Region: Delta
Car #: 77
Year : 1990 Posts: 74
Status: Offline
posted
If my car were 52% cross weight at that height, with front wheels weighing 609 each, LR at 602 and RR at 509, total weight of car with driver at 2329 lbs. I don't have scales, so I am trying to figure out a closer setting to 50% CW. I am wondering what 1/2 turn up for the LF and RR, and 1/2 turn down for the RF and LR would do, CW-wise? I'm thinking that would help the CW without going too far-but maybe not far enough.
Anyone have an educated answer? I'm trying to get to 50%, or as close as possible to that CW. I could fine-tune at the track if my buddy can bring his scales to the track. Am I better off not to adjust anything without the scales? Thanks.
Region: Delta
Car #: 77
Year : 1990 Posts: 74
Status: Offline
posted
What I'm looking for is a better starting point for my first lap at the track. By the way, my '90 SM has the '99 shock hats.I'm thinking 1/2 turn down on RF and LR, with 1/2 turn UP on LF and RR would give it a better balance from my initial ride height (prior to alignment) of 4 3/4" with me in it. I have not remeasured the car with and without me in it; I'll do that later today.
Does anyone have a SWAG of how much difference the four 1/2 turns would make? Surely that would not over-correct, would it?
Region: Lone Star
Year : 1990 Posts: 4253
Status: Offline
posted
Jack the car up from the diff and see which tire lifts first and adjust appropriate corners from there. Old RC trick for when you don't have a tweak board.
-------------------- "Your victory is tainted! Asterisk! Asterisk!!!"--Lisa Simpson
Region: SFR
Car #: 89
Year : 90 Posts: 163
Status: Offline
posted
If you are “wedged” (cross more than 50%) you need to do the following. Up on the RR & LF (equal amounts, ¼ to full turns) Down on the LR & RF (equal amounts, ¼ to full turns) JD setup guide..
I think 1/2 a turn would probably do it. But in all honesty if the car is alligned where it's at now and this is a track day, just drive it.
Region: Delta
Car #: 77
Year : 1990 Posts: 74
Status: Offline
posted
Jeremy, I have borrowed some scales and have 2 days before track day, so I think I'll try to improve on the setting. BUT, the question comes to me: How close to 50% is close enough. Someone else has suggested the numbers are "close enough" to just drive as is, but then I thought J.D. had suggested we get within .5% of 50%. Would you adjust it if you had 2 days to get it done? Just interested in how to control this animal.....
Region: Indy
Car #: 33
Year : 1994 Posts: 422
Status: Offline
posted
Reggie,
I had the same question for my 94 SM so some time ago I found out by running a little experiment on the scales: 1 full turn on all 4 corners (ie RF and LR down 1 turn each and LF and RR up 1 turn each) yielded 2.45% change in cross weight %. As JD correctly points out you must do all 4 perches simultaneously otherwise ride heights change and we all know where that gets you. Your results may vary. ;^)
PS- I'm sure many others have done this experiment as well so I'd like to see what numbers they got.
-------------------- "In our sport if you go out of bounds you're most likely not coming back" Michael Waltrip
Region: NASA-SoCal
Car #: 23
Year : 1995 Posts: 912
Status: Offline
posted
We got a little over 3%.
-------------------- Rob Gibson RJ Racing 2010 NASA Nationals TTE Champion 2008/2009 WERC Champion 2007 NASA SoCal SM Champion rjracing.net Weekend-Racer.com
Region: Delta
Car #: 77
Year : 1990 Posts: 74
Status: Offline
posted
I got 3.1% change in crossweight, going from 52.3% to 49.2%. I made one other adjustment, approx. 1/6 turn upward to LR and ended up with 49.871% CW. This isn't 50%, but is about as close as I expect to get to it. I calculate that to be within 3 lbs. of optimum. Thanks to all you guys for your help and suggestions.
Region: Delta
Car #: 77
Year : 1990 Posts: 74
Status: Offline
posted
Update: As of the second week in November I have now finished leveling and scaling the car, resulting in a 50.0% cross weight at 4 5/8". Thanks to a generous friend who loaned me his computerized scales I am now good to go. I realize I might need to make some additional adjustments, but this is much better than when I first started this process of Ride Height and Cross Weight adjustments. Thanks to everyone who chimed in!
Email this page to someone! | Subscribe To Topic
Printer-friendly view of this topic | Subscribe To Topic