[TR] 205/70-15 tire pressure

[Joe Curry]

Let us analyze the front tire pressure situation for a minute.

If you are looking at the pressure only as it affects the suspension
stiffness, stiffer up front increases understeer.  So adding pressure adds
to Understeer not oversteer.  

But you can't simply use that equation because the tire profile and rubber
patch has a lot to do with it.  Obviously, you want to create the best
possible contact patch to get the best handling performance.

On low profile tires, this is highly dependent on what the manufacturer
recommends.  If you go too high in pressure, you will reduce the contact
patch and grip and in that situation your steering will go away (Understeer)

In the event that the pressure is too low, your tires will roll over on the
sidewall in hard turns also reducing the contact patch.

Joe

-----Original Message-----
From: triumphs-bounces+spitlist=cox.net at autox.team.net
[mailto:triumphs-bounces+spitlist=cox.net at autox.team.net] On Behalf Of
Dave1massey at cs.com
Sent: Sunday, June 29, 2008 9:56 AM
To: triumphs at autox.team.net
Subject: Re: [TR] 205/70-15 tire pressure

In a message dated 6/28/2008 6:03:26 PM Central Daylight Time, 
ahwahnee at cybertrails.com writes: 
> I know almost nothing about tires/pressure/handling etc -- but why
wouldn't 
> 
> higher pressure up front give you more oversteer rather than less?
> 
> Seems like higher tire pressure would give a tire more grip.  I recall
when 
> I had my old Fiat I would crank up the front tire pressure to counter it's

> pronounced understeer.
> 
> That said -- I too run about 4 lbs more in the front tires of the TR --
but 
> then I like oversteer.
> 
Perhaps my response was a bit cryptic.  I run 4 PSI high in the rear.  32 
Rear, 28 Front.  Everything you say is true.  More pressure up front does 
increase oversteer.  When it comes on unexpectedly the car tends to swap
ends.  Not a 
good thing in the twisties.

Dave   
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