Jeep Enthusiast Forums banner

bumpstops, shock length, and tires size. help me iron out the fuzzy points..

218K views 388 replies 109 participants last post by  PA2KTJ 
#1 · (Edited)
and things that need a better or more explanation.

it's something I've been working on not only for a base line, but to show how bumpstops vs. shock length play an important role in a suspension system besides using them to shoe horn in a set of 33's with no lift... for those who feel they don't need the ability to run high speeds on rough terrain.

the issues come up every day.. how long do my shocks need to be? how long will fit?, what size tires fit/can fit a given height?

another edit... this chart is directed at the front shock lengths, since the front is where the rubbing issues mostly occur the rear typically needs around 1" more than the front for the same length shock.





here's some bumptop/spring tech....

Rear Springs are Rancho 2.5" RS616... unloaded length is 15.5". collapsed to coil bind they are 5",

Which means the 2.5" rear lift springs REQUIRE a minimum of 1.5" bumstop extension whith the relocated spring perches, no loss or gain in ride height was made from the relocation, I made sure to set them exact.





A stock 104 rubicon/sahara rear spring is 11 3/4" unloaded, 3 3/8" @ full coil bind...




so, add/clarify a point/measurement, contest a point.... ect.

I'm not trying to prove anything here, just showing what each system and combination can/will do.... good or bad, depending on how one looks at it..
 
See less See more
7
#2 ·
edited some, added some....
 
#5 ·
hadn't seen that before, deal is I know pretty much exactly what works and attempted to take out the vagueness and "recommendations" away like this.... (which is stated for running 35's in the link) "4" of lift is required. 6" of lift is recommended. Some rubbing may occur. A small body lift or wider fender flares may be necessary to increase clearance and prevent rubbing." that doesn't tell you that 35's need 3" bumpstops to run the 4" lift, it say's " some rubbing may occur"
the bump stops prevent damaging rub and allow the use of specific or longer travel shocks.

by pointing out the bump stop height required for a given shock length and the tires size that fits as a result of the bump stops.. for example on my chart if you pick a tire size wanting minimal lift, it tells what length bump stops are needed to keep the tires out of the fender, and the shock length that can go with the bump stop height without bottoming out the shock... regardless of lift height.

for example look at the chart for 35's. they need 3" bump stops regardless of lift height to fit stock fenders. if you want up travel that's more than stock suspension without the huge 6" lift, use a 2" lift, 1" bump stops and high line fenders with 23.75" long shocks.. is up travel not a concern? put 35's under a 2.5" lift, 2-2.5" bump stops, 24" long shocks, and a 1" body lift. no guess work and definitely doesn't "require" a 4" lift or recommend a 6"
 
#6 ·
and things that need a better or more explanation.

for those who feel they don't need the ability to run high speeds on rough terrain.
There seems to be a large amount of confusion as to what "high speed" really is. We are NOT talking race speeds here, nor are we talking above average. We are just talking about being able to keep up with the herd when we head out to a trail. What all the PRO LCG mooks keep overlooking in all of this is when you build for a specific purpose, you COMPROMISE a lot of other aspects of your rig's performance to achieve one goal.

Lack of balance is always bad, never good.

Building for what is supposedly LCG is akin to building a mall crawler. You know, the rig that looks good, has all the hooraw crap bolted to it, swing-out, Long arm lift, hi-lift, Winch with steel cable and a big *** hook that's never been scratched, beadlocks, 35" tires, and yet, hasn't been re-geared and locked up.

Everyone oohs and aahs over it, but on the trails it would suck, but hey, it looks great at the mall.

If I build a rig that can handle moderately fast traversing of the fire roads, you can bet your sweet bippy it will do everything else well also and that includes street handling.
 
#7 ·
I under stand that mrblaine,
I'm not trying to push lcg with this, just showing what combo's can work. I have the shock lengths listed with the lift height as they generally come in a fairly well balanced kit without over compression or overextension of the springs.... that's what I intended to show anyhow.

surely using 24" shock with a 2" bb is a problem...

thanks for the input.
 
#9 ·
So, I daily drive a 4" SA lift and 33's. I may some day run 34's. According to mudb8's chart, I can run 25-26" shocks. Unlimited04's super fine print above seems to suggest that the ride will be too rough if I go with this maximum length shock. Is that why rough country suggests their 23" 8304 shock? I'm just trying to get myself set straight on what length shocks I'll be happy with.
Thanks guys! Good thread!
 
