650lb added weight sagging rear-end

[Tonka Bronka]

I’ve got a real problem. Next investment is maybe a helper system for loaded up trips. Haven’t weighed in yet but 8 inches over front wheels and 4 in the back.

Still drives great, just did 8 hours on the road but this is not ideal.

Sumo 1.5K helpers might fix that. Could be a tad harsh when unloaded, but maybe not.

Sponsored

 

[Broncobro04]

@popo_patty is correct. If you’re running out of preload, you need to go up in spring rate. Or you need to decrease the preload in the front. The extra clearance is negligible.

As for the spacer lift in the rear, you won’t lose travel, you’ll have a longer compressed length, which doesn’t really affect much except add a little more clearance for tire stuffing. What you will also be adding though, is extended length. Not as big of an issue in the rear as in the front because of the solid axle, however you do need to keep your driveshaft angle in mind as you don’t want to exceed that. Again though, that doesn’t address the root cause which is the spring/preload issue.

 

[orion]

Quick question to all in this thread.

My rear bumper has my rear sagging and I'm looking to get heavier rear springs. I have the Eibach 2.0 coilovers and they have the +500 lbs rear springs but is there any other spring manufacturers making springs for the Eibach coilovers? I'm looking for more of a medium spring instead of an HD spring?

TIA

 

[87-Z28]

Quick question to all in this thread.

My rear bumper has my rear sagging and I'm looking to get heavier rear springs. I have the Eibach 2.0 coilovers and they have the +500 lbs rear springs but is there any other spring manufacturers making springs for the Eibach coilovers? I'm looking for more of a medium spring instead of an HD spring?

TIA

it is a challenge without knowing any of the spring specs from the various manufacturers. It would be nice to at least know spring rates and length. Each of the struts manufacturers probably have slightly different end collar locations so length is going to drive the preload you achieve.

the rear, unloaded, carries 2000-2300 lbs (based on trim level). Most broncos are carrying about 1100 lbs on one of the rear springs. assuming motion ratio of 1.0. Rear actual has a small motion ratio, less than 1.1 but close enough to 1.0. Eibach says their HD spring will carry an additional 250 lbs over the axle for a rear spring (500 total). So this represents about a 20% increase. For the identical length spring. So that is a 20% increase in spring rate. Kind of a big jump if you are not constantly carrying a bunch of stuff.

A bumper has some moment arm so equivalent weight needs to be calculated at axle from CG, wheel base, and bumper location. Just a rear bumper weight increase will increase rear spring reaction forces and decrease the front (unbalanced). Both front and rear bumpers will have a more balanced weight distribution. So a rear bumper weight of say 100 lbs is not apples to apples with 100 lbs weight over rear axle, as eibach specs out.

Lots of complications to get perfect springs for any particular use case with not enough info from the manufacturers. As others have said you want to get the springs correct for your ride height (use case) so that you are sitting near the middle of shock travel. That gives you usable travel in both jounce and rebound. Spring preload adjustments are just for fine tuning ride height since they will affect this equilibrium shock position at ride height.

you probably already know this. Just for others that may not be aware.

dobinsons makes some springs with different rates. Not sure about their length or if they will fit with reasonable preload.

 

[Tricky Mike]

What I think you will loose with the rear top spacer and with your front struts at max height compression is the up travel at each wheel.

This is desirable with 37s to keep them out if the fenders. I learned the hard way and now have damage to deal with.

 

[orion]

it is a challenge without knowing any of the spring specs from the various manufacturers. It would be nice to at least know spring rates and length. Each of the struts manufacturers probably have slightly different end collar locations so length is going to drive the preload you achieve.

the rear, unloaded, carries 2000-2300 lbs (based on trim level). Most broncos are carrying about 1100 lbs on one of the rear springs. assuming motion ratio of 1.0. Rear actual has a small motion ratio, less than 1.1 but close enough to 1.0. Eibach says their HD spring will carry an additional 250 lbs over the axle for a rear spring (500 total). So this represents about a 20% increase. For the identical length spring. So that is a 20% increase in spring rate. Kind of a big jump if you are not constantly carrying a bunch of stuff.

A bumper has some moment arm so equivalent weight needs to be calculated at axle from CG, wheel base, and bumper location. Just a rear bumper weight increase will increase rear spring reaction forces and decrease the front (unbalanced). Both front and rear bumpers will have a more balanced weight distribution. So a rear bumper weight of say 100 lbs is not apples to apples with 100 lbs weight over rear axle, as eibach specs out.

