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      04-06-2020, 01:01 PM   #1
Tambohamilton
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Tam's 330d Touring

I guess this is a 'build thread', but let me start by acknowledging that my 330d is neither noteworthy nor impressive...but I like it. It feels nice to drive, even at town speeds, I can shove a couple of MTBs in the back, and it cruises effortlessly on the motorway. You won't see many pictures of it, because, well, it's a stock e91...and I've washed a car twice in my life.



I bought it about 2 years ago. It's a 2007 with the M57D30TU2 engine, 6MT, RWD, SE (non-sport), and was completely stock, and in decent cosmetic condition. Mechanically it's always been fine too, but it's taken a fair amount of work to get it to where it is now. It had just over 120k miles on it when I bought it, and now has something like 136k.

When I bought it, it suffered fairly badly from tramlining, the egr pressure converter was quacking away, the aux belt squeaked until it warmed up, and the rear tyres had some pretty uneven wear on them. Those were the immediate things anyhow.



In the first year I replaced the rear tyres, got an alignment (0.7deg of rear toe out, -2.3deg camber), replaced the aux belts and tensioner and alternator pulley, replaced the egr pressure converter, replaced the blower fan, one front radius rod, and all the glow plugs. I used OE or OEM parts wherever possible. The blower fan I bought used on eBay. I swapped the rear OE Bridgestone RF tyres for some Michelin PS4 - a much better tyre, especially in the wet. I did an oil change (Castrol Edge 0w-30), and all filters too. Also replaced the rear pads and discs, though they probably had about another 5k miles left in them.



That all helped a lot with the tramlining and ironed out the more noticeable annoyances, and got it through its first MOT with me. I still wasn't happy with the handling though - it felt like I had to constantly readjust my actions when driving, based on how the car reacted. If I got it all right, it felt great, but that was the exception. More often I had to adjust steering input mid-corner, etc.

I also had to rebuild the ABS pump motor, to sort out the brushes. Turns out it had already been done before, but the new brushes were just sticking in their holders a little.



In year 2 (last year), I replaced all front suspension arms except the one I'd already done, both front struts, strut tops, pulled the alignment pins, and got another alignment. I was mainly chasing down the tramlining, which was bugging me. Also I could see and hear that the front shocks were done for. I fitted Koni Special Active struts, because the marketing spiel sounded appealing. The ride definitely improved with all this, but the tramlining didn't change much. Eventually I changed the front tyres to PS4 too, which did help a fair amount with the tramlining. All the fresh parts in the front end raised it a fair bit, and the comparatively sagging rear end made it look daft and handle poorly...though new front rubber was a huge upgrade!





Later in the year I fitted M3 rear subframe bushings, e93 M3 rear sway bar, new sway droplinks, Special Active rear shocks, new shock mounts, spring pads, and diff mounts. Tramlining gone!! And the rear end feels way more taut. The new rubber in the back raised it up a bit, but still a little lower than the front. The e93 M3 rear sway is a bit much honestly - I should have settled for the e90/92 one - but the grip balance is still an improvement from before. In the dry it felt good, in the wet the back end wants to go first. Sometime in all this, my tailgate locking saga began...






Lemforder M3 RSFB...I wonder what the grind mark is for....

That pretty much brings us up to the start of 2020. The tailgate thing was starting to really annoy me, so I replaced all the wiring in the tailgate hinge...it needed to be done, but didn't help the locking issue. Back to the drawing board.





I'd been slowly amassing parts since last autumn to sort out the things which were beginning to bug me; M3 front wishbones, M3 front radius rod inner bushings, front sway mounts and droplinks, M3 steering rack, track rods and ends, Xd strut tops, egr and engine mount vacuum control valves, glow plug controller, vacuum line, and something to fix that damn clunk from the back end! Covid gifted me the free time to do the work (clouds/silver linings, etc), so last week I got into it.



