A Bad Idea - Converting an Old Mountain Bike into a Modern Touring Bike
Submitted by mike on Wed, 09/03/2008 - 05:08
For some reason I decided it would be a good idea to convert the cross canada bike (CCB) into a modern touring bike. It seemed kind of pointless to have the bike just sit there - its only function, to take our visitors on exhausting 5km rides around town. This is a bike that had made two major bike tours, flown about 10000 km in airplanes, and even done a bit of mountain bike racing (in its original unmodified form). How hard could it be? The plan was to use a lot of the extra parts for road bikes that I have lying around, and use them to retrofit the bike. Big mistake. This little article is a chronicle of the trials and tribulations of trying to change a modified mountain bike into a road bike. Though the bike is now pretty nice, and works flawlessly, the excercize was definitely not worth it. It would have been better by a bunch to buy a touring bike.
The mountain bike pictured here shows you more or less what the CCB looked like pre-renovation:
This isn't exactly the same bike, though the frame is the same size and brand. As I recall, the original bike cost around $600, though I modified it pretty extensively as time went on. The post renovation version, the reall CCB, is in the next photo:
In the end this is a pretty nice bike, more or less just what I wanted. I have used it on three weekend tours.
So what happened along the way? To start, there is one obvious reason not to convert a mountain bike - wheel circumference. Despite the fact that we all think we understand tire size -either 26 inch mountain bike wheels, or 700c road bike wheels, tire sizing is extremely arcane and complicated. If you are interested, here is the link to Sheldon Brown's article on tire sizing. The point is that a mountain bike 26 inch wheel has a smaller diameter than a 700c racing wheel. That means smaller circumference, so more rotations of the wheel in a given distance. This means more tire wear.
My cycle computer manual gives the circumference of the 26x1.25 tire that I have on the bike as 195 cm. A 700x25 wheel has a circumference of 210 cm. What this means is that on a 60km ride (6 million cms if I have the right number of zeros), my wheel revolves 30,769 times, as compared with 28,571 times for the 700c wheel. This makes 2198 extra revolutions per ride. This hardly makes any difference on a mountain bike ride, but over a long tour, this will wear out tires faster. Even if you don't travel cross canada, this is going to make a difference.
Of course, I knew enough not to try to put 700c wheels on a 26 inch frame. The main problem, apart from clearance, would be that the brakes would be in the wrong position. I think they would push directly into the spokes, which would stop you really well, once. But 26 inches is okay. They actually make 26x1.25 tires, which are pretty svelte, but still wide enough to work well on cinder paths, and the slightly rougher road conditions one tends to encounter while touring. The wheels I had were supposed to work. All I should have had to do was to change the tires.
So, as you can see, the main change is to replace the mountain handle bars with drop bars, and the shifters with modern lever shifters (the brake lever also shifts gears). A little tape to wrap the bars, no problem. The first difficulty was that the brake levels on road shifters don't pull the cable enough to make v-brakes work - it is basically impossible to keep the lever from bottoming out when you brake. So the v-brakes had to be replaced with cantilevers. Now, cantilever brakes were something I should have had in abundance, I had replaced so many of them with v-brakes - which on a mountain bike, are better in every way. Of course, knowing this, I had thrown out all the obsolescent cantilevers some time ago. So back to the bike shop to buy a new set of cantilever brakes. The plus side of all this is that the canti brakes I found are a lot nicer than any of the old mountain bike cantis.
.Next, the shifters. The CCB is pretty old. It was already being replaced when we took it on a tour of New Zealand in 1995. As a consequence, the cassette in the rear was the 7 speed version. Now, it may be that it is possible to find modern road levers that are compatible with a 7 speed cassette, but I couldn't find one. The complication in all this is that a 8 or 9 speed cassette won't fit on the hub that is made for a 7 speed cassette. So I bought a new wheel (and transferred the old rim, which was in very good condition, onto another bike).
