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Thread: e-Bikes - Let's talk

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    Quote Originally Posted by SolarBikeCar View Post
    One point rarely discussed is the stopping distance. E-bikes are heavier but generally have front and rear disk brakes. On the downhill they go about the same speed as a traditional commuter bike. In a panic stop I would expect disk brakes to greatly outperform a single coaster brake or a pair of v-brakes. Should we ban bikes without disk brakes on trails because riders can go faster than 30 downhill but can't stop adequately? Ebikes are used to improve uphill speed where stopping quickly isn't hard even without disk brakes.
    I really should not feed the troll... But SCIENCE.

    You do realize that most traditional commuter bikes range between 20 and 30 pounds, correct? And most e-assist bikes are going to weigh at LEAST double the lower range of a non-e-assist bike. Obviously, it is going to be harder to stop a heavier object when it is in motion (did you not learn this in your elementary school science classes?). Therefore, your argument is moot. The stopping distance of a 20 pound bike with sub-par mechanical rim brakes is still probably going to be shorter than the stopping distance of a 50 pound e-assist bike with 160mm hydraulic disc brakes (assuming the load is the same). (Now I kind of want to do an experiment, but none of my bikes have rim brakes.)

    This is why larger, heavier vehicles have bigger and stronger brakes than smaller, lighter vehicles.

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    Science is not SolarBikeCar's strong suit, despite being a self-proclaimed "engineer" - I guess IT doesn't require grade-school physics :-)

    Or, apparently, experience with bicycle braking systems. The main argument for disc brakes is not stopping distance, but consistent power in wet conditions and better modulation. Pro rim-brake arguments (why?!) often miss this point and start by asserting that even crappy brakes on a bicycle are usually capable of/sufficient for breaking wheel traction. I used to love that feature on my coaster-brake BMX ... Sure, disc brakes stop harder with less muscle input, but I'd be surprised to learn that in any sort of typical brake-hard emergency stopping situation disc brakes made for shorter stopping distances. Maybe vs rim brakes (not coaster) in the wet ... Someone could do a study ... (ugh, science again!).

    (I do think that disc brakes give more control, but I think most people -- certainly myself included -- are not going to be feathering brakes in an emergency stopping situation.)
    Last edited by hozn; 08-17-2017 at 07:58 AM.

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    Quote Originally Posted by hozn View Post
    Or, apparently, experience with bicycle braking systems. The main argument for disc brakes is not stopping distance, but consistent power in wet conditions and better modulation. Pro rim-brake arguments (why?!) often miss this point and start by asserting that even crappy brakes on a bicycle are usually capable of/sufficient for breaking wheel traction. I used to love that feature on my coaster-brake BMX ... Sure, disc brakes stop harder with less muscle input, but I'd be surprised to learn that in any sort of typical brake-hard emergency stopping situation disc brakes made for shorter stopping distances. Maybe vs rim brakes (not coaster) in the wet ... Someone could do a study ... (ugh, science again!).
    It's not completely scientific despite it calling itself science, but GCN did a comparison. It's a fun and useful comparison, despite the fact that they haven't controlled for any variables etc.

    https://www.youtube.com/watch?v=t0hKMgUEku4

    Oops, this is the better video for stopping distance.

    https://www.youtube.com/watch?v=uHFSSXOSnxs
    Last edited by huskerdont; 08-17-2017 at 08:44 AM.

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    Quote Originally Posted by SolarBikeCar View Post
    Ebikes are used to improve uphill speed where stopping quickly isn't hard even without disk brakes.
    Based on e-bikers I've seen on the MVT and in DC, they are also used to pass people on a flat, crowded trail doing 20+ mph plus, and also to dangerously cut off cyclists starting up from a red light.

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    Quote Originally Posted by gibby View Post
    Based on e-bikers I've seen on the MVT and in DC, they are also used to pass people on a flat, crowded trail doing 20+ mph plus, and also to dangerously cut off cyclists starting up from a red light.
    I see plenty of "roadies" doing the same.

    Regulate the behavior, not the tool

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    Quote Originally Posted by hozn View Post
    Science is not SolarBikeCar's strong suit, despite being a self-proclaimed "engineer" - I guess IT doesn't require grade-school physics :-)

    Or, apparently, experience with bicycle braking systems. The main argument for disc brakes is not stopping distance, but consistent power in wet conditions and better modulation. Pro rim-brake arguments (why?!) often miss this point and start by asserting that even crappy brakes on a bicycle are usually capable of/sufficient for breaking wheel traction. I used to love that feature on my coaster-brake BMX ... Sure, disc brakes stop harder with less muscle input, but I'd be surprised to learn that in any sort of typical brake-hard emergency stopping situation disc brakes made for shorter stopping distances. Maybe vs rim brakes (not coaster) in the wet ... Someone could do a study ... (ugh, science again!).

    (I do think that disc brakes give more control, but I think most people -- certainly myself included -- are not going to be feathering brakes in an emergency stopping situation.)
    http://www.killasgarage.bike/uncateg...an-rim-brakes/ is another interesting look at it from a science-y approach.

    As noted in that article, I think part of the benefit of disc brakes also is the "greater stopping power for the input provided at the lever" - but that doesn't mean that there's actually greater stopping power, period. That's more of a function of the travel from pad to braking surface than anything else (or, hydraulics!). Besides - a disc brake has to be more powerful because it's trying to stop a faster moving object (the rim is farther away from the wheel center).

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    Quote Originally Posted by Sunyata View Post
    I really should not feed the troll... But SCIENCE.

    You do realize that most traditional commuter bikes range between 20 and 30 pounds, correct? And most e-assist bikes are going to weigh at LEAST double the lower range of a non-e-assist bike.
    Trek Conduit (418 W ebike ) 44 lbs
    https://www.trekbikes.com/us/en_US/e.../1329000-2017/

    Trek Lync 5 (urban commuter) 30 lbs
    https://www.trekbikes.com/us/en_US/b...olorCode=black


    both these bikes have a total weight limit of 300 lbs. are we going to get in to the discussion of rider weight, which is far more variable?

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    Quote Originally Posted by americancyclo View Post
    are we going to get in to the discussion of rider weight, which is far more variable?
    Not sure about your weight, but my weight isnt really variable at all. It is quite persistently at X.

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    Quote Originally Posted by rcannon100 View Post
    Not sure about your weight, but my weight isnt really variable at all. It is quite persistently at X.
    But, person to person, the weight varies a lot.

    For example, if I buy a 15 lb road bike, I will be pushing 275 lbs up the hill. On the other hand, a 30 lb bike will have me pushing 290, which is a 7% difference.

    On the other hand, someone who weighs 135 will have total weights of 150 and 165, or a 10% difference.

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    Quote Originally Posted by dhs1963 View Post
    But, person to person, the weight varies a lot.

    For example, if I buy a 15 lb road bike, I will be pushing 275 lbs up the hill. On the other hand, a 30 lb bike will have me pushing 290, which is a 7% difference.

    On the other hand, someone who weighs 135 will have total weights of 150 and 165, or a 10% difference.
    It's also dependent on what else you may have to carry around with the bike. If I have my daughter and her trailercycle attached (which these days I do more often than not), that's an extra 80+ lbs. I'm towing up the hill on the MBT to get home (since she rarely pedals and her drivetrain is probably half shot anyway), and when I almost wish I had a motor.

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