15x8 tire size for track purposes

Buscarlo
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15x8 tire size for track purposes

Postby Buscarlo » Thu Sep 17, 2015 4:03 pm

I already know this question has been asked before, however all the answers I see are people recommending a tire size of 195/50 or 205/50 for a 15x8. I am more of a track guy and dont feel comfortable with those sizes since it would stretch. This is for street-ability and track. My question is, what tire size should I use for a 15x8 with 0 offset without using fender flares? If i need to I can roll and maybe pull the fenders but if i dont have to, that would be preferred.

I was thinking 225/45/15. Does any one know if it will rub at all, either on the fenders or wheel well? Any other size recommendations?

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gotzoom?
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Re: 15x8 tire size for track purposes

Postby gotzoom? » Fri Sep 18, 2015 8:58 am

225's won't fit without some rolling and cutting. If you're close to stock power, you really don't need that much tire anyway. 205 is as much as you can comfortably fit with minimal rolling and cutting. I run 195 width Hankook RS3's and they work pretty well with minimal stretch. I don't think they are as fast as the 225 width, though. Something about the carcass construction on the 195 makes them slower. I think the Bridgestone RE71 in 205 would be the best "street tire" to choose currently.

To make them fit, you'll need to roll the rear fenders, but don't need to flatten them. You will also need to roll the front fenders, and I recommend cutting off the tabs that normally hold the fender liner in place. Under load, if you hit a bump or kerb, the tire may grab a tab, pull it down and the tab will slice the shoulder off the tire. Ask me how I know about this... :roll:

If you haven't bought wheels yet, you might consider going with +12 offset and then you can use 225 width tires with minimal bodywork mods.

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Re: 15x8 tire size for track purposes

Postby d3nso » Fri Sep 18, 2015 11:16 am

205 on a 8" wheel will give you minimal stretch. I've run 195s on mine and the stretch wasn't that bad but for track purpose i would go 205s. Everything wider isn't an option if you don't have 170hp+ at the wheels...

Buscarlo
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Re: 15x8 tire size for track purposes

Postby Buscarlo » Fri Sep 18, 2015 3:30 pm

Thanks guys. I talked to a friend as well and he also runs 205/50 on 15x8 with Kumho ecsta XS for the track. I guess this makes me feel better about going with 205/50. At this point, are there any tire recommendations for 205/50 for street/track? I did look into the RE71 but im so out of date on tires, not sure which is best bang for buck. Also interested in the Dunlop starspec II, Hankook RS3, and/or Toyo R1R. Opinions wanted! :)

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Re: 15x8 tire size for track purposes

Postby d3nso » Fri Sep 18, 2015 4:41 pm

Toyo R1R but be warned mine only lasted 4000km ;) Nankang NS-2R are also pretty good for their price.

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Re: 15x8 tire size for track purposes

Postby Billy_Andrea » Sun Sep 20, 2015 2:03 pm

I use a 195/50/15 R888 on 15x8 Compomotive. Unless I'm trying to I'm not too concerned with breaking traction. I do plan on widening the rears and going to 225 in the future though.

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Re: 15x8 tire size for track purposes

Postby zokustyle » Sun Sep 20, 2015 8:30 pm

Yeah, I think you're really overestimating 4AG power and tire technology.

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Re: 15x8 tire size for track purposes

Postby oldeskewltoy » Wed Sep 23, 2015 7:33 am

Billy_Andrea wrote:I use a 195/50/15 R888 on 15x8 Compomotive. Unless I'm trying to I'm not too concerned with breaking traction. I do plan on widening the rears and going to 225 in the future though.

zokustyle wrote:Yeah, I think you're really overestimating 4AG power and tire technology.


Have you seen Billy's car?


