Best Wheel/Tire size combo

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09-24-2007, 05:17 PM
Shannon1530

OK....new racer question.....I am looking to purchase some wheels for my 80 RX7. I was looking at the diamond racing wheels, since they offer a resonably priced 4x110. They offer both 13" and 14" sizes. Which is better?

Lets say for arguments sake that for all around use, 13" is better. Ok...then what tire size is best?

I know wheel/tire size can change based on which track you are runing and which gear you are running. I am just trying to find a good baseline. Something that might work a little everywhere?

Thanks.
09-24-2007, 05:59 PM
dickita15

I run the 225/45/13s but i do not think they will mount on a diamond. the low profile tire needs a wheel with a larger drop center. some like the taller 50 or 60 series 13" tires and those will fit a diamond.
09-24-2007, 06:11 PM
Shannon1530

dickita15,
What offset are you using?
09-24-2007, 06:17 PM
dickita15

Sorry I honestly don't know.
09-24-2007, 06:19 PM
Shannon1530

Do you have any problems with the 225's rubbing?
09-24-2007, 07:21 PM
dickita15

no problem if you roll the fender lips.
09-25-2007, 07:50 AM
Shannon1530

Why did you choose to run 13" instead of 14"'s? What is the advantage?
09-25-2007, 11:22 AM
mlytle

careful with the diamond an circle racing wheels. from my srx7 experience they are not hub centric, which makes getting them balanced on modern machines challenging. if your shop has the right adaptors it is ok, but i know the racing tire distributor at the track here doesn't not have one and we have had fits with the vibrations from incorrectly balanced steel wheels.
09-25-2007, 04:22 PM
dickita15

Quote:

Why did you choose to run 13" instead of 14"'s? What is the advantage?
[/b]

When I started the rules did not allow the use of larger wheels. With the rules as they are now I considered 15”. After weighing the pros and con I decided to stay with the 13”. I would not go with 14” as they are getting rarer with less tire choices.
09-25-2007, 11:40 PM
ScotMac

Quote:

Why did you choose to run 13" instead of 14"'s? What is the advantage?
[/b]

Assuming you use the same profile on them both, then the 13 is lower weight, lower ride-height, better aero. Only negative is it may screw up the scrub radius.
09-26-2007, 08:14 AM
shwah

I am trying 13s out this weekend for both reasons that ScotMac mentioned. I run big spacers so my scrub radius is jacked up anyway...
10-01-2007, 11:20 AM
Shannon1530

shwah,
How did those wheels work out for you this weekend?
10-01-2007, 01:58 PM
shwah

Race was cancelled late Friday.

We drove up, found out, camped overnight and drove home...

I will be out on them Oct 27/28 at Blackhawk.
10-10-2007, 12:22 PM
Shannon1530

Is anyone using the Diamond Racing wheels? Any problems? What size tire are you using?
10-10-2007, 01:20 PM
mustanghammer

Quote:

Is anyone using the Diamond Racing wheels? Any problems? What size tire are you using?
[/b]

I use them for rain tires - 205/60x13. We have another IT7 driver that uses them with 225/50x13 with no issues. In my experience, they work fine but are hard to balance correctly. I have been thinking about building an adapter that centers the wells on the lug hole or chucking them up in a lathe and truing the hub hole. I have not found the balance as big an issue in the rain because speeds are typically lower. Diamonds are a nice wheel to work from a tire servier's standpoint.

I have 13x7 Panasports for my drys. Expensive but worth it in terms of weight, longevity and the ability to balance them. They are a PIA to service, however.
10-16-2007, 03:26 PM
Dave Damouth

I ran the 13x7" 4 x 110mm, 4" backspacing Spun Diamonds with 225/45/13 Hoosiers for years, no problems.

I'm currently running 13 x 9.5" x 20" slicks on the same rims. No problems.

They are not hubcentric, but if need be you can build an adapter, chuck them in a lathe and make them hubcentric.

With the 225/45/13's, I used so little weight to balance them that I stopped balancing them completely. Couldn't tell the difference, and it simplifies things if you decide to start flipping tires to maximize their life..... The slicks require more weight to balance than the DOT tires did.

The spun version weighs less than 13lbs, and in 10 years I've ruined exactly one rim. It did considerable damage to the nose of the other car before expiring.

If I recall correctly, the Panasports were about 1.5 lbs lighter, 3x the $, and won't take the abuse of the steel wheels.

All of which applies to the 13" rims only. If you go up to 15" rims, the weight differential starts to become more of an issue.