Looking for an indestructible crankset
04-17-19, 04:17 PM
#26
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If this ends up failing, the plan was to have a crankset machined from steel rather than billet aluminum. The crankset would quite literally be 5-10 pounds, and a third of the weight of the bike, but it would outlast me for sure. That will be left as a last ditch effort for the future if needed.
04-17-19, 05:03 PM
#27
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Nobody has mentioned improper maintenance?
Square taper cranks over-torqued onto the spindle, or cranks with the wrong taper profile will certainly break at the square hole. Have you ever replaced the bottom bracket?
Breaks at the pedal spindle hole can be caused by cracks by letting your bike fall over.
This being a mountain bike conversion, how is your chainline?
210 is not that heavy. 51x15 is not that big of a gear.
All that aside, freestyle BMX cranks are arguably the toughest cranks you can put on a bike.
Square taper cranks over-torqued onto the spindle, or cranks with the wrong taper profile will certainly break at the square hole. Have you ever replaced the bottom bracket?
Breaks at the pedal spindle hole can be caused by cracks by letting your bike fall over.
This being a mountain bike conversion, how is your chainline?
210 is not that heavy. 51x15 is not that big of a gear.
All that aside, freestyle BMX cranks are arguably the toughest cranks you can put on a bike.
04-17-19, 05:26 PM
#28
aire díthrub
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Nobody has mentioned improper maintenance?
Square taper cranks over-torqued onto the spindle, or cranks with the wrong taper profile will certainly break at the square hole. Have you ever replaced the bottom bracket?
Breaks at the pedal spindle hole can be caused by cracks by letting your bike fall over.
This being a mountain bike conversion, how is your chainline?
210 is not that heavy. 51x15 is not that big of a gear.
All that aside, freestyle BMX cranks are arguably the toughest cranks you can put on a bike.
Square taper cranks over-torqued onto the spindle, or cranks with the wrong taper profile will certainly break at the square hole. Have you ever replaced the bottom bracket?
Breaks at the pedal spindle hole can be caused by cracks by letting your bike fall over.
This being a mountain bike conversion, how is your chainline?
210 is not that heavy. 51x15 is not that big of a gear.
All that aside, freestyle BMX cranks are arguably the toughest cranks you can put on a bike.
I disagree about the bmx cranks though. They’re strong but in the wrong way. Something like the chromoly Odyssey Sunday would have a lot of flex under his riding style and not get the torque to the ground. This follows the OPs line of thinking about having a steel crankset machined. Aluminium is used to deliver torque and power for a reason: stiffness.
this entire topic is about two things:
Riding form
basic materials science
you enjoy riding in a way that you know is destructive, then buy the professional equipment designed to handle serious use, or spend more money later on continuously replacing a lot of inferior equipment. You want to stop throwing away all that money? Change your riding style, fix your form and find enjoyment riding in a way that isn’t purposely destructive. My advice there is to get a track frame to put that ridiculously expensive new crankset on and find a velodrome, or some crit races to participate in.
04-18-19, 02:33 PM
#29
Senior Member
I'm not buying any of this. The OP isn't superman, not even by his own description. His weight and strength are not so exceptional that he should be able to regularly destroy bikes and bike components on a regular basis simply by mashing a tall gear. His riding style is typical of an inexperienced cyclist and not unusual in that regard. Cranks, in particular, including cheap ones, can withstand amazing amounts of abuse for long periods of time. He's either making some kind of mechanical error (e.g. installing incorrectly, forcing mismatched components together, or using BMX race cranks designed specifically for children) or he's exaggerating about how many cranks he's broken.
Last edited by mihlbach; 04-18-19 at 02:40 PM.
04-18-19, 03:18 PM
#31
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Nonetheless, the track cyclists put down a lot of low speed torque to wind up the speed quickly off the line, but spin very fast at the top end.
It would be interesting to see Robert Forstemann's component choices. It sure wouldn't do to have the crankset come flying apart during an Olympic sprint.
Ahhh.... here we go:
https://www.cyclist.co.uk/news/5148/...secret-gearing
52/12 sprockets.
Dura Ace 7700 crankset
Octalink bottom bracket.
04-18-19, 03:25 PM
#32
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As far as the cranks... I wouldn't go cheap.
It looks like the Dura Ace 7700 cranksets (above) are still popular with track cyclists.
They use Octalink V1.
