Tire size, wheel Size & Regearing

[Amanda C]

I am now looking to start my overland rig build and have an upcoming road trip from Toronto to Seattle in January 2020. The present tire is not 3 peaks (snow rated) and I think it would be prudent to change them in preparation for meeting cold weather as i travel west.



I would like to increase the tire size to enjoy more ground clearance when on trails and would like to put on BF Goodrich Ko2 AT tires.

The tire technician I spoke with at a trusted tire shop (he inspected my truck and confirmed I can put on a 285/75/16 on my existing 16” rims, however I will need to make some modification to the front wheel fender and bumper area (NorCal mod) to stop rubbing and he says I can adjust the front torsion bars to give me more clearance for the tires, However I will be upgrading the suspension system once I have decided what to install and before going on any trails.

However this is my dilemma:-

He is advising that I should stick with the factory 16” wheel/rim as this will give more rubber on the trail when airing down, than installing a 17” or above rim, can anyone give me their thoughts on this ?

Also Regearing I know that changing the tire can have an effect on performance and add undue wear and tear on the transmission?

The round trip I am doing is 9186 km and I know MPG will suffer what is peoples thoughts on this?

My alternative is to purchase a cheaper AT tyre/winter tire to do the trip and then wait until I find a trusted mechanic and fabrication shop to help me build the ideal overland rig?

I think that about sums up whats on my Mind, its quite overwhelming at times, especially when new to owning a truck and overlanding.

I look forward to hearing community thoughts :-)

Thanks

Amanda

 

[Bama_Kiwi]

The technician is correct in their statement about sticking with 16" wheels. Also, R16 tires are generally more readily available and more affordable.

Larger/heavier than stock tires will have an impact on performance, but, I would be hesitant to invest in re-gearing for just a one or two-sized tire increase.

More critically, I would ensure your speedometer is correctly calibrated for the increase in tire size.

 

[Amanda C]

Dear Bama_Kiwi,

Thanks for being so quick to reply, I appreciate the time to advise, so pleased to be a member of OB and looking forward to Helping others too!

I had a good feeling about the person and the advice he was giving I just want to be careful as its a large purchase and I have quite a lot of Kms to cover and dont want to pit stress on the transmission or engine!

Yeah I knew the speedometer will need to be calibrated and will be looking for a mechanic to do this, thanks for pointing this out for other members reading this or considering changing tyre size.

I see your from Alabama, did you own a truck in the USA Before the Mitsubushi Pajero ( i checked out your vehicle on google, i can imagine its very capable with the modifications you have made?

Thanks again

Amanda

 

[Billiebob]

My alternative is to purchase a cheaper winter tire to do the trip and then wait until I find a trusted mechanic and fabrication shop to help me build the ideal overland rig?

I would do this. Going bigger for a 10K mile highway trip makes no sense they will definitely hurt your gas mileage. And a winter trip will be far more comfortable with winter tires. Sure the KO2s are a good all around tire but dedicated winter tires will blow them away. I know, I've had both and went from KO2s to winter grips one January. The difference was night and day.

Enjoy Seattle. You'll love the trip. A full size pickup on winter tires is maybe the best winter travel vehicle for a long distance trip. Only to be beat by the AWD system in a Subaru Outback.

 

[Dilldog]

I wouldnt worry about a regear at all. Depending on options your pickup will have anything from 3.08 to 3.73 gears. Even with the 3.08 gears I wouldnt hesitate to run a 33" tire, provided you have a V8 and not the 4.3L V6. The biggest thing to remember is to just leave the transmission in 3rd or D until you get onto the highway, then put it in 4th or OD, this will keep the transmission from trying to shift into overdrive at lower speeds and reduce the amount of shifting it does, shifting in and out of overdrive generates heat and heat is the second biggest cause of premature transmission failure (first is lack of service).
As far as the tires, I try to stick with the smallest wheel I can. Some of my previous builds I even ground down brake calipers on 1ton pickups to get a 15" wheel to clear. Also the BFG A/T will be a snow rated tire (has the 3 peaks and snow flake logo). But dedicated snow tires will be better. Also most speedometers are up to 10% slow, so a re calibration may not be needed.

 

[Amanda C]

Dear Billie Bob,

Thanks for the advice and it I guess it would take the pressure off me now and most of my serious overlanding will be from May 2020 when I head south to New Mexico via Virginia, Missouri and Texas. Any suggestions as to make of winter tyre i should look at?

I cant wait also to check out BC one day!

Best wishes

Amanda

 

[Billiebob]

Dear Billie Bob,

Thanks for the advice and it I guess it would take the pressure off me now and most of my serious overlanding will be from May 2020 when I head south to New Mexico via Virginia, Missouri and Texas. Any suggestions as to make of winter tyre i should look at?

