I’ve owned my new-to-me 2008 justa Clubman for about 2 months; this is my first post.

I’ve got a few changes that I’d like to make, and as a starting point I like to do things that reduce the effort of the vehicle going down the road (less drag, less mass, etc) before making additions.

One of those changes, which turns out to be an addition, is the underbody panels. From what I can find, these appear to be installed on all of the European cars, but not the North American ones. They are listed for all of the European models from the Mini One Coupe to the JCW Clubman on the RealOEM website. I hate guessing, but it must have something to do with the European extra-urban fuel efficiency and CO2 emission ratings that aren’t part of the equation on this side of the pond – so we don’t get the panels.

I haven’t been able to find much hard data, but just today I see that MINI USA is now listing drag coefficients for the 2012 models:

R55 Clubman 0.32
R55 Clubman S 0.34
R55 Clubman JCW 0.34

Short wheelbase cars for comparison:

R56 Hardtop 0.33
R56 Hardtop S 0.36
R56 Hardtop JCW 0.36

I don’t believe that the 2012 US models have the underbody panels, do they? I don’t know if the above figures are applicable to previous years, but there don’t appear to be any major changes. MINI UK, France, and Germany don’t list the drag coefficients on their sites (that I could find), so I haven't been able to find any values for cars that do have the under body panels for comparison

Another bit of data is that the R53 GP with underbody panels, side skirts, rear wing, etc dropped the reported cd from 0.39 to 0.348. That’s a 10% reduction even with the addition of the rear wing which likely added drag but reduced lift.

So, I’m thinking that the underbody panels would be a good addition; especially since 80% of my driving is at highway speeds. But the factory panels for the Clubman are stubby little things that just cover the fuel tanks ahead of the rear suspension.

http://www.realoem.com/bmw/showparts...48&hg=51&fg=75

The panels for the Hardtop extend from the front suspension all the way back to the rear suspension.

http://www.realoem.com/bmw/showparts...84&hg=51&fg=75

I would think that the full panels have got to do a better job of cleaning up airflow. I’m not sure why the Clubman has short panels, but I’m thinking of sourcing a set of the full length panels from the short wheel base cars, cutting them side-to-side, and splicing in a 3.5” section of ABS plastic to stretch them out so that I’ve got full length panels on the Clubman.

Other than the longer wheelbase of the Clubman, everything else seems to be the same under the car. The front doors are common to both versions, so the wheel base length addition should be in the area of the club door aft of the B pillar. If anybody can think of a reason why this might not work, I’d appreciate your thoughts.

Thanks,
John

 

My thoughts are that I'd like to be your first customer and pre-order two for his and hers...

As a bicycle racer who races against the clock, a reduction of this magnitude would be massively significant!!

Chapeau!!

 

I haven't looked into this much, but is there any chance that the short panels for the Clubman are used in addition to the parts for the shorter cars?

 

I raised the car up yesterday to put on the snow tires and had a look underneath at the mounting points for the panels. As it turns out all of the mounting points for the full length panels. Most of the attachment points are threaded studs about an inch long extending down from the floor.

I'll check with the dealership Monday to see how much the panels cost and if they are available. I've seen others attach them to the R56 in the US, so we should be able to get them. I doubt the price will be as good as shown on the RealOEM listing though.

The RealOEM site only shows part numbers up through 2010, so perhaps there are now full length panels for the Clubman. However, I expect not, and I think I'll need to do a bit of cutting and splicing to make the shorter R56 panels fit the R55.

From photographs I've seen I don't think the stubby R56 panels are in addition to the R56 ones.

 

One thing you really need to reduce is the drag that is caused by the rear bumper underneath the car. Not many of the kits from MINI work on that factor. You need a rear Diffuser to take car of that problem.

You may want to check out Group4 Autosports before you make a decision they have some really nice under car and and diffuser kits available.

http://www.group4autosport.com/Home_Page.html

 

Schatzy 62, thanks for the link to Group 4. Yes, I agree that a rear diffuser will likely help, or possibly offer the greatest benefit. That might be the next project, but I want to reduce as much turbulence as possible prior to the air reaching a diffuser, so I thought I'd start with the flat under panels first.

A rear diffuser has been done for a Clubman before too. Here is a link to some photos of the Mini Challenge Clubman Safety Car from 2008:

http://www.motoringfile.com/2007/10/...ge-safety-car/

I ordered the R56 panels from my dealer yesterday and should get them in about 2 weeks. I'll update this post with some pictures after I get them and install them.

John

 

Hey Minimist,

Just curious, what did you end up paying out the door?

And where is your dealer?

