DIY Large Chassis Coilovers

[loxxrider]

I'm just putting this here temporarily because I'm afraid it will get deleted over on MG if I don't do it soon!

I intend to clean this up a bit with some more info and pics from various members who have done this setup and helped make improvements. I will be doing this same process on my 635 this weekend, so I think I should be able to take pictures of that to help here (all of the same stuff applies).

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The DIY Coilover page for T44's

So after much frustration with figuring out the coilover setup for my 200 20v, I have decided to make a thread to make it easier for others to follow suit. There is of course more than one way to do this, but here is the way I chose to go. This setup should be pretty nice for anyone...you just have to pick spring rates that suit your style.

Parts you will need:

-Bilstein sport (or Koni adjustable) struts front and rear...on 200 20v's the thread is 12mm for the rears. Bilsteins will have to be re-valved for the best ride and strut life. They die rather quickly and aren't valved well for anything above about 350 lb/in spring rate.

http://www.Shox.com has them for $500 for all four.



-Your choice of springs...they have to be 2.5" ID and 6"-7" tall however. Any bigger wont let you go low enough. Ther rear can do just fine with 7-8" I believe. I went with 450= k front and 550= k rear Eibachs. Many find it beneficial to stagger the spring rates front to rear like I have to help make these nose-heavy pigs be less "understeery." If you race a lot, you might want more rate... if you like your ride like a Cadillac, you might want a bit less rate. I found 450 and 550 to be rather nice for street and occasional track use.


Then you need the coilover parts from http://www.A1racing.com

-2x front sleeves COK12452H (fits strut housings...just over 2" ID)
-2x rear sleeves COK12451 (fits the rear struts...just under 2" ID)
-4x perches COK12460
-4x upper perch COK12470



Bicknell Racing BRP-603 can be used as an alternative to the COK12470 for more suspension travel. These hats can be ordered at 716-285-7502



For the front hats I had to widen the hole in the ones that came from A1 in order to get it to slide all the way down onto the strut the way I wanted it. That way I could put the stock perch above it along with the top plate so that the strut bearing could sit in there properly.

http://shop.a1racing.com/coiloverkits.aspx

Should end up costing you about $170.

-larger snap rings Thanks to Nuugen, you can get these large snap rings to sit the sleeves on top of for the rear struts
part# 3100-0200, from: http://www.akronbearing.com



Finally, these might help with spring binding issues:
Coilover thrust bearings
http://www.speedwaymotors.com/QA1-Coil-Over-Thrust-Bearing-Kit,6001.html

-Helper springs recommended to keep these seated and to perfect the setup!
HYPCS100 is the part number for helper springs from A1racing.com




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Installation

Basically for the rears you just slide the sleeves over the body and put it all together. Nothing really interesting here.

In this picture, the assembled rear Audi Bilstein is on the right.



For the fronts, you have to cut the perches off and then weld a ring onto the strut housing for the sleeve to sit on. They should be roughly 3" OD and roughly 2.170 ID and made out of 1/4 inch steel.

The rings are made from 1/4" plate steel that can be had from Lowes. I turned it on a mill, but you could get away with a drill. Its just going to suck while you are doing it and it might not be perfect...but that's more than fine.

You'd need a 2 1/8" hole saw and a 3" one.



The ring is welded on the front strut housing as far down as you can get it and as level as possible.

Before you can slide the ring onto the strut housing, you'll need to cut off the stock spring perch. Just go at it with a grinder. There is no easy way about it. Just attack the factory weld all the way around it and it will eventually just crack off or break off when you hit it with a hammer. Then you have to make it completely smooth with more grinder work or a flap wheel and also take off the rest of the paint on the strut housing. Thats the only way you'll be able to fit the ring and the coilover sleeve. You may also have to take a little more material off of the inside diameter of the ring as the strut housing OD is not actually 2 1/8" its a little bigger.

Then you basically just assemble. I put some grease between the strut housing and the coilover sleeve to stop rust and assist in removal if its ever necessary.

