I finally got Carmen on some proper Longacre Corner Weight Scales tonight, with some pleasant results.
Car is a '94 LS fully optioned, less spoiler, built to autocross in STX.
Weight Relevant mods: Corbea FX1 Pro one piece fiberglass drivers seat. TEIN SS-p with my own rates and damping, side exit exhaust, Motegi TrakLite 2.0 14.3lb 17x8 wheels, 235/40/17 Yoko Advan Neovas.
Of course everything was emptied from the car, has just a hair over 1/2 tank of gas (just like I run it in a race) tire pressures at race settings 35f 32r. Me in the drivers seat, as I would be driving.
Weight W/Out: 2606
Weight W/Driver: 2798
LF 935 RF 908 (65.8%)
LR 506 RR 448 (34.2%)
RF-LR Cross 1414 (50.5%)
LF-RR Cross 1348 (49.5%)
The most surprising aspect is the corner weights. To be that close with nothing done to balance the car, only .5% off is amazing, the guy who's scales they were and I were very surprised. Biggest thing is moving weight from the LF to the RR...read on...
Of course, now I'm going to screw it all up. First I have to even the caster, the LF as .5deg more than the RF, and re-set all alignment specs. Next is weight reduction. A/C removal, interior swap from tan leather to black cloth, and big one, battery relocate.
I will be using a lightweight race battery, and placing it just ahead of the RR wheel. Not only will this get rid of the weight up front, but put some weight over the light RR wheel. Placing it in front of the wheel will keep the weight closest to the car's center, thus preventing any pendulum effect it could otherwise have located behind the wheels.
After that, back on the scales, first disconnect the sway bars, second adjust the height at each corner to obtain 50/50 cross weight, third, re-connect sway bars but dialing out any sway bar pre-load with the adjsutable enlinks at all four corners.
With luck, this will make the car faster, and easier to drive fast
Who's scales did you use? I doubt my spoilerless, sunroofless and A/C-less '93 is much lighter! Similar weight plus a much healthier engine ... no wonder you pulled so hard on me!
Let me know when you're working on Carmen this week and I'll come help and grab those tires from ya.
The MSR Team Scales at Charlie's (holy 6-car garage Batman!!) They're Longacre units, great scales, easy to setup and use.
I was surprised at the weight too, IIRC Kitty weighed in around 2700 with more gas, and I believe I wasn't in the car, but those were different scales.
With any luck I can get the car near 2500lbs, and with 100lbs equaling .1 faster 1/4 time, and every 30lbs can be .1 faster on an autocross course, I expect great results
Call me on the tires, I'll be home swapping the interior and doing the battery re-locate just about all weekend
Well I got all the prep work to do corner balancing done.
I adjusted the caster as much as I could. The LF had .7deg more than the RF, thus with the wide tires I had a nasty pull. I got as much out as I could, and without getting it on the alignment rack it feels like I got the LF about .3 closer, but still not dead on. The steering is much more even and has a lighter feel to it, but still a slight pull. In the interest of even steering feel and keeping everything even I may reduce caster on the RF to equal the LF.
I also have the interior swapped, the heavy parts at least. I haven't had a chance to swap the dash or parts from the shoulder line up (pillars, headliner) so I have a black and tan interior at the moment :P
Battery re-locate with a 9lb battery right behind the rear seats on the RR is done, A/C is gone. Maybe it's psychological, but I can feel a difference in the way the car drives and rides. Guess getting rid of 60lbs on the front end is that noticable, of course the scales and lap times will be the most telling.
With any luck I've managed to remove up to 100lbs. from the car. If so I will hit my 2500lb STX legal goal
very nice! I wish i could afford to make my 6 a plaything until then the audio build continues.
1994 MX-6 LS w/ KLZE, chipped ECU, headers, test pipe, Volt muffler, CAI, Outlaw Spacers, Centerforce Stage II clutch, 17" Flik FTD wheels, and black leather interior. http://www.cardomain.com/ride/2616648
First I had some minor alignment issues to tackle. I haven't checked it on a proper alignment rack in some time, and knew I had a caster problem to solve, I had 4.0deg on the right and 3.4 on the left, I got it to 3.6R and 3.5L. Glad I did it, car drives MUCH nicer now, and no more pull!! I also found I had too much neg camber on the LR. Started with -2.1 ended with -1.6 on both sides. Front camber is -2.8deg, 1/8" toe out for race day, 0 toe front and rear for non-race days.
On the weight reduction/corner balancing I didn't quite hit my 2500lb goal, however results were VERY pleasing.
Same as before, empty car, just over 1/2 tank gas. There was one addition in the form of a 2lb halon fire extinguisher mounted behind the drivers seat, and I likely had 1-2gal less gas. So the plan is to first disconnect the sway bars to eliminate any pre-load they may have, and then to adjust the height of each corner to attain 50% cross weights, here's how the numbers came out:
Amazing!! Moving all that weight around, and the cross weights are not only better, but only .1% off!! That's less than three lbs off, and close enough to leave alone, or risk chasing our tails too much.
But, there is one thing we hadn't done which is to dial out any pre-load from the sway bars, so we disconnected them and found the front and rear had 5lbs of pre-load each. Thank You AWR For the adjustable endlinks
Final Numbers
LF 907 RF 863
LR 498 RR 467
RF-LR Cross 1354 (49.5%)
LF-RR Cross 1381 (50.5%)
Not quite as good as we started with, but now we know there is absolutely no pre-load on the sway bars. Unfortunately we were out of time, fortunately .5% is well within an acceptable margin. Especially when you consider that a gallon of gas weighs about 6lbs and I can burn as much as a gallon and a half during an event, the weight of the car is changing by .4% as the day progresses, AND apparently as I weigh 3lbs less than the first weigh-in, I change from event to event too
Driving impressions thus far, well it's dark so I'm taking it pretty easy, but the car does certainly ride different. It literally feels more balanced, bumps on the road feel much less pronounced through the front tires, steering feel is now even side to side, and the car certianly feels lighter on it's feet.
My next event is this Saturday, after that we have a Pro-Solo coming through town. Stacked up against national competition I'll get a really good idea of how fruitful my labors have been
Sorry for not answering your question months ago Metros
No Pre-Load on the bars means that as the car sits it is completely neutral, there are no forces acting on the suspension other than the car's weight on the springs. No Pre-Load means the sway bar is completely neutral until you load it under cornering one way or another.
When you do load it the forces it experiences and transfers are equal left to right, thus you gain a much more predictable car that behaves the same when cornering either way.
And it absolutely works. Between the re-distribution of weight, and the small adjustments to the sway bars the car rips through slaloms with a LOT more confidence, I'm able to go much faster with fewer corrections, and the car feels nearly identical upon turn in left or right.
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