Tire question - May be stupid!!

N

Nharris89

Member
Hey all, so this may sound stupid but I am ditching the run flats (at last) and getting a new set of tires. Before I go ahead and order, I have different size rears to fronts. Fronts are - 225/40R18 and rears are 255/35R18.

Do these sizes seem right to everyone? Would I be best to go same size all around?

Sorry if this is a dumb thing to ask!
 
You have a staggered set, which is quite normal.

You can go same size all round (i.e. a 'square' setup), but it might depend on whether your wheels are the same all round or not.
 
mmm-five said:
You have a staggered set, which is quite normal.

You can go same size all round (i.e. a 'square' setup), but it might depend on whether your wheels are the same all round or not.
Click to expand...

Ah brilliant thank you! I think I'll just order the same sizes as what's on there now then :)
 
I think you will be pleased. I put a square set of Michelin tires on my E89 and found it greatly improved the ride and handling. 18mm spacers in the rear help handling and fill the arches.
 
Slightly related question:
If I wanted to convert to a square setup, could I just purchase a pair of 'front' alloys that match my current set, run them on the rear with appropriate spacers and run 225/40 tyres all around?

I currently have staggered MV2s on it but I feel the 2.0 doesn't really benefit from that much rubber at the back.
 
no need to bother... the rear wheels are only half an inch (13mm) wider than the fronts, you can quite happily run a 225/40 on a 8.5" rim, well within limits.

https://lvvta.org.nz/documents/infosheets/LVVTA_Info_01-2009_V3_Tyre_Size_to_Wheel_Size_Compatibility_Guide.pdf

and the offset only differs by 3mm, so no need to bother with spacers either.

the only problem with running a square setup on staggered wheels is making sure the rears go on the rear, though again, fronts and rears are so similar i doubt you'd notice if you accidentally put a rear on the front.
 
brillomaster said:
no need to bother...
Click to expand...

That's good to know.
What are people's thoughts on that setup?
Obviously the smaller tyre is a little cheaper, bonus.
Does the square setup handle well?
 
Arguably better than staggered, which just encourages understeer. As you say, the 2 litre hasnt got the torque to trouble the rear axle that much.
 
Fill your boots! https://z4-forum.com/forum/viewtopic.php?f=49&t=107556 :)
 
My wife's 2.5i has a square set up with 245/40 x 18 front and rear. I thought that was a little wide on the front but she loves it and says it handles well.
Our only slight difference is a set of 3-series MV2s on the rear, which are only 8 inches wide but with an ET of 20, so they fill the arches more. In turn, that could give me an issue if they went on the front but with a significant dish to them it is easy to spot.

I wonder if you may find 225s on the back look a little lost?
 
enuff_zed said:
I wonder if you may find 225s on the back look a little lost?
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I think it may look a little odd! They certainly won't fill up the rear arches as nicely.

I just want a little less traction at the back. Finding the limits seems to require some very aggressive driving due to how much tyre is back there.

Maybe Mr wilks suggestion of 235s would be a good middle ground.
 
My 2003 Z4 has 225's front and back so am i right is thinking thats an acceptable mod and I'll see no benefit by changing the rears to 255's?
 
Take a pic bud. I assume you have 16 or 17” wheels?

Some alloys are square so will be fine as it is. Some are staggered and really need the extra width as specified by BMW (or at least some of it)....
i.e. if you’ve got 8& 1/2J rear then you want at least 245 imo. 255 is what bmw recommend.
 
Defo something amiss there. Style 107 should be staggered. So should have 255 at the rear. The exception to this is if you have a Frankenstein set. So 4x front wheels (rear wheels are very prone to cracking).

When you can get the rears off and take a look at the stamps on the inside spokes. Should say 8 1/2J somewhere. Or maybe 18 x 8 1/2 J
 
Brill thanks, I’ll whip one off and take a look. I’m getting them refurbished as soon as they start back at work.
Thanks ever so much 😊
 
Turns out the back tyres were wrong so I had some 255's fitted and it looks so much better, the tyres don't looked stretched like they used to. I also got them refurbished as they were all badly curbed.
So thanks kis, I'd never have realised there was an issue without your advice.

49991662388_5de8c5659e.jpg
 
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