PUR NRG

Replaced the stock 18x8 wheels with SSR Competition 18x8.5. According to Tire Rack the SSRs weigh 16.8 lbs each. After doing the swap I weighed the stock wheels sans pressure sensor. According to my bathroom scale they weight approximately 21.8 lbs, for a savings of 5 lbs per wheel.

On the OEM wheels, 245/40-18 tires fit on all four wheels with no rubbing problems whatsoever. Once the current set wears out I plan to try 265/35-18 tires all around.
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Coach purses

davefzr

I think the SSR's weigh less than that.. it's weird.. the 7.5 to 8 is .4 pounds.. but the 8 to 8.5 is more than a pound??

Not sure if that is right.. you should have weighed the SSR wheel.... I think they may have switched it with the 9 wheel...

btw.. I am doing this same wheel this week.. what tire did you go with?

I am racking my brain about it....

I really want to go with the T1S.. 245/40/18

takahashi

are you sure about the size?

I know it is much of the personal preference but I think whether it could create more understeer.

So may I suggest to go either 235/40-18 for front and 265/35-18 rear

PUR NRG

I've used S-02 and S-03 tires in the past and like them both. The S-02 has stiffer sidewalls (always a plus) but gets noisy after a few thousand miles. Currently have S-02 245/40's on all four wheels and plan to try S-02 265/35s when these wear out.

I prefer the same size wheels/tires on all four wheels for two reasons: I autocross so balanced wheels front/rear is good, and I can rotate tires. Given the former the latter becomes that much more important.
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Asiancougar

Gord96BRG

He's using the same size tires front and rear. To go with wider tires on the rear as YOU suggest will create more understeer. For balanced handling, you really need to keep the same size front/rear.

Regards,
Gordon

takahashi

So you reckon 245/40-18 is the better choice?

Why 265/35-18?

I checked the Volks racing wheel site again.. I am after the volks racing CE28 N for the future and they suggest 225/40-18 front and 245/40-18 rear with different wheel as well

Link and scroll down to RX-8
http://www.rayswheels.co.jp/cgi-bin/...8N&inchIndex=4

I am so confused... I guess we can order 4 rear ones and feed them with 245/40-18. But would that defeat the inventors initial intent???

as ever.
Taka

PUR NRG

General rule of thumb: Wider tire == more grip. From that you can extrapolate that a wider tire in rear compared to front means more understeer. Volks (and others including JIC) put wider tires in rear because that's what people (ricers) want and they're in the business of selling.

If I could stick a 18x9" wheel (and 265/35 or even 275) tires all around I would have done it--but sadly I couldn't find one that was performance oriented. So I "settled" for SSR Competition wheels.
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perfect **** Webcam

davefzr

You couldnt find a tire that you wanted in that size?

murix

In a review of the JIC RX-8, while it did manage over 1.0g on the skidpad, it was apparantly very prone to understeer.

Wide tires in the rear are great if you have lots of torque to control. Last I checked that is not a problem for us.

takahashi

ic.... I thoroughly understand your point but I still worry about wider tire...

Will 265 tire hurt acceleration being too much rubber on the ground? The rolling resistance must be huge.

I guess the wider the better but I am sure there must be a point that strike the best balance between grip and rolling resistance...

I am still seeking the best tire size for the RX-8 .... yet to see one/people that convince me.... Fujita engineering said in the HyperRev magazine stated that 255/35-18 is the best. It is the best choice for me at present.
I agree with same size for 4 tires --- you can rotate and balance the car.

For the info of the Japan show cars: (Rice? some of these yes... )
Ings+1 F:235/35-19 R:245/35-19
Blitz: F&R: 235/40-18
Kei Office (the Drift King's): F&R:235/40-18
Fujita Engineering: F&R: 255/35-18
Knight sports: F&R: 245/40-18
Revolution: F&R: 255/35-18
LEG Motor: F&R:245/40-18
SAN-AI: F&R:225/45-18
Burnout: F:225/40-18 R:235/40-18
Mineblue: F235/40-18 R265/40-18
Veilside: F245/35-19 R275/30-18

PUR NRG

At this point tire width is pure guesswork. I'm going by what I know can fit and only after trying them will I know if the pros outweigh the cons. Trial and error. For autocross I think grip is more important than acceleration.
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Honda Gyro History

RotorManiac

personally i agree with taka: 265 for the front is more rolling resistance than grip. what about steering? will it not suck too?

i even heard people claiming 245 is too much for the front tires...

takahashi

Someone test and pull out the best thread of all time...

