# BB Drop?



## LeeWald (Dec 20, 2006)

So, here's a question for all of you guys who are more tech savy than I am. I'm looking at a new bike for this season. One has a bottom bracket drop of 7 cm. and the other one 5.8 cm. I know that the current trend is towards lower bb heights. Does 1 cm. really make that much difference or am I just splitting hairs here.


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## laffeaux (Dec 12, 2001)

LeeWald said:


> So, here's a question for all of you guys who are more tech savy than I am. I'm looking at a new bike for this season. One has a bottom bracket drop of 7 cm. and the other one 5.8 cm. I know that the current trend is towards lower bb heights. Does 1 cm. really make that much difference or am I just splitting hairs here.


You should be able to notice a 1cm change in BB height. IMO, that's a big change. However, which is better is entirely up to you, and how the BB height works with the other frame geometry changes. If you can test ride both bikes, try them out.


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## Gripped (Nov 27, 2002)

LeeWald said:


> So, here's a question for all of you guys who are more tech savy than I am. I'm looking at a new bike for this season. One has a bottom bracket drop of 7 cm. and the other one 5.8 cm. I know that the current trend is towards lower bb heights. Does 1 cm. really make that much difference or am I just splitting hairs here.


70 is about right. I think 68-70 is a sweet spot in modern cross. 58 is way too high. Anything lower than 72 is too low (and 72 is pushing it).


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## LeeWald (Dec 20, 2006)

Thanks for the replies guys. What you're telling me is exactly what I was thinking and you have corroborated it for me.


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## mike6108 (Jun 12, 2004)

Gripped said:


> 58 is way too high.


Way too high for what?

2010 Ridley X-Night: 57mm BB drop on a 56cm frame
2010 Ridley X-Fire: 61mm BB drop on a 56cm frame


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## singlering (Feb 19, 2006)

mike6108 said:


> Way too high for what?
> 
> 2010 Ridley X-Night: 57cm BB drop on a 56cm frame
> 2010 Ridley X-Fire: 61cm BB drop on a 56cm frame


So they drop the BB more than the frames height?


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## crankles (Sep 25, 2007)

I went from a 58 drop to a 70 drop. Big difference in cornering. At one point, the bike with the 58 drop was my pit bike. I switched mid race after a flat. Same Tires on both, yet I was off in the tape a couple of times trying to take the same lines at the same speed as on the 70mm drop bike. 

not scientific, but I'm a thoeretician, not an empiricist ;-)


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## masongsp (Apr 30, 2003)

crankles said:


> I went from a 58 drop to a 70 drop. Big difference in cornering. At one point, the bike with the 58 drop was my pit bike. I switched mid race after a flat. Same Tires on both, yet I was off in the tape a couple of times trying to take the same lines at the same speed as on the 70mm drop bike.
> 
> not scientific, but I'm a thoeretician, not an empiricist ;-)



I've been thinking of selling my Ridley Supercross next season and getting into something with a lower BB for just this reason. I rode the Ridley for 3 years as my road bike - just couldn't get comfortable taking corners at speed at all, but thought it was just me. Finally got a "real" road bike this spring and can't believe the difference. Same thing on my mtb - got a new one last year with the BB 2-3cm lower and it made an amazing difference (but certainly not the only change there). The problem now is I feel it riding cross and just don't seem to have the confidence in the corners. I've been lowering my saddle trying to compensate for my center of mass and it's helping, but seems like if the BB was a little lower, I'd be able to rail a little harder. 

And please don't tell me I'm wrong - you'll ruin my bike shopping fun for next year!


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## jroden (Jun 15, 2004)

I got a lower bb on my bike, I think it handles better. I seem to scrape my heels on the ground from time to time in tight spots but it hasn't been a problem.

How of that measured, by the way?


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## bikenerd (Jan 22, 2004)

My bike (custom Rock Lobster) has 72mm of drop, and it corners awesome. I've done one race where there was a sidehill section with roots and I whacked a pedal, but just in that one spot on that one course. Every once in a while I hit a pedal when I'm using it as a mountain bike, but for a race bike I wouldn't change it. Paul @ Rock Lobster knows his cross.


