[Bee Pee]

My car spent the day with Chris and Pete at Center Gravity Atherstone this week. Great people and I learnt a lot from my time there.





My car's spec as follows:-

2016 M2 DCT with following oem chassis upgrades:-

- MPerf coilovers - installed by BMW and on BMW ride and damper settings
- -0.5deg front camber correction hub carriers
- 513m cw 245 & 265 F&R 40/18 MPSS tyres
- m4 alloy brace retrofit.[/list]
Initial test drive by Chris in comfort with DSC on around his test route to gauge any issues. This initial (and final) assessment drives were done in comfort mode with all the nannies on. Chris uses inherent DSC to gauge how effective the tweaks are ie more grip = less slip = less DSC intervention.

Outcome from 1st shakedown drive was slight right biased from both F & R, slight noise from NSR corner and traction control cutting in too soon.

Once back in their workshop the look closely at the tyres to gauge wear depth and wear patterns F&R. Fronts were fine and rears less rear camber, despite being in spec was too much such that outer shoulder was not being used hardly at all !!

Chris at Center Gravity focussed on getting the car symmetrical first then tweaking it to suit my preferences. Emphasis was on:-

1 - upping grip levels front (turn-in) and rear (traction).
2. - optimising road manner balance between fast road (bumpy) and track (smoothed) surfaces - Chris talked a lot about more compliance gives more control of tyre contact patches

Car was initially ballasted to BMW specs (75kg in both front seats) and then they check alignment and do first corner balance check - see below.

Initial alignment:-



Initial corner balance



Then, corner balance is re-done to suit my requirements. See picture below - as-is corner balance was almost spot on...



Chris then soften all the dampers to full soft and checks spring travel, damper stroke and bumpstops clearances in all 4 corners. Chris talked a lot about more compliance = more control.

Note - common problem on KW / MPerf struts - OSF compression adjuster dial at the bottom was very stiff to turn. Chris had to ease & tease adjuster and eventually it turned freely - he suggested regular turning of the comp adjusters from full hard to full soft then reset them on all 4 corners to remove any "stiction" within the strut/damper bodies.

Front ride height was fine @ 10mm clearance but at the rear the car was hitting the bumpstops under compression.

Two options to create clearance - raise the rear (which may happen to suit corner balance) and/or trim the bumpstops. We decided to cut 10mm off both rear bumpstops. Rear spring travel and damper rod stroke now had clearance, to be more effective to ensure rear tyre contact patch stays more constant more of the time....

Chris then sets geometry and checks corner balance and this is a re-iterative process until he gets alignment and corner balance correct

See below final settings -

final alignment



final corner balance



With all dampers full soft Chris remarked on how firm front springs felt, whilst he was compressing the front of the car. Understandable given they have the weight of the engine to cope with. Based his experience, Chris said too much support (firmer compression) on an already very stiff spring means tyre walls take a beating and keeping tyre contact patch consist suffers as a result.

Switching to 18" wheels means my tyre parameters (size/type/pressures) can have more influence, than 19". By this I mean, stiff springs/dampers and heavier 19" wheels with thinner sidewall tyres puts more emphasis on refining spring/damper setup. Had my car been on 19", Chris may have backed off both C&R even more to optimise front end compliance.

Different story at the rear, C&R was stiffened up as I have more wheel travel at the back after cutting 10mm off the rear bumpstops. Also, during initial shakedown drive, the rapid but tight turn test, the traction control cut in too early as rear pushed to try and wash front end out.

Chris juggled ride heights, alignment, corner weighting and damping responses. As far as KW / MPerf strut / damper settings, we talked about the principle of starting from softest setting and counting clicks to desired setting - this is too subjective as the softest setting is with flow control open ie piston full retracted from it's mating venturi. Instead, work on clicks from full hard ie fully closed position as this is way more definitive. Also, he advised try changing rebound only as far as road to track damper setting tweaks ie 2 less clicks from full hard F&R....

Post all the fettling, both he and I repeated the same shakedown drive incl the rapid, tight test. With DSC full on, the car gripped harder F&R keeping the car neutral and despite his & my best efforts, the traction control didn't intervene.

End game, as far as the car's setup, is now is what Chris referred to as "rapid slalom spec" ie the car can be pedalled equally L&R a lot harder with nannies active, yet they intervene a good deal less. Means forces/loads being imposed on the components at each corner of the car are being managed more effectively ie tyre patches optimised and springs/dampers working on a high plain.

Chris was right - down A & B roads, I didn't know too well as drove home, the car's composure and the road manners felt sublime ie more supple yet more focussed. Had an interesting tussle with a TTRS then a FRS. Neither could stay with me through a variety of twisties - grip from both axles has increased noticeably and DSC never flickered. When reducing stability control sensitivity ie MDM or sport + or DSC fully off, car remains more poised / consistent at close to or at grip threshold.

Once home, I took this photo showing the original scrub/wear line [approx. 1.25" away from the outer shoulder] within BMW spec for rear camber @ 1 deg 50' and the fresh scrub line right upto the edge of the rear tyre tread pattern [new rear camber -1deg 30']…



Hats off to Chris, he definitely knows his onions. I'm happy and looking forward to driving the car down roads I know and at the next TD's....

BP

[gphung]

Awesome detailed post. Must have been quite the experience. I planned on getting my car corner balanced, but I doubt the folks would've gone through such detail to dial the car in right. Glad to hear it behaves so much better now! DSC not engaging nearly as much now should also mean it'll save your brake pads from added wear.

[M Fifty]

BeePee - none of the pictures appear to be working - maybe just me?

[gphung]

Originally Posted by M Fifty

BeePee - none of the pictures appear to be working - maybe just me?

They weren't working in-line for me, but they all showed up at the bottom of the post. However, I don't see any of them anywhere in the original post anymore. I think there's an issue with the forums. Couldn't see pics in another thread earlier today as well. Mind you I've been strictly using the iOS app today.