Tyre Pressures

[CriggyBarBar]

Hi all

My Westfield SEi Widebody is back on the road following a 6 year hiatus due to the usual excuse of having kids. So I guess that makes me a Newbie!

As the car has been sat idle for such a long time, I had a chap check the tyres were ok for flatspots which involved him putting them up to maximum pressure. He then let them down to about 24psi all round. The tyres are fine, but I can't remember what sort of pressure they should be at. 24 sounds high to me for such a light car.

So, I'm running 205/60R13's (from a Capri) on a 1993 pre litigation SEiW, what would you guys say is a sensible tyre pressure??

Many thanks

Chris

[Captain Colonial]

18-20 psi is right for normal road use. 24 psi is correct for dramatic understeer at speed or snap throttle oversteer.

Welcome back!

(Oh, and SEiW is not pre-lit, by the way.)

[peterg]

and those tyres might no have flatspots but it's likely the rubber has gone off to some extent and they'll be harder and have a lot less grip than when new especially if they'd been on there for a while before the 6 year lay up...

[Captain Colonial]

Yeah, excellent point, good catch Peter. Suitable for destroying on an airfield track or drift day, but otherwise probably best to change them after six years old or more. The rubber goes off, gets hard and brittle. Easiest way is to check the small manufacturing date code on the sidewalls, which will be four digits long like "3706", which means made in the 37th week of 2006. If it's three digits long, it's pre-2000 and should definitely be binned.

[AdamR]

To add to the above - I recently changed some ~2-3 year old rear A048Rs and ~5 year old front A048Rs for new ones (exactly the same model/spec) and it has completely transformed the car.

[kevip6]

Back to the tyre pressures briefly

I was under the impression from this forum I should be running in the 18 PSI region on my 13" 205 R888's and when I took the car to Graham Hathaway racing for a full geo he put them to 24PSI saying that was a much better pressure to run at and the 16-18PSI i had them at could have been a problem when cornering hard?

He does a lot of Westfield track and race prep and so I'm now very confused when you say

"24 psi is correct for dramatic understeer at speed or snap throttle oversteer."

Thanks

[Captain Colonial]

Well, let me put it this way. I've tried it at 18-20 psi, and I've tried it at 24-25 psi, and I know which one for me is more predictable when doing fast road work. Effectively, bumping it up to 24-25 psi for me reduced steering effort slightly, but also reduced tyre contact area, so when it did "break away" on oversteer, there was little or no warning and you had to be fast to catch it. Similarly, when I wanted to turn in sharply, there was audible tyre scrub and reduced turn-in bite. And that's on dry, clean roads. Still, some like to drive that way, lots of slide and turn primarily with throttle. Each to their own, try it yourself, etc etc etc...

[stephenh]

There is a theory that with the tyre pressures a bit higher, say around the 24 psi mark, that on track the tyre tread will heat up more (good) rather than the tyre carcass. However I don't know anyone who has tried it with success. Asa far as I am concerned, I only compete in sprints and hillclimbs, when the tyre hardly has time to warm up properly anyway, so we might as well run with lower pressures, and at least have maximum footprint, and hopefully some warmth in the tyre.

Of course, for road use, getting the tyre warm is not the point of the exercise anyway, so cannot understand the advice you were given by Graham Hathaway. So do what everybody on this thread has recommended. It works for the "Massif", so should work for you. If it doesn't, try experimenting, but I'd bet good money you'll end up somewhere in the 18-20 psi mark. ;)

[kevip6]

Interesting. I wasn't questioning the advise, just after clarification as I was surprised when Graham increased the tyre pressures in the first place. I had asked he to set it up primarily for track performance if that makes any difference?

I'm doing an airfield "activity day" in a few weeks so maybe that would be a good time to play with the pressures.

Is there a minimum safe pressure to run before you're at risk of the tyres falling off during hard cornering?