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## mike6108 (Jun 12, 2004)

singlering said:


> So they drop the BB more than the frames height?


Oops - meant to write mm for the BB drop, not cm!! :mad2: Original post has been edited.


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## yo mamma (Aug 10, 2009)

Setting aside any concerns you may have about the weight, try a test ride on a Poprad/Presidio (same bike) if you can borrow one for a bit, and do a comparison ride w/ a Ridley or Colnago or some other frame w/ a roughly 6cm bb drop and you'll see instantly what a difference it makes.


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## jroden (Jun 15, 2004)

I slapped a tape on my bikes and was surprised to find my main bike , a steel hot tubes was about 60, while my pit bike a no-name affair is about 72. I have always liked how the no-name bike handled better but did notice myself hitting the pedals on the ground a lot. I may try racing the no-namer and see if I go better around the corners, I'm thinking there may be soething to be said for the 70 mm drop, although the world cup guys certainly seem to zip around on their ridleys pretty well.


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## Coolhand (Jul 28, 2002)

I prefer the low BB bikes for racing, they handling the switchback and off camber stuff better for me.


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## krisdrum (Oct 29, 2007)

All this talk of bb drop piqued my curiousity. My road bike (custom, I have the blueprint) has a drop of 70mm. My cross bike says it has a BB HEIGHT of 28.5 (not sure how to convert that over). Is 70 a tall BB drop for a road bike?


Thanks to another thread, I can ballpark my Scattante's bb drop, using BB height. So, assuming it has 700x35 tires on it (a bit of an assumption), the wheel radius would be 345.04. Subtract the 285 from it gives me 60.04. So approximately a 1cm bb drop difference between my road and cross rides. The cross bike definitely feels taller to ride and does not corner as well. The cross bike can feel very skittish in turns, especially tight 180s.


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## jmoote (Nov 29, 2007)

jroden said:


> I slapped a tape on my bikes and was surprised to find my main bike , a steel hot tubes was about 60, while my pit bike a no-name affair is about 72. I have always liked how the no-name bike handled better but did notice myself hitting the pedals on the ground a lot. I may try racing the no-namer and see if I go better around the corners, I'm thinking there may be soething to be said for the 70 mm drop, although the world cup guys certainly seem to zip around on their ridleys pretty well.


Interesting to find that you've always felt the bike with more drop handled better, even without knowing the geometry. My bike has a drop of 70 mm and I run 175 mm cranks. The really off camber stuff is hard to pedal through and I have to be conscious about pedalling through fast turns that I'm leaning a lot. The payoff is much more stability on relatively off camber stuff* and cornering more like a crit bike. I suspect the pros do well on the Ridleys _in spite of_, not due to the geometry of those bikes. They make sense for some terrian, but not the majority of what I see on cross courses these days.

*John, for you and others who race around here: I found this especially great for the very fast back and forth off camber before the big hill at Guelph last weekend - pretty much no need to brake as I went across there.


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## gregdogg62 (Aug 9, 2004)

krisdrum said:


> All this talk of bb drop piqued my curiousity. My road bike (custom, I have the blueprint) has a drop of 70mm. My cross bike says it has a BB HEIGHT of 28.5 (not sure how to convert that over). Is 70 a tall BB drop for a road bike?
> 
> 
> Thanks to another thread, I can ballpark my Scattante's bb drop, using BB height. So, assuming it has 700x35 tires on it (a bit of an assumption), the wheel radius would be 345.04. Subtract the 285 from it gives me 60.04. So approximately a 1cm bb drop difference between my road and cross rides. The cross bike definitely feels taller to ride and does not corner as well. The cross bike can feel very skittish in turns, especially tight 180s.