#11 ·
So, I daily drive a 4" SA lift and 33's. I may some day run 34's. According to mudb8's chart, I can run 25-26" shocks. Unlimited04's super fine print above seems to suggest that the ride will be too rough if I go with this maximum length shock. Is that why rough country suggests their 23" 8304 shock? I'm just trying to get myself set straight on what length shocks I'll be happy with.
Thanks guys! Good thread!
the 23" is too short for a 4" lift.... the 4" is well served with a 15" collapsed shock length. One of these days I'll change the chart to show collapsed length instead of extended lengths since shocks are not created equally on the inside.

What's the story behind that picture?
The pic is what I used to show the importance of and how to measure and figure out the proper bumpstop lengths needed to keep the shock mounts on the axle instead of hanging from the shock when they get busted off after bottoming out the shock one to many times...

the lift in the pic above is an RC 2.5" with the RC 2.2 10" travel shock. (the original long ones)
 
#17 ·
First, to mudb8,and others that have contributed to this and many other posts, I just want to say thanks for all the info you've provided.

Also, just a heads-up for anyone running the RC 2.5" lift with the 2.2 shocks and trying to figure bumpstop extension length. If you remove the rubber bumpers from the shocks (for which I see no value}, the rear shocks compress fully into the shock body, but the front shocks do not. Fully compressed, the fronts still have 1/2" of shaft exposed. So when you measure, you need to add at least 1/2" to the amount of extension required.

For example, I have 4 1/2" of shaft exposed at ride height in the front, so I added extensions to limit it to 4" of up-travel to the cup. As it was stated before, the jounce bumper will fully compress on a hard bump at speed so you need to ignore that when measuring.

I'm sure every shock is different, so be sure to check how much actual up travel you really have. My old SJ hydros had 1/2" of shaft exposed in the rear when fully compressed.
 
#18 ·
First, to mudb8,and others that have contributed to this and many other posts, I just want to say thanks for all the info you've provided.

Also, just a heads-up for anyone running the RC 2.5" lift with the 2.2 shocks and trying to figure bumpstop extension length. If you remove the rubber bumpers from the shocks (for which I see no value}, the rear shocks compress fully into the shock body, but the front shocks do not. Fully compressed, the fronts still have 1/2" of shaft exposed. So when you measure, you need to add at least 1/2" to the amount of extension required.

For example, I have 4 1/2" of shaft exposed at ride height in the front, so I added extensions to limit it to 4" of up-travel to the cup. As it was stated before, the jounce bumper will fully compress on a hard bump at speed so you need to ignore that when measuring.

I'm sure every shock is different, so be sure to check how much actual up travel you really have. My old SJ hydros had 1/2" of shaft exposed in the rear when fully compressed.
You need to study up on shocks some more. That half inch of exposed shaft is because there is likely a 1/2" thick jounce cushion inside the shock body. ;)

Also, all quality shocks come with some cushion either internally or externally to stop a hard impact and save the shock in case you bottom them out, especially important with race style shocks that don't have isolation at the mounts.
 
#21 ·
Extending your bumpstops can be accomplished many different ways. Usually it's a spacer to go between the factory mount and bumpstop cup, held in place with a longer bolt. RC sells 2" bumpstop extensions for $14 with the bolts. I would not recomend going that long in the front as it can cause your bumpstop cup to interfere with the spring when it's at full droop.

Another way to do it is to drill and tap the center flat part of the spring perch at the bottom and bolt some kind of spacer in place. I did my fronts using a combination of 1/2" spacer on top and bolted a hockey puck to the spring perch. Some kits come with aluminum spacers to bolt in there...
 
#23 ·
Here are pics of mine

Front 1/2" spacer on top and hockey puck on bottom:



Rear 1" spacer on top and hockey puck on bottom (couldn't get a good view of the top spacer)


The top spacers in the front were made from cutting one of the RC t-case drop spacers in half and sanding on a belt sander to desired thickness. The top spacers in the rear are 1" extensions left over from the SJ BB I had previously.

The hockey pucks are drilled and counterbored and the spring perches are drilled and tapped for a 5/16" bolt,
 
#24 ·
Time for the Hockey Puck pic, Mr. Blaine!... I can't find it.
 
#25 ·
the only bumpstops that should ever be used on the front are axle mounted stops... like a 2" RE1380. the rear can use the cup extension like the RE1385 Rubicon Express... I prefer Currie's CE9122F and CE9122R, but they are more than 2x's the cost of RE Extensions.

IMO hockey pucks are a waste of Time... if the bell slams down on it, it'll crush.
 
