[Vwdiesel] Tire pressure

James Hansen jhsg at sasktel.net
Fri Apr 14 17:52:20 EDT 2006

David Cook wrote:

> Tire technology has changed quite a bit since then
> (different types of tires, rubber compounds,
> durability, designs, maximum pressure range, etc), so
> tires you buy today are probably nothing like the
> tires that VW put on the car originally, which is what
> the specs in the doorpost come from. 

Not really, Let me clarify something.
The tire pressure dictates the spring rate of the tire, and what the 
suspension was designed to work with.
The tire is a big spring, and putting more or less air in it varies the 
spring rate.  It works in conjunction with the suspension springs that 
were selected by the manufacturer, but changing tire pressures mostly 
changes spring rate on that wheel, since radial tires are designed to 
not change shape under pressure changes within a reasonable level.

99% of what you change with air pressure is ride comfort, and how well 
the suspension sucks up the little bumps- because the tire is a 
suspension component.

Advertising mavens would have you believe there are differences, but 
other than radial tire technology that was introduced long ago, there 
have been no significant changes other than rubber compounds and quieter 
tread designs, which DO NOT affect suspension performance.  For the most 
part, sidewalls haven't changed much other than as fashion statements. 
Sidewall height affects the spring rate significantly if you use tire 
with minimal sidewalls (20" rubber bands)but on our cars, pretty much 
aren't used, but from a suspension point of view are monumentally stupid.

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