Just upgraded to 37" tires!

[Timmy]

Woo hoo! Just upgraded to 37" tires. Found a set of almost new Toyo's at a good price that I just couldn't pass up on Craigslist.

My previous were Micky T Baja ATZ's. I also run DuraTrac studded in the winter. I must say, these 37" tires are smoother and quieter on the road than the Baja ATZ's, which is incredibly surprising to me given that they have much wider spaced lugs on them. The upgrade came sooner than I was expecting as I was planning on getting other things upgraded in preparation first, but I figured it would be drivable enough as it was. My only issue right now is that I am getting a touch of front bumper rub when I crank the wheel hard and hit a bump. I'm actually finding it rubbing in three different spots. I was planning on upgrading to an AEV bumper, so that just moved up on the list (it was my next upgrade anyway.) They are also rubbing slightly on the air deflector under the bumper, which I'll lose with the AEV bumper, so I don't really care. There is slight rub on the front inside fender down at the bottom by where the step is located, but it just needs a little more securing to get it tighter to the body and it should be good to go. I know if I get flexing this that the fender itself will rub, so down the road I'll probably switch out to flat fenders.

On the power side of things. I'm still running the 3.73 axle ratio (it's a manual trans.) It's not horrible, and in fact the change was less dramatic than I was expecting from the 35" tires. It is still 100% drivable in every day traffic. I'm just holding in a lower gear a little longer, so really, it's only 1st gear and 6th gear that are the biggest issues. I think I'm going to follow Ross's lead on this one and only upgrade to 4.56 gears. I think 4.10 gears would have been more than fine for the 35" tires, so 4.56 should be great for the 37". That being said, I'm looking forward to hearing from FerrariFast on this as I know he just got his Jeep with the same tire setup, but went with 4.88 gears (granted he got a supercharger as well!)

Looks wise... Well... When I bought the Jeep with the 35x12.50R20 tires on it and 4" lift, I always felt it looked a high-school-ish, like the Jeep was trying to jump off the tires. Now, it looks proper. Today my point was proven perfectly. I picked my daughter up from school and her boyfriend told her "the tires look too big on your dad's Jeep." And... point for dad. Only a high school student would make such an outlandish comment, and this is the same kid that thinks an AWD Subaru could go anywhere my Jeep could go.

As we all know, pics hardly do justice, but here you go...

Before with 35" Micky T Baja ATZ's on 20" XD Bully wheels


After with 37" Toyo Open Country M/T's on 20" XD Bully wheels


Ps. If someone could send me a link to what type of gear I need to purchase, I'd be grateful. I've looked on northridge4x4 (they are in Seattle, just 4 hours from me so shipping is quick) but there are so many different gear options I'm not sure what all I would need for a 4.56 gear change.

[ljvsnyder]

Looks good, you should challenge the boyfriend with an off road adventure and he can drive the Subaru. Make sue you take plenty of recovery gear, you will be towing him a lot. From the looks of the 37's you may need to upgrade those fenders and chop the bumper.

[Timmy]

Looks good, you should challenge the boyfriend with an off road adventure and he can drive the Subaru. Make sue you take plenty of recovery gear, you will be towing him a lot. From the looks of the 37's you may need to upgrade those fenders and chop the bumper.

Oh believe me, if he actually OWNED a vehicle, I would. Really nice kid, but honestly, he was riding with us and made a comment that Subaru's were made in German. I told him "I hate to burst your bubble, but Subaru's aren't German. You know what a Rice Burner is right?" Well, you can imagine the rest of the story.

Yep, fenders and bumpers on the list. I've actually been prepping for 37" tires for a while, and I was going to do fender and bumpers before the 37" tires, but the opportunity came up so I jumped on it. I can't really go banging around off-road right now because I know I'll rub on the fender. When I back up and turn sharp, the bumper rubs. So... I'm going to get the new bumper here pretty quick to at least take care of that.