I cant wait also to check out BC one day!

Best wishes

Amanda

Any brand name winter grip. They are all excellent. Get the stock size, look for the best price. I always say buy from a local tire shop. Kal Tire, Fountain Tire..... which ever is most convenient. My Kal Tire store does the spring and fall change overs for free since I buy all my tires from them.

You should travel thru BC on the way to or home from Seattle.
Google
Raduim Hot Springs
Fairmont Hot Springs
Ainsworth Hot Springs
Nakusp Hot Springs
No place better to be on a snowy winter night.

Halcyon Hot Springs below.

 

[Amanda C]

I wouldnt worry about a regear at all. Depending on options your pickup will have anything from 3.08 to 3.73 gears. Even with the 3.08 gears I wouldnt hesitate to run a 33" tire, provided you have a V8 and not the 4.3L V6. The biggest thing to remember is to just leave the transmission in 3rd or D until you get onto the highway, then put it in 4th or OD, this will keep the transmission from trying to shift into overdrive at lower speeds and reduce the amount of shifting it does, shifting in and out of overdrive generates heat and heat is the second biggest cause of premature transmission failure (first is lack of service).
As far as the tires, I try to stick with the smallest wheel I can. Some of my previous builds I even ground down brake calipers on 1ton pickups to get a 15" wheel to clear. Also the BFG A/T will be a snow rated tire (has the 3 peaks and snow flake logo). But dedicated snow tires will be better.

Dear Dilldog,

Thanks for the reply and advice, I have an V8 and automatic. so maybe for now its a snow tyre and then next summer I change wheel size and suspension, thanks for advice on the speedometer i bear that in mind. So 16” rims/wheels are a good thing? More rubber on the trail? Not sure my truck has OD what is this?

Thanks for the advice, cant wait to visit your state :-) the camper i am picking up for my rig is in Port Townsend!

Best wishes

Amanda

 

[Amanda C]

Any brand name winter grip. They are all excellent. Get the stock size, look for the best price. I always say buy from a local tire shop. Kal Tire, Fountain Tire..... which ever is most convenient. My Kal Tire store does the spring and fall change overs for free since I buy all my tires from them.

Thanks I will be checking out KAL tyres, i know they store tyres as well! My dad used to use them!

 

[Dilldog]

Dear Dilldog,

Thanks for the reply and advice, I have an V8 and automatic. so maybe for now its a snow tyre and then next summer I change wheel size and suspension, thanks for advice on the speedometer i bear that in mind. So 16” rims/wheels are a good thing? More rubber on the trail? Not sure my truck has OD what is this?

Thanks for the advice, cant wait to visit your state :-) the camper i am picking up for my rig is in Port Townsend!

Best wishes

Amanda

So OD is over drive, which is 4th gear. I think on your vintage of GM its just D. Your shift read out should go something like P,R,N,D,3,2,1. I always ran my GM autos in 3 until I got to a sustained highway speed then kick it into D. It just keeps it from shifting between the top two gears a bunch which is important when you run bigger tires or are under a load. Also another thing to remember, with your transmission if you are in very slick conditions manually select 2. This will cause the truck to start in 2nd gear rather than 1st, reducing the chances of wheel spin.
Also yes I think running the smallest possible wheel is a good thing for off road use. Honestly on your rig I might even be tempted to run a 15", but im not sure if a 15" wheel clear your front brakes or not, so yeah just stick with the 16s.
Port Townsend is a great place, my uncle has house overlooking the ocean there. The Peninsula is like a whole different world compared to the rest of WA state.

 

[Billiebob]

the camper i am picking up for my rig is in Port Townsend!

is this the reason for the trip?
Port Townsend is a wonderful little city.
Be sure to see the harbour. Port Townsend was an entry port for foreigners and the history is quite colourful. Been a long time since I was there but we stayed in the quarantine quarters 20 plus years ago.

 

[Amanda C]

So OD is over drive, which is 4th gear. I think on your vintage of GM its just D. Your shift read out should go something like P,N,R,1,2,3,D. I always ran my GM autos in 3 until I got to a sustained highway speed then kick it into D. It just keeps it from shifting between the top two gears a bunch which is important when you run bigger tires or are under a load. Also another thing to remember, with your transmission if you are in very slick conditions manually select 2. This will cause the truck to start in 2nd gear rather than 1st, reducing the chances of wheel spin.
Also yes I think running the running smallest possible wheel is a good thing. Honestly on your rig I might even be tempted to run a 15", but im not sure if a 15" wheel clear your front brakes or not, so yeah just stick with the 16s.
Port Townsend is a great place, my uncle has house overlooking the ocean there. The Peninsula is like a whole different world compared to the rest of WA state.

