Halon

iTrader: (6)

Car is a 92 SC300. 61mm @ 20psi, 6 speed, 3.26 rear diff.

At the track my 60' times are pretty bad, and the wheel hop sure isn't helping me. See vid
https://www.youtube.com/watch?v=tcPb...ature=youtu.be

I'm running TT wheels with 275/40/17 NT05R drag radials. At the track I had them at 20psi tire pressure.

My rear subframe I recently rebuilt with all new bushings. Where possible I used TRD bushings, otherwise OEM Supra bushings were used. Diff ear's have poly bushings. This is supposed to be my fast comfy cruiser, so no soild bushings were (or ever will be) used.

Current suspension setup is TT springs with Bilsteins. Wondering if perhaps some form of the Gixxer_Drew setup would help me (plus probably ditch a few pounds!).

This car has 10's in it as-is if I can just hook and get a 1.8 60'. So I'm going to try and leave the power where it's at, and focus and getting the car too plant the power and go straight and try to eliminate the wheel hop

Looking for advice from people who have been there. I'd like to stick with drag radials as I see a lot of other people who claim to have way better 60's on DR's. Perhaps the track was in **** condition, but I feel like I should be able to do way better than 2.1's on drag radials. Also this is mainly a street car, my fast comfy cruiser, so I'm trying to avoid a crazy stiff suspension. But willing to listen to what anyone who has been here before has to say.

Lexusfixer

Have someone shoot some video of the car from behind, I had a hell of a time getting my corvette to launch clean. I run BFG drag radials, the fix was pretty simple, just a couple air adjustments to rear tires, RR 21psi cold LR 17Psi cold. You also may want to shoot some video of the front to see if you have a corner of the car coming up. Check out your local speed shops that have a good chassis guy, sometimes you can get it up on scales and dial it in.


I just got done with a ton of upgrades on my motor and again I am having problems getting it to hook up , I replaced all the rubber bushings with very stiff poly bushings that helped a little. I drew a line with a paint pen across the face of each bushing, two passes and the paint was all cracked, this showed how much the poly bushings were flexing, not as bad as the stock rubber but still enough to allow movement in the rear suspension. I am currently having solid aluminum bushings made to get rid of any movement in the rear.


Things to look at when you video tap is rear end squat, is it even? Look at tires from the side of the car is one moving forward? Find a cheap camera you can mount under the car to view all the suspension components, I know you will be shocked when you see how much movement is occurring when your throwing all that horsepower and torque at it. If you only have one tire that is hopping it may be a very easy fix.

CatManD3W

iTrader: (18)

Maybe get some wider wheels.....and run a wider tire.....

Personally I am looking to step up to 305 or 315 rear tire....the 275's just dont cut it....

Other solution would be to try a drag radial tire 15"....with a 60 or 65 sidewall

Lexusfixer

Check this place out


http://www.mc2racing.com/tech/20061012a/

Lexusfixer

and as a side note I am putting 725 HP to the ground with a 275/60/15 BFG DR as it is the standard and required size for our local drag radial class.

Halon

iTrader: (6)

I'd like a wider rear tire, but I think a higher sidewall would be more beneficial. The 275 width isn't that bad, but my 40 sidewall could be better. I've actually spent more time than I'd like to admit trying to figure out a new wheel setup but I struggle to find something that's right for me. So I continue to stick with my simple TT wheel setup.

My ideal wheel setup would be a set of 18's all around with NT05R 285 or 305 drag radials in back for my normal street setup. And then a matching pair of either 15 or 16" wheels that I can put some taller walled drag radials (probably some version of ET Street Radials in the 50-60 height range) on for the track or street fun. Can't seem to find a wheel I can do that with that I think looks good, comes in decent widths, comes in a normal offset rather than a stance offset, and aren't heavy as bricks.

CatManD3W

iTrader: (18)

CCW...or Weld should have what you are looking for....but $$$$

Halon

iTrader: (6)

Right, I guess that was the other part I left out. I'm not interested in paying $3k + for wheels.

