E92 – Suspension Modifications


By John Thorne – Thu, 01 Oct 2009 08:00

Well thank God for that, we’ve finally managed to fix the E92 M3’s biggest problem – handling. Now I’ve been fairly critical of the E92’s handling in general, indeed the standard car on standard suspension I think is just way too soft for a sports car that the M3 represents but it does reflect BMW’s seeming intention to re-classify the car as more of a GT car. For me, if I wanted a mile munching BMW GT car I’d get an M6, for me the M3 represents the hard edge sporting end of the M range and the M3, on standard suspension just doesn’t cut it.

Moton_E90_Web_002.jpgMoton E92 M3 Shock Body” width=”200″ height=”133″> Moton E92 M3 Shock Body
Moton_E90_Web_006_2.jpgE92 3 CSLCup Safety Car on Thorney Motorsport Alignment Rig” width=”200″ height=”133″> E92 3 CSLCup Safety Car on Thorney Motorsport Alignment Rig
Moton_E90_Web_004.jpgLarge range of adjustment from the Moton 2-Way kit” width=”200″ height=”133″> Large range of adjustment from the Moton 2-Way kit

The main problem is complete lack of feel, the front end just doesn’t communicate the road back to the driver as the old E46 model does, the steering feels overly power assisted further robbing any kind of driver feel  and the whole thing feels, well, remote. There is grip, lots of grip, but it’s coming from the tyres rather than from any kind of chassis dynamics. Now this is a surprise as the E92 chassis is as stiff as a stiff thing, indeed BMW quote it as being 25% stiffer than the previous model and I’ve no reason to doubt that but this increase in stiffness doesn’t appear to manifest itself in actual road driving.  The rear end of the car is relatively quick to unsettle (which is fun) but once unsettled is hard to get back under composure so ultimately it makes brisk progress difficult especially in higher speed corners. On very bumpy roads the cars poise is pretty good, smaller bumps are nicely ironed out and over B roads the car is surprisingly quick considering its size but it always feels like its driving you rather than the other way around.

Moton_E90_Web_005.jpgMoton Springs by Eibach” width=”200″ height=”133″> Moton Springs by Eibach
Moton_E90_Web_003.jpgMoton E92 M3 Shock Body” width=”200″ height=”133″> Moton E92 M3 Shock Body
Moton_E90_Web_001.jpgMoton E92 M3 Shock Bodies Front & Rear” width=”200″ height=”132″> Moton E92 M3 Shock Bodies Front & Rear

In comparison the E46 always felt as if it was the driver making the decisions and not the chassis. Typical British A roads seems to be the M3’s nemesis, relatively smooth but the usual bumps and crests that we’ve become used to quickly make the car feel unsettled and fidgety and the overall feeling is that once you’re at the limit you aren’t likely to take it much further, overall the car feels under sprung which is quite typical of most manufacturers cars.Now at this point I have to make a distinction between cars fitted with EDC and no EDC. EDC is BMW’s Electronic Damping Control where the shock absorbers damping is electronically controlled via a button on the dash. Different settings are offered where the damping is firmed up in Sport mode and softened in comfort mode.

Moton_E90_Web_007_1.jpgAt Thorney Motorsport we go beyond manufacturer tolerances in Geometry setup.” width=”200″ height=”133″> At Thorney Motorsport we go beyond manufacturer tolerances in Geometry setup.
Moton_E90_Web_009_1.jpgE92 M3 CSLCup Safety Car at Silverstone” width=”200″ height=”133″> E92 M3 CSLCup Safety Car at Silverstone
Moton_E90_Web_008_1.jpgE92 3 CSLCup Safety Car on Thorney Motorsport Alignment Rig” width=”200″ height=”125″> E92 3 CSLCup Safety Car on Thorney Motorsport Alignment Rig

If you are looking to spec/buy an E92 M3 and have no plans to track the car or upgrade the suspension then certainly spec the EDC. EDC equipped cars are far more superior in handling than non EDC cars (ours is non EDC), the sport setting offers far greater feel overall and is certainly more involving than the non EDC cars, its still vague in terms of steering feel and still nothing like as good as a CSL but its a lot better than non EDC. However, get the car on track and EDC is still way too soft to really be able to cope, although an Eibach lowering spring kit does help both the look of the car and the poise albeit at the expense of some slow speed ride.The Performance BMW bods only give me a couple of pages for these articles and frankly you can fill books talking about suspension and handling so I have to keep the following a bit short and sweet but generally a cars handling characteristics are made up of three things (four if you include the driver).

