Some notes on Bilstein 5100 shocks

Some notes on Bilstein 5100 shocks.

Bar Pins - Bilstein bonds the bar pins to the bushing on the 5100. You can push the bar pin and the bushing out of the shock, but that bar pin is NOT coming out of the bushing. If you want to run BPE's, see the note below on replacement bushings.

Bushings - Manufacturer bushings are available for a nominal cost. I found them for as cheap as $3 each online. Bilstein makes both urethane and rubber bushings as replacements. The rubber bushings have a steel sleeve molded in and are double tapered (like an hour glass). Do yourself a favor and get the rubber bushings. Sometimes a shock bushing gets abused and worn, needing replacement, while the shock is still in good shape. Here's your solution.

Running a Bilstein upside down - The jury is still out on that one. Some places say that the valving doesn't work correctly when you flip them, some places say it's not a problem. If anyone runs Bilstein 5100's flipped, please chime in with your experiences. Bilstein recommends not running their shocks upside down on some pages of their site, and says it's not a problem on another page. That's for the same part number by the way. They do make shocks that are essentially identical to the TJ rear shocks with the rod down though. Haven't looked for similar front shocks yet.

Boots - I run the boots, have for years, and have never had a problem with it. With that said, boots or no boots is a choice that needs to be made. Reasonably speaking, you probably want to take them off. That means a little cutting with a sharp knife on the back shocks and wrestling with them on the front. Shock boots are probably more decorative than functional, and are a stylistic leftover from the '80's. If you do run shock boots, don't zip tie the boot to the shock.

DON'T try to run the gas charged Bilstein steering damper. That thing will mess you up the instant it is installed.

A correctly installed Bilstein 5100 has the lettering right side up. You can read it without standing on your head.

Understanding Bilstein Valve Ratings
Damping forces of Bilstein valvings are measured in Newtons at a velocity of 0.52 meters/seconds (approximately 20 inches/second). The ratings shown correspond to those measurements; rebound force is the first number, followed by compression force (rebound / compression). Conventionally, the ratings are written as one tenth the damping force in Newtons.

EXAMPLE: Valve rating: 275 / 78
Rebound force is 2750 Newtons at 0.52 m/s
Compression force is 780 Newtons at 0.52 m/s
Higher numbers mean higher (firmer) damping forces. For example, 360/80 has more control (is firmer) than 275/78, while 170/60 has less control (is softer) than 275/78.

Digressive shocks
In a Digressive shock, as shaft speed increases, damping forces increase but at a decreasing rate. In other words the shock is stiffer hitting a bump at a higher speed than at hitting the same bump at a lower speed. But, the amount of stiffness doesn't increase at the same rate as the speed increases. Example: Hit a bump at 5mph and the shock is stiff. Hit a bump at 10 mph and the shock is 2x stiff, hit a bump at 15 mph and the shock is 2.5x stiff, hit the bump at 20 mph and the shock is 2.8x stiff.

Digressive shocks can provide low-speed damping control without being unreasonably harsh on rough surfaces. Digressive shocks allow separate damping and rebound rates.

The TJ shocks are made in the USA.

Flipped means rod down in the information below.

TJ part numbers:
B8 5100 - Shock Absorber
Part Number: 24-186810
Position: Front
Descriptor: For Front Lifted Height: 0-2"
Collapsed Length (IN): 13.06
Extended Length (IN): 21.18

Part Number: 24-185257
Position: Front
Descriptor: For Front Lifted Height: 3"
Descriptor: With Short Arm Lift Kit
Collapsed Length (IN): 14.88
Extended Length (IN): 24

Part Number: 24-188180
Position: Front
Descriptor: For Front Lifted Height: 3.5-4"
Descriptor: With Short Arm Lift Kit
Collapsed Length (IN): 14.98
Extended Length (IN): 24.63

Part Number: 24-185929
Position: Front
Descriptor: For Front Lifted Height: 3.5-4"
Descriptor: With Long Arm Lift Kit
Collapsed Length (IN): 14.98
Extended Length (IN): 24.63

Part Number: 24-187190
Position: Front
Descriptor: For Front Lifted Height: 4.5"
Descriptor: With Long Arm Lift Kit
Collapsed Length (IN): 16.51
Extended Length (IN): 26.5

Part Number: 24-185943
Position: Front
Descriptor: For Front Lifted Height: 5-6"
Descriptor: With Long Arm Lift Kit
Collapsed Length (IN): 16.97
Extended Length (IN): 28.44

Part Number: 24-186827
Position: Rear
Descriptor: For Rear Lifted Height: 0-2"
Collapsed Length (IN): 12.81
Extended Length (IN): 20.08

Part Number: 24-185264
Position: Rear
Descriptor: For Rear Lifted Height: 3"
Descriptor: With Short Arm Lift Kit
Collapsed Length (IN): 14.63
Extended Length (IN): 23.07

Part Number: 33-185514
Position: Rear
Descriptor: For Rear Lifted Height: 3.5-4"
Descriptor: With Short Arm Lift Kit (flipped)
Collapsed Length (IN): 15.41
Extended Length (IN): 25

Part Number: 33-185934
Position: Rear
Descriptor: For Rear Lifted Height: 3.5-6"
Descriptor: With Long Arm Lift Kit (flipped)
Collapsed Length (IN): 15.41
Extended Length (IN): 25

Just a note on my installation. I installed 5100's when I installed the H&R springs. The springs gave me just about 1-1/2" of lift. I did not need to adjust my bump stops after installation for the springs, the shocks or my 31x10.50R15 KO2 tires on Grizzly 15x7" wheels. The installation worked out rather nicely and works great together on the trails I run. YMMV
Thank you for posting this, VERY helpful as I try to navigate the various options for TJ/LJ!
 
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I went with the 5100s; thank you for listing part numbers. Only issue I had is the dreaded top bolt breakage on the top rear left shock mount. Took a dremel tool with metal cutting disk (went through 4 of them) to cut the welded nuts off the frame. Really only had to break the welds, then knock them off. Very hard to get to though and the whole job took about 6 hours because of this. Replaced with new bolts (not provided) and was good to go. Note; These 5100s worked perfectly with my 4" lift on my LJ. The ride is much nicer now, though there is still a bit of sway at speed that I don't care for.
Josh (2).jpg
 
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Hey guys,

Im years (almost a decade) late on this forum, but I am considering B8 5100 24-185257 and 24-185264 (the 3 inch lift ones)

I currently have Rancho 5000x (the 2.5inches advertised ones) and while their dimensions (up/down travel) are near ideal, they are very soft for my choice of offroading (dune bashing in the middle east), the car flip flops around too easily and is far from the feeling of a controlled ride.

I read Bilsteins generally provide a very well controlled ride, but I have one concern about the rear one. The dimensions of the rear shock would provide me with only 2.87 inches of uptravel and id need around 3.38inch of bumpstop length to save them from bottoming out. I had around 2.7 inches uptravel on an older, wrongly purchased pair of ranchos and I would always bottom out even on bumps onroad. So I am worried that I would face the same thing here, or are the Bilsteins much stiffer that they wouldn't bottom out?

Has anyone tried the 3inch ones and suffered from the same thing and/or faced bottoming out on the rear side? The shocks are in my cart and im hesitant to complete the purchase for this one concern, so any info or feedback on this would be highly appreciated! Thanks guys

PS. I have JKS 3inch lifted springs, JKS upper arms and Terraflex lower arms, hard top, 33inch tyres, no extra weight like winch or otherwise, in case that helps in any way.