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      09-27-2009, 08:54 AM   #21
Lemans_Blue_M
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Quote:
Originally Posted by ecksreturns View Post
Okay , I saw this thread (http://www.m3post.com/forums/showthread.php?t=279354). Can you recommend the offsets/dimensions for running 20" BBS CH-R's on 305 rear and 255 front?

EDIT - Also checked Tire rack. They recommend offset of 24 for all four wheels and recommend 245/30 fronts and 265/30 rear. I assume these are the basic ones needed? Can we go to 255/30 front and 295 or 305 for the rear with a 25/30 wall without any clearance or rubbing, with any tire brand available? Once I have this clear, I can then go ahead with my decision.
The HRE P40's are available in custom offsets (that you can choose within a given range), while the BBS CH-R's are only available in one fixed offset of +24 front and rear. You don't have the option to change the offset of the wheel itself...but you could add very small 5mm spacers to adjust the offset of the front 20x9 CH-R wheels. That spacer will give you an effective offset of +19 in the front, which is exactly what I recommended in my first post.

It's important to note the CH-R's are flow-formed CAST wheels, while the HRE wheels are 4000 ton forged. So that's not a true apples-to-apples comparison. The CH-R's will also be a few pounds heavier than the P40's (each), but the CH-R's are half the price of the P40's.

The reason the tire recommendations from tire rack are so small, is they are ultra conservative with wheel & tire fitments. (they always have been)

Here is a reality check...

A 265/30/20 rear tire on a 20 x 10.5 wheel is way too small. That narrow tire size would look ridiculous on a wheel that big. Someone screwed up big time on that fitment recommendation. And that's a huge problem in the world of wheel and tire fitments. Tire Rack is a huge company, and you can never be sure who they will dole out that responsibility to within the company. Clearly the person assigned to make the proper tire fitment recommendation in this case is a novice, and/or his recommendation was not double-checked by a supervisor with extensive fitment experience. They simply got that rear tire sizing recommendation wrong.

I have never seen any aftermarket 20x10.5 wheel with a 265/30/20 tire in my entire life. (that's because it's the wrong size )

And that covers hundreds of tire and wheel fitments for European, Japanese and American car and trucks. In the 15 years I have been doing this, I've seen quite a few poor tire & wheel fitment recommendations. (some are outright laughable)

The problem with a company like Tire Rack, is that people naturally assume since they sell this type of product everyday...they MUST know best right?

Wrong.

I abandoned the notion many years ago, that simply because a local shop or internet retailer sells something...that they actually know what they are talking about.

Hands on experience and attention to detail (over a long time period) will make you sharp at this type of thing. Knowing how to properly calculate the clearances you have, and choosing the proper wheel and tire sizes to match those clearances isn't as easy as it looks. There is no formal training available for this type of thing. So you either have to be self-taught, or you learn it from seasoned professional who knows their sh!t. I'm lucky to have a combination of both.

If you go for the BBS CH-R's here is a very solid (risk free) recommendation:

Front: 20 x 9 /w/ 5mm hubcentric spacer for effective an offset of +19mm, 245/30/20 tire.

Rear: 20x10.5 (no spacer required) +24 offset, 295/25/20 tire.

Your wheels or tires will not rub on anything with this configuaration. (guaranteed)

Let me know what you eventually decide to buy.
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