Lozer Posted August 10, 2018 Report Share Posted August 10, 2018 So I'm looking at my dime and notice the front track width is substatially wider then the rear (2"). I've been fighting with some understeer issues and having alot of scrub. That being said the rear is sticking down like is glued in turns. I'm running a 71 510 (adjustable everthing) with an sr20det, 4.44 lsd, 10" wide 16" wheels. So Im wondering what anyone else is running track width wise for thier autox/ track toy. Quote Link to comment
paradime Posted August 10, 2018 Report Share Posted August 10, 2018 (edited) You have a 10" wide tire in front? that seams huge. What is the offset on the rims? If you have adjustable lower control arms they may be adjusted wider than necessary. Have you had the car on a rack to check alignment? If so, what are the numbers. Edited August 10, 2018 by paradime Quote Link to comment
datzenmike Posted August 10, 2018 Report Share Posted August 10, 2018 Stock 510 tread is 50" front and rear except the goon which is 0.2" wider on the front and 0.4" narrower on the rears. So do you have rim spacers to clear larger calipers??? Rim offset is different from the rears? Do you have stock struts??? Understeer LSD or welded rear end will cause the front to plough into corners. Front sway bar replaced with something TOO stiff OR add a rear sway bar to compensate. Front springs too stiff OR stiffen the rear springs to compensate. Quote Link to comment
Lozer Posted August 10, 2018 Author Report Share Posted August 10, 2018 Running flares and adjustable everything with 280zx brake/struts. Front rim offset is 5" rear is 5.25" Ride height is 6" front and 6.5" in the rear measured from the where the top of the body seam. ok so the front is 66.5" rim lip to rim lip Front spring is 350 lbs with the futofab ka/sr sway bar. Rear is 66.25 rim lip to rim lip. with 475lbs rear springs (coil overs) (i know too stiff but i like it) no rear bar. Im still measuing so i'll get back to with more info in a bit. Quote Link to comment
Lozer Posted August 11, 2018 Author Report Share Posted August 11, 2018 So after bashing my skull in for a few minutes. I made a perfect box around the car, measured from 20 different spots on the frame, chassis, and suspension pick up points to get it dead center. Conclusion was front pass side was 3/4" in and driver side was 1/8" got down did a full alignment and extended the LCA and now my front is 1/4" wider then the rear and my understeer issue seems to be gone + the steering is substantially lighter...... 2 Quote Link to comment
paradime Posted August 11, 2018 Report Share Posted August 11, 2018 Glad to hear you've restored equilibrium. Dude, does your chiropractor know you're running 475lb springs in the rear? I was dumb enough to have my SR 510s alignment done at Wheel Works once, and those monkeys had my lower control arms shifted 3/4" to the passenger side. WTF they thought they were doing I have no clue. Quote Link to comment
Lozer Posted August 12, 2018 Author Report Share Posted August 12, 2018 After the autox today I will not be running those springs. LOL they were to adress the understeer issues. Quote Link to comment
paradime Posted August 12, 2018 Report Share Posted August 12, 2018 Stay at it man, It's a long process of modifying, tweaking, testing, and repeat. After installing Jeffs custom rack and pinion front X-member I finally got my suspension pretty dialed in with, 300lb springs all round, 1.125" McKinney front sway bar .75" rear, front 0.08º toe in 0.16º total, 1º camber. 0 camber In the rear -.09 toe out, and have the T3 coil's preload settings at 4 front 7 rear. I know there's a lot of debate on wether or not to run a rear sway bar. Either way, the goal is to eliminate the 510's chassis roll camber shift, aka trail through steering, aka primitive 4 wheel steering. If you look at the most successful 510 track cars, they're all lowered and have very little body roll. The BRE 510s had 1" rear sway bars Troy Ermish's Vintage B sedan 510 same thing Tom Anker's national champion autocross 510 had absolutely no body roll. He ran no rear sway bar, but had 275lb. springs up front and 1100lb. in the rear. Yeah, that's not a mistake, 1100lb. From what I understand, that's what Bob sharp was running on his 510s in the Eastern race circuit. If John Mortin won TranAm in 71 and 72, Troy Ermish holds lap records up and down the West Coast using a rear sway bar with lighter springs, AND they avoided the discomfort of 1100lb rear springs? Shit, I'm thinking Bob Sharp and Tom Anker were a sadists. 1 Quote Link to comment
demo243 Posted August 12, 2018 Report Share Posted August 12, 2018 (edited) 1100 lbs in the stock location is about the same as a 275lb spring on coilivers (someone has a rough conversion somewhere on ratsun) due to the leverage the rear arm has over the stock spring being that it is inboard from the axle shaft. When you go coilovers you move the spring all the way out to the end so the wheel/arm loose that leverage and it becomes more of a 1:1 ratio. I'm running 300 front springs on my coiliver and cut in half 650 eibach spring making it 1300lbs per side in the stock locations I also have a big sway bar front and a rear sway... need to measure that one though. On smooth pavement the car is on rails and there is hardly any roll... however when it gets rough it does "skip" a bit... and I think I need to replace my shocks as they are not valves for such heavy spring rates. The car also doesn't like the rain... gets very twitchy when its wet.... but old falken tires probably don't help that Edited August 12, 2018 by demo243 1 Quote Link to comment
datzenmike Posted August 12, 2018 Report Share Posted August 12, 2018 3.8 is the cantilever ratio. Because of mechanical advantage (leverage) an 1,100 spring forward of the axle only acts like a 289.47 pound spring on the axle. 1,200 pound springs are not unknown for racing. 2 Quote Link to comment
paradime Posted August 13, 2018 Report Share Posted August 13, 2018 Brain fart, stands to reason the B sedans were running stock spring position. ? Moment of egocentricity there thinking all 510s are coil over. 1 Quote Link to comment
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