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-   -   School me on bottom bracket drop please... (https://www.bikeforums.net/general-cycling-discussion/1153775-school-me-bottom-bracket-drop-please.html)

Wattsup 08-26-18 09:15 PM

School me on bottom bracket drop please...
 
The 2017 Giant Anyroad I own has a bottom bracket drop of only 61mm, which seems strange to me for the intended purpose and consumer target group, at least as I see it.

Can someone explain to me why having such a high bottom bracket in this type of bike makes sense?

See: https://www.giant-bicycles.com/us/anyroad-comax-2017

Hiro11 08-26-18 09:52 PM

BB drop alone doesn't tell you much about how a bike will handle. One thing is certain, a smaller BB drop gives you greater clearance at the chainrings, that's likely the reason for your bike having a low BB drop. A higher BB also typically stiffens up a frame and makes the steering a bit faster. Some builders say a larger BB drop also lowers your center of gravity and makes the bike "more stable", others disagree. I have a bike with a fairly extreme 80mm drop and that bike feels extremely planted if a bit plodding, however that's likely the result of many factors.

/edit, reading through this it didn't make sense. I fixed the grammar.

Kedosto 08-26-18 10:03 PM


Originally Posted by Wattsup (Post 20529538)

Can someone explain to me why having such a high bottom bracket in this type of bike makes sense?

Clearance between the chainrings and the ground, or objects on the ground like rocks, stumps, etc. Also helps reduce pedal strikes, especially with longer crank arms.

The “Any Road” includes gravel or no road, so a small bottom bracket drop (higher off the ground) might not be a bad idea.


-Kedosto

fietsbob 08-26-18 10:20 PM

Data; its the distance below the line between the hub axises

In a small wheel bikes its not even a drop,

then you go with BB height above the ground...



Cyclocross bikes have higher bb so you can pedal thru off camber slopes,
and not dig a pedal into the up hill.

maybe they adopted that , while going for a sloping top tube feature .
a CX frame would not use..





...

Wattsup 08-27-18 09:17 AM


Originally Posted by Hiro11 (Post 20529587)
BB drop alone doesn't tell you much about how a bike will handle. One thing is certain, a smaller BB drop gives you greater clearance at the chainrings, that's likely the reason for your bike having a low BB drop. A higher BB also typically stiffens up a frame and makes the steering a bit faster. Some builders say a higher BB also lowers your center of gravity and makes the bike "more stable", others disagree. I have a bike with a fairly extreme 80mm drop and that bike feels extremely planted if a bit plodding, however that's likely the result of many factors.

Thanks for the info. What I find strange is just how low it is...aside from mountain bikes, it's difficult to find another "all-road" or gravel bike with a BB drop so small. The bike comes with 32mm tires, so I don't think the designers had roots and big rocks in mind when they designed the bike. Maybe as you say it has to do with stiffening the frame. It seems that the frame is a "composite blend", Giant's way of saying they skimped a bit on the carbon fiber and put some glass fiber in its place. That's one way to increase the profit margins, huh?

ThermionicScott 08-27-18 09:39 AM


Originally Posted by Wattsup (Post 20529538)
The 2017 Giant Anyroad I own has a bottom bracket drop of only 61mm, which seems strange to me for the intended purpose and consumer target group, at least as I see it.

Can someone explain to me why having such a high bottom bracket in this type of bike makes sense?

See: https://www.giant-bicycles.com/us/anyroad-comax-2017

Would it be a problem if you hadn't read the spec? ;)

Given that they use 170mm cranks on the smallest model, perhaps they just used a slightly higher BB across the board to make things easy on themselves. 61mm is only 5-7mm or so higher than a lot of production bikes that don't raise eyebrows, and you're unlikely to notice that difference.

Wattsup 08-27-18 09:53 PM


Originally Posted by ThermionicScott (Post 20530332)
Would it be a problem if you hadn't read the spec? ;)

.

The bike spit me off onto my head a few weeks ago, as documented on this forum. I'm still looking for answers. :foo: Aside from mountain bikes, I haven't seen any bike with a BB drop less than 65mm. Only the one that bucked me off onto my head...61mm.


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