Any pics of 18" Forgestars mounted?

[inTgr8r]

Originally Posted by MakoBimmer1

I am considering going with 235/40-18 on the front 18x8.5 and 265/35-18 on the rear 18x10. This should be ok for just street driving, right? Tire Rack shows me a warning message when I go to purchase these tires in this size as it is not considered the right size.

Tire rack is suggesting 225/14-18 and 255/40-18.

What differences would I see and feel between the two sizes if anything?

TIA for all your wheel/tire guru expertise!

--Chad

???
The OE size should be 225/45-18 and 255/40-18

But the ones you're looking at will most likely be my choice as well.
They will reduce your diameter by ~0.6" from OE spec.
I think thats fine as long as you do both front & rear. (should keep DSC happy)
Also, a benefit is a minor total gearing advantage.

Negative is that the car will record a few extra miles on the ODO & speedo will read slightly faster.

[nlink720]

I have a 2004 Z4 3.0i with 18x8.5 square at a 30mm offset with 255/35-18 tires all around. The front is close, but there is no rubbing. The rear has plenty of space. Just make sure your offsets are ok, and you should be fine -up to about a 10" rear wheel. You could also just run the wider rear tires on a 9" wheel since 10" should not net you much, if any, performance advantage with only a 265 rear tire. I would go with a 9" rear wheel or perhaps 9.5" rear wheel, or even skate by with 8.5" square.

[Blind32]

Originally Posted by inTgr8r

???
The OE size should be 225/45-18 and 255/40-18

But the ones you're looking at will most likely be my choice as well.
They will reduce your diameter by ~0.6" from OE spec.
I think thats fine as long as you do both front & rear. (should keep DSC happy)
Also, a benefit is a minor total gearing advantage.

Negative is that the car will record a few extra miles on the ODO & speedo will read slightly faster.

The ODO will still read accurate since the ECU has the real speed from other variables. The speedo will read slightly faster tho.

[inTgr8r]

^ thanks... wasn't sure where the ODO picked up it's source.

[GP20]

Originally Posted by MakoBimmer1

I am considering going with 235/40-18 on the front 18x8.5 and 265/35-18 on the rear 18x10. This should be ok for just street driving, right? Tire Rack shows me a warning message when I go to purchase these tires in this size as it is not considered the right size.

Tire rack is suggesting 225/45-18 and 255/40-18.

What differences would I see and feel between the two sizes if anything?

TIA for all your wheel/tire guru expertise!

--Chad

Aside from the speedometer being a little more off, you'll be okay. Less unsprung weight, better gas mileage, and less tramlining. I might go with those sizes for my next set of tires, too.

[GP20]

Originally Posted by Blind32

The ODO will still read accurate since the ECU has the real speed from other variables. The speedo will read slightly faster tho.

Actually, inTgr8r is right. The odometer will record a few extra miles when reducing the tire diameters.

[Blind32]

Originally Posted by GP20

Actually, inTgr8r is right. The odometer will record a few extra miles when reducing the tire diameters.

My appologizes then. I'll go do my homework

[MakoBimmer1]

Originally Posted by GP20

Actually, inTgr8r is right. The odometer will record a few extra miles when reducing the tire diameters.

By how much you think? I dont want to rack up false miles!

[inTgr8r]

Originally Posted by MakoBimmer1

By how much you think? I dont want to rack up false miles!

For every 1000 miles you will rack up 1027 miles.
Data sheet

[Z4Murder]

Originally Posted by GothM

IMHO 236/265 set up would be adequate. You would save a little weight, get less tire "pooch" and the car would be more fun to drive if you like to chuck it around. Like I said though I have not got to explore the 245/275 set ups full potential yet.

yea, i've been doing some research on tire traction and it seems tire width is much less important than sidewall flex and tire compound. but ya gotta admit a wide set of tires look mean!

could also save ourselves some worries about hydroplaning with a little smaller tire

[GothM]

With my 245/40 275/35 set up on Nitto Invos I was surprised the sidewall actually ended up being taller than the stock 45/40 set up. I ran into a similar issue on my M3 between Advan Neovas and Hoosier A6s both identical size but the Hoosiers being taller. That is typical from my experience with race rubber though. So between brands you may find that the side-walls vary slightly.

Depending on the tire you might get a little pooch effect but unless it is substantial, you are really one with your car or driving competitively and keeping a data log you probably wont notice if the diameter is slightly off.

If your time/budget allows it is fun hit the track or auto-x to experiment with tires to see how they effect your car.