I'd decided to remove the FSA Tempo square-taper crankset of my 1-year-old road bike to measure & replace its bottom bracket as it's clunking and has little lateral play. The non-drive side crank arm was stripped when I tried removing it with a crank puller, at which I immediately stopped and also gave up removing the drive-side crank to avoid risking further damage.

(Crank Puller) Crank Puller What could've gone wrong? I first threaded the tool by hand without cross-threading and tightened using a wrench to engage the threads fully into the arm.

Edit: Is it just that the 3-piece crankset is badly designed that there's a high-risk of stripping aluminium crank arms?

  • I'm assuming you wound the black part out before fitting to the crank? As pictured it would not go into a crank on a bike. What was the condition of the crank threads before - did you clean them? How many turns of engagement did you get with the crank before applying pressure? What tool did you use to tighten the puller - a hand spanner or an impact driver ? – Criggie Dec 18 '19 at 13:04
  • 1
    What is the quality of the crank puller - I had a cheap one that was a fraction undersized and stripped threads on a crank (fortunately leaving enough that a ParkTool puller still worked). As far as the last bit - 3 Piece has been prove over probably half a century, and still used on new bikes today. It was not phased out for reasons of reliability or serviceability. – mattnz Dec 18 '19 at 19:53
  • 1
    May be a dumb question, but did you remove the crank bolt and any washers first? Was the puller definitely pushing against only the bb spindle and not a surface on the crank arm? – Andrew Dec 18 '19 at 19:53
  • 1
    @mattnz That's quite likely. I realised that it's a cheap eBay one that has some play when fully threaded. I'll try with a better quality one. – Sunny yue Dec 18 '19 at 20:51
  • @Andrew The washer was removed. – Sunny yue Dec 19 '19 at 8:57

There's a few factors that can lead to this problem and range from tool and crank material quality to user error.

If you have a tool made from a weak metal or is manufactured badly (ie diameter is wrong), the threads on the tool can easily be ripped off. Similarly, if the cranks are made from a weak metal, then the threads on the arm can strip off.

User errors can include not moving the inner part of the tool out enough so you end up tighting the outer part of the tool onto the cranks only half way. So when you start winding the puller to press into the bottom bracket, the threads strip.

Another issue could be if someone glued the crank onto the bottom bracket in the past. I don't know if you got the bike second hand or if someone put loctite or glue at some point. But it's possible.

If it's been glued on, you might have to cut the crank off to get the bottom bracket out. Either way, if the threads are gone. I would personally start thinking about replacing the crankset too when the bottom bracket fails, or before if you don't want to risl walking home at some point.

If you're not sure about what to do next, post another question or visit your local bike shop.

  • 3
    It was a combination of weak tool (some threads were already slightly crooked) and operating error. From memory, I don't recall tightening the crank puller fully into the crank arm (only about half a turn using wrench after hand-threading). Either way, I'm replacing the crankset and BB altogether (riding without screw until the arm falls off). I guess it takes one ruined crank arm to learn not to strip those threads. – Sunny yue Dec 19 '19 at 11:13
  • Easy mistake to make, good excuse to upgrade your crankset too! Learn a bit and upgrade the bike, win win! – abdnChap Dec 19 '19 at 11:18

To add to abdnChap's answer, I have encountered a crank arm that had an opening that was too small for my crank puller. This resulted in the puller pushing against the crank arm, rather than the axle.

  • Good point - one might think a cheap square-taper puller is okay for Octalink, but its subtly wrong. There are some that do both but they have a plug/adapter in the end. – Criggie Dec 21 '19 at 2:46
  • That's a good point! I've added it to my answer. – abdnChap Dec 23 '19 at 15:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.