28x10 vs 26x10 contact patch

Well there not much more to say I guess.
You ask the question but the answer you already knew.
Cheers.

 

Well, this thread is helping me think some of it through. I'm still questioning myself and am still a little confused though. The "wrinkle" effect and "rollout" have me perplexed. Seems like a more complex subject than I thought. Oh well, I'll try to do some more research. Thanks for the input everybody.

 

I think I can explane The larger tire has a larger arc radius, the radius contact isn't as sharp as the smaller tire so the contact patch would be slightly bigger with the larger tire.

 

Erick, you are a deep dude! LOL, my head hurts...
Ask yourself this: What do you want from the tires? Maximum hook? (most of us do)

Then I promise you, a taller tire will give you more contact patch. At the same psi. Imagine a go cart tire @ 20psi, and a 33X16 tire @ 20 psi. There is no way they will both have that same contact patch.

Get the 28, and then get those 4.88's, or 5.12's, to rev that baby where she wants to be!

When all else fails, look at NHRA Stock racers...They know how to make small tired, stock suspensioned cars hook. 90% of them run 30 inch tall tires, and then gear accordingly. There is a reason for this...

 

When you're limited in width (by the rules...aka: NHRA Stock Eliminator Cars max width is 9") then go taller to get more contact patch. But here's the real deal on tire size:

Only run as much tire as you need to get the car to hook. Period. If it'll hook on a 26x8.5 then run that. If you can hook on that tire but you go with a 26x10 tire you are only dragging excess carcass down the track. It'll slow you down. The whole "big tire" theory came from bracket racers who wanted to make sure they NEVER spin a tire no matter what track they're running on. Don't overtire the car.

 

Words of wisdom. ^^^^
As far as I'm concerned I'd rather spin than bog any day.

 

Think about it: If a 26x10 tire hooked the same as a 34x17, why do all Pro Stock cars use the bigger tires? Why even make those bigger tires in the first place if they hook the same?

Seriously, a larger tire WILL hook better than a shorter one. The area that is in contact with the track IS larger. No need questioning it because it IS true. Wanna see for yourself? Have your 26x10s on the car, with 10 psi in them. Jack up the back of the car and wet the tires down, but try not to get any water on the pavement underneath. Now, put the car down on the ground. Jack it back up and look at the mark the tire left. Then go find a set of 28x10's and do the same thing. The "patch" will be longer...same width (assuming the 28x10 is exactly the same width) but longer. 10.5 cars run the tallest possible tire (usually around 31" tall).

Back to pressures. Tuning tires isn't rocket science. Start at 20 psi, and work your way down until it starts to become inconsistent in the 60'. Then stop & increase the pressure back up a pound or two. Or you can just put 6 psi in them and go racing, but I'm warning you....that low pressure in a smaller tire (like a 28x10) WILL cause the back of the car to "walk" severely. In our cars (one had 28x9's the other had 28x10.5) we never had to run less than 14 psi. When I had small tires (the 10.5's) I always ran around 16 psi. Car drove itself, no walking, no spinning, nothing. Then again, I wasn't putting down nearly as much power as I am now either. Now I'm up to the 32x14's. I keep them around 11 psi. Less than 8 and the car walks badly and doesn't hook nearly as well.

With the lower pressures, the center of the tire actually lifts off the pavement. To see this, take your car & wet the tires again, then put it down on the floor with like 5 psi in them and roll it forward. You'll see that the center part of the tire is not contacting the pavement as much as the edges.

Now, all this info can be taken with a grain of salt. Some folks have their own way of doing things and they know how their cars work/don't work. I've been working around these things all my life and I've not had a single incident where those above mentioned methods didn't work. To each his own.

 

I never said they would hook the same. There's no question that bigger tires hook better, but it is because the tire can run less pressure.

If you guys think that 2 tires at the same pressure have a different contact area, you are going against scientific fact. At the same pressure (and same weight car) the tires will have the same contact area. Once we all agree on this fact I think we can have a better discussion.

All of the other advice you guys are giving is great though.

 

he asked a question, then gave his answer and tried to change the minds of everyone whose answer didnt agree with his. why would you feel this isnt logical?

 

Air pressure supports the car (the sidewall can support some of the load like a runflat tire, but I don't think slicks have much sidewall support). Air pressure is in psi (pounds per square inch). For a 3000lb car and 30psi tire pressure, the contact area will be the following:

3000lb/30psi=100 square inches, or 25 square inches per tire.

Tire size doesn't effect the contact area, only the shape of the patch.

Now we should probably lock this thread before the truth comes out.

 

Here's my original question that I still don't have an answer to because everyone is hung up on the first part of the post:

"Is it the shape of the contact that changes or is it that a larger diameter tire allows for a lower air pressure due to increased stability?"

...Oh nevermind.

 

People have answered all parts of your question, but you refuse to listen to their answers. Maybe you should call Goodyear or Mickey Thompson and ask them.

 

Okay fellas. this one has degraded into a shouting match. Big tires hook better because they are bigger.
End of story and thread.