kurtfriedrich

How do you decide how much bump stop addtion you need to add when you do a lift? I see some 2" lift kits have none for the rear, and others do?

If you don't have enough, what bad thing happens?

Does it depend on the type (length) of the shock?

thanks!

04DrBlur

Only enough to keep your tires away from the fenders.

jkbandit

another thing to consider, not to exceed spring compression.

wayoflife

actually, the prevention of spring over compression (i.e. compressing it so much that it does not return to it's original height) is the only reason why you need bump stop extensions. the prevention of fender rub or shocks bottoming out are just added benefits.

regarding how tall of a bump stop extension will you need, typically, you want about as much as you just lifted your jeep. in other words, if you lift your jeep 2", you'll want 2" bumpstop extensions. now, i say 'typically' as this is just a guide to follow and not necessarily a rule and there are always exceptions to the rule

TEEJ

Yeah...it depends upon the coils....if they had room to compress w/o binding, you're good to go...if they are going to be damaged at full stuff, then you must trade away some of your articulation/uptravel to avoid damaging the coils.

As the spring rate dictates most of what that works out to, generally, if a given number of coils provides a given amount of lift...the higher spring rate coils will have more room for compression, as fewer coils are required to lift the truck to the same height.

If the coils have a higher rate due to thicker metal...vs their set due to treatment, etc...then they can have less room due to added coil thickness...

and so forth...

So - I always recommend that you measure the fully compressed limit for a new set of coils to see what you have to work with w/o damage...and, then limit compression accordingly.

When shopping for new coils, by the same token, look for the lift amount you want, with the full stuff compression length that will avoid/minimize those evil travel robbing bumpstop extensions.



Adjustable stops, such as from JKS, or trimming conventional extensions, allow you to fine tune the amount of stop extension, so that you don't just install a default "Large enough no matter what/it came with the kit" extension, that may, or may not, be the right size for YOU.

The primary advantage to keeping your uptravel articulation range as intact as possible, is that, ideally, your suspension will alllow the tires to go up and down, while the Jeep stays level.

If you prevent a tire from rising with a stop extension...the JEEP has to rise on that corner, instead of just the tire...so, it tips you up on that corner.

If a mall crawler, no biggie, you didn't need articulation anyway...

If a rock crawler, or if you are in hairier off camber situations, etc...then that extra tip up on that corner, etc....can make or break you positionally, and take away line options/stability needed to get through the terrain/flip you over, etc.



So - you NEED the extensions to avoid coil damage, but, don't use longer than needed, as it is a sacrifice that gains you nothing, and hurts performance.

Windrocker

Great explanations but I am still a bit confused So if I had an OME lift with 616 front coils and 617 rear coils would I need extensions on a 2 door with 35's ?

wayoflife

the appropriate amount of lift for the size tires you plan on running as well as shocks of the correct lenght for that particular application.

it all depends on how the coils have been designed. i would contact OME and find out from them what they would recommend.

wayoflife

are you are speaking from experience?

wayoflife

i'm sorry but did i hit a nerve or something?

look, it was just a simple question and one that i asked as it is not something that i myself have experienced. i mean, just so that we're both on the same page here, are you suggesting that a jeep with 6" of lift and 31" tires is still going to tear off it's fenders a ruin its shocks?

TEEJ

Hey - just measure the coils at full stuff ferchissakes already...that's the correct answer on the coil length/bumpstop extension needed issue, period.

Everything else is hearsay.



As for the tire clearance:

...well, some 35's are 33.5" in diameter, and some are 36" in diameter

Some 3" suspension lifts will lift YOUR jeep 3", or 2.5" or 3.5", depending upon the weights on each corner, due to how fat you/passengers are, armor, bumpers, equipment, etc.



So - Your tire size varies from nominal, and, your lift height varies from nominal...what's the "Correct" number of inches required of bumpstop?



Well, it varies proportionally...based on all of the above.

__________

Suspension lifts in general do NOT increase your tire size you can stuff...as a stuffed tire goes to where its stuffed, period.

All a suspension lift does is increase your RIDE HEIGHT...so, at the mall, the larger tires fit...but, over a bump, etc...the tires go up to where ever they would WITHOUT a lift....you just make it so they have further to go to get there...buying some slack.

To FIT larger tires that would hit the fenders on full stuff, you need to move the fenders out of the way...by removal, replacement with ones that don't intrude as much, or, a Body Lift.

1" of BL lets a 2" larger diameter tire stuff, a 2" BL lets a 4" larger diameter tire stuff, and so forth.



So, if 33's fit into your stock height jeep, a 1" BL would therefore allow 35's...and, the 2"-ish BB's are used to clear 35's, so it all works out to the same thing, except, the 1" from the BL STAYS 1", and the 2" from the SL's shrink as the tire rises.

As some 33's, esp. MT's etc...need a bit more room than stock height to clear...the 2" BL is typically a better solution, etc.



So, typically, a BL takes care of the fenders/tire stufage room, and the SL just raises the frame/ride height.

Bumpstop extensions can do the same thing, but, steal valuable uptravel...and should be minimized to maximize performance/capabilities off road...mostly limited to avoiding over compression of shocks and coils.

If you get shocks that compress to ~16", the stock stops are fine.

As for coils, again, you HAVE to measure to be sure.

A rule of thumb if no compressor is available...measure the thickness of the coils themselvses, and add them together to get a stack height (Coil stacked with the coils touching each other...).

Coils typically bow a bit too under compression, but for rule of thumb use...the straight stack will provide a slight margin of error/avoid over compression under stuffage...you can add a bit more length to the number for insurance purposes, etc, as appropriate.

After you get your stack height, just measure the stop to stop bucket clearance...and see what's left for the coils...if the stacked coil distance is longer than the bucket distance made by the stops, the extra distance is all you need an extension to span for you.



That's it really.