LS7 BUD

Had mine measured after hearig they aren't 28" tall... Came out exactly how Realcanuck said 27.2" tall mounted on a 17x11 wheel on the car...

PRE-Z06

Going from a 26" tall tire to a 30" tall tire lessens torque multiplication by ~15%, do you not believe that helps it hook?

LSOHOLIC

I'll bite...........yes there is a wheel torque reduction. But we are talking about traction. While the 15% plays a role, the role has a diminishing return with more power you make...aka, wheel torque.

Most of the cars we are talking about have excess wheel torque and the 15% loss in reduction is outweighed by the available traction early in the run.

If this 15% theory held any water we would all be running 24" tires as to "up" the wheel torque. There is an obvious tradeoff going on here......what good is additional wheel torque if we cant put it down ??

Example.........X275 vs OL315
Both classes are over powered and many of the guys run very, very similar combos. Yet the 315 guys have the 275 guys covered by half a second. But the X275 guys have 15% more wheel torque, LOL.....point is, traction is king when your making obscene amounts of power. Put a 315 on a X275 car and it picks up huge amounts because they are able to pour more power to the tire earlier.

The 315 has 94" of rollout and 11.9" of tread width.
The 275 has 87" of rollout and 9.5" of tread width.

The 315 has 7 more inches of rollout.....aka, "virgin" rubber per revolution out of the hole. Which does and always will trump tread width.

I'm a firm believer in run the least amount of tire to get you down the track. But when your pushing the power that some of the guys on here make.......they need the most tire they can fit !!


***EDIT****
Kind of lost sight of what you said Chris, yes the lack of wheel tq helps the traction.............but If you take two cars, one with 315's and the other with 275's but both have an equal "effective" final ratio with the different tires......who puts down more power earlier in the run (we are talking car that make some steam )??
Rhetorical ^^^^LOL

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07blkvette

So which one 315-325-335 on a 17x11?

LSOHOLIC

Those all suck if your makin some decent power and trying to hook on a $hitty surface....if I was stuck with a 17x11, and putting the power down was my main concern I would run a 295/45-17 Mickey Thompson DR or the 325/45-17 M&H DR.

the 315 & 335 are very short (if your talking Hoosier).


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turbotuner20v

My m&h measured around 27.5"

Milan

LSOHOLIC can you explain rollout? I'm 99% sure I am understanding what you are saying but figured it would still be beneficial

LSOHOLIC

Imagine cutting the tire in half and "rolling out" the tread.....as to measure the circumference in a straight line. Rollout is how much rubber (in inches) that is layed down in one revolution.

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Milan

So finding the optimum balance between torque reduction from the higher gearing created and roll out....check

How does tread width factor into that? I seem to recall in physics that width does not play a factor in friction? Too simplified?

My school of thought was that it was always 1) tread compound and 2) amount of sidewall to absorb the weight transfer that made a car hook

DANZGLASS

im running 325/40/18 m&h right now. will be on 345/35/18 mts soon. think ill be better or worse in traction? 840/840 turbo setup. hooks 3rd and up pretty well.

ace32x

some good information in this thread, im limited to 18" wheels to clear my calipers. currently have a set of 335 30 18 hoosier Drs im going to try i can report how they hook up. 900+whp and tq. if not to not going to be searching for a new size tire to run. not trying to get to tall and mess up my gearing either tho so it looks like the M&H's or the MTs are the only options in those sizes

PRE-Z06

I'm not saying tires can't very from their noted technical size, but just to clarify are you measuring the circumference or "rollout" and then dividing by Pi to come up with 27.2"?

PRE-Z06

I know you understand what I'm saying Caleb and for most of the guys who don't have the electronics to control power delivery of the more traction limited "racecars" a bigger tire will help hook on non racetrack surfaces and help the car ultimately be faster as we all know "spinning ain't winning"

Another problem with roll races is they don't have a definitive start/end speed so you want to look at tire heights changing rpm points meaning the shorter tire is not only multiplying more torque, but if both begin at say 60mph the rpms will be higher with the shorter tire putting you higher in the powerband where you naturally make more torque and this could be a reason for spinning. Also if the shorter tire causes you to have to make an extra shift at higher speeds then that could offset the gearing advantage, as in shoes there's not a one size fits all lol

Comparing two different width tires isn't really a fair comparison and definitely can put down more power over coming the loss of torque multiplication from the taller tire as you stated.

My point was just not to handicap the car with the biggest tire available as I agree with you you'll ultimately be fastest on the smallest tire and you need to find that happy balance for the best results since it's not a tire class race...so if you can hook on a 275/50r15 and not running out of gear, then running a 275/60r15 will only make the car slower, agreed?

Weight is another factor as I know you know, but won't go into splitting hairs as that's for those last hundreths

5 Liter Eater

You guys sure are overthinking this.

realcanuk

Proace4

For what it is worth, I run the 335 hoosiers on my car. 900rwhp+ and love them. I talked to Mr. Lancaster(Went 8's on them) down in texas and may step down to a 315 hoosier but remain on hoosiers while on my 18's. They work for me, in my setup.

ajrothm

No sh*t...

Simple:

Height trumps width for traction.... EVERYTIME.....

But if you don't have enough motor/gear to pull the taller tires, you can/probably will slow down....(particularly on the track, I have done this with 850 rwhp)

But in terms of traction only, height = circumference = roll out = tire patch on the ground = TRACTION...

LSOHOLIC

ALWAYS

There's always the alternative....

LSOHOLIC

Did you ask Eric if it was ideal ?? Bet their taking power out early in the run because of the tire......or better yet ask his tuner...James Short, if a better tire would allow a more aggressive tuneup.

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LSOHOLIC

For those stating the obvious..........my impression of the issue or reason for the thread was traction.

Meaning either two things.....
1) $hitty race surface
2) Making enough power where the tire is the weak link and can not keep up.

This does not pertain to flypaper prepped tracks or underpowered setups.