Keeping an Eye on Cranks

Keeping an Eye on Cranks

I spend so much time assembling test bikes, testing components, etc., that I have little time to work on my own bikes. Fortunately, my Alex Singer (above) has been very reliable, even though it is 38 years old and has been ridden at least 200,000 km (120,000 miles) in its lifetime, mostly under its first owner.
Before our Flèche ride, I adjusted the front brake pads, which had worn and started to touch the tire. After that 600 km ride, the chain was overdue for replacement. I replace the chain every 1600-1800 km to limit wear on the hard-to-replace freewheel cogs.
As so often, I only got around to replacing the chain the evening before the next big ride, our club’s 400 km brevet. After taking off the chain, I inspected the chainrings. The large 48-tooth chainring had worn so much that the teeth were very thin at their tops. In the photo below you can see the roots of the teeth, where they still feature their original thickness.

I was pondering this rapid rate of wear when I realized that I last had replaced the chainring four years ago. Since then, I had ridden the Singer about 25-30,000 km. Considering that I use the big-big combination frequently, which runs the chain at an extreme angle, that is a very acceptable rate of wear from the TA chainring. The small 32-tooth ring sees much less use. It remains in very good condition. Fortunately, I had a spare 48-tooth chainring, and it was a quick job to replace it.
On TA “Pro 5 vis” cranks, you need to remove the crank to replace the chainrings. In any case, it is a good idea to take the cranks off your bike every few years. As I unscrewed the crank bolts, I noticed that one had loosened a bit. Next I checked the bottom bracket. Four years ago, I had pressed new bearings into the Alex Singer bottom bracket, and as expected, they still spun smoothly. The first set of bearings had lasted 34 years, so I hope to get similar mileage out of these. (I really don’t miss the annual overhauls of cup-and-cone bottom brackets.)
After removing the chainrings from the crank, I inspected the cranks for cracks. To my shock, the left crank had a nick, from which two small cracks seemed to emanate (arrows in photos below). Or was it just a scratch?

I decided to remove the nick and see how deep the crack/scratch went. I clamped the crankarm between two small wooden blocks in a vise. A few file strokes removed the nick and cracks/scratches (see below), as they were just on the surface of the crankarm. If it had been a deep crack, the crank would have been retired immediately: A broken crank is no laughing matter. Sorry for the mediocre photo quality, but the main focus was to get the bike ready for the ride, not to work on the lighting for the photos.

Classic TA cranks are not anodized, so restoring the finish was easy. I started with “wet-and-dry” sandpaper (400 grit up to 1200 grit) under a trickle of water to remove the dust and prevent the sandpaper from clogging. I used the opportunity to lightly sand the remainder of the crankarm as well. Then I polished it with some polishing compound on an old rag. When I re-checked the polished surface, the cracks had disappeared completely. The other crankarm also had a few nicks, which I also filed and sanded off. After polishing both arms, I rubbed on a little car wax to protect the cranks’ and chainrings’ finish. The shiny cranks match the new chainring and look nice on the bike.

Installing the new chain and oiling it completed the maintenance job, which took about 90 minutes. And the bike worked flawlessly during the long ride the following day.

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Comments (20)

  • Dan

    Thanks for sharing this experience. It’s this kind of informative post that is making this blog a valuable resource.

    May 30, 2011 at 8:16 am
  • tim potter

    Wondering why you often ride in the big-big gear combo when you know its prematurely wearing out your drivetrain? Why not run a triple to avoid the problem? Also, I believe it was Sheldon Brown who’s written that the best chain lube is the stuff chains come with when new, so I’m curious why you oiled your new chain?

    May 30, 2011 at 9:31 am
    • Jan Heine, Editor, Bicycle Quarterly

      I use the 48-tooth chainring almost exclusively, because it allows me to ride most terrain without front shifts. A triple would defeat that purpose, and it also would increase the tread (Q factor) of my cranks. (A 46-tooth ring would be better, but the braze-on front derailleur of my Singer would sit too high.) I am willing to accept that I have to replace my chainring every 25-30,000 km. How long do your chainrings last?
      If I don’t oil my new chain, it will start squeaking after a few rides in the rain. I prefer to oil the chain when it is new, rather than re-apply lubricant later and wash dirt into the links. And I hate squeaky chains!