First up I altered the rear sway mounting enough to ensure it cleared all the suspension arms all the time. It's a bit of a bodge, but it's solid. Again, the e90 bar would have helped. Nothing else seemed out of line back there, so fingers crossed it was the source of my noises. Thread.

Next up I replaced the glow plug controller and vacuum control valves, and vacuum lines. That glow plug controller is a pain of a job! Even with the intake manifold removed, it's still buried under a mess of plumbing and wires. I swore at it a lot. Vacuum control valves and lines were much easier, but I admit I didn't replace the lines going to each engine mount...I'll get them another time. I took the opportunity while the manifold was off to scrape some of the coal out of the head and ports, and the manifold itself. I'd scraped it a bit last time it was off, but I still got heaps more out of it this time. Also I hadn't removed the egr inlet from it before, so I did that this time - the manifold inlet was about 1/4" thick with coal in places! Glad I got the worst of that out. My swirl flaps are staying in, even though they're pissing crud all down the side of the engine there - I don't currently have a viable solution for replacing them, and I'm not going to delete them.







After that it was time for the front suspension, again. The steering rack went in quite smoothly. Maybe it's a euro thing, or a RHD thing, but I didn't need to cut off the plastic tab at the input shaft. I did need to swap one of the hard hydraulic lines from the old rack onto it though; the M3 hard line fouled the hose bracket. I also installed a new PS reservoir, since I had one lying around (postage error in my favour from another order - seller told me to keep it). Pressing the inner radius rod bushings out, then M3 ones in went quite smoothly. Strangely the bushing was super tight to remove on the OE arm that I have, but not so bad on the Febi Bilstein one, but the OE M3 bushing was tight going into the Febi arm and not so bad going into the OE arm. Clearly the Febi arm and bushing are both a tad smaller. I was content with how both new bushings fitted though, so happy days. I used 2x jubilee clips to compress the new bushings to get them in - it was on their limit of strength though! The rest of the front end parts went in just fine. I nearly left a bearing shield washer out of one of the strut assemblies, but (thankfully) realised it just after I'd finished installing that strut top.



I decided to bleed all brakes and the clutch while I was at it. The brakes went without a hitch, but the clutch refused to bleed. I'd spilt the fluid out of it (and all over my face!) when removing the CDV, so I had to bleed it to get it working again. I ended up removing the whole clutch and brake pedal assembly in order to get the MC out. I rebuilt the MC (thanks to @bryanbdp post here ) with a little mod to the bleeding flap valve, threw the lot together, and managed to force enough fluid through to get a functional clutch again. It's not right as it is, but it works. An awesome side effect is that my clutch pedal now sits lower - I wish it would be there all the time!!

At this point I took some time to find the source of some water that was ending up in the driver's (RH) foot well, and causing the FRM to freak out when it got humid. I think it was on or the other or both the wiper arm axle seals where they go through the plastic trim at the bottom of the windscreen, or the seal between that trim and the bottom of the windscreen. Time will tell whether reseating them has helped.

With the car back on its wheels, I used a spirit level to measure camber (for comparison with before measurements that I'd taken), and string lined the wheel alignment. Last time I did this I got it within factory specs, so I'm not going to get it aligned at a shop unless I feel like something is awry. I set the front wheels parallel to the string lines, so very slightly toe in. I had read in other places around the forum that M3 front wishbones gained about 0.75deg more negative camber compared with the stock arms, but I actually got about 0.45deg. Still, it's in the right direction!

I decided that my tailgate locking problem must have been caused by the JBBF being (water) damaged, so I decided that I'd have a last ditch at updating the module, just in case that helped. It updated successfully, so I decided to do the DDE too , and wound up with not being able to reset the service indicator. Idiot. It was working fine! After a lot of ranting and panicking, I figured out my mistakes, and did it right. Happily, that meant that I also returned to the JBBF with the correct programming and coding operations, and presto! The tailgate now locks! (thread here)

Last of all I proceeded to make a shit job of a handful of stone chip repairs... Fuck it. Shows it's my car. Also removed the dealership sticker that had slowly been beginning to offend me, and foam taped the rear numberplate on (plastic screw inserts were rattly).

