What psi? - That is the question

Mick_98MXV · Postby **Mick_98MXV** » Tue Jan 17, 2006 3:09 pm

Thought i should bring this here instead of hijacking another topic.

Quick Fit told me to put 40psi in the front and 38psi in the back of my
205x40x17 tyres.

'LM' agrees as he does 40psi all round and 'Miata' disagrees with back-up from Bridgestone website...

What psi do each of have in ur tyres? And why's that??

Bevan · Postby **Bevan** » Tue Jan 17, 2006 3:11 pm

I ride on 34 cold. Any higher is too harsh.

On a track day, I put it up to 38 cold which equates to around 44 hot on the track.

Postby **Okibi** » Tue Jan 17, 2006 3:30 pm

I use to run my 17"s about 40-42, i guess because the profile was pretty low i was paranoid about the sidewall flexing too much and hitting the rim.

I ended up chewing up the insides of my tyres in the process.

Take a look along the inside edge might be a good sign your running too much pressure.

Another solution is the mark your tyres with some chalk, lower the HOT psi temp by say 2psi each time until you find a happy medium.

Matty · Postby **Matty** » Tue Jan 17, 2006 5:13 pm

~30psi max. any more and the ride is too harsh.

JBT · Postby **JBT** » Tue Jan 17, 2006 5:27 pm

30-33psi cold. Tyres are 195/50 15. The car feels skittish on normal road surfaces with them any higher.

Postby **Okibi** » Tue Jan 17, 2006 5:37 pm

What tyres are they?

I run my 15" Toyo T1-Rs at about 34-36PSI (cold) but that's no use to you because you're running a different profile and tyre. :roll:

JBT · Postby **JBT** » Tue Jan 17, 2006 5:57 pm

Bridgestone Turanza

Postby **Okibi** » Tue Jan 17, 2006 6:18 pm

Having a quick look at their website..

the ER-33 goes as low as 45
the ER-30 goes as low as 45

What type of Turanzas are they?

Craig · Postby **Craig** » Tue Jan 17, 2006 6:22 pm

ER30's in 195/50/15

Postby **Okibi** » Tue Jan 17, 2006 6:27 pm

Mick_98MXV wrote:...Quick Fit told me to put 40psi in the front and 38psi in the back of my 205x40x17 tyres.

Ok i'm confussed.

smiles · Postby **smiles** » Tue Jan 17, 2006 7:33 pm

I run 32 psi all round on 205/45/16.

I think 40 is too high and the car will feel skittish, for such a light car. Start with something lower and just monitor the wear and make small changes.
After going for a hard drive on the weekend, the wear is even so I'm sticking with 32. The tyres felt great around bends too.

npn4875 · Postby **npn4875** » Tue Jan 17, 2006 8:13 pm

Like Boags said, I run 40 cold for the road and 45 for the track. The SP is standard NB suspension, no mods, and irons it out pretty well. It may be a bit skittish if (when) I put Teins all round and set 'em hard as a rock ;)

Caffeine · Postby **Caffeine** » Tue Jan 17, 2006 8:31 pm

34 cold here too.... 204/45-16 yokohama CDrives.

I ran the same with the stock Turanza ER30 and yokohama A539's, both in the same size

Garry · Postby **Garry** » Tue Jan 17, 2006 9:33 pm

205 45 16's 32 cold all round for general cruising and 33 for going fast

rain902 · Postby **rain902** » Tue Jan 17, 2006 9:47 pm

i am nowhere near an expert at this sorta thing - but heres my humble contribution anyways...

i run 40pseez in my work car coz it has really ordinary tires, and i want the extra crispness (and economy) but i start @ 26-28 pseez on the track rubber...

bear in mind that for everything there is a cause and effect - running any tires with higher pressure will make them stiffer, but reduce the contact patch on the road, thereby lessening grip.

silly me forgot to adjust pressures @ winton during the rain a few months ago, as the day wore on a dry line appeared, my hot pressures were up around 40psi (optimum for those tyres is low-mid 30s) and i had a really well defined wear mark in the centre third of the tyre. :shock:

I didnt record any faster time on the dry run with the wrong pressure than i did on the wet runs with the right pressure. :oops:

Running asymmetrical pressures (eg 30 front/34 rear) is a good way to subtly change the handling characteristics of your car. i think that most sedans and stuff call for higher pressures in the rear to compensate for the additional weight of rear passengers and luggage etc - things that dont really factor into a -5 drive

fwiw i generally have 2 pseez lower on my drive tyres to give the better compliance/adhesion.

We are all running different pressures - 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! trial and error, my friend. trial and error.

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 :shock: