The Cobra Adventure
Discussion
GCCP said:
E46 m3 come with a 3.62 as standard - they come up all the time on M3cutters. Might be a good inbetween option? assuming you have the big 210 diff?
I'm on a medium case. I did look at swapping to the large case, but with how somethings are engineered on the Cobra, it would have clearance issues. 
After building my diff up, it felt far too tight. I was hoping to just get away with the core swap, but that wasn't to be!
So I had a look at an old thread about building an E36 track car where the OP rebuilt the diff. So I reached out to him and bought some diff shims from him.
You use the shims to adjust the drag when the diff is fitted. Looking for between 11-23in/lbs of drag. A wider shim = less drag.
Had a fun night of measuring all the shims he sent.
Diff stripped back down and the original shims measured. I had a 1.48 and a 1.69 in it.
Then it was a case of trying different combos till the drag measured right. I had to use this park tool for bicycles to measure that low in in/lbs!
Final shim stack was, 1.59 and 1.79. Gaining 0.21mm.
After that, the diff could be built back up again. Which requite lightly grilling the crown wheel. Crown bolts torqued to 120lb/ft with loctite.
Put it back together and measured the backlash. All on spec at 0.08mm. Case back together and filled with Kaaz LSD oil.
So I had a look at an old thread about building an E36 track car where the OP rebuilt the diff. So I reached out to him and bought some diff shims from him.
You use the shims to adjust the drag when the diff is fitted. Looking for between 11-23in/lbs of drag. A wider shim = less drag.
Had a fun night of measuring all the shims he sent.
Diff stripped back down and the original shims measured. I had a 1.48 and a 1.69 in it.
Then it was a case of trying different combos till the drag measured right. I had to use this park tool for bicycles to measure that low in in/lbs!
Final shim stack was, 1.59 and 1.79. Gaining 0.21mm.
After that, the diff could be built back up again. Which requite lightly grilling the crown wheel. Crown bolts torqued to 120lb/ft with loctite.
Put it back together and measured the backlash. All on spec at 0.08mm. Case back together and filled with Kaaz LSD oil.
Edited by Waitey on Sunday 7th April 15:29
I feel that way every time something comes off the 3D printer or arrives from Protolabs, I get mega excited that my digital thing is now a real thing 
This thread is absolutely ace. Curious about the revopoint scanner too, I’ve got the Pop2 and not enormously happy with it. I like the look of the dry shampoo trick, however. Almost certainly cheaper than the AESUB spray I’m currrently using.
This thread is absolutely ace. Curious about the revopoint scanner too, I’ve got the Pop2 and not enormously happy with it. I like the look of the dry shampoo trick, however. Almost certainly cheaper than the AESUB spray I’m currrently using.
Standard custom car rollacoaster story incoming.
Custom Gaz Golds are here.
Ah ffs.
God bless owners groups.
Some random old chap from the USA asked me if I’d had the damper bodies shortened.
I was all like nah just built them up to E36 DTM specs.
He was all like, measure the damper bodies.
Mine are too long by 40mm, meaning I’ve lost that in compressing and gained it in droop.
Not ideal.
So I’m going to make some new top mounts which raise that mounting position by 40mm.
Will allow me to keep the right ride height and keep all my fancy new geo.
Pictures and 1000 words and all that.
Here you can clearly see my issue. 40mm gain in length, 10mm loss in stroke. Stroke I'm not bothered with.
The OEM top mount, mounts the bearing 30mm below the mounting face of the strut tower. So I need to bring that up to 10mm above. I also need to bring the centreline of it outward by 1mm
Custom Gaz Golds are here.
Ah ffs.
God bless owners groups.
Some random old chap from the USA asked me if I’d had the damper bodies shortened.
I was all like nah just built them up to E36 DTM specs.
He was all like, measure the damper bodies.
Mine are too long by 40mm, meaning I’ve lost that in compressing and gained it in droop.
Not ideal.
So I’m going to make some new top mounts which raise that mounting position by 40mm.
Will allow me to keep the right ride height and keep all my fancy new geo.
Pictures and 1000 words and all that.
Here you can clearly see my issue. 40mm gain in length, 10mm loss in stroke. Stroke I'm not bothered with.
The OEM top mount, mounts the bearing 30mm below the mounting face of the strut tower. So I need to bring that up to 10mm above. I also need to bring the centreline of it outward by 1mm
I was getting worried about suspending a corner from 3 M8’s.
But after reading 10.9 M8’s can take ~1.8t of force each, I feel a little better.
As there’s no way the OEM mount can take 5t through it.
nd to double double check, looked up the forced through a Macpherson strut in an extreme pothole strike.
Assuming 300kg on the strut at rest.
A pot hole strike would produce a force of 11052 newtons. (FORCE ANALYSIS OF SUSPENSION STRUT UNDER VARIOUS LOAD CASES 2016.)
Which is about 1152kgf of upward force.
The max force the fasteners can take is <5000kgf.
So a 4+x safety margin.
But after reading 10.9 M8’s can take ~1.8t of force each, I feel a little better.
As there’s no way the OEM mount can take 5t through it.
nd to double double check, looked up the forced through a Macpherson strut in an extreme pothole strike.
Assuming 300kg on the strut at rest.
A pot hole strike would produce a force of 11052 newtons. (FORCE ANALYSIS OF SUSPENSION STRUT UNDER VARIOUS LOAD CASES 2016.)
Which is about 1152kgf of upward force.
The max force the fasteners can take is <5000kgf.
So a 4+x safety margin.
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