Not meaning to hijack this thread, hopefully this is useful for the OP as well

[stephenh]

I've run mine in sprints and hillclimbs with the pressure as low as 14.5 psi cold, and the tyres didn't fall off!!

Mind you, I established that was too low, at 16 psi cold they were much better.

What make and model of tyre are you using?

If a medium or medium/hard compound trackday tyre, personally I'd start with 18 psi cold, for a trackday, and check the temps after a session on track. If the temps have risen above 20 psi hot, then try letting a bit out to bring the pressures down to 20 psi hot, and see what it feels like. Then by all means try experimenting increasing the pressure by a couple of pounds, and see what difference it makes.

[AdamR]

Back to the tyre pressures briefly

Sorry

My 2p:

On the road, I run around 17 cold (185/60/13 up front and 205 on the rear). Bit more comfy, and you can't push the car anywhere near as hard (or get the tyres as warm) as on track anyway.

For track, I got hold of a temp probe and had a play at Anglesey on Saturday, ended up with 23 hot front and 22 hot rear to give a perfect (within 1-2 degrees) temperature distribution across the carcass. However, earlier in the morning when I was running around 20 hot, my lap times seemed to be better. All of this is with a passenger, by the way.

[Mark (smokey mow)]

Kevin,

Graham Hathaway certainly knows his onions, and indeed he has set my car up very well, but as a caveat and with the exception of his early autocross and rallycross days, the majority of his racing experience has been slicks.

From my own experience of playing with pressures on road and sprints (on 14" wheels) I find 17-18psi works best for my car, although I have on occasions droped that to 16psi cold for sprinting, but my A021's do have a very stiff tyre wall which may help.

[frag68]

My 2p worth is I am running about 18psi on the front, but I got 2 budget Uniroyal directional tyres fitted to the rear and asked the garage to inflate to 18psi and the car was uncontrollable and bouncing everywhere. The sidewalls are much softer than on the front tyres so I am running them at 25psi and the car is back to what it was like before the new tyres were fitted.

Tyre size is 195/60/14.

[Dave Eastwood (Gadgetman) - Club Chairman]

STOP

Please, goodness me, though thread drift is normally a fantastic part of the Boardroom and has given some of uour most surreal and funny moments over the years, a technical thread on tyre pressures IS NOT THE PLACE FOR IT.

With the greatest respect, at it's extreme, advice that is perfectly sound for ONE poster on this thread, could have another backwards off the road with a destroyed car and a hospital visit on the cards!

You cannot assume what works well for one particular car set up with a particular tyre combination can be transferred to another!

Toyo R888's are a semi slick trackday tyre with specialist compounds and a particularly stiff side wall. They benefit particulalry from quite aggressive geo settings - they love camber for instance and will lap up 2 or more degrees of negative camber. They will also respond really well to certain tyre pressures, though its probably a good idea to distinguish between road and track use.

Kev told his specialist that he essentially wanted a track set up; his whole geo as well as the pressures he's been recommended may reflect Graham's track experiance of Westfield's - try it and see Though as others have said, they may be a shade high for the road, but without knowing the rest of the set up, thats just idle speculation.

But NON of this, with the exception of Pete's post is ANY USE to the original poster! (And we're at risk of confusing him).

We don't know what the tyres are, other than round and black , the only thing we do know is they're minimum six years old and could be much older, they've probably been exposed to heaven knows how many freezing temperatures and that they're probably as hard as diamond and as sticky as a diesel on a wet roundabout.

Get a new set of tyres on, even if you only put a nice budget set of Toyo T1S/T1R Yokahama's etc

Er, and breath.

Oooh a two rant day, must check my medication.

[CriggyBarBar]

^{Thanks to everyone, I will pop and have a look at how old they are. However, the best advice seems to be to stick some new ones on. I went for a spin last night having dropped the pressures down to 18psi and it did indeed feel better. Looking at the weather forecast though that would seem to be the last time I will be going out in her for quite a good few days! Cheers for now.}