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shock valving and spring stuff

1K views 17 replies 10 participants last post by  F4iEric 
#1 ·
looking to buy a used penske double, however it is sprung for 190-200lbs rider but is newly refreshed

what im wondering is does the valving change with the spring rate, for instance can i buy this thing and just put a new lighter spring on it for my weight or would it need to be revalved as well
 
#12 ·
To the best of my knowledge the Penske can be adjusted for proper compression and rebound after a spring change without a teardown.

I would guess that there is some limit to that, however. But going from 190 to 150 or so?

My penske required a spring change after I bought my bike. (going from 160 to 190) No re-valving was done. The stock front forks were re-valved and re-sprung, however.
 
#13 ·
Grasshopper how much is your song? :) I need one on that Aprilia.

You'd be fine I'm guessing on that shock. As long as you look at a few things.

As I understand it. When you order a Penske shock, you give them your weight, bike and such. They then build YOUR shock with the proper valving and spring.

Penske shocks are rebuildable and can be adapted to other applications. If you had the shock and wanted to do this (as I'm considering on the Aprilia) it might be worth it. If you have to buy one second hand, have it refreshed, respring it and then buy the parts to adapt it. I doubt the cost justification is there.

Now here is what you need to look at Jason. IF this shock came from say a 600 RR which has a large leverage ratio, it is valved for heavy springs. Soooo. Me on a 600 RR might need an 800 lb spring. If you planned to put this on a GSXR where my weight of rider would need, say a 525 lb spring, the valving will probably be WAY off.

So... If you just need to go within a few spring rates, I'd say it's probably fine. If you have to do a large change, the valving will probably be off.

Also make sure the mount points are the right type. This may not be an issue. But on my FZR, it uses a U shaped lower clevis, other bikes have the center mount with the ball pivot, like my SV has at the top. Some bikes have a center bolt at the the top mount. This bolted to the frame. It also made it easy to shim for more ride height. But my point is, make sure it will fit your application. I'd hate for you to buy something and it won't go on the bike.

Yes, if you were running on an AMA grid, you'd probably change valving with big spring changes. I blew up my shock last year. I borrowed the Penske off Wink's SV. His was just refreshed. I mounted it up with my spring. I ran about 1.1 seconds slower. I couldn't get the bike to finish a corner. His Penske is sprung for a MUCH lower weight then mine. My guess is that I was blowing through the valving and I was losing to much ride height.

Remember, the main point of the springs is to hold the weight of the bike up. The valving and oil levels / weight do the rest. That's what you will read. But once the valving is in the ball park, the most likely change you'd see other then turning the knobs, is likely a spring rate change.
It can be done, but if your doing this to save money, be sure to cover all your angles.
 
#14 ·
Come chat at ACC this weekend and I can explain this more.
 
#15 · (Edited)
basically im looking at a sprint on teh shock that is currently set for a rider with about 20 lbs heavier than i am, its a gsxr 600 shock for my year bike which is the only ones im considering if i buy used simply because used prices plus refresh and spring put me too close to make a new one not the right choice

this one all id need to do its slap a spring on and go it sounds like :)


next questions is will i even benefit from this, my tires show no signs of poor or accelerated wear and aside from getting a slightly textured surface they look new.
 
#16 ·
next questions is will i even benefit from this, my tires show no signs of poor or accelerated wear and aside from getting a slightly textured surface they look new.
IMO you're probably ok with a stock shock if it is in good condition, the stock equipment is pretty good considering... I ran stock rear shock, that was never refreshed and had 30k miles on it up until last year. Eventually the oil had broken down so much that it could no longer provide enough damping even with the adjusters maxed out. When this happened I started getting really poor tire wear. I swapped in the penske and have been sitting pretty ever sense. As for riding, I did not notice a big difference in feel from a good working stock shock to the penske, if both are properly adjusted you wont notice a big difference at your pace (or mine), you need to be moving pretty good for it to matter.

My advice: If you stock shock needs a rebuild, go ahead and buy an upgrade (penske), if you're spending money might as well get better equipment to make future refreshes and customizations easier/faster. If however you are not experiencing any problems, keep your stock shock for now, no sense spending money on something you don't need, there's plenty of other places to spend the money that will make a bigger difference (like tires and track time).
 
#17 ·
Will you benefit from a better shock. Probably, will you recognize it? Maybe not right now. But you won't find the plateau of the suspension holding you back if you have good equipment. If you're looking at a shock, for the same model bike with only a 20lb difference. You should be fine. To many people worry about the forks of a bike. There are many benefits to a proper shock. The forks on today's bikes are very good. I believe the shocks are the weaker link. Spring the front end properly and refresh it. Then get a good shock. The money spent will be saved in tire life. The shock plays a very important part of the suspension and it's setup and consistent operation is key to a well working bike.
 
#18 ·
Another advantage of the Penske is the right height adjustment. Obviously you can do the same thing with a stock shock and shims, but the adjuster is finer to match the height in the front. Which of course matters more if you have fork extenders. Penske also makes different pistons for their shocks, some work better then others from my understanding.

The only thing I wish is that I had the chance to ride mine stock and with the suspension (ak20's, extenders, penske triple) back to back to see the difference.
 
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