce cavitation, as correctly eluded to by JD racing. There are ways of ''tuning'' the checkplate system and we did fiddle with that for many years. But once we embraced the bending shim stack midvalve in the Ohlins FGK cartridges we went ahead in leaps and bounds. In fact I have an update mod for your forks that we tested with Shirriffs, Stroud and Bugden. Race Tech ( a seperate company to Ohlins ) now use this in road race and this is what we tested with Sam. This technology has been intermittently used in MX over the years but has only more recently been embraced in non works level road racing.
Jimmy, it was a pleasure to answer your question!

[White trash]

I would therefore ask anyone reading this post if they would like me to continue offering help or short articles re what I have personally learnt with suspension systems????????????????????

You know it big fella.

[Pumba]

As selfish as it sounds, I'd like to read as much as you can type on the subject Robert.

Add another vote for me, although I have read most of your posts and really struggle to grasp the concepts most of the time they are informative all the same.

[JD Racing]

What would be the definition of high frequency exactly? I've been doing this for a long time but have no idea whatsoever what high frequency refers to in this instance.

Checkplates can be made to work very well, with sufficient seat force they can help build cartridge pressure very rapidly, by restricting their lift you can limit the dumping of fluid, their rate of opening can also be modified with different spring rates. The general problem with checkplates is that in a traditional set up they dump too much fluid, this can be adressed by looking at all the elements in the system, of which it has many and tuning each element, its something that's far from dead.

Bending shim stacks can also be made to work well but to get the necessary seat force to stop them dumping fluid they need a fairly stiff stack which can lead to cavitation, build something that doesn't open the ports fast enough and you have too much damping at high speeds which makes the forks ride high in the stroke. With a bending shim stack system you have far less elements to tune which is very restrictive in a 20mm cartridge with a high pressure drop which makes them very susceptible to cavitation.

What is the viscosity index of the Ohlins oil, how does it compare with other oils in the ball wear test?
I'm not aware of "Ohlins use it in snowmobile shocks so it must be good" being an officially S.A.E recognised standard.
For an oil to be noticeably different within 1 lap they must have been of very different viscosities, what were the 2 oils tested and how do their viscosity indexes compare, what was the air temperature at the test?

[ArcherWC]

Keep em coming Robert

[et al]

Yes please keep it coming Robert - most of it is way over my head but I always enjoy reading what you have to say.

[Shaun]

There is a time for flippancy and there is a time where it is not so appropriate and that is the EXACT point I was trying to make. You were trying to achieve god knows what and so was someone else and for what reasons?
I dont have to divulge any of my own accumulated experience but have taken considerable time to do so, and will continue to do so as long as it is recieved in the spirit it is given.
I have often enjoyed the comments from JD but what I do strongly object to is he enjoys the luxury of occassional sniping from a position of anonymity. That is cowardly and hardly a level playing field.
I would therefore ask anyone reading this post if they would like me to continue offering help or short articles re what I have personally learnt with suspension systems????????????????????

Got my vote for sure

[Robert Taylor]

What would be the definition of high frequency exactly? I've been doing this for a long time but have no idea whatsoever what high frequency refers to in this instance.

Checkplates can be made to work very well, with sufficient seat force they can help build cartridge pressure very rapidly, by restricting their lift you can limit the dumping of fluid, their rate of opening can also be modified with different spring rates. The general problem with checkplates is that in a traditional set up they dump too much fluid, this can be adressed by looking at all the elements in the system, of which it has many and tuning each element, its something that's far from dead.

Bending shim stacks can also be made to work well but to get the necessary seat force to stop them dumping fluid they need a fairly stiff stack which can lead to cavitation, build something that doesn't open the ports fast enough and you have too much damping at high speeds which makes the forks ride high in the stroke. With a bending shim stack system you have far less elements to tune which is very restrictive in a 20mm cartridge with a high pressure drop which makes them very susceptible to cavitation.

What is the viscosity index of the Ohlins oil, how does it compare with other oils in the ball wear test?
I'm not aware of "Ohlins use it in snowmobile shocks so it must be good" being an officially S.A.E recognised standard.
For an oil to be noticeably different within 1 lap they must have been of very different viscosities, what were the 2 oils tested and how do their viscosity indexes compare, what was the air temperature at the test?

High frequency is the marketing term Race Tech use to describe them and I have mulled over why Paul Thede calls them that and should really ask him directly. The only reason I can give it is that as it oscillates ( at frequency ) between one stroke and the other it builds damping much more readily. At higher and higher frequencies it may have more ''stability'' As with a lot of Yankee PR the reason could be corny but I will take the trouble to find out.
I was accused today of being hard to pin down ( or to that effect ) and the post was removed. Getting hold of Paul Thede is VERY difficult even if you are the distributor, so dont hold your breath for the official answer. I think most very busy people are very hard to pin down and therefore prioritise which work they have to do first, same as any busy business.
Yes we played and played and played with checkplate allowable lift and spring rates etc using a big box of parts from the Ohlins racing department ( since thrown in the bin ) Also with oem and Traxxion we played with lift variables and thought we had something pretty good.
At least speaking from the perspective of 25mm I think we can all agree Ohlins have been around a long time and a couple of years back the cartridges were changed to bending shim stack midvalve type. I think its also very fair to say that Race Tech know a thing or two with what they are doing to their 20mm stuff, and will also be abundantly aware of the advantages of bending shim stacks.
Obviously we can agree that it is all about balancing the combination of the mid valve and the base valve.. I have spoken at length with Ohlins engineers about cavitation risk with what is effectively an emulsion type system, and of course you can achieve cavitation with an overly aggressive checkplate setup as well.
The Ohlins oil we are using has a flow rating of 14 centistrokes at 40 degrees celsius and is also a very slippery oil. If you pm me your e-mail address I can forward you the spec card. The tests were very scientific as we changed oil in the same day and conditions immediately. I will divulge the brand of the oil we had been using to that point, again if you pm me. Suffice to say the centistroke rating was almost identical.
I dont profess to be God with any of this stuff and never have done so. BUT I have always trod a consistent path and am prepared to continue to put in a massive amount of work to continue learning. And frankly I do derive pleasure out of helping anyone who asks, but conversely have little time for those who are loathing and scathing of the results of any effort.