I am getting closer to having all the parts for the GP / Aluminum Rear Trailing arm conversion to my 2006 MINI Cooper S (daily).

So a little back story for those of you that dont know about this, the GP1 came with Aluminum Rear Trailing Arms saving about 11 to 12 lbs of suspension weight, its not a hard conversion and if you are super lucky it can be done on the super cheap. The conversion is done by getting a set of R56 Aluminum Rear Trailing Arms. See attached photo for the needed parts.

You move your Brakes and Wheel Hubs over to the new Trailing Arms. So if you find a damaged or parts car at the Salvage yard you can get +95% of the parts there, you will need the steel adapters to adapt the rear shocks these are available from Way Motor Works and Allmag Parts (both sponsors here).

After that its a simple unbolt the old stuff bolt on the new stuff, and be rewarded with a much quicker suspension recovery on the rear.

I am adding to mine (since I have the time and the parts are out the PowerFlex Rear Trailing Arm Bushing kit, see photos of that installed when I did my other 2006 MINI JCW MCSa, I dont drive this one as much anymore I am working on preserving it.

So done so far to the car:

Wilwood Front Brakes
R90 Wheels with New Summer Tires
Racing Dynamics Header
JCW Exhaust
GTT Stealth Intake (basically a JCW intake without the flap and looks stock)
COMPLETELY new JCW suspension (I mean everything Bolts, Mounting parts, Shocks and Springs) car had coilovers I hated them.
New rear EBC Red brake Pads
New rear anti-roll bar bushings, the old one were shot, (when I got the car it had a 25mm rear bar.
Added Boost Gauge
Added Audiovox iPhone interface and Promount Phone Holder

Still to finish up:

The Rear Trailing Arm conversion (obviously)
Install the 380cc Bosch Injectors
Install Oil Catch Can
Install the LinkECU and LinkECU Can based Wideband standalone engine computer

At that point I think I will have the car dialed in.









Here is a pile of the parts that are still going into the car:

 

Hey we currently have an R50 with the same aluminum trailing arms but we swapped to R56 calipers in the back. The issue we ran into is the R50 ebrake cable end is a different setup and doesn’t fit through the squared off hole on the new calipers.

Did you end up doing any swaps with this or have any similar issues marrying up the parts?

 

I have a set of R56 calipers that are going on the back of my R53 shortly (for ease of changing pads), and my understanding is that the later caliper requires matching R56 emergency brake cables. (Non-Mini brand cables aren't particularly expensive, but changing them does require dropping cat-back exhaust.)
Anybody know otherwise?

 

You need new ebrake cables? This only if you put R56 rear calipers correct?

I had planned to reuse my R53 rear calipers and ebrake cables.

 

Correct. If you stay with R53 rear calipers, your existing R53 E-brake cables will work fine (and you don't even need to disconnect the cables from your calipers when swapping-in the R56 trailing arms).

The only reason to switch to R56 calipers is if you want to easily change rear pads for track days, because the newer calipers are significantly faster to swap back & forth.

 

Ok just confirming, thanks!

Will be doing this along with coilovers in the coming weeks,

 

I always wondered if this conversion is worth the headache with the weight savings.

One of the biggest issue a lot of R56 owner has is the soft aluminum threads in the trailing arm that tends to strip easily due to the triangular bolt BMW choose to use. This of course can probably be remedied with a Timesert if it happens.

I’ve contemplated this mod many times on my R53, curious to see your feedback on it.

 

Regarding those threads where the bottom of the shock attaches to the trailing arm. . .
A simpler option then Timeserts to deal with those soft threads when you install the aluminum arms is to replace the self-threading triangular bolts with regular (high-strength) bolts: BMW/Mini #33506779488 is the correct 14x105mm zinc-plated bolt, and here are the non-captive matching shock washers: #33526776759. If all else fails and you have stripped the threads, yes, the Timesert is the best solution, but the install tools are expensive. Do use either loctite or anti-seize on the bolt to prevent galling the aluminum threads.

You will also need these adapter bushings when bolting R53 shocks to R56 trailing arms: http://www.waymotorworks.com/r56-rea...ngs-or-gp.html. (They are available from multiple sources.)

Last, but not least, when installing the lower shock bolts, make sure the parts are properly aligned, and finger-tighten the bolts at least a half-dozen turns before you grab a ratchet. To get the alignment right, I found it useful to first install the upper shock-to-body bolts loosely, then (with the shock adapter in-place) use a jack to raise the trailing arm 'til it aligns perfectly. Bolt goes through washer/shock/adapter, to threads. Hand-tighten and torque to 103ft-lb. then finish tightening the top bolts (41ft-lb).

 

Never had a problem and I have done this 3 times on my R53's - But I always used new bolts from MINI for the lower shock connection.

