Minimum C/O Spring Weight

[DocB]

I've been following the Spring Hz thread, but thought I would start a new thread so as to not muck that one up.

I have track measured my coil-over's travel in compression and am using just about all of the bump-stop's absorbtive abilities (95-99%) as spec'd from the manufacturer. The spring weights are what my math told me I should run, but I am still looking to tweek the handling. I do not want to go over 100% of the bump-stop travel as this, as you all know, is a no-no, and will destroy the car's handling in a corner.

This may sound very basic, but I have one simple question:

Using up 99% of the bump-stop, is this then the minimum spring rate I can/should run?

 

[sheizasosay]

You have an actual FR500S? So you have Sachs on the car now? Is your car's ride height setup for the designed ride height of the Sachs? I take it you removed the 500/300 in/lb springs that originally came on the car. What is on it now?

Why are you "purposely" using almost ALL of the bump-stops in place of more spring when their is possibility of damaging REALLY good dampers? Are you into the bumpstops on all corners?

 

[DocB]

Yes, #527.
Yes, Sachs on the car. Shocks are dyno-ed and up to snuff.
Yes, ideal ride height as spec'd by Sachs.
Yes, 500/300 removed and upped spring rate.
Yes, into the bumpstops on all four corners.
No, not purposely into the bump-stops. Would rather not, but I am, because I am driving the car very hard and fast.
No, I do not want to, and cannot afford to, purposely damage my shocks.


Car always handled very neutral, with the old and new spring rates. I kept the ratio the same. Nose dive and front roll are much reduced, which was what I was originally after.
Tried a stiffer swaybar in the rear, but no good. Went back down.
Also, running 275-305 tires, square, now, DOTs and slicks. Whatever I can get my hands on.

Everybody keeps saying softer springs are faster, and I know every car is different, but I don't think this is the case for me.

Even Terry Fair, from Vorschlag, is running less spring in the rear than I am.

I just don't think it is wise to be so far into the bump-stops. Especially turns like #16 at VIR. Just trying to learn and get this noodled out a little bit more before this next season.

Hope to hear from some of you with good, sound, suspension experience pertaining to this. I never really saw it written anywhere that how far you are into the bump-stops is an indicator of where your spring rates should start.

BTW-Norm, I took the car to the last, cold, AutoX event of the season in November. Even on old, last run of the season, worn out, heat cycled out, Conti slicks, the car just ate up the course.

 

[sheizasosay]

I have track measured my coil-over's travel in compression and am using just about all of the bump-stop's absorbtive abilities (95-99%) as spec'd from the manufacturer.

This is why I said "purposely". Sounded like you had been doing the "95-99%" for little bit and that it was OK as long as you didn't tip that 1 extra %. My apologies for the misread.

Also, running 275-305 tires, square, now, DOTs and slicks. Whatever I can get my hands on.

I can't help but look at that last quote and wonder if you are in the bumpstops on DOTs, slicks and every other tire you run. A spring's effectiveness in keeping you out of the bumpstops has a lot do with how much grip the tire can make. Obviously my statement only holds true for turns and not bumps going straight. But if you are not in the bumpstops with 200 treadwear tires and are in the bumpstops with race slicks, then I would say that is telling. Spring rates that are right on a street tire are not gonna be right on race tires. That changes everything.

I know you are looking for the experts. I'm sure they will read the information I have asked you and use it to help you out with the answers you are looking for.

You might want to consider more compression or less rebound in the interim.

Good luck

 

[JAJ]

I have a dumb question: are you running through the bump stop range in a static cornering state after the suspension has taken its "set"? Or is it when you hit a bump - like a curb?

 

[DocB]

Can't tell. Measured the measuring rings jammed up inside the bump-stops when it came off track.
And yes, it could be either. Maximum compression travel at setting turn-in or curbing. Let me say that I am mostly easy on the curbing, but a hard hit does happen.
Either way, I believe the shock should not be almost bottoming out.
And yes, tires also contribute to the problem. I understand that. Not with the curbing part, but setting turns.