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-   -   correct bumpstop length (http://www.wranglerforum.com/f210/correct-bumpstop-length-70047.html)

bobjenkins 11-24-2010 07:17 PM

correct bumpstop length
 
Okay iv been thinking alot about going to 35īs but Im going to stay with 33īs and instead get a tummy tuck with a 1.25 body lift and mml

Okay guys lt me see if Iv got this right. to test how much bumpstop I need for my 3 inch lift and 33 inch tires this is how I should do it.

get some spring compressors, remove the springs on one tire then jack up that side of the axle until the bumpstop hits, and see how much clearance Ive got on the wheel well. If there is alot of clearance then I can shorten the bumpstop

Thanks for any info. Im trying to figure this out for the fronts right now. If I can trim fenders/add 1.25 body lift/remove bumpstops to get more flex I would like to.

Heres what im dealing with now. 3 in lift 33 in tires, and a bumstop entender of 2.5 inches on the fronts.

thanks

edit also aparently it looks like the track bar(?) is going to be very close to the front diff .. not sure how to remedy this

MikalCarbine 11-24-2010 07:48 PM

You have the right idea, you will be limited by your shock length also. What lift do you have? The length of the shock will play a key role with bumpstop length elsewise you will bottom out the shock and break it. The trackbars is a whole different issue. Wait for UnlimitedLJ04 to chime in on this, he's a legit pro in the area

bobjenkins 11-24-2010 08:19 PM

Quote:

Originally Posted by MikalCarbine
You have the right idea, you will be limited by your shock length also. What lift do you have? The length of the shock will play a key role with bumpstop length elsewise you will bottom out the shock and break it. The trackbars is a whole different issue. Wait for UnlimitedLJ04 to chime in on this, he's a legit pro in the area

Thanks for the response. I'm not sure what lift kit I have the previous owner had it installed at desert rat. The only part I can think to look at to identify it are the shocks. They are white and say explorer on them. Is there another way to tell?

UnlimitedLJ04 11-25-2010 10:14 AM

Quote:

Originally Posted by bobjenkins (Post 892849)
Okay iv been thinking alot about going to 35īs but Im going to stay with 33īs and instead get a tummy tuck with a 1.25 body lift and mml

It works well :punk: Do you have an SYE? A tummy tuck adds whatever clearance increase to the overall lift height seen by the t-case.

Total Lift seen by T-case = Suspension Lift Height + T-case lift height

The common question is "Can you subtract 1" off for the MML?" Meh, the answer is maybe...you'll need to test your jeep and see. With a TT, the answer is usually no.

Quote:

Originally Posted by bobjenkins (Post 892849)
Okay guys lt me see if Iv got this right. to test how much bumpstop I need for my 3 inch lift and 33 inch tires this is how I should do it.

get some spring compressors, remove the springs on one tire then jack up that side of the axle until the bumpstop hits, and see how much clearance Ive got on the wheel well. If there is alot of clearance then I can shorten the bumpstop

Kinda - you want to do both sides at the same time. It would help to take the flares off, because you don't care about them for clearance...they're plastic, they move and are easily modified. What matters is the fender & tub itself.

So do the front or the rear seperately. Keep in mind you need a floor jack that can travel at least 10-12" (that was a big issue for me for a while) you can crib the rest with wood blocks. you'll also need four 6-ton jackstands, and two 2/3-ton'ers would help, but not required.