The easy solution for spring binding is the needle thrust bearings I've added into the parts list above. Then you don't need a spherical bearing to facilitate spring turning.




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Some pictures

Sorry they are so dirty, this was from after quite a bit of use and abuse



this is top of the rear



bottom of the rear...you can see the nice c-clips



This was one of the first pics taken after the install... that is about as low as you can go on the stock strut housings. More discussion on that later.

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Strut Mounts

Old design I had made. They had some issues, so I went for a re-design.





New upper strut mount I was working on and hopefully will be able to work on again.

[loxxrider]

OK here is a quick DIY on the actual strut housing modification. These pictures are from the work I did on my 635csi, but the concept is identical (except you can also cut off and rotate the steering arms on the T44/URS like Ed D. has done on his car).

First, remove the struts from your fine automobile. If you don't have the ability to do this without a DIY, then you probably shouldn't attempt the rest of this! I'm I/we could help someone with that on an individual basis if it comes to it.



Observe your soon-to-be awesome strut housing:



Start hacking away at the old spring perch with a grinder or cut-off wheel. Just be careful not to cut into the strut housing itself unless you intend to cut that section out.



You should end up with something like this when you're finished. Mine is pretty hacked up, but I didn't care because I cut that section out later. It turns out that I really should have cleaned that part up and cut down lower, but hindsight is always 20:20 isn't it?



At this point, you might think you could just put the threaded sleeve on the area where the spring perch once sat. Not so. An uneven surface could lead to stress concentrations which can split or crack the aluminum sleeve leading to failure down the road. You need to make (or buy) a ring of some sort for the sleeve to sit on. See the ones I made in the post above and the ones Ireland Engineering (below) included for me when I bought some of these parts from them.

Next, observe how much shorter and awesome your new shorter struts are. Also notice how nasty the one you are replacing looks.



(This is just for the BMW guys)... Look how much shorter these are!



Now if you're going to shorten the housings for use with shorter struts, you need to get on to deciding where you're going to make your cuts. This is a pretty critical decision and depends on your spring length shock length combination (and how much threaded sleeve you have to work with). Like I said earlier, I made mine a bit too high, but I really wanted to get a specific part of the strut cut out to avoid excess grinding and some rust issues.



When you are all happy with your calculations and have made your cuts, get to welding!



One thing to note about the welding process... You really want to get the two tube sections as close to concentric as possible. The easiest way to do this is to put a strut in the housing while you are welding. The problem with this technique is that the struts are filled with 1000s of pounds per square inch of pressure, and overheating one could cause it to fail and explode, potentially maiming or killing you and anyone around you. As a result, you must only weld small sections at a time and allow the strut to cool off after a few small passes. That's why the welds look so inconsistent in the pictures.

We would weld about two or three half-inch sections and then spray the strut off with some water. Even then, it was getting hot enough to scorch the paint on the strut body. Whatever you do, just be careful, and also be mindful to weld in such a way that the strut housing doesn't warp. Do welds 180 or 60 degrees apart from one-another to keep the warpage in check. Check that the strut can slide in and out of the housing easily after each session. Don't weld the strut housing to the strut! LOL

Just take your time and you will be A-OK.



After the sections are welded together, weld your sleeve perch on.



Now you can test fit the strut and measure how much spacer you need to make for it (if it is shorter than the housing you have). A piece of aluminum tubing or even a stack of washers will do the job just fine. You want to space the strut out such that when you fully tighten down the gland nut, it doesn't bottom out on the strut housing, but it has plenty of thread engagement (a few threads sticking out above the top of the housing is OK in my opinion.



Next, get some paint on them bad boys and assemble them! It should definitely be time for a good drink by this point.












Finally, you may have to space the wheel out from the strut in order for the tire to clear the spring and spring perch depending on what wheel/tire setup you are running. On this 635csi, a fairly standard 17x8 et20 wheel and 235 tire doesn't even come close to fitting. An 8mm spacer (minimum) is required for clearance. That's OK though, as these cars have no problem swallowing up wider wheels. I'm putting some 15mm spacers up front. 20's or more could easily be fit with some negative camber, but I wanted to keep camber as close to neutral as possible for street use.