I haven't had an excuse to go for much of a drive yet, but WOW it the front end and steering feel great now! Particularly the steering weight and feel. I no longer have to readjust my steering inputs. It feels, compared with before, like I just look where I want to go and the car does it. Manoeuvring and parking the steering is pretty heavy, but it's no bother at all. Way easier than the non-PS cars I've had (1990 VW jetta, 85 Ford Fiesta). Also the engine doesn't run out of puff so badly at higher revs; it's keen to go.

I'm sure I'm not finished with this thing yet, so I'll update this thread as I go, just in case it brings entertainment, information or distraction to anyone

Last edited by Tambohamilton; 05-24-2020 at 05:02 PM..
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      04-06-2020, 03:51 PM   #2
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Quick spreadsheet to calculate camber angles from the spirit level measurements...
https://docs.google.com/spreadsheets...it?usp=sharing
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      04-06-2020, 04:00 PM   #3
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I used Xd strut top mounts to lower the front a little. Partly for aesthetics, partly for maybe a smidgen more negative camber and load on the nose.

X-drive vs standard (non-sport) strut top mounts:

Xd mount is some 10mm less tall, so the car will sit ~10mm lower than with the standard mount. Note that an M-sport mount is somewhere around half way in between these 2 mounts (maybe 3mm less tall than a stock mount).

Xd bolts are a bit longer than standard ones, and need to be swapped out

L-R: Xd bolt, standard bolt, alignment pin.

The Xd bolts will foul the strut braces, being about 6mm longer than the standard bolts. I simply hammered the bolts out of my old set of standard top mounts and the Xd ones, and hammered the old bolts into the new mounts. You just need to get them in there well enough that they wont spin as you put the nut on. Tightening the nut will do the rest of the work. You should be able to get them fully home anyhow though.

Ride heights:
Measured the BMW way, but without any ballast. That is, bottom centre of wheel rim to underside of wheel arch. 18" wheels. Note that I don't have any flat ground to do this on, barring a reasonably smooth gravel driveway.
Location/Before/After Xd top mounts and M3 RSFB
FR/616/607
FL/620/608
RR/599/609
RL/596/607

Last edited by Tambohamilton; 04-10-2020 at 11:33 AM..
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      04-06-2020, 04:16 PM   #4
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Not had a chance to try fitting these yet, but I think they're a win;

19 x 4.8mm (3/4" x 3/16") stainless self-tapper, with a M4 x 20mm stainless penny washer. The washer just spins onto the bolt, but won't easily fall off.

Like I say, I haven't tried them yet. I've got a feeling that 16mm (5/8") might have been a better length for the screws.

Last edited by Tambohamilton; 04-10-2020 at 10:21 PM..
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      04-07-2020, 11:55 AM   #5
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Lots of great stuff in here, Tam!

I'm absolutely with you and of the same impressions after replacing some of the front end bushings, tho, now you have me wanting an M3 rack!

On the rear end I'm also loving the new-found traceability thanks top subframe bushing inserts. I also added the E92/E84 rear chassis brace which worked well with the stock wgaon rear brace. Check out my build thread for when/where/how etc. They're so cheap to find I figured why not?

I had a good laugh at your brake fluid bleeding fiasco, sorry! I had a similar situation when I *unecessarily* changed front calipers. Great, what a real smart fool I am.

Questions:
- Can you go into a bit more detail about your camber and toe measurements - specifically, using the spirit level. I have one but I am not sure how to derive the exact angles - some formula I'm missing?

I'm currently in the process of home-measuring my Camber and Toe. The front Toe seems a bit far out @ 1.75mm per wheel in the front. Not surprising the given the Camber I'm running...

