So, as the driver's handbook is no help to me can anyone tell me the preferred pressures for my 18's? I'm running 245/45/18 tyres, currently pumped up by the dealer to 31 on each corner. That seems a bit low as I had 33psi on the 17's on my old Vectra. I know some people use a 'rule of thumb' based on the tyre size (2x circumference +2, so for mine 36+2 =38psi) but not everyone agrees. What have you got yours set to? It's only me in it, so the car's not under load - despite what my wife says - and i do just normal motorway driving.
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I've only had the car a few months but have the same size tyres and i haven't noticed any uneven tread wear yet with having my tyres at 30/31. The manual says 31 for light load and 37 (could be 39) for heavy/eco.
On my last car (2003 A4 avant) i'm sure the manual said to have it at 2.4 bar (around 35psi i think) and the middles always wore faster than the edges so had to run them at 30 to try stop that.
2015 SRI 2.0CDTI ecoderp hatch
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Owners manual says for the 245/45R18 in the CDTi....
Comfort:
Front = 32PSI
Rear = 29PSI
Eco:
Front = 39PSI
Rear = 38PSI
Carrying full load:
Front: 32PSI
Rear: 39PSI
I usually run mine a bit above halfway between eco and comfort, so in your case I'd run at about 36PSI front and 34PSI rear.
It also allows a bit of leeway so temperature-related changes in tyre pressure don't raise or drop the pressure too far out of normal ranges, otherwise my TPMS will start nagging me.
Even driving for many miles at motorway speed will nudge tyre pressure up by a couple of PSI as the tyres warm up, especially the front tyres, so it's best to set tyre pressures before a long journey and on a day that's not unusually warm or cold..
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only this afternoon i was thinking to myself the 'ride' on my insignia (225/55R17) was a bit too harsh..originally put it down to the suspension...(isn't it supposed to be a bit firmer on the SRi ?),
anyhooo.. on my way home i dropped into local garage and checked the tyre pressures.. all four were at 58psi.. WTF!!!
dropped them back down to 32 psi... the car seems a lot 'softer' now, what the hell the dealer thought he was doing with pressures that high i'll never know..Chris
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Originally posted by nick.b View PostMine are 245/45/18 and were at 32 all round but I was getting rubbish mpg. Upped then to 38psi all round and while a little mpg difference I found it to be no noise or comfort difference.Chris
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245/45/18 I run 32psi all around. tpms did its job on my way to work the other day......bleeping at me and telling me my right rear has dropped to 17psi. Took a look and had a screw in it so drove to local tyre place and got it repaired.2017 Vauxhall Insignia Grand Sport Sri Nav 1.5 (165ps) Turbo petrol in Lava Red - Keyless entry and start - 18” five spoke alloy wheels - Front fog lights - Tinted rear windows - Aluminium sports pedals - Ambient interior led lighting - Front and rear parking assist - Active emergency braking - Forward collision assist - Front pedestrian alert - Traffic sign recognition - Lane keep assist - Cruise control - Speed warning and limiter - Voice recognition - Bluetooth - Duel zone climate control - Front and rear electric windows - High beam assist - Auto lights - Auto wipers - Wifi hotspot - 8” colour touchscreen Navi 900 with Android Auto, Apple Car Play and DAB
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Originally posted by Langy View Postonly this afternoon i was thinking to myself the 'ride' on my insignia (225/55R17) was a bit too harsh..originally put it down to the suspension...(isn't it supposed to be a bit firmer on the SRi ?),
anyhooo.. on my way home i dropped into local garage and checked the tyre pressures.. all four were at 58psi.. WTF!!!
dropped them back down to 32 psi... the car seems a lot 'softer' now, what the hell the dealer thought he was doing with pressures that high i'll never know..
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