Ｑｕｅｓｔｉｏｎ ｆｏｒ Ｔｙｒｅｓ？？？

[Aya]

Hi, I had the TE37 17 x 9 wheels on my GTR, the front is 245/40 and rear is 255/40. Today I went to bob jane to ask about new tyres, they said I can put 235 at the front and 255 and the rear. Just want to know is that safe? I'm not driving the GTR very often, coz I got a daily drive car. But I just want to know the difference between the F:235 R:255 and F:245 R:255. Anyone can help?

Also wanna ask the price with these tyres? THx!!!!

[Oosh]

Everything I've read says that you need to have EXACTLY the same rolling radius at all 4 corners, else your ATESSA system will have a caniption fit, so that means IDENTICAL rims and tyres.

And for the sake of 10mm extra why bother? just go 245 all round.

[leech_]

yea same all round dude get 255's all round i would think. on gts-t's you would put probably 235 front 255 rear though

[NXTIME]

yep, 255's all round is the way to go.

[Aya]

all rite, take 255 all around!!!!

[Sydneykid]

No! No! No! The ATTESSA doesn't care about the WIDTH.

The DIAMETER should be the same, but that is NOT the same as width. So you can have 225/45/17's on the front and 255/40/17's on the rear. The rolling circumference will be the same.

PS; if you had done a search you would have found plenty of posts on why this is the case.

[Beer Baron]

what about the width of the WHEEL?

I'd always understood that the GTR should have equal width (and diameter) wheels and tyres front to rear? That would be pretty cool if you can just use different sized wheels/tyres.

[Sydneykid]

what about the width of the WHEEL?

I'd always understood that the GTR should have equal width (and diameter) wheels and tyres front to rear? That would be pretty cool if you can just use different sized wheels/tyres.

I have driven a GTR over 200k's with the space saver spare on the front, the ATTESSA didn't even know. The torque split looked quite normal to me, I even palyed with the torque splt controller, just for fun.

[Beer Baron]

cool. so it seems wheel/tyre width may not be so important.

Thanks.

[NXTIME]

No, only tyre circumference needs to be the same as the ATTESA works on front to back wheel speed differences. So you can have those 12" wide deep dish wheels on the back, Richard, so long as the tyre circumference is the same.

[Aya]

No!  No!  No!  The ATTESSA doesn't care about the WIDTH.

The DIAMETER should be the same, but that is NOT the same as width.  So you can have 225/45/17's on the front and 255/40/17's on the rear.  The rolling circumference will be the same.

PS; if you had done a search you would have found plenty of posts on why this is the case.

So what that means is I still can get 255/40/17's at the rear with 235/40/17's at the front? Just have to get the width at the same size? is that what u mean?

[Sydneykid]

So what that means is I still can get 255/40/17's at the rear with 235/40/17's at the front? Just have to get the width at the same size? is that what u mean?

Ah no! Perhaps a quick explanation of tyre sizes might help

235 = 235 mm wide

255 = 255 mm wide

40 = 40% of the width (that's the measurement from the outside of the tyre to the rim)

17 = 17 inches, the rim diameter

So 235 X 40% = 94 mm

And 255 X 40% = 102 mm

So they are NOT the same circumference.

If you want 255/40 on the rear (102mm) then you need 235/45 on the front (105mm). Check the alternatives with the tyre shop that you are going to buy your tyres from, they have equivalency charts (so their customers can keep their speedos accurate).

[FATGTS-R]

http://www.miata.net/garage/tirecalc.html

That link is for a tyre size calculator.

Detailed calculations and has come in handy many many times.

[Aya]

Thanks guys, I know what I have to get now.