random tire pressure question

[Vinsanity]

So about a week ago, I had a fresh set of tires installed on the Caddy. 255/35/20. The guy at the shop inflated them to 30 psi, which seems pretty low for a low-profile 20" tire, considering the original weaksauce 16" wheels from the factory had tires inflated to 27 psi. I'm concerned this time around because that same shop that installed my tires said that one of my old tires were damaged from driving on low air pressure.

Anyone know off the bat what the proper air pressure should be for a 255/35/20 tire? I kept the old tires at 40 psi, but I just found out that too much air pressure can damage the rim during the event of a pothole impact, which is exactly what brings me to where I am now. Halp!

[hotrodalex]

I always do 35 psi.

[Byteme]

So about a week ago, I had a fresh set of tires installed on the Caddy. 255/35/20. The guy at the shop inflated them to 30 psi, which seems pretty low for a low-profile 20" tire, considering the original weaksauce 16" wheels from the factory had tires inflated to 27 psi. I'm concerned this time around because that same shop that installed my tires said that one of my old tires were damaged from driving on low air pressure.

Anyone know off the bat what the proper air pressure should be for a 255/35/20 tire? I kept the old tires at 40 psi, but I just found out that too much air pressure can damage the rim during the event of a pothole impact, which is exactly what brings me to where I am now. Halp!

I'd be inclined to contact Tire Rack and ask them for their recommendation. Be prepared to give them information on the car, wheel size (diameter and rim width) and tire make and size.

[Vinsanity]

Thanks for the suggestions. Luckily, I did happen to order the tires from Tire Rack, so I emailed the sales rep assigned to my order. He responded in saying that the tires should be inflated to the manufacturer's O.E. specs, regardless of wheel/tire size, as long as it meets engineering criteria, etc. For my car, this happens to be 33 psi. Incidentally, I'll probably need to fill the gas tank tomorrow, so good opportunity to put a little bit more air in the tires.

[93JC]

Go by what the manufacturer says on the sticker in the driver's door jamb.

40 psi is way too high.

[Vinsanity]

Go by what the manufacturer says on the sticker in the driver's door jamb.

40 psi is way too high.

last time I ever make that mistake

for some reason, I thought that low-profile tires needed higher air pressure than normal ones.

[93JC]

33 psi in a low profile tire is the same as 33 psi in a tire with more sidewall.

[hotrodalex]

Low profile tires don't need more pressure, but you have to make sure they stay at the recommended pressure and don't get low.

[cawimmer430]

You what annoys me about BMW owners manual? They don't tell you what oil your car uses and they don't tell you what tire pressure you're supposed to have in your car with different driving styles. The last time the 118i needed oil (warning light) I had to stop at a gas station and make a complete fool of myself by asking the hot chick cashier what oil a gasoline BMW 1er needs. 

In our Mercedes' manuals they tell you loud and clear which oil your car requires and what your tire pressure should be if you tend to drive alone or with another person onboard or with three people and luggage etc. Various scenarious are presented and the appropriate tire pressure. Now that's great information.

[Vinsanity]

You what annoys me about BMW owners manual? They don't tell you what oil your car uses and they don't tell you what tire pressure you're supposed to have in your car with different driving styles. The last time the 118i needed oil (warning light) I had to stop at a gas station and make a complete fool of myself by asking the hot chick cashier what oil a gasoline BMW 1er needs. 

You could totally have used that as a flirting opportunity.

"You see that hot little Bimmer out there? That right there is my baby, and you seem like just the right kinda lady that can help me out..."

[Raza]

So about a week ago, I had a fresh set of tires installed on the Caddy. 255/35/20. The guy at the shop inflated them to 30 psi, which seems pretty low for a low-profile 20" tire, considering the original weaksauce 16" wheels from the factory had tires inflated to 27 psi. I'm concerned this time around because that same shop that installed my tires said that one of my old tires were damaged from driving on low air pressure.

Anyone know off the bat what the proper air pressure should be for a 255/35/20 tire? I kept the old tires at 40 psi, but I just found out that too much air pressure can damage the rim during the event of a pothole impact, which is exactly what brings me to where I am now. Halp!

