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post #1 of 9 (permalink) Old 10-02-03, 04:36 AM Thread Starter
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18" tyre pressures?

225/40 and 255/35 ZR 18 Falken tyres on an AU.

What tyre pressure should these be run at for normal street driving?


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post #2 of 9 (permalink) Old 10-06-03, 04:23 AM
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Re: 18" tyre pressures?

Same as any tyre per decal in the car.

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post #3 of 9 (permalink) Old 10-06-03, 05:03 AM
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Re: 18" tyre pressures?

I run my 235/45/17s at 38 front and 36 rear in winter, and 40 front and 37/38 rear in summer. This helps reduce the uneven wear on the tyres. I would guess with 18s, you would want to run about the same (ie around the high30s to 40psi).


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post #4 of 9 (permalink) Old 10-06-03, 05:18 AM Thread Starter
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Re: 18" tyre pressures?

Blue - my tyre decal doesn't list non-factory sizes...

JC - That high? Wow, I currently have 35 in them and was hoping to hear somewhere around the low 30s. Oh well, I'll go and add a few pounds. Thanks!

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post #5 of 9 (permalink) Old 10-06-03, 05:28 AM
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Re: 18" tyre pressures?

40 psi for the 18's,thats what i was told by the tyre dealer for my 18's..

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post #6 of 9 (permalink) Old 10-07-03, 05:45 PM
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Re: 18" tyre pressures?

Out of curiosity, what does ford recommend for the factory 18's on the BA ? I've always been told run 38 or so in the 17's i've got, but it'll be interesting to see what the factory reckons

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post #7 of 9 (permalink) Old 10-07-03, 06:29 PM
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Re: 18" tyre pressures?

For 18's the factory says
30 front / 30 rear for normal load
35 front / 39 rear for max load.
At that the edges of my tyres were wearing badly (sign of under inflation) My tyre guy suggested 36 to 38
I now run 38 all round

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post #8 of 9 (permalink) Old 10-07-03, 08:12 PM
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Re: 18" tyre pressures?

I never take too much notice of the factory decal as they’re always to low to make the ride nice & soft
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post #9 of 9 (permalink) Old 11-07-03, 03:46 PM
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Wink Re: 18" tyre pressures?

Originally Posted by Q777
225/40 and 255/35 ZR 18 Falken tyres on an AU.

What tyre pressure should these be run at for normal street driving?

My first post!

When I purchased tires for my lowered '95 Ranger, I called nearly everyone in the tire business that I knew. There is no easy answer.

My own experience with this subject, been doing the car thing since '72, and never getting anything but standard responses from those that I thought should know, caused me to developed my own theories.

In the past and with older tire designs one usually obeyed the 'door sticker.' I've come to believe that this pressure is only for OEM tires the same size or close to that size bought from aftermarket suppliers.

It is the load ratings that are the limitation on safe pressures in regards to tire design!

A tire that has a max load rating achieved at say 40psi for example and is used at 30psi if a 'door sticker' is to be believed, has a decrease in that load rating of 1/4 of it's max rating. Now I'm sure this is on a curve of some kind as the load rating at 20psi might be only 1/5 of the max. but the numbers will suffice for this discussion.

The Sumitomo HZR IIIs on my Ranger have a max pressure of 51psi. I cannot remember the load rating and am too lazy to go out there and look, but that load rating is achieved at 51psi. Reduce the pressure and you reduce the load the tire can safely carry.

Given this a tire that has a higher max pressure should be run at a higher pressure than a tire with a lower max pressure and all this is tied to the maximum load capacity of the tire.

Throw in the actual load the car or truck puts on each tire, and this might vary considerably, and you've only begun to reason the answer to the question. The combinations are nearly endless!

Every axle must me independently evaluated as to the load it will carry and the PSI is the only variable the mechanic/driver can influence.

Now, after all that, I run mine at 40psi because I get a darn headache just thinking about this!

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