I’ve finally acquired a piece of bike jewelry that I’ve been lusting over for quite some time now.

The Pro Vis 5, or Cyclotouriste cranks as they’re also called, from TA were rather popular cranks back in the day and continue to be a respected choice amongst randonneurs and tourists. Their unique bolt pattern and diameter allows the cranks to be used as a single, double, triple, even a quad, with any combination of rings available from 26 to 64 teeth.

Multi-Range Gearing

For my purposes, I’ve always wanted a wide-range double, what Sheldon Brown called multi-range gearing. Essentially it’s a crank setup that would give me the range of a triple crankset while still keeping the simplicity of a double, minimizing both the need to shift and the redundancy of duplicate gear ratios.

The Sugino compact double I had been using had a 48/34 combination which was pretty good, but not low enough for touring purposes unless I used mountain bike gearing in the back. I had been using an 11-34 cassette and a Deore LX derailleur. That was fine for a while, but not as elegant as my original 12-27 cassette and Dura Ace derailleur, and I didn’t like the big jumps between the large cassette cogs.

With the TA cranks and 46/26 tooth chainrings, I get an even lower range than previously afforded by the 34×34 combination, while benefiting from tighter shift steps throughout. With a 117.5mm bottom bracket, the large chainring lines up fairly close to the middle of the cassette, allowing me to use all 9 gears in the back while on the large chainring where I do about 90% of my riding. The 26-tooth chainring is used exclusively for serious climbing.

For the seriously geeky out there, here’s a gear-inches chart. With the large ring and the middle cog, the 46×17, I get 72.4 gear-inches. Anybody who’s done much fixed gear riding knows that’s in the perfect range for an all-around cruising gear. While there are some redundant gear combinations with the 26-tooth chainring and the smallest cogs, I wouldn’t use those combinations for a couple reasons. More on that in a bit.

	12	13	14	15	17	19	21	24	27
46	102.6	94.7	87.9	82.1	72.4	64.8	58.6	51.3	45.6
26	58.0	53.5	49.7	46.4	40.9	36.6	33.1	29.0	25.8

Low Q-Factor

The wide-range double gearing was my primary reason for acquiring the TA cranks, but a secondary benefit is their low Q-factor or crank tread, meaning the horizontal distance between pedal attachment points. When set up as a double, they have among the lowest Q-factor of any cranks out there. As Sheldon Brown writes, the benefits are as follows:

For most cyclists, the narrower the tread the better. When we walk, our footprints fall almost in a straight line under the center-of-gravity of our bodies. When we cycle, the “tread” forces our feet to be exerting their force farther apart than they are designed to do. Some theorists blame this for knee and hip problems experienced by some cyclists, but the jury is still out on this. A wider “tread” also creates a greater sideways force when pedaling out of the saddle, so the rider must exert more upper-body strength when riding “en danceuse”.

While I have zero data beyond empirical evidence and my observations are certainly without bias, I can say that the TA cranks feel noticeably better than the old Sugino XDs.

One cautionary note for such a low-q crank is the need to set up the front derailleur just right. When properly adjusted, my front derailleur, an old Shimano 600 FD-6207, has paper-thin clearance from the driveside crank arm.

I need to get the front derailleur this close to the crank arm, though, to get a proper front shift and to prevent the chain from rubbing the derailleur in the big/small combo.

Pushing Derailleur Capacity

When I went in to the local bike shop here in Tottori, Cycle Shop Fukuhama, looking for a new bottom bracket, the shop owner gave me a dubious look upon surveying my TA crank and equipped derailleurs. I knew it was coming. He gave me a warning and amongst a lot of Japanese were the words “total capacity,” and while I couldn’t understand exactly what he was saying I got the gist.

