All - in an attempt to stimulate discussion for "OEM freaks" like myself who are interested in adding the GP trailing arms, I have copied this info from two posts of mine (from a thread in Marketplace) where I detail the research I've done. I just figured that other people would like to see it!

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I am (eventually) going to get the actual GP trailing arms for my JCW MCS.

I have done careful comparison of the "RR AXLE SUPPORT, WHEEL SUSP., WHL BEARING" sections between the standard R53, the GP and the R56... (courtesy of RealOEM.com)

And it became clear that the GP setup is truly a hybrid of the R53 and the R56... with some parts from each - however there are a few parts in that area that are unique to the GP alone, and the actual trailing arms are obviously the most significant of those.

I've even obtained a preliminary quote for the GP trailing arms, and no, they weren't cheap.

Anyway, for anyone serious about this, here's a list of the "UNIQUE TO GP" parts in that region of the car (based upon unique part #s):

33306777619 - REAR AXLE CARRIER (Qty: 1) - only different to allow for GP undercarriage aero parts, probably not needed
33306776315 - TRAILING ARM, LEFT (Qty: 1)
33326776316 - TRAILING ARM, RIGHT (Qty: 1)
33306776366 - HEX BOLT WITH WASHER (Qty: 2)
33306776365 - SHIM (Qty: 2)

Everything else either comes with the R53 or comes with the R56, which means you can obtain them easily from any MINI dealership.

 

Allow me to go a step further with parts info. The following parts are what you'll also need to order to match a GP (i.e. they do not come with the R53)... but these parts are easily obtainable because they are all identical (same part #s) as the R56:

--- From RR AXLE SUPPORT ---
33306770528 - HEXAGON SCREW WITH FLANGE (Qty: 2)
33326770089 - SCREW SELF-TAPPING (Qty: 2)
33306772665 - BRACKET, TRAILING ARM LEFT (Qty: 1)
33306772666 - BRACKET, TRAILING ARM RIGHT (Qty: 1)
33306768048 - HEX BOLT WITH WASHER (Qty: 2)
33326760374 - SELF-LOCKING COLLAR NUT (Qty: 2)
33306770138 - CAGE NUT (Qty: 2)
33326763265 - HEX SCREW WITH COLLAR (Qty: 4)
33326760668 - SELF-LOCKING COLLAR NUT (Qty: 4)
33326774032 - STOP BUFFER (Qty: 2) - comes with JCW suspension already
33506771928 - HEX BOLT WITH WASHER (Qty: 8)
12521437136 - CLIP (Qty: 2)

--- From STABILIZER, REAR ---
33506772789 - REAR SWING SUPPORT (Qty: 2)
31356757707 - HEX NUT WITH PLATE (Qty: 4)

--- From REAR SPRING, STRUT ---
33326771715 - SCREW SELF-TAPPING (Qty: 2)

So you see, with all of these parts that are shared with the R56, plus all of the "UNIQUE TO GP" parts, it takes quite a bit to get ALL of the GP hardware together!

In case you want to look through them yourself, here are the pages I used to extract these part numbers:

RealOEM.com - R53 Cooper S RR AXLE SUPPORT, WHEEL SUSP., WHL BEARING
RealOEM.com - R53 Cooper S JCW GP RR AXLE SUPPORT, WHEEL SUSP., WHL BEARING
RealOEM.com - R56 Cooper S RR AXLE SUPPORT, WHEEL SUSP., WHL BEARING

also...

RealOEM.com - R53 Cooper S STABILIZER, REAR
RealOEM.com - R53 Cooper S JCW GP STABILIZER, REAR
RealOEM.com - R56 Cooper S STABILIZER, REAR

and...

RealOEM.com - R53 Cooper S SINGLE COMPONENTS FOR REAR SPRING STRUT
RealOEM.com - R53 Cooper S JCW GP REAR SPRING STRUT COIL SPRING AND PARTS
RealOEM.com - R56 Cooper S SINGLE COMPONENTS FOR REAR SPRING STRUT

IMPORTANT NOTE #1: The R53 page I used above is for R53s built from 05/2003 onwards. If you have a very early model, you might want to do your own comparison and use this page instead for the standard R53. Apparently they made some significant changes to that area in mid-2003!

