PBJT

Is there a market on tire futures? I should invest in them.

brad@tirerack.com

After 13 years of this, if there is I WANT IN!

ExMB

Joe Weinstein

Hi Damon, can I ask you to suggest a new technical TireRack test to
help racers get the best tire?

I would pay good money to know whether a wider tire, always performs
better than a narrower one, on the same rim. I hear lots of anecdotal
evidence that if the tire has a stiff sidewall, a narrower tire that is perfect
for the rim (the sidewalls are far enough apart at the bead to keep the
sidewalls vertical or even a little out) will stick better than a one-size-
wider tire whose sidewalls get pinched in by the rim.

Thanks for being on the forum!
Joe

DeerHunter

In the Miata world, extensive testing (and personal experience) show that, within reason, a wider wheel will better support any given tire size and performance will benefit. On the street, I moved from a 6 inch-wide wheel to 8 inches (for a 205 tire) and grip not only improved but became more usable (i.e. you can drive more towards the ragged edge of grip, find the limit and keep the car within that narrow band of traction). Admittedly, that's an extreme change.

The track junkies (of which I'm one) found that moving from an 8 inch-wide rim to 9 inches (for a 225 tire) improved lap times significantly (1-2 seconds on a 2-3 minute track). Again, not only more grip, but more usable grip. With the availability of 245 section width grippy tires (which are wide for a Miata), the move is now to use 10 inch and even 11 inch-wide rims, with similar improvements. I haven't done this, as it requires hacking up the fenders and installing flares.

So, while I have no hard data for the Porsche world, I suspect the same rule-of-thumb will hold true.

webweaver

Joe was asking about the difference between wider and narrower tires on the same rim.

Joe Weinstein

Yep. My class doesn't allow rim width changes, so for instance is it better
to run a 245/35 on the 8.5 rim, or the 255/40?

For the old bias-plied tires, and even for Hoosier DOT-Rs, they tolerate and
work on narrow rims, I've seen 315s crammed onto 9.5" rims, but the
trend for more normal radial street tires is to not pinch. Just super curious
whether the 255 works on its narrowest-spec rim and an 8.9" tread width,
vs. the 245/35 which will be closer to the sweetspot, but maybe drop 0.5"
of tread width... And the taller 255 would induce more push, and make the
ABS think the wheel is slower, so take braking off the front? Pondering...
I think that unless the 245 comes in over-narrow in tread width, I think it
will be the way to go...

DeerHunter

I just assumed that one could extrapolate. Okay, to clarify: Based on experience in the Miata world, a narrower tire on a rim slightly wider than the tread width (which will pull the sidewalls out slightly from the tread) is faster than a wider tire on the same width rim that ends up with pinched (or even completely vertical) sidewalls. Look up the tread width of the tire you're considering and compare it to the rim width. If the tread is wider than the rim, you'll probably lose performance over a narrower tire.

zweebach

I recall reading somewhere once that the best performance of a tire was generally obtained when the tire tread width is 90% of the wheel width. The Miata example seems to prove this out.

GrantG

I think Hoosier recommends an exact (or as close as possible, but no more than 1" off) match between tread and wheel widths.

brad@tirerack.com

Update for those who have them on order: The front 245 is in stock, and the rear 295's are in the US. Bridgestone is presently distributing them to their warehouses for delivery to ours. If you would like to get a set on order please contact me. Thanks.

Joe Weinstein

Hi Damon! Is there a typical tire flow from Bridgestone? How frequently do
they add more to the pipeline? Is it constant or large batches?

If I wanted my set in mid/late January, for instance, what's the likelihood that:

1 - The tires I got then would be from this first batch anyway, if there was any left?
2 - The tires then would be from a newer shipment?

Thanks,
Joe

brad@tirerack.com

The 245 size has been delivered now from a few production runs. The 295 is a brand new size that is just now coming in for the first time. The question is a bit speculative for any future purchases, but I would suspect an order in January would likely come from this shipment. At this time we expect to have enough come in to cover present back orders and have more left for future orders. I can't say how many orders for them there will be between now and then, but hopefully they see how well the demand is for these sizes, and keep them coming as a result. They are produced in Japan.

Joe Weinstein

Gotcha.

So, how much would you want down now, in order to guarantee me a 4-tire
set on January 15th? Full price I guess? And if I balked at that my option would
be to keep checking the tirerack site for availability, and if it ever seems low
I have to jump in. Sound right?

brad@tirerack.com

We need to ship or cancel an in-stock order within 10 days of placing. Just check back when closer to needing.