Firstly the cars chassis (which I’ve already touched on) has the most effect, its stiffness and how it reacts to the road are the foundation upon which handling is based. Secondly the cars suspension set up, components, design, dampers and springs and finally the cars geometry, the set up the car has in terms of toe, camber, castor etc.The only real way to change how the chassis works is to fit a roll cage (which we will do when we prepare this car for racing for next season) and not many people are likely to do that for their road car so we’ll cover that at a later date, same applies to the sub frame assemblies, lower and upper wishbones, track rod ends etc.

The main area that we can change relatively easily for a road car is the suspension and anti roll bars and of course the cars geometry so I’ll concentrate on that.Suspension is made up of two components, a spring and a damper and they both work in unison to control the cars up (rebound) and down (compression) movement on the road.  The spring (we’ve not done a shot of a spring on the basis that if you have the intelligence go into a shop and buy this magazine you will know what a spring looks like) is responsible for keeping the car up off the floor and controlling the overall height and speed of movement and the damper (which is the really clever bit) controls how and when the spring reacts.

There are a variety of damper designs from mono tube to dual tube to oil and gas but they all work essentially in the same way, fluid/air is moved from one chamber to another to control the speed of up and down movement of the strut and the speed of this transfer is what controls the speed the spring moves up and down. Without damping a spring (once compressed) would extend without any control, this is manifested when you lean on a corner of a car and it bounces when you take your weight off when the dampers are knackered so its the dampers that control what the spring does, compression (compressing the spring) is controlled by the damper by dictating how quickly the spring starts to compress and rebound is how quickly the spring extends.

I can go in reams of information about high speed and low speed damping, remote reservoirs, helper springs, progressive spring rates but four pages is not enough so to keep it simple I’ll concentrate on compression, rebound and springs.We’re often asked which suspension is ‘best’ for a car and the short answer is that we’ve not found one supplier that can do all of it, suspension is about hours of research and development, time in the cars on road, track, in competition and no one supplier is good for every application. We’ve worked with a lot of suppliers, KW, Nitron, Bilstein over the years and each one offers the best application on different cars, however for the E92 M3 we tried something different – Moton.

Moton is a name racers will be familiar with, the company’s heritage in BMW racing is legendary including helping Andy Priaulx to five World Touring Car Championships in his BMW 320si their suspension is literally the very top of the tree in terms of quality. We first tried their suspension on my CSL Cup race car. Jerome (owner of Moton) watched my in car video from Brands Hatch and simply said “we think we can help, why don’t we send you a race kit to try, if you like, you buy, if you don’t like then send back, no problem.” (He’s Dutch but doesn’t really sound like a meercat from the adverts). We were having trouble getting the camber we needed on the Cup car so we thought, what the hell, can’t hurt.

Two days before the Donington rounds of the CSL Cup the Moton suspension arrived, and we were astounded by the quality. CNC machined struts, roller bearings, multi adjustable top mounts, my race team manager had to be pulled away from the adjustors as he whimpered “Awww, just feel it, the smoothness, the clicks.” He does need medical help now we have decided. The sheer lack of weight was amazing. With only two days to go we literally chucked it on, set up the geometry and set off for Donington Park. First race I got second (not bad considering we had to stop and re-start the engine on the grid due to a miss fire) and in the second race we won by nearly 14 seconds, er, wow.

The race car felt utterly planted, Craner Curves could be taken flat and still get over for the old hairpin and the chicane (we ran on the GP circuit) was a delight to flick in and out of, the car felt stunning. If you want to have a look, check out the in car video on www.cslcup.co.uk. Funnily enough we’ve now bought the race suspension, he’s a cunning bloke that Jerome.So with the E92 M3 project in full swing and us being utterly fed up with the crap handling we decided to try Motons road kit. Moton is relatively new to the road car market, its racing history is without question but to transpose this skill to road cars is not as simple as you might think. So, it was with open minds we fitted the first E92 M3 kit ever in the UK.