1. Remove the shocks - fully compress them and measure the length from eye to eye, or base of the stud to eye.
2. pull the springs from both sides.
3. Now set the shocks back in, connecting them at the top, disconnected at the bottom.
4. You should have unhooked the axle side of the track bar to pull the springs, but here you can leave it unhooked. We'll be playing the interference game (with your stock bar you won't have any problems)
5. Pull the jounce bumper out (rubber bumpstop thing inside the cup)
6. Now jack the axle up (or lower the frame) SLOWLY.
7. You should get something that looks like this:
http://i268.photobucket.com/albums/j...PICT0070-1.jpg
8. Watch for the shocks bottoming out...in other words the Jeep starts lifting, or you start compressing the bushing at the top of the shocks. You should measure your shocks fully compressed length before hand so you know what you're dealing with. 13.5" shocks will fit inside the stock compression location, 14.5" will require 1" bumpstop extension, 15.5" will require 2", and so forth.
8. Now once you get the bumpstop cup setting on the axle pad, slide a tire on if you can. Make sure you've supported the axle with jack stands for safety here. You can hold the tire on by hand, or use two lug nuts hand threaded on. You'll notice very soon if you'll clear or not. This is where removing the flares is helpful.
9. If you couldn't get the bumpstop cup down all the way because the shocks were too long, then you need to measure the distance from the bumpstop cup to the spring pad, as you just back off the shocks about 1/4". Thats how much bumpstop extension you need FOR SHOCKS ONLY.
10. If you don't clear the tire fit test, measure from the hub center to the sheet metal in a vertical fashion (you'll need to eye ball this a bit because the axle is a bit wider than the tub).
11. Now, move the axle down until you can fit the tire size you want. When you can just barely slide the tire on, and clear the steel fender lip, measure the distance to the bumpstop cup and the spring pad. Thats the minimum bumpstop extension you need FOR TIRES.
12. Now while you're doing all this you need to keep checking for track bar interferences. Will the track bar hit the diff cover? Will the track bar hit the tie-rod? Since its disconnected, its an easy check by lifting it up and position it in the mounting location. You can slide a bolt in if you like, or just hold it there by hand and check, or even zip tie or duct tape it. While you're moving the axle, the distance between the mounting points is changing, so don't freak out if you can't get the bolt in.

Typically you want the bumpstop needed for SHOCKS ONLY to determine your TIRE requirement. Then you basically get the longest travel use out of your shocks. Generally speaking, its better to get more shock travel, aka more uptravel and downtravel, and run smaller tires than it is to run those same shocks and lots of bumpstop in order to run larger tires. With the latter idea, you're limiting your uptravel...kinda like your bumpstop pics above.

I give you a general idea of what you're looking for with 33" tires and 3" lift.
- Based on TIRE SIZE ONLY - the require bumpstop will be about 2-2.5" without a BL. With a BL, that will be 1-1.5".
- Based on SHOCK LENGTH ONLY - a collapsed length of 15.5" will require 2" bumpstop, 14.5" will be 1", and 13.5" will be no addition bumpstop extension.
- everything i've said has been for the front. for the rear, the general rule of thumb is to add 1" to the bumpstop extension you determined in the front. thats a good starting point as a guide.
- when testing the rear axle, make sure to mount the tire up at full compression - look for clearance issues in the BACK of the fenderwell. 35s will rub on stock length control arms, 33's may too, or they may be stupid close.
- Don't throw the giant 2.5" bumpstops you have away. Find out how much you need based on what i've listed, then cut it down if you need less. Slap it in a vice and use a wood saw/band saw to cut it down. Save the scrap piece and use it later if you need additional bumpstop. Or use it as a bumpstop extension for the rear if its thick enough.

for the front:
http://i133.photobucket.com/albums/q...springtech.jpg

this is a budget boost for the rear, but the bumpstop extension shows where the spring compresses:
http://i133.photobucket.com/albums/q...Tech/RE-04.jpg

Bumpstop extensions for the front should always go on the axle pad, extensions for the rear should always go on top. See your last thread about 35s on 3" of lift for more info...I think I outlined a bunch there.

Quote:

Originally Posted by bobjenkins (Post 892849)
Thanks for any info. Im trying to figure this out for the fronts right now. If I can trim fenders/add 1.25 body lift/remove bumpstops to get more flex I would like to.

