Staggered Wheels Sizes On 34 Gtr

[JonoT]

Hello Everyone can you please help me out on question about Staggered wheel sizes on and 34 GTR.

I have Search the forums and no one can give me a definate answer to why this is not a good idea. The wheels i have in mind are 19' by 9.0' on the front and 19' by 10.5' on the rear. I can understand that the ETS/ATTESSA may not like this but i cannot understand why that would be true on a near stock GTR?

Has Anyone come across this or any related problems when they have fitted Staggered Wheels like this??

Thanks in Advance

[gt-ahhh!]

i dont see why there should be a problem providing the wheels fit of course. how does it affect the attessa? having more rear traction would mean attessa is less likely to be engaged would be my understanding.

but im only a gts-t driver where staggered wheels is desirable!

10.5s though... nice.

[Sydneykid]

Hello Everyone can you please help me out on question about Staggered wheel sizes on and 34 GTR.

I have Search the forums and no one can give me a definate answer to why this is not a good idea. The wheels i have in mind are 19' by 9.0' on the front and 19' by 10.5' on the rear. I can understand that the ETS/ATTESSA may not like this but i cannot understand why that would be true on a near stock GTR?

Has Anyone come across this or any related problems when they have fitted Staggered Wheels like this??

Thanks in Advance

The ATTESA in an R34GTR runs constant/residual pressure, so the clutch pack tries to make the front wheels turn at the same speed as the rear wheels. If they are different diameters then the clutch pack overheats and eventually wears out. For that reason alone it is not a good idea to run different diameter tyres. A ~3% difference in diameter (as in new tyre versus old tyre) is OK of course.

As for tyre width, that is not so black & white, it's more subjective. Personally I can not understand people using a smaller front tyre than the rear when 65% of the weight of GTR is on the front wheels. They already understeer as a result, so why anyone would want to make that worse is beyond my comprehension.

Cheers

Gary

[JonoT]

i dont see why there should be a problem providing the wheels fit of course. how does it affect the attessa? having more rear traction would mean attessa is less likely to be engaged would be my understanding.

but im only a gts-t driver where staggered wheels is desirable!

10.5s though... nice.

Mate thats what i would have thought but... there is some threads on this and uk Forum sites that state that it may confuse the Attessa and hurt the diffs and transfercase. I cant see how but i had someone say that they had hear of this happening. Hopefully someone can dispell any rumours aboout this and give me the facts on why or why not this would happen.

Thanks for your input

[JonoT]

i dont see why there should be a problem providing the wheels fit of course. how does it affect the attessa? having more rear traction would mean attessa is less likely to be engaged would be my understanding.

but im only a gts-t driver where staggered wheels is desirable!

10.5s though... nice.

Mate thats what i would have thought but... there is some threads on this and uk Forum sites that state that it may confuse the Attessa and hurt the diffs and transfercase. I cant see how but i had someone say that they had hear of this happening. Hopefully someone can dispell any rumours aboout this and give me the facts on why or why not this would happen.

Thanks for your input

[JonoT]

i dont see why there should be a problem providing the wheels fit of course. how does it affect the attessa? having more rear traction would mean attessa is less likely to be engaged would be my understanding.

but im only a gts-t driver where staggered wheels is desirable!

10.5s though... nice.

Mate thats what i would have thought but... there is some threads on this and uk Forum sites that state that it may confuse the Attessa and hurt the diffs and transfercase. I cant see how but i had someone say that they had heard of this happening. Hopefully someone can dispell any rumours aboout this and give me the facts on why or why not this would happen.

Thanks for your input

[blind_elk]

Jono, are you Irish? 3 posts the same - to be sure, to be sure, to be sure.

If you run the same size tyres (say 245/35*19) on narrow front and wide rear rims, the rears will have a smaller rolling diameter than the fronts. This is because the sidewalls on the rears are at a different angle to the vertical compared to the sidewalls on the front. This triangulation pulls the tread of the tyre on the wider rim inwards into a smaller rolling diameter configuration. This creates a situation where ATTESSA thinks the rears are wheel-spinning, and so it applies drive to the fronts to "catch up".

If you use different widths front and rear, you risk creating differentials in rolling diameters due to the width and profile combo not quite coming up with the same rolling diameter.

