Tire pressures with plus size tires

[Nederlander75]

I have installed 225/45/18 in place of 215/45/18 on a 3600lb AWD car. OEM pressures are recommended at 38PSI and I was previously running mine at 41 for high mpg and firmer ride. Would it be safe to say that 41psi is still good or could/should I go higher/lower?

Thanks

 

[rshunter]

Originally Posted By: Nederlander75
I have installed 225/45/18 in place of 215/45/18 on a 3600lb AWD car. OEM pressures are recommended at 38PSI and I was previously running mine at 41 for high mpg and firmer ride. Would it be safe to say that 41psi is still good or could/should I go higher/lower?

Thanks
Here's the Continental Tire advice on plus sizing...

http://www.conti-online.com/generator/ww...plus_sizing.pdf

Cheers

 

[CapriRacer]

Technically this is "Oversizing".

Plus sizing would be going from 215/40R18 to 225/35R19 (+1) or 235/35R18 (+0). If done correctly, Plus sizing should need no adjustment in inflation pressure (except to say, that the rim is more prone to impact damage, so may be a few more psi will prevent some of that).

In theory, you could use lower inflation pressures, (my calculations say 3 psi) but since you are using more pressure than the placard to begin with, why not back down to the placard?

 

[Nederlander75]

Thank you both. Very helpful.

 

[ARB1977]

Originally Posted By: CapriRacer
Technically this is "Oversizing".

Plus sizing would be going from 215/40R18 to 225/35R19 (+1) or 235/35R18 (+0). If done correctly, Plus sizing should need no adjustment in inflation pressure (except to say, that the rim is more prone to impact damage, so may be a few more psi will prevent some of that).

In theory, you could use lower inflation pressures, (my calculations say 3 psi) but since you are using more pressure than the placard to begin with, why not back down to the placard?



Everyone who ive talked to regarding placard pressures say disregard mine. 26 front 29 rear...this is in the Tacoma. This seems too low to me.