what is BB drop

[wapad]

what is BB drop and how does it affect the ride

[Capricorn]

http://www.bikeforest.com/CAD/faq/bb_drop.gif

 

For road bicycles, using conventional sized wheels, BB drop (BB spindle centerline below wheel axle centerlines) has been empirically arrived upon at about [240 mm minus crank length] for useful cornering clearance. Imbalance of pedaling in curves at greater lean causes side-slip. For this reason, higher BB's have shown no advantage in criterium racing while road races are practically unaffected by maximum cornering ability while pedaling.

 

Track bicycles have certain advantages on tracks with steep banking if they can ride the curves at zero speed but then that depends on track length and how it is banked.

sauce

 

Apparently, road bikes have a bigger drop, whereas MTBs have a lower drop for ground clearance purposes. Dont have numbers, so cant vouch for that.

Edited January 29, 2011 by Capricorn

[wapad]

http://www.bikeforest.com/CAD/faq/bb_drop.gif

 

 

sauce

 

Apparently, road bikes have a bigger drop, whereas MTBs have a lower drop for ground clearance purposes. Dont have numbers, so cant vouch for that.

 

 

Ok thanks I learnt something not sure why that was mentioned in a MTB ad though

[Dicky DQ]

Ok thanks I learnt something not sure why that was mentioned in a MTB ad though

 

Indicating obstical and drop-off clearance. Ever tried to ride over big rocks and logs? Chainring gets bashed quire a bit.

[djvr]

A BB drop is very serious You will have to stop, risk loosing your bunch, dodge oncomming traffic in order to pick up your Black Berry

 

In outa here

[Tiny K]

A BB drop is very serious You will have to stop, risk loosing your bunch, dodge oncomming traffic in order to pick up your Black Berry

 

In outa here

 

WAHAHAHAHA! Did you have to go look for where you dropped your BB after not knowing where it disappeared to?

[Johan Bornman]

http://www.bikeforest.com/CAD/faq/bb_drop.gif

 

 

sauce

 

Apparently, road bikes have a bigger drop, whereas MTBs have a lower drop for ground clearance purposes. Dont have numbers, so cant vouch for that.

 

Kirrect. But "lower drop" is slightly confusing though, since some people may think it puts the BB lower to the ground. "Smaller drop" may explain it better.

 

Just to make a note or two in addition to your nice sketch, BB drop per se is a meaninglless number. The same drop on a 29er, 26er and roadbike, will give you different BB clearance. A high BB (in other words, a small drop), makes for poor city riding where you want to put your foot out frequently, when stopping at lights and stop streets. If the drop is too small, you're always standing on tippy toes at the lights.

 

Frame manufacturers talk a lot about BB drop and promise higher clearance, lower centre of gravity, better balance and all sorts of other nonsense. In reality, the manufacturer has very little latitude in placing the BB from the ground, it is always dictated by function and a guestimate of your real application of the bike.