[.alex.]

Is their a general rule of thumb about when you are suppose to be going up in size?

power? 60'? trap speed?

 

[jmarkaudio]

You want trap RPM to be just above peak HP, this should net your best ET.

 

[JeffMcKC]

You can run into hook issues with 28's because of the short side wall. Most cars will be faster with a Taller tire than a short one. I have not seen many cars speed up by changing to a short tire, thats why they use them in limited traction classes.

 

[Mike Peters]

You can run into hook issues with 28's because of the short side wall. Most cars will be faster with a Taller tire than a short one. I have not seen many cars speed up by changing to a short tire, thats why they use them in limited traction classes.

Jeff, I was told by M/T tech that if traction was not an issue, the shorter sidewall would be the quicker tire due to the shorter sidewall reacting quicker with less distortion. Is this not why P/S went to a shorter sidewall? True, the taller tire will have a larger footprint given the same treadwidth and should provide more traction if that is an issue.

 

[.alex.]

I have to re gear the car since i am switching from a turbo to a blower. Just trying to decide what tire to get. Traction has not been an issue in the past with a 316/60 radial.

If i run 28's i can also run the 325 radial, the 29.5's get another set of 315's.

 

[stracer859]

Jeff, I was told by M/T tech that if traction was not an issue, the shorter sidewall would be the quicker tire due to the shorter sidewall reacting quicker with less distortion. Is this not why P/S went to a shorter sidewall? True, the taller tire will have a larger footprint given the same treadwidth and should provide more traction if that is an issue.

i found this to be very true, i changed from a 26x8.5 to a 28x10.5 and it killed my car almost 2 tenths. changed back to the little tires and the car is back where it was, i was just assuming the weight of the tire and gearing was what had the effect on my car

 

[McLovin]

going from a 295 to a 325 was a huge difference in traction and gearing needed to be changed to accomodate the shorter tire,once I went back to the taller tire with the 325 gearing it was a pig.....excpect to make a gear change

 

[JeffMcKC]

Being a Drag Radial, it will not liked to be shocked if you have a tighter sidewall and its shocked to hard, it will go into shake, key is if you have a traction issue the taller side wall will help. I believe this was his question about when to know if you should step up the rollout of the tire.

With any car you should run the correct gear for your final drive, taking the cars tires into account taller tire means more gear to end up with same final drive ratio.

On my car distortion is not a problem, because you run so much air with a radial and go up if it does shake. Without a shake problem, mine is still faster with the 295's than the 325's which is wider and shorter, the tall tire hooks just as hard, even though the tread is smaller, but the shorter side wall will give a better reaction time.

 

[.alex.]

I think i will move up to the taller tire and run a 4.10 gear with the blower. the car curretnly has 3.55's and they wont cut it no matter what tire i go with.