Building a Coast to Coast Trail bike: Part 1 – Prepping the frame
This is the first part in a series detailing a Coast to Coast Trail bike build. Also, some of the things described in this article are probably bad ideas and should be done at your own risk.
Scrolling through Facebook Marketplace one day, I came across a Trek Multitrack 720 frameset for $15. I had been looking for a new project and decided this was it. I wasn’t sure what I was going to do with it, except that I wanted it to fit 700c wheels and up to 45mm tires.
My first idea was to build it up with BMX bars and front and rear racks as a pub bike/grocery getter. Then I thought of an adventure/bikepacking bike, which led me to the idea of building a Coast to Coast trail bike. This bike will be outfitted purposely for the Florida Coast to Coast trail.
While the frame didn’t have any dents or visible rust spots, I could tell that it had been sitting outside for a while. It was missing handlebars, brake and shift levers, seat post, saddle and wheels, which didn’t matter as the first thing I did was take off all of the remaining parts and start sanding down the frame.
I used 120 grit sandpaper and a detail sander for all the big tubes. To remove the paint around the cable guides, tube joints and other hard-to-reach spots, I used a wire brush set attached to the end of a cordless drill and then finished it all off with some 200 grit sandpaper. I probably could have skipped the sanding step and just primed over the exiting paint, but since I was making some other changes to the frame, I decided sanding would give the best finish.
Sanding a bike frame takes time and plenty of patience. It’s difficult to get all the paint off of all the nooks and crannies. I would spend half an hour a few nights every week working on it, but didn’t have the patience to get it all done at once. It probably took a month or two of infrequent sanding sessions to get it done.
On a trip like the Coast to Coast trail, having easy access to all your stuff is super important, so I decided a top tube bag was a must. Many top tube bags mount with velcro straps, but I really wanted mine to be bolt mounted. Bolt mounted bags seem to be sturdier and also look much nicer.
There were two problems with mounting a bag on the top tube. First, my frame didn’t come with top-tube mounting bosses and second, the rear brake cable guides were located right about where the bag needed to be mounted.
The solution? Add bosses to the top tube and move the cable guides out of the way. I mulled over the idea of going with an internally routed cable, but decided against it for this project. Also, the internet is definitely divided over the idea of drilling holes into your bike frame. Because this is an old steel frame that cost about the price of a six pack of beer, I was not too worried about ruining it. But fair warning that if you try this, it could be catastrophic.
There are two options for adding water-bottle bosses: brazing or using rivet nuts, also known as rivnuts. Both options involve drilling a hole into your frame and attaching the bosses either via heat and solder or via compression. After lots of research, I chose rivnuts, as they are the easier of the two options. Brazing doesn’t look too hard and I promised myself that if I ever do this again, I’ll invest in the tools to “do it the right way.”
Before I could add the bosses, I needed to remove the cable guides that were in the way. To do this I needed a way to secure the frame so it wouldn’t move. I built a jig to hold the bike upright using a piece of plywood and some scrap 2x4s. I drilled a 2×4 next to each chainstay and then placed another board across the chainstays and drilled it into the 2x4s.
To remove the cable guides, I used an angle grinder and a cutting/grinding disc. Up to this point, I’d never actually used an angle grinder, so I cut a little too deep on the first try and ended up with a small gouge in the frame. Be warned that this produces a lot of sparks, so if you try it, take the necessary precautions so you don’t burn yourself or your house down.
A standard placement for top tub mounting bolts doesn’t yet exist, although there seem to be a few options that bag manufactures are using. I drilled the first hole about 100mm from the inside edge of the head tube and the second hole 2.5 inches (64mm) away. This is standard water-bottle boss spacing.
Without a drill press, It’s nearly impossible to drill perfectly aligned holes in a round tube. I used a small bit to drill a pilot hole and then I used a 7mm drill bit to drill each hole for the rivnuts. Getting the pilot hole started was a bit of a challenge, but once it’s drilled, the larger hole was easy. In hindsight, I should have created a jig from a piece of wood or steel plate.
Rivnuts are basically threaded tubes with a top lip that are inserted through a hole in the material they are mounted in. To secure them, they are pulled up from the bottom, which compresses them around the material.
Water-bottle bosses use an M5/0.8 rivnut. Rivnuts come in all sorts of different metals, but stainless steel seem to the be most popular for this application. There are also many different rivnut setting tools. One option uses a squeeze handle, but I bought the EZ-NUTUL, which uses one wrench to hold the tool and another to compress the nut. It’s one of those situations where a third hand would definitely help.
I wasn’t happy with the rivnuts that came with the tool, so I bought a pack of 100 stainless steel rivnuts for $11.
Attaching the rivnuts was actually quite simple. I mixed up some two-part JB Weld and put it into the hole I made in the frame, screwed the rivnut onto the end of the tool and coated it with more JB Weld and inserted it into the frame. I secured the body of the tool with a crescent wench and then inserted my torque wrench (set to 6nm since that’s as high as it goes) and started wrenching until it stopped. The rivnut tool says the recommend torque for M5 nuts is 3-7nm.
Once the nut was set, I unscrewed the tool from the nut and wiped off the JB Weld with rubbing alcohol. I repeated this for the other holes. To deal with the little gouge I made with the grinder, I spooned some JB Weld into it, let it dry and then sanded it down.
The fork was a similar project. I sanded it down and then added two water bottle bosses on each leg, which will allow me to mount racks and/or water bottle cages.
This article from bikepacking.com served both as inspiration and a handy how-to guide.
Next up: Painting the Coast to Coast Trail bike frame