What psi? - That is the question

[JBT]

i guess that you can guess that it all comes down to a manufacturer recommendation to start with, then personal preference for the fine tuning!

Mazda recommends 26psi for the NA8

[Caffeine]

ps has anyone ever put air in their tyres @ a service station (those fancy digital things that they use to stop ppl stealing their air thingy) then gone to a different station and checked the pressures? i did it for a laugh the other week - had pressures ranging from 18psi all round, to 44psi all round. scary! never trust one of them again

I hate those things Give me an old fashioned manual control one any day...

[rain902]

I have a hand held tyre pressure gauge i keep in the glove box and always use that to check.

So far my local BP has been spot on with the calibration of my gauge.

sadly bp are few and far between here since the whole "whopping great big 4cents a litre off" thingy - and i am not game to carry the longacre one that i carry to the track around with me, coz i will lose it or something.

[rain902]

i guess that you can guess that it all comes down to a manufacturer recommendation to start with, then personal preference for the fine tuning!

Mazda recommends 26psi for the NA8

ummm i should clarify - tyre manufacturer - we all know that car makers reduce pressure for NVH testing and increase it for economy testing

[Okibi]

So are they 17" or 15" ?

[Okibi]

No worries, so they're a 40 Profile?

What brand and exact type are the tyres?

[CT]

i guess that you can guess that it all comes down to a manufacturer recommendation to start with, then personal preference for the fine tuning!

Mazda recommends 26psi for the NA8

Minimum tyre pressure inflation if it's on the tyre placard - it's only a starting point. Tyre companies put a lot of research into giving you a tyre that sits square on the road under most conditions. Road tyres should be in the range of:

15s 28-32
16s 32-36
17s 34-38
18s 36-40 this is all cold and from a contact that tests tyres for Yokohama. Pressures at the lower end will increase comfort and decrease tyre performance due to the delayed response of the tyre to your inputs. Highers pressure are better in the wet as it keeps the tread open.

For tracking street tyres 4-6psi cold higher is normal to stop the tyre rolling off the rim. But yes, it kills the tread due to the heat. You increase the pressure to decrease the heat effect by reducing the amount of flex the tyre suffers. There's a point where increasing it is detrimental to tyre performance which is why we find that 40 hot in a 205/45/16 is about ideal.

R-Tyres have stiffer sidewalls and softer tread compounds and can run at lower pressures because the sidewall is doing the work, not the air. Slicks again run at much lower pressures due to the construction and the compounds they use.

[smiles]

CT that's some great info, any chance we can have it as a sticky?

Is the 4 psi range sufficient to take into account the weight of the car. I believe a heavier car would need to have higher pressures than a lighter one.

[Ted]

Personally, it comes down to weight of vehicle and tyre construction. For example, a Porsche 911 will need a bit of playing with pressures to deal with its weight distribution.

Generally, the lower profile tyres tend to have a re-inforced sidewall. But again that has to be taken with a pinch of salt as there are some really cheap 18" 35series tyres on the market these days and I would question their case construction. So it comes down to feel. Start at a point and go from there. Try to feel the difference between sidewall flex and treadblock squirm, it is very difficult to do sometimes. I would get your own gauge, then try everything from 26psi to 40psi and see what you feel is the best.

When I changed tyres recently and went to one with a more rigid sidewall, tyre pressures dropped 3psi.

[AJ]

Nexens are an up & comer in the tyre world mick, seen by tyre dealers as a way to get cheaper wheel/ tyre combos out there, from what i've heard, they have a higher road noise level than say, your michys, yokis or pirellis due to a slightly harder compound......having said that, despite what others may say, there is no such thing as a BAD tyre in the W rated low profile sports tyre world, look after them by rotating & keeping a regular check on pressures, keeping them above 30 psi & below 40 psi & you'll get a good run out of them as a daily driver/spirited run combo IMHO


BTW, i run 36 psi/ 34 psi front rear on my precedas on recommendation from one of my tyre dealers & haven't found a reason to change that yet, the tyres are wearing evenly so far (3500 k's).....just starting to knock the corners off the front 2 which is probly more due to my pisspoor driving while getting used to the car than anything else

[CT]

CT that's some great info, any chance we can have it as a sticky?

Is the 4 psi range sufficient to take into account the weight of the car. I believe a heavier car would need to have higher pressures than a lighter one.

Again, it's a reliable guide from a tyre manufacturer when testing performance tyres. Ted as always is spot on too. A good eg is my XR8 wears 18s but I run 40psi in the rear and 38 in the fronts - especially when towing. The MX5 is probably happiest at the softer end of the scales but I can change my car's high speed handling by adding 2psi front or rear so it's a fine tuning tool as well.

[MxJadeMonkey]

cold running 35 to 36 psi no higher as car becomes way to skitttish, i running 205/45 17x7 khumo supraz

[Brad]

I run 32 with the Azenis for the road, and 27 for the track, to give a hot temp of around 34-35. Sure you can pump more in them to make it feel like it's turning in better, but that's only because there is less rubber on the ground giving less friction, but at the same time less grip.

[4sfed5]

Regarding the electronic air gauges....
They are made by clipsal in australia and are very very accurate... i know because i service them...
the pressure sensor element is calibrated and is self testing.it is also VERY temperature stable having only around 1/2psi difference at 100psi between -10 degrees and 60 degrees. so when it thinks that the sensor is faulty due to having a slightly different millivolt value at atmospheric pressure it will throw an error code.
you need to make sure that the tyre chuck on the end of the hose that clips to the valve isnt leaking..
Leaking valve connectors is 99% of the "faults" we get with them......
i trust them more than any repco tyre gauge thats for sure!

[Okibi]

Good to know Glenn !

Also good to know my cheapie pressure tester is still "on the money" then.