LCP

Electric mountain bikes might be getting lighter, but they're still a bit too heavy for me

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Rebecca Bland's picture

Rebecca Bland

Rebecca has been riding bikes since she was a kid and was particularly taken with mountain biking after a trip to the Forest of Dean with her dad on a sketchy MTB tandem. Since then, she’s dabbled in some road racing, time trialling, but keeps coming back to the muddy dark side – even more so now she has two border collie trail dogs to tire out. 

She began testing and reviewing bikes over five years ago and has written for various cycling publications, including MBR and our sister sites, road.cc and ebiketips. What she lacks in technical ability, she makes up for with an enthusiasm for riding snacks. As off.road.cc’s token northerner, rumour has it she’s never more than a mile away from a Greggs.

3 comments

KiwiMike's picture
4 weeks 1 day ago

Well now we're getting pretty nuanced Smile . Under certain circumstances there can be a slight difference, but for the purposes of 'does a heavier bike descend faster' it's got nothing to to with F = m x a. Bikes aren't even falling, they're rolling on a vector with a lot of other things going on. As mentioned, the effect of suspension activation under impact and deviation from trajectory with subsequent loss of momentum is the real issue.

4 weeks 1 day ago

Agreed, let's not rewrite the laws of physics. At a given density and shape you might well expect a larger object to fall faster since its cross sectional area (governing drag) will grow more slowly that its volume (hence mass, hence force of gravity). 

KiwiMike's picture
1 month 7 hours ago

'Sure, heavy bikes can go faster downhill thanks to good ol' gravity'


er, that's not how physics works, and the discussion thread on the Road.cc article schools the author. What affects how fast a bike goes downhill is air resistance and all sorts of friction, as well as momentum - a heavier bike/rider will be less likely to deviate from a line under impact, and the suspension will activate sooner.

A feather and a cannonball both fall equally fast in a vacuum. This has been a constant since Galileo discovered it. Introduce air, and it's then all down to aerodynamics. For a given density (assuming all eMTB's share the same construction) a heavier thing will also be larger, will have more surface area, and will therefore fall slower
 

I agree eMTB weight is A Thing, and disproportionately affects lighter riders, who also generally have less ability to muscle a heavy bike through technical sections. 
 

So yes, weight is an issue. I'm reminded of just how heavy my eMTB is every time I test ride a customer's acoustic MTB after a service. But let's not try to re-write the laws of physics eh? 😎