antar at comcast.net
Thu Oct 21 22:33:08 EDT 2004
I understand your cautiousness, but really, 7" is NOT "ALREADY" below the manufacturer's suggestion. 7" is what Audi uses, and they do not manufacture tires. I've looked at several tires that are sized 225-50-16, and their recommended rim width is 6-8", so there's no danger, unless manufacturers want to slit their own throats (I'd say the flop between Firestone and Ford should've put these people on notice).
I felt that 6" was cutting it close, but I don't think they are a danger. As the Yokohama site explains it, you increase the softness of the ride when reducing wheel width, due to the shape of the sidewall. The other extreme will increase the performance (they didn't say safety), but will also increase negative aspects, like ride harshness and tracking on cracks in the road (a symptom of over-responsive steering). Everything really ought to be balanced somewhere in the middle... So 7.5" is actually not ideal; it's making some sacrifices, but not in safety. As long as the tire manuf. approves the size, it's OK. Manufacturers build a decent margin of safety into these ratings to account for extreme conditions, so being very close to the extremities will get you by for a while, but as I mentioned in the first email, you should replace the tires with a better size when they wear out, or even replace the wheels to match the tires. It all depends on $$... I really don't think safety is an issue here (esp. given the manuf. ratings), it's about what the person is looking for and how much they have to spend for that.
From: Larry C Leung <l.leung at juno.com>
Date: 10/21/04 8:39:01 PM
Subject: Re: Wheels
There is an inheritly LARGE difference between a 7" rim and a 6" rim,
7" is ALREADY below what nearly all tire manufacturers suggest as
a minimum rim width for a 225mm width tire, and the car manufacturer
has the luxury and responsibility to test the safety of the combination.
Do you really wish to be the test pilot for this application?
The whole percentage thing is ONLY a guideline, it's not a rule. The
rules are set by the tire manufacturer. Only they truely know the limits
of their tire. In reality, it's really a tire mfg/car mfg combined
although reasonable corner weight info may be enough to confirm
things for the tire mfg alone.
The only application I've seen allowing 225's on 6" rims is on several
DOT R (race) tires, which have a MUCH narrower range of expected
uses and conditions from street tires (but being DOT rated, they have
the same liabilities). Tire manufacturers were forced to make this
work due to at least the SCCA's rules for Solo Stock and Showroom Stock
racing. I rather doubt they'd consider this range ideal for the tire.
no other application allowing this narrow a rim for this wide a tire.
I'd also imagine that this is a rather difficult combination for the tire
wrench to seat properly.
IMHO, it's NOT a good idea, I'd prefer to NOT be driving next to
a car so equipped.
LL - NY, protecting mine (and possibly your own) flanks
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