Single Chain Ring Considerations

A Canadian Peugeot with single chain ring and spider mounted chain guard.

Most of my bikes have multiple chainrings – double or triple.  I’ve gotten so used to the shifting patterns on my bikes, that I don’t think much about the double rear shifts that might be required to maintain cadence when shifting the front ring, nor do I worry that I might have to trim out the front derailleur from time to time (I use friction shifting for the most part).  But, that is not normal.  I am a geek, and the vast majority of cyclists are not (no offense to the wonderfully geeky readers of this blog).  Non-geeky cyclists are probably drawn to the seeming simplicity of a single chain ring up front.  Less shifting equals better riding, right?

The only bike in my constellation of daily riders with a single chain ring up front is my 1987 Panasonic MC 7500 – a bike I acquired as a frame and fork and then built into a city commuter.  Even though it’s the heaviest bike I ride, it’s the one that gets the most daily use.  One of the reasons for its appeal as a commuter bike is the simplicity of its equipment.  It has a rear freewheel with 6 speeds and plenty of range, plus a single chainring up front.  I installed a $7 ratcheting no name friction shifter on the handlebar to move the rear derailleur, and the shifter works intuitively with the lower end but perfectly decent Shimano Acera long cage rear derailleur.  At first, I didn’t use a chainkeeper, but experienced the chain jumping off on a few occasions, so decided to install Paul’s chainkeeper.  Chainkeepers are designed to keep the chain from falling off either side of the front ring of a single chainring bicycle when shifting vigorously or oddly, as can happen when unexpected events occur while cycling, and especially while commuting.

After a few mishaps with Paul’s chainkeeper, the most recent of which caused me to re-locate this device, as shown above (it is now a “fender keeper”), I have been thinking about the way returning cyclists, as well as those not mechanically inclined might have dealt with my recent near disaster.

I was cycling home after a day at work, heading downhill when suddenly my cranks would not turn.  Since I was still freewheeling I knew that the problem was at the front of the drive train and I immediately suspected that the chainkeeper had become dislodged and contacted the chain.  I pulled over immediately, and after confirming this was true, disengaged the chainkeeper, as shown above.  I rode home with no further issues, but shifted very gently, hoping my chain would not jump off the front ring, and all went well.  It is unlikely that the average cyclist would have been able to diagnose this problem, much less solve it.  Nor should they really need to.  Instead, the marketplace needs some much better solutions to the single chain ring challenge.

1947 Camille Daudon with single chainring

Vintage bicycles with single chain rings don’t need chain keepers.  Why?  The rear freewheel will have only 3 to 5 speeds for the chain to navigate, causing the chain movement to be very manageable as compared to modern drive trains with 8 – 11 speeds at the rear.  For commuters, it’s not necessary to have tons of gears, but instead to have enough gear range to accommodate the hills you encounter on your commute.  So, 3 to 5 speeds might be all you need, if the gear range is appropriate.

Paul’s Chain Keeper

The problem with many chainkeepers, such as Paul’s, is that they work TOO well. Since they are designed to prevent chain movement, there isn’t enough clearance to provide for even the slightest change in chain angle, and they require extremely precise adjustment that can go out of whack with even a small mishap.

One solution is to put a spider mounted chain guard on the crank, and then use a seat tube mounted chain watcher on the other side.  Or, you can put two spider mounted chain guards on the crank – on either side of the chain ring.  Sheldon Brown published an article for Adventure Touring Magazine in 1999 which deals with chainring issues for touring bicycles, but he also includes some good advice on anti-derailment devices that can help prevent the chain from dropping off a single chain ring.

If you are going to convert your bike to a single ring up front, here are some points to consider:

Shorten the Chain – you will want to remove links from your chain in order to accommodate the switch to a single ring up front.  This will help to prevent chain slap and chain jump.

Decide about a chainkeeper vs. chainwatcher vs. chainguard(s):  Depending on the width of your rear cassette or freewheel, you’ll need to think about the demands you are placing on the front ring.  If you are trying to go with an 11 or 10 speed system at the rear, then you’ll need something to help deal with the extreme angles that the chain will experience at the front ring.

