Bridgestone Announces Large Diameter Narrow Tires

[Xist]

I have been wondering for a while how prohibitively expensive it would be to have custom rims made--I had been concerned with something with a blank face, round like a moon disc or flat like a pizza pan, but something that will not fall off as you go around a corner.

I cannot imagine breaking even on the design, but I think that it would be easier to have custom rims made than tires.

[Frank Lee]

Originally Posted by niky

Close enough for government work, as long as the tires are of the same type, construction and height.

No, really- it's not close enough for anything.


I wonder how the r.r. compares to that of the classic 155R15- say, the ubiquitous Pirelli radial- commonly found on old VWs?

[Xist]

Originally Posted by Frank Lee

No, really- it's not close enough for anything.

Isn't government work a myth? Is that like saying "close enough for a monopole magnet?"

[niky]

For what tires? From some of the data I've seen, the contact patch size remains fairly constant at regular pressures (as opposed to woefully underinflated) for tires of similar construction but differing widths.

I'm willing to accept that a wider tire might put more rubber down on the road due to differences in construction, but I have never come across any hard data for it. I'd genuinely like to find out why (part of why I signed on this site) because I hate not knowing. I'd rather not be spreading false information in my writing if I'm wrong.

[Frank Lee]

I looked into contact patches once upon a time and found data disputing the idea that the contact patch basically can be used to gauge the weight on the tire if the psi is known. Then I did my own experiment of measuring contact patch size at varying psis; the correlation was quite poor.

[niky]

The contact patch on a radial doesn't deform that much compared to older tires, but what about the correlation between patches at the same pressure on different tire widths?

[NeilBlanchard]

We don't know the outside diameter of these tires, but if the raw math is close - 155mm x 55% = 85.25mm = 3.3562992" x 2 = 6.7125984" + 19" = ~25.7"

So they are only a bit larger diameter than a 195 60 15 which is 24.2" by the same math.

Yes, a 19" diameter rim that is about 5" wide (the tire is about 6.1" wide) would be key - hopefully it would be smooth and flat so the low rolling resistance wouldn't be wasted by aero drag!

[CapriRacer]

Fuel for the fire:

http://www.performancesimulations.co...on-tires-1.htm

Explains why race cars use wide tires.

So - No - the contact patch is not the same with the same pressure and load.

Oh, and tires do NOT behave according to classical friction theory. Tires generate their highest grip at 10% to 15% slip.

[shovel]

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.

[UFO]

Originally Posted by CapriRacer

Fuel for the fire:

Fact or Fiction? Tire contact patch and air pressure.

Explains why race cars use wide tires.

So - No - the contact patch is not the same with the same pressure and load.

Oh, and tires do NOT behave according to classical friction theory. Tires generate their highest grip at 10% to 15% slip.

Nothing wrong with the classical friction theory, just that there are more factors at work when considering tire performance.