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Old 01-08-2013, 04:27 PM   #1
dan-o OP
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/5 frame versus /6 frame

Does anyone know the changes between a /5 main frame and a /6 main frame? Other than the battery mount bottom piece and ears, and the tab for the steering friction plate. Can I swap everything from a /5 to a /6 frame without major modifications? It appears the horizontal crossmembers at the rear are a larger diameter.
thanks,
dan
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Old 01-08-2013, 04:57 PM   #2
Big Bamboo
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I believe the fork locks have different diameter cylinders.
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Old 01-08-2013, 09:33 PM   #3
Wirespokes
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I believe everything will swap right over. I think (sort of a dim recall on this) the only real difference between the /5 and /6 was rake angle, but that's nothing to worry about.
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Old 01-08-2013, 09:42 PM   #4
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I believe that at some point they fitted a second tube up the middle of the main spine presumably in an attempt to strengthen it. Mine has this double wall tube.
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Old 01-08-2013, 09:49 PM   #5
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I think they did that in 76. But that doesn't complicate the swap from /5 to /6.
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Old 01-09-2013, 04:04 AM   #6
dan-o OP
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thanks so much for the information. I appreciate it!
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Old 01-09-2013, 01:43 PM   #7
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Quote:
Originally Posted by Wirespokes View Post
I believe everything will swap right over. I think (sort of a dim recall on this) the only real difference between the /5 and /6 was rake angle, but that's nothing to worry about.
I have read that in glossy magazines but BMW's frame jig test all airhead frames. They all have the same rake. /6? ?6's were constantly changing. It probably depends on what year /6. You at some point got the doubled tubed backbone, the extra cross brace under the steering head and a lot more and bigger gussets. By '81 the frames were a lot stiffer and heavier.
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Old 01-10-2013, 03:02 PM   #8
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this frame is dated 6/74. Sounds like a good strong frame to hold all the torque from my R50/5 power plant
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Old 01-10-2013, 04:14 PM   #9
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As you surely know the rear sub frames changed from the short wheel base to the long wheel base. The late 1973 long wheel base sub frames are a double tube cross brace arrangement and stronger than the 1974 stamped steel cross brace arrangement. When I cobbled together my 1974 framed sidecar rig I sought out a 1973 1/2 rear subframe for that additional strength, plus my old QSL solo seat needed the arrangement for the mounting system.






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bmwhacker screwed with this post 01-10-2013 at 04:22 PM
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Old 01-10-2013, 04:30 PM   #10
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yes, I am keeping the short wheel base subframe and swingarm. Did you weld on the tab for the old front end friction type steering dampner?
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Old 01-11-2013, 12:19 PM   #11
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Originally Posted by dan-o View Post
yes, I am keeping the short wheel base subframe and swingarm. Did you weld on the tab for the old front end friction type steering dampner?
I ended up with a modified dual disc BMW 60's Earls front end... lengthened a /5 damper rod to fit the Earls, then had to get "creative" for the lower damper pieces to mount.
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Old 01-11-2013, 10:49 PM   #12
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The battery box is the only major difference. Everything else will bolt on
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