I don't know much about bikes. I've got myself an older Specialized Stumpjumper. I asked myself the other day while I was riding with +50km/h through the forest what the maximum speed is the wheel bearings will endure and if there is e difference between smooth roads and trails.

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    You were going significantly faster than a Tour de France-level pro rider averages on a racing road bicycle? But you were in a forest? On an old mountain bike? Ooooh-kay. Commented Sep 1, 2020 at 9:26
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    @AndrewHenle 50km/h is perfectly possible downhill on a fire road. The limit is nerves or maybe spinning out. The OP didn't claim to be doing it on the flat
    – Chris H
    Commented Sep 1, 2020 at 9:56
  • Related: bicycles.stackexchange.com/questions/68324/…
    – Swifty
    Commented Sep 1, 2020 at 10:11
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    @AndrewHenle I was doing 50 km/h on a forest gravel downhill yesterday, what is so unbelievable about that? Commented Sep 1, 2020 at 10:20
  • @AndrewHenle Downhill on a fire road ^^
    – Lotok
    Commented Sep 1, 2020 at 10:33

1 Answer 1


50km/h = 13.9m/s = 833m/min. Wheel circumference is roughly 2m so that the wheel is spinning at 417rpm. Sealed industrial bearings easily withstand 10.000rpm and more. The steel ball bearings inside even more.

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    Thank you. So I will never reach the limit.
    – Lotok
    Commented Sep 1, 2020 at 10:30
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    Not unless you travel at over 1,000km/h based on the above maths. Commented Sep 1, 2020 at 10:52
  • Your calculations look off, just roughly guessing to get near 833m/min you’d need to be doing close to 60mph. Did you forget the conversion between mph and kmh ?
    – Dan K
    Commented Sep 1, 2020 at 11:30
  • Just for clarity I worked out the circumference of an average 700c / 29” tire to be 0.91m. Calculating 831.31m per minute / circumference = 912rpm
    – Dan K
    Commented Sep 1, 2020 at 12:44
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    @dan k - I follow your reasoning until you divided by 100 to convert inches to meters. What’s the logic there? Should multiply by 2.54 to get to cm before you divide by 109. Also, to get a more precise diameter (and already in cm) add 2x the tire size to 622 for a 29er or 700 wheel
    – Andrew
    Commented Sep 1, 2020 at 23:24

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