How much weight is normal to balance new 20" wheels?

eyeguy · #1 02-03-2010, 11:14 PM

Just had some new Vredesteins mounted on OEM 214's today. Tirerack recommended the install shop with good feedback, Hunter balancing gear, etc and the crew was great and let me observe the entire process. One wheel required over 7 ounces of weight to balance - the others needed about 2 oz. The machine showed no visible wobble and the computer did not recommend remounting/error, etc.

My question: is 7 oz of balancing weights (strip adhesive weights on inside of rim of course) unusual? The 20" 214 and tire is quite heavy...

Thanks

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Penguin · #2 02-03-2010, 11:51 PM

Tire Rack says about 1/2 of one percent, or 3-4 oz for the typical wheel/tire combo:

Tire Tech Information - Tire & Wheel Package Ride Uniformity Confirmation

I don't know how much your combo weighs, but 20"" is probably heavier than the typical wheel/tire combo they refer to.

I suspect someone else can give a typical weight for your combo.

ard · #3 02-04-2010, 12:54 AM

Was that a 'road force' balance or just dynamic balance.

I'd reject a wheel that needed that much to balance.

A

eyeguy · #4 02-04-2010, 01:40 AM

Thanks for the link - TireRack recommends roughly 1/2 of one percent, or 3-4 oz was recommended tolerance for a 40 lb total tire + alloy rim. After researching a bit further it appears that the 11" width (rear) 214 + 315 mm Vred weighs about 70 lbs, yielding almost 6 oz as recommended tolerance.

Yes, it was road force tested with a Hunter - I'm not sure if it was the GSP9700 but it looked just like the machine pictured on TireRack at the above link.

So I guess it's OK? It just seemed like alot of weight, and for the cost of these rims, tires, and TPMS for my summer wheel set they better be perfect! The crew seemed quite skilled and were very careful with my wheels. Unfortunately these summer wheels won't be mounted til about May.

Do other people know how much weight was placed on their wheels to balance (and how much does the wheel weigh)?

Thanks again-

rh71 · #5 02-04-2010, 08:45 AM

From my experience in getting my rims balanced correctly over the course of a few months, which included a Hunter GSP9700 machine, it is a delicate process - especially because the road-feel on BMWs are high. Did the hunter machine spin it faster than 25mph? I had a vibration only at 70mph+. Of course even my bad rims balanced out at zero going 25mph... I didn't feel any vibration around town. No machine did it at 75mph from what I saw. After I got new tires and good rims, it still vibrated a bit. He had used clip-ons on the inside of the rim... but you may guess that it doesn't help with any outside imbalances... I brought it back and had them use the sticky strips and now it's near-perfect. The strips are too small for me to read all the weights all around so I can't tell you how much weight was put on mine.

E70x5 · #6 02-04-2010, 09:59 AM

Usually when a wheels requires that much weight u have to spin the tire on the wheel. Usually there are "heavy spots on th tire" (meaning where they joined the rubber to make it round) so what most reputable places do is take the air out of the tire and try rotate it around the wheel to counter balance the tire against the wheels. I ur example where they put the most weight they rotate it so it won't be out of balance all on that one point. Tell me if this makes sense. . .

ard · #7 02-04-2010, 01:47 PM

Quote:

Originally Posted by E70x5

Usually when a wheels requires that much weight u have to spin the tire on the wheel. Usually there are "heavy spots on th tire" (meaning where they joined the rubber to make it round) so what most reputable places do is take the air out of the tire and try rotate it around the wheel to counter balance the tire against the wheels. I ur example where they put the most weight they rotate it so it won't be out of balance all on that one point. Tell me if this makes sense. . .

Partially

When you road force, it takes the wheel imbalance and tries to match the flex-imbalance of the tire to 'mask' the wheel imbalance. You essentially need to take the tire, break lose the bead, and rotated the tire around the wheel. The machine calculates how much.

The problem- as rh notes above- is that the wheel will be imbalanced at all speeds, and the tire's "imbalance" is determined by the road force and speed. It may be perfect at the measured speed on the machine, but it much higher speeds you can get vibrations.

I just had a new set of HREs for my Pcar done. They were PERFECT. I paid to have them spun 'naked', runout measured and then tires roadforced. 315 in the rear, 265 front...One tire would not balance under the limit- returned it for a new one. No quibbles. If my wheels were not perfect, or if they needed that much weight, I would have returned them IMMEDIATELY.

A

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