School me on truck tires

[fiddypal]

Ok so i admit it, i know next to nothing about tires.... Can you guys school me on all the important info regarding my situation?

I have a Silverado 1500 with upgraded tires (BF Goodrich All-Terrain T/A | LT305/65R18 | 124/121R), i know this because i bought the truck used and all my friends kept asking me when i got new tires and i told them they came on the truck

The spare (Goodyear Wrangler HP P265/70R17 | 113S) is also not the same tire as the 4 on the truck, looks like a normal road tire which i am guessing matches the stock tires that came with the truck from the factory.

The TPMS in my truck is happy when the front are around ~42psi and the rears at ~45psi. It is very sensitive and can go off in the winter if the tires get cold and lose a few psi.

My driving style is 80% Paved roads and 20% Dirt roads and trails. My off roading currently consists of dirt roads in the local state park which are in very good condition, no potholes or anything, etc. These tires are pretty good on the highway too since they don't give off a ton of road noise. I have driven friends trucks with nobby aggressive tires and was like ****** is that noise when i first got on the highway so trying to avoid that since most of my driving is on paved roads.


So i guess a few questions:

- What are my current tires capable of off-road? This is a new truck so i'm not trying to push the limits and do anything crazy off road.
- Can someone give me a quick overview of "airing down"... What psi do i want to drop to for off road and why? So far i have never aired down but i dont know if i am lucky and have not had a puncture or if i just havent needed to in the off road driving i have done so far.
- I read in another thread that driving with a non-matching spare can screw up your drivetrain. Is this true, should i get a matching spare or is the one i have in there now fine in a pinch?

 

[jeep-N-montero]

Every question you just asked has been covered numerous times on here and many other forums, please take the time to do a bit of searching and reading and you will learn a lot.

 

[fiddypal]

Every question you just asked has been covered numerous times on here and many other forums, please take the time to do a bit of searching and reading and you will learn a lot.

Right, can't believe i missed all the other threads with people who have the same exact tires and driving habits as me..... Its a forum for conversation man, if you told everyone to search the forums for past content at some point there would be no reason to post anymore since everything has been answered!

Just trying to have a conversation with like minded people and learn a little in the process.

 

[Airmapper]

Just trying to have a conversation with like minded people and learn a little in the process.

Nevermind jeep-N-montero, he gets a little uptight sometimes. And some people confuse forums with Wikipedia...... Wikis are for static information posting. Forums are for dynamic discussion.

- What are my current tires capable of off-road? This is a new truck so i'm not trying to push the limits and do anything crazy off road.
- Can someone give me a quick overview of "airing down"... What psi do i want to drop to for off road and why? So far i have never aired down but i dont know if i am lucky and have not had a puncture or if i just havent needed to in the off road driving i have done so far.
- I read in another thread that driving with a non-matching spare can screw up your drivetrain. Is this true, should i get a matching spare or is the one i have in there now fine in a pinch?

You have "AT" tires, mildly capable off road, more so than typical street tires. The tires you have are highly regarded for mixed surfaces and very popular for your use, you should be fine.

Airing down makes the tire more flexible, and thus conforms to the surface better, aiding traction. Airing down too much can damage the tire or cause it to come off the bead. I usually never air down below 20psi. People vary on what pressure they think is ideal. For your intended purposes I would not find it necessary to air down. Some people on this forum advocate it in excess, if you are not having traction issues, I'd leave the air in the tires until you do. Personally I find it kinda annoying when folks have to stop and fiddle with their tire pressures like a restless person with a sleep number bed.

One additional point is less air in tires aides thier puncture resistance, this is usually only an issue in serious off roading in rocks or sharp sticks, which it does not sound like you are planning on yet.

The critical thing for a spare is that it be the same SIZE as your other tires. Other factors like tread or brand are negligible. Personally I have an identical matching spare down to having an identical wheel, this is because I'm vain and don't want to look like a 3-legged dog driving around with an odd spare should I use it.

Hope this helps.

 

[Airmapper]

Looking over your spare again, you need a 305/65R18 or a tire with equivalent diameter. There are tire calculators online you may be able to find a matching diameter 17 inch tire and slap a used tire on your spare rim for the time being.

Driving with that spare will be hard on your differential, which is designed to account for minor differences in wheel speed, not major ones like you would see with different diameter tires.

