Manager Forum

hey yall, I was wondering if anyone has a mathmatical formula fo correct tire pressure when changing to bigger tires, 31x10.5 for example. I've always gone by the placard on door but sometimes tire looks low or wears on edges. Anyone have any thoughts? Bob in sc

if all else fails i go with the recommended tire pressure on the side wall. tire racks web sight offers support, one of my shop systems offers tire pressure specs. if i'm going out of oem range for tires i look to the supplier for pressure advise. as a rule it varies for usage. you mentioned the outsides wearing so obviously it's an under inflation issue so i would increase the pressure (depending on the tire size) 10 lbs. like i said above, i'll always fall back on the tire pressure on the sidewall. some tires will offer pressures depending on vehicle weight.

The issue with sidewall pressures is that they are for the MAXIMUM load, which most vehicles don't even come close to. I'd start with placard pressures and adjust from there. There must be a better way, though.

Agreed Ric, that was what I was looking for. Tried Googleing it and somebody in Europe had some sort of formula. Seemed a bit complex for this simple country boy.

i'm by no means stating that the maximum is my first choice. it's if all else fails. some times my feeling are "customer choice to change tire sizes and styles, customer issue". i will not allow myself to get into a pressure issue where suddenly it's my issue for advanced tire wear. times have changed. you just can't slap any tires that you feel will look cool on your vehicle. a lot of issues can be forced by doing this. man., i don't know what's effecting my attitude here but i feel like a negative ned.

Good point, Steve. We need to remember that the customer accepts ALL responsibility when changing tire sizes. We're here just to keep wear to a minimum and handling to a maximum. Those extremes will be unique for each customer and the challenge will be getting them to understand and accept that.

I guess at this point, educating the customer on tire wear and pressures then letting them decide seems to be the SAFEST way to decide on pressure. Didn't mean to bring ya down Steve. lol. thanks for the input guys.

you say bigger tires... 31x10.50.... what vehicle are these on? what lift was done to allow these 31's? is the wear on all tires about the same? does the wear seem more on p/s or d/s? or is it the front tires? is it outer or inner edges that wear?