Rear wheel spoke conversion - brake caliper bracket.

sfcpiet said:
Exactly. Difficult to get the stock disc to fit with those wheels AND retaining the stock anchor on the swingarm.

Quentin, getting the caliper lined up with the stock disc while it is above the swingarm isn't possible with the stock type bracket, no space, unless you cut a chunk from the swingarm. Wasn't an easy task machining the brackets back then with our rather rudimentary facilities, I would have gladly passed it on... but Herr Witt insisted on the finished product looking "factory", which it indeed did. The conversion eventually even attained TÜV approval!

The rearward position of the lower shock mounts of the SFC/Spaceframe frees up a lot of space required to locate the caliper upstairs. Road swingarms are a lot more cramped. A lot easier to start from scratch with a more suitable/easier to work with caliper and anchor point.

piet
Click to expand...
So question begs, does anybody have an original DeWitt conversion to see how it was done?
 
Russ,

They've been sold out for decades. Very much doubt most running wire wheels in later models actually know what they've got.

An opposite-side caliper hung below the swingarm using the original bracket anchor, not that difficult. Download Fusion 360, take measurements and learn CAD... trott down to your local CNC machine shop with a lump of alloy and the 3mf. or step. file.

piet
 
Russ, if you look at an sfc1000 rear calipers setup it will give you an idea of how it’s possible to achieve a result. I run a Zane calipers bracket and calliper on the back of my Jota and it was a pretty easy conversion. The carrier for the disc was custom made as I wanted to run the Zane rear disc. You could run a 500 rear disc as they are 260mm . Put your thinking cap on and away you go😂👍
Tom
 

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Agree with Tom ... if you're going with a major upgrade like a spoked rear disc, you may as well get some real benefit - lighter, better mounting system, floating caliper ... and not rocket science.

I made my own caliper carrier and disc adapter for the cheap as-new Yamaha R15 (150cc) rear disc on my bike. On my SFQ I welded a threaded lug to the frame under the swingarm for the front torque arm connection, but on a build I'm doing for someone at the moment I was able to fit an M12 bolt to the inside of the (unused) footpeg mounting bracket and drill and thread the bolt for am M8 thread for attachment of the front rose joint (avoiding modification to the frame).

Rear caliper carrier.jpg
 
It's so much easier to modify someone else's part than start from scratch. I like the continuity of using Zane bits. There, sadly, must be a bunch about in the old country. Years back, I used a later-model Yamaha Alloy single shock swingarm on an XT 500. I cut the single shock bits off and added twin shock mounts. Made me a bit nervous the first few times I jumped it in anger, but it worked out great, no cracking.
 
So finally ended up designing a purpose built caliper bracket and different spacers to keep an original look. If money was no object I'd redo with some changes, seems to fit with everything lining up though.
 

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Nice job Russ😊👍 Do keep an eye on the rear disc if it’s a full floater, was warned by Wolfgang years ago that’s it’s not such a good idea as there had been a few disc failures.
Tom
 
ozijotati said:
Nice job Russ😊👍 Do keep an eye on the rear disc if it’s a full floater, was warned by Wolfgang years ago that’s it’s not such a good idea as there had been a few disc failures.
Tom
Click to expand...
To be honest Tom, I don't use the rear brake much at all, just need it to get the bike through the inspection 😆. I got the discs through Gert who's run them on his 1200 SULZBACHER for many years now. Still point noted and eyes open.
 
my favourite Mike Hailwood quote " if you are using the front brake hard enough, there will be fresh air under the rear tyre anyway"
scrutineer did not agree, was The 350TZ he raced in the open class at Silverstone prior to the 1978 TT, and the crossover linekages were ok for the gears, but crap for the brake.
CLEM,
I think he was fourth, but beaten only by 500/750's
 
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