 

[jeep-N-montero]

You could switch to a 17in wheel and run the ko2 in the 34x10.50r17 size load range D, very good setup to run for year round traction. And make sure you get 5 matching wheels/tires, I have never understood why people spend money on wheels but are too cheap to get a matching spare.

 

[jeep-N-montero]

And tire size calculator here https://tiresize.com/calculator/

 

[jeep-N-montero]

Airing down tires https://www.google.com/?gws_rd=ssl#q=airing+down+tires

 

[fiddypal]

Thank you for all the great info guys, that is exactly what i was looking for. Right now i keep a puncture kit and small cig outlet air compressor in the truck for emergencies. Will the rim the spare is currently on match the same tires i have on the truck now or would i have to go buy a bigger spare rim?

I am guessing the R17 and R18 mean 17 and 18 inches respectively?

These tires have treated me well so far, so i may very well get an extra to replace the spare with so they all match. I am glad i confirmed what i had read about the differential getting impacted by running different tire sizes, never knew that!

The big adventure i am about to embark on will see me in Mt.Rushmore, Yellowstone/Teton, Utah, Colorado. Again not looking to do any rock crawling, just casual trails to find places to camp or go fishing, etc.

 

[Doctor W]

Probably best to get a 18 inch wheel from a wreckers for your exact model and year Chevy, maybe get a cheap used tire on one of those 18 inch wheels while you're there. I wouldn't drive very far at all with such greatly different sized tires on one inch different wheels for fear of damage to a diff or transfer case.

 

[RedF]

Your BFG A/Ts are a great tire for street driving and recreational off roading.

R means radial, the 17 or 18 is the rim diameter in inches - so no, your 17" spare wheel will not be compatible with the tire size your truck is running.

Personally, I wouldn't get in a twist to buy a matching spare wheel and tire. Many vehicles come equipped with with a smaller spare from the factory, not that your Silverado necessarily did. If you do have to use the smaller spare, try and limit your speed and distance.

The calculated difference in diameter is 2", and the difference is 38 revolutions in a mile. If your truck has a gov-lock diff, it apparently requires approximately 100 rpm difference to engage, so unless you are going 150+ miles/hour with your spare tire installed, it shouldn't care. Beyond that, they're supposed to disengage at relatively low speed anyway.

That said, yes it is ideal to have a matching spare for several reasons, but it's also ideal to have the spare tire fit in the factory location. A 33.6" diameter tire may not fit in the factory location.

 

[Regcabguy]

Right, can't believe i missed all the other threads with people who have the same exact tires and driving habits as me..... Its a forum for conversation man, if you told everyone to search the forums for past content at some point there would be no reason to post anymore since everything has been answered!

Just trying to have a conversation with like minded people and learn a little in the process.

An LT from any brand will work fine. I don't understand how all the truck companies get away with outfitting light trucks with passenger car tires.

 

[dman93]

Your BFG A/Ts are a great tire for street driving and recreational off roading.

R means radial, the 17 or 18 is the rim diameter in inches - so no, your 17" spare wheel will not be compatible with the tire size your truck is running.

Personally, I wouldn't get in a twist to buy a matching spare wheel and tire. Many vehicles come equipped with with a smaller spare from the factory, not that your Silverado necessarily did. If you do have to use the smaller spare, try and limit your speed and distance.

The calculated difference in diameter is 2", and the difference is 38 revolutions in a mile. If your truck has a gov-lock diff, it apparently requires approximately 100 rpm difference to engage, so unless you are going 150+ miles/hour with your spare tire installed, it shouldn't care. Beyond that, they're supposed to disengage at relatively low speed anyway.

That said, yes it is ideal to have a matching spare for several reasons, but it's also ideal to have the spare tire fit in the factory location. A 33.6" diameter tire may not fit in the factory location.

This is an interesting observation (I didn't check your math but assume it's correct). I worry about even slight tire pressure differences from side to side affecting tire diameter and diff behavior, but in reality it seems like slight curves, road camber, bumps etc will have just as much effect, especially with an open diff. It's probably still good to have a spare that closely matches diameter and width especially if you need to put it in front (for steering stability etc) or if you regularly rotate the spare into service, but the importance may be overblown. For example, it may not really be beneficial to relocate a heavy spare to hang off the back bumper just to fit a matching size, as so many people do. Thanks for a thoughtful response.