Bilstein 5100 vs 5125 rear shocks? - Jeep Commander Forums: Jeep Commander Forum
Suspension / Lifts This is the place to discuss the suspension, lift systems, and other stuff underneath your Jeep Commander

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post #1 of 16 (permalink) Old 04-10-2015, 06:48 PM Thread Starter
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Bilstein 5100 vs 5125 rear shocks?

I searched the threads but didn't find a topic that specifically discusses using Bilstein 5100 vs 5125 shocks on the rear end of the XK ...so I decided to start a discussion.

I know the 5100 series is popular for both front struts and rear shocks. The front struts are part #24-225793. They lift between 3/4" and 2", depending on how you position the snap ring.

The rear shocks are part #33-225807. They will give you a lift between 0-1.5" but unlike the front, they don't have a snap ring adjustment so you cant actually adjust them. From my understanding, they are simply a little longer then "oem" shocks, hence the boost ...anywhere from nothing up to maybe 1.5" max. So there's a certain limit as to what your going to get out of these, and need to think about that, when piecing stuff together.

Marketed "for custom lifted applications", the 5125 series rear is the next option for those of us who wish to raise the back end up with OME coils plus an additional 2" spacer (like a Daystar) or perhaps 4" SL coils, or JBA 4" coils.

I'm thinking in these kinda rear set-ups I just mentioned (when you don't go full Superlift)...the 5125 series shocks come into play. I read about guys having to shim them on either sides with washers to remove some of the play. That's not such a big deal. However, there are a bunch of different 5125 series shocks listed by lengths, compressed length, extended length, total travel, etc.
Here's one spot I found a chart listing the various sizes available, not by specific application. I'm not endorsing anyone, just that they have a good chart as you scroll down the page.

http://www.shockwarehouse.com/site/bilstein_5125.cfm

Have any of you used the 5125 series? If so, maybe you could indicate which part number you used and what height lift coils you have in the rear, that you matched it up to.

For example, if you did a 3" lift ... vs. a 3.5" lift, would you use the same part number ? If you have almost 4" lift what number is best to use? I'm guessing it wont be the same 5125's as if you had a 2.75" rear lift.

I think some of us might benefit from seeing what others have done using 5125's with successful results.
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Last edited by BBCBIRD; 04-10-2015 at 06:52 PM.
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post #2 of 16 (permalink) Old 04-13-2015, 02:12 PM
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Rear shocks do not lift in anyway, they do pose a limitation to droop in the rear if you do not get longer than stock shocks when you lift however.

Since the 1.5" lift shocks are 15.4" compressed and 24.75" extended I would be looking @ something like these two: http://www.shockwarehouse.com/site/product.cfm?id=15117 http://www.shockwarehouse.com/site/product.cfm?id=15118 for a 4" lift, depending on valving. Probably want to extend your bumpstops for that.

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post #3 of 16 (permalink) Old 04-13-2015, 03:35 PM
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Well, there are specialty shocks that include coil over springs that might lift a bit, even a few that pump themselves up to add spring pressure to even loads, etc, that doesn't change what luckyse7ens is saying.

The purpose of the shock is to just "Damp" the spring force so you don't bounce up and down endlessly on the springs.

Yes, most shocks today have nitrogen gas charges in them. The purpose of the gas pressure is to prevent foaming of the oil in the shock as its forced through the valves in the shock, i.e. give you better shock performance. Sure, that gas charge will cause the shock to extend, but the amount of spring force created by the nitrogen charge is so tiny compared to the springs themselves it makes no difference, especially in ride height, its just there to combat the oil foaming.

The shock length extended/retracted is for the travel in suspension. It also depends on the suspension and how you lift it, how much additional travel you get and if a different length shock will get you anything.

The Commander has a live axle in the rear, what limits it extending downward as far as it can go, droop as luckyse7ens called it, is the shock. So if you want more suspension travel and a good lift kit on a live axle can give it to you, a longer shock is needed. The stock shock length will just let if only extend as far as stock, which is now less than stock if you raised the ride height.

Keep in mind, the suspension has to bottom out on a bump stop before the shock bottoms out. If you get a shock that is too long and it will bottom out before the suspension hits the bump stop, you'll damage the shock and blow it.

The front strut/shock uses a big honking urethane stop over the top of the strut as a bump stop, so the strut doesn't bottom out before the suspension and damage it.