 

I've done this conversion at least 20 sets now and I just reuse the stock bolts and not had a problem with them once. But also I've never run into any thread problems on an R56 with the aluminum arms. So use the bolts that come with the arms and you should be good.
I have seen people cross thread them by not having the bolt lined up so I would make sure you have the bolts in straight.

 

Way, how many foot pounds do you torque the lower shock and front bushing bolts to when re-installing?

 

I have personally never had issues with my own cars on the lower bolts but it always makes me nervous taking it in and out as the forums is littered with numerous accounts of people stripping it out. Which I can see happening quite easily.

I’ve been contemplating this upgrade more and more lately as I’ve been thinking about doing the R56 fJCW rear caliper and rotor setup along with the e brake cable.

 

So you need the sway bar links from the donor R56? Dang it, I took them off the trailing arms because they wanted $5 each for them at the Pull & Pay. What is different about the sway bar links?

I have $30 tied up in all of the parts. I did get the wheel speed sensors. I tried getting the shock mount out of the shock with a tie rod separator but that did work. I wasted a 1/2 beating on the shock mount because it looked different. No way would I spend $100's on these parts, but $30 + extra parts and I will do it. I have to replace all four struts anyway, so I will add it to the alignment bill.

 

On the swaybar link, the stud that bolts thru the aluminum trailing arm is longer on the R56, and I believe the overall length was different too.
(Almost every bolt going into or thru R56 aluminum arms is slightly longer than its R53 counterpart.)

 

I'm in the process of doing this upgrade and I have everything from a breaker R56s. My question is there seem to be 3 different bushings for the rear trailing arm brackets but which is the right one?

• The PFR5-1105 suits Gen 1 models up to 2003 with a trailing arm support bracket diameter of 80mm. For inserts use PFR5-110.
• The PFR5-1104 fits later Gen 1 models from 2003 onwards with a trailing arm support bracket diameter of 60mm. 
For inserts use PFR5-1102
• The PFR5-1103 Rear Trailing Arm Front Bush fits Gen 2 models with an aluminium rear trailing arm. For inserts use PFR5-1002

I've been told the PFR5-1104 fits the Gen 2 bracket but not sure.

I assume you the bracket from the Gen 1 models from 2003 are not the same as the Gen 2?

 

pfr5-1103

 

Have you converted? What a different car i am driving since converting, new shocks new tyres new brakes....roundabouts and corners no troubles

 

Great thread here.

This is something I've been contemplating too, need to get off my lazy **** and do it finally.

I've been contemplating it long enough and at this point I think the pros outweigh the cons.

I was slightly worried about the aforementioned threads stripping, and as well I also read that the MINI Challenge racecars don't do this conversion because the aluminium is brittle and has a tendency to fracture and crack if impacted whereas the steel just bends. The same material is used for motor mount brackets and you can see in the pic below how it just split in half:



But I've realized that for a road car it shouldn't be too much of a concern as if such an impact does happen well then there'd be bigger problems than that and it'd be waiting on a tow truck anyway, not likely to press on regardless like a race/rally car might do.

.

 

^ Getting into a crash versus normal driving are two different things tho. Some engine mounts are actually engineered so they break during a crash so the engine gets pushed down and away instead of going toward the driver. I wouldn't be worried too much about the GP parts as we'd see complaints about them being broken all the time.

 

Yeah, I agree.

Real world use should not present any problems.

Sort of an irrational reaction on my part because my fear also arose from sort of a traumatic experience back when I first got my car and changed out the motor mount --- when refitting I slightly over-torqued the ground bolt on the bracket and the whole ear just sheared off completely like it was made of clay and I thought holy crap! this is some mickey mouse material ! ! ! - coming from mid 80's Swedish sturdiness where stuff is solid and well made, it took some getting used to the modern world tendency for chintzy plastic and such stuff.

And what's the deal with that ugly oxidation that often occurs with MINI aluminium parts?



It may be just the nature of the composition and common for such aluminium parts?

After breaking the ground mount ear, I was suspect of what I interpreted to be poor casting perhaps with too many air pockets and envisioned it being sourced cheaply from an eastern European supplier.

 

When you buy the trailing arms if from wreckers make sure to inspect the threads, also when installing i hand tightened all the way then 100fp torqued that shock bolt. If you strip the threads helicoil fix it, you need a kit size M14x1.5 search here there is a post on that fix...so never use an impact wrench...make sure to source all bolts and that adaptor that goes between shock and trailing arm...good luck

 

Much thanks Ellie!

Appreciate it.

 

Great thread! I bought all I needed from Way, his kit is complete and reasonably priced IMO. I powder coated the hangers, sent them to him and he pressed them for me too.

 

looks amazing job well done...

 

Indeed, wow!