A Mountain Bike Gets A Re-Design.

Most bicycles rolling around this fair land were purchased as a complete, ready to go bike. Any bicycle emporium, ours included, has a selection of Hybrid, Road, Mountain and Comfort models that are great choices to get you out on the trails and the pedals moving. The next step, once the bug has bitten, usually involves another offering from the rack in a slightly higher grade and often to a more specific type of riding. Fast forward a few years, look in your basement and you will see a dozen bicycles that chart your progression through the sport. Most people tend to clear out once in a while and move some of those entry level Hybrids and MTB’s to new homes, others, like my good friend Tom, look in that basement and think ‘what can we turn those into’…

Case in point. Recently Tom decided to re-purpose a pretty standard Fuji mountain bike. The bike was about as generic as an entry level mountain bike could be. Twenty one speed 3 x 7 drive-train, component level that was the common mix of high end hybrid to low end mountain and a very basic mass produced wheel-set. The main feature and plus point of the bike being the frame, more specifically the geometry is actually pretty well designed for the purpose, also it is 27.5 wheel size, of which I am a big fan. So into the workshop it came and out came the clipboard.

Anybody that comes into the store may well have met Tom at some point and, if you have ventured into the workshop you will have seen one of his myriad projects in progress. His projects are always far from routine, they always make me think, they are never easy, they usually involve blending cutting edge modern technology with something that is the opposite. They take me to the verge of insanity before they are finished and yet, when they are and we roll it out for a test ride they put the biggest smiles on my face. These projects are all born the same way, usually on a Sunday afternoon Tom will utter forth the phrase' “ Can we do …..”. I then dutifully pick up my pen and notepad and grab the extra strength Advill. Thus was the start of the Fuji.

On the face of it , a large part of this project was removing stuff. The wheels were going, they were cheap machine built units that had already been trued many times and the hubs were also far from smooth. The front and rear derailleurs and shifters also in the trash. Tom is not a fan of derailleur systems but is a big fan of internally geared hubs, so item one was to use an 11 speed Shimano hub as the gear source. No derailleurs to bend out in the woods. He wanted the biggest tires we could get in the frame and tubeless specific rims to run low pressure. Everything else was pretty much routine, mainly a crank and bottom bracket upgrade to a external bearing two piece crank setup and a Race Face narrow wide chain ring.

The wheels obviously first to build, using the aforementioned Shimano 11 speed internally geared hub. Front hub is a Shimano XT hub. Both hubs are disc brake options. Spokes are custom cut to size and threaded and I used DT Swiss nipples and spoke washers throughout. The rims are Velocity Blunt 35’s and Tom wanted them custom finished in white.

Now here you may be thinking what is the big deal, why all the fuss about a simple wheel build, I see no problem and you would be correct. Tom, however, has a penchant for throwing in a little side note, a kind of codicil if you will. In this case, said wheels needed to not only work on the Fuji frame but would ultimately be used on another frame, a “Soma Riff”. Which of course runs modern 142 x 12 spacing and a thru axle 100 x 15 front. The solution was to machine spacers for the rear and make custom angled key washers for the bolt on hub. The front hub is a standard Shimano XT 100 x 15 thru axle with a machined converter running through it and built in end caps to run a standard quick release skewer.

The next hurdle was a method to adjust the chain tension as we no longer have the rear derailleur handling that part of the equation. Internally geared hub bicycles are basically a single cog at the rear and a single chain ring up front. The chain wraps around both and there is no need for any slack. Frames that are built for this setup will have a method of adjustment at the rear enabling the wheel to be moved fore and aft enabling the chain to be correctly tensioned. The Fuji, obviously, did not have that, which meant a method of adjustment was needed.

20190329_174215.jpg
 
The New Crank-Set

The New Crank-Set

20190329_174146.jpg
20190329_174239.jpg

This is not an uncommon occurrence, lots of comfort and hybrid bicycles have been converted in this way and there are a few devices available for this purpose. Unfortunately they are not up to the rigors of MTB’ing. However, a small company in England makes a heavy duty unit which is up to the task. Sadly, this is made for quick release wheels using standard MTB chain line and not solid axle, bolt-ons which are not using MTB chain lines. More filing and drilling, a few hours and a lot of scrap aluminum later and the unit is re-spaced and able to bolt onto the axle and hanger. Also the chain line issue is corrected front to rear with the addition of a couple of spacers on the new Shimano ZEE crank-set and external cup Hollowtech II bottom bracket.

tommtnalfine (6).JPG

As you can see from the pictures, a mountain bike without derailleurs makes a lot of sense. It just looks a lot cleaner for one but you can immediately see the benefit of not having delicate gear changing devices bolted on to the right side of the rear axle. Lots of frame manufacturers are producing frames that are able to take advantage of hub gears and these obviously make it easier however, with a little patience, a few files and a big pot of headache pills most anything can be done…

Posted on March 31, 2019 .