Difference between 35's and 37's

[Joe3322]

Hi Everyone,

I'm new to this forum and Jeeps. I've read what feels like millions of forum and debates on this issue but main question which I have not found an answer to is: Is it a weight or size issue for the axle and drivetrain? For example would 78lbs 35's be better or worse than 76 lbs 37's? Thank you in advance for feedback and I look forward to hitting the trails with you guys down here (just moved from Asheville Area).
Just for reference I have 30/44 axle and regearing to 4.88 with ARB and Artec Armor.
Thanks
Joe

[tcdawg]

It is both a weight and a size issue.

If you had a 35 and a 37" tire that both weighed the same, the 37" would still provide more "leverage" due to the size.   Think of a lever or a cheater bar you would use to get a bolt off.  The longer the lever the more torque at the bolt with the same force at the end(you).

And, bigger tires typically weigh more but not always.  If they do weigh more you then have both more force and more leverage.


But....bigger is better.  Everyone knows that  //;D//

[Joe3322]

Thank you, that makes a lot of sense. Reason I asked is because I was looking into Nitto Trail Grapplers since I've had them on another vehicle and loved their performance but never realized how heavy they were for a 35. I just started offroading and quickly found my jeep dragging alot, so I picked up a set of rock hard armor (3 piece) to protect the undercarriage but that doesnt solve my clearance issue. So I'm in the process of ordering a RK 3.5" X Factor and was tempted to go with 37's but its starting to look like the extra 2" adds ALOT of extra cost and headache. So...back to my original plan...Opinion?

RK 3.5" X Factor (3" Bump stops)
Fox 2.0 Shocks
35" Trail Grappler (on stock 17 with spidrex spacers)
Fox ATS Stabilizer
Artec Axle Armor

Thanks in advance
Joe

[jc79]

OK, so I wrote up the reply below before realizing you were on a D30 front.  That's really the only reason I would consider 35's.  There are plenty of guys (JKOwners, etc) that run 37's on D30.  Other guys are more conservative and think its an risky way to go. 

I'll leave my reply below because i'm still curious what extra costs you see based on moving from 35 to 37 that your plan hasn't already accounted for.

-----------------------

Curious what extra costs you are seeing... in either case you need to have the axle "armored" with C-gussets and likely a truss (if you are actually doing offroad stuff).

Some will say that a driveshaft (or 2) is required on the JKU's wit 3.5" lift, but that's not related to tire size.  And lots of guys run the stock shafts successfully for a long time and just replace when/if one fails.

You will already have all eight control arms with that lift kit... so you can push the rear axle back an inch to make room for the 37's.  You would have to trim the pinch seam and shorten the Rubi Rails.  But not much cost for that work.

Fender flare clearance will be a limiting factor if you don't trim the stock ones or install aftermarket tube fenders.  Again, the cost is minimal if you simply trim the stockers...

[clark123456]

Joe, are you planning to run forest service trails, go mudding, crawl curbs at the mall, and/or climb rocks?  If multiple...which is most important to you too be the most successful at?

[Joe3322]

I guess in the long run there should not be to big of price difference, 37's would probably wear joints and other stuff quicker but thats to be expected. The only difference I see short term (from my understanding) is regearing, 35's can live w/o regear for awhile whereas 37's would be unbearable and require regear right away but again long term that was already budgeted so savings? not really...
I know a ton of people go through this decision with they get the JKU but Im stuck between 35's and 37's.... Can a trussed axle (dana 30) hold up over time with 37's?

clark- Still really new to this but so far a lot of  forest service trails and a little climbing...I tend to stay away from just mudding. This is also my DD. I would say having a reliable DD that I can hit the Trails on the weekend.

[tcdawg]

I know a ton of people go through this decision with they get the JKU but Im stuck between 35's and 37's.... Can a trussed axle (dana 30) hold up over time with 37's?

The truss strengthens the axle itself but does nothing for what I consider the weaker link...the axle shafts, ring & pinion.  Unless you are doing high speed off road runs or REALLY bouncing your rig around you probably won't break the actually axle housing.  I think a truss is fairly cheap insurance though, because it is certainly possible to bend an axle tube, just make sure you have someone that knows what they are doing when they weld it on.

You have the newer 3.6 motor correct?  That allows you to gear correctly but not be on such a deep gear that they get weak. 5.13 and numerically up gears in the D30/44 get small on the pinion gear.

I would definitely do chromo axle shafts and  high quality U joint for the 37's.  Also, gusset the C's.

Can I D30 hold up to 37's...yes, but it depends on your driving style.  If "easy does it" is something you can live with on the rocks, then many folks make this livable .  If you like to use the throttle and spin tires, I wouldn't do it.

[tcdawg]

Thank you, that makes a lot of sense. Reason I asked is because I was looking into Nitto Trail Grapplers since I've had them on another vehicle and loved their performance but never realized how heavy they were for a 35. I just started offroading and quickly found my jeep dragging alot, so I picked up a set of rock hard armor (3 piece) to protect the undercarriage but that doesnt solve my clearance issue. So I'm in the process of ordering a RK 3.5" X Factor and was tempted to go with 37's but its starting to look like the extra 2" adds ALOT of extra cost and headache. So...back to my original plan...Opinion?

RK 3.5" X Factor (3" Bump stops)
Fox 2.0 Shocks
35" Trail Grappler (on stock 17 with spidrex spacers)
Fox ATS Stabilizer
Artec Axle Armor

Thanks in advance
Joe

I think this is a real good plan.  Good DD attributes and you will not be disappointed offroad.

[Joe3322]

Thank you for the quick reply and help. Everytime I get ready to pull the trigger I 2nd guess...but I think 35's will be more than enough so lets do this thing  //SLAMIN//.

I think a truss is fairly cheap insurance though, because it is certainly possible to bend an axle tube, just make sure you have someone that knows what they are doing when they weld it on.

I plan to do all my work at Allsouth, emailed them a couple days ago just waiting for them to respond. Again, thanks for the quick response and all the help!

[kent10sne1]

I run 35's and I can do alot, actually .. more than I should.   but over all 35's will get you alot of places 37's can go, just need to change your line a bit .

AllSouth is the place, that will make sure its done right and they treat your right.

[kvom]

If the tires weigh the same with the same wheels, then the angular momentum and hence torque at the same RPM varies with the square of the radius.  18.5^2/17.5^2 shows 37s would put 11% more strain on your drive components when subjected to a sudden stop.  In reality it would be somewhat more since the rubber contact patch will be larger and hence more likely to impart more stopping force.

Most breakage come from staying on the gas while bouncing the front or having the tire bound up.  In such situations you can break the shafts on 35s too.

If your current suspension clears 35s I'd go with that plus chromolly shafts.

[Raisinhead]

I went from heavy 35s on 18s (Toyos) to lighter 37s on 17s (mtr-k). Overall, I ended up being a little lighter with the new set up, but bigger tires. I don't notice a significant difference in the road. I did find a formula that would have solved the question, but I think it's on my old phone- I'll look for it.

I would echo what these guys already said. Mostly depends on your wheeling style. Many of us run/ran 35s and have been able to handle some pretty crazy obstacles. Most of us rather capability over looks. I'd take a jeep on 35s with less worry about breaking before 37s on a weak set up.