Overextending Bilstein 5100 rears with my 3" lift, which Bilstein 5125 part?

[str8flexed]

So, long story short I have about a 2.5-3" lift and the normal Bilstein 5100 rear shocks which are only meant for 0-2" of lift.

I noticed a thud when going over speed "humps" at over 20mph when the rear of my vehicle is bouncing up in there air.

Anyway, I can deal with this... the shocks are cheap at $75 each, I think if one breaks I can then replace with them longer shocks, maybe Dobinsons or something. Don't need to go crazy and rip them out and replace them now, hell I'm happy I just put them in a few weeks ago. I just need to go over speed humps slower. I figure also, when offroading, I tend to go slow anyway when there's lots of articulation.

But, I searched and I've seen failures of the 5100's possibly from overextension. This is the one thing I'm worried about - this happening if I'm out wheeling on a road trip.

Is it really that bad to overextend them sometimes? Does anyone else overextend their shocks frequently (5100's or otherwise - I mean, basically this happens at full droop right? Or why does my sway bar not limit it? Hmm)

 

[Bumbo]

That would annoy me far too much to keep like that… plus from what I read, is that those shocks also don’t really preform that great too far past their lift specs either…

If it was my truck, I would change the shock.

 

[Teamoatmealpie]

easy trick to confirm bottoming out on speed bump. put small dab grease on your bump stop. hit your speed bump and If your bottoming out it'll be easy to see the grease transferred over.

 

[GearJunkie88]

easy trick to confirm bottoming out on speed bump. put small dab grease on your bump stop. hit your speed bump and If your bottoming out it'll be easy to see the grease transferred over.

Great tip! I think I’m bottoming out my front suspension. I will try this trick tomorrow. Thanks!

 

[Fern]

Are you sure you are not just hearing the thud from the tires hitting the speed bump or landing after being airborne?

 

[str8flexed]

Are you sure you are not just hearing the thud from the tires hitting the speed bump or landing after being airborne?

Pretty sure, this is a big round speed hump not the small harsh ones.

It kind of propels your car into the air. Don't think it's landing, either, that should be silent because of the coils right....also think the timing is wrong.

Either way I looked more into it and it seems bottoming out from compression seems more dangerous than overextending? Probably because bottoming out usually has more force? That makes me feel better, I think..

Can't wait to trash these Billie's then I can just get Icon's/King's. LOL

 

[str8flexed]

easy trick to confirm bottoming out on speed bump. put small dab grease on your bump stop. hit your speed bump and If your bottoming out it'll be easy to see the grease transferred over.

That's a good trick! But I think I'm overextending, not bottoming out..

 

[JSparky]

To find out you can either measure your shock length at rest, or jack up the rear from the frame and see how much droop you have.

I’ve been bottoming out my shocks all week just going in and out of parking lots, but I also have the stock shocks on there right now with ~4” of lift.. my radflo’s are off getting rebuilt right now. I have maybe half an inch of down travel before they bottom out.

 

[mikey's2010SR5]

Are you talking about topping out or bottoming out? I am confused.

Both are not good for your shocks, that is why we have bump stops. Granted some might have top out bumps.

I was topping out on my old coil overs and was annoyed as all hell. So I went long travel and now don’t need to worry.

I wouldn’t go beyond the lift specs of the shock.


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[Teamoatmealpie]

That's a good trick! But I think I'm overextending, not bottoming out..

hummmm,,, your thread title says 'bottoming out". Ooh well its an easy way to rule it out.

 

[JSparky]

Are you talking about topping out or bottoming out? I am confused.

Both are not good for your shocks, that is why we have bump stops. Granted some might have top out bumps.

I was topping out on my old coil overs and was annoyed as all hell. So I went long travel and now don’t need to worry.

I wouldn’t go beyond the lift specs of the shock.


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Right, topping out.

 

[WEAK_E90]

pretty sure i blew mine out by doing this... I was at 3" in the rear and like you said only ment for 2" - cant really blame them if im pushing them beyond the specs...

Im tearing them out and going a different route come spring when the salt is gone as they sound like they are loose and falling apart.

i remember the "thud" phase... only gets worse.

 

[str8flexed]

So I found the Bilstein 5125, which has multiple options. Bilstein 33-230375 seems to be what I need, but I wanted to double check.

Bilstein 5125 33-230375:

Collapsed Length (IN) - 17.11
Extended Length (IN) - 28.33
Mount Type - Stem-to-Eye


VS the popular Bilstein 5100 (0-2"):

Collapsed Length (IN)14.91
Extended Length (IN)23.50

Does this look like the right part? I know I might need bump stop extensions now to prevent it from "bottoming out" now, but at least it won't top out from overextending...

Again, this is to accommodate about a 3" lift.
Bilstein 33-230375 Rear B8 5125 Shock Absorber - Shockwarehouse.com

 

[JSparky]

Careful, I’d cycle your suspension to see what your max extended length is before your coil starts dropping out. I’m working on a write up, but I just installed OME 899’s which are a 2-3” linear coil, and I can only go to 26” before th coils start coming loose. You’ll need a dual rate/progressive coil, or an incredible amount of lift, to fit a 28” shock.

I’m working with a company to have custom 10” travel shocks made to be used with 2-3” linear coils and 2” bump stop extensions, topped out at 26”. I can keep you posted on what I do.

 

[str8flexed]

Careful, I’d cycle your suspension to see what your max extended length is before your coil starts dropping out. I’m working on a write up, but I just installed OME 899’s which are a 2-3” linear coil, and I can only go to 26” before th coils start coming loose. You’ll need a dual rate/progressive coil, or an incredible amount of lift, to fit a 28” shock.

