Tyre pressures

[Mattv6]

Hi,

What are the correct tyre pressures for the Dymag wheels (15 front and 16 back) for road use?

Thanks. 

[TrackDayBore]

Depends on what tyres are fitted to the Dymags...?

[hamtt]

[quote="TrackDayBore"]

Depends on what tyres are fitted to the Dymags...?
[/quote]

Rubber ones I think

[Mattv6]

Toyo r888s

[Northnoble]

I reckon 18 rear and 16 front is about right for most conditions!

[FlyingTrotter]

The cars are quite sensitive to changes in tyre pressure - I would start with 16/19 and adjust from there - I run Yokos on the road and track and tend to find 16/19 ok on road most of the time but on track it's surprising how much small adjustments affect the feel

[speedmachine]

I run 16/19 with the same setup, but (not hyjacking the thread, just taking it to a higher level) if one drives a cold track and has difficulties getting the tires up to temp, should one lower the front pressure or putting it up a bit? I believe I got advised in the past to put the fronts up to 18psi  in order to get the temps up a bit a little faster.

this sounds unlogical because I would think that the friction gets lower due to the harder tire, so the temps should be going down.

Apart from that, are you guys riding those pressure hot or cold? On track I release the pressures once the tires are hot back to 16/19 as they tend to go up a couple of tenths.

[TrackDayBore]

Hi Mattv6,

As Ian said "small adjustments affect the feel" ...which is true, and the "feel" is individual to the driver - that said, how does a 'newcomer' to an Atom know "how the car should feel" ...?

As I've said before... what matters is the hot tyre pressures, or to put it another way, what is the 'required' tyre pressures (on a given day and road/track surface) to achieve the best possible 'working temperatures' of the tyre/tread surface to get the maximum grip...?

To expand on this, all AA drivers of course want the maximum tyre grip whether on the road or the track..  but of course in cool air/road temperatures (and without driving like you're on a racetrack) it will be very difficult to get the tyres up to their 'optimum' working temperatures on the public highway.

So this is where a compromise must be arrived at...  but (and have a quick yawn) if only it was that simple  .  Because as we know tyres provide a large part of the 'springing' in a car suspension system and yes you guessed (within limits) the lower the pressure the 'softer' the ride...!  And proportionally a softer tyre will provide 'softer springing' when combined with stiffer springs - that's why I often drive home from a track with around 8psi in my front AO48's...! So as to keep as much tread/tyre surface in contact with the road surface...  because my track setup springs are a little 'stiff' and unresponsive to normal road surfaces... so the softer tyre pressures soak-up the 'bumps'. You can then correlate the inverse...  higher tyre pressure transfer the bumps the the 'softer' springs and they in turn soak-up the bumps, and of course the dampers soak-up the "energy" absorbed/stored in the spring.

Anyhow, stay with me, there's nothing on the telly...  does all this 'science' really matter...?  Well yes, if you want to get the best 'possible' grip out of your tyres on any given day, on any given road/track surface with any given driving 'attitude' 



So this has got me thinking and here's the challenge (to somebody)....  with all the years of 'collective experience' on this forum it must be possible for someone (good with charts/tables) to collate the available data from forum members and "once and for all" create a SUGGESTED Tyre Pressure Chart...!

With basic variables...  make/model of AA - make/size tyre - winter/spring/summer - surface road or track - suspension setup (road or track)....  then all the 'newcomer' has to do is just read along the chart and "voila" some "Guidance Pressures"

It's only a suggestion.

BTW, I run 888's on the rear at "around" 18 to 20 psi and AO48's on the front at "around" 9 to 12 psi... Hot, or do I mean Cold 

[Steve]

Balance is a big part of what you are trying to achieve, and 16/19 should achieve that, but I'd always measure the pressure hot, rather than cold. Normal driving, and the PSI might add 1 or even 2 degrees depending on ambient temperature.

As for track driving, and having measured pressures with remote sensors, the thing only thing that really heats the front tyres is heavy braking - quick cornering achieves surprisingly little. I guess you could heat the rears with the throttle, but again from my experience it's the braking that produces the real heat. Surface of the tyre I'm sure will get temporarily hot with cornering and throttle etc, but it's the heat radiating from the disc into the wheel that will produce more lasting temp and pressure gains.