Hi all
my son has fitted 18" wheels to his vectra 1.8 sri with 225/45/18 tyres fitted we know these aren't exactly the correct size but they are like new so will do for now can anyone tell me what tyre pressures to put in please?
Hi all
my son has fitted 18" wheels to his vectra 1.8 sri with 225/45/18 tyres fitted we know these aren't exactly the correct size but they are like new so will do for now can anyone tell me what tyre pressures to put in please?
have you ever wondered how tyre fitters know the correct psi every time,the rule of thumb is double the wheel size and add 2 psi so for your sons car 36 plus 2 psi
and on any wheel size max 40 psi if you want to roll economy all the time... it actually gives you enough to carry heavy loads and gives enough contact without having the tires have weird uneven ware... i use 40psi all the time and my average town driving has seen an improvement of 2mpg in 2 weeks time when i started doing it... kept it like that ever since... This was on my previous car though my vectra got 40 psi from the moment i stopped at a petrol station when i bought it to fill the tank up, they were on a mere 35 PSI.
Last edited by northpole; 15th August 2019 at 08:09.
My 2007 handbook says they are the correct size for 18" wheels with a 1.8 engine. The recommended book pressures don't agree with the 2 x wheel size plus 2 psi rule of thumb.
pressures.jpg
iv used double rim size plus 2psi for near on 40 years now and never had an issue with uneven wear
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