I should clarify my previous statements: I originally responded to the query regarding Perry's mounts for an airhead BMW. My first hand experience was not encouraging. On the other hand, Perry has been mounting sidecars longer than I have and he has many satisfied customers. We mounted this hack maybe 15 years ago and I don't know if it is the same as what he is using now. My remarks about BMW frames were based upon both personal experience and the widely held reputation BMWs of that era have for being flexible and for frame failure. BMW manuals for these bikes specifically state the frames are lighter than the earlier /2 and are not adequate for sidecar use. You do not need to look far to find anecdotal evidence to support that position. I believe this weakness can be addressed with a proper subframe. That is my opinion, not necessarily fact. Pam I was speaking about my experience with Mike's bike, not your experience with your bike. There are lots of variables and it is not surprising experiences and opinions will differ. I don't know how you mounted your sidecar or where the attachment points are. I am very happy to hear that it is working well for you. In my opinion the R90 is one of the few really pretty bikes BMW has built. Some would consider it collectible. If it were mine I would not risk damaging the frame with clamps or by welding on it. It is possible to bolt mounts to an airhead without a subframe, but even this I would be reluctant to do. A subframe allows you to better position the bottom mounts and re enforce the bike frame fore and aft and from side to side. Depending on the use, among other things, a year may not be enough time for damage to become evident. My KLRs broke after several seasons hard use which include classes on bumpy ground, dualsport rallies, a few tipovers and daily commuting. I discovered the damage after jumps with a passenger aboard and some high speed washboard. . I really think though, that the damage was cumulative. Even if you only ride on the street a substandard mount will eventually result in damage or failure. In my opinion. But please understand me! I am not calling your rig substandard, nor am I saying Perry's mounts are no good. I'd have to have them in front of me. Besides, I am not an engineer. I am just a guy who has messed around with a few of these things. What I have posted are just opinions and worth no more than what you paid for them
This is what I've been thinking, too, have even seen a few listing for north of $12,000. I'm thinking of selling the R90S and perhaps buying a GS of some sort, most likely airhead or pre-2000 oiler for rigging. Sure do like the looks of the rig Jay rode to your party, though. Pam
In the late sixties I inspected brand new BMW models in the showroom of the Qld distributor; Morgan and Wackers. I took home some of the glossy brochures on them- black (or white) R50, R60, & R69. BMW was experimenting with bar-end flashing indicators in that period. These models have quite substantial frames, and even sported ball-shaped sidecar mounts on the Right-hand side (Unfortunately, for Oz). Its even possible (don't quite remember) that the brochure showed a sidecar, or two. ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ Fast-forward to 1969. I looked over the new /5 models; R50/5, R60/5, and R75/5. Took home a thick BMW booklet that "Premiered" the slash 5s. Quite prominent inside, BMW announced that the new frame design meant that owners would have to forgo their use with a sidecar. In 1971 I had my first BMW; a R50/5 with electric start. This was an extra cost option on the 500cc. During the years 1974-1985 I was a member of the QLD BMW riders club. Legendary were the occurrences of broken sub-frames, and these mishaps were mainly on solos. If someone wanted to build-up an outfit, they either used a complete pre-'69 model, or at least shoe-horned the /5, /6 motor into one. (NB. My current, and first, outfit is my 4th BMW; from R25 to R100RS.) ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖ From 1973 I owned a Moto Guzzi 850T with the 'Telaio Rosso'-shape frame. This is how to build a strong frame . . . . . not what BMW did with their twin-loop plus bolt on. Moto Guzzi V7 Sport, with the 'Telaio Rosso' legendary robust build. The 850T shared this frame style. Two-piece motorcycle frame which can barely cope as a solo. If I had the money, my R100RS engine would be mounted in a /2-type frame, or even a CJ. I once rode it around the major holes on a road closed to ordinary traffic. The Ural tub & frame came through unscathed, but . . . . . welds broke at the front of the downtubes, & the upper triple fork plate came close to breaking away on the centre hole. After that; ● Some welding. ● A set of Perry's reduced trail T-clamps (which are beefier than stock). ● Addition of a cross-brace bridging upper rear-frame connection bolts, which makes battery access more difficult. I'm in the process of changing over to an external (to bike) automobile battery.
Sure hope the electric start on your 50/5 worked a lot better than on my '71 60/5, which never saw a cold morning it would start on; but it was so much better than the Honda 350 that I didn't mind kick starting much. That already well used 60/5 made it all around North America in '76-77, including half way down Mexico, and back to the east coast, with a lot of very bad roads between (the Mexicans used to prepare back roads by dropping huge gravel in the road bed and letting the drivers crunch it). I fell in love with Beemers on that year+ long trip. However, I appreciate what you're saying. I've never had frame problems, even with the sidecar on the '76 R90S, but am not so stupid to assume it means anything, necessarily, except possibly that I was lucky and/or much easier on my bikes than others. Who knows. Pam
Hi Jim, Perry built a rig for me in 2008 using my 1977 R100/7 and a Ural sidecar he obtained for me. It was a down-to-the-nuts-n-bolts rebuild and the resulting rig was a work of art in both form and function. Go with his triple trees for sure they work as advertised. Ace Cafe Rat
Thanks Rat. My original post was in 2011. I ultimately went another route, but if I build another airhead rig I will probably go with Perry's trees. Post up some pics of your rig! Can I take it from your sig that you're also a Royal Enfield iron barrel rider? Met too. Loads of fun!
Watch the frame of a big truck going over a really bumpy road... It flexes! In fact, it's intended to flex, and if didn't it'd rapidly crack and be torn apart. Now let's apply this to airheads... If you brace and reinforce the frame of an airhead, it gets much more "buzzy" as it's transmitting engine vibration rather than absorbing it. That begs the question: Was the airhead frame intentionally designed to flex? Probably, especially given that it was designed by a Brit who had previously worked for Triumph/BSA. British and Continental steel tube manufacturers have always made frame tubing in various guages, etc. so bicycle frame builders could mix and match them to get the best combination or rigidity and suppleness, and those same manufacturers supplied the motorcycle industry too. Thus I suspect the airhead frame and a lot of other bike's were purposely designed to flex somewhat. One notes this by the change in resonant RPMs in an airhead fitted with a sidecar subframe, even without a sidecar mounted. Thus the subframes we're fitting in fact may or not be strengthening the outfit, and multiply the number of subframes times the possible locations of mounts and sidecars to be mounted and we'd need supercomputers to figure it all out. Perhaps that why some outfits get by fine without subframes, and some break frame bits even with subframes?
