UCA Ball Joint Angle

[BroncoAdventure]

2024 4dr Black Diamond. 2" spacer lift combined with Bilstein 5100 set at clip #2 for an additional 1.5" of lift with stock springs. Upgraded to Zone Offroad UCA. Alignment specs are now back within spec. 3 weeks in, rides great, solid, not floaty, slightly firmer than stock (how I like).

Daily driver roads and dirt trails. No offroading.

The picture shows ride height ball joint angle. Does this look steep?

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[Brian_B]

As long as it doesn’t overextended at either extreme of travel the ride angle of the ball joint doesn’t really matter. It’s not like a CV we’re it’s got rotating parts inside

If the CV is at the same angle though…

 

[BroncoAdventure]

As long as it doesn’t overextended at either extreme of travel the ride angle of the ball joint doesn’t really matter. It’s not like a CV we’re it’s got rotating parts inside

If the CV is at the same angle though…

How does this look? I do have a diff drop bracket arriving tomorrow as well.

 

[Brian_B]

Using my caveman protector that looks about 15 deg

The further off 0 the more wear the CVs will take. So I’d say if you have a diff drop coming that’s good.

I think mine is running at around 7 deg at ride height.

There is still that max angle you need to worry about at the extreme ends of travel - the m210 and most aftermarket axles have a max angle of 28 deg. I’ve heard the m190 was 18 but that seems pretty low. I don’t think there is a spec for rise height but the further from 0 you go the more the CV has to work - and it works any time the axle is rotating

 

[BigMeatsBronco]

This looks relatively normal for lifted angles at ride height. But ride height isn't always what breaks stuff... Usually it's when the tire is drooped all the way down at full extension of the suspension, that's when the angles become extreme and the strength of the parts is marginal under wild angles. I would drive the truck into a situation where one of the front tires is off the ground or nearly off the ground and then reevaluate your angles.

 

[BroncoAdventure]

Using my caveman protector that looks about 15 deg

The further off 0 the more wear the CVs will take. So I’d say if you have a diff drop coming that’s good.

I think mine is running at around 7 deg at ride height.

There is still that max angle you need to worry about at the extreme ends of travel - the m210 and most aftermarket axles have a max angle of 28 deg. I’ve heard the m190 was 18 but that seems pretty low. I don’t think there is a spec for rise height but the further from 0 you go the more the CV has to work - and it works any time the axle is rotating

I appreciate the feedback Brian! I'm going with Dobinsons diff drop kit. One thing that I've noticed about this kit is it seems that it doesn’t include the difficult to install 2 bolt spacer that @Dusty and a few others had a time installing.

@TeocaliMG @BigMeatsBronco When reading the Dobinsons part description for this bracket, it states

• Some early batches of this kit included extra unnecessary hardware

I do not see the 2 bolt bracket being installed in their instructions, it seems that they've left it out and deemed it unnecessary. I'll give them a call tomorrow to confirm...just wanted to get your thoughts on it.

https://exitoffroad.com/product/dob...d_QOV6uHOFropy3XkBBZW1T_G7UFytx9Oi4ZkdzvNmz3z

 

[TeocaliMG]

I appreciate the feedback Brian! I'm going with Dobinsons diff drop kit. One thing that I've noticed about this kit is it seems that it doesn’t include the difficult to install 2 bolt spacer that @Dusty and a few others had a time installing.

@TeocaliMG @BigMeatsBronco When reading the Dobinsons part description for this bracket, it states

• Some early batches of this kit included extra unnecessary hardware

I do not see the 2 bolt bracket being installed in their instructions, it seems that they've left it out and deemed it unnecessary. I'll give them a call tomorrow to confirm...just wanted to get your thoughts on it.

https://exitoffroad.com/product/dob...d_QOV6uHOFropy3XkBBZW1T_G7UFytx9Oi4ZkdzvNmz3z

There are different ways to "drop" the differential. If you move it straight down, you don't want the spacer between the rear bushing bracket and housing, but you do need to relocate the rear attachment to be lower (bushing dog-bone to frame). This can be a pain since there is a weld nut there, meaning it's a bit more involved than simply unbolting it from the top of the frame bracket and refastening it on the bottom side.

The other way to get a moderate amount of drop (what I did) is to tip the differential down, since you are introducing a small rotation to the differential, you want to space the housing back forward, hence the spacer between the rear bushing bracket and housing. IMO this is the easier method for smaller amounts of drop.

 

[BroncoAdventure]

Differential drop done, however, I cannot recommend the Dobinsons kit. Their kit doesn't include necessary hardware, which is bazaar to me. The OEM diff bracket has 2 welded on nuts... the Dobinsons does not. Ok cool, naturally one would think the Dobinson kit should include 2 new nuts and bolts to mount the bracket and affix the diff to the bracket, or at least 2 new nuts to be able to reuse the original OEM bolts...no they did not include either.

Simple solution, buy 2 new nuts and bolts at the local hardware store...unfortunately I already had the OEM bracket removed therefore I was forced to cut the nuts off the OEM bracked and use those...simple spot welds.

Funny thing is, prior to installing the kit, I spoke with someone at Dobinson and they assured me all that I needed for the install is included with the kit. BS

 

[Bird Dog Off Road]

Differential drop done, however, I cannot recommend the Dobinsons kit. Their kit doesn't include necessary hardware, which is bazaar to me. The OEM diff bracket has 2 welded on nuts... the Dobinsons does not. Ok cool, naturally one would think the Dobinson kit should include 2 new nuts and bolts to mount the bracket and affix the diff to the bracket, or at least 2 new nuts to be able to reuse the original OEM bolts...no they did not include either.

