Roger Kraus Racing, a supplier of race tires, has a pretty good
description on the role of the various parts of the cars suspension
(including tires) and what changes produce what results. See at
http://rogerkraustires.com/TechSheets/overunder.shtm
N.F.I. and all of that.
MIke Denman
On Jun 29, 2008, at 10:09 AM, Joe Curry wrote:
> 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@autox.team.net
> [mailto:triumphs-bounces+spitlist=cox.net@autox.team.net] On Behalf Of
> Dave1massey@cs.com
> Sent: Sunday, June 29, 2008 9:56 AM
> To: triumphs@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@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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