Thanks,

Claus

 

Cool idea... I wonder why the Clubman has lower Cd than the hardtop. I also wonder if some coast-down tests would show an improvement with the panels.

 

I read an article about that. The Clubman has lower Cd than the hard top because it is longer.

Dave

 

I figured it may have something to the added length. I wonder at what length the surface friction overcomes the advantage of additional length... a la a teardrop shape being inferior to a kammback.

I also wonder what difference the spoiler differences make. Hardtops tend to have 'taller' spoilers.

Btw, I don't suppose you know where I might find that article?

 

MadDane,

My dealer is Mini Yaletwon in Vancouver BC. The price that I agreed to was $83 per panel and $13 per rear mounting bracket. That's Canadian dollars, which is pretty much at par with US at the moment. They wanted another $40 for the nuts & bolts, but I figure I can pick that up for probably $4.

Blainestang,

I'm planning to do a before and after coast down test, so we'll see if it makes a difference.

 

It's a squat, stubby nose car. I finally got over it, and stopped worrying about it. If I have to push a bunch of air out of the way, so be it. It's worth every molecule of air I displace!

 

I would really like to know as much about this as possible. Have you installed them yet? pics?

 

+1

 

Yes would love to see the results. Lots of pictures of the install would be great too!

 

Yeah, sorry I haven't updated this thread. No, the panels aren't installed yet. I've just about finished modifying the panels so they'll fit the Clubman. I was originally going to just splice in a flat piece of ABS, but decided to add all of the stiffening contours of the factory panels to the splice pieces. I'm out of town for work, so I'll post some pictures when I get home in a week and half. And hopefully get them installed within a few days after that.

 

Don't forget about us Minimist! Awesome thread! Very curious to see the results. Also having a cooper and a clubman, for sure the clubman gets better highway mileage than the cooper because of better Cd. it is much heavier. It would be nice to even the playing field.

Let us know how it goes!

 

+1

 

any news on this?

 

Damn I'm slow at getting things done!

Here's a pic of the modified driver's side panel with the 80mm splice added. I had to make a mold to bend the abs plastic to the same contours as the factory panel with a heat gun. It's not perfect, but close enough for under the car. I made tabs with the abs that are riveted to both sides to hold the splice in place.

I need to rivet the other side together and then mount them. At my pace that should only take me another year!

 

thanks for the update. looks good

 

Very nice. Molding the splice section to match is a really nice touch.

 

I installed the panels a few weeks ago. Do they work? Well, it appears so. I filled the tank this morning and and my mileage is better than I've recorded in the past. I typically get about 6.6 l/100km (35.6 USmpg) combined, but this tank was 6.1 l/100km (38.6 USmpg). I think there's more going on here than just the panels (warmer ambient temperature, summer tires - even though the winters are LRR, and maybe a lighter touch on the go pedal), but I'm encouraged by the results. I started working on the rear diffuser template on the weekend.

 

Pictures please!

 

Here are some details on the rear diffuser, if I can call it that. Typically rear diffusers seem to have strakes fore to aft that are supposed to channel and smooth the airflow. These strakes will also stiffen the panel. For the moment I’ve chosen not to use these so I just have a flat panel.

It is made of coroplast (that’s one trade name) and measures 39” wide x 32” long. It’s very light weight and seems stiff enough for the job. I cut out the section under the muffler and added a piece of aluminum flashing that I painted with black high heat paint and riveted in place. I think this area is too close to the muffler for just the plastic.



Typically rear diffusers seem to be at a steeper angle, about 10 degrees. Of course there are trade offs; the steeper angle is supposed to help reduce lift, but a shallower angle is better to reduce drag. I’ve read that the best angle to reduce drag is about 2.5 degrees. The angle on the Clubman from the forward attachment point on the extended factory panels to the rear bumper cover is 4 degrees. Fitting a steeper angle one on the Clubman isn’t really an option anyhow, unless you wanted to remove the wheel well for the spare, and cut out the lower section of the rear bumper cover.

Here it is installed. The forward edge is attached to the factory centre panels with 4 #8 stainless screws each side through the 4 mounting holes in the factory panels. The rear edge tucks up under the bumper cover and is held down with one #8 screw on each end. So I’ve only drilled two 1/8” holes in the bottom of the rear bumper cover.



Here is a close up of the forward edge where the exhaust turns from the centre tunnel to the right side. I cut out this area to give it some clearance, but didn’t use any heat barrier. The exhaust pipe curves upward here so there seems like plenty of clearance.



The two angled slots on the sides allow the lower control arms to clear. I just copied this from the factory R56 Challenge rear diffuser pictured below.


So far so good. At least it hasn't flown off at 100 kmh

Pictures are in my gallery too.