Make sure the rear derailleur can handle the range: when switching to a single ring up front, you often need to increase the range of your rear cassette or freewheel.  If you do so, make sure that your rear derailleur can handle the the bigger cogs.  You may need to adjust your b-screw, or invert it (a la Sheldon Brown) to get the clearance you’ll need for the larger cogs.

Or – shift carefully and don’t worry about any of this.  Occasionally your chain may fall off, and then, you’ll put it back on again.

Quando/Quanta Hubs Long Term Update

Quando/Quanta hubs

Last week, while getting ready to climb a steep section of my route home, I vigorously shifted into my lowest gear while riding my 1987 Panasonic MC 7500 winter bike.  That resulted in my chain over-shifting and falling into the spokes.  Uh oh!  It took about 15 minutes for me to dislodge the chain and ride home, after turning the bike upside down for diagnosis and repair.  I had to remove my Paul’s chain keeper in order move the chain, as it had gotten wedged between the chain keeper and chain ring.  Still, I wasn’t worried because I stopped the bike the minute this occurred, and didn’t expect that I had done much damage.

I had built this wheelset about a year and a half ago using Quando cartridge bearing hubs, laced to SunRims CR18 rims. For the few weeks preceding this mishap, I had been hearing a clunking noise in the rear of the bike, occurring while pedaling and coasting, but louder when riding at speed.  It took a while for me to clue in to what the noise might mean.  At first, I thought it was the saddle rails or seat post, because I only heard it when working hard at accelerating. But then I began hearing it while coasting.  Then I thought it was the replacement freewheel I was using – perhaps the freewheel cover plate was coming loose and the body was clunking around.  Bicycle noises can be maddening to diagnose!

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Spoke damage.

When I finally had time to get the bike into the shop stand, I was saddened to see that the chain had damaged all the drive side spokes in my little mishap.  Doh!  Good thing I checked.  So, I proceeded to disassemble the wheel, all the while wondering whether I had the right length replacement spokes (that’s why you always buy extras…), and questioning whether I was up to a wheel building experience on this nice sunny afternoon.

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Once I had the spokes out, which I removed very slowly and methodically (spokes under tension are dangerous projectiles), I examined the hub body.  It looked pretty good.  Okay, let’s build the wheel again with some new spokes.  Fortunately, I had 9 spokes on hand of the exact length needed.  In a sort of thoughtless way I began turning the hub axle, perhaps in an attempt to delay the inevitable.  That’s when I heard a strange grinding/clicking sound.  I held the hub close to my ears to listen further.  Finally, the sound stopped, but was replaced by a very tight spot when turning the axle of the hub.  Very tight.  Not normal!  The source of the clunking was now illuminated.  But, what to do?

I could attempt to diagnose the cartridge bearings, or I could try to find the right rear hub with 126mm rear spacing (mission impossible?).  The latter turned out to be the best course of action.  Velo Orange sells a 126mm rear hub with freewheel threads and 36 holes – just what I needed.  Mission accomplished.

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Meanwhile, I removed the dust covers on the Quando hubs.  Perhaps with this winter’s especially rainy and muddy rides, bad stuff had made its way into the cartridge bearings and could be simply cleaned out.

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No such luck.  The bearing grease (which has been removed in the above photos), was pristine.  Undaunted, I decided to clean the bearings and re-grease them, to see if by some chance that would change the hub’s tight spot (which was illogical of course).

The bearings on these Quando hubs are either bad, or not properly adjusted, or the races and cups in the hubs are damaged.  Cartridge bearings do not work in the same way as cup and cone style bearings.  The latter’s adjustment is achieved by the correct position of the cone against the cup, something most experienced mechanics can do easily.

Cartridge bearings are engineered differently.  The preload adjustment is done by the factory when the bearings are pressed into the hub.  If it is wrong, correcting it can be a problem.  A cartridge bearing hub’s races can also be damaged by improper installation (or removal).

While it may be possible to have these hubs diagnosed and repaired by a mechanic with the right equipment, the cost to do so is not justified here (throwaway technology strikes again).  Now, I will try to look forward to rebuilding the rear wheel with my new VO hub, when it arrives.  The front hub spins just fine and has no issues, for now.  But, given this experience, I will plan to monitor it in the future.