Hey all,

I know there are too many variables so just looking for a general answer.

If I have:


F
795 810


735 695

on my wheels, how much would I adjust my height in back to get closer to a good cross weight (of course I got adjustable coilovers)?

I ask because I did not have have an opportunity to adjust when I got it corner weighted.

Thanks,
Ben

 

Its pretty much impossible to say how much without having the car sitting on scales. Just from looking at the numbers you will need to put more pressure on the RR or LF but any moves you make will be guesses.

 

yeah, basically you have to make the adjustments with the scales, and see what they come out with after each adjustment.

 

What's wrong with the current cross? 795+695=1490, 810+735=1545. Total: 3035. So, LR+RF/Total is a 50.9% cross. You're at 52.8% front.

Was your weight in the drivers seat? What car do you have that comes in at 3035#? Do you know your current ride heights and if there's any rake in the car?

 

Was the driver in the driver's seat?

Did you make sure the tires were correctly inflated to the exact race pressure?

 

Trying to get to perfect cross weights not front/back. Sorry for clarity sake, I should not have specified back adjustment as it could involve all 4 tires needing adjusting to get the back pass side to equal the driver's side.

Yes the weight includes driver in the driver's seat.

This is an FC with V8 conversion so it will be front heavy.

Hardly any rake. Maybe 1/4" or so.

 

Yes and yes.

 

While this relates to a Spec Miata it has the basics - http://www.specmiata.com/setupguide/...ing%20Tips.pdf

And yes you need to do all the adjusting while the car is on the scales.

 

What are your spring rates front and rear? Theoretically it is possible to work it out based upon front and rear suspension geometry, spring rates, thread pitch on your coil overs, etc. But in reality the guys are absolutely right - it is best to do it while on the scales.

Realize that changing the height in back will also slightly change the rear camber. Not hugely, but you may add or subtract a tenth or so which may worsen your setup if you are already off slightly in that same direction.

Now, having given all the warnings and observed that your cross weights aren't really all that bad, I would say that it probably wouldn't hurt that much to raise the right rear perch one half twist on the collar and drop the left rear perch about the same amount.

I had to do the same thing once, but that was on the recommendation of my suspension guy who had another appointment coming up and we ran out of time on the rack. In addition we had been playing with the alignment for an hour and had a pretty good feeling on the impact of small adjustments to the coil overs.

Good luck,

-bill

 

8/6 are the spring rates. It would be interesting to figure it out as you state.

Your comment on raising 1/2 twist is as good as I have heard. I actually did a full turn or about 1/8" on the right rear a few days ago. Personally, since I am running on a left turn track this weekend, I would prefer to be a small bit light on the right side...but only a small bit.