RSR BMW Clutches...Born in Racing

No that's not a BMW, it's a 139 cubic turbocharged 425 hp Harley that we race at Bonneville these days. 139 cubic inches is 2,277 cubic centimeters or about twice as big as your typical BMW. It requires a special multi-plate sintered iron clutch with a centrifugal lock up mechanism. More than 25 years ago we started turbocharging BMWs and ran into the same thing we encountered with Harleys, Kawasakis and Suzukis...double or triple the horsepower and zip goes the clutch.

Lock up mechanism, sintered iron plates with a high coefficient of friction, an outboard support bearing for the clutch, and an antiquated three part engine to primary to transmision assembly. This is what it takes to get the Bonneville Bullet down the long course at Bonneville.

What does this have to do with BMWs? Well, it shows we have the experience and the determination to take a bad design and get the job done. BMWs also have their bad points, even in stock form, and we aren't really happy unless BMWs have two to three times their rated horsepower. The science, materials and design are always interesting.

It takes experience to tackle problems and we have the experience, born out of necessity, to solve these problems.

Turbo History at RB Racing...1980's

In the early 1980's when we started turbocharging BMWs we quickly discovered three things. First, we found that the stock clutch held up well through about a 50% increase in power. Secondly, we weren't going to set any records with a stock clutch. Thirdly, we found that elevated power levels of 2x and 3x the rated horsepower required specialized clutch components.

Take a 50 horsepower Airhead and give it 90 horsepower and you were a hero on a flexi-frame, pogo fork wonder. At least you could spank a Kawasaki. Take a 70 horsepower K100 and give it 180 horsepower and you win dyno contests with your saddlebags along for the ride.

When we decided to bump the R engine up to 150 horsepower and go drag racing the clutch no longer worked. When we bumped the K100RS up to 312 horsepower the same thing happened. To run in the 10's with an airhead, or to run 206 mph with a K100RS, and 150 mph in the 1/4 mile, different clutches had to be developed. You couldn't change the basic design, or turn it into a multiplate or centrifugal lock-up, so new friction plates had to be made and stronger diaphragm springs had to be incorporated.

Customer turbo kits did not require clutch upgrades. The race bikes did. Now, all these years later, we need them again.

Dead Puppies

Destroyed male transmission splines and matching female splines on friction plate on "Oilhead" and K series clutches. No turbo, no 150 mph quarter miles, just "normal use". BMW tells you you have to pull the rear of your bike apart and lube these from time to time, maybe every 12,000 miles. Many destroy themselves at regular intervals. Major hassle and it costs well over $1,000.00 to do this because you get to replace all sorts of parts since you are already "there". In some cases in extreme use the clutch can shear apart.

There must be a better design. There is.

Slipping Clutches

Build a land yacht with a reverse, wheelbarrow handlebars, a marginal clutch, and you roll the dice. Slipping clutch in high gear. Thousands of dollars spent putting the same parts back in only to have them fail again. Maybe it's your riding style, maybe it's the design. All we know is we turbocharged ours and the clutch went south at 5 psi of boost. Seems a bit weak to us. Do we have an answer to this. Yes. But we need to see what the problem is before we engineer a solution.

You have twisted shafts. You have slipping clutches. You have seals that may fail and douse the clutch with oil. We'll deal with the first two.

Basic Design of BMW Clutches

Dry, single plate, diaphragm clutch as used on "airheads". These are low horsepower engines way, way, below 100 horsepower. It's capacity is defined by the pressure of the diaphragm spring, the surface area of the friction plates and the coefficient of friction of the assembly.

Your basic water buffalo clutch from a K100 and similar to all the later "Oilhead" R series. Same basic dry clutch with a single friction plate and a diaphragm spring. Spline problems on the R series and slippage issues on the land yacht LT's.

RSR BMW Clutches.. Street 360, Turbo Six Paw, Bonneville Four Paw

We offer three basic designs that address the limitations of the stock, unsprung, organic clutch. Sprung hubs lessen the shock to transmission splines. Kevlar and Cera-mettalic linings provide increased bite to prevent clutch slippage on bikes like the K1200LT and the R1100/1150/1200 GS series.

Finally, special solid hub racing designs for all out racing activities. Clutches have always been the weak link. Our racing heritage has forced us to address these issues. RSR BMW Clutches are available in both 17 and 24 spline variations as well as 165mm and 180mm diamters. Ceramic friction material (Cera-Metallic) and Kevlar friction material.

RSR Street 360

RSR Street 360: Six springs absorb the shock of engagement between the transmision and clutch splines. No more spline damage. Kevlar linings provide smooth clutch action and an increase in holding power of 15% above organic linings. Friction plates 60% thicker than stock. 300,000 PSI Dry Film Lubed splines. A superior clutch recommended for stock horsepower bikes. Outwears organic oem linings.

165mm and 180mm applications.

RSR Turbo Six Paw

RSR Turbo Six Paw: Six springs absorb the shock of engagement between the transmision and clutch splines. No more spline damage. Organic linings simply do not have the coefficient of friction that Cera-metallic linings have. If you need a clutch that won't slip this is your clutch.

Smooth engagement for street use. Cera-metallic linings. Six friction surfaces provide more bite than full circle organic designs. More solid engagement than organic materials but more suited for street use than three paw designs. No belleville spring (marcel) between the friction pucks. Friction plates 60% thicker than stock. A true high performance clutch recommended for applications where clutch slippage occurs in normal or heavy duty use. Turbo kit applications up to 240 hp. 180mm diameter.

Not available for 165mm applications.