The capacity of the front derailleur is the difference between the large and small chainring. If the difference exceeds the derailleur’s capacity, then the chain will drag on the bottom of the derailleur cage while pedaling in the small chainring. Most modern double derailleurs have a capacity of 15 or 16 teeth. My vintage Shimaon 600 one has a capacity of 18 teeth. The difference between my chainrings is 20 teeth. It’s generally understood that the published capacities for components are on the conservative side and can be exceeded, so I wasn’t worried in this department. Plus Sheldon Brown had gone farther than I had in the past, using a 105 derailleur to shift a 50/28 combo on his Hetchins.

The thing that I was unsure about was whether or not I’d be able to use my existing rear short-cage Dura Ace derailleur. Rear derailleur capacity is based on how much chain slack it can take up, also known as chain-wrap. This is found by adding the difference between the largest and smallest chainrings to the difference between the largest and smallest cogs. For me, that looks like:

(46-26) + (27-12) = 35

My derailleur has a published capacity of 29 teeth. Again, this is a conservative number, but I was definitely past the reasonable margin of error. Any normally thinking person would use a medium-cage derailleur for this, which has a capacity of 37 teeth. I did not want to buy another derailleur.

I had managed to make a 50/34 compact crank with an 11-30 cassette work on my wife’s bike using a short-cage Ultegra derailleur, a 35 tooth difference for a derailleur that also has a 29 tooth capacity (as well as a max cog size of 27 teeth). Additionally, I had read of mountain biking weight weenies who opt for Dura Ace rear derailleurs rather than XTR ones to shave weight, getting the derailleur to even accept cogs up to 32 teeth.

So I tried to convince the shop owner that it was “OK!” and that “people on the internet say it works!” I’m not sure if Sheldon Brown is as renowned here in Japan, so I didn’t name drop. “Test-o! Test-o!” I insisted. He agreed to let me give it a shot and allowed me to borrow the shop tools for the bottom bracket and crank swap.

First I tried running the original chain length that I had on there as was properly measured for the 48-tooth chainring on the Suginos. That was too long, causing the chain to drag on the chainstay in the small/small combo. Too much chain, not enough chain-wrap capacity. So I shortened the chain, finding the length by wrapping it around the largest cog and the largest chainring. Normally, using that method, one would add two additional links for the derailleur to take up. I didn’t. Fortunately, it just barely worked.

This is how the derailleur looks when running the big/big, 46×27 combo. The rear derailleur is almost fully extended. This isn’t a ratio I’d be wanting to ride in regularly, nor should I be since if i need gears this low I’m probably on a hill and should’ve shifted into the small chainring. But if I do accidentally pop into this combo the good news is I won’t be tearing off my rear derailleur. This is a very real threat, too, when your chain is too short.

Here’s the chain in the small/small, 26×12 combo. The chain is pretty saggy, but it does clear the chainstay and under load it doesn’t look this bad. However, in practice I wouldn’t ride this combination anyways, or even the 26×13.

The shop owner was impressed. The moral of the story here is that parts can work beyond their specifications if you’re willing to tinker, but if you tear off your rear derailleur don’t blame me.

Pro Vis 5 Availability

The TA Pro Vis 5 cranks are sadly no longer in production, nor are any similar cranks like the Sugino PX or the Stronglight 49d. They show up on eBay with a fair amount of regularity. In the U.S., N.O.S. TA Pro Vis 5 cranks are available from Velo-Orange. Be prepared to pay a pretty penny. Velo-Orange sells the arms alone (no rings, no bolts) for $235. I paid significantly less that that for mine, but I’m not going to divulge my source (unless you ask really nicely) in case I want more sets in the future.

You may be able to find a pair hidden away in the dusty corner of an older bike shop. Cycle Shop Fukuhama actually had a whole box full of them that they pulled out when I asked them for a bottom bracket. I had no idea. They were selling them for ¥21000, about $210. Still more than I paid.

The good news is that, according to Velo-Orange, a “major crank manufacturer [is interested] in producing a TA Cyclotouriste-style crank set.” I’ll be keeping an eye out for it.

Browse Timeline

• « New Site Layout
• » Sakura Season

Comments ( 16 )

Add a Comment