LWB vs SWB

I recently purchased a 1971 R75/5 SWB with a Globe sidecar (GS200). This will be my first sidecar rig and I expect to make upgrades. My first change will be to change frames. I've decided to use a /7 frame to beef it up, but my question is: Will it make much difference if I continue as a SWB or should I look for components to make it a LWB?

I cant answer your question, but along with the knowledgeable folks here, there is a huge collection of knowledge on the ADVRider forum under Hacks.

/5 frame ok

The later frame does have a stronger top tube, an extra transverse brace between the front down tubes, a longer swing arm and longer rear loop to suit. But as for sidecar use, I doubt those changes merit the cost and labour of switching to a /7 from a /5. You could help us with a photo or two, especially of the mounting points. Make sure the clamps distribute the forces as widely as possible, and that the frame tubes themselves (which are very thin-wall) are not crimped. The mounts should NOT be on the rear subframe, it is a very weak piece.

There are lots of /5's around with sidecars, and they perform quite well.

In any "airhead" frame in sidecar use, watch carefully for evidence of fatigue on the gussets around the steering head -- that's the first, and thankfully rare, evidence of frame failure.

Enjoy!

My first sidecar was exactly what you have a SWB /5 and a globe. Replace the frame with a /7 frame. I broke mine a couple of times until I gave up and built an EML. If you need help with a subframe to mount the sidecar to bike PM me and I will give you my phone number so I can better describe a safe way to go.

The /5 frame is somewhat weaker all around, although the Globe is a very light car. Trouble is, there are some significant side loads when cornering, whether the rig is lightweight or not.

FYI, I have a reinforced /7 frame hanging on the wall, that I intended to use in my R100t/Ural rig. However, the current frame is working fine, so I never swapped. It's got a clear title from a '78 R100. reinforcing gussets in front of the swingarm pivot bosses.

I also have a LWB swing arm, and a spare 11/37 final drive I could part with. I need to slim down my "inventory."

Yes, even a /7 frame needs some clever reinforcements. I could probably dig up some photos in due course.

pmdave

/5/Dnepr

I have a /5 with a Dnepr (similar to Ural) rig.


Here is a pic of the attachment parts:



The top left piece reinforces the frame at the junction with the rear sub frame over the battery. Top right piece reinforces the front down tubes just below the head stock, and accepts the front sidecar diagonal brace. The middle piece is the main subframe that bolts to the engine mount bolts, and the rear footpeg mount. This accepts the two lower sidecar mounts.
I have a sidecar triple tree system from Perry Bushong's shop in Fort Worth TX. This moves the forks out about 1 1/2" and thereby reduces trail making steering much easier much the same way a leading link front forks does. Just not as stout as a leading link set up.



I have a final drive from an R50/5. This works real well and gives me some acceleration in 4th gear. With the stock R75 final drive I hardly ever could use 4th gear. The rig works real well. I won't argue about a later frame being stronger, but so far I haven't had a problem. I don't have the rig out a lot, and usually not loaded.

HankPfister said:

I have a /5 with a Dnepr (similar to Ural) rig.

Here is a pic of the attachment parts:

I have a final drive from an R50/5. This works real well and gives me some acceleration in 4th gear. With the stock R75 final drive I hardly ever could use 4th gear. The rig works real well. I won't argue about a later frame being stronger, but so far I haven't had a problem. I don't have the rig out a lot, and usually not loaded.

Click to expand...

Beauty Rig! Post more pictures of it...

To the OP:
I had a SWB and LWB /5 at the same time... Surprisingly that 1.5" made a big difference between the two's handling.
I was going to hack the LWB but never got too it.
With advent of /5's the weak link seems to be the radical frame change and the use of the 'sub-frame'.
It was this change that pretty much ended the use of sidecars on BMW as the attachment nodes were now gone as seen on /2's.
My concern would be the 'subframe' and the swingarm.
The 'mainframe' is pretty robust and as I remember it the same on both. Beef up the subframe and pivot points.
As for SWB... It may help being an 1-1/2" shorter w/ the wheels relation to the position of the hacks wheel.
The wheel on the hack leads the bikes rear wheel by how much?

Thinking out loud here for a minute....

The /7 main frame is much stronger than the /5 and even early /6 frames which makes it a better choice. If I was building a road-going hack, I would use the more robust of the two frames. The /7 main frame has correctly designed steering head gussets and heavier wall larger diameter tube on the cross braces plus there is the added brace under the steering head to consider. In fact, the /7 steering head angle is steeper than the /5 which will make the steering behave differently - quicker and less stable, more prone to head shake. I discovered the difference when I put a /7 swing arm in a /5 frame to build a long wheel base bike. The resulting wheel base using the /5 frame was an inch longer than the wheel base of the /7 frame with the same dual disc front end and long swing arm. If you go this rout, I suspect youÔÇÖll need a serious steering damper or a leading link fork to compensate. The photo I've attached for you to look at is of a very well sorted out road going machine. Thats a Watsonian sidecar. The bike frame is 1978 /7 (R100S).

This is your very first experience with a hack is it? What are you going to use the sidecar for? Are you planning on trips to the store for groceries or going out on the open road? If your intention is to use it for running around town you may be better off to enjoy it as is. If the time comes when you decide you need more performance then consider the upgrade or perhaps a completed hack with all the features you want already built-in. You are talking about a lot of work after all for specific performance gains which you may not even need or use.

pics

1971 R75/5 w/Globe sidecar

mounting points

this is the current setup for mounting

sidecar teardown

note frame has a ballast plate attached to frame

What a great project rig ~! Really...

That chunk of steel "ballast" looks like it probably weighs as much as the motorcycle. I use water because its available and adjustable ballast. Those sidecar mounts at the motorcycle look more than just weak, they look improvised as in Invention of necessity is a mother type of improvised. Do not even consider reusing them. The mounts at the chair itself look basically good to go but the front mount is rusted beyond trusted. I think that one thing you could do is to start looking around for options on mounts for the bike. That could be the determining factor between long and short frame. Lowel Neff in AZ, Perrys sidecars in Ft. Worth TX to name a couple of sources I have used for components. Also, look at the sidecar manufactures sites for mounting kits. http://www.sidecar.com/mbbs22/category-view.asp is the website for the USCA folks (United Side Car Association) and there is a classified section for all things SC related. Nice looking chair by the way well worth the effort to re-rig. What kind of hieroglyphs are those on the pedestrian slicer?

In addition to the /7 main frame, to make a long wheel base bike youÔÇÖll need shocks, mufflers, a /6 seat to go with the /5 large tank (/7 and /5 seats will not fit), swing arm, drive shaft, /6 or /7 sub frame, brake rod, and battery box w/mounts to name a few parts off the top of my head.

Here is a close up of the bike I showed you earlier...