Rupes

I'm thinking about putting some 245/40/18 on the rear. I'm wondering though if this will make my tire come out of the wheelwell too much. I'm aware people have posted that they can put 275's and such on it...so I'm not asking if it will work (as I know it will) but rather, I'm asking if it would LOOK right. Also, would I get tire to fender contact on hard cornering? would you replace the fronts to 245/40/18 because the car runs on the same size front and rear tires? I'd rather just replace the rears, as I don't care about having large tires up front. Thanks (Sorry for all the questions, I'm a tire newbie).

-Rupes

PUR NRG

Why exactly do you think you might get tire to fender contact in the rear during hard cornering?
________
EmiliaHot

Rupes

Well on my fathers 330 BMW, I put 265's on the rear and its been such a big problem, that I had to take them off and put back the 245's. On banked turns and such, the back will roll into the fender as well as the front.

-Rupes

SilverBullitt

I have 245/40zr18 on all stock 4 rims and A1. Not problem at all.

Gord96BRG

Do you care about balanced handling? The stock RX-8 suspension setup is designed around having the same size tires front and rear. Put wider tires on the rear only, and you will introduce more understeer to a car that understeers slightly already.

I'd highly recommend keeping the same size tires all around, unless you are compensating for the tire change with other suspension modifications designed for staggered tire sizes.

Regards,
Gordon

WTF no turbo

Get off the balanced handling thing already..christ easy pressure fix and by the looks of Huff whooping a vette and m3 in the turns doesnt seem no worse for wear.You made a comment on indy and sprint cars with wider rubber in rear cause the mid engine?Ok so more weight on rear justifies more rubber in rear?Seems like the other way around to me.This car is slow as hell at least lemme make it look fast.

Gord96BRG

Go ahead, knock yourself out - make it look fast. If you don't care that it will actually be slower, then I certainly don't care! :D

Regards,
Gordon

Omicron

I have 245/40-18s on all four corners, and have no clearance issues - even with the car lowered via Tein H-Tech springs. Info here.

cortc

The difference between the 225 and the 245 can be compensated for by a little more pressure in the back... The car will handle fine, as far as the fitment goes no problem; plenty of room...

Guys, until you have actually driven an RX8 with a staggered setup and experimented with tire pressures, hold off on the judgments. Every car takes changes in tire/wheel sizes and make differently; so don't expect the exact same results with the RX8... And if it did understeer slightly, nothing that changing sway bar bushings or rear sway-bar couldn’t fix... (However with the 8 a mild stagger is not a problem, trust me I know...)

Sputnik

Why would someone put on wider tires in the rear, only to adjust suspension and tire pressures to bring the balance back up front? You neutralize any gain you may have gotten, and you've used up a bit of the adjustment in the suspension, which gives you little or no room to tweak for conditions, track design, or surface.

---jps

cortc

Because when you make some additions to the power you will have more grip in the rear... When I get done with my upgrades my goal will be about 280-320hp at the rear... To increase the overall grip I suggest going to a 235 up front, it wont change the feel much but will increase the limits a bit...

F.Y.I I will be at the show this weekend at Homestead, this time I will be in the showoff competition (Will post picks on Monday), next time on the track (Once I finish with the brakes and the engine mods)...

cortc

By the way, even with the 265s in the rear and just a few mods I can get the rear out any time I want, so she has enough power even now to play with the tail...

Kel Rx8

"your my boy blue"
nicely put dave
wheres the pixs ?

Sputnik

But as soon as you tinker with air pressures and other suspension adjustments to get grip back towards the front, you've adjusted out your increased grip in the rear, and you're back where you started (as far as handling is concerned). You've gained nothing.

Meanwhile, you've changed the grip front to rear so that your braking bias is messed up, and now the front and rear tires react differently under transition, making the handling less consistent, harder to control, and thus harder to keep at the limits.

---jps

RotorManiac

Sputnik, you are putting here some very interesting information... but I'm no expert, so you got me confussed!
Actually, I agree with cortc but what you say... seems right too! Wish I knew who is right...

By the way, what are the "sway bar bushings" cortc is reffering to?

cortc

Sputnik: You are chasing your tail here and over analyzing the whole thing, that's not how it works... First you go from 225 f/r to 235/265 front rear... Then you balance the car out using the methods described before... You now have a car that has higher limits and will handle more power... The affect on braking is going to be a positive one and the very slight change to the bias will be picked up by the electronic brake force distribution... And it is minimul...

Sputnik

I respectfully disagree. Tuning a suspension is a balancing act, and there are alot more trade-offs than you are considering. If those trade-offs are something that a person is willing to give up, then so be it. For alot of people driving on the street with street cars, most of those trade-offs are admittedly moot anyway. But for someone interested in keeping the nuetral handling of an RX8, it is something to consider. My point is, if you've truly adjusted your suspension and tire pressures so that the car is once again balanced at the limits, then you do NOT have more rear grip in the corners, and you will not handle more power in the corner (or while exiting it). Where handling is concerned, you can either have a neutrally balanced car, or one that has more grip in the rear for powering out of corners. You can't have both. This goes for whether you have staggered wheels or not.

Quote:

...The affect on braking is going to be a positive one and the very slight change to the bias will be picked up by the electronic brake force distribution...

The factory EBFD is designed and calibrated for equal tire width front and rear. What makes you say that it is dynamic enough to handle the different grip levels of a staggered tire setup? Even on a 50/50 balanced car, front tires handle more of the braking effort, and a balanced 265/265 setup is going to significantly outbrake a 235/265 setup, no matter how well the EBFD is working. Even a 245/245 setup should outbrake a 235/265 setup (all else being equal, of course).

---jps