Taller drag tires slowed me down AND sped me up??

**budoboy** · 04-09-2009, 01:07 PM

I went from 25.5" M/T Street ET drag radials to 27" MT Street ET biasplys and lost 1-2 1/10ths in the quarter (from 12.00-12.10 to about 12.20) but gained about 1-2 MPH (113-116 to 114-117). Interesting.

It was my first time out on these tires and the traction wasn't great but I got about 6 runs and I believe what I posted above is true (give or take a little). Any thoughts?

Maybe I need to adjust tuning? I was hoping to his 11s but with my ETs went the other direction after this swap (I also got a limited slip rear axle so I have some relearning to do regarding burnout/launch).

**slideway** · 04-09-2009, 01:17 PM

Originally Posted by budoboy

I went from 25.5" M/T Street ET drag radials to 27" MT Street ET biasplys and lost 1-2 1/10ths in the quarter (from 12.00-12.10 to about 12.20) but gained about 1-2 MPH (113-116 to 114-117). Interesting.

It was my first time out on these tires and the traction wasn't great but I got about 6 runs and I believe what I posted above is true (give or take a little). Any thoughts?

Maybe I need to adjust tuning? I was hoping to his 11s but with my ETs went the other direction after this swap (I also got a limited slit rear axle so I have some relearning to do regarding burnout/launch).

Not sure why you thought you were going to lower your E/T with a larger dia. tire. I think if you can hook up with the 25.5 M/T's you'll get in the 11's easier.

**PowerWagon896** · 04-09-2009, 01:19 PM

Originally Posted by budoboy

I went from 25.5" M/T Street ET drag radials to 27" MT Street ET biasplys and lost 1-2 1/10ths in the quarter (from 12.00-12.10 to about 12.20) but gained about 1-2 MPH (113-116 to 114-117). Interesting.

It was my first time out on these tires and the traction wasn't great but I got about 6 runs and I believe what I posted above is true (give or take a little). Any thoughts?

Maybe I need to adjust tuning? I was hoping to his 11s but with my ETs went the other direction after this swap (I also got a limited slit rear axle so I have some relearning to do regarding burnout/launch).

It's really hard to say. If you wern't hooking that could explain both the higher ET & trapspeed.

Spinning, just a little bit, will slow you ET down, that's obvious. The spin can also increase your trap speed because your tires & complete drive train went farther as measured by tire revolutions, but your car only went 1/4 mile in distance. The drive train had more distance to get up to speed so to speak.

It's hard to determine W/O a good hook up. I almost always log longer ET W/higher trap speds when I slip just a bit.

**budoboy** · 04-09-2009, 01:21 PM

Originally Posted by slideway

Not sure why you thought you were going to lower your E/T with a larger dia. tire. I think if you can hook up with the 25.5 M/T's you'll get in the 11's easier.

Didn't think the difference was going to be that great, nominally the bias-plys are supposed to be 26.5 but in reality they measure about 27. Also I was shifting into 4 before crossing the traps with the 25.5" tires and thought I would shave off a little time by staying in 3rd gear with a taller tire. I was also hoping for a better hook with the biasplys vs. radials. Oh yeah, I got them CHEAP too. Just another experiment.

**FloridaRT** · 04-09-2009, 01:22 PM

Taller tires cut down your gear ratio, slows you down and allows the MPH to get higher.

Go back to a shorter tire.

Bob

**budoboy** · 04-09-2009, 01:24 PM

Originally Posted by PowerWagon896

It's really hard to say. If you wern't hooking that could explain both the higher ET & trapspeed.

Spinning, just a little bit, will slow you ET down, that's obvious. The spin can also increase your trap speed because your tires & complete drive train went farther as measured by tire revolutions, but your car only went 1/4 mile in distance. The drive train had more distance to get up to speed so to speak.

It's hard to determine W/O a good hook up. I almost always log longer ET W/higher trap speds when I slip just a bit.

I know what you are saying about not hooking and higher MPH, but I actually was able to pull a 1.82 and a 1.80 finally (which is about what I get with the 25.5" ET street drag radials) and I lost about a 1/10th (at least) and gained about 2-3 MPH. DA was close to 0' so no compaint there. Hopefully with a sticky track I can shave my 60' down with the bias-plys and the LSD I just had installed.

**slideway** · 04-09-2009, 01:40 PM

Originally Posted by budoboy

Didn't think the difference was going to be that great, nominally the bias-plys are supposed to be 26.5 but in reality they measure about 27. Also I was shifting into 4 before crossing the traps with the 25.5" tires and thought I would shave off a little time by staying in 3rd gear with a taller tire. I was also hoping for a better hook with the biasplys vs. radials. Oh yeah, I got them CHEAP too. Just another experiment.

Fair enough, Actually I did the same thing. I went to the M/T 26.5 bias ply's and got no e.t. reduction(well I did get .05 off but shed 200lbs.) So I want to try a set of 25.5 hoosiers or M/T's and think I'll drop a 1/10 or two.

**budoboy** · 04-09-2009, 01:43 PM

Originally Posted by slideway

Fair enough, Actually I did the same thing. I went to the M/T 26.5 bias ply's and got no e.t. reduction(well I did get .05 off but shed 200lbs.) So I want to try a set of 25.5 hoosiers or M/T's and think I'll drop a 1/10 or two.

I'm looking at the hoosiers now. 315/35/17 is supposed to somehow fit the 9" wide rims? 11.5" tread should get me some hook

I think they are nominally 25.6" tall which is who knows how big when actually mounted on a 9" rim.