Simple solution, buy 2 new nuts and bolts at the local hardware store...unfortunately I already had the OEM bracket removed therefore I was forced to cut the nuts off the OEM bracked and use those...simple spot welds.

Funny thing is, prior to installing the kit, I spoke with someone at Dobinson and they assured me all that I needed for the install is included with the kit. BS

Yeah, just got mine and found this out as well. Sent them a very snarky email asking why they don’t mention this in their instructions or on their site. I’m just gonna head to Ace Hardware and buy the ones that Broken innovations uses on theirs.

 

[BroncoAdventure]

Yeah, just got mine and found this out as well. Sent them a very snarky email asking why they don’t mention this in their instructions or on their site. I’m just gonna head to Ace Hardware and buy the ones that Broken innovations uses on theirs.

Unreal dude. I sent them an email with a link to my post above. Thanks for posting and confirming that I'm not the only one. This would not have been an issue for me had I not trusted what their rep told me.

 

[Rkgzx9leftcoast]

I Believe 5100`s like the 6100`s are the same length as stock shocks. The added lift comes from compressing the spring while moving the clip up. Should have the same down travel as stock shocks. You are just driving around with the shocks extended down compared to the stock ride height. If that makes sense.

 

[87-Z28]

I Believe 5100`s like the 6100`s are the same length as stock shocks. The added lift comes from compressing the spring while moving the clip up. Should have the same down travel as stock shocks. You are just driving around with the shocks extended down compared to the stock ride height. If that makes sense.

indeed.

but I think the OP has also added a 2” spacer effectively increasing his extended length. That is where the concern is.

I personally don’t like diff drops. They only slightly help with CV angles but almost always cause CV plunge to increase. Virtual impossible to just move diff down vertically and maintain oem plunge.

I would just not increase shock extended length past the 24.3” limit for max oem CV angle. Or get different CV axles that allow greater angles.

 

[BroncoAdventure]

indeed.

but I think the OP has also added a 2” spacer effectively increasing his extended length. That is where the concern is.

I personally don’t like diff drops. They only slightly help with CV angles but almost always cause CV plunge to increase. Virtual impossible to just move diff down vertically and maintain oem plunge.

I would just not increase shock extended length past the 24.3” limit for max oem CV angle. Or get different CV axles that allow greater angles.

Yes, Bilstein 5100s and 2" spacers

 

[CitrusBronco]

How much does this drop the axle? I dont see that info on their website.
It does not look like it’s more than about a few inch’s, does a 2” spacer and this diff drop over drive the cv plunge? Does this not equal it out to prevent plunge?

 

[87-Z28]

How much does this drop the axle? I dont see that info on their website.
It does not look like it’s more than about a few inch’s, does a 2” spacer and this diff drop over drive the cv plunge? Does this not equal it out to prevent plunge?

The Bronco IFS double wishbone is basically just a 4 rigid link mechanical mechanism. UCA, knuckle, LCA, and frame as the last link. The CV axles are attached to the knuckle (hub) at the outer and frame at the inner (diff). In theory, if inner CV pivot point is placed along the axis created by the UCA and LCA frame pivots, then zero plunge will occur. CV axle length will not extend or contract as suspension cycles. This is the design goal.

When adding a diff drop the CV axle angles in droop improve but the inner CV pivot point is no longer along the optimal axis for plunge. So the consequence is usually increased plunge.

It is difficult to drop FDU and not affect plunge. There are three mounts. If all of them have the identical bracket offset then inner pivot moves perfectly vertically downward. If not, then there will be some rotation in FDU and pivot point will move for-aft also. As stated it is very difficult to optimize plunge when dropping FDU. Especially since oem location is already near optimal.

the oem configuration has very little plunge, +/- 2 mm. Max CV angle in droop is 22 degrees. See first figure.


FULL DROOP AT ZERO SHOCK DISPLACEMENT

Adding a 2” spacer lift at wheel (1.25” thick spacer at strut due to 1.6 MR) results in increased CV axle angle at full droop. 32 degrees now instead of 22. This is the concern with a spacer lift. Notice that oem plunge of +/- 2 mm remains since inner cv pivot was not moved. See second figure.

Third figure shows the 2” spacer lift with a 1” pure vertical diff drop. Max CV angle improves to 28 degrees but plunge is negatively affected. Now +/- 8mm.

fourth figure shows the 2” spacer lift with a 2” pure vertical diff drop. Max CV angle now improves to near stock at 24 degrees but plunge is now +/- 17 mm.

at some point plunge issues become a concern. These plots are for a pure vertical drop which is not likely for these kits. Some optimization may be possible to rotate FDU slightly and improve plunge. Nonetheless there is a trade off between CV angles and plunge. A minor FDU drop of near 1 inch is perhaps the best of both worlds, smaller angles and manageable plunge. I would not drop much more than that.

Nothing wrong with a diff drop and perhaps a good compromise. I just don’t like them and would rather address the issue with CV axles that can handle more abuse.


EDIT. Added link for more details on Bronco IFS kinematics.

https://www.bronco6g.com/forum/threads/kinematic-model-of-oem-sas-front-suspension.108300/

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