Who's Running Wider Rear Wheels&tyres On A Gtr?

[Wacky Dee]

what about an R34 GTT ?

[Duncan]

well....I used to run 33 gtst (near enough the same to 34 gtt) with wider rear (265) vs front (235). And it understeered everytime. If I could have fit larger tyres up front I would have.

But it really depends on what you are doing. For your average 200kw+ street gtst you should probably run larger rears....you are not fitting the fronts hard enough on the street to use all their grip, but you will definately use/exceed the grip from the rear if yo ugive it a bootful in first or second.

But on the track with dedicated track tyres you should run the biggest damn front tyres you can. And if you run the same size on the rear that gives you the option to rotate the tyres between front and rear

[crjfly637]

I ran an R32 GTR for 3 years as a daily driver, doing about 30,000km's per year. That included quite a lot of freeway driving and I never saw any issues in the driveline.

I had the same widths you have 9" front with a 235 and 10" rear with 255. It started because they were the tires that came with the rims.

I found the torque split to the front wheels happened a lot faster, making the car much easier to catch when the tail started kicking out. Plus making it better off the line, and just more traction every where. I did get some understeer, but I was replacing 235 all round so it was the same understeer I had before.

I used to have to replace tires once a year - Lack of rubber meant rotation wasn't much use.

The only advice I could get on the subject was all bad as well. "You'll destroy your transfer case" "no one else does it, so it must be bad"

So I'm really interested to hear someone else actually doing it and if there are any real world problems with setting it up this way. Or if it is just technical on paper behaviour and stats on wear rates, because I honestly never had any issues.

That's not to say my case was a fluke and I am totally wrong. Maybe I can be proven wrong, I certainly don't have an axe to grind on the subject and was recently thinking about buying another 32.

[Brezza]

i've noticed when i got my new tyres that the torque split sits higher than it was with the old tyres.

with the old tyres it would sit under 5 on the guage, but now when cruising it sits at around 5-10.

my tyres are Toyo R1R's which are freaking awesome!!

but they do have quite a high sidewall compared to the maxxis i used to have on it.

the measurements are still the same

235/45 R17 front

255/40 R17 rear

i dont think i have much of an understeer issue, the tyres grip really well.

what does the torque split sit at when cruising at a constant speed in a GTR with the same front and rear sizes?

[Sydneykid]

I ran an R32 GTR for 3 years as a daily driver, doing about 30,000km's per year. That included quite a lot of freeway driving and I never saw any issues in the driveline.

As long as the tyre diameter is the same (+ or - 3%) than there shouldn't be any ATTESSA issues, it only has problems with diameter not width.

I had the same widths you have 9" front with a 235 and 10" rear with 255. It started because they were the tires that came with the rims. I found the torque split to the front wheels happened a lot faster, making the car much easier to catch when the tail started kicking out. Plus making it better off the line, and just more traction every where.

ATTESSA doesn't have traction inputs (ie; wheelspin) it has the far superior lateral an longitudinal G force inputs. So the torque distribution is dependant on the G forces generated by added grip of new tyres compared to the lower levels generated by worn out tyres. It has nothing to do with front versus rear width differences.

I did get some understeer, but I was replacing 235 all round so it was the same understeer I had before.

So the rear 255's didn't generate any more grip than the 235's that were there before. Either your wrong about the same amount of understeer or you wasted your money buying the 255's because they had no effect.

I used to have to replace tires once a year - Lack of rubber meant rotation wasn't much use.

You need to review the theory and practise of rotating tyres.

The only advice I could get on the subject was all bad as well. "You'll destroy your transfer case" "no one else does it, so it must be bad"

That's diameter not width.

So I'm really interested to hear someone else actually doing it and if there are any real world problems with setting it up this way. Or if it is just technical on paper behaviour and stats on wear rates, because I honestly never had any issues.

That'll be me. I had to replace a a pair of front tyres (245/45/15) damaged when I hit a concrete depression, the rears survived but the fronts were both destroyed. I had a spare 225/50/16 and I borrowed another 225/50/16 just to get me home. It was fine on twisting roads, turning the steering, but as soon as I hit the freeway and drove in straight lines for more than 100 metres or so the transfer case shudder was unbelievable. So I had to change lanes like a warm up lap just to make it home. The difference in diameter was around 9%. I put a new pair of fronts (245/45/17) on with the worn rears and the diameter difference was 3% and there was no transfer case shudder.

That's not to say my case was a fluke and I am totally wrong. Maybe I can be proven wrong, I certainly don't have an axe to grind on the subject and was recently thinking about buying another 32

As far as transfer case damage in concerned, width = not wrong, but diameter = very wrong.

As far as handling goes, width = wrong

Cheers

Gary

[Sydneykid]

i've noticed when i got my new tyres that the torque split sits higher than it was with the old tyres. with the old tyres it would sit under 5 on the guage, but now when cruising it sits at around 5-10. my tyres are Toyo R1R's which are freaking awesome!!

but they do have quite a high sidewall compared to the maxxis i used to have on it. the measurements are still the same

235/45 R17 front

255/40 R17 rear

i dont think i have much of an understeer issue, the tyres grip really well.

You're not driving it hard enough to feel it or your not sensitive enough to notice it.

what does the torque split sit at when cruising at a constant speed in a GTR with the same front and rear sizes?

R32GTR = Zero

Cheers

Gary

[sam_mull]

I am running 265/35R18 both back and front on my R32GTR. These are on Volk Racing by Rays Engineering Superfine Rims, and running Dunlop LeMans rubber.

They were on the car when I bought it, and are wearing Ok, but are a bit dodgy in the wet.

The rims look good, but along with Koni shocks are a firm ride. This is pretty uncomfortable on the crappy roads that we have to endure on the NSW Central Coast.

My speedo is pretty accurate (320klm/hr) with a measured tolerance of 1-2% using my Tom Tom at a steady speed. This does not correlate with the data from the calculator?

Hey people,

just wanted to start a thread to find out whether there are many people out there running split width rims and tyres on their GTR.

i know people have raised issues about the ATESSA, and rolling diameter of the wheels.

but i am currently running a set of 17's and my front rims are 9in wide and the rear are 10in wide.

my car is a R32 GTR

i got 235/45R17 on the front and 255/40R17 on the rear.

using this link i calculated my rolling radius and circumference to be

http://www.club80-90syncro.co.uk/Syncro_we...0calculator.htm

front circumference 1962mm

rear circumference 1939mm

DIFFERENCE of 23mm

front radius 312mm

read radius 309mm

DIFFERENCE 3mm (which is 6mm in diameter)

i know its not equal, but i am hoping to keep the same size for the front and get a 265/40R17 on the rear, which will make the Circumference 1964mm (Difference of 2mm) and Radius 313mm (Difference of 1mm)

does anyone else favour the added traction on the rear of a GTR??

[Brezza]

i finally bought some Rays 17x9 all round, so now i can finally run all the same width all round.

and enjoy the luxury of changing tyres front to back!

cheers guys for your help.

will let you know how much different the handling feels.

Brezza

[Brezza]

the GTR handles so much better!

i got Toyo R1R's 235/45 R17's all round and the car really holds on around corners, and with the same width up the front as the rear there is less understeer which is great.

now i can really give it to it coming out of a corner.

cheers guys for your advise

[GTR-N1]

It really is great to see someone like you who's taken top-of-line advice from the members here and reaped the benefits of it!

I must say that the posters on your thread are the best in the business. You must feel privileged!