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Author Topic: Disc brake conversion for Bullet 500  (Read 107 times)

creaky

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Disc brake conversion for Bullet 500
« on: June 14, 2015, 04:58:24 AM »
I recently bought a disc brake conversion kit for my 2006 Classic 500. I did not buy the hub or spokes as I bought a complete wheel on Ebay from India. The instructions were next to useless but I read some good info on this forum which answered many questions. I presume mine is a genuine kit and the part number looks like  B97207 (hard to read on box) and the slave cylinder is marked Pricol. Would some-one please confirm this. Even though I followed the instructions this is my problem. The brake lever pulls in too far and appears spongy. Now before you all start telling me about bleeding I must mention that, if I take the caliper off the bike and re-insert the rubber blocks that were in it for transport the pressure on the lever is perfect and solid like it should be, proving air in the line is not a problem. When I install the caliper with its bracket on the bike and leave the mounting bolts loose, the wheel spins freely and the brake feels and works perfectly. But when I tighten the bolts the pads slow the wheel down a lot (too much drag) and the brake lever pulls right in to the handlebars and if I ride the bike it barely stops me. I have done all that is described regarding the set-up with shims and spacers but I still can't get a good "pedal". (to use an old car term). In the kit there were 4 black spacers, 2 were 13mm thick and the other two were 15mm (or 11mm-can't remember which are on the bike at the moment) Why do they supply these two thickness's of spacer. Also re the shims, where do they go and what is there purpose. I can answer more questions if anyone can respond to this. Meanwhile I will troll the forums to try to get any other ideas. BTW it looks as if the pads are not contacting the full face of the rotor, only the inner circumference which I discovered by rubbing chalk on the disc and seeing where the pads were touching. I'm half thinking it will get better as the pads wear in. Any ideas?

creaky

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Re: Disc brake conversion for Bullet 500
« Reply #1 on: June 16, 2015, 06:27:59 AM »
In addition to what I wrote I said the disc pads were only contacting on the inner circumference of the disc but I was wrong. They do on the left side of the disc but on the right side of the disc it is the outer circumference that is touching. So the caliper must be skewed to one side. I filed those two spacers on a slight angle which was hard to do and that has made a bit of a difference. Maybe I have to use trial and error and file a bit at a time. Surely someone out there has installed one of these kits so I want to know if you had this problem. From past experience with calipers they usually centre and align themselves but this type is a real pain. If I had not ground down my left fork I would re-install my old drum brake.

da punds

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Re: Disc brake conversion for Bullet 500
« Reply #2 on: June 17, 2015, 10:27:34 AM »
Hi,
I used the Hitchcocks kit, but in standard form it wasn't a very good fit. I made a new plate to fit on the inside of the fork leg, with the wholes in slightly different positions to align the pads and disk. I did not use any spacers except on the lower mudguard stay. All my stays are the originals and I did not use the shortened stay. I have not done a high milage on the bike yet as I am in the process of registering it for the road, but it has been a good strong reliable brake in testing and sailed through the MOT test, bettering some modern bikes according to the tester. Here are some pictures not sure if this helps much.
56 Trailblazer Gemini, Super Fireball BigHead, 59 Clipper 570, 39 Model CO + others(BMW, GasGas, Yamaha, Suzuki (rare GSXR-750R)), Mk1a Interceptor project.

creaky

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Re: Disc brake conversion for Bullet 500
« Reply #3 on: June 17, 2015, 04:39:51 PM »
Thanks Da Punds, Those pictures are most useful. Don't suppose you have a template or photo of the plate so I can copy it. I will take some pics of my set-up today and post them. What I did yesterday was to file both 15mm spacers at an angle so one side is 15mm and the other about 13mm. This has the effect of twisting the caliper a smidgeon anticlockwise looking from the top. The pads now make slightly better contact with the disc which I prove by drawing a texta pen line across the disc area, (both sides) and spinning the wheel with light, then heavier brake pressure. Can you confirm that your caliper is identical to mine. Mine has Pricol written on it and came in a genuine RE box.

creaky

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Re: Disc brake conversion for Bullet 500
« Reply #4 on: June 17, 2015, 06:08:17 PM »
Just took some photos. Could be my imagination but your photo looks like the two pistons line up better with the disc contact area than mine, hence your modified bracket. You can see in re4 the rough as guts way I filed the spacers but it is still a work in progress. In re3 you can just see that the plate is slightly angled in to the caliper. As per the instructions though I could not see what the shims that were supplied would do as I presume one would use them on either top or bottom spacer to make it thicker, hence tilting the caliper left or right at the top. I have not fitted the centre mudguard stay.