Some stock suspension calculations and measurements

[87-Z28]

“moves the wheel “ is a bad choice of words. More like moves the axle shaft axis and allows for same a mount of extra wheels travel

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[87-Z28]

Also maybe drive shaft attachment angle, length , geometry; depending on how diff is lowered.

 

[mpeugeot]

I will add the diff dop to the chart so it can be visualized. But essentially a 1” drop extends wheel 1” from frame. So if shock length is increased 0.66” (1.5 motion ratio) then original geometry is retained. If shock length is not increased then yes over extension in compression is possible Everything moves towards compression side. Pretty sure that is correct. I will run the numbers and update.

So, it sounds like a possible correct answer to keep close to the original geometry would be a 0.66" spacer lift with a 1" diff drop. The upside is that you can run a larger tire without rubbing (especially if you were to combine it with a 1" body lift).

Although, I don't see myself trying to run 37's, much less 35's, yet. I might run a 34" tire, but I already have plenty of room for that.

 

[Snacktime]

Differential drop is a much more critical modification for people on coilovers who are over extended. Balances out the downward over travel.

I went with a differential drop to allow better internal CV engagement when crawling obstacles. I have limited up travel due to my sway bar so I am not worried about the fully compressed side of the equation.

 

[87-Z28]

The numbers are not absolute. They depend on use case. Snacktime has a lot of hard hours (articulating at full droop).

I think it has become pretty clear that more than a 1” increase in shock length (1.5” at the wheel) and lots of hard hours put the CV durability at risk. Many of the coilovers fall into the >1”+ category. However if you don’t wheel hard, then ride height will be in factory specs and CV would likely be fine. Small spacer lifts <1” are likely not much of a concern.

lots of tools and combinations available to run larger tires. Spacers, coilovers, diff drop, body lift, spring rates & preload. The design envelope is tight but very possible to stay close to factory geometry.

 

[87-Z28]

The fdu gets loaded through the axle half shafts via the tires. The half shafts have an offset wrt the frame mounting for the fdu. This results in a moment arm producing bending at the mounts.

A simple thought exercise, adding 10” spacers to lower diff with very long bolts (12”+) clearly produces bending loads (increased moment arm) that will tear up the mounts. So how much extra bending load occurs with 1-2” diff drop? And will factory mounts have the required excess capacity? Not sure I would just put a spacer in there. The increased mounting loads should be careful evaluated and tested. But easy enough to fabricate properly designed mounts. Just not sure how well tested some of these aftermarket parts are. There are always design tradeoffs that require thought and testing.

@Snacktime did you fab your own spacer/mounts for the diff drop? I am eventually going to drop in the m210 fdu. Mainly for locker and gearing. Not convinced strength is much different. I would like to add a diff drop while I am in there.

 

[mpeugeot]

The fdu gets loaded through the axle half shafts via the tires. The half shafts have an offset wrt the frame mounting for the fdu. This results in a moment arm producing bending at the mounts.

A simple thought exercise, adding 10” spacers to lower diff with very long bolts (12”+) clearly produces bending loads (increased moment arm) that will tear up the mounts. So how much extra bending load occurs with 1-2” diff drop? And will factory mounts have the required excess capacity? Not sure I would just put a spacer in there. The increased mounting loads should be careful evaluated and tested. But easy enough to fabricate properly designed mounts. Just not sure how well tested some of these aftermarket parts are. There are always design tradeoffs that require thought and testing.

@Snacktime did you fab your own spacer/mounts for the diff drop? I am eventually going to drop in the m210 fdu. Mainly for locker and gearing. Not convinced strength is much different. I would like to add a diff drop while I am in there.

Fair enough, but since I can fabricate reinforcement of the mount, I am not terribly worried about the strength of the mount unless the factory really did a piss poor job in the first place. I do expect any drop would benefit from appropriate reinforcement, but it should be easy to overbuild any drop mount that short.

 

[mpeugeot]

The numbers are not absolute. They depend on use case. Snacktime has a lot of hard hours (articulating at full droop).

I think it has become pretty clear that more than a 1” increase in shock length (1.5” at the wheel) and lots of hard hours put the CV durability at risk. Many of the coilovers fall into the >1”+ category. However if you don’t wheel hard, then ride height will be in factory specs and CV would likely be fine. Small spacer lifts <1” are likely not much of a concern.

lots of tools and combinations available to run larger tires. Spacers, coilovers, diff drop, body lift, spring rates & preload. The design envelope is tight but very possible to stay close to factory geometry.

I am not looking to get the vehicle super lifted, but I do tend to challenge the equipment that I have.