      May 30, 2011 at 9:49 am
      • Bill Raymoure

        Jan, for a new chain do you remove the factory lube first with a degreaser or do you just put your own on top of the factory stuff?

        June 3, 2011 at 8:25 am
        • Jan Heine, Editor, Bicycle Quarterly

          I just put on the new stuff on top of the factory lubricant. It seems to work fine. As I mentioned I usually don’t re-lubricate the chain during the 1600 km that I use it, unless I ride through a lot of rain.

          June 3, 2011 at 8:33 am
    • Chris Cullum

      I remember that comment from Sheldon and recently took it to heart. This season I completed a Super Randonneur series that was particularly wet and I deliberately used my old drivetrain from last season figuring a new one would get worn out from 1500km of bad weather. After the rides I checked my chain and it was at 1/8″ or .75 over length. I replaced both the chain and cog set which was also close to replacement. Installing the new chain I kept the factory lube on the chain and did not oil it. I rode a little over 100km before I set out on a 400k brevet. This brevet was again wet and the chain was making a fair bit of noise during the ride (which I don’t normally get with full fenders and Boesheild lube). At home at the end of the ride I checked the chain and it was already at the replacement threshold of 1/8″ or .75% stretch. I normally get about 2000km before this level, just over 500km is very poor. Anyway this is just a data point that in wet weather the original chain lube may not be the best bet. The chain for reference was a Sram PC971 which is what I typically use.

      May 30, 2011 at 10:12 am
  • Steve Palincsar

    Jan said:
    Considering that I use the big-big combination frequently, which runs the chain at an extreme angle
    Just how extreme an angle can there be with a 5 or 6 speed freewheel? And how does it compare with the angles commonly used on 9, 10 or 11 speed bikes? If it’s a concern, could you do as Alex described the other day on the iBOB list, and center the big ring over the freewheel, and use the small ring only with the 2 or 3 largest sprockets? I presume if you’re always on the big ring, that’s how you use the small ring now.

    May 30, 2011 at 3:28 pm
    • Jan Heine, Editor, Bicycle Quarterly

      The Singer rides and shifts very well, and if my chainring has to be replaced every four years, then I can live with that. Ideally, I’d do what you suggest, and center the chainline on the big ring, but that would involve a shorter BB spindle for the Singer bottom bracket. I could machine one from an SKF bottom bracket spindle (it has enough material for the bearing seats and shoulders), but for now, the Singer works well enough. And I’ll save the ultimate in optimization for a custom bike in the future.

      May 31, 2011 at 9:14 pm
  • paul priest

    I noticed you use old Look pedals. Do they have long bearing life? Can you still get cleats for them?

    May 30, 2011 at 5:02 pm
    • Jan Heine, Editor, Bicycle Quarterly

      The bearing life on old Look pedals is amazing. They don’t seem to wear out. I don’t know about cleats… eventually, a tab on the retention mechanism breaks. I usually use Shimano’s PD-A520 pedals, but the bearings seem to get sticky, and then my feet begin to hurt. We should test their PD-A600, which supposedly has better bearings, but Shimano are so difficult to deal with that we just haven’t got around to buying a set.

      May 30, 2011 at 7:58 pm
      • Chris Cullum

        I had a pair of those Looks back in the day. Solid pedals, IIRC they weighed something like 550g. The spindles did eventually get crunchy on mine. Those pedals are OOP for a long time and I would be surprised if you could get cleats. You might have better luck finding the entire pedal used or NOS. I find it’s a little misleading that these are the pedals that are used for the standardized bike weights in BQ as most randonneurs I know use pedals that are 1/2 the weight of these.
        The A520 pedals do have poor quality bearings. Mine developed play and when I went to rebuild them I found something like 22 microscopic balls. Both rows are far out toward the end on the pedal so that the bearings are not well supported. It was an extreme pain to put all those little balls back in place. Happily the races and balls seemed to be in good shape. The other side I just squirted more grease in and adjusted the bearing tension without completely disassembling them.
        I have a set of A600 pedals and the bearings seem to be of better quality. I believe it is the same spindle as the XT MTB pedal. On both the A520 and A600 the spindle could be shorter as both pedals move the foot out and increase the effective Q-factor.

