What pressure?

[Andy Pandie]

I'm sure this has been covered before, but a quick search didn't reveal the answer.

My Tuscan 2S has 255/35/18 Toyo T1R's all round, with recently fitted Nitrons and Eibach srpings (not sure of their settings). Before the suspension change I had the tyre pressures as per the handbook, 28psi all round (31psi fully laden) which felt about right. Now that feels a bit hard and less stable, very easy to lock the rears, so have dropped to 26psi all round, it was at 24psi when I picked her up which felt ok. I'm happy to play around until it feels right, did so with my Chim, just wondered what everyone else sets theirs too.

Just for reference GV's orange bible states 24psi all round, and, mytuscan.co.uk states 22-24psi front, 24-26psi rear.

Thanks in advance.

[Cats]

Hi Andy
Mine was at 28psi alround on Goodyear F1s but has felt a little harsh especially in the cold weather. I dropped it to 25 front and 26 rear before the Cheddar run and certainly felt better. But I think I will still try some different pressures especially as it warms up I might go a little lower. Would be interested to see how you get on.
Regards
Neil..

[Andy Pandie]

Thanks Neil,

Guess I just need to play around with the pressures.

Thought it might be benificial to get them correct before playing with the damper settings, or embarking on a long loaded up trip. Dropped to 25psi tonight and tbh didn't notice any difference, albiet only over twelve miles, maybe try down another pound next weekend

[Speed eight]

Tyre pressure.........hmmmm,ok.
So I think that we know that any given reading in a handbook or from chum to chum is probably going to be wrong.
But it is a starting point.
So how can we ascertain the correct pressure for "our" car?

For this we need a chum, an infra red temperature reading gun, (these are now not too costly and can be got from quite a few places.) starting pressure idea, and an idea of how we are going to drive the car.
The tyre pressure will only be "right" for one type of driving and a compromise for all others.

So for my Tuscan I do this.
Let us try 22psi. But it could be 24 or 26psi.
Drive the car in a "spirited" manner, as this is how most of my driving will be, I hope.
Not crazy but quite fast.
After say 5 miles of this style of driving on a nice sunny day, having planed your route so that at the 5 mile point you can safely pull up off the road, do just that.
Now your chum, who is already there, quickly takes the temperature reading of each tyre across its contact patch, side-middle-side.
When the pressure is "right" the tyre will be the same temperature across the tyre width, within a couple of degrees.
Now this will work for any tyre and any width.

Persistence is the key operation here and the results will be felt.

Regards.
Speed eight.

[Basil Brush]

Failing that, I'd go with 24 front/25 rear.

[GT TVR]

28 psi is too high; use 24

also, don't set the Nitrons too hard. I have the same set up (and same car) running 11 front and 9 rear from soft (track day 15/12); this way it really absorbs the bumps in stead of being thrown of track

[Andy Pandie]

Thanks for the replies, confirms my theory that 28psi is too hard, I'll revert back to 24psi as they were when I picked her up.

Speed eight, I'm sure your method is correct and if trial and error fails I'll give it a go, just need to find me an IR thermometer, oh and a friend P.S. Nice conversion you have there