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Tire pressure

Gadwall

By Gadwall
in Tires, Wheels & TPMS

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Gadwall Enthusiast

Gadwall

Posted
Posted

Guys, I have a 2011 Sierra SLE Z60 and put BF Goodrich Rugged Terrain T/A P275/55R20 tires on a while back. I picked up the truck used and was not real familiar with what the Z60 package represented. Best I can tell the Z60 pkg has 1" shorter stance, tighter suspension and a larger front anti-sway bar. It is real difficult to confirm the big difference from standard setup trucks. Anyway, The factory door tag calls for 30psi front and back on tire pressure. I went 35 front and 38 rear. It rode pretty stiff and a friend suggested to bring down to the factory 30psi. I did lower it to 32F/34R and it seemed to ride a lil better. I am just afraid I will wear out the new tires prematurely as when looking at the tires on profile they look "low" on air. I do not want to have rounded edge on my $1000 tire investment. Any suggestion on what I should run them at or confirmation on Z60 pkg difference? Thanks.

vkjohnson Enthusiast

vkjohnson

Posted
Posted

I have the z60 with similar tires and run at 30psi as suggested. They put the suggested PSI on there for a reason...because that is where you get best performance and tread life. I'm sure others will say the same. Too much pressure will wear out the middles faster than the edges. I can only assume that the reason the 20 inch wheel package asks for 30psi vs the 35psi in others is because of the wider tread and more contact with the ground.

My brother-in-law has the z71 and IMO it is not as smooth as the z60. Z60 is paired with the 20 inch wheels and advertised for better road performance and that's where I'm driving 98% of the time. I wanted it because I saw the other posts about higher body roll and bounce on bad roads with z71 (plus I like the 20s). And yes, it does sit about 1" lower.

Wires Enthusiast

Wires

Posted
Posted

I have the z60, and have run 30PSI for the last 30k miles. Tires are wearing evenly.

 

I believe the Z71 comes with LT tires (my '00 did). They have a lot more plys and run 50 PSI if I remember correctly.

Cowpie Senior Enthusiast

Cowpie

Posted
Posted

Really too bad that the tire makers do not have easy to use tire load / air pressure charts like they do with commercial truck tires. There really is no one size fits all air pressure solution for everyone. Each of us has differing conditions we drive under, differing loads, etc. It is one thing to have a generic tire pressure for just running around, but varying load demands can make those generic pressures not the best choice for tire performance. And just guessing is not a good option.

mdauwald Enthusiast

mdauwald

Posted
Posted

I have the Z60 setup on my 08 with the 20 inch wheels and run 38psi. My front tires started to show some wear on the outer edges at 5000 miles while running 30psi. However, I also found that the factory alighment was off quite a bit. I was running 38psi only when towing but have since kept it that way full time. My tires have no additional wear 20K miles later.

 

Is part of a new vehicle delivery inspection checking the alignment? probably not but the dealer mentioned all GMT900s seem to be off from the factory

c4cruiser Enthusiast

c4cruiser

Posted
Posted

I have the Z60 setup on my 08 with the 20 inch wheels and run 38psi. My front tires started to show some wear on the outer edges at 5000 miles while running 30psi. However, I also found that the factory alighment was off quite a bit. I was running 38psi only when towing but have since kept it that way full time. My tires have no additional wear 20K miles later.

 

Is part of a new vehicle delivery inspection checking the alignment? probably not but the dealer mentioned all GMT900s seem to be off from the factory

Dealerships don't typically check alignments as part of their PDI process. If a new vehicle customer has a complaint about the alignment, they are usually told to put a few hundred miles on the vehicle before the dealer does any alignment work. That's supposed to allow for any sort of "wear-in" on the components. When I bought a '99 Silverado, I had an alignment issue and was told to drive it for awhile. After 1000 miles I took it back and the dealer replaced a tie rod end and did an alignment under the warranty.

