Tyre Pressures For 18" ?

[Munkyb0y]

I have 18" 235/40 at the front, and 18" 265/35 at the rear.

My mechanic told me 34psi all round. (By the way, he's an idiot, wont be using him anymore. Stuffed my timing belt fitting. But that's another post).

My rear tyres look nice and pumped, but my fronts look a bit low.

What pressures do you guys use with same tyre sizes?

I know it's been asked before, and yes i searched, and read the posts, but alas, here we are.

Couldnt get a straight answer. Very differing opinions.

I am just using it for street driving, no drag, no track.

cheers

[blind_elk]

The tyre manufacturer should have recommendations for pressures to run with the particular tyres you have.

Then add 2psi to the fronts.

[Al]

I use 38psi.

You can actually damage the tyres, on the inside, from having the pressure too low.

[Munkyb0y]

I use 38psi.

You can actually damage the tyres, on the inside, from having the pressure too low.

Is that for 18", similar size?

A friend of mine just bought an Ford FPV Turbo 6. He has 19" from the factory. The tyre placard says 38psi.

That's what got me thinking. Also the jarring shocks from the cr4ppy sydney roads feel awful through my front tyres.

[Al]

I have 19's, but with the same tyre profile you use.

[cowie165]

Far out. I've been using 40psi in 245/40/18s for over a year now. D'oh.

I might give 36psi a try for a few weeks

[Munkyb0y]

The strange thing is that my rear tyres (265/35/18) look well and truly pumped at 34psi.

where as the front (235/40/18) look kinda flat at 34psi.

is this because of the different series?

I think i remember something about bicycle tyres, especially thin racing type, use a higher psi. Probably because there's less area to fill, so the pressure is greater inside. Not sure what the theory on all that is.

i'm going to try 38 at the front, but might leave the rear on 34 for now.

[Munkyb0y]

Running 38psi all round now.

Seems like a good call.

Apparently, low profile, higher psi. That's what i was told... here and out there. Even 40psi would be ok.

Has to do with the sidewalls being less able to support themselves, higher psi helps keep them in check.

something like that anyway. plus i'm running nankangs, and these have got weaker nylon sidewalls, apparently.

So cowie165, maybe 40psi was ok. Have you had any probs with uneven wear (in the middle) at that pressure over the last year?

[Al]

No need to say thanks

[Munkyb0y]

Thanks Al

[Al]

lol

[cowie165]

Hi Tony,

The tyres are Federal SS595s with 7,000km and they are wearing evenly, which is great to see

The lack of sidewall flex you mentioned is the reason I was using 40psi. Hrmmm. As an aside, it's a higher pressure but lower volume than smaller size (15", 16" etc) tyres (ideal gas equation).

Mark

[Al]

40psi is also an accepted tyre pressure for 18's/19's

[cowie165]

Thanks Al

seriously though, cheers. It is good to know I've been doing the right thing

[Munkyb0y]

Al....what pressure were you running in that pic of yours?

lol.

but seriously, you're making me wanna go out and destroy some tyres.

damn that's a teaser.

[JUNR34]

Since we are on kind of the same topic how much do you guys recommend on 235/45R17? Been using 38 guess Ill have to lower it now, just wondering would this actually ruin the tyres in anyway if you have it too high?

[Munkyb0y]

Since we are on kind of the same topic how much do you guys recommend on 235/45R17? Been using 38 guess Ill have to lower it now, just wondering would this actually ruin the tyres in anyway if you have it too high?

My concern would be bloating the tyre, and therefore wearing the center tread prematurely.

But lets see what Al says. lol.

[cowie165]

My concern would be bloating the tyre, and therefore wearing the center tread prematurely.

But lets see what Al says. lol.

You brushed on a good point there. A lot of guys new to sports cars believe that higher pressures = improved handling.

Whilst that may be true for your family mobile with a tyre placard suggesting 26psi for the Camry, sports cars generally already have higher pressures. Increasing them further bloats them just like you mentioned Tony and you actually end up with a smaller contact surface than if you ran them ~4psi-over-recommended. You need to find that nice happy medium

[Al]

Unfortunately i am no tyre expert, just learnt through asking and experience.

What Munkyb0y wrote is spot on, but with 17's i do run 36-38psi.

[Al]

Al....what pressure were you running in that pic of yours?

lol.

but seriously, you're making me wanna go out and destroy some tyres.

damn that's a teaser.

Provided it is in a "controlled" environment