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Pics Of These Dodgy Home Made Disc Adapters?


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I cant remember who it was, but the one on that GU is second hand, and the guy who made it also made one for a python. I think.

If your thinking about making one, then this might be usefull:


Its the ISO standard for front disc mountings. If you use that, then you will have a +20mm adapter.

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Wally made them didn't he?

Inur made one allowing a king bmx hub to be used in a monty, but it was a disc frame allready.

It would work on stock, but i'd want one a bit more beefy considering the increased distance between the dropout's and brake mounts.....

Edit: because the forces are spread out over a larger area, there might be more of a tendancy to breaking either the mount or the frame, more likely the frame if it's aluminium and the mount is steel. It would depend very much on the frame design, what were you thinking of doing it to dave?

Edited by jake1516
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ye, the adaptor post was Inurs, unfortunatley i had to shift a lot of material myself, so i think it is alot weaker than it could of been if i had known exactly where it needed to be before i set to fixing it. so if i have to/decide to make a stronger one i will post pics with it off and on the bike. Do it mate, the rear disc is absolutley beastly

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Boothy is by far the best and the other good thing his dad actually knows what he is doing being an Engineer, he knows what material to use and such forth, bring on the 26" adaptor for the Karbon i say :) il nip down and see your dad at some point Mr Booth and see what he can cunjour up, might have to remove the disc side spacer off one of my hubs to make it fit correctly.

those mounts that go to the magura mount are putting extra stress and pressure on the frame, as with boothys the stress and pressure is more on the hub. a steel axle is probably stronger than an ally frame? imo that is what has made me want to work with Boothy dad to make one fit a 26" on the inside of the dropout relying on the hub.

the other mounts obviously work so fair play (Y):) the material just looks a bit thin :S


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I just don't see how it could work, maybe it's the angle the photo is from or something bu it doesn't seem like there is anything to stop it just spinning around with the disc when you pull the brake?? im probobly missing some real obvious point here.....

Yes those are putting more stress on the frame but the frame can disapate the forces more than the hub can, and by using two perhaps 3mm rubber washer's at the 4-bolt mount's you may be able to reduce that even more, at he risk of creating a spongier brake.

but yeh I havn't wrote off boothy's design I just think I need to see it on the bike to understand......

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I want to make mine so that the bolt goes through the frame>slot in the adaptor>then into the wheel but i also want to make it bolt into where the snail cam goes so it doesn't spin round

will this work because it'll look a whole load neater than making it from the brake mounts.

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I can't see any reason why frames shouldn't be equipped with disc mounts. There are quite a few good designs like the Modulo, Simtra and BT which are super beefy. I wouldn't trust Kot though or the ridiculous mounts the Limey had which would probably snap from just looking at them. Here's a quick explanation of the basic forces that act on a disc mount, I repeat REALLY BASIC.

In a design like this, there are two stress areas. One is the magura mount and the other is the dropout and hub axle.

The adaptor's main "pivot" is the hub axle and the dropout. It rests on the frame and the hub at the same time which are both very strong parts of the bike as long as they're not of shit quality. Any HD King or Profile hub will do the job.

The other stress area is the magura mount. Due to there being a really small leverage (marked as the blue and dark yellow line) the force acting on the magura mounts is very small. The angle of the force is also very flat, so it's not pulling the screws out but actually using them as something to rest on. With rim brakes, the threads are being pulled out each time you break and yet they're fine.

Here's another mount which has proven to work well, the Monty PR/Ti type. It's placed directly on the dropout which means it's strong within that area but puts a lot of stress on the top and bottom tube of the chainstay. The force is pulling the mount upwards at a large angle but yet it's fine. Luckily, the angle between the tubes is quite large which makes the design stronger. It's additionally supported by a bar which transfers the force onto the bottom tube as well. (Thanks Jake for the pic)

Simtra, flat force and a beefy design, perfect to cope with the extra leverage a 26" gives.

I don't quite trust the KOT design but I think it's good. The dropout and disc tab is one CNC element which means there are no weak points between the dropout which is the pivot point of the disc tabs, and the mounts themselves. Additionally, theres a tube between the top and bottom one which acts as extra support. The welds themselves would probably be the weakest element in this design but with a large weld area they are no doubt stronger than the tubing itself. It's actually the tubing I would worry about, Kot frames are a bit too light.

Alright then. A comparison of the two designs. The standard brake mount is mounted on the top tube which essentially is a long lever, pivoting on the hub and supported by the bb and seat tube. Then you've got the screw-on, which is mounted near the hub axle and on the DM mounts. At the bottom of this pic, there are 2 black lines. The shorter the line, the more stress is put on the frame. The short line represents the traditional mounts, the long line represents the screw-on Wally and I made.

To sum up, the closer the mount to the bb, the stronger the design will be - and that's why we hardly ever have problems with frames cracking because of Magura 4-bolt mounts. So why don't companies make adaptors like ours? Because there's just no point, what is currently in production is good enough.

And last of all, the good thing about these screw-on adaptors we made is that they're MUCH more likely to bend/break than the frame. And as making one from scratch takes only about 3 hours using crude tools, you can't loose. The next step is to get the design right and have one cut out CNC from aluminum. Not only will it be lighter, the saved weight can go into making the adaptor stronger and stiffer. Aluminum is more brittle than steel and up to a point will be stiffer as well if treated appropriately.

This is probably going to be a FAQ soon as more and more people are getting dual disc on non-disc frames. I'll be making my adamant dual disc this year but that will involve drilling the frame etc. The ideal setup for an adaptor like this is a 26" mod with narrow hub spacing. Personally, I'm not quite sure if an adaptor like this will work on a stock without extra support from the tubing, meaning it would have to be screwed down to the frame in places other than just the Magura mount.

Edited by Inur
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