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post #4 of 16 (permalink) Old 04-13-2015, 05:58 PM Thread Starter
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Thanks for the two replies. I understand the basics of the rear shocks functions, but I appreciate the good explanations.

I wasn't aware of needing to extend the rear bump stops if going with 4" of lift in the back. So much stuff to learn.

I'm hoping someone here has added 3-4" in the rear and actually used a set of 5125's.
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post #5 of 16 (permalink) Old 04-13-2015, 06:59 PM
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Quote:
Originally Posted by BBCBIRD View Post
Thanks for the two replies. I understand the basics of the rear shocks functions, but I appreciate the good explanations.

I wasn't aware of needing to extend the rear bump stops if going with 4" of lift in the back. So much stuff to learn.

I'm hoping someone here has added 3-4" in the rear and actually used a set of 5125's.
Doesn't the superlift kit come with rear shocks? I wonder what the specs on those are.

Quote:
The kit is packaged complete with rear Superlift Superide or Superide SS shocks by Bilstein.
Super lift rear shocks P/N 88200 are 28" @ full extension. http://www.jegs.com/i/Superlift-Susp...88200/10002/-1

and 16.5" collapsed.

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post #6 of 16 (permalink) Old 04-13-2015, 07:23 PM Thread Starter
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Thanks for finding that for a reference. Interesting that a pair runs less then $98 shipped. At less then $50 a piece shipped, I wonder how they would be?

They are only listed as fitting the 2005-2006 WK and only the 2006 XK.

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post #7 of 16 (permalink) Old 04-13-2015, 07:31 PM
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Quote:
Originally Posted by BBCBIRD View Post
Thanks for finding that for a reference. Interesting that a pair runs less then $98 shipped. At less then $50 a piece shipped, I wonder how they would be?
Those look like dual tube shocks. Probably Monroe Sensatrak type quality. I'd personally rather find some monotube shocks.

Omelet (on Jeep Forum .com) "upgraded" from OME shocks to Superlift shocks and felt he was underdamped. He upgraded to Fox 2.0 reservoir shocks shortly after.

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post #8 of 16 (permalink) Old 04-14-2015, 09:47 AM
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Quote:
Originally Posted by BBCBIRD View Post
...I wasn't aware of needing to extend the rear bump stops if going with 4" of lift in the back. So much stuff to learn.

I'm hoping someone here has added 3-4" in the rear and actually used a set of 5125's.
You may NOT need to extend the rear bump stops, is all depends on the design of the lift kit.

There are several limits of the suspension travel;

Geometry: the links and suspension itself, it has to be stopped before the suspension pieces hit the frame with enough force to damage the parts. The links will only allow the suspension to extend so far, and there are many suspension designs where the suspension theoretically could extend is limited by when the links bind up or it sometimes needs to be artificially limited because other undesirable things can happen before the links bind up.

Spring/Shocks: The spring shocks have limits to how far they can extend and compress, it has to fit within the travel of the suspension otherwise you have mismatch and damage can result.

Driveshafts: Driveshafts have limits on the angles they go, especially with power going through them. Exceed the angle, the drive shaft may snap, or it may wear excessively fast. As well, driveshafts have an idle angle that they should spend most of their time transmitting power, outside that ideal angle, like if you've done a cheap lift to far, the driveshafts spends a majority of its time transmitting power, it will wear much faster.

Links and alignment: You've also got steering links, sway bar links and brake hoses that might NOT have the same extension as the lift, alignment might be different and angles can be different creating more stress. If you increase suspension travel, some suspension designs may create such a change in wheel alignment at those extremes its dangerous (the artificial limits I spoke of above).

So:
Bottoming Out the suspension fully compresses with the whole weight of the vehicle behind it, that is a tremendous amount of force and that is why there are huge rubber blocks with a very strong part of the suspension hitting it to absorb that impact and prevent damage.

Hitting Extension limit just the weight of the wheel and suspension behind it, the forces are much less, and thus if there is even a bump stop, its small, in some designs the spring or shock is designed to absorb the force and be the limiter that keeps the suspension from extending farther than it should and damage the other things above. Don't take that to believe that opposite is true, that shock and spring can absorb the much more severe bottoming out force, that is where people end up with blown shocks and damaged springs. On some designs, like the Commanders IFS, the big sturdy Strut, has a huge sturdy rubber bump stop for bottoming out. If a suspension's original design doesn't have a shock strong enough don't think it will ever be strong enough to handle bottoming out.

