Where Should I Have Tires Mounted?

[LE] Acura dealers do not necessarily have the same high-end tire mounting equipment as places who specialize in that work. The first (and last) time I had my tires done at the dealer it was a major struggle with their equipment to dismount the 245/40-17's on the rear. The poor mechanic was sweating, filthy, and seriously bruised by the time he got it off. Then during an epic battle to mount the new tire, their mounting machine *broke*.

So they ran my tire/rim down the street to a tire shop and were back in 10-15 minutes with it nicely mounted and balanced. They said that they just didn't have the right equipment to handle such low profile tires at the dealership. In the interest of maintaining a good relationship with these guys, I've been taking my tires to a good tire shop ever since that first episode.

[TG] My two cents worth as someone with dealership experience (from both sides of the fence).

Most older dealers do not have the equipment to dismount and mount NSX tires nor do they have equipment to do alignments (tire width, ground clearance). As I said "Most" not all. This equipment is very expensive and some dealers my not find it cost effective. If you are dealing with a Newer Dealership or one that is updating there equipment they can probably help you out, on the other hand if you are dealing with a dealer that has been around a while they may not.

My local dealer doesn't have the equipment to handle NSX work in-house however they will take your car in the morning and you can pick it up that afternoon. If your using a tire cert. they do the alignment and mount and balance the tires (no charge). If you need tires or an alignment they will give you the option of several places to go or drop your car off and they will handle it (at no additional charge).

Basically ask your dealer up front.

[MCA]  The higher-end Hunter machines can do these without breaking a sweat... I watched a guy demo these for me... with one hand he removed / remounted an 18-inch RUN-FLAT C5 tire in about 5-7 minutes. The stiffness of the 2-inch run-flat sidewall on this is beyond the "stand on it and work the pry bars" technique that the corner mom-and-pop tire shop might use..

I'd suggest going to a specialist... most shops should be able to handle the 16" front okay, but the 17" rear might be difficult... I run 35-series 18" rears, and this limits my mounting and alignment choices.

[RBA] I had chromed TSW Evo's, and Discount Tire charged me $65 to pull the old tires, put the new ones on, and balance - ALL FOUR WHEELS. No damage done to the rims, either.

Most of the guys down here in Houston go to NTB or Discount for all their tire-related maintenance and have had no problems to my knowledge, for what it's worth...

What Are Those Dots On The Sidewall?

[AWN] The red dot indicates the point of maximum force-variation; it should be aligned with the point on the wheel that's physically lowest.

Usually, wheel manufacturers will drill the valve-stem hole at the lowest point on the wheel, so you should align the red dot with the valve stem.

[GM] From the Yokohama booklet about the OEM AO22H1's that came with my car: The RED dot is to be used as the location for measuring tread wear. "When the indicators show, tires must be replaced."

The YELLOW dot indicates the lightest part of the tire, also known as "maximum force variation." This should be lined up with the heaviest part of the wheel - the valve stem. They call this "phase aligning" the tire.

[SS]  The yellow spot (light) should be mounted on the heavy spot (valve stem) on the wheel. In which case the red dot would be the high point on the tire, and wear the fastest, indicating the need for replacement sooner that other places on the tread. OR The red spot (high) should be mounted on the low spot (valve stem) on the wheel.

Balancing Equipment

[KS - 2001/2/22] In addition to their 611 alignment system, Hunter also makes a state of the art wheel balancing system called the GSP9700 Vibration Control System. On their website, they provide the ability to locate a shop that has the GSP9700. The website address is http://www.gsp9700.com/pub/search/findgsp9700.cfm  

How Should The Wheels Be Balanced?

[AT] In balancing, the terms static (fixed,non-moving) versus dynamic (moving) have really nothing to do with the types of weights or how they are attached. Your spin balancing machines are dynamically balancing the tire and the rim. The computer program in the machine then tells the operator how much weight to use and where it should be placed on the rim. This process can also be done with the tire on the car. This will now take into account other moving parts in the suspension and the whole thing is balanced as a unit. The only problem with this is that the tire/rim setup is now married to that corner of the car. You can't even remove the tire, turn it and mount it in a different position from what it was balanced at. These two types of balancing techniques are dynamic, ie., the tire/rim is moving while the devices determine where the tire is out of balance. The type of weights used, sticky backed or banged-on as you call them, are really not important except for the ease to the operator or equipment doing the work. I've seen sticky backed weights mounted on a rim in the same area where a bang-on type of weight would also work just as effectively. Like Harry has mentioned, I prefer the sticky backed weights because they do less-to-no damage to the rim when mounted. In addition, if the machine being used tells the operator that the best place for the weight is somewhere near the center of the inside of the rim, then bang-on weights can't be used. Sometimes it's also in more than one spot and so a combination of strategies can be used, but usually the stick-on weights will work for most situations.

Static balancing, which is rarely used today because of the demand of the new tires, has the tire being weighed on a bubble type scale or mechanism which senses where the heavy spot of a tire is. This is an average weight and area for the total weight needed. This type of balancing lends itself to bang-on type of weights mainly for the ease to the operator in putting them on with the speed of doing the job. Now I will have to say that I'm not totally sure how a car factory which is mounting and balancing tires through the use of highly automated equipment, which probably have little human input, does this process. I don't know if that technique is considered static, dynamic or something in-between.

A final note on dynamic balancing and sticky-backed weights. I had this done to my 15" front and 16" rear early 1991 rims using autocross RT1's. This seemed to work fine for a short time but I did notice that I had some weight on the inside area near one of the spokes. I also noticed that I had very little clearance between these weights and the front brake caliper. Well after one autocross, I had to back away from another contestant's car while in the grid area and I heard this terrible crunching noise. It sounded like I broke something in the front end. Checked the car out and couldn't find anything wrong. Later when I drove the car home I noticed a severe vibration coming from the front while doing 55mph. I later found out when changing tires to the 94 street sizes, that the weights had started to come loose on the front and then hit the caliper while I was backing up. This peeled them right off and they fell off when I started driving forward. No damage to the car but it put a minor scare into me for a short time. So if you have to use sticky weights, and are using the early rims for the NSX, make sure that the weights are not going to interfere with the front brake calipers. You have very little clearance there.

[AWN] Clip-on weights SUCK. There is NO WAY I'd let anyone put them on my wheels... Inside OR outside. Stick-on weights on the inside of each rim are fine on the NSX (or any car with similar wheel offsets). You only need weights on both the inside and outside edges of the rim on wheels with offsets more negative than those on the NSX wheels.

Distributing the weights on both inside and outside edges of the rim can make a HUGE difference, mostly because static balance is different from dynamic balance. Imagine a simplified version of an unbalanced wheel; visualize it as a pair of unequal weights connected by a bar, with a hole drilled through the midpoint of the bar.

Obviously, the thing's out of balance. The light side needs 99 more pounds of weight, right? Ok, add 99 pounds. Let's say that we add the weight to just one side of the wheel:

The perspective is a little odd-looking here, so let me draw a simple side view:

See what happens? If you do a static balance check on this "wheel" by balancing it at its pivot point, it will appear to be perfectly balanced:

If you SPIN the "wheel" around its pivot point, though, you'll see that it's actually way OUT of balance; the 99-pound weight will try real hard to be collinear with the 100-pound weight and the 1-lb weight, and it'll make the "wheel" wobble as it spins.

If you'd balanced the "wheel" by adding TWO 49.5-pound weights, one on each side of the 1-pound weight, the wheel would balance both statically AND dynamically. Here's a side view (those perspective views were a bitch to draw) of the proper way:

See? Now the wheel's stable.