Opening the box we were met with the same quality manufacture as the race kits (which cost nearly £6k), the same bearings are used as in the race kits along with same struts and platforms, the seals are different to cope with road salt and grit and there are differences to finish to keep the units looking good after road neglect but pretty much they look the same as the race kits. Constructed of steel and aluminium the kit we got was the two way adjustable kit, this means that the bump and rebound are adjustable separately which is perfect for a road/track car.

My race car runs three way adjustable which means compression adjustment is separated into slow speed and high speed meaning we can dial out high speed bumps separately to low speed (the speed relates to the damper not vehicle speed) but this is a bit overkill for a road car, even one that goes on track a lot.Being the first kit in the UK meant we had a few minor issues with fitting which we sorted with Moton easily enough and the kit went on the car with relative ease. Now’s a good time to talk about geometry I guess. Putting on fancy suspension is all well and good but it’s the vehicles geometry that can make the biggest difference to a cars handling. Manufacturers have to set the car up with an eye on compromise, keep it more understeery for safety, minimise tyre wear for the bean counters, ensure ride height will cope with Chelsea Road kerbs etc. What we do is throw all that compromise out the window and set the car up to maximise its handling whilst at the same time trying to minimise tyre wear and comfort).

We do this by adjusting the vehicles ride height (either by springs or suspension), toe, camber, castor and trail. Now, you could read book after book about geometries and still be learning (I still am) so I’ll keep this short (damn this 4 page rule they hit me with). Toe is where the tyres point out or in (stare down at your feet when standing up, they will be toeing out (unless you are really weird), camber is the angle the tyre touches the road (cars tend to run negative camber, ie the top of the tyre is nearer to the chassis than the bottom) , castor and trail relate to the angle the wheel sits relative to the axle. Now exactly what we do to improve the handling of the E92 is built on hours and days of road and track testing so I wont be super accurate here as it’s a competitive advantage but generally we increase negative camber, increase toe on the front and decrease toe on the back to improve a cars handling (rear wheel drive anyway).

We have to be careful not to go too far as an overly aggressive set up will increase tyre wear quite dramatically but even a few minor changes can have a huge effect on how the car handles.So, we’ve uprated the cars geometry, we’ve changed the standard springs and dampers, whats it like?In short, blimey (I’d say something a bit more dramatic but the PBMW bods have already warned me for course language) what I’d like to say is “oh my f*cking God this is f*cking fantastic” but I think by now you get the point. I was starting to think that we were never going to get the E92 handling sorted, that it was always going to be a compromise until we went to full race spec and that we’d been beat. We’ve been trying a variety of suspension suppliers on the car and always came back to the same conclusion, that the car needed very good quality damping to make the use of the springs. Well, we finally have it.

Initial road work is a revelation in terms of steering feel, the car is properly weighted and gives a lot more resistance to steering input; you finally feel connected to the road via the front wheels. At the rear the extra grip is immediately noticeable, body roll is still evident but it doesn’t affect grip in the same way the standard car suffers. Under acceleration there is less fore/aft body movement so the ride actually feels more comfortable even though it is firmer. On UK A roads the feel is much more planted, the car feels a lot like my old CSL now with the extra weight hidden from the handling and the overall feel. B roads (especially the really bumpy ones round where I live) are a firmer affair but it all feels nicely suspended as if you can feel the dampers working with the chassis rather than trying to cope with it.

On track the improvement is even more dramatic, the E92 is a big ole’ car so its turn in and mid corner poise is hard work but the Motons allow a far more aggressive style to be used that maximises both fun and minimises lap times. Donington Park on a BMW Car Club day highlighted the only weakness now – lack of harness or decent seat, I spent most of the time in the seat hanging onto the steering wheel!We’ve still more set up work to do and it would be nice to do a full report just on geometry set ups but for the moment we’re off looking at seat replacements, these just don’t cut it for work on track.
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