        May 30, 2011 at 8:19 pm
        • Jan Heine, Editor, Bicycle Quarterly

          I find it’s a little misleading that these are the pedals that are used for the standardized bike weights in BQ as most randonneurs I know use pedals that are 1/2 the weight of these.

          We’ve been thinking about this. It’s just that these were the pedals we used when we started testing bikes. And to keep all bikes comparable, we’ve kept the pedal weight the same. Otherwise, you’ll suddenly get a bike that is 1/2 lb. lighter for no reason except that the standards have changed. But eventually, we may want to change this…

          May 30, 2011 at 8:58 pm
    • Conrad

      Concerning pedal bearings: I have old shimano 105 pedals which were made by Look on my road and track racing bikes and they are great- never wear out. The cleats are still readily available. I use eggbeaters for cyclocross racing because the mud clearance is so good but the bearings stink. Don’t last much longer than a season. On the positive side it is cheap and easy to rebuild them; replacement bearing kits are readily available for all models.

      May 30, 2011 at 10:35 pm
  • Garth

    Hi Jan,
    I’m curious if you review the old Sugino PX cranks in one of your Vintage Bicycle editions?
    One of them worked loose, but I might not have torqued it properly. We’ll see if it becomes loose again.

    May 30, 2011 at 8:06 pm
  • Conrad

    I’m wondering how long a freewheel lasts you? My commuter setup is an 8 speed cassette (used to be shimano XT, now a SRAM, durability seems the same) with a SRAM 8 speed chain. I replace the chain at the 0.75% wear mark which is usually around 1500 miles and I still have to replace the cassette after every third of fourth chain, because a new chain will start skipping. Is there a better way?

    May 30, 2011 at 10:18 pm
    • Jan Heine, Editor, Bicycle Quarterly

      I haven lost track how long my freewheels last, because I tend to switch freewheels a bit for different periods of year and events. I sometimes start out with a 13-24 and only switch to a 13-21 later in the season. When I was racing, I regularly got 30,000+ km (20,000 miles) out of freewheels before a few individual cogs started to show wear. They weren’t skipping, but since they were easy to replace, I did put in a new one. Actually wearing out a freewheel cog hasn’t happened to me in so long I don’t even remember.
      Of course, I use (and used back then) Dura-Ace 6- and 7-speed freewheels. However, the cogs aren’t much thicker than 8-speed ones, and the 7-speed chains are the same. So 8-speed shouldn’t wear that much faster. Have the cogs changed? Or is it an issue of grit on the chain. Obviously, my bikes now use full front fenders that reach down far enough to protect not just my feet, but also the drivetrain, from road spray.

      May 31, 2011 at 7:40 am
      • Conrad

        I’m not sure if the cogs are changed because I’ve never used Dura Ace 6 or 7 speed freewheels. The 8 speed cassettes do have ramps machined into the cogs, like the newer 9 and 10 speed stuff. My rain bike has full fenders. I do use a really thick syrupy chain lube that may attract more debris- maybe that is the problem. Also I never really clean the chain, I just wipe and relube until it stretches to the 0.75 mark and then replace.
        Where on earth do you find old Dura Ace 6 and 7 speed stuff? Its hard enough to find an 8 speed road cassette, seems like SRAM is about the only choice now.

        May 31, 2011 at 8:59 pm
        • Jan Heine, Editor, Bicycle Quarterly

          I stocked up years ago, buying lots of good-condition freewheels. I don’t like riding old equipment that cannot easily be replaced, but so far, I haven’t had to dig too deep through my box of freewheels.

          May 31, 2011 at 9:10 pm
  • Tim

    Jan, considering how much discussion there’s been here re: the issue of chain care, lubricants, wear, etc. seems like an excellent topic for further research. Would greatly appreciate you doing one of your famous controlled scientific studies on this as we’re obviously basing a lot of opinions on our experiences which may or not be repeatable around the world/ supportable by facts.

    June 3, 2011 at 9:47 am

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