Author Topic: Tyre pressures for 18" tyres??  (Read 4207 times)

Steve McF

  • Viggen
  • ****
  • Posts: 1636
  • Number of thanks: 10
  • 9-5 2.0LPT.....as was, and now 9-3ss 2.0T Aero :)
    • View Profile
Tyre pressures for 18" tyres??
« on: 07 February 2018, 10:04:05 PM »
I can find out the tyre pressures for the standard 9-3ss Aero tyre size (17"), but what tyre pressures should I use if I have 18" tyres fitted? (which of course, I do  ::) )

Would it be the same?

Am I being thick?? :D

sgould

  • Aerobic
  • SST paid up supporter
  • Overboost
  • *
  • Posts: 5388
  • Number of thanks: 345
  • 2006 9-5 Aero estate - Hirsched.
    • View Profile
    • Christine Bennett - soprano
Re: Tyre pressures for 18" tyres??
« Reply #1 on: 07 February 2018, 11:30:47 PM »
I prefer slightly higher pressures than the ones recommended in the list on the label on the glovebox lid.  Somewhere halfway between the recommended and the ones listed for max load and speed.  Around 38 psi.

The 18 inch tyres I keep at the same as the 17 inch ones.  I asked Hirsch when i fitted 18 inch to my 9-5 and they said that they should be the same.
Help support SaabTechTalk by making a Lump Sum donation or by opening a subscription. 
Options available are in your Profile/Actions.

Steve McF

  • Viggen
  • ****
  • Posts: 1636
  • Number of thanks: 10
  • 9-5 2.0LPT.....as was, and now 9-3ss 2.0T Aero :)
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #2 on: 08 February 2018, 07:53:00 AM »
Thanks Will - I'll check them and see what they're at, using the 17" pressures as  the guide for starters ;)

Norfolk Jim

  • SST paid up supporter
  • Viggen
  • *
  • Posts: 1748
  • Number of thanks: 27
  • No longer Saab now Nippon Express 4x4
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #3 on: 09 February 2018, 08:46:25 AM »
18" on my 2009 9-3 Aero are 35 psi.

That's what it says on my plate and in my book and they've been fine

Steve McF

  • Viggen
  • ****
  • Posts: 1636
  • Number of thanks: 10
  • 9-5 2.0LPT.....as was, and now 9-3ss 2.0T Aero :)
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #4 on: 09 February 2018, 03:56:15 PM »
Just had a look in the glovebox and it says normal pressures for standard 17" tyres is 35psi too, so sounds about right :)

sgould

  • Aerobic
  • SST paid up supporter
  • Overboost
  • *
  • Posts: 5388
  • Number of thanks: 345
  • 2006 9-5 Aero estate - Hirsched.
    • View Profile
    • Christine Bennett - soprano
Re: Tyre pressures for 18" tyres??
« Reply #5 on: 15 February 2018, 12:57:07 PM »
This morning I was checking over the Carlsson and read the driver's handbook!! :)

I've not seen this before, but the list of recommended tyre pressures is not quite the same as the list in the glove box.

In the handbook there is an additional line. The basic pressures are 35 and the loaded/high speed pressure is 41. The same as the glovebox.  The extra line says "For improved fuel economy 41 psi".  I suspect that the higher pressure will improve the economy at the expense of the tyre life, as they will wear faster in the centre.
Help support SaabTechTalk by making a Lump Sum donation or by opening a subscription. 
Options available are in your Profile/Actions.

Norfolk Jim

  • SST paid up supporter
  • Viggen
  • *
  • Posts: 1748
  • Number of thanks: 27
  • No longer Saab now Nippon Express 4x4
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #6 on: 15 February 2018, 01:27:32 PM »
And a hard as nails ride no doubt!

Audax

  • SaabTechTalk Team
  • Wide open throttle
  • **
  • Posts: 3332
  • Number of thanks: 207
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #7 on: 15 February 2018, 04:40:10 PM »
And a hard as nails ride no doubt!

I've found that increasing tyre pressure can improve the ride, I'm guessing that this is because the suspension does it job instead of the tyre which can make things better. Does depend on the tyre and the car though, at some point a too high pressure will make it bad. The tyres I used to have on the 9-5 were best at around 40psi, the michelins on the 9-3 are good at around 38psi. Never had a problem with centre wear either.

Norfolk Jim

  • SST paid up supporter
  • Viggen
  • *
  • Posts: 1748
  • Number of thanks: 27
  • No longer Saab now Nippon Express 4x4
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #8 on: 16 February 2018, 10:36:37 AM »
If I pump my Nokian WRD4's up above 35 the ride does get noticeably firmer and I my suspension has only done about 9k. However if they go much below that the ride is also bad so 35 seems the sweat spot!

Audax

  • SaabTechTalk Team
  • Wide open throttle
  • **
  • Posts: 3332
  • Number of thanks: 207
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #9 on: 16 February 2018, 07:47:21 PM »
I recall similar with my nokian wr-g2, below the magic number the car was like a bouncy castle, above it resulted in poor handling and ride. Think it was 37 psi for my 9-5 2.0t estate.

Steve McF

  • Viggen
  • ****
  • Posts: 1636
  • Number of thanks: 10
  • 9-5 2.0LPT.....as was, and now 9-3ss 2.0T Aero :)
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #10 on: 21 February 2018, 10:40:31 PM »
Checked the tyres tonight - 27 - 28psi in each of them, now all filled to 35psi. Will see how we go ;)
« Last Edit: 26 February 2018, 10:12:09 AM by Steve McF »

Norfolk Jim

  • SST paid up supporter
  • Viggen
  • *
  • Posts: 1748
  • Number of thanks: 27
  • No longer Saab now Nippon Express 4x4
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #11 on: 26 February 2018, 09:38:31 AM »
You'll knacker your wheels if you hit something at that low pressure Steve. That's way to low. Mine would squirm that lower pressure. 4 wheel steer would go overtime

Steve McF

  • Viggen
  • ****
  • Posts: 1636
  • Number of thanks: 10
  • 9-5 2.0LPT.....as was, and now 9-3ss 2.0T Aero :)
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #12 on: 26 February 2018, 10:13:42 AM »
Yeah, they were all consistently at around 27psi, so I pumped them all up to the recommended 35psi now.

Car seems to be OK, tramlining much reduced since the tracking has been sorted and now the tyre pressures are at the right level.

Norfolk Jim

  • SST paid up supporter
  • Viggen
  • *
  • Posts: 1748
  • Number of thanks: 27
  • No longer Saab now Nippon Express 4x4
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #13 on: 27 February 2018, 10:46:41 AM »
Yeh the 18" wheels are rare beast to get hold of (I think called 10 spoke) and I hit a pothole last year and made a dent in wheel; that's on the back balanced out thankfully but trying to find a spare is nightmare and £££'s so be careful

Steve McF

  • Viggen
  • ****
  • Posts: 1636
  • Number of thanks: 10
  • 9-5 2.0LPT.....as was, and now 9-3ss 2.0T Aero :)
    • View Profile
Re: Tyre pressures for 18" tyres??
« Reply #14 on: 27 February 2018, 11:12:05 AM »
Hi Jim,

well mine aren't Saab 18" wheels, so wasn't sure what the pressures were supposed to be. They were on the car when I bought it, and were apparently on the car when the previous owner bought it back in about 2012.