Different Size Tires

BGTV8

No, simply suggesting that going back to the OEM tyre size for the rear is the most logical solution.

People need to realise that vehicles fitted with ABS and Stability Control rely upon the front and rear wheels rotating at the same speed and this can be affected by fitting tyres ith different diameters than the manufactiruer intended, because that affects one of the most basci stability control parameters.

If you are changing tyre sizes, then make sure that you respect the relationship between overall diamter of fronts and rears.

Your tyre shop should have been aware of this.

Masa

Ding ding ding! Winner.

The problem is now your rear tires are 1 inch diameter less than the fronts because of the 40 series sidewall. You need 45 series sidewall with a 245 width.

Right your your front 225/50/18 have an overall diameter of 26.8 inches and the rear 245/40/18 have an overall diameter for 25.7 inches. This is a 4% variance which will throw your abs/vdc out of sync causing instability issues.

You want to stay within 1% variance when running staggered set ups.

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BMW 340i
Jeep Cherokee Trailhawk

roplusbee

This!

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2007 350Z NISMO #0618: Zerolift | UPREV | F.I. | Greddy | Competition Clutch | Injector Dynamics | Aeromotive | Pioneer | JL

chrischhorn

I ran them for a month or so with those sizes before I bought my new wheels since I was basically pre planning the new wheels.

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R.I.P. 8/01/13 1SlowZ
One day I'll have another....

Zis4me

So I could run 235/45 and 255/40 with no problem what if i wanted to jump up to 235/45(front)F 275/40(rear) in the rear.. would that be an issue?

chrischhorn

a 245/45 on front and a 275/40 on the rear would be fine. 235/45 is still too small to OEM diameters. 275/40 is almost a direct match for OEM diameters and so is 255/45 which are the reasons I chose these sizes. My next set will be a 275/35 and a 255/40. Smaller diameter so "shorter gearing" for autocross or maybe just a 275/35 square setup.

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R.I.P. 8/01/13 1SlowZ
One day I'll have another....

Zis4me

235/45 and 255/40 is not good either?

chrischhorn

Technically yes it will work together but not individually......dunno why you have to make it so complicated..

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R.I.P. 8/01/13 1SlowZ
One day I'll have another....

Waiz

Use this tire size calculator:

Tire Size Calculator - Compare Tire Sizes

Using your current specs your front tire is taller than your rear tire, this is a disastrous setup.

You want to maintain around a 3% difference to keep all TCS, VDC happy with your rear tires always being larger

I would go with 225-40-18 front and keep your rears as is

Zis4me

i'm just gonna run stock then
til i buy rims next year

Zis4me

you think I should run 40's all around.. that wont cause an issue?

chrischhorn

VDC/ABS/TC won't have issues but your going to be going smaller sidewalls and I can almost guarantee that your tires dont meet the recommeneded vehicle load rating. Load rating is what the manufacturer decides what is needed to properly and safely support the vehicle. A lot of people to careless but I tend to bother them with it anyways. I drive my vehicle aggressively and make sure that the tires can withstand what I or the road throws at em.

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R.I.P. 8/01/13 1SlowZ
One day I'll have another....

Waiz

Of course not, as long as you maintain enough stagger

Just use the sizing I gave you, it's not that difficult