In the debate over the front shock of the Commander, is it a strut or a shock? You can spend hours in an academic debate, the Commander has a Double Wishbone front suspension NOT a Macpherson Strut suspension. But, the packaging, production efficiency and performance of the Macpherson strut is so advantageous, they have gone to using modified Macpherson Struts in other suspensions even though technically they are NOT performing as a structural suspension link. So they call it strut, even if its just performing as the shock/spring/bump stop and rubber mount all in a convenient condense package that performs better, its the same part, just used differently.

So, you're going to lift you vehicle and change all this:
A good lift kit has figured this all out and given you everything you need. But there are lots of bad lift kits out there, that haven't figured everything and given you everything you need.

If the lift kit leaves the suspension still able to compress all the way to its original compression to the original bump stop and the springs don't bind, then no you don't need new bump stops. The lift kit may very well result in binding or other pieces hitting and damaging before reaching full compression, which means the bump stops have to be modified. A good kit will include the modified bump stop, a bad kit will NOT and you'll likely damage your suspension.

Just raising the ride height, either with pucks/blocks or taller springs, nothing else, really doesn't get you much. There will be no additional wheel travel. The suspension will have the wheels extend to the same point as stock, which is less distance now, because you raised the vehicle by extending the suspension and taking away some of that distance for how far the suspension its limit in extension. You may have more distance for the suspension to compress, provided the pucks/blocks or taller spring doesn't cause the spring to bind before hitting the bump stop. If it does, there should be modified bump stops, so the end result, you've traded some jounce for rebound, and if you had to modified the bump stops, you've actually reduced the full wheel travel. There is some benefit in more ground clearance, thus more break over angle, fitting larger tires, but overall off road ability doesn't improve much without more wheel travel or decreased if you decrease the total suspension travel.

Live axles its easier to compensate for all the stuff I mentioned above, so the rear, you could use taller springs that don't bind with longer shocks (cause they limit the extension of the axle) and actually get more suspension travel.

The front on the Commander is Independent Front Suspension (IFS), this is NOT so easy to modify and the links in the suspension limit its total travel greatly, and driving around at a different ride height is more stressful on the steering and driveshafts, proportional to how high you lift it.

The severity of the lift is a factor, lifting it only 2", will likely NOT put all the Geometry to far out, to the point undesirable things will happen, perhaps wear might be a little accelerated, i.e. you might have to replace some suspension pieces a little sooner than if you kept it stock, nothing crazy. Judging from the posts on the forum, well in the range that arguably that parts that need replaced wasn't outside of the realm of the stock suspension.

A 4" lift? The kits I've seen are pretty radical, and that makes sense to me, there are modified steering knuckles for the IFS to compensate on the angles for steering and driveshafts. Perhaps that give you a little more wheel travel in the front. Shocks for the rear to produce the wheel travel, etc.


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Last edited by Mongo; 04-14-2015 at 10:09 AM.
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post #9 of 16 (permalink) Old 04-14-2015, 10:29 AM
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I had this exact same question, going through dozens of part numbers trying to find what I needed. I called Crawl Offroad and talked to Chris (I think?) about the 5100 vs. 5125. His answer was simple enough, the 5100's have a lifetime warranty and the 5125's have a 90-day warranty. He also said his and most distributors will not give you fits about it being on an XK like Bilstein has done in the past.
The part number he confirmed for me for the rear 5100's is 33-186009 (16.69" compressed and 27.11" extended length), so that's for a lifted application

Hopefully that helps you out a little.
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post #10 of 16 (permalink) Old 04-14-2015, 10:44 AM Thread Starter
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Quote:
Originally Posted by luckyse7ens View Post
Rear shocks do not lift in anyway, they do pose a limitation to droop in the rear if you do not get longer than stock shocks when you lift however.

Since the 1.5" lift shocks are 15.4" compressed and 24.75" extended I would be looking @ something like these two: http://www.shockwarehouse.com/site/product.cfm?id=15117 http://www.shockwarehouse.com/site/product.cfm?id=15118 for a 4" lift, depending on valving. Probably want to extend your bumpstops for that.

Ok...so the ones "Lucky" point out already are 1.5" lift shocks with 15.4" compressed and 24.75" extended.

The 5100's you just suggested Zharry.... # 33-186009 (16.69" compressed and 27.11" extended.

So those 33-186009's are 1.29" longer compressed and 0.64" less extended, then the 33-186559 F4-BE5-A465-H6 Bilstein 5100 Lucky pointed out.
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