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Really? After a road bike has already slowed to the MTB speed, it still has as much kinetic energy as the MTB, along with it's lower rolling resistance and less drag. Once the speeds are equalised, the road bike's brakes still have more to do than the MTB's
In other words, if you rode an MTB down a typical Alpine road descent, its brakes would have an easier time than a road bike's on the same descent.
We are not comparing the bikes on the same route. We are comparing the bikes on their respective territory. We'll assume the elevation difference is the same so potential energy is equal. (rider+bike weight is close)
A MTB going down the A-line at Whistler (considered a fast track right?) will average 30 kph if the rider is pro. A roady going down Tourmalet will average 60 kph if he is pro. Difference is, the roady will probably have to avg well beyond 200W to do that. Something the MTB don't because of the technical riding.
The roady however will go 80-100 kph for almost a third of the time. MTB probably wont exceed 60 much of the time. So air resistance become much much greater on the roady since air resistance is exponential in third (assuming no wind). A MTB is far less aero though, but not enough to stir things up.
Rolling resistance is probably 3-4 times greater on the MTB so I don't think it'll exceed 100W on a typical run.
All in all I can't quite work our where the power of the road rider puts the equation. Might be closer that you think.
Another difference will be the periodic heavy braking the road bike has to endure. For a disc system that would mean large temperature fluctuations compared to MTB. Can't be an advantage.
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They're the new SRAM XX1 designed as a 1x11 mainly aimed at 29ers.
10-42t rear cassette give you a good amount of range without needing a double or triple;
Ah my MTB friend was telling me about it, gives the full range with only one chainring? Nice, but pricey so I hear
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Nice, but pricey so I hear
Pricey at the XX level, but if you don't need the full 10-42 (420%) range, you can use 1×10 at the X7 level and save quite a bit (money and weight) compared with 2×10 and still have 11-36 (327%). Who, among people who pay for their own kit, really needs more range than that?
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Pricey at the XX level, but if you don't need the full 10-42 (420%) range, you can use 1×10 at the X7 level and save quite a bit (money and weight) compared with 2×10 and still have 11-36 (327%). Who, among people who pay for their own kit, really needs more range than that?
Sounds like very good kit, if I ever get round to getting my geared MTB back on the road I'll look at that. I take it back about the bike: I like, although the Brooks can go
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Really? After a road bike has already slowed to the MTB speed, it still has as much kinetic energy as the MTB, along with it's lower rolling resistance and less drag. Once the speeds are equalised, the road bike's brakes still have more to do than the MTB's
In other words, if you rode an MTB down a typical Alpine road descent, its brakes would have an easier time than a road bike's on the same descent.
Dammit asked about energy turned into heat, and i gave a slightly trolling answer. The key bits were assuming negligible pedalling, and 'on average'. The average is taken over the whole descent, including the bits where the riders aren't braking...
In more detail:
mass - the MTB is heavier, but both bikes are light compared to their rider, so the difference in total mass is small.
energy - i'm assuming no pedalling, just looking at the gravitational potential energy, so with a bit more mass the MTB has a bit more energy to get rid of, but it's close.
Rolling resistance - the sum of all the non-braking constant forces that resist motion. The MTB has more, but the work done against it is resistance force x distance travelled against it. With the road bike's much longer path length of descent, it's not clear which will loose more energy this way.
Drag force - air resistance and any other forces that go roughly with the square of speed. To calculate the work done against it you can integrate it over the path length of the descent. It will be much larger for the road bike because even though it's more aero, it goes much faster and further.Brake heat energy - what's left of the starting potential energy after the above have been accounted for. It's clear the MTB will have more.
You're answering a more relevant but slightly different question about how hard the brakes have to work.
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We are not comparing the bikes on the same route. We are comparing the bikes on their respective territory. We'll assume the elevation difference is the same so potential energy is equal. (rider+bike weight is close)
A MTB going down the A-line at Whistler (considered a fast track right?) will average 30 kph if the rider is pro. A roady going down Tourmalet will average 60 kph if he is pro. Difference is, the roady will probably have to avg well beyond 200W to do that. Something the MTB don't because of the technical riding.
The roady however will go 80-100 kph for almost a third of the time. MTB probably wont exceed 60 much of the time. So air resistance become much much greater on the roady since air resistance is exponential in third (assuming no wind). A MTB is far less aero though, but not enough to stir things up.
Rolling resistance is probably 3-4 times greater on the MTB so I don't think it'll exceed 100W on a typical run.
All in all I can't quite work our where the power of the road rider puts the equation. Might be closer that you think.
Another difference will be the periodic heavy braking the road bike has to endure. For a disc system that would mean large temperature fluctuations compared to MTB. Can't be an advantage.
I believe you are thinking this the wrong way. Just to put an example, Runner X runs at 30km/h for 500 meters, then rests for 5 minutes, then runs again at 30km/h for 500 meters. Now compare with Runner Y, he runs 1000 meters at a constant speed, taking the same time than the Runner X. Who would be more tired?
Same thing goes for brakes. Intensity matters, is not just an energy exchange, specially if you are working near the limit. -
Viscacha by revelate.
The newer design is a lots better and addressed some of the fault I've found with it.
Almost exactly what I want for long days on the bike this summer, but just tried to find cost and it came to $170 for one (bit too pricey for me at mo), any other similarly designed and sized (and cheaper) saddle bags you guys know of?
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Almost exactly what I want for long days on the bike this summer, but just tried to find cost and it came to $170 for one (bit too pricey for me at mo), any other similarly designed and sized (and cheaper) you guys know of?
Right now I use a Carradice SQR tour. I got it for the dun run and brighton trips etc. It's good because its hard as nails, and has a decent quick release. However I'm looking for something a little smaller for shorter trips, so am considering the ortleib classic range.
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fuuuuuuuuuuu
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bikepack.pl is cheaper I think.
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Another millionaire wall hanging..... No pedals = not a bike! -
Should've left it in front of the tie-die, rode it today, might thaw out by next Wednesday......
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Bike porn
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@Velocio
Rick Hunter full fat longbike with custom porcelain rocket bags! The frame looks stunning!