Thanks and it sounds like your diesel is really coming together! cheers to that - a bunch of work!

EDIT: some pretty rudimentary geometry I can do with just a plum bob and measuring can be done to find the camber angle... PLUS I missed your spreadsheet link - very helpful, thanks!

Last edited by tlow98; 04-07-2020 at 02:49 PM..
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      04-07-2020, 02:41 PM   #6
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Yes. Do the M3 rack. It's just better, unless you really hate any steering resistance when at a standstill!

I might have to keep an eye out for one of those chassis braces. (EDIT - Just seen yours is an e91 too! ) Mine, being the e91 already has bracing to an A frame behind the rear subframe, from just in front of the rear subframe front mounts...I wonder if the e84 brace would be retrofittable in this case - looks like the 2 need to overlap. Where did you get yours, and how much did you pay, if you don't mind me asking?

Camber using a spirit level. I was inspired by someone who installed an M6 x 1.0mm bolt into a spirit level to use as a camber gauge. The pitch is 1mm, so every turn of the bolt is 1mm of progress. From having the bolt flush with the level surface, adjust the bolt until it reads level, while counting the turns. Or use a vernier to measure the bolt protrusion.
I didn't exactly do that though - my way is less accurate, but doesn't involve modifying a spirit level... I just offered the level up to the wheel, and directly measure the gap between the wheel rim (or whatever your contact point is - mine was actually the tyre bead) and the level, when the level is vertical. Then high school trig (tan^-1) to figure out the angle from the offset measurement, and the distance between the 2 level contact points. Because my car wasn't necessarily level (not on even ground), I used a couple of bolt heads just in front of the bonnet catch as a datum. Certainly not the most accurate point to measure from, but I was just in need of some sort of reference. I'd say it's accurate enough, having registered 0.45deg change on one side and 0.46deg on the other!

I haven't calculated toe yet...it's close enough for me, though I might get the string out again and measure it properly since I'll probably have a lot more free time what with Covid. I'll use the same method though, just string instead of spirit level. And I'll need to reasonably accurately measure track width F&R too... I think yours is a bit off. I'd expect <1mm per wheel, off the top of my head.


Last edited by Tambohamilton; 04-07-2020 at 02:56 PM..
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      04-07-2020, 07:32 PM   #7
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Yap, E91 only way to fly for me

Here is more info on the E92 rear brace in concert with the stock E91 rear brace. They do overlap and both are used on the OE E84 with certain option packages (pano, awd, etc.) at least that was what I was told previously. Regardless, they work well together. All I did was shim (via washers) the E91 A-frame down about 1/4". There is foam placed appropriately on both stock units so no rattling, etc.. Thanks to @soravia for this info! His wagon thread is pretty epic but here's the part that pertains to the Brace https://www.e90post.com/forums/showp...0&postcount=56. His wagon apparently did not have the front and aft holes threaded as standard. Still useful mod tho, I think.

I got mine at a Pick N Pull salvage yard for $46 with hardware

More info from my post:
https://www.e90post.com/forums/showp...4&postcount=19

Great stuff with the spirit level My garage tilts ever so slightly to one side but I bet I can account for it.

And yes, iirc correct toe in the front is IN ~1.5mm total. Mine is at 1.75mm per side OUT. Haha, oops! It's so incredibly happy to turn tho - imagine that!

Wish we got the diesels over here... le sigh. Enjoy it.

Last edited by tlow98; 04-07-2020 at 09:31 PM..
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      04-08-2020, 03:53 AM   #8
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Great info, thanks! Found one of the braces on eBay for £40...tempting! Need the 'pushrods' too though, they seem to be going for £20/side.

Wasn't looking forward to the thought of spacing the stock brace down at all, but then I saw your idea of welding the 2 braces together...that would be good, surely!? And it'd save fiddling with spacers.