One of the nice benefits of a 1" BL is it means you need 1" less bumpstop to fit the same tire size that would require 2".:wavey:

With regard to the front track bar. If the axle isn't centered at ride height, you'll want to drill a hole in the mount to reuse the stock bar. But you'll need to weld some reinforcement to the mount.

http://im1.shutterfly.com/media/47a0...D550/ry%3D400/
http://im1.shutterfly.com/media/47a0...D550/ry%3D400/
http://im1.shutterfly.com/media/47a0...D550/ry%3D400/

UnlimitedLJ04 11-25-2010 10:33 AM

and for reference:
http://i133.photobucket.com/albums/q...ech/spring.jpg

MikalCarbine 11-25-2010 10:45 AM

Great info right there, can't wait to order my lift sometime in December

bobjenkins 11-25-2010 12:05 PM

Yes great info! Ill being working on this on Friday when I can get spring compressors

Also about the sye good info I was thinking I who'd need one with a tummy tuck and you confirmed it!

bobjenkins 11-25-2010 03:20 PM

Quote:

Originally Posted by bobjenkins
Yes great info! Ill being working on this on Friday when I can get spring compressors

Also about the sye good info I was thinking I who'd need one with a tummy tuck and you confirmed it!

Ok I measured the spring. Compressed 14.5 . Extended 24 .25

Are these springs recommended for 3 inch lift?

UnlimitedLJ04 11-25-2010 03:47 PM

Quote:

Originally Posted by bobjenkins (Post 893988)
Ok I measured the spring. Compressed 14.5 . Extended 24 .25

Are these springs recommended for 3 inch lift?

you mean shocks?

if thats the front shocks, yes you're fine. 1" bumpstops min for shocks only. so with a 1" BL + ~1-1.5" bumpstop extension, you'll fit 33s very nicely, and have lots of droop.

add a TT, and the belly clearance + SYE and you can get the belly clearance around 16" +/- 1" depending on your final setup.

bobjenkins 11-25-2010 04:23 PM

Quote:

Originally Posted by UnlimitedLJ04
you mean shocks?

if thats the front shocks, yes you're fine. 1" bumpstops min for shocks only. so with a 1" BL + ~1-1.5" bumpstop extension, you'll fit 33s very nicely, and have lots of droop.

add a TT, and the belly clearance + SYE and you can get the belly clearance around 16" +/- 1" depending on your final setup.

Yes thanks. The shocks fully compressed. The jouncer is not compressed much at all so youre right.Sounds like 1 in bumpstops are perfect

Now I'm moving to the back. I'm planning a 1.25 inch body lift and mml with the tummy tuck and sye. Here's a pic with my fender off

bobjenkins 11-25-2010 04:27 PM

Quote:

Originally Posted by bobjenkins

Yes thanks. The shocks fully compressed. The jouncer is not compressed much at all so youre right.Sounds like 1 in bumpstops are perfect

Now I'm moving to the back. I'm planning a 1.25 inch body lift and mml with the tummy tuck and sye. Here's a pic with my fender off

Pic. As it looks not with the body lift I wont have to trim fenders

UnlimitedLJ04 11-25-2010 08:11 PM

is that 33's with the springs removed & the bumpstop cup resting on the axle pad (well, or the 2.5" bump extensions)?

bobjenkins 11-25-2010 09:24 PM

Quote:

Originally Posted by UnlimitedLJ04
is that 33's with the springs removed & the bumpstop cup resting on the axle pad (well, or the 2.5" bump extensions)?

Yes spring removed and the top jouncer resting on the axle pad. (Bumpstopextender 2.5" was removed) the jouncer was still on there. I compressed it until the shock was fully compressed , that was bottoming out so cut the bumpstop extender and now its 1"

UnlimitedLJ04 11-26-2010 05:42 AM

Quote:

Originally Posted by bobjenkins (Post 894384)
Yes spring removed and the top jouncer resting on the axle pad. (Bumpstopextender 2.5" was removed) the jouncer was still on there. I compressed it until the shock was fully compressed , that was bottoming out so cut the bumpstop extender and now its 1"

looks good. the clearance will probably be a little less than you see there once you flex the axle as the tire stuffs in the wheelwell. you're definitely on the right track:punk:

UnlimitedLJ04 03-03-2011 05:45 PM

here's some visual adds to help the above descriptions

Most think to check the axle under flex, and think if everything is ok there it must work...but this simply isn't the case. Flex is good for testing tire clearance, but you also need to check full bump with the springs removed.

