Air/Hydraulic Bump Stops and Bent Axles

[KlausVanWinkle]

All of us JKU owners have heard the stories about smiling front axles. Supposedly, the Dana 30 and 44 axle housings aren't up to the task and bend under hard use. Somehow larger tires makes it more likely to happen.

If this is actually a problem, I suspect the bending probably doesn't happen when crawling as much as when you hit an obstacle or unexpected ditch at speed, compounding the impact forces. If that's true, would a pair of front axle hydraulic or air bump stops help prevent this? They provide a progressive spring rate as the front axle runs out of up travel, which prevents bottoming out. Or at least softens it.

If this theory is right, then a set of air bumps might be good front axle housing insurance for those of us who would like to prevent bending their factory axle housings but don't think they need to step up to a Dynatrac prorock or Dana 60 front axle, right?

 

[kojackJKU]

Again, the bending front axle housing is WAY overblown IMO. I am replacing my stock bump stops with stockers again. Most I will use is just the teraflex speedbumps to give a bit couchy'er ride. Not for bending resistance. The reports of bent axles are mosting by people running 37s and hammering the ever loving ******** out of their rigs.

 

[KlausVanWinkle]

I'm not really worrying about it. And have a lot of things to attend to first. But I was wondering if this made sense.

 

[Comanche Scott]

It does make sense.
Gradually reducing compression speed so that the axle comes to a controlled stop will definitely help. Ride or drive a vehicle with a properly engineered setup and you can feel the difference as the compression slows to a stop.

The shocks should be valved for the stops so that they work together to properly control the rate of compression over the last 2"-3".
It will still work, but it will feel overly damped if not done together.
If you ride in a vehicle properly setup, you won't "feel" the bump stops working.

 

[KlausVanWinkle]

My friend works/worked for Fox, I'll ask him about it. I don't really want to change my bilstein AEV shocks though.

 

[kojackJKU]

If you ran the fox instead of the BILSTIENS you would be super impressed. They are a much better valved shock.

 

[Chris85xlt]

if u can weld, adding a truss or sleeving the axles tubes along with C-gussets is good insurance and cheaper then adding Air bumps or TF speedbumps.

on that note i have both the axle truss and TF speedbumps. Not sure if the Speedbumps help prevent smiling axles but it makes trail riding so much smoother at speeds or over unseen bumps and dips.

2009 JKUR with 2.5" lift on 35s and bilstien 5160s

 

[professorkx]

Again, the bending front axle housing is WAY overblown IMO. I am replacing my stock bump stops with stockers again. Most I will use is just the teraflex speedbumps to give a bit couchy'er ride. Not for bending resistance. The reports of bent axles are mosting by people running 37s and hammering the ever loving ******** out of their rigs.

^This. Way overblown unless you are stepping up to 37" tires. In addition, the weight of the tire plays a big part, which is why I pay attention to tire weight when I buy tires. For example, I've found some 35 inch tires that weigh 90 pounds, while others weigh just over 60 pounds, and that extra 30 pounds per tire is huge, as it's all unsprung weight.

My King 2.5 shocks with adjustable compression keep me from hitting my bump stops very hard, even going fast over choppy terrain. When I had the stock Rubicon shocks installed, the shock would blow through the compression stroke, then unload so fast that the front wheels would come off the ground. Hated the stock shocks. Yes, I probably work my jeep more than others, but I'm not worried about bending an axle at all with KM2 35 inch tires.

 

[*TRD*]

I think there is ultimately a three part fix to the bent axle problem.

1: Gusset - it is important to to strengthen the axle
2: Good Shocks - you need to prevent both the axle and chassis from gaining too much momentum
3: Good Bottoming Control - be controlled when you do bottom out. Plus shocks stiff enough to prevent bottoming may not ride well.

Bent axles are more related to going fast than rockcrawling. I think it takes hard driving or uncommon events to bend the axle, the average person probably isn't going to bend an axle.

I also think the bent axle situation is more common on JK's because they are super heavy, and don't have much up travel.

 

[KlausVanWinkle]

Sleeves and trusses seem like a lot of cost and warranty liability for a marginal increase in rigidity. I've looked into a bunch of combinations and decided that if it'd be better to sell the stock axle and get a prorock 44 than modify the OEM axle. I haven't experienced any issues yet. But I'm only running stock 32" BFG MTs and AEV's 2.5 lift. I'm getting ready for the step up to BFG AT KO2 35s. My plan is Evo C-Gussets and caution.

 

[professorkx]

I was reading a different Jeep Forum, and someone posted a poll on this topic. 6% of the 100+ respondents had a C issue, so just not enough to get me excited about welding on the stock axles since they have the Jeep Max Care warranty with $0 deductible for a million miles. In the unlikely event they bend, I'll let the warranty take care of the problem. If I'm declined on warranty, Prorock will be my next stop, but I have a 94% chance of never having a problem...

 

[1stDeuce]

I work for a company that makes a version of the "jounce shocks" that you're talking about. We have conducted some testing on a JK, and I can confirm that adding jounce shocks does NOT prevent you from bending an axle. IF you can restrain yourself, it MIGHT help a little, but most likely, you'll just go faster, as a bottoming event feels softer. Eventually you exceed the capability of the axles to remain straight.

We tried developing a bolt-on truss for the front, but it was a mess. Much easier to do a weld-on, or for milder use, the tube inserts and C-braces. Or just slow down. You aren't going to bend the axle rock crawling, you bend it when you hustle and overdrive the suspension.

YMMV.
C

 

[unkamonkey]

Strange, I've been running D25 axles in the front for over 47 years and never broken or bent anything. Perhaps some here need to learn how to drive off road. I have never broken anything off road.

 

[professorkx]

I broken things offroad, u joints, belts, ripped holes in sidewalls, etc, as I wheel pretty hard and know I'm going to get wonky at times that will cause failures. However, like you, never damaged an axle housing, even when wheeling hard, so not sure what folks are doing to damage an axle housing unless they are just slamming into rocks to be like the King of the Hammers guys they see on videos. My guts tell me this is a solution looking for a systemic problem that doesn't exist. Just because a few folks bent a C, which led to new products hitting the market, doesn't mean we all need to start welding on our axle housings...IMHO.

Has ANYONE here ever bent a C on a JK?

 

[comptiger5000]

Bending axles is mostly an issue when doing higher speed stuff, especially if you ever get it up in the air. Crawling around on trails at lower speed, lots of other stuff will break long before an axle housing bends.