CatManD3W

iTrader: (18)

Check SupraForums....those guys change wheel setups all the time....you can generally get some pretty good deals

motorheaddown

I've cut 1.4x sec 60 foots; so, I've had some success. But admittedly, I'm inexperienced and had help.

I run a small bias-ply Hoosier on 15" wheels and Megan coil-overs. The launch was pretty sensitive to tire pressure, but it was between 14 and 15psi, and the Megans were set very soft but didn't bottom out when the car squatted on the launch. Boost was set to 15-16psi to keep from spinning out of the hole.

Thanks,
-scott

Halon

iTrader: (6)

What tires are you running up front with Bias Ply in the rear? The concern I have is how I read it's "DANGEROUS" to run radials up front with Bias Ply in the rear. So to run bias ply slicks, you're actually committing to an entire wheel setup (likely with skinny's up front). It'd be nicer if I could have my 18" street setup, and swap my 15 or 16's on the back with taller walled drag radials and matching wheels when it's track time or play time on the street. I dont' want to drive around on the street with Bias Ply skinny's up front.

motorheaddown

I'm running bias ply on the fronts and rears: https://www.clublexus.com/forums/per...-saturday.html

Driving it is a little hairy because the car "swims" down the track on bias ply tires; you can definitely tell there's no side-wall strength. Plus, bias-ply on the fronts prevents over-steering during the run.

I'm sure there are more experienced people on SF; so, you should post your questions there. But you can see just how much force is applied to the tires on a good launch. The side walls wrinkle when the car squats; so, I'm not sure you'll overcome wheel hop with a stiff side wall and 20psi of tire pressure when dumping the clutch. You could probably get away with it on an automatic, but a good 6-speed launch requires a soft suspension, soft tires, and a good clutch that you can dump without it coming apart. FWIW, I also run a re-tubed OEM 2-piece DS and flex coupler on the rear diff to protect the driveline. Too many people have broken their diffs with a 1-piece DS and no flex coupler. I also purchased solid diff mounts.

Oh... and I don't know how you're dumping the clutch, but I get on the two-step, slightly engage the clutch, and then dump it. After that, you hope for the best and hang on.

Just my $0.02...

Thanks,
-scott

HiPSI

iTrader: (2)

I thought drag radials were notorious for wheel hop on the track and normally end up with breaking the rear diff from it. It's the full bias ply slick that you want but then you have to be careful with the front tires as mentioned above. This is what I've read on supraforums with guys breaking their 6 speed diff's, not from experience. I'm in need of a new rear setup as well.

I bet it doesn't wheel hop like in the video on the street.

Halon

iTrader: (6)

Thanks for your reply, you're starting to get at what I'm looking for. My car is a 6-speed, an you said to launch a 6-speed you want a soft suspension. I did not know that. I'm currently on OEM supra springs and bilsteins. I'd like to go with coilovers for the weight savings, and was wondering if I need to be looking at a stiffer suspension, but sounds like I have it backwards. I want a soft suspension. So suspension wise maybe what I have right now isn't so bad.

I still am thinking of a different wheel setup, but I'd really like to stick with some sort of radial. I'm liking the idea of having a set of 18's for the street with some NT05R's on the back. And then a set of 15's or 16's just in the rear, with some taller side wall MT drag radials or something for track and street play. Just trying to find that perfect wheel combo for me is tough.


Also as for how I launch it. I don't have a 2 step yet. So what I did was basically rev it up (forget where but maybe 4k). Then when I got the green I just floored it, immediately start letting off the clutch just enough so I can feel it start to engage (preload drivetrain basically) then just dumped it.

motorheaddown

The soft suspension is required to transfer weight to the rear wheels; this helps plant the car for better traction.

I forgot to mention I use two-step AND anti-lag to spool the turbo. My guess is your car falls on its face after you dump the clutch. If so, it's because the turbo isn't making any power by simply revving the motor. Therefore, the driveline doesn't have the power to carry the weight of the car when the load is applied by the clutch. You'll have to make boost at the line THEN dump the clutch to improve your 60' times.

Thanks,
-scott