To OP... can you down size your wheels to a 7"??? 195/50/15 in the front is tough to beat. 205/50/15 in rare cases. 195/50/15 is designed around wheel widths ranging from 5.5" to 7", a 195/50/15 on an 8" wheel is stretching (not the best for handling)
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gotzoom?
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Re: 15x8 tire size for track purposes

Postby gotzoom? » Thu Sep 24, 2015 8:16 am

I'll also add that the hub design requires a positive offset wheel to get the suspension geometry right. Running low positive, zero or negative offset wheels increases scrub radius, which is not great for handling. There really is no reason to run stagger wheels or tires on this car. Set it up correctly and give yourself the option to rotate wheels. You'll get more life out of the tires if you rotate. No camber in the rear kills the outside shoulder, so you really want to be able to rotate.

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Re: 15x8 tire size for track purposes

Postby SgtRauksauff » Mon Sep 28, 2015 1:37 pm

darnit. I had a whole thing typed, then hit ctrl-R instead of ctrl-t and wiped it all out. :(

so now the quick summarization without humorous quips:

starting with stock engine and brakes, with 195/60-14 Azenis and Hawk HP-Plus, I could push the car to about 9 tenths at BHF (Blackhawk Farms Raceway) and still stick without any problems. I was nearing 10/10ths, when the previous owner's use of RTV on the headgasket caused the engine to not send anymore oil to the head, and things just turned sour. I'd also run some autoXes on the same tires, and everything was pretty good.

So, I rebuilt an engine, (108whp on a dynojet), and got a kaaz lsd (with WPE 4:778:1 R&P), and carbotech xp10/xp8 front/rear brakes. Turned the 195/60-14's into beautiful smoke-makers. really had to feather the throttle, and could not give 10-tenths without breaking loose.

got some 14x7 -9 rewinds, and some 225/50-14 hoosiers. (on sale cheap, because the R6/A6 had just come out, and they were clearancing their old stock.) I had NRCA's and AGX's on the front, the car was lowered, so i did have to roll the front fenders a bit, and even use 5mm spacers on the front to not rub. But the car stuck. I could actually get 10-tenths out of this car at BHF, took FTD at a couple autoXes, usually first in class, and once even ftd on pax AND raw. Took it to BIR (Brainerd Int'l Raceway in MN) but on some Hankook R-comp slicks of the same size, and was able to get 11-tenths out of it, but the brakes were in need of more.

So, I consult with Bob at Drift Office, and then apply his recommendation: TODA cams (264/256), FPR, and a header. this tuned to 133.0whp on a (Dyno Dynamics eddy-current dyno). I added brake ducts and upgraded from the Carbotechs to some Raybestos ST43 front, and 41 or 42 in the rear (sorry, I can't remember). World of difference in the brakes, and I was starting to find the edge of traction on the 225/50-14's. Around this time, I also got some 255/40-13s on some panasport knockoffs (can't remember if they're rota RB's or older-style rewinds).

I found a few things when running the 225's, and even the 255's, that caused a bit of consternation/frustration at times. Tthe car gassed up with me in it weighed 2495lbs. In short, very tight autoXes, I used the 255s because they were short and helped gearing, and heated up quickly. when the course was wider open and faster, I'd use the 225's, and do alright as well. my biggest problem was that with that much rubber on the ground, it wouldn't heat up in time to make itself super sticky, and an S2K CR would start beating my times.

Granted, he had brand new R6's and I had not bought new rubber in some time. that's my excuse and I'm sticking to it. Then, a bolt holding an NRCA snapped when going through a roundabout, and my car endured structural damage so I haven't raced it since (project is now underway, but that's a different story).

I'm not sure what power and torque you're putting to the ground, but If it's anything like mine (and I think it is, maybe even better) think the HUGE availability of 205/50-15 tires in different compounds and tread patterns might be worth looking into. If you can fit a 225 in there without going crazy with a hammer , I think it's worth it for HPDE/TimeAttack stuff. However, the 225's can get to be pretty heavy tires, and in an autoX might end up slowing your acceleration more than the grip they provide is worth..

but that's the fun of the sport, the whole balancing act...

--sarge


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