Anyone seen a shop cut the base plate before?

[rideright]

I was helping a friend work on his suspension from a bike he bought used, 2002 CR250.

The interesting part was the base plate below the compression stack had been machined on the top surface (where the last shim sits) to a radius???

Someone also machined the outer diameter as well and installes a heavier top out spring???


I have seen this on radius type base washer on KTM65 SX fork pistons but never on a shock?

Has anyone seen this before?

The last few shims are so small and so thick that in all practical terms, they do not bend.

 

[DEANSFASTWAY]

Not on a shock but Ive seen fork base valves turned down to add more of a stack , but i always wondered why not just start with a wider pivot. Maybe on the shock they thought they would push less oil around the base washer which shouldnt be a factor anyway. Ive seen Factory Connection use a sort of tapered alloy spacer under a fork base valve stack (light stack). It kinda looks like it will cushion the light valving or limit its lift or bend . I think they did that to run light stack and still be durable. Was the shock you workedcon set up for woods or rocks with a real light stack with like almostr no mid stack ? Which way was the taper on the washer? Maybe they were kinda hunting for the same thing.

 

[terry hay]

Ohlins chamfer the top edge of the base plate with a lot of their shocks. It would take some serious shim deflection though before the base plate came into play.
Terry

 

[Jeremy Wilkey]

Factory Connection often does this... I have no idea why.. As pointed out allready, deflection values are not even close..

BR,
Jer

 

[rideright]

Thanks, Jer and Terry,

I had not seen that before, but I too agree the deflection is not even close on a rear shock base shim to bend to such a degree if at all and wonder what the thinking was that drove someone in that direction.

Yes this is done on '03 and '04 KTM 65SX forks, but the shims are so thin, they will bend to the radius.


Thinking of shim bending (deflection) and without posting any actual stacks. I have seen a major tread from the .1 thick separator shim to having two .1 thick shims to know in '03 and '04 many factories - OEM are running two .15 thick shims and in many of my calculations (still a work in progress) the low speed (straight stack) shims will not actually bend far enough to contact the high speed (taper) stack and therefore becomes more of a single stage valving setup ??????????????? This seems to hold especially true on YZ250 rear shocks??

The separator shims also seem to be growing in diameter each year??


I have not read many of the old thread, but wondering how many there are on the subject of just the separator shim thickness and diameters??

 

[russ17]

Originally posted by rideright
OEM are running two .15 thick shims and in many of my calculations (still a work in progress) the low speed (straight stack) shims will not actually bend far enough to contact the high speed (taper) stack and therefore becomes more of a single stage valving setup ??????????????? This seems to hold especially true on YZ250 rear shocks??

Rideright,
Are you sure the YZ250 is running 2-.15 crossovers as I have not seen this on the 03 04 my calculations are they are running .1s

 

[rideright]

Russ17, Sorry you are Right. Guess this means you can not believe everything you read on the net, LOL

I had a couple of YZ's in the shop at the time. '04 YZ and KX use 34x.1 and 30x.1 separator shims. It is the CR and CRF line that use 37x.15 and a 30x.15 separator shims.

My point being to create conversation on peoples opinions on separator shims.

Mine being .3mm seems like a very long distance for the upper stack to deflect and touch the bottom stack to cause the lowe stack to deflect and therefore, even though you may see two stacks, anything with a large separation between the stacks is acting like a single stage stack.

Of course the total thickness and make-up of the top stack will determine its total deflection, I'm just speaking in generality.

 

[russ17]

rideright
I did understand where you are going with this, I think you bring up a valid point here. IMO I think it would depend on the stack above,as you stated, but also, as to what you use at the beginning of the high speed also.
I was kinda questioning my measurements, for a second is all.


RUSS

 

[rideright]

Yes, this is a critical feature of a stack-up. there must be a bunch of opinions out there?

 

[marcusgunby]

Dont forget to some extent the cross overs will try to bend with the ls stack and push on the high speed stack-this will only contibute a very small amount of the damping as deflections will be very small.

 

[russ17]

Marcus,
I would say yes , but I think it would depend on the diameter of the CO. The larger the diameter the more the LS is effected by the HS.
Any thoughts to this.

RUSS

 

[marcusgunby]

yes russ, it would be interesting how much this will add to the total damping-i think the cross over diameter and sizes must play a small part in the total amount of LS and HS, the shim program of kevins seems to say cross over gaps are important but not the diameter of the c/o.This is going to be changed in a upgrade apparantly.I try to think of stacks separatly, think of the ls stack , if we made the last few shims small we have less ls overall, this must be true if the last few shims become the crossovers before the hs stack.

 

[DEANSFASTWAY]

Diameter definitely plays a role , Isnt there a rule of that the crossover must always be wider than the clamping shim? i think someone once told me that. I could be wrong though. Ive got an interesting project on the bench right noe its a brand new aftermarket ZPS quad shock that is real harsh and upon taking it apart I think its kind of hydro locking . The Comp stack is so tight against the base plate and the clamp/pivot is so wide that I cant see how it could really flow enough to really absorb anything . The rider says the shock is so harsh that he wants it redone but doesnt want to send back to original place. Ill put up some specs in a few .You might laugh .

 

[marcusgunby]

Dean that isnt a hard and fast rule but it makes sence to me.The 04 RM has a 8.5mm clamp shim but a 8mm cross over on the forks passive side, so the hs stack has a 8.5 mm clamp and the ls stack uses a 8mm clamp-only time ive seen it.

 

[russ17]

I think the golden rule you talk of' is the as long as the CO is the same size diameter of the clamp. the LS shims will bend by the equal thinkness of the CO to contact the high speed. Example Clamp 22mm Co= 22.15
so it will take the LS shims to bend .15 to contact the HS

Russ