With the new wheel, bars, brakes and shifters, we went for an extended tour or Richmond. In case you aren't familiar with Richmond, it is flat, unlike the rest of British Columbia. As far as I can tell, I did the whole tour (around 50kms) without shifting gears, so everything seemed to work after a little derailleur adjustment. Next trip was to a place with hills, at which point it became obvious that the only way I could get the derailleur to stop complaining and skipping, was to select one gear, adjust the read derailleur, then leave things in that gear. This solution was sort of like buying a broken watch, it worked every once in a while. Back to the bike store to buy a new real derailleur. A 7 speed derailleur isn't compatible with an 8 speed cassette - each click of the shift lever shifts the derailleur just a bit too far for it to align properly.
This is getting ridiculous, but it continues. Next ride, stuff is working until I drop the chain on the front chainwheel to the middle ring. The old chainwheel on the mountain bike crankset is slipping. This isn't too big a problem, I'll just get a new chainring. If you ever buy a chain ring, you have to specify two things - the number of bolt holes (four on most mountain bikes, 5 on road bikes), and something called the BCD, or bolt center diameter. The bolts on the chainwheel form a circle, the BCD is the diameter of that imaginary circle. Again from Sheldon Brown, I learned that you can measure the BCD by measuring the distance between the center of two adjacent bolt holes, then multiplying by 1.7. I did this, checked the BCD against know sizes on the internet, then marched off to the bike store. The owner of the bike store really likes me for some reason. He didn't believe there was a chainwheel of the size I described. I searched everywhere on the internet to find a supplier, couldn't.
Ah well, it would be nice to have one of those new cranksets with the external bearings anyway, they are a lot lighter. Furthermore, if I put on a compact road crank, I would have a nicer set of gears - maybe use the bike for longer road rides as well. So I bought the beautiful crankset with a compact 48 tooth big ring. This one actually worked for part of a ride until the bolts on the small chain ring began to scrape the chainstay. I think you can see from the picture how small the clearance between the inner chainring and the chainstay became with this road crankset.
The bottom bracket shell on modern bicycles is 68mm wide on both road and mountain bikes. The distance from the center of the frame to the middle chainring on a road triple is 45mm, while the mountain bike middle ring should be at least 47.5 mm. So there seemed to be a solution, just shim out the external bearing by 2.5 mm. There is a risk in doing this, since the thread in the cartridge bearing is somewhat less engaged. I was willing to take a chance on this, since I am very light, and don't generate too much power. This didn't work for the reason that is illustrated in the following picture. The crankarm is within 2mm of the chainstay, which will hit the chainstay when it is under pressure, and which will make my heel hit the back of the chainstay. Back to the bikestore for a standard crankset (I forgot to check the crankarm length on the new set, so this was more problems, but for another time).
Surely, the bike must be ready. There is just one remaining problem. I had replaced the fork with the old steel fork that came with bike originally. This one had been cut (weight obsession) to get the bar height right on the original mountain handlebars. This means the bar tops on the new road bars were in roughly a good position for riding. Riding on the hoods, or reaching out to use the road brakes was a bit of a stretch. Also riding in the drops was now uncomfortably low for me. I experimented with a couple of shorter and higher rise stems, but these didn't work. Short stems have a couple of disadvantages - they make the handling very quirky (or at least make it very different from what I am used to), and make the steering very unstable at high speed. So a new fork was in order.
After a lot of searching, I managed to find a carbon fibre rigid mountain fork on the internet. The thing that sold me on this as a decent idea was that the weight of the carbon fork was approximately half the weight of the corresponding steel fork. During the summer, I had met rider who had purchased a very expensive carbon touring bike, and was planning a heavily loaded and long tour with it. This meagre information was sufficient to convince me to do what I wanted to do in the first place and get the carbon fork.
One of the amusing things about the carbon fork was dropping by bike stores to see if they had any such thing. One mechanic on commercial drive was pretty scathing about it - I think he felt that buying a carbon fork of any kind was like buying a convertible car - something for people with an overabundance of money and a shortage of hair. In any case, he let me know what an idiot he thought I was (maybe he has a point judging by the story I have just told), then offered to sell me a great steel fork. He said it was very expensive and high end, though I am sure he just took it off a department store bike that a zombie had brought in. Unlike standard cromoly forks which are mixtures of different metals, this one was pure natural steel.
In any case, the bike now works fine. Here is the list of parts:
- Brake Shifters
- Carbon Fork
- rear wheel
- cantilever brakes
- rear derailleur