Sean F

replied

FredC

mmm. The Crossman going for 18s????

flatsics

I knew my post would get you guys thinking.

I bought a set of rear 18's last year from CCW.
I ran 17's on the front and 18's on the rear for some of the races.
I initially did it to try the new Hoosier 255/35/18 on the rear.
I found that I did not like how short the sidewall was.
I moved to a 275/35/18 and really liked that in the rear as it is wider and shorter than the 275/40/17.
I still really like the 17's and I am not totally sold on the 18's.
I want to get some front 18's to go with my rear 18's.

If I ran stock class and had stock brakes, I would probably try out 15's
and see if they were actually faster on my car.
I don't know much but...
What I do know is, that I am faster in the corners than the cars that I have run with the 15's. YMMV.

FredC

You are faster than most everywhere Doug

John H

I was thinking at Daytona, maybe run 15's on the driver side and 18's on the passenger side. (or visa versa depending on the track of course).

flatsics

John, I think you might be on to something.
Or is that smoking something?

John H

No comment.

Sean F

The plot thickens. Doug, I have a hypothesis that not only are the 15's faster coming out of corners than the 18's but the 17's are faster than the 18's coming out as well (not sure about mid-corner speed, just exit). I don't have any data to support this, but lots of anecdotal evidence having paid close attention to this in the last year. I've also seen parts of certain tracks where the 18's are stronger than 15's or 17's as well.

Doug - I'll get back to you on your PM.

John H

In all seriousness, what does a 15" wheel and tire weigh compared to an 18" wheel and tire? Anyone know? Like a 15 Fuch v. 18 CCW both with Hoosiers?

flatsics

275/35/15 21lbs
275/35/18 23lbs

15 vs. 18 inch wheels
15's are 5-8 lbs lighter per wheel

Sean F

the dirt track wheels that guys are running are even lighter if my information is correct

flatsics

This is from the Buckley Racing website:
http://buckley-racing.com/products.html
Advantages to the smaller diameter wheels:

* Lower center of gravity by approximately 1".
* Lower unsprung weight by 40 lbs compared to CCW 17" wheels.
* Lower final drive ratio by approximately 6%.
* Low cost - $1840 per set
* Allows fitment of 275/35/15 tires on the rear

10 lbs lighter total per wheel and tire.
That is comparing a CCW 17" to a Buckley 15"
There are lighter 17" wheels than CCW
Not all 15" wheels are as light as Buckley's

Sean F

Right, so versus an 18" it's an even greater weight savings.

Sean F

BTW, I believe there are other options out there.

sig_a

---------------------------------
For whatever it's worth --

15" 7"- 8" width Fuchs original to 1987 Targa mounted with four 225/45 Nitto NT01

Front 37 pounds x 2 = 74
Rear 39 pounds x 2 = 78
Tota:l 152 pounds (new tires)

17" 8" width Fikse Mag style mounted with two 215/45 Nitto NT01
17" 9" width Fikse Mag style mounted with two 255/40 Nitto NT01

Front 42 pounds x 2 = 84
Rear 46 pounds x 2 = 92**
Total: 176 pounds

**My 2 rear 17" NT01 tread is 2/32nds, which I guess is at least 1 pound per tire lighter than new at 6/32nds.

In my very limited experience at Putnam 15's were much faster than 17" with stock 3.2 runnning about 500 rpm deeper into the the power (5900 max) and torque (5800 max) curve. Center of gravity also is about 1" lower 15" vs 17". Long front straight is finished in 5th to 3rd. Shift to 4th briefly between turn four and five. All the rest in 3rd gear including 7. Take this all with a big grain of salt, but the overall (power, balance, braking) improvement is very impressive.