 

My '08 Silverado Z71 has no issues at all with alignment. Now with 45K on it, it still doesn't have any issues. Tires are wearing evenly and it tracks fine.

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

alignments are not done at PDI ,,,my front end guy told me once that factory alignments are at a minimum so it goes down the road straight and doesnt wear to much

 

is it worth a trip to a front end shop for an alignment after purchase ?......for the price of tires ,,,yes imo

 

my 2 cents

Cowpie Senior Enthusiast

Cowpie

Posted
Posted

I have made it a policy that every new vehicle, be it pickup, car, or semi truck, goes from the dealer to my favorite tire shop for alignment. It is rare to find one that is set perfect from the factory. And I have all axles aligned, not just the steer axle. Obviously this is not a true comparison, but keeping things aligned, and running proper tire pressures that are checked daily, I am getting up to 200,000 miles out of a set of steer tires on my semi and well over 400,000 miles out of a set of drive tires. If having alignments checked can deliver that on my big truck, it ought to more than pay for itself on my pickup. And tires are not the only benefit. A well aligned vehicle will usually experience longer suspension component life as well.

MikeNH Senior Enthusiast

MikeNH

Posted
Posted

Of you're paying for more than a two wheel (front) alignment on a pickup you're wasting money. You can't set anything on the rear axle.

Cowpie Senior Enthusiast

Cowpie

Posted
Posted

Really? Just as the steers need aligned with each other, the axles themselves need to be aligned with each other. I get two axle alignments on my two axle vehicles, and I get 3 axles alignments on my semi trucks. U bolts are loosened and minor adjustments made to get rear axle to run true with front axle. This is pretty basic stuff we are talking here. Just that most folks do not think to do it.

MikeNH Senior Enthusiast

MikeNH

Posted
Posted

Really? Just as the steers need aligned with each other, the axles themselves need to be aligned with each other. I get two axle alignments on my two axle vehicles, and I get 3 axles alignments on my semi trucks. U bolts are loosened and minor adjustments made to get rear axle to run true with front axle. This is pretty basic stuff we are talking here. Just that most folks do not think to do it.

 

I'm not talking commercial trucks, I'm talking trucks like we all have here and in three years of automotive-related classes between high school and tech school, another three working at a dealership and countless friends still in the business, I've never heard of anyone doing an "alignment" on a leaf-sprung solid axle pickup. A light duty pickup isn't a semi.

Cowpie Senior Enthusiast

Cowpie

Posted
Posted

Contact my alignment guy, Todd, at Allied Oil and Tire in Des Moines, IA. He also teaches all this stuff at the local tech school.

nickvrebel Senior Enthusiast

nickvrebel

Posted
Posted
Contact my alignment guy, Todd, at Allied Oil and Tire in Des Moines, IA. He also teaches all this stuff at the local tech school.
and if he charges for anything more than a 2 wheel alignment on a pickup he is screwing you.

 

As for alignments on brand new vehicles: alignments can show "off" after a trip around the block. The dealer will perform the alignment under warranty, as stated previously they prefer you to put a couple hundred miles on first. Paying fir it somewhere else when your dealer is perfectly qualified is ridiculous.

 

Cowpie Senior Enthusiast

Cowpie

Posted
Posted

Ok, maybe we got lost in semantics with all of this. The rear thrust axis alignment check is what I was talking about as being a 4 wheel alignment. I realize that most folks have not even considered that as a possibility or even needed, but a quick search thru the web pages will provide some insights into this. Try 4 wheeler magazine for one as a start point. If the rear axle is not aligned properly to the thrust axis of the vehicle, then it can affect the steer axle alignment also. That is why the rear is checked first, and adjusted if needed, then the front is aligned. That may not be called a 4 wheel alignment in some circles, but it is in others. And this is why I always have a "4 wheel alignment" done on any new vehicle. Now, to be fair, there are many shops that are not set up to do this rear axle check. That is why I go to a very good shop that caters to commercial vehicles and fleets. I take my semi's there. I take my pickups there.

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