In a message dated 9/9/99 9:45:45 AM Eastern Daylight Time,
gomog@angelfire.com writes:
<< I was using Pirellis until I was steered to Michelins (Energy MXV4) by
the Porsche Club guys at the track here. >>
A couple of points on the tire subject.....
The flat spotting issue which started this thread is going to happen to
almost any tire using a nylon cap. Tires with H & above speed ratings
virtually always use a nylon cap. The nylon softens a bit when the tire gets
hot. When the car is parked, the nylon cools taking a flat spot shape where
the tire is in contact with the pavement. This causes the vibration when you
start to drive again. Once the tire warms up again the flat spot & vibration
go away. How long it takes for the flat spot to go away and the sensitivity
to flat spotting varies from one tire brand/type to another.
Another cause of vibration is tire uniformity. There are a bunch of radial &
lateral uniformity characteristics that vary in tires. And it is complicated
by multiple harmonics, etc. Even with perfectly balanced tires, it is
possible to have vibration problems if a car is sensitive to a particular
uniformity characteristic. For replacement market tires, uniformity levels
can vary widely between different tire brands. My impression of our favorite
car is that Mogs are a bit more sensitive to tire inputs than most cars of
similar vintage. Perhaps the reason a number of people have mention good
luck with Michelins is due in part to uniformity levels. Michelin tends to
put a major emphasis on production quality and uniformity.
As for personal experience, replacing almost new Goodyear G somethings with
Michelin XZX made a nice improvement on my Plus 4.
Cheers,
Ken Payne, oddcarnut & tire nerd
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