#33 ·
I have a 2005 Jeep Rubicon Unlimited with a death wobble at 50 mph. I replaced the steering stabilizer about a month ago but it didn't help. I just replaced the stock Goodyear 245 75R 16 load rating E tires with Michelin LTX AT2 265 75R 16 load rating E. I also replaced the trackbar as the upper bushing had some play. After putting on the new tires and track bar, I noticed I had some tire rub so they put on a Daystar BB; Daystar JEEP TJ Wrangler 97-06; 1-3/4" Front & Rear Coil Spacer Kit; KJ09103BK

They also put on new Racho RS5000 shocks on both axles. After taking it for another test drive, I noticed the death wobble has been minimized but I believe the bump stops may be to long because I bottom out on highway bumps like those concrete control joints on briges and overpasses. I have 1 and 3/8" clearance between the bottom of the bump stop and the chasis... a lot less than what I had with the OEM stops. Another thing to note is that the Daystar stops are hard poly plastic; not the soft rubber of the OEM stops. So, the qestion is do I need longer shocks, re-install the OEM stops or cut the Daystay stops by an inch or....? Thanks for the advice in advance.
 
#35 ·
atxzj, whether you're right or wrong here, I've learned TONS of valuable and accurate information from mudb8's posts here on the forum. Guys like him are the reason why folks like me decided to pony up a few bucks in supporting the forum.

On the other hand, I can't honestly say that I recall seeing your name helping folks out anywhere on the board before you decided to **** in this thread.
 
#38 · (Edited)
FWIW, i'm not trying to slaughter any sacred cows here but, if the shoe fits then i guess ill be the bad guy. If the suspension geometry mud regards as his benchmark were possible, then it would be easily duplicated. So far, it is not duplicated or even backed up.

Mud, it doesn't matter what the shop you work at may have built at some point. What matters is whats on your own rig and what you're currently testing. Its like going to the security guard at microsoft to find out what windows 8 is going to be like.

Yes, the TJ suspension is old and outdated, that's why the are so many upgrades to improve it, not to mention the positive example chrysler set with the JK suspension. Why waste so much time trying to gain LT shortarm suspension? Why?

As far as helping others, I'm not a thread generator type. My mid-arm build has been used as an example on JU, JF, and pirate. When somebody PMs for advice, I answer and do my best to help. That is all.
 
#40 ·
FWIW, i'm not trying to slaughter any sacred cows here but, if the shoe fits then i guess ill be the bad guy. If the suspension geometry mud regards as his benchmark were possible, then it would be easily duplicated. So far, it is not duplicated or even backed up.
stuff I build won't "Bolt On" and I don't have the time or the money to make a production run.

Mud, it doesn't matter what the shop you work at may have built at some point. What matters is whats on your own rig and what you're currently testing. Its like going to the security guard at microsoft to find out what windows 8 is going to be like.
My rig is not a Test mule, it's an example of what nay sayer's think doesn't work. you'd be sorely embarassed to wheel with or against my "cobbled together" TJ no matter what "new" suspension system you copied when putting yours together, Others have already shut up about it.. At my TJ's suspension height and balanced travel, Mid or Long arms is only a creature comfort, not a requirement. There is a lot more to it than you can see in old pics. I also don't have a 20 min lecture with a laundry list of do's and dont's for anyone that gets the keys.. One more thing, What the shop has built, I did.

Yes, the TJ suspension is old and outdated, that's why the are so many upgrades to improve it, not to mention the positive example chrysler set with the JK suspension. Why waste so much time trying to gain LT shortarm suspension? Why?
LOL, WOW!.... the JK has almost all the stuff I modify, Longer short arms, relocated outboard lower shock mounts, longer travel shocks with longer and more balanced travel, highlined fenders, crossover steering, bigger brakes, ect. BTW, have you ever measured the rear arms of a JK? I won't spoil it for you.

As far as helping others, I'm not a thread generator type. My mid-arm build has been used as an example on JU, JF, and pirate. .
And looks to be a nice copy of a suspension you can buy online, that has shorter arms. To bad it has so many problems you tore it apart to do over.

When somebody PMs for advice, I answer and do my best to help. That is all
I bet it helps alot when you tell them to use limiting straps to keep the coils from falling out when they only have 3" uptravel that would be better "fixed" with balanced travel that can actually make use of the available travel/shock length instead of wasting it.

okay, explain it and show your pics. i'm all ears............
We've been down this road, I've explained and shown pics, sorry you missed the Class or can't wrap your head around the concept. This thread isn't the place for it.
 
