Maximum front/rear tyre width difference for 4motion?

[dylan8]

you could possibly do 235/40 all round. your rear wont be legal is all. Might just have to pay someone cash and fit the rear and not take a receipt... its only a touch under what you can legally do.
If you want to do guard work you can fit what you want really.

[FarQ]

I'd be more concerned about any insurance claim, should it arise with fittings tyres and wheels that may not be legal. Even if it is legal, I would get something in writing from the insurance company, as most only require the wheel+tyre be the same rolling diameter, but only allow 1-1.5" larger width wheel based on the largest width wheel on the tyre placard

[kapowww]

you could possibly do 235/40 all round. your rear wont be legal is all. Might just have to pay someone cash and fit the rear and not take a receipt... its only a touch under what you can legally do.
If you want to do guard work you can fit what you want really.

Since it's tax return time I might get the more expensive tyre sizes and some guard work.

I'd be more concerned about any insurance claim, should it arise with fittings tyres and wheels that may not be legal. Even if it is legal, I would get something in writing from the insurance company, as most only require the wheel+tyre be the same rolling diameter, but only allow 1-1.5" larger width wheel based on the largest width wheel on the tyre placard

I'm not too concerned with insurance. I've only got 3rd party anyway.. I prefer to self insure with the money I save on not paying full comp (and that's been a lot over the years). In the past wheel size has never really been a problem in an insurance claim from what I've seen.. While on my P's I put 17s on my dad's Nissan NX Coupe which originally had 14s. He got hit and had no problems claiming.

If an insurance company wants to find something wrong with your car they will.

[FarQ]

Offset & wheel size Calculator here which is quite good. With the rims you have, you can fit 255/35R18 tyres all around.

[dylan8]

Offset & wheel size Calculator here which is quite good. With the rims you have, you can fit 255/35R18 tyres all around.

Only problem with that calculator is isnt doesn't do stretch
His bora is going to be fair low to fit those wheels so i doubt 255s with cut it...

[kapowww]

Only problem with that calculator is isnt doesn't do stretch
His bora is going to be fair low to fit those wheels so i doubt 255s with cut it...

Yup will need stretch. Stretching a tyre doesn't change the rolling diameter does it? I thought it only stretches the sidewalls out and the effect on rolling diameter would be negligible?

[dylan8]

Yup will need stretch. Stretching a tyre doesn't change the rolling diameter does it? I thought it only stretches the sidewalls out and the effect on rolling diameter would be negligible?

does a touch, but not something worth calculating, as you said.

[kapowww]

Found a place that will do KU31s in 235/40/18 all round for $800 (including stretching). Price seems decent. Just trial fitted the front wheel today as I've been lazy and it's rubbing on the calliper. Looks like I need a small spacer for the 18x8.5 +30 fronts..

[dylan8]

will be keen to see how u go with the spacer on the 8.5et30, thats what i currently have and am looking at putting a 5mm spacer in to trial

[Shadow_Rusty]

Tyre Pressures will affect it, but 225/40/18 Fronts will match quite nicely to 255/35/18 Rears

Rim Radius - 228.6mm

Sidewall 225/40 - 90mm
Rolling Diameter 225/40 - 2001mm

Sidewall 255/35 - 89mm
Rolling Diameter 255/35 - 1997mm

So Running the Rears 2psi harder than the fronts will probably resolve this...
Also, as there is more weight over the fronts, the rolling diameter is actually slightly smaller.

Good tyre size comparison site: Tire Size Calculator - tire & wheel plus sizing

[kapowww]

Tyre Pressures will affect it, but 225/40/18 Fronts will match quite nicely to 255/35/18 Rears

I know but the problem is price and fitment under the guards. Those irregular sizes cost $100 more per corner at least, and then the rears will be hard to fit.

I trial fitted my rear wheels (18x10 +25) and it fits the same as the fronts.. Rubs on the calliper but also the stock strut. I don't know if once the KW coils are installed it will make it worse or better. Should be better but I haven't even opened the box yet. My mate has some cheapo 8mm spacers I will try out.

Also since I'm only trial fitting on one side the left and right sides of the car should be the same right??

[dylan8]

are 4mo offsets different to the 2lt bangers? this is the second case of wheels no fitting. or are peoples wheels just the wrong offset...?
my 10s arnt as aggressive as those and i dont touch the rear strut or ever the dust cover on it.
Id imagine itll be worse becuase the wheel will camber in on the rear?

Should be the same... however mine are different by a few mm, passenger side my current setup is flush, where as the drivers side pokes a touch. but that could be put down the body damage or rear beam being off centre.

[Coralon]

The 4mo has independent rear suspension same as the R32 so camber and fitting will be a little different than the FWD versions, obviously lowering will increase the camber and thus strut clearance issues.

Of course I could be hugely wrong but this would be my best guess.

[dylan8]

yep id say your right about the rear.
The front would be the same setup though...?

[Coralon]

I guess the front would be the same, not sure about the offset on my wheels but they are 18x8 with 225/40 on them and i have about 5 mm clearance for the fronts to the strut.