jjjmm56

I've read a number of posts on how ball joints will fail when running 37 " tires. Does this relate to off road only? Will someone please explain why? I can see putting extra load on them if your running a large wheel spacer or offset and throwing the scrub angle off. This will also cause many steering related problems .So if calculating tire dia and wheel offset you should be able to keep SA close to factory settings. Thanks.

Mark Doiron

I'm not sure about BJs and 37" tires, but if you're running OEM BJs, they have a plastic lining that makes them greaseless. And their lifespan is pretty short with any size tire regardless of use case--on the order of a few tens of thousand miles--before that plastic lining is worn out. I imagine 37" tires and hard use shorten that more. Go with a quality BJ (I have Synergy, but there are other good brands), grease them regularly, and you should be fine.

karls10jk

A 37" (or really even some of the more aggressive 33's) are a TON more weight you're trying to control than what they were designed for. There's a reason it took jeep so long to finally offer a 33" on the Rubi and even then, it was a tame 33".

Schlieko

This is the classic... upgrade to 37s only if you have an extra $10 grand in the bank. They were not kidding. I went through ball joints, some on the expensive side, like candy. Finally just paid for Dynatrac Heavy-Duty BallJoints, which I thought were wicked expensive. But they are bulletproof. Have gone way longer on these than any other brand, including Teraflex.

I get people who come up and talk to me about my Jeep. If they ask me specifically about 37s, I really tell them to proceed to 37s with (extreme) caution. I ran 35s basically on stock components for years. Got to 37s and it was a whole new ballgame. Not sure it was worth the extra 2" in the long run.

jjjmm56

Ok thanks, It's not an alignment issue it's crappy ball joint from the factory, and more vibration from a bigger tire.

Jay2013jk

I have to disagree.. the BJs from the factory work fine.. I have 2013 = 78K on with 33s and 2016 = 48k with 33s on both of my JKUs..95% DD. They pass State Inspections every year.. It is more about tire / wheel weight and why do most put 37s on .. HEAVY Off Road action.

ronjenx

My OEM ball joints lasted 77,000 miles. My Synergy ball joints now have 134,000 miles on them and still have no play in them. (Greased at each 3,000 mile tire rotation.)

resharp001

I will only say I have yet to see a statistician on here calculate what is force is really applied to a BJ when a 37" tire with 3 or 3.5" BS wheels (or + spacer to accommodate) is used. I am not some math wizard so I will not comment on scientific facts, only what I have observed in the real world. If you want to run 37s in a D30 or 44 axle, you need to look at Rare Parts. Schielko at some point will be referencing my joy in rebuilding DT BJs which is not worth the effort, though I hope for better results. Just saying, you cannot go by net BS and wheel diameter unless you are some math wizard accounting for leverage in wheel being pushed further out, max articulation, and tire/wheel weight combo. There are many things I give my general opinon about....this one I feel pretty strongly about. The sad part is it when it fails, it will have nothing to do with offroad. It can be 80mp on some metropolitan highway/interstate when you lose control due to some DW that is the result of some shit BJ. Anyhow, just my 2c on this random tuesday night.

jjjmm56

Thanks for your reply. I build a lot of hot rod frames and suspensions ,straight axle and air bag so I may be looking at this in a different way. I know when there is a problem with death wobble, front wheel hop ,and scrubbing the tires, one of the things I look at is the scrub angle. It's not really a mathematical equation but a physical alignment. A line thru your ball joints or king pin and a line thru the middle of your tire that intersect at the contact patch under the tire. Large neg offset and large spacers can increase load on ball joints, add vibration resulting in steering problems . Add to this a tire that may be out of balance, bad wheel alignment ,loose steering and the problems increase. I know that big tires with a big offset look good but can also cause other issues. So when increasing tire dia the line thru your ball joints gets longer so yes you would need a bigger offset. But you need to not reach that point of no return. Again I relating to my experience with hot rods, but have come to find most suspensions follow the same criteria. Thank you for indulging my ideas.

Sv_dude

OP, in your original post you ask if issues related to ball joints and 37’s apply to off-road only. I wouldn’t say no but when playing in the rocks or other weird terrains, it’s not uncommon to have a front wheel off the ground. This puts a lot of extra weight on one front tire, couple that with trying to steer in an ugly situation, that puts a lot of extra stress on the ball joints.