I don't think that's a generalization any of us can make.  My Passat's tires were 35, my Jetta's are 35, my Benz was 29.  195/65/15, 225/40/17, 215/55/16.  There's no pattern there. 

My brother's S4 takes 40 on 19".

[cawimmer430]

You could totally have used that as a flirting opportunity.

"You see that hot little Bimmer out there? That right there is my baby, and you seem like just the right kinda lady that can help me out..."

You should write a book on "automotive dating/pick-up lines". 

[AutobahnSHO]

My subie uses 32psi front, 30psi rear on little 14in rims.
The Sienna is the same front/back but I don't remember what it was (that's what the stickers are for). Low 30s.

[AltinD]

You what annoys me about BMW owners manual? They don't tell you what oil your car uses and they don't tell you what tire pressure you're supposed to have in your car with different driving styles. The last time the 118i needed oil (warning light) I had to stop at a gas station and make a complete fool of myself by asking the hot chick cashier what oil a gasoline BMW 1er needs. 

In our Mercedes' manuals they tell you loud and clear which oil your car requires and what your tire pressure should be if you tend to drive alone or with another person onboard or with three people and luggage etc. Various scenarious are presented and the appropriate tire pressure. Now that's great information.

Have you checked the fuel door? Most probably the sticker with the tire pressure recomandation would be there ... or perhaps on the side of the driver's door.

[S204STi]

The only time you need to worry about bumping the pressure up is to compensate for tires which have a lower load capacity than OE spec, or if you're trying to tune the handling of the car.  I would check the load rating of each tire (in terms of lbs/tire) and compare to the placard.  If they're lower, Tire Rack does have a chart showing you what pressures to run in order to compensate.

[S204STi]

Ah, this chart is based more on high-speed driving, but it still may be useful to you:

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=72

[Laconian]

I think the reason they specify the oil and tire inflation specs on a sticker and not in the manual is because they don't want to have to print a different manual for every configuration.

[S204STi]

Or have a wall of info in the manual for every available configuration. 

[AltinD]

Or have a wall of info in the manual for every available configuration. 

Not convinient when the car is avbailable with like 10 different engines, as many European cars are.

[Eye of the Tiger]

Not convinient when the car is avbailable with like 10 different engines, as many European cars are.

I like choices. I may want a 1.0L 3-cyl turbodiesel in one midsize sedan, and a 3.0L V12 in my other one.

[68_427]

40-43psi for me

[TurboDan]

15psi if you wanna drive on sand.

[S204STi]

If you want to get really technical about this you can get a tire pyrometer cand use that to determine correct tire pressure.

[Soup DeVille]

So about a week ago, I had a fresh set of tires installed on the Caddy. 255/35/20. The guy at the shop inflated them to 30 psi, which seems pretty low for a low-profile 20" tire, considering the original weaksauce 16" wheels from the factory had tires inflated to 27 psi. I'm concerned this time around because that same shop that installed my tires said that one of my old tires were damaged from driving on low air pressure.

Anyone know off the bat what the proper air pressure should be for a 255/35/20 tire? I kept the old tires at 40 psi, but I just found out that too much air pressure can damage the rim during the event of a pothole impact, which is exactly what brings me to where I am now. Halp!

pressure that's slightly too high is less likely to damage the rim than pressure that's slightly too low.

[Soup DeVille]

Not convinient when the car is avbailable with like 10 different engines, as many European cars are.

No, its much better to fill that manual up with vital information like "how to open the glovebox."

[AltinD]

No, its much better to fill that manual up with vital information like "how to open the glovebox."

So what if you have a dosens different rims that can be equipped with dozens types of tires? What's wrong with a sticker on the actual vehicle?

[MX793]

I think the reason they specify the oil and tire inflation specs on a sticker and not in the manual is because they don't want to have to print a different manual for every configuration.

Pretty sure both of my manuals are all written for all configurations of the vehicles.  They have tables with oil and fuel requirements (and general specs) for different engines.

[Rupert]

You assume people know which engine their car has.

[AutobahnSHO]

You assume people know which engine their car has.

or how to read. or that there is even a manual.

[Eye of the Tiger]

or how to read. or that there is even a manual.

Manual? Is that the kind you have to shift? Yeah, it's a manual. It's right next to D.