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Old 03-14-2013, 01:08 AM   #31 (permalink)
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And apparently, to the rest.

The question has got me thinking, though, and I'm looking for data regarding it. Very hard to find data for mixed tire sizes of the same type. I was aware that for different tires, the contact patch size will change due to differences in construction and tread softness/hardness... but I'm wondering if the pressure/weight correlation is more constant for tires made to the same specifications in different sizes.

It's been fun looking, but the best documents I can find are hidden in the DOT databases and my browser is having a devil of a time downloading them.

Also found some interesting data on how wider rims might not just stiffen sidewalls, providing better performance, but also fundamentally change the shape of the tire, changing the contact patch itself.

Flo Cycling Blog: FLO Cyling - The Contact Patch... Why Wider is Better

Research for research's sake is fun.

Again, though... I wonder if Bridgestone will be releasing wheels to go with those tires, and if we can get them in other sizes, too.

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Old 03-14-2013, 01:36 AM   #32 (permalink)
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Interesting link, but I take issue with the psi/area thing, and also the 19.1mm @ 80 and 120 psi tests seem to be botched with wildly varying results that the wide rims didn't suffer.

P.S. The bar graphs comparing patch profiles are- perhaps inadvertently- quite deceptive, having the appearance of greatly magnifying the differences between standard and wide rim contact patches. Even when you take the numerical values into account, the bars' proportions are hard to ignore.
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Old 03-14-2013, 03:19 AM   #33 (permalink)
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Yeah... wobbly there... but it points out an interesting direction for further study. In automobiles, it's quite common to stretch tires over wider rims for better performance. Heck, Jaguar did it with the new XFR-S... same tires as the XFR, but inch-wider rims.

I'm just wondering if anybody has ever tried to quantify the change in contact patch due to the change in wheel size, aside from this. Most data regarding this is anecdotal, at best, and I've read lots of theories about why stretch is effective, but nobody else seems to have looked at the contact patches. Still looking.
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Old 03-14-2013, 01:11 PM   #34 (permalink)
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Quote:
Originally Posted by shovel View Post
Being an off-highway/off-pavement driver I often lament the absence of tall narrow tires for rough terrain. There are a couple 33x9.50x15" models out there that perform fantastically (that's a flotation size, it would be like 240/90R15 in metric) - and the closest I can find to fit my own 4wd vehicle is 235/85R16, still not bad in tall skinnies. Off pavement, a tall sidewall and skinny tread presents much less resistance in soft soil/sand/mud and about the same loft at low speeds. They're not popular since most 4x4's are used to show off and look tough, and the common perception is that wide tires = more traction. Wide tires do protect the vehicle body a bit more off-highway, and somewhat widen the line a vehicle can drive on extreme terrain - won't see skinnies on a rock-crawler any time soon. For a vehicle taken camping and on long distance treks where all forms of terrain are expected, refueling stations are far apart and adrenaline isn't on the menu, tall skinnies are the ticket. Less air drag on the highway, too... fuel isn't free and 4wd's tend to expose a lot of tire to the air, fore and aft.

I wouldn't mind at all if tall skinnies became the next trend and widely available.
One thing about wider off road tires is that you can air them down lower, which allows them to conform to the terain better which then gives you more traction. Also at lower pressures wider tires will compact the soil less leading to less erosion. It has also been my expierience that wide tires at low pressures on a light 4X4 will float on top of the deep sand instead of sinking into it meaning less traction is needed. Of course the key here is a difference in trail pressure vs road pressures.
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Old 03-14-2013, 02:50 PM   #35 (permalink)
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This is an awesome tire.

Drag racers have been confounding physicists since the 1950's.

It's an amazement to me that the thread got to 4 pages without someone pointing out the obvious. Here's a Frank Curtis roadster with 19" Chrysler wire wheels:


MG roadsters used 19" wheels. Moon makes disks from 10" to 46". The Radir 12-spoke spindle mount wheel is 18x3"—bummer.
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Old 03-14-2013, 03:20 PM   #36 (permalink)
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A Mr. Moneypants could order custom billet aero-wheels for those new Bridgestone rubber.
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Old 03-15-2013, 04:13 PM   #37 (permalink)
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Quote:
Originally Posted by rmay635703 View Post
I still rather have 155/90 r12/13/14 or 15
I've never heard of a 90% ratio, except for 18/19" doughnuts.
What are these ?
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Old 03-15-2013, 05:48 PM   #38 (permalink)
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Comfort be dammed! I'd like to see tires with NO sidewall. Just the inch and a half thick tread fixed onto the rim. Then there'd be practically no rolling resistance.
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Old 03-15-2013, 06:01 PM   #39 (permalink)
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Quote:
Originally Posted by HypermilerAX View Post
I've never heard of a 90% ratio, except for 18/19" doughnuts.
What are these ?
There were even a few that are technically 100%, they are NOT metric and fell under the old dimensional standards SR's came close to that, the only tires like that now are floatation tires and they don't say 90 on them anywhere just a bunch of inch measurements.
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Old 03-15-2013, 11:04 PM   #40 (permalink)
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botsapper -- There's always someone ready to take your money. I'd compare the off-the-shelf Centerline Convo Pro Aluminum wheel (15x4 is 9.64lbs). The corrugations in the rim are so they can use less material.

Light Wheels Vs Heavy Wheels - Wheel Tech - Comparison - Car Craft

sheepdog 44 -- HowStuffWorks "How the Tweel Airless Tire Works"



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