One reason to limit myself to 35's or less is to limit my stupidity. It's the same reason I purchased a Suzuki SV1000s and not a Suzuki GSX-1000R. It was bad enough that I was banging gears on the SV1000s, I would have easily ended up in jail on a GSXR.

I am trying to maximize the ability of the Bronco within that window... Articulation is why I went with the Badlands suspension vs the Sasquatch suspension on my OBX (before other options were readily available). I may or may not do a 1" spacer and 1" diff drop. I also considered just doing a 1" body lift. It's subtle but really would prevent any chance of rubbing on 35's, although I am pretty sure that I could run 35's just with the Badlands suspension.

The CV's definitely are not abuse tolerant, I pulled one apart on the hub side just changing out the suspension (I was being stupid and not thinking clearly). I am pretty sure that at full droop without the sway bar that it would probably pull apart again.

 

[87-Z28]

I am in the same boat. Trying to keep CG down and geometry close to design envelope yet maximize lift. I think a small diff drop, small spacer lift, small body lift, and good selection of spring rate/preload with minor fender work can nicely accommodate 37-38s. Very similar to what snacktime has been doing and you don’t need to empty the bank account.

 

[Snacktime]

Differential Drop
I bought a 1" thick stainless spacer(and a new bolt) on eBay for the passenger side. Cut the factory mount up and added material. I would like to make an upper mount extension at some point.

When I looked at my failure while right footing it at the offroad park. I was offset climbing a step up and the passenger CV was fully extended. The inside CV split open near the outside of the cup. I know I was over extended. My goal was to get to a stock like setup and then figure out what was the safe range. Real world says the front cvs can handle icon travel, I am just not sold that this is a good idea for a wheeling rig.

M210 differential is my next big purchase after I couldn't get my driver's CV stub out (probably twisted splines). Not sure if this a strength upgrade but the m210 has the highest chance of aftermarket support. My concerns are the bearing supporting the internals riding in the shafts themselves. Need a bearing race to break up the point load/stress. Lots of things to upgrade that are not lift and tires.

 

[Snacktime]

@Merc4x4 and @87-Z28 got some 4wp shock numbers for you.

Boss4x4 had a set to cheap to pass up!

Front 24 5/16" long, 6 5/8" travel and 1 3/8" bump stop.

Rear 26 7/8" long, 10 1/8" travel and 1 3/8" bump stop.

 

[mpeugeot]

@Merc4x4 and @87-Z28 got some 4wp shock numbers for you.

Boss4x4 had a set to cheap to pass up!

Front 24 5/16" long, 6 5/8" travel and 1 3/8" bump stop.

Rear 26 7/8" long, 10 1/8" travel and 1 3/8" bump stop.

Which shocks are they?

 

[Snacktime]

4 Wheel Parts Factory '21+ Bronco 2.5" VSRT Coilovers
https://www.boss4x4.com/ProductDetails.asp?ProductCode=4WP8-52233BX-1&CartID=1
https://www.boss4x4.com/ProductDetails.asp?ProductCode=4WP8-52233BX-2&CartID=2

 

[Merc4x4]

Make	F Compressed	F Extended	F Travel	R Compressed	R Extended	R Travel
Sas Bilstein	17.0625​	23.3125​	6.2500​	18.6250​	26.1250​	7.5000​
ADS	18.0000​	24.6440​	6.6440​	17.7190​	27.7230​	10.0040​
King	18.5000​	24.6000​	6.1000​	18.5000​	27.0000​	8.5000​
Fox	18.7900​	24.2600​	5.4700​	19.2400​	27.2100​	7.9700​
Eibach 2.0	17.7700​	24.2000​	6.4300​			0.0000​
Icon	17.6000​	24.5300​	6.9300​	18.3600​	28.9000​	10.5400​
4WP	17.6875​	24.3125​	6.6250​	16.7500​	26.8750​	10.1250​

Thanks!

@Merc4x4 and @87-Z28 got some 4wp shock numbers for you.

Boss4x4 had a set to cheap to pass up!

Front 24 5/16" long, 6 5/8" travel and 1 3/8" bump stop.

Rear 26 7/8" long, 10 1/8" travel and 1 3/8" bump stop.

 

[mpeugeot]

4 Wheel Parts Factory '21+ Bronco 2.5" VSRT Coilovers
https://www.boss4x4.com/ProductDetails.asp?ProductCode=4WP8-52233BX-1&CartID=1
https://www.boss4x4.com/ProductDetails.asp?ProductCode=4WP8-52233BX-2&CartID=2

Well when I wear out the Bilsteins, this is probably the direction I will go. How long it will take to wear them out is anyone's guess, they still ride well.

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