Fortunately I already have the Teraflex rear tire carrier, so at least I don't have to upgrade that, but I do need to go get a new 37" Toyo mounted on my spare as it is still holding my 35" Baja's. Why in the world people only buy and sell 4 tires at a time on craigslist is beyond me. A complete set to me is 5 tires. Oh well, saved enough money by buying on CL to save on the cost of a new spare ;-)

[KaiserBill]

I've got to say the Subaru Rally WRX Impreza from the mid-1990's was pretty unstoppable in FIA Rally course. Obviously, the Rally car isn't designed for crawling over obstacles like a lifted Jeep is but then again you probably would be doing a 120-130mph on an unprepared surface like the Impreza can.

https://www.youtube.com/watch?v=eTrBxVtQbe8

However, the best of both worlds-- Current 7 time Champs of the Dakar the KAMAZ...

https://www.youtube.com/watch?v=8FcEuuakWPg

It can do a 130mph in the open and crawl over rocks too...


I do have to ask one question like the kid if you are doing mostly highway driving why get the 37's? If it is just for the looks okay. You'll need to get a pinion puller for the pinion gear. As for gears get the best ones you can afford. Make sure they have a lot of contact between the teeth when they mesh. That way you will distribute the torque across the complete surface of the tooth. That is important cheap gears tend to have less contact area and can easily damage the teeth under high torque loads.

Here is the truth about gearing a truck-- you really need more than just a change in differential gears. You really need to change the gearbox gears as well. But no one does that-- unless you are a rally racer. Because you need to change the torque rise between each ratio to really get the best performance for your vehicle. The charts for tires and differentials only give you an approximation of the normal performance of your vehicle with the stock stuff. Since I don't care about top speed too much-- I always go for mechanical advantage. I would pop- 10:1 differential gears into the truck if I thought it would give me the Earth moving performance I wanted in 3 feet of snow or mud. But that is me.

[UselessPickles]

You really need to change the gearbox gears as well. But no one does that

No one does that because it's not actually needed. Transmission gear spread impacts how you make use of the engine's power as you accelerate and shift through the gears. Changing tire size has no impact on this relationship at all. If the transmission is already matched well enough to the engine's torque/power curve and the general intended usage of the vehicle, and it's not a racing transmission with reconfigurable gear ratios, then any benefit of optimizing the transmission setup to your personal preferences is not going to be anywhere near worth the cost/effort for anyone without very deep pockets.

Then again, if you have a configurable racing transmission, you probably already have pretty deep pockets, and also a vehicle for which there exist after market racing transmissions.

[2k13jk]

If your going to stay with 37s for a long time i recommend 4.88 gears

[Pznivy]

If your going to stay with 37s for a long time i recommend 4.88 gears

I say the opposite. Autos need gears worse than manual trans. Think about what you are spending on the gear change, and think about a power mod. A supercharger would make a huge difference.

I say pay for everything else and drive for a while with the 37s and see how you feel.

I drove 37s with 4.10 for a long time. Then i thought 4.88 was too much when I changed. But we do a lot of highway driving in the northeast.

[FLIPmeOVER]

Nice upgrade. I love the toyos. The aev bumper will be heavy. Are you keeping stock flares?

PieFace (ross) will be here sooner or later that guy is the gear guru.

When you do get gears...Get Yukons. No matter what you may have read.....LOL

[JeepLab]

Ahhhhhh Gear talk!..... Seems like yesturday I was in the same spot, and got it wrong.

Now, take into account, that BB had a supercharger. So my experience is with a very light tire, (km2) Light wheel (Weld Racing at the time, PMtruck Wheels now)

So if your truck is a slug now with the toyos, and whatever wheels you have, You may want to consider 4.88. If its "livable" with 3.73, then I say go to 4.56.

What you are giving up with the 4.88 is the highway criusing gear. BB was SLOOOOOOOOW with 4.88s. I swore I ruined her. with 4.56s now, she is still not the rocket she was with 4.10 on the highway. But she is more responsive across the RPM band.

Gears are a leap. You want to be certain you get it right the first time. The expense for doing it twice is horrendus.

[Timmy]

So if your truck is a slug now with the toyos, and whatever wheels you have, You may want to consider 4.88. If its "livable" with 3.73, then I say go to 4.56.

Yep, what you just said is exactly the way I feel. It is livable with 3.73 right now. If I absolutely had to, I could drive her with 3.73 until the day I got rid of her and enjoy it a ton. I really think 4.56 is going to be the right gearing for me.

So... Can you guys give me an idea, exactly what do I need to purchase? Are we talking two of these for $238 a piece or is it something more? I have a local shop just 20 seconds from my house that could probably do the install for me.