I’m working with a company to have custom 10” travel shocks made to be used with 2-3” linear coils and 2” bump stop extensions, topped out at 26”. I can keep you posted on what I do.

You're probably right. I found another 5125 shock model - this one seems about right. 3" longer than the 5100, but not ridiculously long. I don't know how the compressed length can be similar though if the extended is longer.

Bilstein B8 5125 33-230351

Collapsed Length (IN) - 16.13
Extended Length (IN) - 26.38

UNFORTUNATELY, it does say the lower mounting eye is 5/8", compared to 19mm for the 5100's. So, I'm assuming it's not a direct fit for the rear?

Anyway, I just jacked up one side of my car and realized I only get about 3" of droop in the rear, compared to sitting height at rest.

My questions:
1)Is that low? Or normal for a lifted vehicle?
2)What normally limits downtravel? I heard it was shock length? Or could it be my rear KDSS sway bar or lower control arm?!
3)I saw in another post that other common rear shocks including Fox, OME, Icon, etc., all have an extended length of about 23.5-24". Does that mean that the shock is probably NOT the limiting factor of droop? Lots of people running around w/ 3" lifts with these shocks but I'm sure they are getting more travel ..

Copied from another post:
Bilstein 5100 Rears.....0-1" Lift 23.5" Extended
14.91" Compressed

Bilstein 5160 Rears.....0-2" Lift 23.62" Extended
14.84 Compressed

Fox 2.0 Rears............0-1.5" Lift 23.55" Extended
14.95" Compressed

(Funny that if these work for 1.5" the Bilsteins should also ???)

Fox 2.0 Rears.............2-3" Lift 24.65" Extended
15.55" Compressed

Icon 2.0....................2-3" Lift 24.3" Extended
14.8" Compressed

Old Man Emu..............60080 23.75" Extended
14.48" Compressed

Old Man Emu..............60004 22.83" Extended
14.01" Compressed

(Both of the OME's are confirmed by ARB USA to fit the 5th Gens mounting)

King 2.5" Rear......with Resi......... 24.29" Extended
15.58" Compressed

 

[MyanRagahis]

Careful, I’d cycle your suspension to see what your max extended length is before your coil starts dropping out. I’m working on a write up, but I just installed OME 899’s which are a 2-3” linear coil, and I can only go to 26” before th coils start coming loose. You’ll need a dual rate/progressive coil, or an incredible amount of lift, to fit a 28” shock.

I’m working with a company to have custom 10” travel shocks made to be used with 2-3” linear coils and 2” bump stop extensions, topped out at 26”. I can keep you posted on what I do.

I'd be interested in reading your write up.
Not to high jack the thread, but I had the 5100s in the rear with the ToyTec superflex springs. They're marketed as an additional 2" of flex with extended shocks. I'm pretty sure this is what made one of my 5100s leak a bit. I just bought 2.5 Radflos for the rear and wondering if I should get a different coil like the T13 from Wheelers, and/or get Plastics Guy Durometer rear bumpstop. Just trying to save them from the same fate as my 5100s.

 

[MyanRagahis]

2)What normally limits downtravel? I heard it was shock length? Or could it be my rear KDSS sway bar or lower control arm?!

I don't have an informative answer but this is a response I got from PlasticsGuy

"I have experience with this particular issue with shocks myself and from what I’ve seen what is damaging our Billie 5100 (or similar) is actually the down droop of the suspension. When the truck leaves the ground (jumping) The weight of the rear axle and wheels/tires are 100% supported by the shocks. Inside the shock body there is a pathetically tiny built in bump stop, it does not work well and after being hit a few times (from the shock over extending) the internal bump stop splits and the “guts” of the shock come apart and shift around, causing leaking.



Going to a larger diameter shock like the Radflo 2.5 will definitely help as the shock body is much larger in-turn allowing for a larger internal bump stop. In my opinion the best way to button up the rear suspension on your truck would be to install those Radflo’s (2.5 are way stronger) and install some limiting straps that will prevent your shock shaft from fully extending. The straps are insurance…



As far as my bump stops stopping up-travel prior to your shock bottoming out… Yes, our Durobumps will prevent the shock from bottoming out on itself. As I think about this further I really believe its your down droop killing the shocks because it would take an absolutely tremendous force to actually compress the shock to the point of failure… Shocks are incredibly strong when it comes to compression, but they hate being over stretched out."

 

[Fern]

Well, I am going to assume that's why my rears are leaking. They've been used offroad 3 times.

 

[MAST4R]

Well, I am going to assume that's why my rears are leaking. They've been used offroad 3 times.

Do you have extra spring flex or are you jumping the 4R?

 

[str8flexed]

So I spent some time jacking up and lowering my vehicle in the back, and I think the thud/clunk may actually be something else:

The panhard bar contacting the KDSS sway bar

It comes REAL close, not touching actually, but I can imagine in a non-static situation where it may touch and cause a thud. Others on this forum have reported them touching (presumably because their shocks are longer and allow them to?).

Of course, it could still be the stocks bottoming out causing the noise, but I'm not sure if that causes the sort of noise I'm hearing.. kind of a solid thud on coming from the body..

It does seem like KDSS does limit the rear articulation. I think my best bet is probably to lower my rear lift height from 3" to 2" (too bad, because I like that rake...)..then I will have 1" extra downtravel with the shocks and also more space before the panhard bar contacts. Well, in reality I am just going to keep it the way it is and not go over big bumps fast and just accept that there is reduced downtravel :-/

Attached is pic of how it stands!