Jeep Wrangler Forum banner

1 - 20 of 36 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter #1 (Edited)
How far could I go in an emergency without damaging the diff riding a 32' and a 37' on the same axle? I'm long overdue for new tires so I pulled the trigger on upgrading from 32's to 37's on my 2013 JK rubicon 2 door manual. My spare tire mount wont hold a 37' so I just bought 4 for now. Meaning if I get a flat I'd only have the 32' spare tire. Other option would be to buy the fifth tire but keep the spare behind the back seat while I save up for the mount and regear. Any temp hacks for the mount or otherwise? Money is kind of tight right now but I needed new tires and I might want to save up for more than a basic mount.
 

·
Registered
Joined
·
455 Posts
I can’t answer your question but you could carry a plug kit and an air compressor. If you don’t mind a little work you’ll be fine.
 

·
Premium Member
Joined
·
1,792 Posts
I think to get off a trail it would be ok on the rear.
If I had to drive home, I would but the 32 on the front to not risk damaging the rear diff even if it is for my peace of mind.
 

·
Registered
Joined
·
2,361 Posts
32 to a 37 is about 15% difference in conference and the spider gears would have to make up the difference. And then there is the computer braking system that would be going nuts. I believe if you unplug one of the wheel sensors, the ABS and electronic traction control will be disabled. Obviously driving with a 32 and a 37 up front is best to be kept to a minimum speed and distance.

I have read that about 10% of new cars don't even come with a spare and it is more common to have a dead battery than a flat.
 

·
Super Moderator
Joined
·
5,308 Posts
Unless you have a clutch based LSD like the Factory Track-Lok LSD I can't see how it would possibly damage the diff. But I could see it causing serious issues for the electronics, setting off the traction control and ABS systems and causing performance issues. A simple test would be to swap the smaller tire in and drive it to see how it works. I would try it on the rear axle as well as on the front axle.
But the reality is I would not do that. I would not have a spare that far off of the correct size. I would have a spare that is the correct size. If I were in your shoes I might take the spare off and carry something to patch a flat tire as well as inflate a flat tire. Then I would hope if I get a flat tire it is a fixable flat and not the type of flat like we just had a while back. There was no fixing that one. But, of course, we had a spare of matching size so we were fine.
The stock spare tire carrier isn't rated for that much weight. But you can buy a kit that upgrades it so it can carry the weight. They aren't that expensive, and easy to install. And out of all the additional expenses you are going to face running 37" tires upgrading the spare tire carrier is really small potatoes.

Oh, and welcome to the forum.
 

·
Registered
Joined
·
75 Posts
Im no tech, but i was explained by tech not to go too far off.
Jeeps are true mechanical 4wheels drive. There is a mechanical direct axle link with the wheels, thus require the tire/wheels to be the same (all 4).. there is a small play without damaging anything, but it is really not worth the risk. the spare wont match in circumference . That will cause one axle to turn at an unacceptably different RPM than it’s opposite. Its like a human body with 1 longer leg.. eventually that person with start developing bones and joint problems.

this is also true with all-wheel-drive, the user manual on subaru awheels warns people not to use smaller spare tire too.

For my willys, i was lucky to find four used 275-70-17 ko2 @ 12/32 (For $600) but no luck finding the fifth so i put a $30 14/32 duratrac AT 255-75-17 In the back until i get 5 falken...using tiresize compare web site, the RPM is very close between the 255-75-17 and the 275-70-17 (i will only use the duratrac to get to the garage for a repair..)

in other words , your 32" running with 37" is probably too much ..not worth the risk.

the flat repair kit is probably the cheapest route until you can afford the fifth.
 

·
Registered
Joined
·
1,468 Posts
If money is so tight that you can't get a spare, there are plenty of other issues you should worry about running 37s too.

What other upgrades do you have?
 
  • Like
Reactions: Leadnut

·
Grumpy Old Guy
Joined
·
3,009 Posts
In other words you are introducing a whole lot of problems by simply going with 37's. The problem is even bigger running a 32, even if temporarily.

Be patient, save your money and do it right. It will cost you a lot more later than if you are patient and do it right the first time.
 

·
Super Moderator
Joined
·
15,121 Posts
It can certainly be said more articulately than some... Buy yourself a plug kit, I have the ARB kit. It's not horribly expensive and make repairing your tire the first option. It doesn't always work, so have a back up plan. I have been able to plug more often than having to mount a spare. You do need an air compressor as well. I use the VIAIR 400P so it's portable... I fill tires around my house all the time with it.

Little story, I was up on the White Mountain Indian Reservation (beautiful place) and fishing on a little lake about 25 miles from anything... Me and one other vehicle had the lake to ourselves. We had been there for 3 days and 2 nights already... While fishing on the dam, the other guy comes strolling up and says... Hey there, wondering if you can help me out of a little dilemma. I've got 3 flat tires. o_O

So I packed up my fishing gear and headed back to the Jeep. I told him that I just might be able to help. One of the tires had a blown sidewall... The other 2 were tread punctures. Sweet, we got a chance. Sure enough, able to plug the 2 and air them up and send him in to town for some new tires. Both sidewalls had bubbles in them, but the plugs held. He had run about 50 miles on medium rocky forest roads with Goodyear highway tires on his Grand Cherokee.

We hadn't seen another person in days, if I hadn't been there, there's no telling how long he would have waited for assistance.


Here's a few pics of the location, just for attention.

