-RX8-

i'm juggling a few different wheel/tire combos in my head, and was wondering. just how much tire is too much?

not really too concerned about drag racing, straight line racing, etc... im not going to have enough power to spin 275's/285's etc..

so for cornering/autox/track/daily driving on a relatively light bolt on rx8 what would be a good compromise tire size?

255/40/17
275/40/17
275/35/18
285/35/18

are the sizes i'm juggling.

thanks in advance, and i figured this would be better here than in the competition forum seeing as how im only seeking street tires and the car's main duty is daily driving.

swoope

iTrader: (5)

the stock 225 45 18 is more than needed.. for looks.. 245 40 18 is much more zesty..

but does not change a thing..

beers

dschreiner

It all depends on what size wheel and offset you want on your car. you can pull a 9.5" wheel +45 offset with a 275 easy without any fender modification. great performance for the least aggressive fitment. if you have the right rim im sure you could throw a 300 series tire on the rear of an 8 with fender mod and camber setup. look into the "aggressive fitment thread" and "will it fit thread"

-RX8-

well i didnt list wheel sizes because i have certain fitments in mind. the sizes depend on the tires too. so i'm deciding a tire size before finalizing wheel size.

swoope

iTrader: (5)

sorry,

how does putting on 275s enhance preformance???? sometimes less is more..

as does switching to 17 inch wheels.. 17 inch wheesl are great if you want to save money on track tires..

beers

Ross_Dawg

iTrader: (2)

yes and no, you do save money on what you can find for 17's. There is a much better selection for 18's (were talking rcomps i believe)

OP, 275's for a near stock 8 is plenty. You can fit 18x9.5 +40 or higher with 275/35/18 with no worries.

-RX8-

yea i'm mostly leaning on a 255/40/17 on a 17x9.5 +32 or +38 for quite a few reasons.

1. reduced rotational mass
2. bulk of mass is closer to the hub
3. reduced overall diameter (shorter gearing)
4. cheaper tires and wheels
5. lower center of gravity

but then there's the part of me that wants more rubber just to have it but i know logically i'll have no good use for a 285.

the next size i'm considering is a 18x10+38 with a 275/35/18 tire

Ross_Dawg

iTrader: (2)

The 275's and up are better suited for a dedicated track setup. You dont need anywhere near that for the street. All you'd be doing is wasting rubber to and from the track.

I think your choice in the 17's is a good one. 17x9.5 +32 with 255/40 would look really good; you'd have to roll your fenders but I think it would give your car a great stance.

-RX8-

Thanks for your help that's what I was basically thinking just needed a 2nd opinion. Don't mind rolling the fenders either, was actually expecting to do it with whatever fitment I ended up going with. They're all pretty agressive

maxxdamigz

iTrader: (1)

I found on 275s/stock suspension street use, I feel a change in the lateral grip of the car, but I'm not sure I would call it an improvement persay. Yes, they grip like hell, but the car rolls more. I'll have to rework my suspension to stiffen it back out to really consider it an improvement. However, the tires will let you get the most out of your brakes which is probably great on a track. On the street, it got me rear ended once.

Huey52

iTrader: (2)

245 - 255x40 is just right for a street machine imho.

265 - 275 (or greater) x 35 is too much imho.

TopGear8

iTrader: (3)

^So going faster is...Too much?

275's will be faster than 255's...

RIWWP

iTrader: (2)

More width does mean more lateral grip, but when you get above 245 or so with 18" wheels, you start losing time in Auto-X due to the more effort to rotate, and stop rotating, the higher mass, more than you gain by higher corner speeds. Road Courses are very course dependant (from what I have heard), although more time spent accelerating vs auto-x can mean weight plays an even bigger part.

It's been proven by quite a few people that going up in weight reduces lap times. I know this sounds obvious, but it is a fundamental point you are skipping here.


255s and 275s are both faster than 225 stocks IF it is a lighter total package. IF you are comparing same wheels to 245 vs 255 vs 275, the 245s will probably be the fastest, as they are the lightest without being too short on grip. Go thinner and you gain time from faster acceleration and better braking, but lose more time from less grip. Go thicker and you gain time from better corner speeds, but lose more from slower acceleration and more mass to slow down. There is a sweet spot for every single track, generally based on how much time you spend turning.



I'm not saying don't go 275, I'm saying think it through completely.