This picture was taken with about 12mm of spacer:



Quick pro hint: You can estimate the spacer you need by putting washers between the wheel and brake hat/hub and assembling.

[AudiQuattros]

very useful information

[2.5TYPE44]

I talked to someone at Shocks.com and they could not tell me if the rear Koni's have the groove cut in the shock body for the clip. Does anyone know if the grove is cut in the adjustable Koni's. They said I need part# 80-2630 sport.

[ringbearer]

Koni welds perches on. I just had these made. Double external adjustable.
20150130_120001 by ringbearer93, on Flickr

[loxxrider]

Oh very nice. Can you tell us how we might order those?

[ringbearer]

Racing.Koni.us@itt.com
Mason O’Hara is who I emailed with. Took about 5 or so weeks, I am pleased with them, can't wait to get my car back on the road. I also had them revalved for 500 lb springs.

[loxxrider]

Perfect rear shock solution I think.

[ringbearer]

I think so as well. Some people say they bottom out or are very close to when run very low so shortening them may be good if you want to be really low.

[lucidmatt]

PSA: Tire Rack has front Bilstein Sport inserts for $99/ea shipped. Best price I found by far. Still researching rears (though Ringbearer seems to have one hell of a solution for those!)

[ringbearer]

I went with koni 8611 1257 for the fronts, 2Bennett sold me the small.parts needed to fit them. I really wanted all 4 corners double external adjustable.

[lucidmatt]

oh you fancy. I'm looking forward to hearing how these things change the characteristics. The investment is just a bit too rich for my blood...

[ringbearer]

Autoplicity had the best price but they still aren't cheap. My build thread has the list of attention the suspension parts I'm updating. I don't want to clutter this diy too much.

[iammrfancypants]

Installed these a long time ago and just was able to drive the car yesterday. I have the same setup as Chris is using. I will get into there and check it out and take photos. But the ride is super bouncy and stiff in the rear it was described to me as having plywood for suspension in the back. Anyone else have this issue? Any direction as to what it could be?

[loxxrider]

That's strange, mine never felt bouncy to me. A bit firm, yes. If it really is bouncy feeling to you, then the culprit would be improper valving of the rear shocks.

[crimson ghost]

Any of you guys have trouble with the retaining ring for the collar on the rear Bilstein shock ?? Mine came loose and crashed straight down from a small bump.

[loxxrider]

Yes, it has happened to some. Others have not had the problem. Where did you get your retaining ring from?

[crimson ghost]

They came from Bilstein. These were not off the shelf but revalved as well.

[loxxrider]

This is why uprated snap rings (circlips) are recommended. Now that there has been a failure on your struts, the seating surface for the circlips may be compromised. Installing uprated circlips after a failure like this may result in another failure unless further measures are taken to prevent it whether that be welding them on or something else.

[crimson ghost]

Thanks for the help. I'll look into my options to get a new groove added.

[ringbearer]

I had my welded spring seats on my custom konis break free, there is a lot of force applied to those parts

[loxxrider]

Yeah, but there is something wrong with the weld they did on yours. There is no way a weld with proper penetration and heat treatment would have broken.

In a snap ring application, the weld wouldn't be there to support the ring in shear. It'd be there to prevent separation of the clip. Some kind of clamp for the clip could also be machined to prevent clip unseating while also providing a better seat surface for the sleeve.

If course that new qa1 solution looks decent too! But that doesn't help current bilstein owners.

[crimson ghost]

I'm waiting to hear back from the warranty dept. I'm not sure I feel comfortable with anything but a new strut. I'm glad it was out of alignment and I wasn't taking a curve at speed.

[loxxrider]

I'm guessing they won't warrantee it if you tell them it was used with something other than the stock perch.

[ringbearer]

My weld was crap no doubt. I have a set of 2B rear threaded sleeves and they have a groove machined to capture the snap ring so it cant expand without removing the sleeve.