To figure out BB drop, measure the height from the middle of the bottom bracket and the height to the center of the rear wheel axle. Subtract the BB height from the axle height to get the BB drop. 70 is in the normal range for a road bike. My Strong Road bike was built with a BB drop of 75. My rock lobster cross bike was built with a BB drop of 70. 

I really like the lower BB. My previous bike had a BB drop of 57, and it was really tough to maneuver through tight switchbacks and corners. With my Rock Lobster I have clipped a pedal a couple of times, but it is well worth it to have the better handling through the tight turns.


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## jroden (Jun 15, 2004)

jmoote said:


> *John, for you and others who race around here: I found this especially great for the very fast back and forth off camber before the big hill at Guelph last weekend - pretty much no need to brake as I went across there.


What kind of bike is it, by the way? I let my tires (tyres in Canadian) down to about 20 psi before the race by mistake and had to nip into the pit and pump them up. I don't know how people can ride such soft tires, I had about zero control. 

I wonder what production bikes come with a lower BB? I always felt that the best handling bike I owned was the older specialized in red and white, but perhaps I was just in better shape.

I need to resist the urge to make up for getting older by buying new equipment.


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## crankles (Sep 25, 2007)

*bb drop list*

Here's a list someone compiled last year. It's in sorted order based on bb drop.


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## jmoote (Nov 29, 2007)

jroden said:


> What kind of bike is it, by the way?


It's a True North custom Ti/Carbon frame. The 70 mm BB drop was my idea, on the lower end of what Hugh thought was reasonable for a cross bike.



> tires (tyres in Canadian)


That's one where we go with the US convention, not UK English. I like both spellings personally.



> I need to resist the urge to make up for getting older by buying new equipment.


Don't resist - it's a great excuse to buy new gear


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## jroden (Jun 15, 2004)

crankles said:


> Here's a list someone compiled last year. It's in sorted order based on bb drop.


where?


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## pharding (Sep 30, 2009)

As a comparison the bottom bracket drop on a Cerverlo road bike is 68 mm. the Ridley X-Night is 57 mm. The Ridley X-Fire is 61 mm.


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## crankles (Sep 25, 2007)

*Opps...here's the file*

Oops. my bad. I attatched an excel spreadsheet file, which isnt' supported.It's now a tab deliminated text file. Just import into your fav spreadsheet program. e


jroden said:


> where?


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## jroden (Jun 15, 2004)

thanks, that's really interesting to look at. It seems like a lot of companies don't publish that number in the specs. It's really interesting to see that there is nearly an inch difference in what makers feel is the proper bottom bracket height. I'd have to assume that in time it will gravitate to the "right" height like road bikes.

My gut feeling is that 70 might not be a bad bet.


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## Gripped (Nov 27, 2002)

jroden said:


> I wonder what production bikes come with a lower BB? I always felt that the best handling bike I owned was the older specialized in red and white, but perhaps I was just in better shape.


The Trek XO reportedly has 71 (see other thread). That's based on a calculation of theoretical tire diameter and the bb height (what a worthless metric). I'd reckon it's really between 70 and 72. I think that's a good drop. The price for spec is a little on the high side. Still I wouldn't mind picking up a couple of the XO2s after the season when they go on sale.

The Poprad has a pretty low BB but the replacement Presidio is a pretty standard 64-60 depending on size.

The Waterford X-14 has a drop of 70. I think you could build up one of those with a spec like the Trek for about the same price. Here's a link to one built with 105 ...

http://rivercitybicycles.com/product/waterford-x-14-735.htm


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## jroden (Jun 15, 2004)

Gripped said:


> The Trek XO reportedly has 71 (see other thread). That's based on a calculation of theoretical tire diameter and the bb height (what a worthless metric). I'd reckon it's really between 70 and 72. I think that's a good drop. The price for spec is a little on the high side. Still I wouldn't mind picking up a couple of the XO2s after the season when they go on sale.
> 
> The Poprad has a pretty low BB but the replacement Presidio is a pretty standard 64-60 depending on size.
> 
> ...


Thanks, we have a nice Trek dealer in town. I like the looks of the new Giant also, I think it's got a higher BB though.