Mawnee

I have 255/40/18 out back and I think its a perfect fit both in looks and performance.

TopGear8

iTrader: (3)

So looking at the results from the Solo National Championships this year. All the guys in STX who were running 265's and 255's, should have ran 245's instead because they would have been faster...

Don't think so.

In AutoX, wider is faster.

RIWWP

iTrader: (2)

I'll repeat my final line: "I'm saying think it through completely"


Why don't you just fit a 600mm wide tire back there?


I'm arguing against your universal statement being universally applied, not against circumstances that can certainly overrule it I agree that there are plenty of ways that wide is faster, but you can't apply it universally, because there are certainly circumstances in which wider IS NOT faster....

And that is before even getting into the fact that "wider" as a word implies that there is a comparison being made, and we aren't even defining what it is being compared against, because there is a point at which "wider" is simply too wide and isn't faster.

Gr8Bullet

iTrader: (5)

till you can fit anymore in her.....

but i would fit max of 255 all around in mine.

-RX8-

If the car was going to see more track time i'd definately be going wider. But given the mostly daily driven nature i think 255's would be good for me

c0ldf1ame

iTrader: (5)

i like my 245s

rodjonathan

iTrader: (6)

any pics of the 275s and 265s just wondering how they look from behind

Vlaze

iTrader: (14)

You're using too much rubber when you can't feel anything.





Aw crap, misleading title...

Anijo

I swear we had another thread on this exact same topic recently...

Anyways, the way that you're asking this question implies that you haven't done much in the way of AutoX'ing or track days. If that's the case, Swoope has the right idea. Stick with the stock size or move down to 17's because you want to save money and weight. Just be aware that changing wheel size usually moves you around between classes when it comes to anything competitive (i.e. autocrossing).

My advice is stick on the stock size but get some wheels that look good and are light (18x8 RPF1's maybe?). Once you've done a lot of racing in one form or another, you'll be in a good place to judge when you're running out of grip in which case you can start talking about alternate sizes.

I went straight to 17x9's running 245/45/17's and running in STX in autocross. It was a mistake, I should've stuck in stock class. I know several people who bought 18x9.5's for looks and are now screwed in massively underprepared STU cars if they ever want to talk about actually competing in AutoX... but the bigger size looks better. What it comes down to is you need to decide how important the looks are to you vs. learning to go fast vs. cost of the tires.

I won't fault you (but others will) if you decide you care more about looks and get some 18x9.5's 28lbs rims and run 275/35 tires because it looks good. I'll also always be faster than you, not because of the equipment but because my goal is to go faster and not to look good (within reason, I still won't put ugly rims on my car )

silverbullet05

iTrader: (7)

RJ: I've got 265's on the rears. check my profile for pics.

imput1234

iTrader: (6)

The car doesn't even have 200 wheel, other than autox do you really need 10" of rubber. You be the judge.

GeorgeH

iTrader: (2)

To my knowledge, nobody has done a 17 vs. 18 comparison for autocross, or, more specifcally, wider & heavier vs. narrower & lighter. Historically, most nationally competitive auotcross drivers put on as much rubber as they can within the rules; weight of tires be dammed (although light wheels are a given).

I ran 255/40-17s on 17x9 wheels last year in STX and trophied at nats. Rules allow up to a 9" rim, and 265 tires. Problem is, nobody makes a 265-17 that works, so you have to go to a 265/35-18, which is slightly taller, wider, and heavier (including the wheels) than the 17" setup.

I was beat by Jason with his 18x9s running 265s, but theres much more than tire choice in that equation (although I was within 1/2 second of Jason on the second day, heh-heh). I am facing this decision this year - stick with the 17s or go to the 18s? Have not made my mind up yet.

The point is, wider rubber, when properly supported by the rim, will usually result in higher cornering speeds on a well setup car. This is within reasonable limits (i.e. we are not talking about putting 600 mm of tire on). Will the added weight & aerodynamic drag (and possibly gearing) make the car slower overall? That is track/situation dependent.

I will say that the 17x9 wheels with 255/40 tires makes for a smokin' fun street tire setup. You will feel the added acceleration & grip over stock, although to properly take advantage of the added grip potential you should add some roll stiffness to the car, both transitional (shocks) and steady state (bars/springs). Cheap and fast - hard to argue with that. Only problem is that if you have lowered the car, the added drop from the 17" setup can pose some ground clearance issues.