a4ncar

Folks who have changed the rear coil overs are you using the old top-hat from the old shocks or buying a new one? This is for the standard suspension on W205 with steel springs. Any insight will be a great help. Thanks

Edit: For the W205 you do not have to remove the trunk liner but you do not need to remove the fender liner to pull the shock out due to the top hat design. Looks like you have to use the top mount from the old shock as this is not sold as a replacement part.

Keith66

I did mine from the standard luxury suspension to coilovers. The new coilovers had a new rear shock top hat included. Yeah, that's a cool thing about the W205, you don't need to go in the trunk at all, everything is accessible from within the fenderwell. I removed 3 of the inner fenderwell lining (or "splash-guard") trim screws and pulled the liner down and there was plenty of room to access the top shock flange bolts and get the shock in and out.

Just a tip and word of caution, since the threaded inserts are part of the body stamping, make sure you start the bolts with finger power only to make sure they are not cross-threaded before using any tools. I'm sure cross-threading these inserts would not be a fun or cheap job to fix

a4ncar

You were lucky to get new top hats with your coil-overs. I assume yours were not from BC racing as mine did not come with one and I double-checked with tech support. Thanks for the tip.

Edit: I see now that you had NEOMAX from old threads.

Keith66

Mine are Silver's coilovers.

That's a bummer, I have no experience getting the hat off or installing it on another shock, sorry. I would think it shouldn't be too difficult, hopefully!

I was initially totally confused about how to setup and adjust the rear... being they are separate shocks and springs, so if you need help with that, just give a shout.

a4ncar

Taking the top hat will require a Torx bit to hold and pass-thru socket to remove it. Here is what I understand on how to set /install the rear springs/shocks. Please correct me if I am wrong or you have any tips/tricks for the rear install:

1. Adjust the rear spring to a height based on your first guess what it should be for the drop you are wanting. Install the spring in the spring perch (spring control arm) without the shock attached to the spring perch but hanging from top strut mount (top hat). Measure the unloaded spring length before placing it in the perch.

2. Put a jack under the spring perch and raise until the length of the unloaded spring shortens by 7-10mm to achieve the proper preload.

3. Once the preload is achieved, adjust the shock length so that it reaches the lower mounting hole depth. Install the shock bolt.

4. Install the tire and put something under the tire like 2x6 to make sure the jack will clear it once you have lowered it.

5. Repeat until the desired drop is achieved.

Any input by anyone who has done the DIY coilover install or saw it being done by a shop will be greatly appreciated.

Keith66

Glad to hear the top hat swap sounds simple. #4 is definitely a smart move. If you can't get the jack out, you know you did it right, lol!

The shock adjustment method you describe may be correct, but I cannot understand mechanically how that would work correctly. I'm no suspension wizard, but it seems to me at least, using that method would not keep the pre-load on the spring and would not position the shock piston in the proper range of it's overall travel when the vehicle's weight is on it. I would think that when you let the jack off the spring control arm, the shock will allow the control arm to droop down, losing your pre-load. My coilovers are a different brand as yours, so there may be some engineering differences but I can share how I did it using some information shared from the peeps at Silver's. I'm not saying it is THE way but it worked well for me:

FYI, This is for the car in the air the whole time on a jack or jack stands with the wheels and tires removed:

1. Fully install all your new stuff, coil springs, shocks, all fasteners tightened.

2. Extend (lengthen) the shock as far as you can until it gets feeling tight, so you're not limiting the droop of the spring control arm.

3. Adjust your desired ride height by adjusting the length of the coil spring adjustment collar. (If you're going low, the coil spring will be very loose and most likely will not be touching the perch on the top.)

4. Using a jack under the spring control arm close to the wheel hub, compress the suspension just to the point that there is no more slack between the coil spring and its perches. There should be no more gap, but not tight or compressed.

5. Jack the spring control arm up (to compress the suspension) another 3/8" to 1/2" to pre-load the coil spring and hold.

6. Contract (shorten) the shock until it stops (in my case, it's a solid stop you can feel).

Step 6 sets the extension limit of the shock and should limit the spring control arm travel and hold the coil spring in its perches, just in case you ever want to jump over an abandoned bridge Dukes of Hazzard style, your coil springs don't come flying out :p You should notice when you let the jack off the spring control arm, it does not droop much, as the shock is holding it together. I also think that when setup this way, when you let the vehicle weight down on the suspension, the shock piston range of travel should be in the correct position.

a4ncar

I think both procedures are achieving the preload. I will see which method is easier to do in practice. Did you actually measure the length of spring before and after preload? I am not sure how easy is to measure the spring length when it is installed. Did yours come with any specific instructions for the install? BC did not include any installation instructions.

The reason, I think the spring will hold the preload because once it is compressed by let's say 3/8", I will be adjusting the uncompressed shock to meet the length requirement at which I have for 3/8" preload. Once it is bolted through the bottom hole, and the jack is removed from under the shock, It should hold the spring control arm at that height.

I could be wrong, I will run it by BC Tech support before the weekend. See if you can poke some holes in what I said above, so we can understand better.

Keith66

I'm with you dude, I don't have all the answers or complete confidence of the correct method either. The Silver's also have no instructions, so we are left throwing darts at an invisible dart board Probably my only advantage was that I got mine and they sat in my garage in the box for about 5 months, so I had plenty of time to think about it, lol

I did not take any measurements of the coil spring, only measured the adjustments made on the adjustable collars so they were even on both sides. For the pre-load, I had a measuring tape from the floor to the control arm edge so I could see how much I was jacking the arm up (I did 1/2" each side).

I see now what you're saying about the shock and if it's actually at its mechanical limit of extension when you capture the bottom bolt, then yes it will have the same effect of limiting the control arm. I'm curious to hear what BC comes back with!

a4ncar

Ok, I will post it here on what BC says's for future reference. I still think both procedures are ok.

a4ncar

Ok, finally got done this past weekend. For reference, I did check with Wes @ BC Racing using the chat feature on the BC Racing website by sending him the steps above that I posted and his response was "yes that is correct on how to set it up". This is the link of the video he sent me for installation, it is not specific to W205 but explains the procedure

https://www.bcracing-na.com/articles/tech-videos

Since it was the first time I ever did the coil-overs, it took a considerable amount of time, as I was checking and double-checking on the installation. Also cleaning the underside too while I was at it including the rear wheel liners. I think I should have done the rear first as it is easier for fronts to match and would reduce some re-work. I did not adjust the pre-load on the fronts and left to the default factory setting. I set the dampening to 25 for fronts and 20 to rears, by default they were set to 15. Fronts are easier to change and for rears, you have to drop the wheels.

Any additional advice from fellow members on dampening, etc?