Flat-spotting of tyres - a common issue?

[Rory]

Picking up on stevewak's thread (but not wanting to hijack it):

Is 'flat-spotting' a known, and common issue?
I drive a W203 C270 Estate on the standard 16" 55(F) and 50(R) profile Bridgestone ER30's. I often don't use the car for a couple of weeks at a time, but I've never had any of the issues mentioned in stevewak's thread.

Bridgestones are noted for havings stiff sidewalls, and the ride is poor, so I'm about to change them for Michelin Primacy's, but now I'm concerned that maybe I'll have flat-spot issues?

 

[Birdman]

Flat spotting is less likely to occur on higher profile tyres ie 50% or above. The deeper sidewall tends to distort in order to obtain the necessary contact patch to carry the weight. Low profiles tend to distort the rubber in the tread pattern to do this.

FWIW If you park on a smooth surface and paint water around your tyre contact patches, then move the car and measure the area of each dry patch in square inches, then multiply it by the relevant tyre pressure in psi, you arrive at roughly the weight of the car in pounds.:bannana:

Not very relevant except to show how out-of-round a tyre has to be to support the car!

 

[Satch]

"Permanent Flat Spots

A high harmonic flat spot ,,,,, is often not recognized as a flat spot but is often confused with a mechanical problem. This is best explained as a particular speed where the problem manifest itself. An example would be a car that has a shimmy or vibration from 66 to 70 mph but none above or below that speed range. This is almost always a high harmonic permanent flat spot.

We have seen cases where torque converters, clutch assemblies and half shafts have been replaced trying to fix the problem; it is almost always tire flat spotting. For the car owner this is very time consuming, personally frustrating, and expensive if the car is out of warranty. "

http://www.tirecradle.com/tcradle.htm

 

[TKB13]

I can understand this if a vehicle has been lying in a barn for several years with the tyres on the rims, but I've been driving now nigh on fifty years, using crossply's, radials, retreads, remoulds etc. and have never, ever come across this issue occurring when one has stood just for a week or three! Have I just been lucky? (Barring of course flat-spots caused by very serious skidding by second-rate drivers).

 

[Birdman]

I can understand this if a vehicle has been lying in a barn for several years with the tyres on the rims, but I've been driving now nigh on fifty years, using crossply's, radials, retreads, remoulds etc. and have never, ever come across this issue occurring when one has stood just for a week or three! Have I just been lucky?

It's more likely that you don't use the type of tyres that tend to flat spot.
The problem is most likely to occur with ultra low profile tyres on very wide and relatively sticky rubber of the type used by high performance cars, where predictable handling at the limit and under all road conditions are a priority.

If you go to the weblink in Satch's post you'll find a fuller explanation of the causes.

 

[glojo]

The problem is most likely to occur with ultra low profile tyres on very wide and relatively sticky rubber of the type used by high performance cars, where predictable handling at the limit and under all road conditions are a priority.

Definitely agree,
My stretched limo stands idle for months at a time, and we have never had a problem.

The link Satch supplied is very informative, but I felt it was mainly an advertising story for the very expensive supports.

John

 

[GrahamC230K]

Car stood at airport car park (outside) for a week in freezing temperatures. Drive like it was on 50p pieces for the first few minutes!

 

[Birdman]

Performance tyres are best when warm so I suppose it's no surprise they don't adapt to winter use. That's what winter tyres are for. Everyone in northern Europe knows that!

I've just ordered a pair of Gooodyear F1 Eagles 265/35 ZR18 GSD3 for £250 delivered, from Johnson Tyres. I wonder when they will find their way here?

 

[TKB13]

It's more likely that you don't use the type of tyres that tend to flat spot.
The problem is most likely to occur with ultra low profile tyres on very wide and relatively sticky rubber of the type used by high performance cars, where predictable handling at the limit and under all road conditions are a priority.

Yes, I take your point there, I'm obviously a bit on the 'old-fashioned' side!

 

[Birdman]

Yes, I take your point there, I'm obviously a bit on the 'old-fashioned' side!

Best place to be. I've spent hundreds repairing kerbed alloys. It's an occupational hazard with low profile tyres because the wheel rim is below kerb level. Plus, these tyres don't come cheap - the manufacturers know a high-margin selling opportunity when they see one!