Shock mounting angles/shock length Q's

[Fishnbeer]

I am getting close to completion of my project truck. Its a solid axle swapped s10, dana44/ford 9", sitting on leaf springs. It is time to start looking at shock mounting. I have questions about angles of the shocks.

Truck will be not see much on road use, mostly trailered to trails. Should end up being a pretty stout trail rig and be able to handle some rocks. On the rear suspension I am thinking of triangulating the mounting of the shocks. I have a pair of shock mounting tabs to weld to the top of the axle tube, but I think I may want to go with a stud or bracket or something coming off the housing to get an extra two inches or so of shock length. I will make a crossmember to mount the top of the shocks angled up and inwards. Is there an 'ideal' angle to mount them at? And once it is together, how do I determine the best length shock?

And for the front suspension, I have some shock hoops to weld on. Now I have the same question about shock angle for the front, what is the best angle? I have seen rigs where the shock is mounted perfectly vertical, and I have seen rigs where the top of the shock is tilted towards the rear (almost like caster angle). What are pros/cons of these angles?

And after I have the mounts all welded up, how do I measure for proper shock length?

 

[Tech Tim]

The ideal position is for the shock to be straight or within a degree or two) at full bump.

You start losing shock effectiveness as you go past 10° and it gets worse the more you angle them.

Most people who run their shocks at a severe angle are doing it for packaging and most don't understand how much it can hurt their performance.

 

['84 Bronco II]

The ideal position is for the shock to be straight or within a degree or two) at full bump.

You start losing shock effectiveness as you go past 10° and it gets worse the more you angle them.

Most people who run their shocks at a severe angle are doing it for packaging and most don't understand how much it can hurt their performance.

This ^

You want your shocks mounted as near vertical, and as close to the wheel as possible (in general; there are exceptions, but they don't really apply for your case). When you see guys with their shocks inboard of the springs at crazy angles, they may as well not even be running shocks since they are doing so little at that point. The reason they do that is for packaging since it can be difficult to fit a shock with enough stroke for tons of articulation if you mount them near vertical near the wheels. Cutting holes in the bed if you have to in order to mount longer shocks at proper angles is a much better solution from a performance standpoint. Something like this:

If you angle the shocks, I would suggest angling the tops towards the shackle side of the spring so that the shock will become more vertical as the suspension compresses. Also, you may have noticed that it is common for OEMs to stagger the shocks, one in front and one behind the axle, on leaf sprung vehicles. This is done to mitigate axle hop and is someting you should consider doing, especially if you are not running a traction bar. Since I assume you are running full width axles, you likely have room to build the upper shock mounts in the wheel tubs outboard of the springs if you don't want to cut through your bed floor. However, you will likely need your lower shock mounts positioned below the axle tubes still in order to fit a shock with enough stroke. If you position the lower shock mounts tight to the rear wheels, the clearance penalty should be mostly mitigated. Look at the rear shock mounts on JKs and JLs for a factory example of what I am talking about.

 

[Fishnbeer]

Thanks for the input. It sounds like the triangulated rear shocks are really just an answer to clearance issues and is not for optimal performance. I am not opposed to having shock towers come through the bed of the truck. As far as axle hop, this isnt like a high speed trophy truck or something. Is axle hop an issue at crawling speeds?

So for the rear shocks I can have the hoops come through the bed. They are not full width axles, I got a set of early bronco axles. The wheels that I got have a lot of offset to push them out wider. I do have some room between the spring perches and the brakes to mount the lower shock tabs if I want to mount them out wider, but I will likely have to angle the top inwards slightly so the tires wont rub...

 

[Fishnbeer]

Also I can put the shock tabs on the top u bolt plate on the springs. The perches/u bolts and plates I am running are pretty beefy. That top plate is 3/8" from ruff stuff. Should I consider putting the lower shock tab on top of the u bolt plate?

 

['84 Bronco II]

Thanks for the input. It sounds like the triangulated rear shocks are really just an answer to clearance issues and is not for optimal performance. I am not opposed to having shock towers come through the bed of the truck. As far as axle hop, this isnt like a high speed trophy truck or something. Is axle hop an issue at crawling speeds?

