(Image: Header Graphic)

Tuesday, July 29, 2014

Doug's Domain

Doug Vetter, ATP/CFI

dvatp.com has been updated!

Some URLs have changed but you will be automatically redirected to the new locations. Please update your bookmarks! Read more...

Wednesday, October 14, 2009

How NOT to Fix a Flat

As you may recall, back in June I suffered a flat tire and had it repaired. Unfortunately, during my routine tire pressure check last Sunday, I found the very same tire down to 24 PSI. I carefully surveyed the tire and found no obvious damage so I quickly concluded that the patch was leaking.

Given that I hadn't checked pressures in a few weeks I figured it was a slow leak and I could save myself the trouble of an "in the field" tire swap and wait until after I installed the winter tires in a few weeks to bring the tire to the shop for repair. I pumped the tire up a few pounds over the norm for good measure, resolved to check it regularly and get on with my life. When I arrived at work the next morning I looked back at the car and quickly noticed a conspicuous bulge in the sidewall. I let out a choice word and then took a pressure reading of 19 PSI, or a drop of almost 20 PSI overnight. I didn't have a means to pump the tire up in the field so I resolved to swap the tire with the spare over lunch.

This morning I took the flat back to the same company that "fixed" it last time. The guy I spoke to took a defensive posture and attempted to convince me that they did not, in fact, fix the tire last time. After I told him I don't make a habit of going around to tire shops and requesting free services he relented, but only long enough to suggest that it might be due to the valve stem. I acknowledged that might be a possibility but suggested he dunk the tire in the tank so we could both stop guessing. He rolled the tire away only to come back a couple minutes later and admit that the patch was leaking. I asked him to fix it properly this time by dismounting the tire, applying a patch from the inside of the tire, and then remounting & balancing the tire on the road force balancing equipment. He agreed to have it done later in the morning and I left for work.

At this point you might be thinking, how does a plug patch leak? Well, this wasn't a plug patch. More precisely this was what they call in the industry a "gummy string" which is the easiest / quickest repair technique available because it doesn't require dismounting the tire. This explains why they charged me "only" $10. Some research online suggested that gummy strings work in general but the failure rate is high enough to question their use, particularly on a high performance car where a sudden loss of pressure or blowout in a high speed turn could very easily result in loss of the vehicle.

Later in the day I went back to pick up the repaired tire and figured the worst of the day was behind me. Wrong. As I picked up the tire to put it in the trunk I realized the the tire machine retainer clamp had gouged a circular scratch through the clear and into the base coat of the wheel a few inches from the hub. I'll spare you the details of the verbal exchange that followed, but it suffices to say that I have no intentions of doing further business with this facility.

So what have I learned? Plenty.

Mileage: 183525