17" rims and tires on a M35x?

[spbrant]

I would like to get a second set of rims and tires for my 2006 M35x. I would like to get something from Tirerack in the 17" rim size so the cost per tire and tread life would improve. I would be money ahead in the long run. Anyone know what the equivalent 17" tire size would be for the 245/45/18 tires that are on my M35x now? Has anyone heard of people doing this before? Thanks.

[szh]

Welcome to NICO!

I would like to get a second set of rims and tires for my 2006 M35x. I would like to get something from Tirerack in the 17" rim size so the cost per tire and tread life would improve.

Not necessarily true, unfortunately. See below ...

I would be money ahead in the long run. Anyone know what the equivalent 17" tire size would be for the 245/45/18 tires that are on my M35x now? Has anyone heard of people doing this before? Thanks.

1. Most 245/45-18 tires typically have a rolling diameter of 26.7" or so, with a typical 785 revs/mile. To get the same result in a 17" rim, you would need to get a 225/55-17 or 235/50-17 tire for similar diameter and revs/mile. The rim would need to be 17 x 7.5 or 17 x 8 for this tire ... remember that the wheel offset needs to be about 45 to 50mm for your car model. With these tire sizes, ride and handling would suffer for sure. The car suspension is optimized for a lower aspect ratio sidewall. 2. My big concern would be whether the 17" rim might have fitment difficulty ... like contact to some brake or suspension component item (caliper contact would be bad). Somebody at Tire Tack might be able to tell you this, if they have done a fitment test of this type.

3. Are you really sure that you want to do this change? The price difference between a typical 225/55-17 and 235/50-17 tire to a 245/45-18 tire is not that great, actually. Because the 245/45-18 is a very standard size, and there are lots of brands/models available for it. So, why not just get less expensive tires perhaps? For example, the Avon Tech M550 tire from Tire Rack is about $150 a tire in a 245/45-18 size and a decent compromise.

BTW, when adding tires to a luxury (and heavy) sedan like the M35X, you do not want to compromise the handling and safety aspects. So, Grand Touring tires may seem like a good thing to do, but the load index and speed ratings are generally lower and tires fail internally (generally invisibly ) till they become unsafe, or require frequent re-balancing to keep them from vibrating, etc.

Z

[spbrant]

Thanks for the advice. After reading it, I believe I had better stick with what I have and not play around with it. Thanks again.

[szh]

Thanks for the advice. After reading it, I believe I had better stick with what I have and not play around with it. Thanks again.

A most excellent choice!!

Z