Fork midvalve - shim stack or check plate?

[Yankee Doodle Dandy]

Up until recently sport bike forks used a check plate and a spring /wave washers for a midvalve set up. Dirt bike forks would use a shim stack and after market tuners such as Race Tech would sell kits to change them over to a spring w/ check plate configuration.

The 06 and up GSX-R forks use a shim stack w/ a bleed hole. K-Tech uses a shim stack.

Ohlins uses a check plate w/ wave washers in their 20mm piston kits and a check plate with a spring in their 25mm stuff. They even offer (3) different rate springs.

There is a US Ohlins dealer that offers his own valving in the Ohlins stuff and has been replacing the check plate set up with a shim set up.

Which is a better set up for track use?

[vifferman]

Eggs Zachary. But I prefer the minestrone.

[Pussy]

Bending shim stack mid-valve for the win!
Stock Showa forks on the 06 onwards GSX-R 600 and 750 have the feature.
I have a set of FGK 132 cartridges in my 750 with the mid-valve. Brake dive resistance is excellent. The forks can be run with slightly more rider sag, and still be kept up in their stroke.
Robert Taylor from this site will be able to give you a good explanation of it

[Robert Taylor]

Up until recently sport bike forks used a check plate and a spring /wave washers for a midvalve set up. Dirt bike forks would use a shim stack and after market tuners such as Race Tech would sell kits to change them over to a spring w/ check plate configuration.

The 06 and up GSX-R forks use a shim stack w/ a bleed hole. K-Tech uses a shim stack.

Ohlins uses a check plate w/ wave washers in their 20mm piston kits and a check plate with a spring in their 25mm stuff. They even offer (3) different rate springs.

There is a US Ohlins dealer that offers his own valving in the Ohlins stuff and has been replacing the check plate set up with a shim set up.

Which is a better set up for track use?


25mm, Ohlins with shim stack. Their 20mm stuff is old hat and I have been at pains to get them to change it.
20mm. Race Tech high frequency rebound pistons, the rebound ports are a near identical copy of Ohlins but with a shim stack midvalve.
Much more instant damping response and braking pitch control, absolutely no question.

[Yankee Doodle Dandy]

With the Ohlins 25mm stuff are you modifying the piston so you can use a shim stack or does Ohlins make a rebound piston for use with shims?

[Pussy]

With the Ohlins 25mm stuff are you modifying the piston so you can use a shim stack or does Ohlins make a rebound piston for use with shims?

The rebound pistons have been coming as midvalve ones for a while. At least three years, to my knowledge.
This is, of course, in the 25mm cartridge kits

[Yankee Doodle Dandy]

All the ones I have been messing with have had the check plate and spring configuration.

[Robert Taylor]

All the ones I have been messing with have had the check plate and spring configuration.

The pistons we use are different to current production as delivered. I dont wish to elaborate further on this public forum as its commercially sensitive and there are parasites in our industry that will be reading this.

[Yankee Doodle Dandy]

I poked around online a little bit and it does look like Ohlins went from the spring & checkplate to a mid valve arrangement.

However, I do see Ohlins still uses the spring & checkplate on their current Superbike fork (FGR 800) and their new 30mm cartridges for the R1 use a spring & check plate.

[Pussy]

There must be HEAPS of Ohlins dealers on your continent who will have the info you're looking for. They've got access to the gen on your side, if they are authorised

[Yankee Doodle Dandy]

There must be HEAPS of Ohlins dealers on your continent who will have the info you're looking for. They've got access to the gen on your side, if they are authorised
Help in the US?

You must have never been here.

[Pussy]

Help in the US?

You must have never been here.

You're right.... I haven't.
Surely your Ohlins importer/technical staff will have the gen?

[Yankee Doodle Dandy]

Ohlins USA is useless to me.

Unless you are a factory team or satellite team then you are SOL.

95% of the people selling Ohlins in the US are just shops that change parts. For street based stuff the majority of suspension shops here deal with Penske as they are easier to work with.

[Shaun]

Ohlins USA is useless to me.

Unless you are a factory team or satellite team then you are SOL.

95% of the people selling Ohlins in the US are just shops that change parts. For street based stuff the majority of suspension shops here deal with Penske as they are easier to work with.



I have been trying to tell Robert for years now to get his arse over to the USA

[Yankee Doodle Dandy]

I don't know why I typed for street based stuff, I must have been half asleep. Penske's sales are not limited to street stuff as they have a huge presence on the track also.

