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

Agreed............Yeah, I'm not running stock either, but my first comment was based basically on stock as I assumed the thread first started with. Actually, now that I re-read it, it was this one and another thread about tire pressure but.....if people are very close to 40(assuming when cold....and maybe I shouldn't have), then 38 to 40psi could be a little much on stock size. I guess that's all I was trying to say. No Worries!

Ha Ha.......I edited and moved it because I realized the guy with 60psi wasn't in this thread at all........I could go find it, but too lazy! :ylsuper:
Do you talk to yourself often? :yelrotflm

When I fitted my tyres (245's), I emailed the tyre company's technical department in Europe, who recommended 260kPa (~38psi). As I keep on saying, the most important criterion is even tread wear. Too low pressure = edge wear. Too high pressure = wear in the middle. Not a bad idea to measure tread depth across the profile from time to time.

Couldn't agree more.

This is what I was getting at Mazsurfer - it's horses for courses.

I wouldn't run 40psi in 45 profile rubber but I would with 35 profile tyres.

For the record, I'm not stock either - 235/40's on 8.5 rims.

I reckon 34psi is the absolute minimum for the stock rubber for road use, even on poorer roads.

But the general message remains the same, hence the point of the thread. Check your pressures regularly and ensure you have optimum psi for your chosen rubber/rim/suspension combo. It really does make a lot of difference in this car.

Agreed. :rock:

I do I do.................. :rock: The voices talk back aswell :banghead: :cwm27:

That has to taken the camber angle to account!

Revolver, for out Michellin, 38 psi with 2 degree camber is slightly too much centre wear!
36psi is AOK http://i97.photobucket.com/albums/l2...es/smoking.gif

Thanks Taka. I haven't noticed centre wear from running at 38psi on the freeway but then again I don't do an awful lot of it. Are you running 8.0's though? Might be a small difference as a result.

I'm happy with 36psi generally.

Oh yes, yours are 8.5. I do think that narrower rim gives more shoulder wear http://i97.photobucket.com/albums/l2...lies/dunno.gif.

http://i97.photobucket.com/albums/l2.../attention.gif Revolver, dail the neg camber as much as you can on the front. I ain't seeing any abnormal tyre wear on the inner side of my Michellin. I am at -2.5 front, and -2 rear. That has been going on for more than 15000km.

Some Porsche owner told me -2 camber is not a big figure. He does not know what his is exactly, but Porsches 911 has a more agressive settings and they use OEM Michellin PS2.... with rountine check on tyre on the 20000km service. So they do not expect bad wear.... although our suspensions are diff from Porsche (Tein and MazdaSpeed >>>> than OEM Porsche haha) but it is worth a go.

So no fear I would say http://i97.photobucket.com/albums/l2...lies/crash.gif, what is your setting atm?

slightly off topic, ur pictures crack me up Taka hahaha I spend more time tryin to figure out what word was spose to fit there ;)

Yes I reckon it does but I really like that characteristic, used to it really.....harks back to my rally days!!! :rock: :rock: PLus I am getting really good wear out of the tyres even though I hate them.....I know I am harping on about them but they suck!

Yes I know that road is a shocker.....wait till you have hit 15,000kms and then commiserate with me.....

BTW I met with another 8 fan....NT Rotorhead the other weekend for a coffee....I will send you a message next time and see if you can make it..... Lazy seems to be MIA at the moment and I'm not sure where the others AMG etc have gone too..... :wavey:

Firstly, I'm with Kall. I'm not sure I talk your smilie's language. :crazy: :scratchhe :D:

Otherwise, I asked for -1 all round when I got the MS stuff installed. But who really knows wtf they ended up doing. I've been thinking of going back just to have the suspension checked now that it's been installed for a while (e.g. check everything is still securely fastened, etc - it gets a pounding on Sydney's goat tracks), so I might get them to check the camber again.

Personally, I think -2 or -2.5 is a bit too aggressive for street use but you seem to be going okay with it. I'll think about it. Thanks for the feedback.

I was given this 6 DVD set called 'Out of Control' ages ago and hadn't bothered to start watching it until last weekend. It consists of hundreds of rallying stacks and near misses, with a bone dry commentary from some northern England bloke.

It gets a bit repetitive but some of the stacks are truly spectacular. Those crazy Finns! :D:

BTW, it's not some snuff movie. Apparently, none of the stacks shown resulted in serious injury.

Rally fans would love it. I'll try to remember to bring it to the Nats.

Meanwhile, I've got 5 discs to go :crazy: ...

A good pressure gauge is less than $20.
I have a $100 compressor and fill them at home.

I used to put high pressures in my Holden with Turanza 225/55s but the insides of the tyres wore out way too fast. The only way I could get even wear was at 28 psi.

An excellent tyre gauge cost a lot more ;).

Low pressure for even wear? It is not the problem with your gauges, it is the problem with the tyres!

Actually with Holdens it is a problem with the suspension. A lot of torque, a lot of weight and a primitive suspension system.

After reading my thread, I realised I should maybe up my tyre pressures. I have always been keeping mine at around about 32psi as per manufacturers recommendations and never thought to put them up to 36-38. Put them upto 36 the other day and damn, what a difference, car feels a lot sharper, and even rides a lot better... so thanks for this thread guys (and MissyK :p) :D

Scotland is cold.... 36psi is diff volume of air ;)

hmm what tyre pressure would u guys suggest me trying/running?

235/45/17 front
255/40/17 rear

Tyres are bridgestone s03

im currently running 36psi all round, and the car doesnt feel right - it feels twitchy
i have tein flex on my car, spring rate front is 5 and rear is 4.

car is a s15 btw ~

Er try a S15 site?This is an RX-8 site....

thx for your informative input

He wasn't being rude, just observing that you may get more accurate information from people who own and drive the same car.

Lol, so is 36psi too high then??