Tyre pressures Please HELP!!!!!!!!

[G I5LES]

What is the recomended tyre pressures for 185x70x13s front and rear on a 1600 xflow

please help as i have been told differently by everyone and would like some comfermation Thanks in advance for all your help.

[Alex Wong1697456877]

The truth is that there is no real optimal pressure that applies to all 7's, even with the same engines.

 

Anything from 16psi to 28psi could work. As a rule, the fronts generally need to be the same or higher psi than the rears. 20psi all round is a good starting point but trying different pressures is part of 7 ownership.

 

I ran 26 front 18 rear on 185/60/13 Yoko 021R's and run 20 front and 16 rear on ACB10's......

 

Doesn't help at all really does it?

 

Good luck.

 

 

 

Alex Wong

alex.wong@lotus7club.co.uk

www.alexwong.net

Home : 44-(0)121-440 6972

Fax : 44-(0)121-440 4601

[Nick]

Alex has answered this pretty well. I, for example, used to run A021Rs and never went as high as 26 at the front; generally 18 ish all round, sometimes 20 front 18 rear.

 

However, Mike Bees posted some useful information recently which I've cut and pasted below.

A rather obvious but possibly overlooked point about tyre pressures: For a given situation there will be a tyre pressure that gives the optimum amount of grip from the tyre. Adding more pressure than this will reduce the grip, reducing the pressure from this will reduce grip.

 

Ergo you can't have a general rule which says "increasing the front tyre pressures will cause less/more understeer" because it depends (a) on where you're starting from and (b) on loads of other factors.

 

 

The best way to determine the tyre pressure for optimum grip (or more correctly to make optimum use of the tyre's width) is to use a pyrometer. Measure the temperature of the inside, centre and outside of the tyre. Plot them on a graph with temperature on the Y axis and position (inside, centre, outside) on the X axis. If the 3 points form a horizontal line then bingo you're heating the whole width of the tyre evenly. If they form a straight line but with the inside hotter than the outside or vice versa then the pressure is optimised but the camber and/or toe is causing a temperature gradient across the tyre. If they don't form a straight line then draw a straight line between the inside and outside temperature points - if the centre point is below this line then the middle of the tyre isn't doing enough work so more pressure required, if the centre point is above the line then the middle of the tyre is doing too much work hence less pressure is required.

 

The requirements will change from venue to venue and day to day (even hour to hour) at the same venue.

---

 

if you want to try different pressures, my advice would be to do it either at a circuit or on a bit of road you know well. I would start at something like 26 psi and go for a drive. Then try say 16 psi all round; then try about 20 psi. Ie, make big differences to start with and try to be aware of any changes, whilst driving consistently.

 

If you notice improvements, home in on those settings.

 

If you can't be bothered with all that, stick to 18 or 20 psi or so!

 

I hope that's of some use.

 

[Jason Plato]

Start at 20psi and adjust from there .

[Casbar]

I run Good Year 185 13s on a live axle cross flow. I generally go for 18lbs all round.

 

Robert

[Jonathan Ratty]

Just make sure you don't have the 40psi that the wheels leave the factory at, if you are building yourself. Car handles very poorly...

 

Regards,

 

Jonathan

[Richard Gibson]

One good way to see how much of the tire you are using is to mark them off with chalk at the quarters (00,15,30,45). The take your car out and thrash it around some good high speed and low speed corners. Since sidewall thickness is a factor, pressures can vary widely. With my BF Goodrich R1's, I ran at 20psi all around to start with and found I was not using much of the outer edges by analyzing the chalk marks. SIne then I have settled to 18psi front 16 psi rear.

 

Richard Gibson