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## Gripped (Nov 27, 2002)

jroden said:


> Thanks, we have a nice Trek dealer in town. I like the looks of the new Giant also, I think it's got a higher BB though.


The problem with the Trek for me is the effective TT. The 54 has a ETT of 53.9 and the 56 is 55.8. The wheelbase, chainstays and head tube angle all add up to the more predicable side of quick handling. With a longer stem in the 54, that slows the handling even more. But a ETT of almost 56 is a bit on the long side for me.

For me, the Waterford would be about golden.


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## jroden (Jun 15, 2004)

my road tt is 58.5, while the trek is 57.8. What do you think of that? The next size up is way too big.

An ps--is the two frames the same x01 and x02 w/ just different components?


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## jmoote (Nov 29, 2007)

jroden said:


> my road tt is 58.5, while the trek is 57.8. What do you think of that? The next size up is way too big.


I'd say the 7mm shorter TT will be fine. Depending on headtube length, stem size, spacer arrangement you can probably have it all wash out without going to a drastically different stem. My road and cross bikes have the same 210 mm headtubes, 20 mm of spacers and -8° stems. Road top tube is 575 with a 100 mm stem and cross is 570 with a 90 mm stem. I've debated going to a 100mm stem on the cross bike and dropping 10 mm of spacers, but other than that I like the higher/closer bars on the cross bike.



> An ps--is the two frames the same x01 and x02 w/ just different components?


Same frame, different paint and components.


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## jroden (Jun 15, 2004)

jmoote said:


> I'd say the 7mm shorter TT will be fine. Depending on headtube length, stem size, spacer arrangement you can probably have it all wash out without going to a drastically different stem. My road and cross bikes have the same 210 mm headtubes, 20 mm of spacers and -8° stems. Road top tube is 575 with a 100 mm stem and cross is 570 with a 90 mm stem. I've debated going to a 100mm stem on the cross bike and dropping 10 mm of spacers, but other than that I like the higher/closer bars on the cross bike.
> 
> Same frame, different paint and components.


That might be a good option, our local shop, Handlebars is really good about mix and match with new bikes.


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## pharding (Sep 30, 2009)

Stevens and S-Works Tri-Cross have bottom bracket drops comparable to road bikes. Parlee will make a custom cross bike with that geometry.

By the way this thread influenced my decsion to order a Ridley X-Fire today and cancel my order for the Ridley X-Night.


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## yo mamma (Aug 10, 2009)

crankles said:


> Oops. my bad. I attatched an excel spreadsheet file, which isnt' supported.It's now a tab deliminated text file. Just import into your fav spreadsheet program. e


I'm assuming you didn't measure all these bikes, but rather took the mfr's specs, which makes the BB height column practically worthless as it is dependent on the tires on the bike at the time of the measurement. BB Drop is imminently more useful since it is independent of tire size.


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## jroden (Jun 15, 2004)

an eye opener for sure. I assumed my custom hot tubes had a lower bottom bracket but upon measuring the drop carefully tonight it was 57.5 I'm going to race sunday on my cheap-o pit bike with a 70 drop and see if I get around the corners better,

It would help if the mgfr's provided that figure, it seems important. Maybe I just suck and am looking for excuses for my lousy bike handling, who knows.


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## Gripped (Nov 27, 2002)

yo mamma said:


> I'm assuming you didn't measure all these bikes, but rather took the mfr's specs, which makes the BB height column practically worthless as it is dependent on the tires on the bike at the time of the measurement. BB Drop is imminently more useful since it is independent of tire size.


Duh.

You can usually do a calculation based on bb height and come out okay. I've got that Excel file on my computer but I'm lazy and don't feel like finding it.


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## velociped jones (Mar 21, 2005)

as long as i got simon burney out, he sez the "measurement from a level floor to the center of the bottom bracket shell should be around 280mm."


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## jroden (Jun 15, 2004)

velociped jones said:


> as long as i got simon burney out, he sez the "measurement from a level floor to the center of the bottom bracket shell should be around 280mm."