I'd also look at the Sora 3500 series with Octalink V2
One might also look at one of many 24mm and 30mm cranksets. The early FSA carbon cranksets had some issues, but there would be a variety of new generation external bearing bottom brackets & cranksets that could serve the OP well.
And, of course, many of the new frames incorporate an internal bearing for the 30mm cranksets.
It looks like the Dura Ace 7700 cranksets (above) are still popular with track cyclists.
They use Octalink V1.
I'd also look at the Sora 3500 series with Octalink V2
One might also look at one of many 24mm and 30mm cranksets. The early FSA carbon cranksets had some issues, but there would be a variety of new generation external bearing bottom brackets & cranksets that could serve the OP well.
And, of course, many of the new frames incorporate an internal bearing for the 30mm cranksets.
04-18-19, 03:26 PM
#33
Not actually Tmonk
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^
OP, that should work for ya
OP, that should work for ya
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"Your beauty is an aeroplane;
so high, my heart cannot bear the strain." -A.C. Jobim, Triste
"Your beauty is an aeroplane;
so high, my heart cannot bear the strain." -A.C. Jobim, Triste
04-19-19, 08:12 AM
#35
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I guess I did leave out some context, for those doubting. I started all of this at 295 pounds, and slowly fixed that issue over the last four years or so. I have zero doubt that I started with horrible form, and continue to maintain that. As my weight decreased, the frequency of the breakage did as well to be fair. My last crank arm break was in fall of 2018, so it has been a while. At around ~100 miles biked each week, metal fatigue sets in eventually. I always have a nagging thought of when and where it's going to happen again, but the hope is that the track crankset lasts long enough that I at least stop worrying before it breaks. I'm sure it will.
Pedal breakage is another problem, but I've essentially given up trying to fix that one. With a maximum shaft diameter past the standard pedal threading, steel can only do so much. I just keep a spare pair in my bag and change them twice a year as cheap preventative maintenance. Prior to changing pedals regularly, I rode home on one pedal many times.
Pedal breakage is another problem, but I've essentially given up trying to fix that one. With a maximum shaft diameter past the standard pedal threading, steel can only do so much. I just keep a spare pair in my bag and change them twice a year as cheap preventative maintenance. Prior to changing pedals regularly, I rode home on one pedal many times.
04-19-19, 03:33 PM
#36
aire díthrub
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That crankset is so far above everything else you’ve ridden, and you’ll figure that out the first time you ride it. Because it’s literally designed to handle greater stresses, more torque. But you need to work on your form. You can still climb up hills on a heavy gear to enjoy that challenge, without beating your cranks and pedals to death. Cyclists have literally been doing it for over a hundred years. I don’t say this because I don’t want you to piss away another $600 bucks. Because honestly if you have that kind of money to throw away, more power to you. But breaking cranks and pedals is dangerous, and one day you could end up seriously hurt or worse. Enjoy your new crankset. And if you have any technical questions about install or other issues, don’t hesitate to ask. There are plenty of knowledgable people on this sub forum. Cheers.
04-29-19, 07:28 PM
#37
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Get some FGFS/BMX Cranks.
I bet you can find ooodles of used ones online. I always see some kind of FGFS bike for sale when I go on CL.
Here's an example:
https://www.ebay.com/itm/Demolition-Medial-2-0-BMX-Cranks-BLACK-165mm-Flatland-Fixed-Gear-FGFS/301891720514?epid=10021149639&hash=item464a261542:g:87QAAOSwCcZaBL2X
I would bet that if you're willing to go used, you could probably get something together for under $150, which is cheaper than 5 replacement crank arms.
I seriously doubt that you're going to snap BMX cranks by simply pedaling.
Also, the other people said to check your torque. I know that I rounded some crank arms by overtorquing.
Getting the torque right on those things is very important.
I bet you can find ooodles of used ones online. I always see some kind of FGFS bike for sale when I go on CL.
Here's an example:
https://www.ebay.com/itm/Demolition-Medial-2-0-BMX-Cranks-BLACK-165mm-Flatland-Fixed-Gear-FGFS/301891720514?epid=10021149639&hash=item464a261542:g:87QAAOSwCcZaBL2X
I would bet that if you're willing to go used, you could probably get something together for under $150, which is cheaper than 5 replacement crank arms.
I seriously doubt that you're going to snap BMX cranks by simply pedaling.
Also, the other people said to check your torque. I know that I rounded some crank arms by overtorquing.
Getting the torque right on those things is very important.
Last edited by BicycleBicycle; 04-29-19 at 07:35 PM.
