Changing out the swing-arm?

Barbara · Posted: October 11, 2009, 11:53 am Post subject: Changing out the swing-arm?

Hi Guys,

I'm fighting rear-wheel spokes on my '77D, since I lug a sidecar around with her. Finding spokes is difficult enough, but constantly worrying about tightening spokes or taking the wheel off to replace broken ones is a pain, especially when I have a '79 with cast wheels and a rear disc. I have heard that because of the disc, you have to change out the swing arm...right? I have the aftermarket bushings on my current swing-arm...does anyone know if they will fit the cast-wheel swing-arm?

I went from the aluminum rim to a stainless one because of flexing, and the spokes lasted lots longer, but after 6000 or so miles, they are getting very loose now and requiring lots of attention. Since I have the '79 engine in the '77 while I am rebuilding her original engine, I guess the swing-arm and wheel wouldn't hurt. Not my favorite look, but functional with the chair.

Anyone done this conversion? Tips? Horror stories? Pleas for me not to waste my remaining youth in a fruitless quest? Something?

Thanks, Guys!

Waldo · Posted: October 11, 2009, 12:10 pm Post subject: Re: Changing out the swing-arm?

Barb,
ikes XS lists the bushings as fitting 70-84 models, how about the inner sleeve, I changed it and the axle at the same time.
Waldo, Bellingham

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

I think the bronze bushings are the same for spoke or mag. For that matter the swing arms are probably the same also I thihnk you have to have an arm up top to hold the caliper bracket on the disc brake verion and mounting arm on bottom for drums.

Barbara · Posted: October 11, 2009, 5:55 pm Post subject: Re: Changing out the swing-arm?

Hi Guys,

Thanks! Maybe I can just weld the bracket for the disc on the existing arm? Hey, Waldo, is there a BMW dealer up in B'ham? (I'm in Mt. Vernon.)

I think tomorrow after work I will "offer up" (as the Brits say) the cast wheel and axle on the original swing arm and see if it all fits. If it does, I'll get my son to weld the necessary tabs for the brake. If not, I'll use the swing-arm from the '79.

Thanks for the input! Very Happy

Waldo · Posted: October 11, 2009, 7:32 pm Post subject: Re: Changing out the swing-arm?

Barb,
No BMW dealer I know of. Do you have the bracket that holds the rear caliper, I have one plus the swing arm with anchor arm as spares.
Waldo

weekendrider · Posted: October 11, 2009, 10:09 pm Post subject: Re: Changing out the swing-arm?

Do the complete swap. Swingarm included IMO. Have you considered the swingarm and rear wheel from a TX750?

Barbara · Posted: October 12, 2009, 10:18 am Post subject: Re: Changing out the swing-arm?

Hi Guys,

Well, what I'm trying to do is to keep it in the shed, so to speak. I have the '79 that donated an engine (temporarily) to the '77, and the swing-arm/brake/etc. is complete and if I can just swap them out, then (ahem) the price is really right. Like I mentioned elsewhere, I think the Universe is just pushing me in the direction I want to go....

But spokes look so neat.... Sad

yamaman · Posted: October 12, 2009, 10:38 am Post subject: Re: Changing out the swing-arm?

Easy swap Barb, good opportunity to check it all out in there & give it a nice dollup of fresh grease.

Also do you have a std pivot bolt? I'm sure your aware that they are prone to breaking, and especialy as you've got that chair bolted on the side, you might be giving it a bit of curry. So while you've got it apart, you can have a good look at that. Mikes has good pics of what the difference between original & new type bolts.

And if you chop the other swing arm, then your down to only one, and you'll have to add a brake stay to mount the drum wheel in the ex disc arm. Cheers

xsleo · Posted: October 16, 2009, 12:22 am Post subject: Re: Changing out the swing-arm?

When you change over to the disc brake you will need to change the brake pivot shaft as well. You will also need to mod the stop too. I used a bent piece of steel, bolted it to the existing stop and threaded a hole to line up with the disc brake pivot shaft. Then relocate your rear brake switch. Lots of little things. It was all worth it on my 75, I love my brakes. Looks kinda funny with a mag on the rear and a spoke wheel on front. I think that's ok because I can't see the wheels when I'm riding.
It might be just as easy to move the chair over to the 79 frame. Then do what you planned for the 79 to the 77.

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