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.

  • There has been quite a bit of debate on wether this thing actually doesn anything or not. An underbody brace, like the TSW version (before they went out of business), always made more sense to me…

    Anyway, I have a four point rollbar, and that definitely does make a difference, I suppose this contraption may help a little.

  • BilboBaggins

    I’m with you Brenden. I’ll wait for the ‘X’ shaped version.

  • BilboBaggins

    Sorry, Brendan

  • Didn’t I read this very same article last week? If this isn’t a repost I’ve got a severe case of deja-vu going on.

  • hemisedan

    Right, it seems that I’ve read about this about three times in the past week or so. What gives?

  • ScottinBend

    It doesn’t even come close to the suspension points, so what possbile good does it do…..?

  • Rocketboy_X

    If you were unaware if the bar was in or out, would you notice a difference? Or did you just put it in your car and notice a ‘difference’?

  • As mods go, this would be relatively low on the bang for the buck scale. Like, maybe at the very bottom…

    I seriously doubt it would be noticeable on an everyday driver, IMHO it really doesn’t make much sense on a street driven car, especially when there are so many other relatively cheap mods that do.

    On the track MAYBE it would take out a small amount of chassis flex that MIGHT be noticeable. But then again, I seriously doubt that this would be the first choice for a tracked MINI–a harness bar, or better yet rollbar, would make more sense in that situation.

    The more I think of it, this is one of those mods that fits the category of a modification in search of an application.

  • ScottP

    Summer re-runs?

  • Didn’t I read this very same article last week? If this isn’t a repost I’ve got a severe case of deja-vu going on.

    There was an issue with our software and this indadvertedly got posted for a few minutes on Friday.

  • MKH

    More like a modification in search of a sucker with an extra $279 to throw their way for little benefit, other than a bar that blocks full use of the MINI’s cargo capacity.

  • Axel

    well as usual SKEPTICISM as its best. M7 products or any other product from whomever you feel justified to buy do their purpose either it be for fun driving or to just show off at someone. Spend your money for what it takes. I have personally bought from M7 many parts for my 02 MCS and they are still there 124k’s later. I personally know Peter and I back his products. NO amigos, he does not sponsor me or whatever ok. If you dont like the product JUST dont buy it I have only bought what is deemable to me therefore I have spent my money wisely. BTW, if you get to read this, Pete. when are you coming down here to Puerto Rico to have a couple of Medallas(local beer from Puerto Rico) 😉

  • Axel, I don’t have anything against M7–they do have some good products that several reputable vendors endorse–this just isn’t one of them.

    The problem in the MINI world is that people see parts, think they’re going to dramatically enhance performance, buy them, then defend them to the death, when there’s little data to support that the particular part or modification actually is of any benefit. Personally, I think the rear chassis brace gets close to that.

    Now if you’re buying it for the way it looks, then that’s fine–but if you’re buying it for some dramatic improvement in performance (especially on an everyday driver), then I think that’s a stretch. And there are better parts (including some by M7) to stiffen up the chassis…

    This site gets ALOT of traffic. Anything on the front page will get alot of hits. IMHO, the original article was a little overexuberant on what this brace actually can do–it’s just my 2 cents, maybe in reality it’s only worth one cent, take it for what it’s worth…

  • Greg W

    If this was absolutely necessary surely the MINI design engineers would have built this into the construction. For normal road users (those who drive within the law and limits) any difference would not be noticed. A fool and his money are soon parted.

  • PretzelBurner

    A simple strain gauge or plastiguage strategically placed should measure deflection and silence all naysayers or proponents no? Not sure how its bolted up but bolt up one side, on the other side put plastiguage between brace and body, take a couple runs trying for your personal best at highest G, see if the plastigage compressed OR not.If mounting points are too tight, move towards using a strain gauge. OR fab up an x using the same mounting points (but don’t connect the bars), measure deflection where the bars cross. You can use a simple digital dial gauge to capture max deflection if its great enough.

  • goat

    @ GregW -That is the typical comment of someone who drives in a, shall I say, “staid” manner. Stiffening a chassis is one of the best things you can do for any car. Strategically placed members can make a very notable difference to the sporting driver, even on the street and within “law and limits” that you seem so pleased about. Not just cornering but stiffness over railroad tracks, poor pavement etc. always helps the suspension do a better job of controlling body motions + optimizing road traction. Squeaks and rattles are typically reduced with a stiffened chassis as well.

    Remember that the same MINI engineers that you hold in such high regard also send cars on their way with soft and high-riding suspensions (R56 jcw included), so don’t assume the cars cannot be improved by good aftermarket engineering. In the interests of compromise for “typical drivers” – many of whom are not as enthusiastic about performance or value other competing design criteria – the factory ALWAYS leaves something on the table Having said all that, I agree that the design of this particular bracing system is not optimal. It should have a diagonal member… the cargo excuse rings weak here. But the key thing is to tie the rear shock towers together laterally and this does do that.

  • ScottinBend

    It does not attach at the rear strut towers. It attaches to the interior body shell at the rear seat latches, not an optimum location by any definition.

    This is a very poor attempt at rear body stiffening.

  • goat

    @ScottinBend – looking at the photos again… ouch… well then… 2 strikes against the design: (i) lacks a diagonal; (ii) doesn’t attach to the strut towers directly. 🙁

  • Alex

    I con’t really comment on their products’ quality as compared to other brands, but I can say this: If you expect quality customer service, DO NOT ORDER FROM THE M7 WEBSITE!!! I ordered an item and specifically selected the rush overnight shipping. I wrote right in there, saying that the shop was already in posession of my car and that the part needed to go out ASAP. When I completed my order for OVERNIGHT shipping, the site confirmed my order and told me it would be delivered within 3-5 days! So I sent an e-mail to the customer service address, and 3 days later, got a reply saying they were out of the item and it would ship at the earliest, a week from then. When I asked about a discount or at least a refund of the shipping for the inconvenience, I was told that they did not want to do business with an “unreasonable” customer. Mind you, the website said nothing about the item being out of stock, and I was left with a dis-aseembled car for a week. Ordered a competing product, and got it the next day. The M7 team has a lot to learn about customer service!!!!