Before getting to it, my 35i is fitted with 370mm front discs and calipers robbed off of an M4, the front suspension components are those off of an E90 series M3, plus a few rear ball joints off of an E46 M3/Z4M. Anti roll bars are also upgraded and it has a remap from Evolve Automotive. As the dealer had sold their M40i and only had the four cylinder car available I'll focus on the chassis comparison rather than the engine. More info on the modifications made are in these two threads;
viewtopic.php?f=23&t=110562
viewtopic.php?f=23&t=108512&p=1572606#p1572606
First off, the interior. At first glance, I thought 'wow' and am still impressed with the level of technology they've crammed into the car (HUD I love). Everything feels well screwed together (as you'd expect in a new car) and there's a lot of small touch points such as air vents and buttons that feel nicer than those in the old car. Upon closer inspection, there are a few things that weren't so impressive, firstly the leather on the dash is definitely not a better grade than the E89's, the plastic panel at the front of the soft top is an extraordinarily cheap feeling piece, similar story with the sun visors that are a hard plastic rather than the E89's leather trimmed ones. Lastly, I found the driving position to be very high even with the seat as low as possible. In traffic I was eye level with hatchbacks in what felt like a similar seating position rather than the low slung nature of the E89 and E85 for that matter.
My final gripe, and something I'm curious as the whether anyone else has noticed, is that with the roof up I found there to be a howling coming from the rear tyres, above 50mph especially I found it to be quite unpleasant. I don't know if this is something unique to the particular car I had? Sound deadening on the whole though is much improved over the E89 so this may be why one noise in particular stood out so much.
Onto actually driving the thing and in comparison the new car blows the standard E89 out of the water in almost every regard, to mine however it felt surprisingly close.
The brakes in particular feel almost identical, exact same solid pedal feel that can easily be modulated with plenty of stopping power in reserve. On the roads it doesn't feel like you're coming close to their limits at all. The pedal travel on mine is perhaps slightly shorter than the G29 but otherwise they're remarkably alike.
Steering on the new car is extremely quick and darty, more so than my VX220 in fact. It's extremely easy to quickly flick it into a corner and the lack of body roll combined with a very taut feeling chassis really gives you a lot of confidence to push it harder and harder. In comparison, the E89 takes a very small roll before the steering weights up and sets into a corner. The steering on my car is much, much heavier, normally I wouldn't call an E89's steering heavy however back to back the G29's felt like you can twirl it with one finger. Personally I found that when pushing on the light steering contributed to a slightly 'loose' feeling whereas the M3 components on the E89 seem to get tighter the faster you go and tells you more about what the car is doing, through the front axle especially.
Damping on the new car is definitely improved over mine, I don't have the adaptive dampers the demo car had although in all modes it soaks up lumps and bumps better than the passive dampers on mine which apart from the extra interior tech is probably the biggest improvement over my car. Larger profile tyres will also contribute to this and is something I'll look into changing on my car too, the G29's were 255/35 R19 on the front and 275/35 R19 on the rear, mine are 235/35 R19 and 275/30 R19. Neither car tramlines at all.
As my car is a manual, there isn't a real comparison to be had in the gearbox. The 8 speed auto is lightning fast and suits the car really well, shame no manual is offered but it is what it is.
An M40i is down on power compared to my car however the gearbox would likely bridge a lot of the gap. Both cars will cover ground at a serious pace, perhaps mine has a slight edge in outright grip but it's very close indeed. Both cruise in a sublime manner on a motorway (assuming the howling tyres was unique to that demo car) although the G29 is better at soaking up the bumps which I feel would pay dividends over a long trip on A-roads. I found the seats in both equally comfortable, I just wish the new car's seats went lower as it really does feel as though you're sat in a hatchback that happens to look like a sports car.
Overall the new car is hands down a much better car than the standard E89 and I wouldn't bemoan anyone for preferring not to go rummaging through the parts books of M cars to see what fits. Personally I don't feel the benefits outweigh the cost to change when my car drives just as well, whilst its not quite as refined over harsh roads it's more involving and communicates with the driver better. The new car is really very good indeed however, I'll continue saving the pennies for something else
