Suspesion setup with radial slicks "help"
 

Hello everyone, My name is Jon and I am new to this forum. Im reaching out looking for some advise from fellow racers. Although my car ( 1965 GTO ) is not a legal Stocker, Ive built it very similar in terms of suspension, looks, tire size and such.

So since I finished this new build last year I have had some struggles with getting the car to hook consistently. When it hooks up it will 60 in the 1.37 rang, 2500 rpm footbrake. The car previously was setup to run a DOT drag radial and I had success with it, 1.40 with 100hp less. I was running no-hop bars and soft rebound to really hit the tires ( M/T PBR ) hard and 90/10 shocks up front.Fast forward to now, In the rear now I am running all tubular arms with spherical joints in stock locations, Viking DA shocks, BRM antiroll bar, UMI lower relocation brackets. Front has Viking coilovers with double adjustable shocks as well and stock control arms.
Tires are Goodyear 5202 30x9 Radial Slicks which have a much much softer sidewall than the M/T PBR.

So im really struggling with how to setup the suspesion with these tires. Do I setup as if they were a bias slick, or do I setup as if they are a Drag Radial? I have about 165% antisquat currently. When the car hooks all is well, when it dont hook though my sympoms are it hooks then comes unglued a couple feet out then it rattles the tires. Ive tried up and down on tire pressure and played with shock settings a little bit too. Is it possible im hitting this radial slick too hard and causing it to bounce? Should I keep hitting it hard and tighten compression more? Please help...https://www.facebook.com/photo.php?f...7520000&type=3

Re: Suspesion setup with radial slicks "help"
 

Sounds like yor hitting the tires too hard. I would loosen the rebound up front and tighten the compression in the rear. Probably about 18 lbs or more in the slicks. Because you changed a bunch in the rear, doube check that there is no suspension bind when it travels. Hope this helps.

Re: Suspesion setup with radial slicks "help"
 

before we talk about shock settings, what do you have for pinion angle and preload? I will also tell you that coilovers with the stock arms is a mistake.

3880 lbs. 59%F/41%R weight bias launched off the footbrake on Hoosier 30x10.5 radial slicks. .Stock A arms, coil springs and Koni shocks up front.

https://www.youtube.com/watch?v=rbKYio6OvKM

Re: Suspesion setup with radial slicks "help"
 

Pinion angle is 1.5*
Zero preload wiwth me in car.

3500lbs with 53F 47R bias, why is the stock arms a issue with coilovers?

Re: Suspesion setup with radial slicks "help"
 

No binding as Ive checked that, thanks for the advise.

Re: Suspesion setup with radial slicks "help"
 

Typically limits front end travel which these cars need all they can get. The car needs to be put on 4 corner scales to dial in the preload.

Re: Suspesion setup with radial slicks "help"
 

Got it! I have stock limiters removed and it does have decent travel.

https://www.youtube.com/watch?v=q9mqQJX4Ofw

Re: Suspesion setup with radial slicks "help"
 

video

https://www.youtube.com/watch?v=q9mqQJX4Ofw

Re: Suspesion setup with radial slicks "help"
 

not nearly enough, I had the stock limiters installed.

Re: Suspesion setup with radial slicks "help"
 

Looks to me like the front is not loose enough. the front settles back too soon.

Re: Suspesion setup with radial slicks "help"
 

In my experience, and as Ed said, because of the front weight, OE-type springs would be better. Landrum has a wide selection of drag-front sprigs to fit the factory location. The front needs as much travel as possible, and the static front height should be slightly lower than stock. One no-cost mod is to relocate the front upper ball joints to a new location, on the bottom of the control arm, not the top. Doing this will at 1/2" + to the front travel. Also, the front system should be free and move smoothly.

Re: Suspesion setup with radial slicks "help"
 

I agree that more travel will help you.

My Chevelle has 6+" of travel with stock suspension in the front. Stock type coils and shocks.

Get as much travel and control it with a quality shock.

Tubular A arms look cool but not needed in my opinion. They actually sometimes weigh more!

For the rear, pick your poison. It depends on SLR, slicks,...

I actually had good luck with traction action bars til they bent all the factory mounts.

Have fun and good luck

Re: Suspesion setup with radial slicks "help"
 

Woodfin...KNOWS!

Re: Suspesion setup with radial slicks "help"
 

Tire pressure gauges go bad. Check your gauge against others to verify its accuracy. Not saying thats your problem, but its an easy fix if it is your problem. I recently found out mine was 6 lbs off causing lots of traction problems since the beginning of the year.

Re: Suspesion setup with radial slicks "help"
 

If you find a tire gauge that matches yours, it’s luck! Tire gauge readings vary greatly especially that most are Chinese junk! There is no wrong gauge, all that matters is what your gauge reads. Never borrow someone’s gauge to set your pressure.

Re: Suspesion setup with radial slicks "help"
 

The launch in the video above looks pretty darn good. Not sure where you get the 165% antisquat number... If you are watching "Kevins youtube videos on antisquat", they are only good for one thing...entertainment. I watched your video multiple times in slomo and it isnt hitting the tire extremely hard. Alot of variability comes in track temp/track prep, as well as the age of your tires. Replace the front springs as mentioned and put a good dbl adj front shock on it. IMO, you'll find as much hook controlling the front as messing with a stock 4 bar rear setup. Some people will say pinion angle doesnt matter..... however, very few have stated what they have. ;).