Front 225/45/18, Rear 255/40/18, will this work?

[bradc]

According to http://www.tyretraders.com/tyrecalc.html the difference between the 225/45/18 and 255/40/18 is only 0.22% larger, or 0.75mm.

Will this small size difference affect the 4WD system at all? I figure that even with matched tyres all around there would probably be more than this anyway in lots of peoples cars, because of difference in air pressure, and from how the tyres are individually worn.

The next important question is if it is even possible to fit 255mm tyres under the rear wheel arches. I have the facelift model, with the extended wheel arches, so I can offset the wheels further out from the car by about 20mm more than the normal models. I'm sure it is more than possible, looking at my current tyres there is about 10mm clearance between the suspension arm and the inside of the tyre, and I can easily move the wheels out by another 20mm before they extend further than the wheel arch. The big difficult question is really about if the 4WD system will handle the 0.22% difference.


215/40/18 and 245/35/18 are another option this is only 0.07% /0.25mm , but my car has 225's as standard on the front, and it would seem a little strange going to narrower tyres

[Nick Mann]

Why do you want to do it? IMO the cars handling is pretty neutral anyway.

[bradc]

it looks better :D The current model BMW M3's have the exact same tyre size as what I'm proposing, and their tyres look really really wide at the back.

Also, I know I can swing the back out quite easily around roundabouts and low speed corners, hopefully the wider rear tyres will make it a little bit more difficult to do that.

[Nick Mann]

Isn't the M3 rear wheel drive?

And if you can get the back out easily, are you provoking it or is your current rubber no good?

Not saying its a bad thing to do - I have no idea - but just not sure if it is worth it!

[bradc]

Yeah it is, I haven't been able to find too many 4wd cars with differant sized tyres, which is why I'm being fairly cautious about it all.

And yeah, I'm provoking it, my current tyres are reasonable, but the car starts to go sideways shortly after I hit the 3rd light on the AYC, and I'd like it to be a little bit better than that. Looks are still the main reason though.

[Roadrunner]

I run Evo VII wheels and tyres (235s on 8" wide 17" wheels) and the tyres rub marginally on the plastic arches when the car's loaded. With another 20mm of rubber outwards (as you say, there's little clearance inwards) I think the tyres would snag the arches. I reckon the reason you don't see AWD cars with different size wheels front to back is that any major difference in rolling radius would start to wind up the centre diff which would result in it running hotter and probably lead to premature failure. I know you've matched the rolling radius as best as possible so that probably wouldn't be an issue. However, I'd still be concerned that the rear would have more grip than the front which could lead to big understeer. If you're running out of grip at the extreme (3 bars on the AYC?) maybe you need better tyres? Bearing in mind, of course, that the laws of physics apply and you must run out of grip at some point ... ;)

[bradc]

I've seen a few people here running 245 tyres without too many problems, I guess it also depends by how much the car is lowered as well, mine isn't lowered at all at the moment, so there is tons of room between the wheel arches and the actual tyre.

Do you have any issues at all with the front tyres, do you have plenty of room?


It will only understeer at the limit, the point is to eliminate oversteer as much as possible, while making the car look really good.

[Roadrunner]

Do you have any issues at all with the front tyres, do you have plenty of room?
No issues with the fronts, although 255s would likely be outside the outer line of the arches. Mine isn't lowered either but, with four up, the rears can foul the arches. You could always trim the insides of the arches, though ...

[EdmundVR4]

H7, Have you checked the stock offset of the Evo & VR4 wheels ? I do believe they are different (Evo : 30 something & VR4 46mm) & that extra 10mm offset coupled with a wider tyre will cause your tyres to rub under load. I have 40mm offset wheels with 235/45/17 tyres & I have heard them rub only twice in 90,000km of fairly hard driving on Trinidad's bad roads.
BradC, I've seen my AYC lights (yellow bars) come on a few times while driving normally on the highway & when I stopped and checked the tyres, sure enough, one of the rear tyres was a bit soft (nail in tyre leaking slowly). I've driven my car 30km with the donut spare tyre on & the AYC light was on all the way home & AYC is still working fine.So, the AYC does pick up minor differences in tyre size.

Edmund

[Roadrunner]

Yep, the Evo wheels are +38 offset vs the standard wheels' +46. It was only noticeable with a full load (four heavy guys in the car) but not something I worried about. I think the 255s would be a problem, though ...

[bradc]

So the overall opinion is that 255's simply won't fit on the rear very well, that sucks. Guess I'll just stick with normal 225/40/18's then.

[Kenneth]

brad:
I would be dubious about putting wider rears than fronts on your VR-4

4WD cars are known to show understeer characeristics. I believe that the 40/60 front/rear torque split when accelerating is to address this issue.
When at low speed/gears the VR-4 has plenty of torque to exceed the availably traction on the rear tyres when turning a reasonably sharp corner.

However at high speed, the handling is superbly balanced. I would think very very very hard before messing with this setup.

Now if you could adjust the torque split... but thats another story.

[bradc]

What concerns me the most is low speed intersections and roundabouts where the car does feel a bit skitish at the back wheels under full throttle.

If the 255 tyres would fit, and there wouldn't be any problems with the 4WD system due to differant tyre sizes, then I would go for it straight away.

Another problem I had was trying to find mag's available in 18x7.5" (front) and 18x8" (rear), it is very hard to find a style of mag that is available in both those sizes.

[Kenneth]

If you are flooring it at low speed intersections / roundabouts the back end comming around is deffinatly preferable to front end slide. first off, it looks cool and second you tend to spin out instead of running up the kerb and breaking your wheels.

