Rear spring plates and trailing arms

MartinClan · #1 12th December 2006, 12:15

Now I have completed the engine install all I have left to do mechanically is to sort out this s0dding problem with the rear spring mounts being in the wrong place.

I had a brainwave - perhaps I could move the spring plates on the trailing arms instead? (It would save hacking the chassis around) They would only need to move about 15mm and I guess they are just spot welded on. What does the forum think? Does anyone have a spare trailing arm that I could try with (save messing around with my refurbished arms in case it turns out to be a no no)

BR

Robin

GreatOldOne · #2 15th December 2006, 22:18

I'm not sure they are spot welded on... I think the lug that the bottom portion of the spring engages with is part of the arm. I could be wrong though. Any way, wouldn't it be easier to move the top mount out?

I know it's no help, but my seats seem to line up OK:

I have to say, it's not what I expected it to look like - I thought I''d just slip the original BMW rubber seat over a lug on the chassis an that'd be it. These are the adjustable spring seats though. I just ended up cutting up the old rubber seats to fit the marlin system.

peterux · #3 16th December 2006, 09:33

Ooooh, that's a bit diffrent to mine?
Looks like Mark has made some changes, I wonder why?
Did you mention somewhere about getting your rear springs modified by Marlin?
Can we see a picture?

thanks

Peter

MartinClan · #4 16th December 2006, 17:14

Quote:

Originally Posted by GreatOldOne

I'm not sure they are spot welded on... I think the lug that the bottom portion of the spring engages with is part of the arm. I could be wrong though. Any way, wouldn't it be easier to move the top mount out?

Just had a look again. It seems like the lug is part of the plate that the spring sits on. It's a question of how this is attached to the arm. If I can move the plate the lug goes with and and cures the problem.

Moving the top mount is not going to be that easy. It would be difficult to get an angle grinder in to cut it off - and an angle grinder makes an awfull mess (red hot bits of metal flying about not good for the finish on the chassis) Then I would have to get a mobile welder to weld it back on again in the correct place - wouldn't trust my welding plus it is upside down...

I think I will persue moving the bottom plate - I am trying to get hold of another couple of trailing arms to practice on first though - don't want to wreck my niceley refurbished ones...

Anyone out there got a couple goin spare?

Robin

GreatOldOne · #5 16th December 2006, 17:37

Quote:

Originally Posted by peterux

Ooooh, that's a bit diffrent to mine?
Looks like Mark has made some changes, I wonder why?
Did you mention somewhere about getting your rear springs modified by Marlin?
Can we see a picture?

thanks

Peter

No probs - here's the springs:

What they seem to have done is cut the top 2-ish turns of the spring off, and then heated the top coil to bring it flat. The flat part then slips over the cup on the spring seat. I wasn't keen on metal on metal there, so that's why I cut up my old rubbers to fit the Marlin mounts.

The seat is only adjustable in an up or down (Z-Axis) motion, as it's a metal cup with a large bolt welded into it which screws onto onto a threaded stub. The pointy rubber bit on the end of it is from the old rubber mount, trimmed down and with a hole bored into them slightly smaller than the stub.

Patrick · #6 17th December 2006, 11:21

Quote:

Originally Posted by MartinClan

Just had a look again. It seems like the lug is part of the plate that the spring sits on. It's a question of how this is attached to the arm. If I can move the plate the lug goes with and and cures the problem.

Moving the top mount is not going to be that easy. It would be difficult to get an angle grinder in to cut it off - and an angle grinder makes an awfull mess (red hot bits of metal flying about not good for the finish on the chassis) Then I would have to get a mobile welder to weld it back on again in the correct place - wouldn't trust my welding plus it is upside down...

I think I will persue moving the bottom plate - I am trying to get hold of another couple of trailing arms to practice on first though - don't want to wreck my niceley refurbished ones...

Anyone out there got a couple goin spare?

Robin

We will have some trailing arms going spare soon, they are from a 316i compact they are drums though and 5 stud.

As for chopping, warming bending springs. I didn't want to do that - just seemed a little unsafe to me.

MartinClan · #7 17th December 2006, 19:04

Hi Patrick

I may be interested in the trailing arms if they are going to be available soon. The fact they have drums dosen't matter Aa I just want to take them to bits to see how the plates are fixed. I have bid on some on ebay - but the guy hasn't got back to me so I don't know if he has changed his mind about selling them. So - I suppose the question is how much do you want for them? I could probably come and collect them sometime over the xmas break - it would be a nice run for the old 318is. Be intersted to see your car in the flesh and perhaps your brothers "little project" as I am seriously thinking about buying a 318ti compact at the moment.

Cheers

Robin

Patrick · #8 17th December 2006, 22:31

I'll have to ask Richard as they are his trailing arms

, we're waiting for brake hoses, which will hopefully arrive this week before we can get started on that bit. Your very welcome to pop over during xmas

The good news is the side project drove for the first time today. There's a really strong resonance at 2500rpm need to investigate if that's our shoddy welding to extend the Z3 exhaust or that the Eisenmann back box is just very loud - which is shouldn't be as Richard order the quietest one.

peterux · #9 17th December 2006, 22:48

Quote:

Originally Posted by GreatOldOne

No probs - here's the springs:

What they seem to have done is cut the top 2-ish turns of the spring off, and then heated the top coil to bring it flat. The flat part then slips over the cup on the spring seat. I wasn't keen on metal on metal there, so that's why I cut up my old rubbers to fit the Marlin mounts.

.

Thanks, Jason. That explains the new mount design.

I bought some Apex shortened springs so would be interested in the free length of you moded springs. I guess I can go this route, if mine are two hard.

thanks again

Peter

GreatOldOne · #10 18th December 2006, 10:00

I'll measure them tonight for you, before I finish painting them.

GreatOldOne · #11 19th December 2006, 21:04

Sorry for the delay. I fogot to measure them last night... Must have been the paint fumes. The free length is approx. 190mm or 7.5" if you don't hold with this new fanged metric system.

peterux · #12 24th December 2006, 20:25

Quote:

Originally Posted by GreatOldOne

Sorry for the delay. I fogot to measure them last night... Must have been the paint fumes. The free length is approx. 190mm or 7.5" if you don't hold with this new fanged metric system.

Thanks, that's really good news. The Apex springs I have used were 185mm (7.25") free length before I fitted them which means they are in the right ballpark.
They were designed for lowering the stadard BMW 325i so thay may be a little harder than the shortened original springs. I have kept the original springs, so I can get them modified later if the Apex's are too hard.

Good luck with your build,

Peter