Lots of complications to get perfect springs for any particular use case with not enough info from the manufacturers. As others have said you want to get the springs correct for your ride height (use case) so that you are sitting near the middle of shock travel. That gives you usable travel in both jounce and rebound. Spring preload adjustments are just for fine tuning ride height since they will affect this equilibrium shock position at ride height.

you probably already know this. Just for others that may not be aware.

dobinsons makes some springs with different rates. Not sure about their length or if they will fit with reasonable preload.

I think I'm just going to buy their HD springs, all 4, and see how she sits. I also just looked at the OG instructions and I still have a lot of adjustments on the rear. I thought I was close to maxing it out. I think I still have an inch + to work with.

 

[CitrusBronco]

This is desirable with 37s to keep them out if the fenders. I learned the hard way and now have damage to deal with.

If you have to max out a setup to clear 37s either your tires are too big or your suspension setup is not enough.
Yes you can max it out however you’re not going to get optimal performance if it’s maxed out.
I’d suggest smaller tires or larger coilover setup.

Can I ask what setup you had and what damage you ended up with? Was it from jumping or just normal slow speed crawling when you received the damage?

 

[Tricky Mike]

If you have to max out a setup to clear 37s either your tires are too big or your suspension setup is not enough.
Yes you can max it out however you’re not going to get optimal performance if it’s maxed out.
I’d suggest smaller tires or larger coilover setup.

Can I ask what setup you had and what damage you ended up with? Was it from jumping or just normal slow speed crawling when you received the damage?

Eibach 2.0s. It was from baja style offroading which used up all the travel and the tires hit the fenders before the shocks bottomed out.

 

[CitrusBronco]

Eibach 2.0s. It was from baja style offroading which used up all the travel and the tires hit the fenders before the shocks bottomed out.

I bet that was a fun day otherwise, I love to get some speed off-road with the Bronco.
Was the damage front and rear or just the front end?

 

[Tricky Mike]

I bet that was a fun day otherwise, I love to get some speed off-road with the Bronco.
Was the damage front and rear or just the front end?

Both. The rear was just broken flare clips and cut tires. The front was pushed up fenders.

 

[CitrusBronco]

Both. The rear was just broken flare clips and cut tires. The front was pushed up fenders.

I would expect the front to take the brunt of it. Thanks for the info, I appreciate it.

 

[Tyson]

Coincidence- I’m the same loaded weight now and trying to decide what rear collar lift will help in the future. I’ll post after I measure and drive this 2000 miles, and will weight test it on the road.

Have you added your spacer lift?

The problem is that you installed and adjusted your setup for no weight (you ensured everything was level front to back). Then you added 650 lbs. Even the HD springs will sag and because most of the weight is toward the rear you’ll now have that affect.

Proper way would be to keep that factory “rake” look instead of leveling and then once you load up the rear with weight, it will now be level. Adding more height while it could work, isnt the best way to accomplish your goal.

Always setup your vehicles for your planned loads. I kept an approx 3/4” rake on my and after being loaded down with gear I’m almost level with just a touch lower in the front still. I also keep my gear in the Bronco a lot.
Also, what do you have that weighs so much? 650 lbs is on the extreme end of camping gear loads. I have 2 kids and 2 adults and don’t come close to that for 3 days excursions.

I will typically carry an RTT that is 165lb…then Fridge, power pack, recovery gear, water, gas, diesel, heater, axe, shovel, recovery gear etc etc. I thought about getting a trailer - but like the ability to travel anywhere anytime and camp - which we do several times a year. All that said. I am going to buy the “rear” spacers and put in that will add 1.5”…and adjust my shocks down. I will get it to 6 3/4 front and back when fully loaded. Then remove the RTT, battery and a few other attachments (drop 250lbs and keep roughly 400lb on board). I am suspecting that when I remove the weight my front will be 7” and rear 7.25” or 7.5”. I will report back when done and after doing some offroading

 

[B22-2023]

No changes yet, looking at all the options, maybe the rear Eibach springs but since we decided as a family to no longer load the sh** out of the Bronco for trips, it's heavy enough: looks like just focus on a little more lift all around and that looks like adjustable coilovers once and for all.

Sponsored