Rebound Dampning changing

[Jasle]

I have an ohlins shock on a PeeWee.  The problem is that the rebound and compression dampning seem to have gotten a lot softer.  The N2 pressure is 55psi on the remote resivoir.  The shock is non adjustable.  Recently had the seal head replaced.  Don't notice any fluid leaking from the seals. 

 

Is this just the oil breaking down.  It only has about 5 hours on it since the seal head was replaced and oil and N2 recharge.

 

Thanks

Jason

 

[Jasle]

well after a ride today all rebound and dampning action is gone. No sign whatso ever of oil leakage and still good pressure on the bladder.
Any ideas before I ship it off to the suspension guy?

 

[shaggy829]

sounds like your low on pressure , it may not have been filled properly at the last service .also are you sure the gas pressure is not 155psi. 55 seems to be on the low side . at 55 psi the shock is shure to cavitate and would loose damping . most ohlins shocks use piston resivior's which require higher pressure . small bladder shocks run about 140-150 and piston resi shocks go about 170-180 .
shaggy

 

[Jasle]

good info! I'll have somone bump it up to 150 tomorrow and see how it goes. But if it has leaked out that means pretty much I have a leak in the bladder right? or the schrader valve I guess???

Thanks. I didn't realize that 55 was low.

 

[jossbuk]

How did you measure the pressure. There is vary little volume in a shcok. You could of lost 100 PSI when using a normal pressure gauge...

 

[Jasle]

I did use a normal pressure gauge. Not until after we had the problem though. the second time I measured it was 25psi. I talked to the Cobra guy and they said 125 is where it should be. I borrowed a shock and after 2 moto's the borrowed shock had gone south too. Absoloutley no rebound or compression dampning. I'm off to the suspension shop later today.
Any idea how I could blow 2 shocks in the same week? The kid is riding harder but this just sucks. State Finals were this weekend. He did surprisingly well with the crap shock.
And I have the Cobra Designed shock. The ohlins was released a little later than when out bike was made. My mistake.

 

[KTM-Lew]

These don't have a linkage, do they?....I'm thinking if the bottom mount isn't swiveling or the heim joint is bound up by improper mounting or design flaw, the shaft may be flexing/torqueing the seal-head and wearing-out the piston ring/band. You would expect to see some leakage if that is what is happening but if in fact the pressure is dropping then it has to be leaking somewhere.

 

[shaggy829]

jasle
if you have a cobra shock and not an ohlins you could have many problems. the cobra pistons are crap they look good but thats about it , the ring lands wear out and the band will fall out of place and get torn to bits in the process and then it will contamenate the seal head . i have
built lots of the cobra shocks and thay always need a piston and band. you must inspect the body carfully for wear also, especially if the band came off .

shaggy

 

[Jasle]

Cool thanks for the tips. I'm off to a new suspension guy tomorrow. One of the local Pro's reccomends him highly. Hopefully the pricing isn't too crazy. One last race this year then hopefully the 03 by Feb?

 

[russ17]

Shaggy what kind of pistions are you using in those cobra's if i might ask andwhere can i get them if needed


russ

 

[shaggy829]

russ
I buy them from cobra. most of the time it's been at the races when i get these shocks because cobra won't work on them ,but they will sell you the parts.
shaggy

 

[Jasle]

Well the guy checked it out today and said the teflon bushing was broken in four pieces. he said the oil looked like it had not been changed in about 10 years. i think we had probably 15 hours on the shock. could we just have overheated it? He did do a 6 hour class with Kurt Hendricksen where they kept them riding almost the entire class.

Ist he ohlins really worth the $550????

 

[shaggy829]

the ohlins would be worth the money if you can put it on the new bike also.
shaggy

 

[russ17]

Jasle I haven't seen the inside of a cobra shock but on alot of mini's the inside is raw aluminium I always send them out and get them hardcoated they seem to run cooler and doesn't break the oil down as fast. it also tightens up the tolerance between the piston and the inside of the shock. don't know on the cobra though

 

[Jasle]

Shaggy. I'm told the 03 will come with the ohlins as stock. We want to keep our 01 as a backup though and I don't want to fuss with the shock. Still not sure if I'll buy the ohlins for it though. I could sell the 01 and afford another 03 for the cost of 2 shocks!
Russ, Thanks. I've heard of the hard anodizing for the suspension parts. I'll really check it out once we get the new bike. I think a total teardown prior to running it will be in order. This year the kid actually stands a chance of competing. he is really coming along and since I can only control 5% of the equation I want to make sure I'm on top of my end of the deal.

Thanks!!!!! I think I'm off to the store to pick up some reading material on suspensions. I've got the motor stuff figured out but rear suspensions are still a mystery! Any reccomendations?