I can't see that it's worth a set of clutch packs to not just fit the same size all-round. And it makes it so much easier to even out wear by swapping front - rear as well.

[JonoT]

Jono, are you Irish? 3 posts the same - to be sure, to be sure, to be sure.

Haha sorry mate the pc at work jammed and some frustrated button pushing resulted in 3 posts

Anyway thanks for the input as well i think we got it about sorted. I can understand that the profile size on the rears will differ (although im not sure how much) and will produce an uneven rolling diameter.

We've been onto the guys at Falken Aust to find out if they can sort a scale to see if 30 profile on the rears will result in an even Rolling Diameter.

These Rims were bought as a set and are no longer being produced so if we can't sort it with tyres I'm not sure its worth putting them on if it results in accessive wear.

[gt-ahhh!]

why cant you run different width tyres and have the same rolling diameter...?

ie: 245 front 275 rear (example only) or like my car, 235/255.

the point about having different rolling diameters is true only if you use the same width tyres but fit them to different width rims.

the best point is in fact that same size tyres and wheels can be rotated for more even wear! but at the end of the day the tyres wear (and replacement) still occurs at the same rate...

Edited January 23, 2008 by gt-ahhh!

[JonoT]

why cant you run different width tyres and have the same rolling diameter...?

ie: 245 front 275 rear (example only) or like my car, 235/255.

the point about having different rolling diameters is true only if you use the same width tyres but fit them to different width rims.

the best point is in fact that same size tyres and wheels can be rotated for more even wear! but at the end of the day the tyres wear (and replacement) still occurs at the same rate...

Very true

I think its more the fact the computer will sense the rears are running either faster or slower depending on the size and try to compensate with putting more torque to the front. I still don't think it would be much but if it wears the front or rear diffs out it may not be a smart idea to do it.

I'm trying to find out if theres someone who has done it with no complications. I know that 'RH9' is running staggered 20' but its more a straight line car.

[blind_elk]

why cant you run different width tyres and have the same rolling diameter...?

ie: 245 front 275 rear (example only) or like my car, 235/255.

the point about having different rolling diameters is true only if you use the same width tyres but fit them to different width rims.

the best point is in fact that same size tyres and wheels can be rotated for more even wear! but at the end of the day the tyres wear (and replacement) still occurs at the same rate...

The rolling diameter comes is a function of the tyre's width and profile. The same profile at different widths gives different rolling diameters.

It can be done; it's a matter of finding the right width / profile combination for both front and rear to achieve a matched rolling diameter. Much simpler process if all four rims are the same.

[Sydneykid]

Very true

I think its more the fact the computer will sense the rears are running either faster or slower depending on the size and try to compensate with putting more torque to the front. I still don't think it would be much but if it wears the front or rear diffs out it may not be a smart idea to do it.

I'm trying to find out if theres someone who has done it with no complications. I know that 'RH9' is running staggered 20' but its more a straight line car.

The ATTESA ECU has no idea about wheel speed. My previous post tells you what the problem is;

The ATTESA in an R34GTR runs constant/residual pressure, so the clutch pack tries to make the front wheels turn at the same speed as the rear wheels. If they are different diameters then the clutch pack overheats and eventually wears out. For that reason alone it is not a good idea to run different diameter tyres. A ~3% difference in diameter (as in new tyre versus old tyre) is OK of course.

If you run an R32 GTR with different diameter wheels you wear out the clutch pack, without really feeling anything too nasty from the driver's seat. This is because they run virtually zero residual hydraulic pressure.

In R33/34GTR's with different diameter wheels you get this massive shudder all through the car after only a couple of k's of driving. This is particuarly prevelent on the freeway, where the straight line running makes the shudder appear very quickly, like in a few hundred meters. If you have a few corners it takes longer for the ATTESA to overheat as there is the differential action from the outside and inside wheels having different radii around the corners. But as soon as you get a straight section of road, the shudder is there. This is not like an out of balance wheel, this is viscious, harsh thump thump thump shudder that feels like your whole car is going to shake itself to death, once you feel it you will never want to again.

If you want to test this out, please feel free to PM me and we can give it a go ..........on your car......... not mine.

Cheers

Gary

[tacker]

Hmmm,

Gary i take your point about the smaller wheel on the front making the understeer worse, and i am going to put 285/30/18 allround next time as i know they will fit in the front wheelwell now without fouling on anything.

