Thread: Coilover DIY?
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      05-03-2020, 04:13 PM   #51
Surly73
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Drives: '11 535xi 8AT KWv3 MPE MHD xHP
Join Date: May 2012
Location: Oakville, Ontario

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Quote:
Originally Posted by Luky View Post
Go out to an empty parking lot and try some hard 30-40 mph turns. Finding mine has a fair amount of understeer now. Need to try setting the rear shocks to 4 or 5 (found I cannot reach the knobs with the tires on ), maybe reduce rear tire pressure a couple PSI (running a 255/35-20 square set up now @ 38psi). If that doesn't do enough I may take the M5 competition package front sway off and go back to stock msport front sway. Already have the H&R rear sway.
I agree. I haven't done any of the parking lot "skidpad" tests to check the balance. I was thinking (but didn't ever tell anyone) that I wondered if it tended more to understeer than ever before and now you've said the same thing. That's interesting because it would have to mean that the front has gained a lot of firmness relative to the back, but if anything I feel the rear received the biggest boost in firmness. It sounds like we're running very similar sway setups except I have the M5 front, not M5 CP front.

See my other post on tire inflation and load ratings. On my summer package the door sticker recommended 35/39 became 36/37 if you consult the load tables. That's going in the wrong direction, I know, but still interesting.

I could look at going back to non-sport stock front end. A non-sport front sway paired with an H&R 20mm rear sway should/could oversteer like crazy. Part of me would love to get the original sway with proper end link orientation back on the front as long as the balance was sorted...

I can say that the platform is WAY more predictable than before. I can confidently enter into turns without wondering what mid-corner adventures await me when I encounter any mid-corner road undulation or when the floaty suspension "bounces" off of the sway bars. I can also say that it seems confirmed that ultimately there is less grip to go with that control (since compliance increases grip, e.g. drifting cars are super firm) and now I'm to the point where I could probably break things loose while still in control. With stock suspension PS4S never came anywhere near to breaking free from what I could detect. It just felt like you weren't going to make it.

There's simply no time or place to do any real testing - still working on that.


Quote:
How/where are you measuring 350mm for your ride height? I am measuring ~24.5" (622mm) from the bottom edge of the wheel (rim) to a marked spot directly above the wheel center to the edge of the fender with 20" wheels. (Checking this way takes tire pressure and tire side height out of it.)
I am measuring the "old" way - from spindle center to fender. I remember when working on my E39 I would look up ride heights and stuff and it was all spindle center to fender. Looking up the F series now it's wheel lip to fender which I think is dumb. Now there's different tables for different wheel sizes in TIS and it only gives you measurements for the wheel diameters that platform came with. Easier to measure, sure, but ugh. I converted everything from multiple sources into spindle-center measurements and keep it in a spreadsheet with other working numbers.

I believe I will be raising my rear a few mm. I will probably also be softening a couple of clicks. I want to research multiple sources on tuning rebound and compression. I'm awaiting some advice from KW since altering ride height also alters pre-load.

I have some techniques which apply to bikes stating that rebound is a characteristic of vehicle weight (with occupants) and suspension and that there is only one correct setting which can be determined my test driving off of a drop. (best filmed in slow mo with a phone outside of the vehicle) Considering many lower tier adjustable suspensions are only rebound adjustable I find this interesting.

The same tuning advice says that compression setting is where "preference" enters, and where the real input on what the driver wants the vehicle to "feel" like comes from. I would want the dampers to break in a little more before doing any critical settings but it would be interesting to play with. I might take my rear speakers out and head out some time when I have time on my hands and do some playing. I'd have to see if I could come up with a way of reaching the rear compression adjustments while out on the road. I expect I could reach the fronts by turning the steering.

I'm interested to hear anything more from anyone regarding over/understeer following coilover installation - particularly KWv3s. With my E39 and E90 I could really just feel where things stood. The F10 seems a lot more complicated.
Appreciate 0