So for the rear shocks I can have the hoops come through the bed. They are not full width axles, I got a set of early bronco axles. The wheels that I got have a lot of offset to push them out wider. I do have some room between the spring perches and the brakes to mount the lower shock tabs if I want to mount them out wider, but I will likely have to angle the top inwards slightly so the tires wont rub...

Axle hop absolutely is an issue crawling, way more so than for high speed off road applications. Axle hop will deny you on ledges and steep climbs and is a great way to shock load your drivetrain and break parts. That said, if your suspension is prone to axle hop, staggering the shocks won't eliminate it, but just reduce it somewhat. The real answer is a traction bar, but you may not necessarily need one and staggering the shocks will help avoid the need to some degree.

Tipping the upper mounts in to clear the tires is not a big issue if you aren't exceeding ~10º from vertical. Obviously there is always compromise when designing a suspension system, but the main takeaway here is to avoid excessive angle. The more they are tilted, the dampening they will effectively provide.

Early Bronco axles are pretty narrow though, so you will probably be forced to mount them inboard of the springs if your springs are mounted outboard on the frame. It is not the end of the world, and most OEM vehicles are configured this way, it is just not ideal for performance.

Also I can put the shock tabs on the top u bolt plate on the springs. The perches/u bolts and plates I am running are pretty beefy. That top plate is 3/8" from ruff stuff. Should I consider putting the lower shock tab on top of the u bolt plate?

You can, that is not an issue at all, and in fact, many OEMs mount their shocks just like that. The issue with that though is that it will force you to use a much shorter shock which will limit your travel, or cut holes in the bed so that your upper mount can be places much higher.

 

[Fishnbeer]

Alright I got some ideas for rear shock mounts, thinking a simple hoop welded to top of frame, angled inboard slightly, probably with a crossbar to tie them together at the top. But then how big of a hoop do I get? I need to know shock length first right? What comes first, the chicken or the egg?

How do I go about this? I need to measure travel, so is it as simple as jacking up the truck and measure how far the axle droops, then throw 20 bags of concrete in the back and measure how much it sags? Theres gotta be more to it than this, right?

 

['84 Bronco II]

Alright I got some ideas for rear shock mounts, thinking a simple hoop welded to top of frame, angled inboard slightly, probably with a crossbar to tie them together at the top. But then how big of a hoop do I get? I need to know shock length first right? What comes first, the chicken or the egg?

How do I go about this? I need to measure travel, so is it as simple as jacking up the truck and measure how far the axle droops, then throw 20 bags of concrete in the back and measure how much it sags? Theres gotta be more to it than this, right?

Since you are building new mounts anyway, and you aren't limited by the clearance under the bed since you are willing to put the shocks through the bed, you can pretty much just pick a shock with the amount of travel you want and build around them. At some point though, the amount of travel will be limited by your springs and shackles, so there won't be any benefit to using a longer travel shock. However, having shocks with more travel than you can use won't hurt anything as long as they are mounted such that they aren't bottoming out before you are hitting your bump stops. Without seeing your setup, I imagine some 14" travel shocks would probably provide you all the travel you could ever use with leaf springs on such a narrow axle.

The problem with leaf springs is that it is a lot more difficult to measure travel and shock length than a coil suspension since the spring also locates the axle. In a coil suspension, you easily measure for max droop (when the spring starts to unseat) then pull the coil out and jack the axle up for max compression, easy peasy. With leaves, it is hard to fully load the leaf to full compression in your garage. If you want to be scientific about all this, you need to disassemble the leaf pack down to just the main leaf, then reinstall it with some sort of spacer to compensate for the leaves you took out. With just the main leaf, you can much more easily flex it out completely in your garage to get a good idea of how much travel your springs have, and how much travel your shocks need. This is also a very good time to set your bumpstops so that they will work effectively unlike most rigs you see on the trail.

Here is an idea of what this looks like (I stole this picture that mjlogan88 posted on Pirate of his Explorer with 15" of travel):