Just as soon as i can locate a set of 18 x 10 rims with 37mm offset.

I did manage to get 265/35/18 for the front which was about 32mm more than the 285 in circumference, would that be within the 3% ?

[Sydneykid]

Hmmm,

Gary i take your point about the smaller wheel on the front making the understeer worse, and i am going to put 285/30/18 allround next time as i know they will fit in the front wheelwell now without fouling on anything.

Just as soon as i can locate a set of 18 x 10 rims with 37mm offset.

I did manage to get 265/35/18 for the front which was about 32mm more than the 285 in circumference, would that be within the 3% ?

285 x 30% = 86 mm sidewall

265 x 35% = 93 mm sidewall

93 mm - 86 mm = 7 mm

7 / 93 = 7.5% which is more than 3%

Cheers

Gary

[JonoT]

The ATTESA ECU has no idea about wheel speed. My previous post tells you what the problem is;

If you run an R32 GTR with different diameter wheels you wear out the clutch pack, without really feeling anything too nasty from the driver's seat. This is because they run virtually zero residual hydraulic pressure.

In R33/34GTR's with different diameter wheels you get this massive shudder all through the car after only a couple of k's of driving. This is particuarly prevelent on the freeway, where the straight line running makes the shudder appear very quickly, like in a few hundred meters. If you have a few corners it takes longer for the ATTESA to overheat as there is the differential action from the outside and inside wheels having different radii around the corners. But as soon as you get a straight section of road, the shudder is there. This is not like an out of balance wheel, this is viscious, harsh thump thump thump shudder that feels like your whole car is going to shake itself to death, once you feel it you will never want to again.

If you want to test this out, please feel free to PM me and we can give it a go ..........on your car......... not mine.

Cheers

Gary

Mate thanks for your advice

We got it sorted with the help of the tyre manufactures

we have to run 265/30 front and 315/25 on the rear we've been told that should give us a 640 rolling diameter all round.

Thanks everyone for your advice it came in handy!!!

Edited January 24, 2008 by JonoT

[Sydneykid]

Mate thanks for your advice

We got it sorted with the help of the tyre manufactures

we have to run 265/30 front and 315/25 on the rear we've been told that should give us a 640 rolling diameter all round.

Thanks everyone for your advice it came in handy!!!

Yep that will work;

265 x 30% = 80 mm sidewall

315 x 25% = 79 mm sidewall

But will it ever understeer with 50mm narrower tyres on the front

Cheers

Gary

[tacker]

285 x 30% = 86 mm sidewall

265 x 35% = 93 mm sidewall

93 mm - 86 mm = 7 mm

7 / 93 = 7.5% which is more than 3%

Cheers

Gary

Gary,

i am the first to admit i dont know my a#$e from my elbow, hence why i ask.

But if it is 3% of diameter then i think its ok your calc uses the side wall dimentions not the wheel diameter, again give me a kicking if i am wrong i usually am :-).

If i use your tyre profile calcuations the 285 has a dimeter of 629.2mm while the 265 is 643.2. which is a 2.1% difference on diameter.

Standing by to be corrected :-)

[Sydneykid]

Gary,

i am the first to admit i dont know my a#$e from my elbow, hence why i ask.

But if it is 3% of diameter then i think its ok your calc uses the side wall dimentions not the wheel diameter, again give me a kicking if i am wrong i usually am :-).

If i use your tyre profile calcuations the 285 has a dimeter of 629.2mm while the 265 is 643.2. which is a 2.1% difference on diameter.

Standing by to be corrected :-)

If you include the diameter of the wheel then you are correct, but the tolerance then is around 1%. My 3% rule of thumb on sidewall height makes it easy to calculate on the fly, that's why I use it. The real calculation should of course be the circumference of the tyre, usually expressed as revolutions per kilometre on tyre charts. Or 2PiR in high school maths' terms.

Cheers

Gary

[tacker]

Ok cheers Gary

[tanweer]

put it simply because its all wheel drive different widths mocks up the transfercase...

but having said that you could put stagered fittment if you wanted to coz the point is that GTRs arnt full time all wheel drive (well am speaking bout R33 and R34) and front wheel only hooks up when slip detcted... hope you find the answer you lookin for mate

cheers]