Square taper crank fits too far on BB axle

[XC26]

In the last few years I've had several instances in which a brand new square taper crank slides too far onto the BB axle with the result that the retaining bolt is flush with the end of the BB axle and the crank arm can not be tightened up sufficiently. This has occurred on newly purchased bikes and usually on either the left or the right crank arm but not both - it's not a JIS vs ISO issue. Usually, one crank arm is a perfect fit and the other slides on too far. I've even noticed it with a manufacturer-paired crankset and BB. Has anyone else come across this? Is it poor quality control? The components in question are branded from respectable manufacturers.

 

[Dusty Bin]

THey are all made to a pattern, so differences in QC are not really a problem - there must be some other issue with your crank...

 

[RecordAceFromNew]

In the last few years I've had several instances in which a brand new square taper crank slides too far onto the BB axle with the result that the retaining bolt is flush with the end of the BB axle and the crank arm can not be tightened up sufficiently. This has occurred on newly purchased bikes and usually on either the left or the right crank arm but not both - it's not a JIS vs ISO issue. Usually, one crank arm is a perfect fit and the other slides on too far. I've even noticed it with a manufacturer-paired crankset and BB. Has anyone else come across this? Is it poor quality control? The components in question are branded from respectable manufacturers.

If what you described happened then certainly something is badly wrong, may it be design, sourcing, implementation or whatever. XC26 you don't happen to be talking about Apollo's from Halfraud do you?

 

[XC26]

If what you described happened then certainly something is badly wrong, may it be design, sourcing, implementation or whatever. XC26 you don't happen to be talking about Apollo's from Halfraud do you?

Hi RecordAceFromNew,
I've not had this issue on an Apollo; in fact, some of my lower end bikes have had really good fitting square taper cranks. It's occurred on 3 bikes I bought that were fitted with "SunTour" alloy cranks and another fitted with "First Components" matching crankset and BB. With SunTour, it was always the left crank that slid on too far and with First Components, it's the right crank. Also, swapping the L&R cranks on the BB shows that the fault is with the crank arm and not the BB.

 

[lukesdad]

Don't bother making shims out of a drinks can.

... not untill you've drunk 'em anyways

 

[RecordAceFromNew]

Hi RecordAceFromNew,
I've not had this issue on an Apollo; in fact, some of my lower end bikes have had really good fitting square taper cranks. It's occurred on 3 bikes I bought that were fitted with "SunTour" alloy cranks and another fitted with "First Components" matching crankset and BB. With SunTour, it was always the left crank that slid on too far and with First Components, it's the right crank. Also, swapping the L&R cranks on the BB shows that the fault is with the crank arm and not the BB.

Interesting. Most Suntour forks I have come across are pretty poor made to a price, but hitherto their chainsets I have seen work fine, just a bit heavy, but it is probably fair to say the make is now merely a shadow of its former (60's/70's/80's) glory. Definitely something is wrong with the chainset or the bb or both if the crank bolt can be flush with the axle.

 

[andrew_s]

the make is now merely a shadow of its former (60's/70's/80's) glory.

Current Suntour is unconnected to old Suntour, which went bust with the brand name being sold on by the liquidators as an asset in a similar fashion to Karrimor or Muddy Fox now being just Sports Direct brand names to put on the output of J.Random Chinese factory.
Old Suntour was top quality kit, up there with Dura-Ace or Campag Record. I'm still using an XC-Pro front mech (with bar-ends). Suntour tended to sell at cost plus a markup and didn't generate enough profit to fund the research to keep up with Shimano, and lost out big time when indexed shifting came along.

 

[Steve H]

I experienced a problem when I replaced my Suntour cranks on my hard tail mtb a few years ago which was on a square taper bottom bracket. The drive side crank arm seemed to go on further than the old one meaning all the front shifting was out and couldn't be adjusted to work.

After a lot of adjusting and tinkering and swearing I eventually took it to my lbs. Turns out the new cranks I'd bought weren't quite a match for the bottom bracket length. When I replaced the bottom bracket with the matching cranks all fitted perfectly.

Maybe worth you checking your bottom bracket and cranks match and that they fit the 'chain line' spec of your frame.