Thread: Bilstein 7100 what is so good about them?

They're a relatively in-expensive high quality shock, fully rebuildable if you need to or want to change rates, very comfortable, don't fade, and give good flex.
Sources - Multiple mates have them fitted, about to fit a set myself

I think there is a lot of error in what you think the various shocks are.

The 7100's are an exceptionally high quality shock. The life of the shock will be longer than that of any other shock and if it breaks (they dont really wear out), then they can be completely rebuilt. These shocks can be had with a selectable valving or built to your own specification rather than just whatever the manufacturer decided. The also come in various lengths and travel options. These options make them really good for those who have non-standard setups and can select a shock to suit their needs.

Just to explain some of the shock design. Shocks need space inside them to compress. This is because when the shock is closed the shaft adds to the internal volume. This is done with twin shell shocks with low pressure gas, foam shocks using foam and monotube shock by having a high pressure gas in a cell that is separated from the oil. All shocks have a piston in them which travels through oil and the pistons have valves in them to create the resistance. The shock fades when the oil gets hot and mixes with the gas within the shock body.

Foam cell shocks seem to be the worst for fading from my experiences and they dont seem to recover when the cool down as the foam seems to break down. Then twin shells come next, but after they have faded the do return to normal operation. It doesn't matter how low or high quality the shock is, these properties dont change. Bilstein make none of these shocks. Monotube which Bilstein do make have the gas at a high pressure which reduces the chance of airation of the oil (ie fade) and they also have the oil physically seperated from the gas with a divider (its a floating piston). What this means, is that the shock by design can not fade. When the shock gets how however, the pressure in it increases and this further increases its ability to not fade. This is the same for every monotube.

With regards to the body denting. There are som edifferences in the bodies also. A regular twin shell or foam shock are built quite lightly because of the protective outer shell. They're built like coke cans and if they get dented then its no issue. The monotubes have much much heavier walls, like steel pipe, and you'd be hard pressed to dent them. A strike that takes out a monotube will have also destroyed a twin shell or foam shock - it'll be a big one.

The monotubes stay cool more because they are monotube rather than having the option of a remote canister. The oil is cooled directly through the shock body. Twinshells and Foams on the other hand with their additional jacket cant do this. The 2nd or sometimes 3rd shell is like putting a winter jumper onto the shock and it keeps the cool airflow off the shocks oil.

The reason for remote resorvouir is to do with packaging. In a regular monotube, the gas chamber sits at the bottom of the shock. What this means, is that for a 10" travel shock, the body might be 14" long. If the gas chamber is removed from the bottom of the shock (and put into the remote canister externally), it means that you can have greater shock travel for a given body length, eg a 14" long body might give you 12" of travel instead, or alternatively get 10" travel from a 12" long shock.

Slunnie has eloquently written a great response...

Put simply - Foam cells degrade every time they get hot and dont recover 100% so the more often (thing a good trip) they heat up the quicker they fail.


Remote canister control aeration by the gas pressure in the external canister applying pressure to the oil...


External shocks arent only for 'race cars' they are for any application where you want maximum oil volume and travel for a given body length, and controlled damping, with the ability to adjust the gas pressure....

I'm considering the Bilstein B6 off road for my D90,but I've heard a lot about these 7100's.As far as I can tell, the only advantage of the 7100 is the extra travel because of the remote reservoir,is that right? The ability to change valving doesn't interest me much.I just want to install the best shock for the job and forget about it.

I have the traditional all in one Billies. I love them. Transformed the car when combined with Dobinson's springs. They lessen the tramp effect of live axle on corregations and the vehicle feels glued to the road.

Cheers

Marty it's a bit horses for courses.

Unladen a higher rate shock will feel stiff and the ride a little harsh.

Set for overlanding and loaded it will feel great.

It also very much depends on your expectations of ride quality. Some want a magic carpet others a firm ride.

Aren't you trying to get rid of the banging?

I wrote a response at lunch today but it is not on here. I must have forgotten to press the button.

Thanks to all especially Slunnie.

Would it be too much to ask for you guys running the 7100 to list the specs of the ones you have? There is a lot to filter through on the other pages, i figured if it was listed simply here it would make it easy for me to know what to buy that seems to work for the D2. I could than get a picture of total cost as well as I've noticed it is not a simple bolt in replacement.

Lift
Install lengths
Travel length
Valving
What other parts required to fit them to a D2 E.G 1/2 to 12mm adapters
? Anything else

Do the shocks come valved and ready to bolt in from the US?
Assuming you purchase all the parts required to install is that the only cost?