I think I'll save this mod for when I have some free cash and free time. I'd like to replace a lot of rear suspension bushings, and maybe M3 guide rods too.

Just do the same as I've done in my spreadsheet, though maybe you could measure your garage floor instead of the car. Subtract that angle from one camber measurement and add it to the other.

You guys got diesels... The 335d. I wouldn't mind one of those, if they came in manual. I'm happy with mine though. I don't need any more power, I'd like a bit less turbo lag at lower rpm though. But that's just me being lazy.

Last edited by Tambohamilton; 04-08-2020 at 08:52 AM..
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      04-25-2020, 03:34 AM   #9
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Quote:
Originally Posted by Tambohamilton View Post
Not had a chance to try fitting these yet, but I think they're a win;

19 x 4.8mm (3/4" x 3/16") stainless self-tapper, with a M4 x 20mm stainless penny washer. The washer just spins onto the bolt, but won't easily fall off.

Like I say, I haven't tried them yet. I've got a feeling that 16mm (5/8") might have been a better length for the screws.
Fitted these yesterday; 16 x 4.8mm (5/8" x 3/16") self-tappers would be a better match for the original, but these 19mm (3/4") fitted fine.

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      04-25-2020, 03:48 AM   #10
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Made a spreadsheet to reasonably accurately calculate the toe angles from string line measurements against the wheels (not set up parallel using bars).

I measured the track (well, outer width) immediately in front of and behind each wheel, then took the average to get the track of that axle. Note that this gives slight inaccuracy whenever the wheels aren't exactly parallel to the string lines...but this will only be very small (~1mm in 2760mm).

Green cells are ones I enter measurements into, in order to calculate what's what:
https://docs.google.com/spreadsheets...it?usp=sharing

I've also got some tools to calculate camber based on spirit level measurements, on the spreadsheet, but that will have to wait for another day...
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      05-24-2020, 04:45 PM   #11
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Added camber measurements using a spirit level to the spreadsheet...
https://drive.google.com/open?id=1p1...hf2MxfBH8EPcNg
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      05-24-2020, 04:53 PM   #12
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Started writing this in another thread, then realised that it probably wasn't much use to anyone there, so I'll shove it here... Having a ponder about switching between stock springs to sort the suspension out...maybe.
Complete sedan specs here (inc weight distribution):
https://drive.google.com/open?id=10-...fK48ckDHXfAqWb
Touring specs here (not inc weight distribution):
https://drive.google.com/open?id=1-m...7fcAp7DsHHm2hu

For my case, a 330d sedan weighs 1610kg, with 47.7% of that on the rear axle. So thats 842.03kg F and 767.97kg R.

The 330d touring/wagon weighs 1675kg, and I'm going to assume that the entirety of that 65kg extra is on the rear axle: 842.03kg F, and 832.97kg R. (this being so close to 50/50 pleases my OCD greatly!)

A 335d sedan weighs 1655kg, with 47.3% of that on the rear axle: 872.19kg F, 782.81kg R. 335d wagon is 1720kg: 872.19kg F, 847.81kg R. So, from tlow98 's post here, D7 would be for 872kg on the front, and D8 would be for 848kg on the rear.

The springs on my car (330d touring, non-sport) are C6 F, and F3 R. C6 makes perfect sense, by tlow's system...but I have no idea what to make of F3 on the rear. I think the rear is already plenty stiff though! With these springs and my current setup (Koni SA shocks, Xd top mounts, M3 front arms, M3 RSFB, 18" wheels) my ride heights are pretty much exactly 608mm F&R when unladen.

Using generic calcs for spring rate (wire dia, spring diameter, number of coils), I got 124lb/in F and 456lb/in rear. Motion ratios, from fe1rx on 1addicts, are 0.96 F and 0.565 R, which gives wheel rates of 119lb/in F and 258lb/in R. If these are at all indicative, I can see why I get the impression that the rear end is stiff!

