Timeline for How do I fix a left crank that has come off of my Pro Form 4.0 RT Stationary Bike?
Current License: CC BY-SA 4.0
9 events
| when toggle format | what | by | license | comment | |
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| Oct 7, 2020 at 17:27 | comment | added | Argenti Apparatus | @Jodey You just need cranks for square taper JIS or ISO. Vast majority of bikes use JIS and most square taper cranks for sale are JIS. You can estimate tightening torque: a 6kg force on a 0.5m long wrench or socket driver is 30Nm. | |
| Oct 7, 2020 at 16:25 | comment | added | Jodey | Thanks again @Argenti. I have a few quick questions for you and MaplePanda: 1) IF I can determine whether my bike is using an JIS or and ISO standard, can I buy any crank that is of the same standard or must I buy the one that was made specifically for this bike? 2) I am assuming the bolt for the cranks is standard? If do get a replacement crank, and the torque wrench s standard - is there a way to make sure it is on tight enough/ do you think unmechanical guy can do this well enough? I am trying to decide whether to try and repair or if I am better to just buy something else. Thanks again! | |
| Oct 6, 2020 at 23:37 | comment | added | MaplePanda | Does OP need specific cranks? $75USD is way too much for the caliber of part you’re looking for. | |
| Oct 6, 2020 at 21:47 | comment | added | Argenti Apparatus | @Jodey Both the axle and the cranks conform to a square taper standard, either JIS or ISO, A JIS crank will not work properly on an ISO axle, and vice versa | |
| Oct 6, 2020 at 21:24 | vote | accept | Jodey | ||
| Oct 6, 2020 at 21:24 | comment | added | Jodey | Thanks very much for such a thorough answer Argenti. I have looked online and see that a pair of replacement cranks for the RT 4.0 are about $75 US. From what I gather, the taper interfaces have standards (thanks for the link) but the cranks do not? I will try to add a picture of the interface on my bike. I am trying to decide whether this is worth trying to fix or if I should simply buy something new. I would appreciate your thoughts and will try to add in a few photos of the share taper interface. | |
| Oct 6, 2020 at 19:55 | comment | added | Argenti Apparatus | @WeiwenNg There's something about the axle that maybe looks like damage on the upper left hand surface - it might just be a mark though. I just noticed the bolt-hole is off-center which might be a contributing factor to the crank coming loose | |
| Oct 6, 2020 at 19:12 | comment | added | Weiwen Ng | So, the axle in question is almost certainly made of steel, and the cranks are most likely aluminum. Steel is much harder than aluminum, so it seems to me that it's pretty likely that the axle is undamaged. In principle, another possibility for the axle is titanium, but that's exceedingly unlikely (those would be a weight weenie sort of item, probably not installed on stationary bikes), and anyway ti is still harder than aluminum. | |
| Oct 6, 2020 at 19:02 | history | answered | Argenti Apparatus | CC BY-SA 4.0 |