Lets talk about Axle travel and bump stops

ponykilr

ponykilr

Old Crow
Joined
Apr 26, 2021
Location
Lowgap
I have read a good bit about this and like most things the opinions run the gamut.

What is the best ratio of up:down travel? I have read 50:50 is ideal while some say more droop is better. Obviously up is limited by fenders, tires, shocks and such. Down by springs unseating, shock length, ect.

What is the best way to determine how much bump extension you need? Cycling the suspension to measure what ideal would be? Wheel turned as well as straight?

My bumps are factory, 3” springs and a 3/4” spacer. I have about 6.5” tire to fender at ride height. I have a little over 6” from pad to jounce bumper at ride height so I need extensions obviously.

I just need some insight on measuring.
 
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ponykilr said:
I have read a good bit about this and like most things the opinions run the gamut.

What is the best ratio of up:down travel? I have read 50:50 is ideal while some say more droop is better. Obviously up is limited by fenders, tires, shocks and such. Down by springs unseating, shock length, ect.

What is the best way to determine how much bump extension you need? Cycling the suspension to measure what ideal would be? Wheel turned as well as straight?

My bumps are factory, 3” springs and a 3/4” spacer. I have about 6.5” tire to fender at ride height. I have a little over 6” from pad to bump stop at ride height so I need extensions obviously.

I can order 2” or 3” pucks to drop them down, just need some insight on measuring.
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This the 04 TJ in your signature? For the front,, just get a bag of hockey pucks and add them to the bottom of the spring pad until you get it where you need it.

On the rear, I have the 2" drop spacer for 2" springs and 3/4" spacer. You'll probably want the 3".
 
ponykilr said:
I have read a good bit about this and like most things the opinions run the gamut.

What is the best ratio of up:down travel? I have read 50:50 is ideal while some say more droop is better. Obviously up is limited by fenders, tires, shocks and such. Down by springs unseating, shock length, ect.

What is the best way to determine how much bump extension you need? Cycling the suspension to measure what ideal would be? Wheel turned as well as straight?

My bumps are factory, 3” springs and a 3/4” spacer. I have about 6.5” tire to fender at ride height. I have a little over 6” from pad to bump stop at ride height so I need extensions obviously.

I can order 2” or 3” pucks to drop them down, just need some insight on measuring.
Click to expand...
Best way to measure how much bump stop you need is to pull your springs out to replicate full compression and measure. Do this with the tires on.

As for the amount of up and down travel. It is personal preference. I prefer more down travel than up travel. This helps to keep the center of gravity low.


X2 on hockey pucks in the front.
 
Yeah, remove the springs and cycle. Stuff is probably limited by tire/fender contact or maybe shocks. Down travel might be limited by shocks. If not that, it's steering or track bar. If it droops better on the driver side than passenger, it's almost definitely limited by the steering. Unhook the drag link, droop it out and try to reconnect the drag link. May have to strap it or swap to heims and misalignment bushings.
 
Also brake lines are not limiting straps.
Going off of what shanw said if your track bar or drag link is your limiting factor you will burn through bushings on them. I know this because my trackbar was my limitation for awhile and I destroyed bushings constantly.
 
I have a heim style front track bar but steering is factory.

So, remove springs and at least one link and cycle axle all the way up. If shocks fully compress before tires stuff (doubt they will) then base bumps off of keeping shock from bottoming.

If shock is cool then base bumps off of tire to fender happiness.

If steering or track bar have interference …. New parts or bump to keep them happy til new parts.

Full bump is cup to pad with axle raised evenly, right? And full flex is one side drooped and the other raised?

Both full bump and full flex should be check with regards to tire clearance because tire will be in different locations, correct?

Rear will likely need more than the front as a rule, correct?
 
CasterTroy said:
That's what shocks are for 😎

"See how these broncos WORK........"

🤣
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Or having nothing to limit your suspension. Then the guy behind you asks if anyone had lost a spring spacer and all of the sudden you have a ton of spring noise. But atleast I got a good poser picture and cool hi tech limit strap lol.
20200528_163809.jpg
20200514_181009.jpg
 
ponykilr said:
I have a heim style front track bar but steering is factory.

So, remove springs and at least one link and cycle axle all the way up. If shocks fully compress before tires stuff (doubt they will) then base bumps off of keeping shock from bottoming.

If shock is cool then base bumps off of tire to fender happiness.

If steering or track bar have interference …. New parts or bump to keep them happy til new parts.

Full bump is cup to pad with axle raised evenly, right? And full flex is one side drooped and the other raised?

Both full bump and full flex should be check with regards to tire clearance because tire will be in different locations, correct?

Rear will likely need more than the front as a rule, correct?
Click to expand...
What do you mean by remove one link?

What I would do and what I ended up doing was. Pulling both front springs and letting my fenders rest on my tires. In your case it might be your shocks. Then measure the gap that is between your bump stop and bump stop pad. I added 1 inch to my measurement to account for flexing and it was dead on for my setup. This method works front and rear. It takes time but is worth it for figuring out bump stops and shocks.

The reason why you need to consider full flex because you tire will be angled in at full flex. Depending on your set up that might not matter. Once you get your bump stops find a place to fully flex and check clearances.

For figuring out what is enough droop is debatable. Personally I run the theory that your spring should just have a little bit of weight left on it. To figure this out find a way to fully flex out and if you unseat a spring back up till its seated and measure the distance from where you want to mount some type of limiting device.
 
ponykilr said:
remove springs and at least one link and cycle axle all the way up.
Click to expand...
No need to disconnect any suspension links. Stock TJ short arms do not limit suspension travel. Disconnect the drag link and droop out the passenger side to see if you're exceeding the tie rod's max angle. The type of joint on the track bar doesn't matter specifically - what matters is how much angle it's capable of doing.
 
@Keith1138 @shawn I meant disconnect one sway link when testing flex for tire clearance.

OK, as soon as I can I will remove the springs and see what I see.
 
ponykilr said:
I have read a good bit about this and like most things the opinions run the gamut.

What is the best ratio of up:down travel? I have read 50:50 is ideal while some say more droop is better. Obviously up is limited by fenders, tires, shocks and such. Down by springs unseating, shock length, ect.

What is the best way to determine how much bump extension you need? Cycling the suspension to measure what ideal would be? Wheel turned as well as straight?

My bumps are factory, 3” springs and a 3/4” spacer. I have about 6.5” tire to fender at ride height. I have a little over 6” from pad to jounce bumper at ride height so I need extensions obviously.

I just need some insight on measuring.
Click to expand...
The ratio of compress to droop depends on your driving terrain. For rock crawling with my LJ, I'm mounting Fox 14" Coilovers with 4" of up travel, and the remaining dedicated to droop (39.5 iRoks). This worked extremely well on my buggy with Rockwells and 49" iRoks. If you are doing desert racing I'm sure you would want to increase up travel significantly.
 
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