TYRE PRESSURES

[Monitorlizard]

dhutch,

           when I got mine,a couple of weeks back,tyre pressures were 25 all round,which was too much,in my opinion.When I visited the Westfield factory,they said 20 to 22 should be about right.I`m running 20 all round,which is certainly more comfortable on the road.Might drop thr rears to 18,& see how that goes.Thanks for your info,both cars will be much the same weight, etc.

 

                                                                               Brian

[dhutch]

When I visited the Westfield factory,they said 20 to 22 should be about right.I`m running 20 all round.

Interesting. Obviously it will slightly depend on the car, weight/tyres/etc and it may be I am running a little soft.

 - Certainly if I try autosoloing with the fronts down at 14-16ish the grip is decreasing, and or feeling increasingly wallowy.

 - I am no expert, and have not done at much experimenting or back-to-back testing as I would like to have done yet.

 

For reference, my car is around 540kg and running 185/60R13 A539 Yoko's all round.

 

 

Daniel

[Captain Colonial]

For the sceptics out there yes, a few psi makes a big difference.  I run 13" Yoko 048s and at 20 psi they felt awful, lots of feedback vagueness, ploughing understeer and bounce.  Dropped them all to 18 psi and the difference was staggeringly better, positive feel, crisp turn-in, less bouncy.  Definitely worth experimenting with (in a safe place, of course).

[stephenh]

It also depends to some extent on the make and model of tyre, also to some extent I suspect on tyre size.

Stiffer side walled tyres are fine on lower pressures, if you dont mind the tyre acting as one of the suspension mediums.

Typical of stiff side walls would be Toyo 888s and R1Rs. Whereas T1Rs are I think (I haven't used them myself) softer tyre walls so need a bit more air to keep them stable.

I used to run my Kumho V70As at 16 psi for sprints or even a bit lower for short tracks in cold ground conditions whereas I run my Avon ZZRs at 18 psi (after advice and experimentation). The Avon has softer tyre walls than the Khumo.

For road use, using a slightly more road orientated tyre, I'd be surprised if you found any advantage in dropping the pressures below about 19 psi.  

[John K]

I have just settled on 17 psi in my 205 R 13 Falkens

 

The ride was still too jiggly but I didn't want to run the tyres any softer so I backed off the rear shocks all the way (in a few steps) and the fronts by 3 clicks.

 

The ride is now almost enjoyable and in terms of real world public road speeds I believe the car is actually quicker as the tyres spend more time touching the road.

 

Not sure what the shocks are. They are yellow with an adjustment screw at the base with a click every 90 degrees - one day I will read the labels

[alexander72]

Sound like spax john,

[John K]

Thanks, and I do know how pathetic that must have sounded to all you enthusiasts.

 

"What sort of shocks do you have?"

 

"Yellow ones"

 

"Have you considered buying a hatch back?"

[Liwijatan]

I got my self last week Toyo R1R 15" 195/50

Running 18psi and the rear feels a bit slow. The tire seems to have very good grip and turns in very agile but the rear feels kinda slow.

In a fast left right combination it feels solid when I go into the first part. But in the middle, when I have to turn to the other side, the rear feels very blurry. I'm not sure if this is kinda normal as I only know normal cars with high tire pressure and 18"+. Is that normal and I simply need to get used to it? Only encounter this with higher speeds 90mph+

On lower speeds the tire feels awesome. :-)

[Greg 1]

Have tried various pressures in competition from 14psi up.

Finally settled on 22psi cold all round.

 Posting quickest times at that pressure. Car is a live axle and I run quite soft suspension settings. No ARB's.

Interesting to note that the Yokohama motorsport web page actually states that none of their motorsport tyres should be run at less than 19psi. Tyres have an optimum pressure range and if you run outside of that then you will not be getting the best performance from the tyres. This was explained to me in detail by one of Dunlops top motorsport guys here who is responsible for the supply of tyres for the V8 Supercar series over here. This is regardless of the cars weight. A light car will be toward the bottom of that range but still within it. In the case of Yokohama you will need to be running at least 19psi to be inside their optimum range. Westfield in my opinion are on the money with the pressures they are recommending 

[Mighty Mart]

Hi Greg,

i would imagine that most cars wearing yokohamas would be significantly heavier than a 7 type car though, so going lower than 19psi for our cars would not be the same as in a tin top?

Mart.