Dear Dilldog,

Thanks for this advice, so what’s the best gear for around town where the speed limit is 50 to 60 mph, occasionally 80 mph. I have always been using D, thanks for advice on slick conditions i will bear in mind 2 and 3 for this winter in Oshawa. I am looking forward to the trip, a little nervous, i flew into my dads on Tuesday and i am adjusting to canada life again. discovering Overlanding is like being a big Kid again !

 

[Amanda C]

is this the reason for the trip?
Port Townsend is a wonderful little city.
Be sure to see the harbour. Port Townsend was an entry port for foreigners and the history is quite colourful. Been a long time since I was there but we stayed in the quarantine quarters 20 plus years ago.

Hi Billiebob,

Yeah I am going to pick up my HOBBIT HOUSE, thanks for the hot springs cant wait! and Port Townsend, you can see more of my build as it happens by clicking the link in my signature below.

Best wishes

Amanda

 

[Dilldog]

Dear Dilldog,

Thanks for this advice, so what’s the best gear for around town where the speed limit is 50 to 60 mph, occasionally 80 mph. I have always been using D, thanks for advice on slick conditions i will bear in mind 2 and 3 for this winter in Oshawa. I am looking forward to the trip, a little nervous, i flew into my dads on Tuesday and i am adjusting to canada life again. discovering Overlanding is like being a big Kid again !

Around town here the speeds are anywhere from 25 to 45mph, so I would leave it in 3. Once I hit the state highways or interstate and got above 55mph I would select D. Also when you pull long steep hills its a good idea to select 3. And dont worry about damaging the transmission by selecting gears while moving, they are designed to be able to do that, just dont overshoot and hit reverse. Your pickup is new enough that it wont actually go into reverse but it will do some wacky stuff.

 

[Amanda C]

Around town here the speeds are anywhere from 25 to 45mph, so I would leave it in 3. Once I hit the state highways or interstate and got above 55mph I would select D. Also when you pull long steep hills its a good idea to select 3. And dont worry about damaging the transmission by selecting gears while moving, they are designed to be able to do that, just dont overshoot and hit reverse. Your pickup is new enough that it wont actually go into reverse but it will do some wacky stuff.

Thanks I start learning this, I was used to manual gears all my driving life, this is my first automatic !

 

[Dilldog]

Thanks I start learning this, I was used to manual gears all my driving life, this is my first automatic !

Most automatics can be used in a half ways manual way. When Im towing I will still use gears to help slow me down too. An automatic wont slow you down as much as a manual but it will help some.

 

[Bama_Kiwi]

Dear Bama_Kiwi,

Thanks for being so quick to reply, I appreciate the time to advise, so pleased to be a member of OB and looking forward to Helping others too!

I had a good feeling about the person and the advice he was giving I just want to be careful as its a large purchase and I have quite a lot of Kms to cover and dont want to pit stress on the transmission or engine!

Yeah I knew the speedometer will need to be calibrated and will be looking for a mechanic to do this, thanks for pointing this out for other members reading this or considering changing tyre size.

I see your from Alabama, did you own a truck in the USA Before the Mitsubushi Pajero ( i checked out your vehicle on google, i can imagine its very capable with the modifications you have made?

Thanks again

Amanda

Amanda,

You're welcome! Never be afraid to ask questions - everyone here is eager to help.

I have owned several 4WD vehicles in the states, starting with a 1991 Geo Tracker (nee Suzuki Sidekick), then a 1999 Mitsubishi Montero Sport, and most recently a 2007 Chevrolet Trailblazer. I kept each of these trucks mostly stock, aside from tires, due to either lack of funds or lack of need/desire.

My current car has received the most modification as I have delved deeper into this hobby/lifestyle. More mods planned, too. :) I haven't had much opportunity to test its capability first-hand as yet, but no reason to believe I can't do most of the things I'd ever want to do, so far.

 

[Lanlubber In Remembrance]

I am now looking to start my overland rig build and have an upcoming road trip from Toronto to Seattle in January 2020. The present tire is not 3 peaks (snow rated) and I think it would be prudent to change them in preparation for meeting cold weather as i travel west.

View attachment 131185

I would like to increase the tire size to enjoy more ground clearance when on trails and would like to put on BF Goodrich Ko2 AT tires.

The tire technician I spoke with at a trusted tire shop (he inspected my truck and confirmed I can put on a 285/75/16 on my existing 16” rims, however I will need to make some modification to the front wheel fender and bumper area (NorCal mod) to stop rubbing and he says I can adjust the front torsion bars to give me more clearance for the tires, However I will be upgrading the suspension system once I have decided what to install and before going on any trails.

