What do you think about this tire combination

slow35th · #1 (**permalink**) 02-13-05, 02:34 PM

When it comes time to replace my tires I am thinking about running 275 40 18's in the rear and 245 45 18's up front. I think you could get away with this on the 8.5 inch rims as it is only .5 inches shy of the recommended minimum for the 275 40 18. This is the same rolling diameter and there are several makes in this size combination. The goodyear G3's and the Toyo T1-S's both come in this size combination. I know that you would give up the ability to rotate but that is the case on several vehicles anyway including my SRX. Is anyone running this combo?

Lance

StealthV · #2 (**permalink**) 02-13-05, 05:01 PM

Mmm...275s. Be the ginuea pig!

thebigjimsho · #3 (**permalink**) 02-13-05, 07:33 PM

You are in virgin territory here. I'm not sure what will happen to handling. You could say you will gain a bit of understeer. But, with the same width wheels, you will have a little less control in the rear because of the angle of sidewall to rim. So, would that little bit of control loss mean that you won't have as much understeer as if you had a wider wheel in back? Or would that really change everything. I'm not sure.

Let us know.

wildwhl · #4 (**permalink**) 03-24-05, 10:17 PM

The Maggie is insisting that I try this

CTSV05 · #5 (**permalink**) 03-24-05, 10:50 PM

Just so I'm clear, the overall diameter is the same, so the only difference is the tire is wider?

Is this correct.

So if that is the case, your sidewall will react differently, due to the tire needing to bulge in the sidewall, to squeeze onto the rim.

Then if thats correct, won't you lose some tread contact on the edges of the wider tire?

slow35th · #6 (**permalink**) 03-24-05, 10:57 PM

Recomended rim width for the 275 40 18 is 9 inches. Our rims are 8.5 inches. I think you could get away with it. My SRX came with a similar tire combination on the same size rims. My only concern when I made the original post was whether or not the wider tire would have clearance in the rear.

slow35th · #7 (**permalink**) 03-24-05, 11:10 PM

Here is a comparison of dimensions. 275's on top

Section Width: 10.82 in 275 mm
Section Width: 9.64 in 245 mm

Rim Diameter: 18 in 457.2 mm
RimDiameter: 18 in 457.2 mm

Rim Width Range: 9 - 11 in
Rim Width Range: 7.5 - 9 in

Overall Diameter: 26.66 in 677.16 mm
Overall Diameter: 26.68 in 677.67 mm

Sidewall Height: 4.33 in 109.98 mm
Sidewall Height: 4.34 in 110.23 mm

Radius: 13.33 in 338.58 mm
Radius: 13.34 in 338.83 mm

Circumference: 83.75 in 2127.2 mm
Circumference: 83.81 in 2128.7 mm

Revs per Mile: 780.1
Revs per Mile: 779.6

Speedometer1: 60 mph 100 km/h
Speedometer2: 59.9 mph 99.9 km/h

CTSV05 · #8 (**permalink**) 03-25-05, 12:59 AM

Well, it shouldn't be a problem, but I still think you'll lose some of the "flatness" of the contact patch, but it can't be much.

V-lociity · #9 (**permalink**) 03-26-05, 12:06 AM

Just my untested and well researched opinion. If you replace the "OE" tire with a non factory tire make sure that you
1: meet or exceed the service rating of the OE tire (in the case of the Goodyear Eagle F1 Supercar 1565 lbs. @168 mph.)
2: If you decide not to follow the recommended rim width guidlines realize that the tires ability to handle cornering loads can change non-linearly making it possible to damage the structure of the tires carcass and possibly unseat a bead etc..
food for thought?

globed70 · #10 (**permalink**) 03-26-05, 11:33 AM

Other than looks or bragging, I don't think there is much to be gained from mounting a wider tire under the minimum width. A properly fitting 245 has to be a better answer than an odd fitting 275. So what is the reason?

wildwhl · #11 (**permalink**) 03-26-05, 01:32 PM

Looks, partly, but I was hoping for a larger contact patch (guess I'll have to rethink wider rear wheels first)

urbanski · #12 (**permalink**) 03-26-05, 01:59 PM

Quote:

Originally Posted by wildwhl

Looks, partly, but I was hoping for a larger contact patch (guess I'll have to rethink wider rear wheels first)

19" HRE C20s are calling your name

http://www.daemonmotorsports.com/cat...hp?id=42869635

StealthV · #13 (**permalink**) 03-26-05, 05:55 PM

Come on Urb, 841Rs ! :coolgleam

urbanski · #14 (**permalink**) 03-26-05, 06:28 PM

Quote:

Originally Posted by StealthV

Come on Urb, 841Rs ! :coolgleam

I'll use the grand I'm saving with the Comp series to buy, er, stuff, like CTSV05's AH kit, maybe a shifter, and the downpayment on the head/cam package

slow35th · #15 (**permalink**) 03-26-05, 07:03 PM

Quote:

Originally Posted by V-lociity

Just my untested and well researched opinion. If you replace the "OE" tire with a non factory tire make sure that you
1: meet or exceed the service rating of the OE tire (in the case of the Goodyear Eagle F1 Supercar 1565 lbs. @168 mph.)
2: If you decide not to follow the recommended rim width guidlines realize that the tires ability to handle cornering loads can change non-linearly making it possible to damage the structure of the tires carcass and possibly unseat a bead etc..
food for thought?

Item 1. All of the tires we are talking about here are Y or z rated tires.

Item 2. I would agree with you if we were talking about 1 or 2 inches below recomended rim width but half an inch is not likely to change the contact patch or handling characteristics of any significances on a 40 series tire.