17 replies to this topic

[Tom Sager]

I've noticed a number of my SM7 tires/wheels aren't as "round" as I'd like them to be.  While spinning the wheels on the car I'm noticing what looks like a flat spot or out of round area in some of the tires.  I'd say it's about a .100" deviation from round in a single spot and that's large enough that it would be visible to the eye as a flat spot if it were a flat spot due to locking a wheel.  No visible evidence of a flat spot in the tread.  It also does not seem to correspond to a bent spot in the wheel so I think in a few cases it's the tires. 

 

I've often felt that the wheels and tires we buy aren't as round as they should be.  I see some run out in both when they are new but what I see now from some of the used tires is more than what I would consider "normal".  Does anyone know if there might be a seam in the construction of the SM7 that might move a bit after use?  Anyone else notice the same thing or have a comment?

 

I do have a few bent wheels that need replacing and if anyone is a fan of a particular brand of wheel that they feel is very round, strong and light, I'm all ears.  I've been running D-Force in recent years. 

[Danny Steyn]

Tom, what I find amazing is how out-of-round brand new sticker tires are until we have a few laps put into them. At the NASA champs I swore my wheels were bent until about the third lap when the Toyos finally came up to pressure and started being less square than when they were mounted

[Michael Novak]

Tom

 

Do you see it only cold, as they change alot when they warm up. We have a tire balancer that has Road load also and it can detect these type of problems--overall they are pretty good...

[FTodaro]

I have a tire machine and have mounted and balanced several SM7 tires. if they are on the car sitting in one spot they will conform to the pressure, but fresh mounted tires, i have found to be pretty good over all. The worst  tires are shaved as the shaving process is not perfect.

[Ron Alan]

Pulled a car out of the trailer after a month to change transmisson...car on jackstands I spun the wheels out of habit(10 cycle SM7). All 4 where flat spotted...almost identical.  Then I realize it was all the spots the car had been sitting on! 

 

Edit...at least it appeared that was the issue! Will find out next session

[Rob Burgoon]

Pulled a car out of the trailer after a month to change transmisson...car on jackstands I spun the wheels out of habit(10 cycle SM7). All 4 where flat spotted...almost identical.  Then I realize it was all the spots the car had been sitting on! 

 

Bias ply tires do that worse I've heard.

[Tom Sager]

Tom, what I find amazing is how out-of-round brand new sticker tires are until we have a few laps put into them. At the NASA champs I swore my wheels were bent until about the third lap when the Toyos finally came up to pressure and started being less square than when they were mounted

I have noticed that also with new tires but once run-in they typically behave well meaning no shake or vibration.  Last time out swapping some tires around and having a few re-balanced at the track I still had a significant shake in the steering wheel throughout a couple sessions.  That led me to look more closely at tires and wheels it's amazing how not round everything looks.

 

Anyone have a wheel brand they really like for being round and light and strong?

[Tom Sager]

Tom

 

Do you see it only cold, as they change alot when they warm up. We have a tire balancer that has Road load also and it can detect these type of problems--overall they are pretty good...

Would that machine be a Hunter Roadforce type?  I may try to find a shop locally with something like this.

[Marc Cefalo]

Tom, what I find amazing is how out-of-round brand new sticker tires are until we have a few laps put into them. At the NASA champs I swore my wheels were bent until about the third lap when the Toyos finally came up to pressure and started being less square than when they were mounted

danny, were your toyos shaved?  sticker toyos feel terrible until they are warmed up and scuffed in.   feels like the wheels are octagons.  if shaved no issues right out of the box but at the glen i wonder still if unshaved was truly the way to go....

[Michael Novak]

Would that machine be a Hunter Roadforce type?  I may try to find a shop locally with something like this.

Yes.

[Danny Steyn]

danny, were your toyos shaved?  sticker toyos feel terrible until they are warmed up and scuffed in.   feels like the wheels are octagons.  if shaved no issues right out of the box but at the glen i wonder still if unshaved was truly the way to go....