RSR Turbo Four Paw

RSR Turbo Four Paw: Six springs absorb the shock of engagement between the transmision and clutch splines. No more spline damage. Organic linings simply do not have the coefficient of friction that cera-metallic linings have. If you need a clutch that won't slip this is your clutch.

Smooth engagement for street use. Cera-metallic linings. Four friction surfaces provide more bite than full circle organic designs. More solid engagement than organic materials but more suited for street use than three paw designs. No belleville spring (marcel) between the friction pucks. Friction plates 60% thicker than stock. A true high performance clutch recommended for applications where clutch slippage occurs in normal or heavy duty use. Turbo kit applications up to 240 hp. 165mm diameter.

If you want to spend $670.00 for a clutch without a sprung center you can buy one here.

RSR Bonneville Three Paw

RSR Bonneville Three Paw: Three friction plates provide more bite than the Turbo Six Paw with more abrupt engagement. Cera-metallic linings. Friction plates 60% thicker than stock. 300,000 PSI Dry Film Lubed splines. Used for race and turbo applications greater than 240 hp where more friction is required. More pressure per square inch than the six paw design. Solid, unsprung design.

For both 165mm and 180mm designs.

RSR"Dual Coat" 300,000 PSI Dry Film Spline Lube

As standard practice we apply dry film lubricant to all female RSR Clutch friction plate splines. In addition, each RSR Clutch comes with a mandatory dry film lubricant application kit to coat your male transmission splines. More than enough if you want to pull your bike apart half a dozen times in an obsessive, compulsive manner or, alternatively, if you choose to treat your special someone to a lube job.

Immune to heat and with a low coefficient of friction, the dry film lubricant, unlike traditional "spline grease", bonds to the metal and provides protection that grease alone cannot provide. The dry film lubricant is suspended in a liquid solution and will air dry. Simply clean and prepare the shaft per instructions provided and apply the dry film lubricant directly to the male transmission splines.

RSR High Temperature Grease Kit

We also provide a high temperature grease embedded with dry film media to coat the male and female splines. Same vial size as our dry film lubricant and plenty enough for multiple applications with your favorite toothbrush. The combination of the dry film bonding the clean parent metal of the male and female splines, plus the "reservoir" of the high temperature low friction grease, provides long term protection to the link between your engine and transmission.

We recommend a light coat on both your male and female splines. Remember, this is a dry clutch so you don't want blobs of grease flinging about. We simply use an old toothbrush to apply the RSR High Temperature Grease to the splines. The RSR Grease is incredibly sticky and you need a stiff brush to fully coat each groove.

We have provided a PDF Instruction on how to apply the two part system on your clutch and drive splines.

Choices

Two glass vials come with each RSR Clutch...one for the dry film lube and one for the high temperature grease. You may or may not choose to use these as old habits die hard. In fact, you can apply the 300,000 PSI dry film lubricant to your transmission splines and continue to use your favorite spline grease from BMW, Honda, or even Dupont Kratox. If you want to forgo the dry film application all together and apply your favorite "spline grease" that's your choice.

BMW's GL 261 grease is still being sold for your two wheeled masterpiece. In fact, BMW stopped using it in 1998 ago on their automotive transmission splines because it was "not suitable for prolonged exposure to high bell housing temperatures". We've got to move these refrigerators...We've got to move these colour TV's...Money for Nothing.

Clutch Alignment Tool

When you bolt down the clutch cover plate with the six special high strength bolts we provide, the clutch friction plate and the diaphragm spring must be perfectly aligned with the clutch housing and the centerline of the crankshaft. We machine this simple tool to keep things aligned so the transmission splines will slip into place. It is highly recommended that you buy the tool as it will save you endless frustration.

RSR Clutch Accessories

Each RSR Clutch Kit comes with a "Dual Coat) Spline Lube (Kit). Alignment tool 05-0201 (optional) is suggested as, when you tighten down the clutch assembly, the clutch friction plate and the pressure plate has to be in perfect alignment.

"K" Bike RSR Clutch Kits

Each RSR Clutch Kit comes with a "Dual Coat" Spline Lube (Kit). Kits also include special clutch cover bolts and hardware to mount the new clutch assembly. Alignment tool 05-0201 (optional) is suggested as, when you tighten down the clutch assembly, the clutch friction plate and the pressure plate has to be in perfect alignment.

"R" Bike (Oilhead, Hexhead) RSR Clutch Kits *

Each RSR Clutch Kit comes with a "Dual Coat" Spline Lube (Kit). Kits also include special clutch cover bolts and hardware to mount the new clutch assembly. Alignment tool 05-0201 (optional) is suggested as, when you tighten down the clutch assembly, the clutch friction plate and the pressure plate has to be in perfect alignment.

Diaphragm Tricks

The earlier 180mm R1100 clutches have 1.75mm thick springs whereas the later model R1150GS models are 2.00mm thick. If you want a stronger clutch for the earlier models this is a good way to go. Think pressure times area. Lever pressure is about the same. Part Number 21 21 2 345 597. Study BMW part numbers long enough and you'll find enough variations to drive you crazy.

This is what we use on a R1100RT Turbo along with a 05-0034 Six Paw Turbo Clutch.

In general, you should stay with your stock diaphragm spring as this is what you feel at the lever. The way to a better clutch is through better friction materials and more aggressive designs proven in competition as well as sprung designs that insure smooth engagement and which lessen shock loads to the splines. Some people have used two diaphragm springs. We do not recommend this.

RSR BMW clutches. Born of necessity. No tricks, just logic.