Getting rid of the rear brake hub
Posted: Thu Apr 14, 2016 8:02 pm
The Modification to fit a swinging arm brake calliper only requires two pieces of metal. It is also necessary to turn up a spacer. The length of the spacer is equal to the length of the standard spacer plus the length of the spacer that is fitted into the hub that you are replacing. The ends of the spacer should be the same diameter as the end of the free spacer and the end of the hub spacer. Being of an economic persuasion (i.e. a cheap skate) I used what I had in my scrap box.
The right angle bracket needs to be just as long as the flat topped part at the back of the swinging arm, the section that is parallel to the axle adjustment. In the pics you will see a couple of vertical ‘slots’ in this bracket. These are not necessary, they just happened to be in my piece metal when I found it! You will have to drill and tap the rear of the swinging arm to fix the rear of the bracket. The front of the bracket can have nut on the underside of the bolt where it goes through the swinging arm.
The vertical plate to which the calliper is fixed was also some scrap. You can see in the pics that the calliper is bolted to this plate using two bolts of suitable size for the calliper chosen. This was fine for Brands Hatch as it was set with the correct rear sprocket for this track. What I need to do is make the calliper fixing holes into slots so that I can readjust the calliper position when I change sprockets. (I am not actually sure that this plate is long enough to allow full adjustment of the sprocket range. I might have to change it for a longer piece).
Again, I had available the calliper that I used but any 125cc front calliper will provide excellent braking (the scrutineers were happy, but my daughter rarely uses the back brake anyway). A couple of washers and a nut bought the centre of the callipers in line with the brake disc.
The only remaining problem was that the disc was too ‘fat’ to go in the slot. I took the calliper into its two halves checked where fluid transfer hole between the two halves was and filed the slot wider – there was plenty of ‘meat’ spare to do this. Took great care to clear the swarf out and re-assembled it. Put it all together and the last action was to remove the torsion arm.
Excellent rear brake and a considerable saving in weight. If you need more photos or information please pm me.
The right angle bracket needs to be just as long as the flat topped part at the back of the swinging arm, the section that is parallel to the axle adjustment. In the pics you will see a couple of vertical ‘slots’ in this bracket. These are not necessary, they just happened to be in my piece metal when I found it! You will have to drill and tap the rear of the swinging arm to fix the rear of the bracket. The front of the bracket can have nut on the underside of the bolt where it goes through the swinging arm.
The vertical plate to which the calliper is fixed was also some scrap. You can see in the pics that the calliper is bolted to this plate using two bolts of suitable size for the calliper chosen. This was fine for Brands Hatch as it was set with the correct rear sprocket for this track. What I need to do is make the calliper fixing holes into slots so that I can readjust the calliper position when I change sprockets. (I am not actually sure that this plate is long enough to allow full adjustment of the sprocket range. I might have to change it for a longer piece).
Again, I had available the calliper that I used but any 125cc front calliper will provide excellent braking (the scrutineers were happy, but my daughter rarely uses the back brake anyway). A couple of washers and a nut bought the centre of the callipers in line with the brake disc.
The only remaining problem was that the disc was too ‘fat’ to go in the slot. I took the calliper into its two halves checked where fluid transfer hole between the two halves was and filed the slot wider – there was plenty of ‘meat’ spare to do this. Took great care to clear the swarf out and re-assembled it. Put it all together and the last action was to remove the torsion arm.
Excellent rear brake and a considerable saving in weight. If you need more photos or information please pm me.