Tyre Pressures

[kenny999]

Just had 17" wheels with 205x40x17 Nito tyres put on my Mazda 2, would the pressures be the same for the standard tyres? standard pressures are 32psi ft 34psi rear.

Also spare wheel is standard 15" so will there be a problem using this with 17" wheels should a puncture occur.

Cheers for any replies..

Edited February 12, 2011 by kenny999

[MoonRiverOasis]

would the pressures be the same for the standard tyres?

Depends on the Load Index.. if it's the same for the old and the new tires, the same pressures should be used. If the Load Indoex differs, you'll need to adjust the pressures.

The basic rule of thumb is:

• If the load index of the new tires is higher: reduce the pressure by 1 PSI per point difference
• If the load index of the new tires is lower: increase the pressure by 1 PSI per point difference

Load index is the 2 or 3 digit number on the left:

Also spare wheel is standard 15" so will there be a problem using this with 17" wheels should a puncture occur

The rolling diameter should not have changed by any more than a couple of percent, so you won't be risking any mechanical damage, but handling and braking will likely be compromised with the spare on though, so suitable caution needed.

Edited February 12, 2011 by MoonRiverOasis

[kenny999]

would the pressures be the same for the standard tyres?

Depends on the Load Index.. if it's the same for the old and the new tires, the same pressures should be used. If the Load Indoex differs, you'll need to adjust the pressures.

The basic rule of thumb is:

• If the load index of the new tires is higher: reduce the pressure by 1 PSI per point difference
• If the load index of the new tires is lower: increase the pressure by 1 PSI per point difference

Load index is the 2 or 3 digit number on the left:

Also spare wheel is standard 15" so will there be a problem using this with 17" wheels should a puncture occur

The rolling diameter should not have changed by any more than a couple of percent, so you won't be risking any mechanical damage, but handling and braking will likely be compromised with the spare on though, so suitable caution needed.

Thanks for the reply, one more question dealer says petrol 91 or 95 so I assume 91 will be fine garage calls this Gasahol which I assume is 91..

[WarpSpeed]

Not likely as they are low profile tires and require much higher pressures to provide enough stiffness support for the side wall..