Some other day I'll figure out how to draw a conclusion from that on how to select a spring from another model, and predict the resulting rate and ride height reasonably accurately...

Last edited by Tambohamilton; 05-28-2020 at 07:18 PM..
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      05-24-2020, 05:10 PM   #13
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Almost pointlessly small update from today...

My car not being fitted with servotronic steering from the factory (funnily enough!) means that I have nothing to plug into the servotronic unit on the M3 rack...and I have glorious, weighty steering permanently!

I guess it's unlikely to come to any harm really, and I'm unlikely to ever need it, but I wanted to cover up the servotronic plug on the rack. Without measuring, I ordered an vinyl cover intended for M12 bolts/fasteners, and it fits really rather well. A hair smaller would be ideal, but I don't think it'll fall off.



I packed it with petroleum jelly, for some water/rust-proofing.

Also been beginning to wonder whether some of the rattling/clattering from my front end may be caused by engine mounts. I can't find anything loose, and nothing in the handling feels loose, but I do get some proper rattling from the front end sometimes. Most recently noticed it when turning right where the inside wheels went over a bump in the road - loud clatter was clearly audible! Anyone got any input as to how done this mount is?



There is a tiny bit of rubbing evident under the engine mount arm, from the bump rubber, but it's far from polished (just look how rough that casting is!! ).

Last edited by Tambohamilton; 05-24-2020 at 05:17 PM..
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      05-25-2020, 10:29 AM   #14
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Quote:
Originally Posted by Tambohamilton View Post
Started writing this in another thread, then realised that it probably wasn't much use to anyone there, so I'll shove it here... Having a ponder about switching between stock springs to sort the suspension out...maybe.
Complete sedan specs here (inc weight distribution):
https://drive.google.com/open?id=10-...fK48ckDHXfAqWb
Touring specs here (not inc weight distribution):
https://drive.google.com/open?id=1-m...7fcAp7DsHHm2hu

For my case, a 330d sedan weighs 1610kg, with 47.7% of that on the rear axle. So thats 842.03kg F and 767.97kg R.

The 330d touring/wagon weighs 1675kg, and I'm going to assume that the entirety of that 65kg extra is on the rear axle: 842.03kg F, and 832.97kg R. (this being so close to 50/50 pleases my OCD greatly!)

A 335d sedan weighs 1655kg, with 47.3% of that on the rear axle: 872.19kg F, 782.81kg R. 335d wagon is 1720kg: 872.19kg F, 847.81kg R. So, from tlow98 's post here, D7 would be for 872kg on the front, and D8 would be for 848kg on the rear.

The springs on my car (330d touring, non-sport) are C6 F, and F3 R. C6 makes perfect sense, by tlow's system...but I have no idea what to make of F3 on the rear. I think the rear is already plenty stiff though! With these springs and my current setup (Koni SA shocks, Xd top mounts, M3 front arms, M3 RSFB, 18" wheels) my ride heights are pretty much exactly 608mm F&R when unladen.

Using generic calcs for spring rate (wire dia, spring diameter, number of coils), I got 114lb/in F and 440lb/in rear. Motion ratios, from memory, from fe1rx (sp?) on 1addicts, are something like 0.9 F and 0.5 R, which gives wheel rates of 103lb/in F and 220lb/in R. If these are at all indicative, I can see why I get the impression that the rear end is stiff!

Some other day I'll figure out how to draw a conclusion from that on how to select a spring from another model, and predict the resulting rate and ride height reasonably accurately...
Yes! The wagon rear springs are odd-balls. Mine are 'X4' which by any stretch of the imagination (and the numeric ticker compared to your F3's) would mean my rear springs are relatively stiff. They most definitely are NOT. I have one of the lighter iterations of this car, so I have no idea what to think about the rear wagon springs in general...

Everything you mentioned makes perfect sense to me and my research backs it up, fyi.

