None of that happens.
FWIW, on the ES100, the 7" is not the "nominal" (whatever that means), it's
the Spec width, which means that's the width that they use to measure the
tire dimensions.
Going to an 8" width does NOT "force the carcass". In fact, that setup on my
911 was back to the stock factory setup (225/50/16 on 16x8" wheels in the
rear, as well as 205/55/16 on 16x6" on the front). Look at the section width
(8.9" for the 55, 9.1" for the 50) and the tread width (8.3") for the ES100
225 tires. There is nothing being forced anywhere with an 8" rim.
When mfrs spec a rim they also think of ride comfort as a trade-off to
performance, like they did allowing a 225/55/16 on a 16x6.5" rim on the Gen
3 SHO. An 8" rim on a 225 tire, which is still under the section and tread
width, is still an ideal setup.
It does NOT cause "aggressive shoulder wear, "under" wear in the center of
the footprint, an offset footprint, and carcass deformation (which can lead
to separation)". In a similar vein, my current 215/45/17s on a 17x7.5" rim
are nicely worn evenly across after four very hard track days, and 20K+ road
miles
Ron Porter
-----Original Message-----
From: FlamingTaco [mailto:flamingtaco@earthlink.net]
Sent: Tuesday, July 25, 2006 5:21 PM
To: ronporter@ameritech.net; shotimes@autox.team.net
Subject: RE: [Shotimes] Thoughts on Kumho Ecsta 711s
I'm not too familiar with yokohama, but your own findings match what you'll
see if you look through BFG/Goodyear/Michelin et al. The recommended tire
width for the ES 100 225/50-16 is not a MINIMUM 7", but a NOMINAL 7". IOW,
the tires were designed to be mounted on a 7" rim. The MAXIMUM range for the
tires is 6-8".
Your "improvement" is due to gaining more section width by forcing the
carcass to push the shoulders towards the foot-print. There are trade-offs
in doing this, though, namely agressive shoulder wear, "under" wear in the
center of the footprint, an offset footprint, and carcass deformation (which
can lead to separation).
While I'm not against using extreme tire/wheel combinations for track use, I
will not recommend mounting a tire at either extreme of it's recommended
range for a daily driver, be it warranteed or not. 1/2" either side of
nominal is the max one should go with to preserve longevity and the tire's
designed performance parameters.
I have seen enough "periodically tracked" 6-8" range tires mounted on 8"
rims separate or blow the sidewall to know that mounting a tire at it's
extremes, then driving it to it's extremes is pushing the tire too far. Not
so many problems with vehicles seeing street-only use, but many shops do not
like mounting 225's less than 60 on anything wider than 7.5". Since they are
under pressure to limit failure returns, I've got to put some credence in
their experiece as well.
David
-----Original Message-----
>From: Ron Porter <ronporter@ameritech.net>
>Sent: Jul 25, 2006 4:08 PM
>To: shotimes@autox.team.net
>Subject: RE: [Shotimes] Thoughts on Kumho Ecsta 711s
>
>Nope. I first learned this a few years back on the 911, when I went from
the
>245/45/16 on 16x8 rims (I bought it with that) to a 225/50/16 on those
rims.
>EVERYTHING improved.
>
>Look at the specs for most 225 50 or 55 tires. Tread widths are around 8",
>and the spec rim will be at least 7", with a 7-9" rim range.
>
>An 8" rim is the best for a 225 tire from my experience, just as the 7.5"
>rim is perfect for the 215/45 tires I run now.
>
>As an example, a typical S tire is the ES100 Yoko, I either 225/50 or
225/55
>size. Here's the Tire Rack specs:
>
>225/50 WR16
> 92W SL 280 AA A
> 1389 lbs.
> 44 psi
> 10/32"
> 23 lbs.
>6-8"
> 7"
> 8.9"
> 8.3"
> 25"
> 829
>
>225/55 WR16
> 95W SL 280 AA A
> 1521 lbs.
> 44 psi
> 10/32"
> 24 lbs.
>6-8"
> 7"
> 9.1"
> 8.3"
> 25.8"
> 805
>
>The design spec rim is 7", but the tread width is 8.3", with a rim
>recommendation of 6-8". I can tell you that the 225/55 does not work very
>optimally on a 6" slicer. 7" is fine, but 8" is the optimal for handling.
>
>Ron Porter
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