Drivers side bumpstop stuffed, shocks disconnected:
http://i133.photobucket.com/albums/q...0/DSC01947.jpg
That is 1-3/8" bumpstop extension. The 1" is provided by a Performance Accessories body lift puck ("Big Block"), which costs about $2 directly from their website.

Flexed, with the passenger side drooped:
http://i133.photobucket.com/albums/q...0/DSC01948.jpg
You can see the track bar clears most of the diff cover well.Not even close to the "SOLI" lettering, right?

Now lets look at full bump:

http://i133.photobucket.com/albums/q...0/DSC01950.jpg

^if you can't get to this point, with the bumpstop cup fully resting on the spring pad, you need to adjust your bumpstops. Shock length is too long, or there is some suspension interferences occuring. These need to be eliminated to achieve uptravel.

Track bar lands in front of diff cover significantly more here:
http://i133.photobucket.com/albums/q...0/DSC01949.jpg
http://i133.photobucket.com/albums/q...0/DSC01952.jpg
http://i133.photobucket.com/albums/q...0/DSC01953.jpg
This demonstrates the track bar clearing the tie-rod & modified diff cover with 1-3/8" bumpstop.

The modifications to the diff cover were:
http://i133.photobucket.com/albums/q...r/DSC_0446.jpg

Now lets install the tires and see what it looks like:

Full bump with the springs removed, and 33's:
http://i133.photobucket.com/albums/q...0/DSC01954.jpg

http://i133.photobucket.com/albums/q...0/DSC01955.jpg

Under full flex the tires fit in the fenderwell, but its close
http://i133.photobucket.com/albums/q...0/DSC_0087.jpg
^this is now the time to turn the steering wheel left to right, lock to lock, and look for other interferences, such as the tires rubbing the sway bar or frame, the brake lines getting caught..etc.

You should also drop the axle to full droop, and turn the steering lock to lock to check brake line length. If the brake lines become tight, you'll need extended brake lines. You can use a string to help determine the proper measurement.

jeepjones 03-06-2011 11:39 AM

Quote:

Originally Posted by bobjenkins (Post 892923)
Thanks for the response. I'm not sure what lift kit I have the previous owner had it installed at desert rat. The only part I can think to look at to identify it are the shocks. They are white and say explorer on them. Is there another way to tell?

The shocks/lift is Pro-Comp as in Pro-Comp Explorer shocks.

GoldenSahara00 07-07-2011 05:48 PM

Hey guys, I added a BL now, and was wondering if you could help me determine if I can reduce or remove my bump stop extensions. I read through this and several other threads, but I just need a little more info about the shock length and all that. I was honestly a bit confused.

UnlimitedLJ04 07-08-2011 08:56 AM

Quote:

Originally Posted by GoldenSahara00 (Post 1360755)
Hey guys, I added a BL now, and was wondering if you could help me determine if I can reduce or remove my bump stop extensions. I read through this and several other threads, but I just need a little more info about the shock length and all that. I was honestly a bit confused.

For reference:
In front: 13.5" compressed length shocks fit with no bumpstop extension
In Rear: 12.25" compressed length shocks fit with no bumpstop extension

Regardless of lift height - Subtract the compressed length of the new shocks you're trying to fit and you've got a good starting point for the required bumpstop extension.

Example: 15.5" compressed length shock (like OME N66L) = 15.5-13.5 = 2" front bumpstop requirement.

The body lift benefit in regard to bumpstop extension length is that you can run less bumpstop for TIRE SIZE. You still need the same bumpstop extension based on shocks.

