[Healeys] TYRE SIZE for RIM

sebring at illawarra.hotkey.net.au sebring at illawarra.hotkey.net.au
Tue Jul 3 21:06:31 MDT 2007


I am a little perplexed at yhe variety and range of poinions and sizes that are 
being listed for Healey rims.

The metric system is very easy to understand.
ie. 185 in the 185x70x15 size designation is the nominal cross section width of 
the tyre as designated in the industry standards.

Now 185mm is 7.2 inches, or between friends, 7 inch rim width.
The recommended rim width for 185 will most likley range from approx. 6.5 to 7 
and a bit.

185 on 4.5inch rim would be way outside the acceptable range, Far too much bag 
in the side wall and the tread may not sit flat and therefore wear uneven, 
brake less than designed and handling likely to be sloppy due to side wall 
flex. The tyre will not carry its designed lateral load.
Alternatively 4.5 inch would equate to a tire size of 115 !!!
The smallest I am aware of is 145 0r 155 as used on Beetles of old -- now thats 
a handling benchmark

Check any race car where handling and braking is optimised and the width apart 
of the tyre bead should be very close to the tread width which should match ( 
within reason ) the rim width.

Looking good is only one small part of the safety and performance equation.
The best power, the best brakes, the best suspension are only as good as that 
little contact patch so please optimise it. Pressure is also part of the 
equation to control this contact patch. The wear pattern is only an indicator 
of how much of the tread face/contact patch is in touch with the road surface 
and this controls braking and roadholding.

Joe


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