Tyre pressure - low profiles

I'm running 205/40/17 tyres and so I decided to check my tyre pressure today.

I saw it was running at a what seems to very low 15psi!
I'm not sure what the pressure norm for low profile tyres are however I know that general tyres are at around 35 psi.

I did a test and pushed the side wall of the tyre (probably ineffective) to see how deflated it was and it seemed okay. When I pumped the tyre pressure up a bit it felt like the tyre was quite pumped so i left it at around 18 psi all round.

Can anyone confirm what the correct tyre pressure should be for low profiles all around?

I'm sure 18psi isn't the correct pressure....

i say pump it up to 38psi and increase/decrease the pressure to find the sweet spot
anything below 30psi for our cars is low i reckon

i personally run 36/33psi front/rear while cold on 195/55/15

I'm probably going to go out and pump it to 34 psi all round.

With low profiles I couldn't tell if they were flat. I'll head back out to the petrol station now :)

Cheers

Quote:

---

Originally Posted by DC4Integra98

I'm probably going to go out and pump it to 34 psi all round.

With low profiles I couldn't tell if they were flat. I'll head back out to the petrol station now :)

Cheers

---

yep low profiles are like that, they will look hard with stuff all PSI in it. just pump it up, it wont blow up on you

depends on how you drive... if you're like me and do a lot of highway driving, 38 is best... easy on the fuel...

I'm running 215/35/18s and I have them up at 38 - 40psi depending on the weather. In warmer weather I take them down to 38 or less because the heat in the road will inevitably increase the pressure in the tyres due to thermal expansion. Yeh, the ride might be a little more bumpy than normal but it will depend on the roads you drive on and will benefit your fuel efficiency by a little. I reckon the minimum you run on would be 35, but it all depends on what you like. You don't want to hit a pothole having under inflated tyres and cracking one of your rims, being the worst case scenario and costing you more in the long run.

Buy a good tyre pressure gauge, don't trust the guages on garage pressure hoses, they are often widly inaccurate. Check tyre pressures at home in the morning when the tyres are cool (not heated up by driving) and before any of the tyres have been warmed by the sun (a tyre can gain a couple of psi just from being warmed by sunshine). Buy a tyre pump so you can adjust pressures at home.

35psi ish (cold) would be a good starting point. It won't be 'too much' and it won't be 'not enough', but what is 'best' varies hugely with the exact tyre, the width of the wheel to which that tyre is fitted, the car to which that tyre / wheel combination is fitted, and on driver preference for softer ride over steering / handling or steering / handling over softer ride...

My car has a mix of tyres (on 6.5" wide wheels) with 195/60/15 on the front and 205/55/15 on the rear. I don't mind a harsh ride quality (I actually dislike a plush ride feel), and I have the fronts at 42psi, and the rears at 47psi. These pressures are found by experimentation and are different because each different tyre has different characteristics, and these characteristics are also affected by the rim width.

The wider rear tyres 'like' the higher pressure because the rim is a bit narrow for the tyre width and the sidewall is to some degree laterally unstable unless the tyre is pumped up pretty hard. The narrower front tyres 'like' the somewhat lower psi because they are a more suitable width for the wheel width, and thus the sidewalls behave in a more stable / responsive manner so don't need as much psi to behave well.

And, in case anyone asks, I have the wider tyres on the rear (rather than on the front which might at first glance seem more correct) because they don't steer as crisply as the narrower tyres do. The car handles better with the narrower 195 tyres on the front because the sidewalls are effectively stiffer on the 6.5" rim than is the case with the wider 205 tyres (even with the higher psi in the 205 tyres). When it comes time to replace the 205s I'll be getting 195s. Ideally I'd keep the 205 tyres but fit them to 7" or 7.5" rims, but $s being $s...

I love JohnL's explanations for everything. +1!

15PSI, dude thats like a flat tyre....

i would say 42psi all round..

low profiles usually require a few psi more than "normal" tyres but beware if you have crap tyres and you over inflate them.... can end up with eggs, sorta like when you kick a basketball really really hard

For 205/55 R16, I use 36 psi all round. So for your 205/40 R17, I'd go 38 psi or thereabouts. I agree with JohnL, get your own tyre pressure gauge and use that instead. The gauge at the pump might be stuffed.

Quote:

---

Originally Posted by aaronng

For 205/55 R16, I use 36 psi all round. So for your 205/40 R17, I'd go 38 psi or thereabouts. I agree with JohnL, get your own tyre pressure gauge and use that instead. The gauge at the pump might be stuffed.

---

^^ this. I have 205/40r17's and run 38 psi for daily driving. If you're still unsure what pressure to use ask V__ what he recommends, as he works for Bob Jane.