Bumpstop extensions are required for four main reasons:
1. Prevent major suspension interferences - like axle housing hitting the oil pan, or track bar hitting a diff cover.
2. Preventing coil bind - prevents damage to springs.
3. Prevent shock damage - prevents shocks from bottoming out.
4. Prevent tire vs steel tub rubbing - prevents damage to the body and tire damage.

Tires are the last on the list because thats the least important job.

If you add a 1" BL, you can fit 1" larger tires, provided #1-3 are already satisfied.

Example:
You have 2.5" of lift and have 14.5" compressed length shocks in front using the stock track bar, with 13.5" compressed length shocks in the rear using a track bar relocation bracket. Notice I've said nothing about tire size.

Now, following the above #1-4 list:
1. You don't need any bumpstops in front to clear the stock track bar, but in the rear you need 1.25"-1.5" bumpstop extension to prevent the relocation bracket from hitting the underside of the tub.
2. The front springs are under 20" in extended length, which means they'll fit in the stock spring towers. You'll need some bumpstop extension in the rear since the springs are longer, and the 1.25"-1.5" from #1 should suffice well.
3. The front 14.5" compressed length shocks require at least 1" of front bumpstop extension. The rear 13.5" compressed length shocks require 1.25-1.5" of rear bumpstop extension, which fits well with #1 & #2.
4. Now you know you need 1" front, and 1.25-1.5" rear. You can run a max of 32" tires on this setup. If you add a 1" BL, you can run a max of 33" tires. If you add a 3" BL, you can run a max of 35" tires.

Got it?

GoldenSahara00 07-08-2011 09:20 AM

Yes, thanks that was a great outline! So basically, the body lift doesnt really affect BS extension because there are other things that it is there to protect. If I lessen all of those, I can lessed extension.

Thanks again!

UnlimitedLJ04 07-08-2011 10:42 AM

Quote:

Originally Posted by GoldenSahara00 (Post 1362278)
Yes, thanks that was a great outline! So basically, the body lift doesnt really affect BS extension because there are other things that it is there to protect. If I lessen all of those, I can lessed extension.

Thanks again!

a body lift doesn't affect bumpstop extensions because the shocks mount to the frame, not the body.

the only way a BL effects bumpstop extension is if you're running too large a tire on too low a lift. that would give you shorter compressed length shocks, but then #4 becomes the overriding requirement for bumpstop extension - you don't want to damage the tires/tub, so you need to add more bumpstop extension in than is required for #1-3. Only then will a BL constitute a reduction in bumpstop extension length.

an example of that can be seen in the ill-educated "Low Center of Gravity" crowd. Some think you can run 37s on 2.5" of lift if you just push the bumpstops way out....which kills all your uptravel. problem is you need uptravel, and running less uptravel than stock (around 4") is plain stupid.

thats why you see my posts harping on whats required to actually gain uptravel with a 2.5" lift when you start mixing and matching aftermarket parts, especially track bars and diff covers. In front you end up hitting the track bar into the diff cover or the tie-rod, and in the rear you end up hitting the diff cover into the gas tank or causing rear track bar binding issues.

thats also why most educated folks recommend 4" of lift for 33s. Most smart 4" lift companies use 15.5" compressed length front shocks and ~14.5" compressed length rear shocks, with 9-10" of total travel. That means you need 2" of front bumpstop extension and 2.5" of rear bumpstop extension.

Remember I said above thats the minimum you need to run 33's without a BL?

Well thats why 4" of lift and 33's is the most common recommendation - you gain 2" of uptravel, a good amount of downtravel and plenty of room for 33s.

If you don't have the right bumpstop extensions you end up blowing up the shocks, or ripping the shock mounts off the axle. If you're not bashing something else together first. YJ's that don't run front bumpstop extensions actually push the front axle housing into the oil pan. On TJ's, shock mount damage is most common in the rear, the fronts are beefy enough you usually only see blown shocks or broken bar pins. So next time you see a post where somebody says their shocks are blown/leaking, the bar pins are toasted or the bushings are shot, or they ripped the shock mount off the axle - you know right away the bumpstops are most likely not set right.

