Tyre Pressures
 

Had a good reminder this morning about how important it is to keep your tyre pressures up to the mark, especially when running stiffer than stock suspension.

Had been a bit slack and hadn't checked them for a while. The car had been feeling a bit lacking in grip and a bit sloppy when braking late for tighter turns. It also felt like the ride was a little out of whack.

Well, checked them this morning and they had slipped down to 31-32psi (cold). Bumped them back up to 36psi where they normally are in suburban driving and what a difference!

Car felt tight and agile again. Had a fun little blast into work. Much sharper turn in and even better ride - I think because the tyre pressures were a better match for the spring rate.

So, don't get slack like I did :nono: ;) . Keep those pressures where they should be and you'll enjoy the car much more. :)

Thanks for the reminder. 35 all round still.

i do 36

I do 38 ...

... is that too high?

I do more then all of you

my murcotts instructor told us to keep it at 38psi

and that's what i keep it at :)

I run 38 in both the 8 and the 7.

Have to point out that is a CX-7 not RX-7 http://i97.photobucket.com/albums/l2...smilies/ed.gif

I ran 38 for a while but Sydney's suburban track system is just too pockmarked to live with. I find 36 is the best compromise. If I know I'll be on the freeway for a while on a trip or something, I go up to 38.

Of course you do! But you have 20s don't you?

I do 38 in front and 36 on rears.

My tyre guy told me 38 will keep the tyre from distorting around corners when I push the car while 36 on the back is fine as they are just there for the ride.

In fact at a tad of 29,000 kms my tyres are wearing well and wearing my nerves with their constant whirring...but that's ok cause I have found Joss Stone and her music drowns out the noise!!!

I have always believed that the correct tyre pressure was the one which gave you even tread wear across the profile. I'm running 245's, and 260kPa (~38psi) seems about right. I would imagine that possibly 250 kPa (~36psi) would be OK for 235's and 235kPa(~34psi) would be good for 225's.

I do mine every Sunday morning before I drive out of the garage (nothing to do with religion, just a day of the week to do this routine stuff). Temperature has an influence on tyre pressure. As the weather gets cooler, tyre pressures will drop, so it is important to check frequently during the autumn months.

i check almost everytime i fill up (every 2 to 3 weeks)... it reads 37psi/38psi before i pump it up to 40psi. Tried to go to the same servo much as i can.
has anyone tried nitrogen inflation? it supposed to keep the constant tyre pressure and better fuel economy for long distance trips. the normal air we pump from servos contains water (cant remember the percentage...)
have done it to one of my previous cars.... didnt keep it long enough to notice the difference.

RC, have you driven down King William Rd , Hyde Park yet? I never really understood what people were complaining about, until yesterday. I swear I almost had to slow down just to get rid of the noise it was that bad.

Paved roads + Potenzas = a lot of noise at 50km/h

It seems to me that the people who sell it say it has benefits - don't see it myself. Air is already 78% nitrogen, with 21 %oxygen + ~1% other gases. Nitrogen weighs a smidge less than oxygen, but we're talking a few grams per tyre here. Filling your tyres with dry air will prevent some pressure fluctuations due to moisture, but unless you're a F1 company, you aren't going to notice the difference. I always adjust my tyres in the cool of the morning, when the amount of moisture in the air is at its lowest.

I suspect that many motorists who do report economy improvements are really noticing a placebo effect - I've done something to the car, therefore it's going better. It could be that because people are expecting improved economy, they are unconsciously driving in a more economical manner.

I wonder how many "butt dyno" improvements are really just placebo effect? But then, I'm just a bitter twisted old cynic

King William Rd in Hyde Park has always been paved since I was a kid!

Why would you just go with the recommended tire pressure that is listed on the drivers side door for every vehicle made sold in the US? I know this assumes you have the size mentioned on that sticker, but do most of you not know that it's there.....and for a reason? Just Curious?

You should try the rough-seal roads here in New Zealand. The road noise on what is basically gravel glued to the road is horrendous...

Most manufacturer's recommendations are underdone for performance driving. They are often biased towards increasing ride comfort at the expense of handling.

Every defensive driving course I've done, the instructors have recommended increasing the pressure over the manufacturer's recommendation and/or tyre placard to improve braking distances and increase the car's ability to get out of trouble. I've seen the difference demonstrated right in front of me - seeing is believing.

Too many people think 30psi (often the 'default' recommendation) is some kind of universal standard that suits every tyre on every car. In my experience, this is not the case. Even your stock standard family sedan will have improved braking and handling with pressures of 34-36psi. I run our Mazda 6 at 34psi around town and 38psi on a long trip with plenty of freeway driving.

would it minimise understeer and maybe create abit of oversteer?
I used to run my old car like this and thought it had better turn in but also got abit loose sometimes.. ?

im running 34 all round on the 8 atm, 225's

Manufacturers generalise their pressures.

They dont take into account factors which influence the tyre. Such as the weather, the road conditions, the modifications on the car, and if you have a work car - the pressure when the work car is empty vs the pressure of a full load you must change accordingly, so forth.

Manufacturers test their pressures and base it in a confined environment, there is no possible way they could cater their pressures to everyones needs around the world. Melbourne roads are different to Sydney roads for example. So pressure I would run would be different to that of Sydneys (as their roads are quite crap ;))

Agree with what Revolver said aswell, at the driving courses which I did at same company as him, they do explain certain psi actually improves economy and reduces tyre wear.

I understand all that, but putting too much pressure in can be bad as well. For the record, my door sticker says 32psi and I run ~35psi. These numbers are only for the stock 225/45/18's and not applicable to every tire of course, but I just think that when someone is running 40+, that's a bit excessive and can actually hurt tread wear. Hell.......one guy said he had 60psi!!!!! :Eyecrazy:

depends, lower the profile, the higher the pressure.

if ur running stock which is 45 profile then 36/38 max

but im running profile 35 so i run 40-42psi for daily. if i put 32psi bye bye to my tyres in long run. but when we go tracking i lower it to 36psi as due to heat etc it will rise well about 40.

60psi in a stock rx8 tyre? hes crazy........

Nah we understood what you ment totally
And thats the questions I asked when I was first told to run 36-38psi on stock tyres. Why do manufacturers recommend what they do wouldnt they know more about their tyres then others? So yes understood what you ment, and something I argue wit my parents over too lol Im sure our discussion came valuable to some newbies anyways ;)

hey where did the post b4 mine go lol looks like im talkin to myself now