Also, what spring rate calculator are you using?
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      05-26-2020, 02:34 AM   #15
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Cool, thanks. It really would be nice to know what the deal is with the rear springs...oh well!

I just used a formula from the internet for the spring rates. Should be somewhere near; at least repeatable for comparison, though not necessarily actually real-world accurate.
https://docs.google.com/spreadsheets...t?usp=drivesdk

EDIT: Added some better labelling and fixed some rounding errors in the spreadsheet. Also included a source for the formula which has a reasonable explanation of how to use it.

Last edited by Tambohamilton; 05-28-2020 at 05:29 PM..
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      05-28-2020, 04:53 PM   #16
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Back faffing with springs again, and found the Sachs spring catalog! Super useful!
https://drive.google.com/file/d/1Of8...ew?usp=sharing

It has the BMW code (eg 'C6') referenced to their part numbers, as well as chassis, engine, and sport/non-sport, etc.

First nugget is that 'Cx' front springs are for non-sport suspension, and 'Dx' for sport suspension. tlow98 had already told us about that.

Next nugget is that some of the BMW codes actually refer to the same part; eg 'D7' and 'D8' both refer to Sachs part 993 257 (BMW parts 31 33 6 767 379 &
31 33 6 767 380).

Anyhow, for the front springs tlow had it mainly figured out.

Rear spring coding seems to be a lot less logical, especially with e91s...

My rear springs are F3... This corresponds to Sachs part 994 480, which is for a non-sport e91 (as well as others). That's spot on the money. F4 springs are the same Sachs part no. F5 are for the same setup, but with a towbar.

K4 (994 485) are for the same setup but sport suspension (no tow), and K5 (994 486) for sport + towbar.

Sorry, tlow, X4 code doesn't exist in the Sachs cat...are you sure it wasn't K4? K4 (and K3, K2) springs are fitted even to 316i tourings; probably the lightest variants around!
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      05-28-2020, 07:18 PM   #17
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Quote:
Originally Posted by Tambohamilton View Post
Started writing this in another thread, then realised that it probably wasn't much use to anyone there, so I'll shove it here... Having a ponder about switching between stock springs to sort the suspension out...maybe.
Complete sedan specs here (inc weight distribution):
https://drive.google.com/open?id=10-...fK48ckDHXfAqWb
Touring specs here (not inc weight distribution):
https://drive.google.com/open?id=1-m...7fcAp7DsHHm2hu

For my case, a 330d sedan weighs 1610kg, with 47.7% of that on the rear axle. So thats 842.03kg F and 767.97kg R.

The 330d touring/wagon weighs 1675kg, and I'm going to assume that the entirety of that 65kg extra is on the rear axle: 842.03kg F, and 832.97kg R. (this being so close to 50/50 pleases my OCD greatly!)

A 335d sedan weighs 1655kg, with 47.3% of that on the rear axle: 872.19kg F, 782.81kg R. 335d wagon is 1720kg: 872.19kg F, 847.81kg R. So, from tlow98 's post here, D7 would be for 872kg on the front, and D8 would be for 848kg on the rear.

The springs on my car (330d touring, non-sport) are C6 F, and F3 R. C6 makes perfect sense, by tlow's system...but I have no idea what to make of F3 on the rear. I think the rear is already plenty stiff though! With these springs and my current setup (Koni SA shocks, Xd top mounts, M3 front arms, M3 RSFB, 18" wheels) my ride heights are pretty much exactly 608mm F&R when unladen.

Using generic calcs for spring rate (wire dia, spring diameter, number of coils), I got 124lb/in F and 456lb/in rear. Motion ratios, from fe1rx on 1addicts, are 0.96 F and 0.565 R, which gives wheel rates of 119lb/in F and 258lb/in R. If these are at all indicative, I can see why I get the impression that the rear end is stiff!

Some other day I'll figure out how to draw a conclusion from that on how to select a spring from another model, and predict the resulting rate and ride height reasonably accurately...
It's 1am here, so I'll keep this brief...