However this is my dilemma:-

He is advising that I should stick with the factory 16” wheel/rim as this will give more rubber on the trail when airing down, than installing a 17” or above rim, can anyone give me their thoughts on this ?

Also Regearing I know that changing the tire can have an effect on performance and add undue wear and tear on the transmission?

The round trip I am doing is 9186 km and I know MPG will suffer what is peoples thoughts on this?

My alternative is to purchase a cheaper AT tyre/winter tire to do the trip and then wait until I find a trusted mechanic and fabrication shop to help me build the ideal overland rig?

I think that about sums up whats on my Mind, its quite overwhelming at times, especially when new to owning a truck and overlanding.

I look forward to hearing community thoughts :-)
Thanks
Amanda

Amanda, I will try to give you my opinion but it may not be what you want to hear.
First, stick with the 16" wheels, you tire man is right about the cushion is better on 16" tires than the larger tires.
Second, your wanting to go up in size 4 tire sizes from 245 to 285. Keep in mind that a 4" taller tire will only raise your rig 2". I don't know the diameter of your 245 tire or the 285 tire but generally each size larger is about 1" taller than the lower number. 4" is a good guess for now. Your gear for the speedometer will have to be changed in the tranny to correct your MPH. At 65 MPH your engine RPM will drop several hundred RPM's, which means your factory cruising speed will change. (factory cruising speeds for MPG of gas is usually around 2200 to 2400 RPM on the tachometer.)
It would be a good idea to go out and check your driving speed with your tach so you will know before you change things what your engine performance is today.

The effect would be that your acceleration will not be as good as it was with 245 tires. To get the acceleration back to what it is now a lower gear ratio would need to be installed to compensate. If you buy the tires now I would also change the gears as well or you wont be happy with the performance. I know you wouldn't be happy with a smaller tire from the looks point of view so I wont even suggest doing that to avoid a gear change. Make the torsion bar height change if the man said it can be done. Don't forget, 4x4's can get stuck too, even with aggressive tires so don't go anywhere in snow country without tire chains. You didn't mention a locker differential but as long as you need a gear change I would put a locked in the rear at a minimum if it doesn't have one already. A posi-track is okay if you don't push it to hard and may be all you need. All of what I suggest will be needed when you add the extra weight of that camper. Even after the gear change you will notice a big difference in truck performance with what looks like a heavy camper. You truck is heavy half ton 327 ci v8 engine (5.3L) and to get all the performance you need you may want you visit a performance shop to see if they can get you another 100 horse power for off roading. That could wait until you get the camper installed on your rig.

The only other advise I can offer is to just go ahead and get a set of tire chains and head out. The truck is pretty capable as it is. The interstates are kept cleared for traffic and as long as your not going off road right now your tires will be okay for the trip to Washington. You will want all that I mention when you put that camper on so do it now or do it later.

 

[UltimaSanctus]

Always glad to see another GMT800 rig on here.
So if your truck has the holy grail of options with the 5.3L V8, Z71 package (which i see it does), and the towing package, it should have 4.10 gears from the factory. This means that the engine will still work in it's powerband all the way up to 35" tires. Granted you would need a 6" suspension lift or a 2" suspension + 3" body lift to fit those.

If it doesn't actually have the 4.10s it will have 3.73s which is fine for the 285/75/r16

In order to fit the 285/75/r16 tires, which is roughly 33", all you need is some leveling torsion keys which can be found for about $40-60

You could also get some small rear lift blocks so the truck isn't squatting with a trailer attached.

For the around town shifting that others have talked about, if you are worried about being in too high of a gear you could just hit the tow/haul button on the end of the shift stalk

Also towing can eat up the 4L60e transmissions sadly. I would recommend getting an upgrade transmission cooler and you should have no worries.

Hope all this helps

 

[Lanlubber In Remembrance]

Around town here the speeds are anywhere from 25 to 45mph, so I would leave it in 3. Once I hit the state highways or interstate and got above 55mph I would select D. Also when you pull long steep hills its a good idea to select 3. And dont worry about damaging the transmission by selecting gears while moving, they are designed to be able to do that, just dont overshoot and hit reverse. Your pickup is new enough that it wont actually go into reverse but it will do some wacky stuff.

The auto trans will downshift automatically when going up hill. Very seldom have I manually down shifted with an automatic going up hill, but I do down shift going down hill as a breaking method. Your trucks computer shifts the auto trans as needed. If your truck has an OD, it dosent go into OD until you are 40-45 miles per hr. Always drive in D unless you are pulling a load and need 3 to keep your rpm's up so the engine does not lug (strain). That should not be necessary with an auto if your tranny is in proper working order.