Switched to 295/55/15 DR's now lack of traction

[05yellowgt]

I go out to the track for the first time this year. The only thing I have changed since last year is that I replaced my 15x9 Weld XP wheels with 275/50/15 MT DR's with Racestar 15x10 wheels with 295/55/15 MT DR's. I barely had 200 miles on the tires since I put them on back in June. Nomatter what I did today I couldn't get these tires to hook. Everything from a 2800rpm launch on up with result in spin through all of 1st, all of 2nd and sometimes into 3rd. I was literally spinning through the 330' mark through nearly every pass. With the old wheels/tires I had a best of 1.62 60' and today I the best I could do was a 1.89 by basically leaving off idle. That run was a failure due a coupler coming lose at the top of 2nd.

I know the track prep wasn't very good today and I need more seat time to figure out what pressure and launch rpm's work best. Has anyone had good results from the MT 295/55/15?

 

[GrnBullitt08]

Why did you swtich from the 15x9s to the 15x10s? 1.62 is a damn good 60' time.

What tire pressure where you running at?

And Im sure the DA wasnt too friendly today as well.

 

[05yellowgt]

I tried 15, 14, then 13.5 PSI. A 1.62 60' time would be pretty good for an n/a car, but I'm pushing 700rwhp, should be able to get into the 1.40's or better on DR's with the right suspension setup. Guess I should mention that as well. Right now I'm on stock front and rear struts and springs with front swaybar delete, Steeda adjustable upper, lowers with relocation brackets in the top hole, and BMR anti-rollbar.

 

[GrnBullitt08]

I dont know if your gonna be cutting 1.40s on a Drag Radial....maybe a drag slick.

You prob need to ditch those front struts for coilovers and do an adjustable shock in the rear.

 

[05yellowgt]

It should be doable with a well setup car. An auto would make it much much easier though. I agree some adjust able stuts/shocks should be added.

 

[GrnBullitt08]

Yeah the power numbers your pushing and how hard that car probably launches the stock components need to go.

Track conditions could of been killing ya. Were you running the same power with your old wheel and tire setup, or have you upped it since.

 

[05yellowgt]

I don't know for sure, but at least today I added 3* of timing because I was only seeing 20 where I was tuned at 23*. That makes almost a 50rwhp increase on my setup. Otherwise the only change from last year was the new wheels/tires.

 

[GrnBullitt08]

Lol well a 50rwhp gain can reduce traction...

 

[dysan]

What kind of ends do your control arms have? Are they poly by chance? I've blown a few of my poly bushings out and when then are cracked/split that kills my traction. Also, those pressures seem quite low for drag radials. I've found with my M&H DR's that 17 psi is the best for me.

Also, have you changed out the crappy rubber bushing that's on top of the diff in the rear to a poly or solid one? That stock bushing took a crap on me a few weeks ago and that wreaked all kind of havoc on consistency.

 

[PNR Welding]

As Dysan said, tire pressure is probably too low. Not sure if it contributed to the problem or not, but I have cut 1.39 60' with the blower on 325-50-15s at 17psi. Not much bigger of a tire than you have, just a little wider.

 

[05yellowgt]

I'll try some higher pressure next time. My LCA's do have poly bushings. I'll be sure to check them for wear/cracking. The rubber bushing on the axle housing was replaced as well.

 

[firestang70]

John you are complaining about T&T traction at Tri State??? I'm sorry i mean tri skate. I know my buddy runs that size on his eforce car at 15 psi, run a best of 10.70. No compalints on traction but he is an auto car.

 

[05yellowgt]

Well yeah I guess a HUGE portion may also be Tri-Skate. Guess I could try for a pass or two at Kil-Kare before I got the boot.

 

[08gt4u]

where are you guys buying the bushing intop of the diff from?

 

[dysan]

Here's the one I got....

http://www.spohn.net/shop/2005-2008...ar-Upper-Control-Arm-Housing-Bushing-Kit.html

FYI though, you have to re-use the "clamshell" from the stock bushing and mine would not come out un-damaged so I had to get a new one. It's not expensive though.

 

[08gt4u]

im guessing for the clamshell just go to the dealer an order one correct.

 

[US-1]

Well yeah I guess a HUGE portion may also be Tri-Skate.

Well.......duh.

 

[dysan]

im guessing for the clamshell just go to the dealer an order one correct.

Yup. You can't just get the clamshell though, you would need to order a new bushing and take the clamshell off of it. I don't know exactly what's involved though since I had a local guy do it for me.