There isn't any thread as useful then tyre testing for specificly for the RX-8...

murix

PUR NRG just made a very important point. Tire size is dependent on what you are looking for. A good tire for autocross might not be the best option for the street or for a road track and at this point the car is too new to have enough empirical data to say what does and does not work.

I am going with the 245/40 route to see how that does. My next track day is at Thunderhill on July 20. I have already been on the track with the stock setup and will be going back with my RB setup and new tires.

takahashi

THat is the spirit... wish I have more money to practice that as well...

I went to track in April and will be going again on the same track in August.

the changes are only the MazdaSpeed strut, sway, brake and the exhaust, ... and yes when I burn the stock set of tyres then I will be looking at new tyres but I can't afford a AUD$2000 mistake that is all

Sputnik

Some things to consider when looking at a wider wheel/tire package:

-Cost (of course)

-Availability of tires for the size (this is actually a bigger consideration when you are talking about a staggered setup. I owned an MR2 that required a staggered setup, and not only do you have to find a tire that you want in one size, but one that comes in both sizes that you need).

-Some rolling resistance (but that's not going to have a big effect by itself).

-Wheel/tire weight (which like we said before, affects both rotational and unsprung weight)

-A wider tire increases the propensity of a tire to hyrdoplane in wet conditions

-Steering feel in regards to effort required steer (might not be an issue, but may prematurely wear out some power steering systems).

-Depending on how wide you are going, and the car you are putting the wheels/tires on, you have to consider clearance (to avoid rubbing and suspension travel issues). To avoid rubbing and the like, people have to adjust wheel offsets. The offset is a big part of setting up a suspension's geometry, and modifying it does negatively affect the suspension's performance and tuning. And in the front suspension, it also affects the steering response and feedback. That light, nimble feel with good communication through the steering wheel will be dampened, and the car will not feel as solid and precise as before. Those of us with Miatas and the uncommon 45 offset have found out the hard way that when you are talking about a well tuned and refined suspension, a proper offset makes a difference.

---jps

PUR NRG

I can't speak to rolling resistance on 265 tires since I don't have them yet. But tpryor autocrosses his RX-8 on 275 hoosier slicks front and back. If any tire is going to have rolling resistance I'd think that would be it. So far it seems to be working for him.

murix, I'm not sure if track and autocross tire requirements are really that different--except autocross tires need the grip at lower temps. Otherwise I think you're looking for the same things in both.
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Expert Insurance

MrWigggles

As a point of reference I run AVS db2's front and rear

I have 245/40-18 in front and 275/35-18 in rear.

In general I think the hanling is better but I don't detect any understeer problems. I don't autocross but I do take a lot of turns very fast on my way to work and back. There are some turns that I used take in 85 MPH that feel better now at 90MPH.

It could be the tires and maybe 245/40 all the way around would be about the same.

I just don't think that the difference is all that big either way. Cortc autocrosses with his 235 - 265 combo with good performance on his 19 inch wheels.

One reason I went with 245/40 and 275/35 is because those size are closests to the 225/45 OEM tire. No 235 or 265 tire will be as close and if you go 235/40 you will increase the speedos inaccuracy from it currently reading of ~2% too high to ~4%.

One last thing, if you use your bathroom scale to weigh wheels, it would probably give better results if you weighed yourself holding the wheel and then subtract the weight of yourself alone. The bathroom scale might not measure small weights as accurately as heavier objects.

-Mr. Wigggles

Ophitoxaemia

for autocross you want the widest tires you can get to operating temperature. the modern autocross tires require little heat so you can go wide. 275 is not at all too wide, although a 9 inch rim is a just a little small for it.

rolling resistance isnt as much of a factor as the additional weight.

on the big track things are a little different. for street, 225 is fine.

james