This post has been deleted
This post has been deleted
#42 ·
:eek:ntopic:
hey mudb8, have you seen or played with any TJ's that have AirLift bags in the rear?

Jeep TJ Air Lift Suspension Installation Write-Up

installed mine today: http://www.jeepforum.com/forum/f9/unlimited04s-lj-build-778715/index16.html#post9320554

trying to work out how they'll behave during rear axle flex....both sides are connected, so as one compresses, the other will inflate more, but at ride height the pressure in both is equal. I played with the floor jack & drooping the axle with the shocks disconnected and they didn't do anything strange, ride in the springs nicely actually. They're supposed to replace the bumpstop extensions...but i dont feel comfortable pulling the OME bumpstop extension just yet. they almost seem to act like continuously variable airbumps....
 
#44 ·
Is it installed? If it is, and you have access to tools, i would yank the coils and start measuring. If not, put the kit on minus the coils, and compress the wheels until it rubs, turn it, back it off and take some shock and bumpstop measurements.

As said before, there are far too many variables for anyone on the net to tell you to just install X amount of bumpstop or shock and be done with it. The best thing you can do is crawl under there and start figuring out how to handle these issues now, and in the future.
 
#47 ·
the 33's with a 1.25" BL will need at least 1" bumpstop extension since they need a minimum of 2" without a BL. The BDS shocks are left to question... how long are they collapsed? They may need 2" extensions to keep them from bottoming out. I have conflicting info on BDS shock lengths.
 
#50 ·
My, what a presumptious ***. I'm not going to pretend to know you, MudB8, but I do appreciate all of the helpful information you've provided to the board so I'm just going to throw this example out there...

Did the notion ever strike you, atxzj, that the technician turning wrenches in the back of the Ferrari dealership may not make enough coin to comfortably support a family and drive the highest end, exotic, one-off custom car? Doesn't mean he can't turn a wrench and figure out a logical fix to just about any problem to occur on the finest of the rigs.

Way back when, I was pretty handy with the wrench on a 2 stroke bike and worked on some of the most wicked fast and capable race winners in the area though I never could afford to run what the more wealthy folks could. I got by on my 3 year old Honda RC250 just fine, and ignored pompous pricks with an attitude like you put forth. I enjoyed my time riding just the same, and didn't have a problem helping others learn more about going farther, faster, and more comfortably.

The point of an internet board is to help others learn. You aren't helping any of us, especially MudB8. Frankly, you're doing nothing but wasting time and space. So if he's wrong, then point out where and explain why. Your condescending attitude is disgusting. This is all I have to say to you and I won't allow you to waste any of my time further. If you're such a hardcore 4x4 guru go spend some time at Pirate and let them folks over there chew you up and spit you out a few times. In case you're too blind to notice, most of us folks here are novice to intermediate and learn a great deal from folks more advanced who are friendly enough to share information. So, if you want to keep making enemies, keep taking a dump on good folks like MudB8. Good day.
 
#51 ·
Mud,

It's time to look at my sig line. Some people are simply not worth the time. I know the quality and skill you put into your work.
 
#52 ·
can you guys help me out? im swapping my RC lift for OME coils and shocks tomorrow. i got the long travel shocks. N66L and N67L front and rear, respectively. collapsed length is 15.5" and extended is 26.5". what size bumpstops am i gonna need?

2.5" lift, 1.25BL, 33's
 
#56 ·
stock trackbars no relocation brackets. i havent have many problems in that area (yet). so should i be sending back the long travel shocks for the normal ones? i used DPG-offroad when i ordered everything.
Thats entirely up to you, I can only show you what I've run into and how I have fixed it on many TJ/LJ's around here.. Dirk and I have different opinions on the 2.5" with "L" rear shocks. I've measured and fixed the problem.

I would use N67 standard rear shocks with the OME 2.5" coils unless you intend to at least lower and outboard the lower mounts... I set em up with at least 1.25" bumpstop extensions using the n67 standard shocks. don't forget to consider what you need for the tires as well.. I prefer the longer shocks relocated but if you want the best ride possible and don't need around 3" bumpstop extension to keep the tires out of the fenders, the n67 is a bolt on and go with no harsh ride from the lack of uptravel especially loaded with gear.

I used the OME supplied 3/4" spacers on cb3's with relocation...





there is another thread "RC 2.5" shocks too long" you can look at, they are/were, the same length as the N67L's
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top