Wheel Balancing Question

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Oct 17, 2005
Highland, NY
Wife's 2003 Taurus had a slight shake in the front end at about 65 MPH. I figured one of the wheels needed re-balancing. So to save lift time at my local garage I pulled the wheels myself and took them down. I observed the tech add air to each tire before he put them on the spin balancer. I made a mental note of that and I checked the air in each tire when I got home. I was shocked to find that each tire was boosted up to 45 PSI. So I lowered them back to spec. Earlier in the day I had done the same thing with my Civic. But I dropped the wheels off and came back an hour later to pick them up. So now I was very curious. The pressure in the Civic's front tires were now 45 PSI too! [Eek!] My question. Why did he do that? Do you need to have the tires inflated to a high PSI to get an accurate reading on the spin balancer? I'm a little peeved that he didn't tell me that the tires were over inflated. BTW...after I lowered the tires to spec it fixed the high speed shake in both vehicles. So they indeed needed a balancing.
The tire tech wants to operate the tire on the test machine close to the operating conditions on the vehicle while it is driving down the road. *Witness that some tire testing/balance machines use a road force load whiile operating} The vechcle driving down the road will see a 3-6 PSI increase over the cold tire pressures. The more PSI the tech uses, the easier it is to find belt delaminations and tread separations,... The only thing the tech did wrong was to not put the tires back in normal cold pressures when he was done.
strange...i have never added over the specified pressure before balancing or even testing the road force. however i do see the point of doing so.
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