IMPORTANT NOTE #2: Since I haven't held them in my hands side-by-side, I do want to concede that it is possible that the R56 trailing arms are indeed 100% identical to the GP trailing arms. They certainly are very similar... but they have different part numbers. Are the different part numbers a deliberate ploy to try to prevent us from doing what we want to do? I don't know... maybe. Still, I will feel better removing all doubt and using the actual GP part numbers.

IMPORTANT NOTE #3: People with very late 2006 builds and have the new wheel hubs (same as R56) might need a slightly different combination of parts. My info above applies to the "usual" wheel hub size that the vast majority of R53s were manufactured with.

IMPORTANT NOTE #4: For obvious reasons, I have left out the GP shocks & springs in the comparison. Those are specifically weighted to the GP anyway, so would not be a good match for a regular R53. If you obtain the JCW suspension (the right way, using your VIN), then you will get the shocks & springs best suited for the weight of your MINI.

 

I'm in the middle of adapting R56 trailing arms to my early R53. In short, the only thing you can keep are the brake rotors, calipers, control arms, and rear subframe, everything else....no seriously, everything else needs to be replaced.

Honestly it doesn't matter what year your R53 is; early or later, you'll have to ditch most of your stock stuff and all your hardware. The exceptions will be the later ones starting in mid-03 with the new-style rear trailing arm bushing, however the screw and plate you use will be different.

The GP and R56 trailing arms are different, but the difference is subtle. They work the same and have the same mounting points. Their only difference I can tell is the castings themselves have different markings. The easy way to tell is the GP solid faces are smooth and the R56 has subtle cross-hatching. This cross hatching MAY be for structural reasons, but it's so low-profile I'm not convinced it's anything but cast-release assistance or perhaps some low-gloss aesthetic treatment.

The R53 sway-bar drop links are different than the R56's, as the casting of the aluminum is thicker than the steel. I found out however that you can make the R53 drop links fit if you shave the stanchion off the new trailing arm. Why that stanchion is there is beyond me, it's only a source for stress risers and to seemingly annoy R53 owners, LOL!

That's all I have to add for now. The total cost for the conversion is "about a grand", and that's sourcing from Classic MINI, who offers parts at 20% off retail. The actual trailing arms were about $220 each, however new style rear hubs are about $160 each, and then another wad for fresh hardware, ABS sensors, bushing mounts, Polyurethane inserts, and more hardware.

Much thanks to blumini for his help as a resource, as he's already done this conversion!


Cheers,
Ryan

 

Nice info, thanks Ryan. I do want to point out that the GP conversion can be done without changing the hubs, as all but the last builds of the GP came with the old hubs, at least according to RealOEM. Seems they switched over between 7/11/2006 and 7/12/2006.

Don't know why you'd need new ABS sensors?

 

OK, I'm still a bit confused on which hubs from when work where. Since my MCS is an early '02, I figured it was time for new hubs anyway.

Just for fun; what's the pricing on the GP trailing arms?

 

Look at the GP link that I posted above. It shows the date cutoffs... you probably could have stuck with the old hubs if you wanted to (although maybe not, since yours is before 5/2003).The price I was quoted was $625 each. I don't think that included shipping (from overseas), nor did it include the other "unique to GP" extras I put in my first post. $1250 for parts alone - not cheap!

 

Wow dude, that's $405 more a piece than R56 arms from Classic MINI. You need to reconsider the R56 arms!

 

Not me. But I haven't solidified on buying the GP ones from that one source, either... I'll be checking around. The fact that the GP trailing arms weren't on the MINIUSA embargo list when it was first published is promising... but obviously who knows, today!

 

Now that I've finished the R56 trailing arm conversion, I can address a few myths:

*All year hubs bolt up to the R56 arms. I kept my '02 wheel bearing hubs to keep my M12 wheel bolts, as I didn't want M12 front and M14 rear. You do need the new bolts from the R56/GP, as the aluminum arm is thicker and the bolts to bolt up the hub are much longer.