Following on from my previous post about selecting different stock springs to achieve 'better' suspension performance, I've created a new spreadsheet to estimate ride height using calculated spring rates and other published data...

https://docs.google.com/spreadsheets...it?usp=sharing

In the spreadsheet C6 and F3 springs (tabs) are the stock springs fitted to my car. D6 and K4 springs would be fitted to my car if it was an M-sport model (it's non-sport/'SE'); these are used just to validate against BMW published ride height data.

Props to fe1rx for publishing all the work he did on his 1er, so folk like me can come along and pinch bits of useful information (motion ratios, unsprung weight).


Now all I need to do is figure out what wheel rates etc I actually want! Anyone fancy donating me a copy of Milliken and Milliken so I can (re-)learn some stuff??

EDIT 02 June 2020: Fixed some severe errors on the spreadsheet, and made it a bit more useful!

Last edited by Tambohamilton; 06-02-2020 at 06:42 PM..
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      06-02-2020, 06:51 PM   #18
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Made some large changes to the spreadsheet this evening, including fixing some glaring errors, and went through a few more spring options...

I've narrowed my search down to 2 combinations:
1. D6 sport front springs (as would be OE on my car if it was a sport model), with D6 rear springs plus a 6mm spacer. This combination would give me the sport ride height, without increasing rear stiffness at all. Front stiffness does increase a little, but it is currently crazy soft!
2. D7/D8 (same parts) front springs, and leave the rear end as it is. This maintains my current ride height, but increases front stiffness a bit more than the D6 front option.

I think I need to do some reading to make a decision. The second option being cheaper and less work does sound enticing though!

I'm keeping on with posting this stuff, just in case someone finds it useful at some point down the line...
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      Yesterday, 03:26 PM   #19
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Yeah, if you have removed the run flats Iím of the opinion there is a big need for stiffer springs. Thatís why Iím going D8 all around. Not trying to give you more opinions, but ya know, here they are. :-)
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      Yesterday, 05:12 PM   #20
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Haha, yeah I hear you...there are so many options for the rear! At lest on the front you just have sport/non-sport in various weights; on the rear there's sport/non-sport, e91/others, and various weights!

Couple of notes about the D8 springs...

Front D8 springs are the same as D7 springs; I believe BMW gave them different codes because they are used in different scanarios sometimes, but I don't really know. Anyhow that's just a bonus because you can use either part to the same effect. Running this spring up front will likely rase your ride height to that of the non-sport version of your car...approximately (or minimal change if you already have non-sport suspension there). It's rate is around 145lb/in, giving 132lb/in wheel rate.

Rear D8 springs are around 615lb/in rate (195lb/in wheel rate). Assuming your springs were K3, they were around 570lb/in (180lb/in wheel rate). Both springs have very similar free length, so I think you'll likely see some ride height increase there too...I'm not sure how much. K5 springs are also 615lb/in, but 5mm shorter, so would be closer to your original ride height.

TL;DR - I think fitting D8 all round might not be great, either visually or in terms of handling.

For my own car - which has the wrong rear sway (e93 M3) - I'm aiming for minimal increase of the rear stiffness, but some increase in front stiffness. I want to work out how much I actually want/need rather than going by forum experience.

My reasoning for that direction is that I think the e91 cars were built to be loaded with stuff in the boot/trunk, then driven, where other models weren't and therefore the e91 rear springs are overrated unless you've got a weekend's camping and fishing gear and 2 children in the back...which is most notably not the correct time for spirited driving unless you're late for a flight! My non-sport e91 330d came with F3 rear springs at 545lb/in. An equivalent e90 would be fitted with C4 rear springs at 445lb/in. That's a 22.5% increase in rate for an 8.6% increase in axle load (unladen). It makes sense for practicality, but I think not so much for handling.

YMMV
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