One night while browsing through the endless good deals on eBay I stumbled across a front brake rotor from a late model Buell. For those of you that are unfamiliar with the Buell brake set ups they consist of a perimeter floating rotor and a six piston Nissin caliper.

I imagined that it would have quite impressive stopping power so my first thought was, “Could I make it work on my bike?” My bike has no front brake. So the quicker my 250 rear brake can stop, the better off I am. I knew that the Buells have a 17-inch front wheel and my bike has an 18 inch rear, so I had a feeling I could make it work.

I decided to buy the rotor, and ended up winning it for a mere fifty dollars. It even included the mounting hardware. I will be narrating how I made it work for me, but since each bike is different it might not be the best way for every bike. This article is intended to show people that parts don’t have to come in a kit or be made for a specific model to work on your bike. With a handful of creativity you can make anything work.

Designing the mounts and mounting the rotor:

Once I had the rotor I measured the outside diameter and it was just over 15 inches, the inside of the dropped center on my 18-inch wheel is 16.5 inches, so it would fit in my wheel with approximately three quarters of an inch around the outside of the rotor. The mounting hardware consisted of the screws with a special shoulder on them, shims for the steel shoulder bolts to tighten against, ceramic guides for the rotor to slide on, and springs to hold the rotor firmly in the outward position. I wanted the rotor to float because if it was mounted rigid to the wheel, it would surely vibrate. I decided to use the stock hardware; all I would have to do is design a steel mount to weld on the wheel. Ease of replacement was another benefit of using stock Buell hardware. If something should break or be misplaced down the road, just find a dealer.

I researched the stock mounts and found that they are quite simple; they have a threaded hole for the shoulder bolt, a slot for the steel shim that is evenly spaced around the threaded hole, and a blind hole for the spring.

I decided to design the mounts and have them cut by a machinist friend of mine. They can easily be made with a vertical mill, that I have access to, but I knew I had plenty to keep me busy. I was able to determine the spacing between the bolt and the spring by measuring the distance between the wear marks from the spring and the slot for the ceramic guide on the rotor. I guess that’s another bonus of used parts.

Next, I determined the depth for the spring hole by fully compressing the spring and measuring it. I suggest safety glasses when doing this. I made the hole just deep enough to fully compress the spring into it. The threaded hole didn’t need to be blind but I decided that it would look better that way. I made that hole just deep enough to clear the length of the bolt and the tap used to thread the hole. I drew everything in AutoCAD and delivered the drawing to the machinist. A week later I had six steel mounts that were ready to be welded on (Image-2). What’s really great is that they only set me back about $80. Like I said, the guy is a friend of mine.

Next, I started breaking down my spoke wheel. I dismounted the tire and found that a scraper and a wire wheel made an easy job of removing the spoke seal. The seal on this DNA wheel was a foamy rubber that cleaned up nicely. The nipples were then loosened, and in no time the wheel was in 122 pieces. I continued by marking the areas on the rim that the mounts will be welded to and then removed the chrome with a sanding flap wheel attached to an angle grinder. Now I was able to fasten the mounts to the rotor and mock everything up, I definitely liked the way it looked so far (Image-3).

The most crucial step in the whole process came next, welding the mounts to the rim. They needed to be perfectly straight because the rotor is only able to travel .040-inch to compensate for any misalignment. To aid me in this I decided to use a mill table. There won’t be any milling necessary but the T- slotted bed will allow me to firmly clamp everything in place and the spindle will be a perfect spot to mount an indicator. The indicator will be used to make sure everything is straight and concentric.

The easiest way I could find to position the mounts for welding was to bolt them right to the rotor. Instead of using the springs I removed them and used washers on each side of the rotor to hold it in place firmly. This will assure that the mounts can’t slide or move on the rotor. I wanted to have the rotor mounted inside the wheel, exactly one inch away from the edge, so I made some 1-inch spacers to clamp between the rotor and the mill table. Later the wheel was clamped directly to the table which gave me the offset I wanted. The important thing was strict even surface all the way around.

The rotor was clamped to the mill table with the clamps positioned around the outside of the rotor first. Next a test indicator was attached to the spindle and used to center the spindle inside the rotor. This can be achieved by moving the table but once the spindle was centered the table could no longer be moved. After the spindle was centered the test indicator could be repositioned to measure the top surface of the rotor, to test whether it was flat or not. Mine was, if it wasn’t it would need to be shimmed. A cheap set of feeler gauges worked for a variety of steel shims, and if the price was low enough, I didn't feel bad about cutting them up. Once everything was perfect the clamps were moved, one at a time, to the inside of the rotor to make room for the rim (Image-4).

Mounting the rim was fairly simple. It was clamped directly to the table, over the rotor. The rim could slide around on the table while centering it under the spindle. It was important that I didn’t move the table because that would throw off the centerline of the rotor, and I would be forced to start the centering process over. I first measured around the inside of the rim until it was centered; I then lightly clamped it in place (Image-5). You don’t want to over torque those clamps because they will easily bend the rim. After I knew everything was concentric I measured the top edge of the rim to make sure it was also flat.

Once everything was clamped, I began TIG welding by tacking each mount in several spots before fully welding any of them. Since I designed the mounts in AutoCAD they were the perfect length. They came right out to the surface of the rim all the way around leaving just the slightest gap. I welded everything that was possible while it was still clamped in place, that way nothing could be pulled out of position by the heat. The table could be moved to allow extra clearance around the spindle, once everything was centered and clamped (Image-6). I was able to weld three sides of each square mount while it was clamped in place, the fourth outer side needed to be welded when it was unclamped.

After the welding was completed on the mounts and they were thoroughly inspected, I stepped up for a test fit. Everything worked out great. Everything lined up and there was .040-inch of travel in the floating rotor. Once I reinstalled the springs the rotor stayed in the outward position and could easily be pushed to the inward position.

The welds fully penetrated the steel rim all the way around the mounts (Image-7). One of the largest benefits of TIG welding was the ability to add heat without material. That aspect guaranteed full penetration from start to finish. With the fabrication finally done on the rim it was ready to be powder coated (Image-8). The outer edge of the rotor mounts sat flush with the edge of the dropped center in the rim, that was why I wanted one inch of offset on the mounts. There was still one thing that I want to do to the hub before I send it out to be powder coated.

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