Bike with 57.5 bb drop = 286mm height from floor
Bike with 70 bb drop = 280mm " " "

Interesting...


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## yo mamma (Aug 10, 2009)

Gripped said:


> Duh.
> 
> You can usually do a calculation based on bb height and come out okay. I've got that Excel file on my computer but I'm lazy and don't feel like finding it.


Guess you haven't seen JRoden's post:



jroden said:


> Bike with 57.5 bb drop = 286mm height from floor
> Bike with 70 bb drop = 280mm " " "
> 
> Interesting...


I don't what two bikes he's referring to, but you see those sorts of discrepancies all the time when using bb height to compare frames. No matter how you slice it, bb drop is more accurate and more appropriate for comparing apples to apples as it is independent of the tires.


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## jroden (Jun 15, 2004)

yo mamma said:


> Guess you haven't seen JRoden's post:
> 
> 
> 
> I don't what two bikes he's referring to, but you see those sorts of discrepancies all the time when using bb height to compare frames. No matter how you slice it, bb drop is more accurate and more appropriate for comparing apples to apples as it is independent of the tires.


One bike is this cheapo-o no name frame that was sold online for a while on bike island. It seems to fit me perfectly, I bought it as a pit bike but I'm going to try racing w/ the lower bb and see if it handles better

The other one is a custom hot tubes. I asked for a lower BB and never bothered to measure. I guess the BB is "low" but the drop is about like a Ridley, so what does that mean?

I compared the two with whatever tires they happened to have on.

Damn fancy expensive steel bike was supposed to be the last one I bought...


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## jmoote (Nov 29, 2007)

jroden said:


> I asked for a lower BB and never bothered to measure. I guess the BB is "low" but the drop is about like a Ridley, so what does that mean?


It's not actually that low... the builder's idea of low maybe, and low compared to cyclocross bikes of the past, but not in today's market.



> Damn fancy expensive steel bike was supposed to be the last one I bought...


Time for a new fancy expensive steel bike?


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## jroden (Jun 15, 2004)

jmoote said:


> It's not actually that low... the builder's idea of low maybe, and low compared to cyclocross bikes of the past, but not in today's market.
> 
> Time for a new fancy expensive steel bike?


I like the looks of that rock lobster frame, I've got a fancy carbon fork already and some rocking 9 speed parts, plus fancy overpriced brakes so I should be all set. If I could find something just right off the shelf I'd prefer that, the specialized and trek both look decent, I ride with a guy with the new giant I'm going to slap a tape on it at our next practice.

Good luck racing tomorrow, I's going to stay stateside the next 2 weeks as we have a nice couple races in Rochester I want to support. I will miss the friendly conversations with customs on the US side of the peace bridge.


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## jmoote (Nov 29, 2007)

jroden said:


> Good luck racing tomorrow, I's going to stay stateside the next 2 weeks as we have a nice couple races in Rochester I want to support. I will miss the friendly conversations with customs on the US side of the peace bridge.


Thanks John, enjoy your racing there. I imagine we'll see you at the Toronto Intl CX?


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## jroden (Jun 15, 2004)

jmoote said:


> Thanks John, enjoy your racing there. I imagine we'll see you at the Toronto Intl CX?


yes, that's the highlight of the season fo rme, we are staying at a hotel with a waterslide near the airport, so the kids are excited too. Cross is great for us family men, last race we camped out at Guelph Lake, kids had a blast.


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## towerscum (Mar 3, 2006)

*but still...*

I suck,and my Waterford with the 70 drop rails on all corners. 

FYI
Mud IIs
54.5 TT
100mm stem
custom Waterford fork


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## jroden (Jun 15, 2004)

i rode my pit bike today with the bigger drop and finished 4th in a tricky muddy race. I felt like I was turning the bike better, I'm still a klutz.


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## mandog (Mar 20, 2010)

What's the drop on a Kona Jake the Snake size 56?


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