rear shock setting

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craigs
Posts: 82
Joined: May 29th, 2007, 5:46 pm

rear shock setting

Post by craigs »

Where should I set the knob at for my rear Penske shock? I don't have the talent or time in FV to set it where I am fastest - too inconsistent and learning lap by lap. Where should I set it and forget it for this first year. I'll be running mostly at NHMS.

Thanks,

Craig
FV80
Site Admin
Posts: 1195
Joined: June 27th, 2006, 9:07 am

Re: rear shock setting

Post by FV80 »

Set it on one .... or six. There is no way to tell with the (lack of) info you provided - and there really isn't any way to tell anyhow. Every car is different and if you have no real experience in a Vee - it won't make enough difference to matter. Shock settings will generally come into play only when you are starting to look for the last second or so of speed. NOW - if your shock is NON-FUNCTIONAL - that's a different matter. Jump on the back end and let it spring up - it should NOT 'bounce' (adjust the rebound to control that) - and it should go DOWN relatively easily when you 'jump' on - adjust the bump for that. In other words - if YOU bounce off when you jump on it, lower the bump number - if you slam it down to coil bind when you jump on it, raise the bump. If it still slams down, your shock is broken or needs rebuilding badly. If you can't tell any difference between 1 and 6 (entirely possible), just set it on 3 and forget it. In my experience rebound is more important than bump - rebound is controlled (assuming you have the double or triple adjustable Penske) by the valve inside the end of the shock eyelet away from the spring perch. Run it in (use a small allen wrench to adjust it) clockwise to the stop and then back it off about 12 flats to put it about in the middle. Depending on the internal valving, it might have a LOT of range ... or might not. If your rebound is too stiff, you will get 'jack down' - if it's too soft, you will 'bounce' off the bumps. For now, just set it in the middle and forget it.

In all likelihood, yours (if your shock is decent) will just 'go down' and 'come up' - anywhere in that range is fine to START learning how to drive :-).

Your shock should be rebuilt about once per year - more often if you race A LOT. If you don't know the status of the shock, it would be a good idea to send it to someone and have it rebuilt and dyno'd so you know where you are starting. Most people who do this, would have a general idea of how to valve it for a 'general' fv setup. Fred Clark at Caracal Cars and Joe Stimola (Penske dealer/service rep) are 2 people I know with a LOT of FV shock experience - I'm sure there are others. Schings might do it too, but I don't know for sure.
Steve
The Racer's Wedge and now a Vortech, FV80
SR Racing
Posts: 1205
Joined: June 24th, 2006, 1:58 pm

Re: rear shock setting

Post by SR Racing »

Steve is right as usual for set up.... But... At the risk of irritating shock rebuilders... I dont' agree with the yearly rebuild requirement. If you have a Nitrogen filled shock, you might want to check and purge that frequently, but if the nitrogen pressure stays close and the shock isn't leaking, the valves are the only things that might be worn and they should go much farther than 8 or 10 weekends. IMO
FV80
Site Admin
Posts: 1195
Joined: June 27th, 2006, 9:07 am

Re: rear shock setting

Post by FV80 »

SR Racing wrote:... I dont' agree with the yearly rebuild requirement.... IMO
Jim,
I thought the same thing .. till I tore mine apart myself after about 15 race weekends. The inside fluid looked 'dirty' and it really looked bad. I had to replace several shims as a result of contamination and abrasion between them from the dirty fluid. It is always possible that mine got some 'dirt' inside it during the previous rebuild, but I decided to err on the side of caution after that. (it was still holding pressure just fine)
YMMV :mrgreen: ,
Steve
The Racer's Wedge and now a Vortech, FV80
craigs
Posts: 82
Joined: May 29th, 2007, 5:46 pm

Re: rear shock setting

Post by craigs »

Thanks guys. I have the Penske 8100DA rear. I just turned the adjusted 25 turns towards the back. What's up with that? I assume it will just spin forever and that I need to line a number up with a "notch" on the outside of the shock? How do I set it to "6" or "1" or any other number? The dial is numbered 1 - 6. If I want it at say "3" where do I line the "3" up with?

BTW - my fronts (Penske 7014) are out being rebuilt now. Because of my wealth of knowledge I told the builder "leave em valved where they are and just make em right".

Thanks,

Craig
brian
Posts: 1348
Joined: June 26th, 2006, 12:31 pm

Re: rear shock setting

Post by brian »

There should be a reference point on the cannister to align the compression number. The rebound adjuster can be turned clockwise until it seats, then the number of clicks from closed is used as a reference. Don't jam the rebound adjuster tightly against the stop. Being a nubie, I would suggest running the compression on full soft (1) and about 6 clicks off on the rebound.

Like Steve, I have found that the shock needs service regularly. I've seen oil go black and shims crack over a few weekends. Penske recommends changing shims each time the shock is torn down. They tend to get bent and develop a memory. At $7 it's not a big deal to change them just a bit of planning. Look around your area for a circle track company that services shocks. They're usually cheaper than RR folks and will have inventory available.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
f clark
Posts: 42
Joined: December 25th, 2007, 8:30 pm

Re: rear shock setting

Post by f clark »

Good Mornilng Craig,
In reguards to your shock questions,and with out knowing what kind of car you have.
I suggest that you start with the compression adjuster (can 1-6) on 3, its the middle since it appers you have a "A" valve for compression, thats the middle setting. Most run "AA" for compression valving but there is not a lot of difference. 1 is full soft, 6 is full hard for the can.
Now the rebound screw. Close it completly, thats in or clock wise, thats full hard, then back it out 12 flats thats 2 turns of the screw, ccw, this is 1/2 of the full adjustment for rebound, 4 turns or 24 flats is the most open for the rebound, you will gain nothing else by opening it further. The "D" valve is very common for FV shocks and used by most.
The rebound screw that you turn moves an alu. rod that in turn pushes a needle valve when your are turning it in or CW ,when you then turn it out(ccw) to the 12 position you are only turning the screw since none of the above components are hooked together. you must "JUMP ON or BOunce yor car to allow the oil to move the needle to the set position, on the track it takes only a small bump or slight shock action to get this to happen.
I do a lot of these shocks and would be happy to help you with yours.
Fred Clark
904-234-5603 cell, most of the time,
craigs
Posts: 82
Joined: May 29th, 2007, 5:46 pm

Re: rear shock setting

Post by craigs »

Thanks guys. Rear shock set at 3 for compression and I left rebound alone for now. I'll probably have someone at the track look over my shoulder so I don't screw it up. Front shocks were picked up from Ric Racing this morning all rebuilt and ready to go.

Craig
f clark
Posts: 42
Joined: December 25th, 2007, 8:30 pm

Re: rear shock setting

Post by f clark »

Craig,
I forgot to mention to you about the gas (nitrigon) in your shock, I use 225 lbs. in mine, others vary the pressure from 150 to 250. Gas pressure is a tuneing devise and keeps the oil from foaming, the less gas the less pressure is required to get the shock,spring, rodends etc to START to move, up the gas and the harder it is to get these things to move.
This action is refered to by some as BUMP or Nose pressure and has no effect on the valving action AFTER the shock starts to move.it just controls the oil foaming
Also if you see a lot of oil seeping from the shaft seal area, its time for a seal replacement, or if the gas goes away real fast, there is a slight leak somewhere that is sometimes hard to find.
Hope this is helpfull information.
Fred Clark
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