Other thing is that you should take a serious look at your tyres. If you have crap tyres, your VR-4 will feel skittish no matter how wide your tyres are.

I would look at getting some nice rims of the same width all round. If i had the choice and the cash to do it, I would look at 17" by 8" dished rims.

[KiwiTT]

I would never have different sizes. A Subaru I heard about had different sizes and the 4WD drivetrain was ruined. It is not worth the risk.

Take Kens advice, get good wheels and tyres of the same type,

[bradc]

ok, you've all managed to convince me to go with either 225 or 235/40/18. Now only one more question, does anyone know an exact way to figure out what width rims you should use with 225 or 235 tyres? I've seen anywhere between 7"-8" for these sizes, and I really don't understand it.

[EdmundVR4]

bradc, I have used both 225 & 235/45/17 tyres on my car with my Konig 17"x8" wheels & I found the 225 width tyres to be a bit too narrow for the rims. If I had to buy rims again I would go with 7.5" width, which I think would be suitable for both sizes, but preferably 235's. Two important performance consideration on the wheels is weight...the lower the better & manufacturing process...forged is better than cast. And, don't forget to get the correct offset(or nearest available)

[dickytim]

not trying to contradict any one but the subbie 4WD systems is VERY different to our own, ours uses a viscous coupling, while the subbie system uses a clutch type set up copied from porsche, this means that the subbie system would be more likely to suffer from those sort of problems more than our cars, Bradc, I have seen your rears, Yokohama Avid somethings, you have the same set up as my car, the rears are no where near as good as the RE-01's on the front of your car, I suggest if it were purely a handling issue change your rears, if it is for looks then go to http://www.work-wheels.co.jp/wheels/index/emt-k1p-2/emt-k1p-2.html#

[bradc]

How on earth can you remember the tyres I had on my car? I'll definately get bridgestones all round with my new mags, I've been very impressed with the ones on my other legnum.

I quite like these designs, as you can see I've got quite a few! Do you know where to get work wheels from in this country?

http://www.liveupdater.com/magandturbo/LiveArticle-form.asp?ArtID=-825936785
http://www.liveupdater.com/magandturbo/LiveArticle-form.asp?ArtID=-107239476
http://www.liveupdater.com/magandturbo/LiveArticle-form.asp?ArtID=-1321285730
http://www.bgworldwheels.co.nz/images_bbs/RX.jpg
http://www.bgworldwheels.co.nz/images_bbs/RC.jpg
http://www.yhi.co.nz/images/wheels/advanti/advantipops05/11-octane_gunmetal.jpg
http://www.yhi.co.nz/images/49.html
http://www.yhi.co.nz/images/46.html
http://www.in-site.co.nz/dtm/links/gallery_items/1_11_33_large.gif

[bradc]

found their site ;)

http://www.work-wheels.co.nz/wheels/cx.htm
http://www.work-wheels.co.nz/wheels/emotioncrkai.htm
http://www.work-wheels.co.nz/wheels/tm1.htm

[dickytim]

I don't know where to buy them from I only know the guy who brings them in, and that is thru an aquantance.

And as far as remembering what tyres you have it is those stupid little trivial things I CAN remember, don't ask me to remember a name tho !!!

[OSiRiS]

I would look at getting some nice rims of the same width all round. If i had the choice and the cash to do it, I would look at 17" by 8" dished rims.

Like the rims I have for sale ;)


Bradc, I have seen your rears, Yokohama Avid somethings

Yokohama Advans?

Anyways. No I wouldn't load up two different sized tyres or even wheels on a 4WD system.

[Kenneth]

Like the rims I have for sale ;)


Yes like those... lol

im a couple of months away from rims atm... would need tyres to go with rims also.

[chris g]

I cannot believe that you are thinking of putting different size wheels/tyre combination on front to rear

I have recently sold my 7g Galant Sports GT and when discussing tyres with the woman who bought it, even she said that you do not mix tyre/wheel sizes with 4WD or you risk transmission damage!

[bradc]

since then I've found another size that is even closer, 235/45/17 front and 265/40/17. This is only 0.07% differance.

I understand that it will affect the 4wd system if there was a big differance, but surely the system would be able to handle a small differance of less than a percent.

[chris g]

For me the % issue is about speedo accuracy - nothing else

If you want to chance it and it may be that you are talking yourself into it, go ahead and try it BUT keep the car with that tyre/wheel combination for a significant time and see how long the transmission lasts

Hopefully it will last for years, but then it may............

[bradc]

after fitting 235's today I know that there is no way 265's will fit on the back anyway, so it doesn't really matter. ;)

[You See]

Told you so. :rolleyes4

[dickytim]

Sam will roll you rear gaurds for $45 a side including GST etc, 021 711 762, just be aware that if you have had the wheel arches touched up or there is any bog in them then it will crack the paint.

BTW do they rub on yours Brad or do you not corner fast enought :P

[bradc]

I've already asked pitstop to, and I'm booked in on thursday next week, they are also going to get my exhausts level :D

They definately rub, even on the motorway hitting bumps and stuff they would rub. They are terrible around corners too ;)

[dickytim]

I have almost got my suspension sorted, just did the right hand side lower ball joints so have done both sides, it is a lot tighter and I have lost the nasty vibration at speed, now I need to get the wheels balances and the alignment done and then it will (possible) be out for a track day at pukekohe Sunday week. Something to do with a swap meet.