*While we're on the topic of bolts, you also need new bolts for the trailing arm bushing, and the lower shock mount. You can choose to re-use the bolts for the bushing to the body, and brake caliper mount.

*The R56 ABS sensor works correctly with my '02 wheel hubs. J Propane and I have been swapping PM's, as he seemed to have trouble with this and had to use his R53 ABS sensor, but the R56 sensor works perfect in my April '02 build MCS.

*You don't need any of the clips or ties from the R56; all the clips and ties in my '02 worked just fine to hold the ABS sensor wire. Just a few bucks you don't need to spend.

*I used Powerflex's polyurethane inserts for the rear trailing arm bushings. These are the "new style" bushings that are small purple rings, not the big yellow inserts of the old style bushing my '02 came from the factory with. The new style bushing has a different pivot point and seems to be a big design improvement.

*According to my bathroom scale, the difference in weight from Me+R53 trailing arms and Me+R56 trailing arms is about 6 pounds each, for about a 12 pound savings. This is probably +/- a pound or two.

I hope that helps!
Ryan

 

Good post Ryan - very informative!

 

Besides the documented 12 lbs weight savings what is the

functional difference between the older R53 trailing arms

and the new R56 trailing arms after this $1000 conversion is done?

 

There are two main functional differences:

#1: The 12 pounds is mainly sprung weight. This means your suspension has much greater resolution, and works much better than the old heavy welded steel trailing arm.

#2: The redesigned pivot of the trailing arm is a much better design. It is more linear, less binding, and uses a more robust bushing carrier design. This equates to not only better reliability, but also a smoother trailing arm articuation, resulting in more resolute suspension action. I haven't had a chance to drive my MINI in-anger since the install, but quick trips around town demonstrate the rear end of the car is much more precise and also more predictable than the old setup.

FYI: The conversion doesn't cost $1k. It's more like $700 if you use your existing hubs. I didn't do an exact price B.O.M., so I'm only in the ballpark here.

Cheers,
Ryan

 

Anyone know how much to torque all of the self threading bolts???

I'm sure the torque values are different since most of the bolts thread into the aluminum arms Vs. the steel nuts on the R53 arms.

I have all the parts & need this info before starting the project ; )

 

I don't have any exact values, unfortunately. I only have my intuition from experience of how much approximate torque based on material, hardware size and grade.

 

Thank you for your feedback Ryephile : )

 

I'm looking into this right now Ryan and I will probably make a call to classic this week. Is it allright if I call you if I get stuck along the way?

 

I have updated my second post to reflect a few additional parts differences, including the aforementioned bolt. All of the additional parts are also on the R56, they are not GP-unique parts.

 

nice thread.....full of information. can someone who has done this mod comment about the change in wheel.tire clearance. i seem to remember someone saying that clearance increased and another said that clearance decreased. i run as much tire as i can stuff under the car with my track setup and would like to know.....

 

The Feb 08 NAM Alliance Magazine has a full writeup with step by step directions and a full parts listing written by Ryephile.

 

Edge have you actually made a purchase of any GP parts @ all.

you know Mini parts group puts a national freeze on GP parts. You have to have a valid Vin# and Registration / in order to make a
purchase. Have you been pass all this or inquired into this. I know someone was trying to purchase a GP intercooler @ 1 time. Without a Vin he could not do anything. I was just curious if this has happened to you.

 

Yes, obtaining GP parts from USA dealerships is tough... because MINIUSA has made the decision to deliberately keep the parts restricted, to prevent us from doing exactly what we are trying to do.

Do I have any GP parts? Yes... (see my sig!) but not the suspension parts (yet!).

 

all I see is a bunch of letters

 

How much weight do you loose with the R56/GP trailing arms and is their any other improvement in performance from installing them?

 

LOL... except that my signature takes up less vertical space than yours... So who is contributing more to "what's seen on the screen is not content"? Per Ryephile's posts above (#9 & #12)... 6 pounds each and yes!

 

Could you expand upon that yes?