DP 914- What does it take?, Spinning this off from Nat Thread.. Options

[7275914911]

The 2011 Nat thread talk about getting competitive in DP is not the first time I have had thoughts on this. After bringing a "Knife to a Gun Fight" the only 2 times I have competed on the Nat Level (SSM and FP) in my 2056. I am only going to help someone else win tires in that company.

I will be back in Oct in Blythville tho because its in my local region and it's a blast even when you are bringing up the rear!!

Enough rambling back to the topic...
What would a competitive 914 have to look like from top to bottom. What can/can't be done and what can/can't be replaced?

Thoughts/ideas/input are always welcome.....

[jhadler]

A 245 tire on a 7" rim is a waste of an expensive tire. It's not the number on the sidewall that matters, it's the contact patch it makes on the ground that matters.

A 245/50 tire that's shoehorned onto a 7" rim will pinch the sidewalls considerably. Sure, the tire can fit, but much of the tire will actually NOT be contacting the ground. At the next autox you're at, take a look at the stock class cars that cram as much tire possible onto their stock rims. See how the sidewalls bulge? When the sidewalls bulge, the contact patch of the tire lifts off the road surface. On a stock category car, where alignment, suspension, and sway control are limited, the only option left is to regain contact patch lost because of body roll. So that's done by cramming over-sized tires onto stock width rims. But that is an inelegant solution that is much better taken care of once you're allowed to muck about with the suspension and alignment of the car.

For a Prepared category car on radials (where your rim width is limited), you will want the opposite. You want the sidewalls of a radial tire to be as square you reasonably can. Now, in a category such as street prepared, where rim width is unrestricted, you would want to S-T-R-E-T-C-H the tire onto as wide a rim as you can. 275's onto 11" rims are not uncommon.

I second Brit's suggestion of running cantilever tires if you're stuck with 7" rims. ** the cantilever tires were made specifically for cars that have restricted rim widths.

As for your contact patch numbers? I'm not sure where you got them, but a 245/45-16 tire on 8" rims will give you a 9.2" contact patch, not 10.4". That's the contact patch of a 275 tire on a 9" rim. The narrower the rim, the smaller the contact patch for the same tire.

FYI: I'm getting nearly the same contact patch with a 225/45-15 on an 8" rim as a 245/45-16 on the same rim width. 9.0" vs. 9.2" contact patch. As Jake Raby often says..."it's all in the combo". ** and it's lighter, and geared shorter than the 245.

-Josh2