Saturday, June 15, 2013

Loveland Pre-Ride and Time Trial Brake Rebuild

Pre-rode the Loveland Lake to Lake course yesterday. It's a nice course, with a few tricky sections - mostly on the descent side.

It's about 29mi with about 1700 ft of climbing. Most of that climbing is probably around a 1-2% grade mostly, with a couple 4-6% short sections. Very easy to stay aero for most of it. There are a couple descents where I easily hit around 45mph - even if for a very short time. Was on the aero bars and it was a bit windy. Probably will opt for the horns if it's that windy on race day. That cross wind tweaking on the front 60mm race wheel is a little unnerving - and it's nice to be near the brakes when others are around and you're descending that fast. Loss of time anyway is pretty minimal there. Just pedal harder on the uphill ;-)

After the ride I decided to swap out my PowerTap wheel with my race wheel (HED Jet 6), so that I could get in some time just testing to make sure everything is adjusted properly in the next week. Plus, I kind of know what TT pace needs to feel like at this point.

Also needed to adjust the front derailleur mount as it was a bit loose and the derailleur was angling down a bit. Decided to tackle the rear brake because the tension adjuster on the right side wasn't working. My suspicion was because the brake rides under and behind the rear bottom bracket, that a bunch of crap had made it's way into the adjuster mechanism.

Technical Details on Rebuild of the Brake:
The brakes are actually made by a company called TRP ( Looks like they OEM them for a number of TT bikes - like the Specialized Transition I have.

Here's the location of the brake - looking up from underneath the BB. Thaaaaat's right.

Really getting at it necessitated removing the front crank. Trust me, in the long run - you want to do that. It takes like 2 minutes to pull the crank - and a lot longer to try and work the brake otherwise.

Pulled both sides off and disassembled. It's a pretty simple mechanism - although I wish there was a better picture of how it works so I could post it. Basically there is an internal thick washer that one end of the spring inserts into with a detent that the adjuster barrel screw pushes on. The other end of the spring inserts into the frame when you push the brake on the post. Move the adjuster screw in and out and the detent puts more or less pre-tension on the return spring.

Here's a side view with an arrow pointing to the adjustment washer.

The cavity where that wash sits just collects crap from the road, causing it not to rotate smoothly. So it sticks and keeps too much tension on the spring, or it doesn't move at all. I wish had taken a picture of it while I had it apart. There aren't any good exploded views out there, but it's a pretty simple mechanism.

I basically had to spray the heck out of it with WD-40 and used a tooth pick to rotate it until it was free enough to pop it out into my hand. Then some de-greaser into the cavity and parts to clean them all up. Then greased it up and put it back together. 

Reassembly and adjustment of the now smooth and clean brake arm assembly went pretty quickly. Although adjustment of the pad to properly hit the HED Jet C2 rim and keep it off the carbon fairing and away from the tire of course is always something you want to check and double check. And you have to peek around the frame with a bright light to properly see it.

I was glad to have spent the time to really clean it up properly. I'm guessing it will not need service for a year, depending on the riding weather.

And since I was feeling so mechanical, here's Luke's breakfast. It's two speedboats made from banana, Nutella, strawberries, coconut and a couple raisins. The boathouse is cinnamon toast and sausages. 

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