 

Marc - I was on unshaved. In test day and practice sessions I ran a variety of tires, old and stickers, and kept running the stickers until around 5-6 HC where they seemed to be their best. For the race I went back to 9HC old tires and they really worked for me. Both Chris Haldeman and Tyler Kicera were running shaved. But you had to be careful how you brought the shaved up to temp. In my7 experience, shaved TOYOS are not good in their first session and do need at least 1 HC and time to cure, before they are at their best. With Toyos, my experience is that If you go out and race hard immediately on stickers or shaved sticker, I find that they are easy to grain, and then they are toast.  Others might have different experiences.

 

And yes, all my sticker tires felt square the first few laps. BEgs the question how are they being stored?

[davew]

We have mounted about 600 SM7's this year. I have not had any experience with Toyo's since they where the SCCA tire.

 

Every year we find a couple of Hoosiers that want 5-8 ounces of weight. Flip the tire, same thing. Rotate it around the wheel, same thing. Put a different tire on that wheel and it balances fine. Hoosier has always simply replaced the tire without complaint, with apologies. That is less than a 0.5% problem rate, well within my margin of error.

[Justin Casey]

Anyone have a wheel brand they really like for being round and light and strong?

 

I've had good luck over several seasons with the common Team Dynamic ProRace 1.2's. They are ~13.4-13.6 pounds depending on finish. I've maybe bent one full set of wheels after 3 seasons from my own doing (had a bad off or was forced to hit a curb).

 

I recently acquired Version 4? of the 949racing spec miata 6UL's. I haven't weighed them yet but they claim to be exactly 13 pounds. They held up fine in the 45 minute championship race at Buttonwillow. We'll see how they last moving forward.

[Tom Sager]

I have a lot of experience ( 30 years with an OE) with tire uniformity issue.  If the flat spots were not caused by a wheel lock up, they are likely cold flat spots.  If you wnat to road force a Hoosier tire, you have to put the car on jack stands while they are warm.  I have mounted, road forced and balanced a lot of Hoosiers.  The Radial First Harmonic RF1 isn't very good as compared to an OE tire but good enough for a race car.  I have notice an a very small percentage that needs excessive weight as mention by Dave Wheeler.  Check the same tires after a run session and they will likely be round.

 

My car is up on jack stands for a transmission.  Spinning the wheels I can see a noticeable flat spot.  The car came off the track after a race (after impound) and went in the trailer for a few weeks.  I know the tires were round when I mounted them.  If you don't have a noticeable vibration, you are fine. 

Good info.  I did for a couple events have a vibration or worse "shake" issue.  Have been going through all the wheels, tires and checking the car.  One by one I've weeded out some problems with all of the above and last time at the track the car felt pretty good.

[Tom Sager]

I've had good luck over several seasons with the common Team Dynamic ProRace 1.2's. They are ~13.4-13.6 pounds depending on finish. I've maybe bent one full set of wheels after 3 seasons from my own doing (had a bad off or was forced to hit a curb).

 

I recently acquired Version 4? of the 949racing spec miata 6UL's. I haven't weighed them yet but they claim to be exactly 13 pounds. They held up fine in the 45 minute championship race at Buttonwillow. We'll see how they last moving forward.

The 949's sound interesting and Momo's have been recommended. 

[davew]

I have been selling wheels for Spec Miatas for about 15 years. For the last few years we have been using the MOMO Podium wheels. The price is right and they have shown to be very durable. I have seen only 1 bent wheel from curbs/potholes since I have been selling these wheels. Other un-named wheels had a reputation for bending inner lips, causing a hop and vibration. I weighed a MOMO the other day at 13.3 pounds on my digital postal scale. That weight included the center cap. Just the wheel should be within a few ounces of minimum weight.

 

Your mileage may vary

Dave

[steveracer]

I have a stack of "9" wheels with bent inner beads...not buying any more of them.