[Greg 1]

Yokohama don't say a light car can run at lower pressures, it is 19psi minimum period.

You are welcome to read their motorsport tyre pages for yourself.

The Dunlop guy described this to me. The tyres are designed to run at their optimum between pressure x and pressure y.

There are then a variety of factors that then impact on the exact pressure in that range for a given vehicle on a given circuit etc etc.  But the best pressures selected will still be in the tyre optimum pressure range to maximize tyre performance. Different brand tyres or model within a brand could well have a different optimum pressure range.

My discussion with Dunlops expert was not the first time that I had heard this. I also had a lot of discussions with a professional race driver and now team manager who has also raced 7's for fun since the late 60's. He had the same story and told me I was running my pressures too low. I then experimented with higher pressures and settled on 22 cold which for me was the sweet spot recording my quickest times.

I would suggest that the next track day you go to, take some data logging equipment to record times and have a play with higher pressures and see how you go. A change of 1 to 2psi can have a marked difference in performance. Record all your times and tyre pressures. It is only by doing this type of methodical testing will you trùly find out what works for you. What works for me may not be your optimum.

[Dave Eastwood (Gadgetman) - Club Chairman]

27 minutes ago, Greg 1 said:

I would suggest that the next track day you go to, take some data logging equipment to record times and have a play with higher pressures and see how you go. A change of 1 to 2psi can have a marked difference in performance. Record all your times and tyre pressures. It is only by doing this type of methodical testing will you trùly find out what works for you. What works for me may not be your optimum.

While this is very true, unfortunately, if caught, you'll typically get booted off the average UK track day, as timing is expressly forbidden.

[Greg 1]

13 hours ago, Dave Eastwood (Gadgetman) - Club Secretary said:

While this is very true, unfortunately, if caught, you'll typically get booted off the average UK track day, as timing is expressly forbidden.

Over here we have track days often referred to as tuning days for this exact purpose. You will see everyone out taking pressures, tyre temps and adjusting suspension and geometry to get the best out of their cars. Great day out as most of us weekend warriors who are doing it for the fun, exchange data and ideas and help one another out. You learn an awful lot from days like this particularly from the blokes who have been doing it all their lives.

[Mighty Mart]

On 4 July 2018 at 16:18, Greg 1 said:

Yokohama don't say a light car can run at lower pressures, it is 19psi minimum period.

You are welcome to read their motorsport tyre pages for yourself.

The Dunlop guy described this to me. The tyres are designed to run at their optimum between pressure x and pressure y.

There are then a variety of factors that then impact on the exact pressure in that range for a given vehicle on a given circuit etc etc.  But the best pressures selected will still be in the tyre optimum pressure range to maximize tyre performance. Different brand tyres or model within a brand could well have a different optimum pressure range.

My discussion with Dunlops expert was not the first time that I had heard this. I also had a lot of discussions with a professional race driver and now team manager who has also raced 7's for fun since the late 60's. He had the same story and told me I was running my pressures too low. I then experimented with higher pressures and settled on 22 cold which for me was the sweet spot recording my quickest times.

I would suggest that the next track day you go to, take some data logging equipment to record times and have a play with higher pressures and see how you go. A change of 1 to 2psi can have a marked difference in performance. Record all your times and tyre pressures. It is only by doing this type of methodical testing will you trùly find out what works for you. What works for me may not be your optimum.

Hi Greg,

Thanks for the informative reply....very interesting.

Exactly what a forum is for - a mine of information and always happy to learn from others experiences :-)

Mart.

 

[DamperMan]

A few weeks back I was about to go visit a customer about 75 miles away and last minute thought “it’s sunny.. let’s take the westfield”.   I’d been driving about since a wet Curborough with very low pressures. I whacked some air in using the dodgy air gauge at work ( I keep the good one locked away).  I have to say the car felt really sharp and the steering a whole load lighter.  Ride was harsher but still pretty good......   It turned out  when I checked the pressure the next day my 20 psi reading was really 32.    It would have probably been lethal in the wet but on a really hot day I quite liked it.  It felt very predicatable and driftable!      As some one else said the only actual measure of performance is actual times.    Feel can be very deceiving alone.      I read some ware back 20 years ago when I started in the world of suspension, it’s better to be 2psi over pressure than 2 psi under pressure.   

car weights, tyre makes, sizes, wheel alignment and personal preference all have an effect on that is optimum for a given car.