40's -vs- 42's..... Ready.. Discuss!

Brute

Hooked
Is there is a significant increase in off-road capability comparing 42" Nitto Trail Grapplers vs 40" Nitto Trail Grapplers on a Diesel Jeep Gladiator JT build?

I'm planning a significant JT build with 72.5" Dynatrac 60/80 ProRock HD axles, 5.13 gears, E-lockers front and back, PSC Steering Kit and either EVO or Rebel Offroad Long Arm suspension. Given the extra long wheel base and shallow departure angle of the JT, I'm assuming I could use the extra ground clearance and improved departure angle the 42s would provide. I'm wondering how much more capable the JT would be with 42" compared to 40" tires on the Rubicon and Moab, Sand Hollow trails.

Real world insight is greatly appreciated.
5:13?…
 
Not sure why I just read this whole thread, I'm on 35s and don't have the money to talk about 40s VS 42s lol

However on anything but a Gladiator 42s look too big in my opinion. To me 37s are a big tire and 40s seem to handle just about anything. I don't think I can justify anything bigger than a 40 because there is no reason to sacrifice more power for no significant increase in performance. Especially for these guys with 4 bangers and gear ratios for 37s...
 

wayoflife

Administrator
Staff member
Is there is a significant increase in off-road capability comparing 42" Nitto Trail Grapplers vs 40" Nitto Trail Grapplers on a Diesel Jeep Gladiator JT build?

I'm planning a significant JT build with 72.5" Dynatrac 60/80 ProRock HD axles, 5.13 gears, E-lockers front and back, PSC Steering Kit and either EVO or Rebel Offroad Long Arm suspension. Given the extra long wheel base and shallow departure angle of the JT, I'm assuming I could use the extra ground clearance and improved departure angle the 42s would provide. I'm wondering how much more capable the JT would be with 42" compared to 40" tires on the Rubicon and Moab, Sand Hollow trails.

Real world insight is greatly appreciated.
Having personally wheeled both setups, I can tell you even with a diesel, 5.38's provide just enough power. As far as performance goes, I saw no significant difference between 40 and 42. If anything, with 42s, you need to go higher and you'll still rub big time unless you extend your bump stops. Of course, on a JT, trying to keep your rear pinion from binding at a full droop is more of a challenge as well especially if you're running coilovers.

That said, I am still running 42's with my 3.6L and they look great but I'll most likely drop back down to 40's when they wear out.
 

JimLee

Hooked
Having personally wheeled both setups, I can tell you even with a diesel, 5.38's provide just enough power. As far as performance goes, I saw no significant difference between 40 and 42. If anything, with 42s, you need to go higher and you'll still rub big time unless you extend your bump stops. Of course, on a JT, trying to keep your rear pinion from binding at a full droop is more of a challenge as well especially if you're running coilovers.

That said, I am still running 42's with my 3.6L and they look great but I'll most likely drop back down to 40's when they wear out.
You running limit straps on that beast?
 

azjtr

New member
Having personally wheeled both setups, I can tell you even with a diesel, 5.38's provide just enough power. As far as performance goes, I saw no significant difference between 40 and 42. If anything, with 42s, you need to go higher and you'll still rub big time unless you extend your bump stops. Of course, on a JT, trying to keep your rear pinion from binding at a full droop is more of a challenge as well especially if you're running coilovers.

That said, I am still running 42's with my 3.6L and they look great but I'll most likely drop back down to 40's when they wear out.
I’m so close to pulling the trigger on 42’s and this thread has me seriously considering not making the move and sticking with 40’s. @wayoflife are you still feeling the same way about the 42’s a few months into 2023?
 

wayoflife

Administrator
Staff member
I’m so close to pulling the trigger on 42’s and this thread has me seriously considering not making the move and sticking with 40’s. @wayoflife are you still feeling the same way about the 42’s a few months into 2023?
So, now that we're running Currie Antirocks, we're no longer seeing the kind of rubbing that we were previously due to the torsion bars limiting the amount of flex we have. Also, now that we're running EVO trailing arms, we now have our rear pinion angle always in line with our drive shaft and that's been a HUGE plus! Without these two changes, I think we'd be way more hot to trot into going back down to 40's. That's said, going smaller is still on the radar for us.
 

Jackboeker83

Active Member
So, now that we're running Currie Antirocks, we're no longer seeing the kind of rubbing that we were previously due to the torsion bars limiting the amount of flex we have. Also, now that we're running EVO trailing arms, we now have our rear pinion angle always in line with our drive shaft and that's been a HUGE plus! Without these two changes, I think we'd be way more hot to trot into going back down to 40's. That's said, going smaller is still on the radar for us.
I have heard you say before that you like 20 inch wheels with 40s. When/if you downsize the tire size will you keep the 20s?
 

Trail Bud

Hooked
If anything, this is the direction a lot of us went in - WIDER. As in, 40x15.50's.

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Still one of my all time favorite setups.

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I like that set up too. Major fun.
 

jpkjeep

Caught the Bug
I’m so close to pulling the trigger on 42’s and this thread has me seriously considering not making the move and sticking with 40’s. @wayoflife are you still feeling the same way about the 42’s a few months into 2023?

My personal experience is that 42s provide some advantage to 40s. It depends how hard of trails you do. There have been a few obstacles so far that freinds with similar built JLs have not been able to make. We are talking 9 rated trails bordering on buggy level here in Sand Hollow (Chain Reaction, Twister, Nasty half...) It's always been a matter of that 1" breakover advantage.


That being said, my Jeep sees 2-3 trails a week and 15-20k miles a year. My Nittos look as if they will last maybe 20k. I may end up going down to 40s just because of the cost and amount of use. I'm hopeful that new competition from Mikestar and Mickey may drive the price down. I don't know if $3700 a year in tires is worth it 🤣
 
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