About tire size & performance

[MoshimoGTP]

I have a 225/60/R16 stock size. I want 245/60/R16, that tire size can affect the performance of my GTP on the street or on the raceway?maybe 245/50 or 225/50 a better choice?. What are the beneffits or problems with those tire sizes.??

Thanks

[Ripn12s]

Only thing I can say is that the smaller sidewall along w/ 16 inch rims will make the wheel gap look even worse then it is already.

try www.clubgp.com for other thoughts

[sonhasteg]

Wider the better as far as traction goes, but you need wider rims to be effective. The majority opinion is that the widest "effective" tire width on the stock rim is a 235. I have heard of a 255 being squeezed onto the stock rim, but would not suggest it. Most go with a 245 width.

A shorter diameter tire will increase excelleration slightly. Too short and you'll run into problems with the computer.

Shorter sidewalls will increase handling, but at the cost of a harsher ride.

http://www.miata.net/garage/tirecalc.html
Here's a site that has a tire size calculator...if you can't get to it here is the tire sizes you have questions about.

Specification Sidewall Radius Diameter Circumference Revs/Mile
225/60-16 5.3in 13.3in 26.6in 83.7in 757 (stock)
245/60-16 5.8in 13.8in 27.6in 86.6in 731 (3.5%)
245/50-16 4.8in 12.8in 25.6in 80.6in 786 (-3.7%)
225/50-16 4.4in 12.4in 24.9in 78.1in 811 (-6.7%)

As you can see 245/60-16 is an inch taller and the 245/50-16 is an inch shorter. Shouldn't be enough of a difference to be a problem (except your speedo will be off by the above %). The 225/60-16 is almost 2 inches shorter. Besides increasing the wheel gap I would suspect that this would set a low pressure warning light and may even be enough to change shift points.

Here's an exact match for the stock diameter and cicumference, but obviously it would require 17" rims...

Specification Sidewall Radius Diameter Circumference Revs/Mile
245/50-17 4.8in 13.3in 26.6in 83.7in 757

[MoshimoGTP]

Today i bought the 235/55-R16 Goodyear. I hope this don't affect me on performance. I have noticed with this tires my car don't slips like before.

Suggestions? Questions?

Thanks a lot!

[justinarm]

How important is speed rating on tires? I have Bridgestone RE910 with a T rating of 118 mph. If I have the correct tire pressure, would it be o.k. to go around ~140? I know this isn't very safe, but would a tire blow out? Many GP's have the speed limiter removed and have regular tires and go around 140 sometimes. What do you guys think?

[i3o2Matt]

wat the speed rating is where the tire loses its traction...it still grips, but not very well at all...

[justinarm]

But does it have a greater risk of blowing out?

[kilroypr]

Yes it does, the speed rating tells you basically that the sidewalls can handle air pressure, torsion and temperatures at speeds equal or less than the speed rating. If you drive a tire past it's speed rating the sidewall becomes too soft and could bent easily if the steering is turned abrubptly or could explode easier due to the softer than normal sidewall texture at that higher than rated speed.

I am looking for a gadget they sell for trucks that depending on the tire diameter it corrects the speedo reading. Let me check if it is available for cars and if that is the case then the tire diameter would not mess your tranny changes points.

Here is the gadget for trucks, I need to find out if there is a counterpart for cars.

http://www.jcwhitney.com/webapp/wcs/...&storeId=10101

http://mikeegan.stormpages.com/Tru.html

http://www.superlift.com/33002I_1.pdf

http://www.superlift.com/print/insta.../33002IN_1.pdf

ALl the links that I have found point just to truck applications. But it would not hurt to ask the manufacturer if a version for automobiles could be available.

[justinarm]

Thanks for the excellent reply kilroypr!

[MoshimoGTP]

What about tire press on 235/55/16. In front i have 30 lbs and rear 28 lbs. But i noticed the front tires like than less 30lbs. I need to put more press to my front tires???... Suggestions?