4447614

4447615

4447616
 
  • Like
Reactions: USStrongman

·
Registered
Joined
·
654 Posts
In an emergency I’d bite the bullet and call the tow-truck
 

·
Super Moderator
Joined
·
5,308 Posts
In an emergency I’d bite the bullet and call the tow-truck
Perhaps, but where we like to go a tow truck can be incredibly expensive, if it is even an option.
But for street use a triple A membership might be a good thing.
One of our cars did not come with a spare tire. It came with a 12 volt air pump and a specially designed bottle of fix-a-flat that fit into the air pump and would inflate and patch the tire at the same time. Of course this depended on the flat being fixable in that manner. The one time we had a flat with that car the tire came apart and there wasn't enough fix-a-flat in the world to fix it. We had to wait hours for my brother to pick up a wheel / tire at our house and bring it to us. It was not a good day.
For me, I can't imagine driving a Jeep without a proper spare tire. But to be fair, many people do. Some even permanently remove the spare tire and its mount off the rear tailgate. To each their own.
 

·
Super Moderator
Joined
·
10,631 Posts
Here's another idea. Go to a salvage yard and buy a decent used 37"tire. Have it mounted on the same wheel as your other 4 tires. Then, clean it well and carry it in the cargo area.
I don't run a spare for daily driving but I carry a can of Fix-A-Flat in my console and I have AAA. If I go off road, I carry my spare in the cargo area. I have a compressor and a plug kit in my off road tool/recovery box.

Good Luck, L.M.
 

·
Registered
Joined
·
654 Posts
Here's another idea. Go to a salvage yard and buy a decent used 37"tire. Have it mounted on the same wheel as your other 4 tires. Then, clean it well and carry it in the cargo area.
I don't run a spare for daily driving but I carry a can of Fix-A-Flat in my console and I have AAA. If I go off road, I carry my spare in the cargo area. I have a compressor and a plug kit in my off road tool/recovery box.

Good Luck, L.M.

If you go this route, make sure you ratchet strap it down. Wouldn’t be fun to have a 31” or larger tire fall on your head
 

·
Registered
Joined
·
8 Posts
Discussion Starter #15 (Edited)
If money is so tight that you can't get a spare, there are plenty of other issues you should worry about running 37s too.

What other upgrades do you have?
I have:
6 inch Teraflex suspension lift
3 inch body lift.
Rubicon Extreme Duty Mono Tube Shocks
RE CVF rear Driveshaft.
Rancho steering stabilizer
Half of a PSC Hdyro assist system. (pump, pulley, resevoir)
Half inch wheel spacers.

I will finish the hydro assist once I buy the rest of the parts. I blew the power steering pump so I just bought half the upgraded system for now. Next up is probably brakes or re gearing depending on how it feels but will do both soon. Will probably do gussets but not convinced yet on other axle upgrades/reinforcements. Have yet to scour all the threads on this yet. It's a manual trans

Teraflex f/r diff armor
Smittybuilt f/r bumpers/sliders
Banks ram air
Magnaflux exhaust.
Rugged ridge LEDs.
Firestik antennae.
Noco external adapter running to Schumacher battery charger.
Glock box.
No winch yet but will do that plus oil pan/tranny armor.

By money being tight I mean I may have to wait a month to continue the build. Priorities are regearing, brakes and finishing the hydro assist. I cant keep running and balding tires all month.

I'm just gonna spring for the fifth tire and keep it in the back. Still interested in the 37' discussion re needed upgrades. My wheeling habits are pretty rough but I could learn to be more cautious. Seems that's the consensus reached in all the 37's threads. That it's at least as much or more about habits as about equipment
 

·
Registered
Joined
·
756 Posts
My math says a 32" and 37" tire will spin at the same differential rate of driving in about a 80 foot diameter circle. Not sure how nice that'll be to the diff if you're cruising down the freeway at 80 mph, you would never take a turn that tight, that fast (in a Jeep anyway), and certainly not continuously.

I like other suggestions of trying to get yourself a used 37" tire for cheap, just enough to get you out to the tire shop. Although you don't want something totally bald that will be at a very high risk of failing itself while getting you off the trail.

I wouldn't rely entirely on fix a flat for offroad use, too great a chance for irreparable sidewall damage if you're around rocks. Should be fine for street use where you're most likely to just pick up a nail.
 

·
Super Moderator
Joined
·
15,121 Posts
A used 37 in the cargo area is a great idea... Just strap it down as mentioned above.

I will also say, that 3.5" of lift and flat fenders would have been all you needed for the 37's. This is 3.5, flat fenders and 38's. But it also shows the spare when wheeling.
4447667
 

·
Super Moderator
Joined
·
5,308 Posts
With flat fenders 2.5” - 3” of lift is enough for 37” tires in my experience. The lift part of running 37’s is the easy part.
Anyway, with 37” tires you want to upgrade your axles and steering, I don’t think I would run 37’s with a D30. And even with a D44 I would / do run hd ball joints, stronger axle shafts ( we run RCV), stronger tie rod (we run aluminum), hydro assist (we haven’t installed that yet), and bigger brakes ( we run Dynatrac). If you are hard on the skinny pedal, bracing for the axle tubes would be good.
 

·
Super Moderator
Joined
·
5,308 Posts
Yeah but like, 9 inches is more lift than 3 inches
That is true, but more lift is going to bring with it it's own issues. And running 37" tires already has enough issues.
You will probably need a front drive shaft soon, stronger axle shafts front and rear, bigger brakes, the rest of the hydro steering, and heavy duty ball joints. You may also want / need heavy duty track bars, a stronger tie rod, and better shocks. And your 1/2" wheel spacers sounds like a really bad idea. The only way you can run a wheel spacer that small is if it is just a spacer that goes between the wheel hub and the wheel, vs normal Jeep wheel spacers that bolt to the wheel hub and then the wheel bolts to it, using two separate sets of wheel studs. Running wheel spacers that are just a spacer without their own wheel studs, especially with big tires, is asking for failure if you wheel.
But its your Jeep, have fun.
 
1 - 20 of 36 Posts
Top