Most of the real suspension shops over here deal with Penske as they are easier to work with. They provide much better support and are easier to get custom stuff done.

Off the top of my head, there are only a couple of independent suspension tuners that really work with the Ohlins stuff and one of them is a former Swede that worked for Ohlins.

[Shaun]

On our side of the world it is Ohlin's that is the main shock here, with the best support anywhere in the world!

What has inspired you to start posting on a New Zealand bike web site?

[Yankee Doodle Dandy]

A post with a lot of info came up in a google search.

It seems like people over here are more interested in talking about stuff that matters regarding suspension work.

If you were to ask this same question on a US forum it would go like this - first people would tell you that they know nothing about suspension so you should just send the forks out to either X, Y, or Z. Then the rest of it turns into a 35 page argument about how X & Z suck and that Y is the greatest thing since sliced bread.

[SARGE]

welcome to the site YDD.. glad to have another Yank on board



A post with a lot of info came up in a google search.

It seems like people over here are more interested in talking about stuff that matters regarding suspension work.

If you were to ask this same question on a US forum it would go like this - first people would tell you that they know nothing about suspension so you should just send the forks out to either X, Y, or Z. Then the rest of it turns into a 35 page argument about how X & Z suck and that Y is the greatest thing since sliced bread.



same here.. stick around

[Shaun]

A post with a lot of info came up in a google search.

It seems like people over here are more interested in talking about stuff that matters regarding suspension work.

If you were to ask this same question on a US forum it would go like this - first people would tell you that they know nothing about suspension so you should just send the forks out to either X, Y, or Z. Then the rest of it turns into a 35 page argument about how X & Z suck and that Y is the greatest thing since sliced bread.


Fair enough indeed! Robert is very good with what he does, as he really loves the game, to me, he is like a racer, wanting to find out how to be better quicker and safer, he helped me to win many many races

[Yankee Doodle Dandy]

I see Ohlins uses the older check plate configuration on their now 30mm R1 pistons.

[Pussy]

I see Ohlins uses the older check plate configuration on their now 30mm R1 pistons.

Don't forget that one leg does compression and one rebound in the '09 R1

[Yankee Doodle Dandy]

Don't forget that one leg does compression and one rebound in the '09 R1
Yep and they both have check plates.

[Robert Taylor]

Yep and they both have check plates.

Yes but there is damping only in one direction for each piston so there is no longer a midvalve in the accepted sense.

[Yankee Doodle Dandy]

Wouldn't you still want a mid valve stack to control initial dive?

[FROSTY]

Hmm so no Ohlins independant person in the whole of the USA ??
I wonder how RT would sound with an american accent?

[Robert Taylor]

Wouldn't you still want a mid valve stack to control initial dive?

No, because the compression stack is right where the midvalve used to be.

[Yankee Doodle Dandy]

Hmm so no Ohlins independant person in the whole of the USA ??
I wonder how RT would sound with an american accent?
There are only a few that I know of.

I could count them on one hand and still have plenty of fingers left to pick my nose.

[Yankee Doodle Dandy]

No, because the compression stack is right where the midvalve used to be.
So maybe I have things wrong.

The way I understand it is that the compression stack requires x amount of pressure for the shims to start to bend.

The mid valve would require much less than x amount of pressure for its shims to start to bend. This provides damping at low shaft speeds to prevent any harsh feel and provide control.

I am not trying to argue, just understand. When you look at the individual stack/valve/parts combination they look like a traditional arrangement pre-mid valve. If the mid valve assembly works great in a traditional fork what is the dynamic that changes when things are set up separately?

[Pussy]

There is NO base piston in the '09 R1 forks
So the piston/shim stack on the rod of the compression side is ONLY looking after compression... and does it right away

[Yankee Doodle Dandy]

I thought about it some and think I understand now.

Since you have removed the rebound circuit from that fork leg the pressure builds up faster as there is no low speed rebound circuit for it to bleed off through which allows the compression stack to react faster therefore eliminating the need for the mid valve.

Taking it one step further, the elimination of the other circuits (ie - mid valve and low speed rebound) is why they say the BPF tend to ride higher in the stroke.

[Robert Taylor]

I thought about it some and think I understand now.

Since you have removed the rebound circuit from that fork leg the pressure builds up faster as there is no low speed rebound circuit for it to bleed off through which allows the compression stack to react faster therefore eliminating the need for the mid valve.

Taking it one step further, the elimination of the other circuits (ie - mid valve and low speed rebound) is why they say the BPF tend to ride higher in the stroke.

Send me a pm and I will clarify