glagola1

Keep in mind that a dyno plot is only a small snap shot of how a shock works on a car. Like engine dynos, the plots aren't exactly comparable between different dynos either.

User 121020

Can someone add some of this info to the Auto-x FAQ and STR build thread? It would be nice if these plots remained easily accessible.

Great discussion, guys.

bronxbomber252

I figured. Just throwing out another data point. That said. even near full stiff i have not had issues with bumps even in the bumpy lots we use up here in the Philly area and such. which goes to show that snapshot point more. Somehow my fronts even near full stiff stay on the ground and never seem to loose traction (unless i do something stupid... which is often... but not applicable to this thread) Granted however I have a much smaller front bar than you (oem 01) so I dont have as much force pulling that wheel up.

My rear shocks are similar but have less force at full stiff (I also run a softer spring back there). I have them backed off a bit in order to settle down my tail a little in transitions but at full stiff i also never had issues with bumps throwing me off (on my rears my low speed is similar to glagola's front shock, and my high speed is quite a bit less)

I also wonder if my valving is somehow set to account for what you mentioned earlier about at the beginning of the rebound stroke after a bump. But I dont see how that is possible.

PedalFaster

Yup. This is a great thread -- it'll probably be a bit before I have time to update the Stock FAQ, but I'll figure out how to work these into it.

Forcednduckshn

[QUOTE=captain_pants,Mar 31 2010, 05:55 AM] +1 on wasting your time testing on old Hoosiers.

Forcednduckshn

Another question for you all: (Perhaps worthy of a second thread) How do you feel about low/zero gas pressure shocks? In an autoX setting will the shocks cavitate? (make bubbles in the fluid) If this happens, does it create a lot of inconsistency in the shock performance?

The Grimes spec Yellow calls for zero gas pressure. Great for getting just a bit lower ride height, not good for cavitation. Thoughts/comments?

macr88

I do understand that rebound can definitely affect the car negatively and have always been of the thought that less is more. You're better off not having enough than having too much and your explanation earlier about the tires keeping the car down is classic because somehow people think that's what happens.
I understand the outcome but I guess I never thought low speed would cause that.

macr88

I think someone posted DG's link and he goes over it here http://farnorthracing.com/autocross_secrets6.html

Forcednduckshn

Yes I was about to post that link, that write up is what got me thinking. What I'm curious about is what people here have experienced with zero gas pressure shocks - specifically - is cavitation really a big deal in an autoX environment?

TheNick

Has less to do with cavitation for autox and more to do with compression valving. Twin tube and non-remote reservoir monotube shocks MUST HAVE GAS PRESSURE to have compression damping. If you have no gas pressure - then you have really inconsistent compression damping.

Remote reservoir shocks on the other hand - don't need gas pressure to get compression damping. The diameter of the hose orifice provides enough pressure to force the oil through the piston valves during the compression stroke. This is why you can run a really low gas pressure on a reservoir shock and get away with it (not that you would want to).


So on a twin tube shock - the amount of gas pressure increases the compression damping. On a reservoir shock - it doesn't. It can increase the stiction and nose angle (initial movement of the shock). It also preloads the spring. It can add spring rate - but not in the same way as a coil spring.



Marc - you'll change your mind once you drive a car with a lot of low speed compression. Its phenomenal feeling. I have the same rebound valving as Corey's car and I hate it. I can't use anything other than full soft - and I got the same story from Stimola about how I'll hate low speed compression and that his rebound valving is what EVERYONE who is anyone in SCCA is using. I had to fight like hell to get what I wanted in my shocks for the compression - I'm not going to give SRP any more of my money so I'm going to try revalving my Penske's on my own next offseason - I really would like to be able to use the knob on top of the shock. To be honest with you - with as crappy as the rebound valving is - I don't understand how they are even in business if they do this stuff on the road race cars. He even gave me the line "Rebound increases grip" - ha, my ass it does...