Sunday, December 16, 2012

Cut springs and other things

So I spent most of Saturday on another project; helping clad my daughters Christmas present; a "Cubby House" - the reason it's in quotation marks is that it's rather well built - silverwrapped, will have pink bats, and it's on a movable steel skid that is designed to fit into our trailer when we move (we're currently renting). It's a bit of forward planning so as she gets older, instead of falling into dis-use, it will become her own "space" for study etc.

Next up, a photo from work I did a week ago but forgot to take and upload - the mounting bracket and location for the Ford EEC-IV ECU:

Next, here's what I decided to do this weekend. I have problems staying motivated on one task at a time (if you've been reading this build the whole way, that may have become somewhat obvious to you in the way I chop and change between different aspects of the build!). I decided to cut the springs for more low. The shocks on the car seem really good (no extra bounce etc) but when I drove it last (i.e. when it was still registered, but with overheating issues from the engine limiting drive-time) it had far too much body roll for my liking.


Much to the chagrin of the E21 evangelists on Bimmerforums (see discussion thread here), I decided to cut the springs as an initial step. I don't intend on returning it to standard height with factory springs (if I need it higher for Rally down the track, I will do it with coilovers with stiffer springs to control the body roll!) so am not losing anything by cutting the originals. Plans down the track (for adjustability and added stiffness) is to get a second hand set of S13 or R33 coilovers to make fit and work on this car. In the meantime, the fronts are Bilstein and the rears Koni Yellows, so the shocks should still do okay for a while.

I haven't taken an after version of this shot yet as I'm waiting for the springs to full settle overnight; however this is a "Before" shot of the driver's side rear standard height.

I went with a two coil cut, as recommended by one of the few people on BF not abhorred by the sacrilege I was about to bestow on this poor 3 series (let's remember, I tried selling this car intact before I began this project but got zero interest - if it wasn't for this project it would have been scrap metal a long time ago!).

I used an air powered grinder at first. Unfortunately, this one is cheap and fairly hungry for air. My grandfather bought it at Aldi then decided he didn't really need it. I'm glad, as it's the only "straight" grinder I have, and despite having to stop many times and wait for the air compressor to "re-charge" so I could do the job, it was a much better tool for the task than my normally trusty angle grinder due to doing the cutting in the car. Here's a bit of info for anyone looking at lowering an E21 this way: with the rear of the car off the ground, the rear springs aren't really under any compression. There's enough to stay captive, but not enough to break your grinder/arms/face when you cut through. If you're unsure, try and compress the springs slightly with your hand - if you can get a bit of wiggle out of them then it's probably OK.

Enlisting the ever present help of Mr Hamilton, yet again. Cutting the spring becomes a two step process, as we're taking off two coils, it's not possible to remove the cut off section easily without cutting it in half again; it's easier to cut two, then in half than to cut one at a time, as the first is very close to the spring perch (and you don't want to be cutting that!) - see below:

Here it is with both rears done, and lowered back down - note it hasn't fully settled yet. I'm not expecting any massive changes as the springs have already put in years of work, however the change in the amount of spring/leverage to the weight of the vehicle may mean they have some slight give in a day or two - we'll see what happens!

In the front, you MUST cut full coils, as the top hat and bottom spring perch have formed shapes for the spring to seat into. In the rear, you can get away with cutting however much you need as you can just rotate the bottom rubber.

Here's another tip for those of you contemplating cutting your springs in-car like we did. Front springs ARE under compression with the weight of the car off them! Here's what happens if you try cutting them in car, without spring compressors:

Instead, you need to undo the top nut (remove the cap with a pair of multigrips, undo the 19mm nut with a socket or offset spanner - a deep impact socket would be best however if the whole shaft rotates you might need to use an offset spanner and a smaller spanner to hold the flat sections at the top of the shock shaft to stop it rotating. Take care not to destroy your elbow on the LHS when the nut finally breaks - from experience, the bonnet catch hook is in just the right position to cause a great deal of pain!

Undoing both sides at once will give you the advantage of having more room to play with, and the disadvantage of the suspension having much more chance of being in the wrong place when you want to try and get it to go back where it should! We had both undone for the first side, and as a result re-fitting this side took a great deal longer than it should have!

The biggest issue we found was with getting the assembly back into the car - the top spring hat kept getting caught on either the top of the thread for the shock, or the collar just beneath the thread. If I had DECENT spring comressors that weren't: A) too long, or B) just plain trying to kill us, this would have been a much easier step as we could have placed the top hat where we needed it. Instead, on both sides, I had to file a slight taper into the hole on the hat to make it easier to guide into place.

There was still some difficulty getting the shock into place, we managed to get it centered but it was still binding slightly inside the top bearing. A small spray of WD40 and gentle redirection with a flat head screwdriver (you could see which way it was out, and gently push in the other direction) then allowed it to pop into place enough that the nut could be done up further pulling it through. The nut was then removed and re-installed with the correct original washers (one flat and one spring washer).

A lot of people mentioned on BF about the front lower control arm hitting the frame rail when the car is too low. Here's how mine sits now. With Michael jumping on this corner of the car, the rail does not bottom out, in fact it only seems to go about as far above horizontal as it is below when un-loaded as per this image. We will see how it goes in practice! As this is not a street car, if it DOES hit, I am quite happy to cut any fouling areas around the mouth of the subframe, or indeed to make a custom lower control arm to replace the standard one, allowing more clearance. If I were to make a custom arm, I would possibly replace the front swaybar with a simple adjustable rose-jointed locator bar.

Here's how it sits now; it's a significant improvement if I do say so myself, and the shocks don't appear to be in danger of bottoming out with two coils removed all round. The front still looks a tiny bit too high, however I don't really want to remove another full coil. Perhaps I could lower the spring perch? On the subject of modification, if the rear geometry is too messed up with the lowering that has been done, it looks like a relatively easy job to lift the entire rear subframe by at least an inch with only some minor modifications for clearance of the upper control arms and the tailshaft, and raising the diff mount to suit. I guess we'll see what happens there; perhaps down the track when it's coilover time, the subframe will get some fettling too!

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