MF Review: M7 Rear Chassis Brace

The stock MINI out of the box has a remarkable stiff chassis. But, that’s not going to stop aftermarket accessory makers from trying to make an even more rigid car. That’s where M7 Tuning has worked their magic. Gabe previously reviewed the understrut system by M7 here on MF, and so this is my review of their rear chassis brace.

For you suspension geeks out there, I thought I should establish where I’m coming from on my 2006 R50. I have a Sport Suspension Plus set of springs and shocks from an early 2003 MCS (before the suspension was softened), front fixed camber plates and a SS+ rear sway bar. It’s stiff and a whole lot of fun. Turn-in is quick and I can induce a smidgen of oversteer either by lifting off the throttle and trail braking. No other FWD car I’ve driven is as responsive.

The rear suspension on the MINI is surprisingly sophisticated for a car of its size. The multi-link setup still sets the MINI apart from other cars in its class like the Nuova Fiat 500 (torsion spring rear axle) and the VW Polo (semi-independent). The problem is that there is no good place to brace the rear of the car in order to eliminate flex. But, thinking outside the box, M7′s solution is a brace which goes in between the two latches for the rear seats.

Unpacking the parts and pieces was a fairly standard procedure. Everything arrived in bubble wrap, nuts and bolts were packaged in a compartmentalized plastic baggie. M7 is even kind enough to include two allen wrenches to aid installation. Not included were a 10 mm wrench, a 13 mm socket and paper instructions.

The build quality of the parts was impressive. The most impressive piece was the top bar; a hollow black anodized aluminum bar with specially manufactured ends which bolt to the chassis. It’s too bad that this product likely won’t be seen by most passengers because it’s really nice. The engineering was to impressive, tight standards and everything fit together with very little tolerance. M7 says that this is ‘pre-tensioning’ and aids the overall effectiveness of the system. The side pieces attach to the bottom of the chassis, utilizing hooks normally used for strapping down cargo. One cross beam keeps these side bars stiff at the bottom.

Installation took me about 45 minutes at a careful pace. When it’s assembled it becomes even more apparent how much homework M7 did on this product. Although the top bar bolts on behind the rear seats, the RCB does not affect their operation one iota.

And so, I took to the streets. Driving up one of my favorite local roads immediately made the brace’s effect known to me. The rear end of the car feels like it’s one solid piece, and I could feel the vehicle rotate around me more in turns. It’s a subtle trait that doesn’t disrupt day-to-day driving and is only of use in more spirited driving situations.

My only qualm with the product is the fact that the shape the braces create is a rectangle, one of the least rigid geometric shapes. This is because it’s all too easy for a rectangle to be shifted into a parallelogram, diminishing the absorption of force from its corners. And given that M7 was likely trying to strike a compromise between functionality of the brace and cargo space, I can understand which shape they chose for the brace. However, there is a pretty good chunk of passthrough cargo space which is eaten up by the RCB even with this compromise. I would prefer to see the next iteration of this design consist of two bars crossing (creating an ‘x’) attached to the top brace for an even more hardcore level of chassis stiffening.

MotoringFile Rating: 4 (out of five)

Where to Buy: The M7 Rear Chassis Brace is available from M7 Tuning for $279 plus shipping. I tested the R50/53 version, but there is also a version available for the R56.