Similarly, based on criteria #2 (coil bind), next time somebody says they want to put a 1.75-2" spacer on the front of their Jeep because after they added a 120lb bumper and 80lb winch, their soft RC springs are sagging too much....remember the stock springs just barely fit with a 2" BB...so what do you think will happen at full compression when a spring thats 3-4" longer than stock is compressed? Yup, major coil bind and spring damage. Thats why smart companies that sell BB's, give you a bumpstop extension the same length as the spacer lift height - to prevent coil damage. This is most critical in the rear since the spring compression space is quite short already.

Make sense?

IndyJeepMan 07-08-2011 10:59 AM

This is a good write up.

Also, clearance can be had from other things such as body modifications, but beware once you cut once there is no going back! I've become a skilled cutter since I've got this Jeep! :)

GoldenSahara00 07-08-2011 01:08 PM

I am gona finish readed through, but what I meant was, my tires hit before, but with my BL I have more room for uptravel. I was contemplating how much I can reduce my bump stops to take advantage of that additional room. not that the springs/shocks moved. :)

GoldenSahara00 07-08-2011 01:15 PM

Yes, I do and understood most of that before hand to a degree but you made it slightly more clear ;)

and yes indy, but that clearance is only useable if you arent hitting stuff or binding coils or blowing shocks.

Unlimited, I am running the 3 inch zone lift with 33s. so I was hitting into tub, aka the #4, because of tires too large for lift. I had .75 spacers up front, which helped some. mostly for leveling. I added the BL so I dont hit my fenders or anything anymore. But I believe I will still have some extra useable room. So I am trying to figure how this all plays out. I have had no issues with my set up, I think it is better off left alone. also I believe that my zone lift didnt come with rear bump stop extensions but I may just be forgeting when I installed them.

can I look up zones shock compressed size online and compare?

UnlimitedLJ04 07-08-2011 02:04 PM

Quote:

Originally Posted by GoldenSahara00 (Post 1362877)
can I look up zones shock compressed size online and compare?

You can always call Zone. They're in Michigan, but I doubt they will bite. :hide:

GoldenSahara00 07-08-2011 02:13 PM

I'm sure someone has it on the Wx3(world wide web) lol. honestly I am not gona worry about it til I know if I need more flex and how it all works etc. I just wanted to personally understand it better.

UnlimitedLJ04 07-08-2011 03:51 PM

Quote:

Originally Posted by GoldenSahara00 (Post 1363067)
I'm sure someone has it on the Wx3(world wide web) lol. honestly I am not gona worry about it til I know if I need more flex and how it all works etc. I just wanted to personally understand it better.

people seem to think bumpstops are only for off-road or something. they're definitely not. they're required on the street too...thats why people destory shocks and shock mounts...repeated pounding. every time you hit a pothole, dip, speed bump, carry passengers or cargo in the back, etc you're using the bumpstops.

GoldenSahara00 07-08-2011 03:59 PM

Not if you drive gentle like I do all of the time... never!


HAHAHAHA ;)


I just meant I want to get the most flex out of my rig (uptravel) as possible without damaging anything. I know I use my bumps alot :)

UnlimitedLJ04 07-08-2011 04:18 PM

Quote:

Originally Posted by GoldenSahara00 (Post 1363410)
I just meant I want to get the most flex out of my rig (uptravel) as possible without damaging anything. I know I use my bumps alot :)

while uptravel is important, its only about 50% of flex. downtravel is the other 50%.:rofl:

GoldenSahara00 07-08-2011 04:38 PM

You major in mathematics or something? :D

bumpstops dont limit your downtravel though.

jp2611 03-15-2012 08:30 PM

scribed for when i get disco's


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