observe:

http://www.alexmoulton.co.uk/

now then, as we see the chainstay on these bikes slopes UP to the bb - reverse drop. it does so because of the small wheel.

perhaps you are cofusing "bb DROP", with "bb HEIGHT". they are not the same thing. "bb height" would fit your assertions, but not bb drop.

bb drop and its relation to wheel size is observable on that moultan, and on the bikes at the top of this thread, just as i said.

Irrelevant, and you have still provided no support for your argument that bottom bracket height or drop is somehow tied to wheel size. (There are limits, of course, but that's not your argument.) You argue that it is not only "dependent" but "defined" by wheel size. To support your argument you would have to prove that every bottom bracket shell is, for example, 9.5 inches off the ground. Then, and only then, would wheel size affect "drop". Since that is not the case, however, your argument fails. A 650 wheeled bike could have a higher or lower bottom bracket than a 700c bike, and conversly a 700c bike could have a higher or lower bottom bracket than a 650 bike. Depending on the desired handling or ride characteristics, customers' requests, crank length or intended uses a frame designer can raise or lower the bottom bracket regardless of wheel size.

jeez Diablo - ttn has repeatedly and patiently explained that the angle of the chainstay to the horizontal will differ for different sized wheels - with 700c wheels the chainstay slopes down to the BB (put differently, the wheel axle is ABOVE the BB) - with small wheels (eg 20") the chainstay slopes up to the BB (put differently, the wheel axle is BELOW the BB) - all bikes have the BB at roughly the same height - hence, the angle of the chainstay IS dictated by the wheel size

As I have repeatedly and patiently explained to ttn, your argument as well is based on an incorrect assumption.

yep, that is pretty much the reply I expected

yes, ozzy. maybe diablo should telephone a few bike makers, to set them straight. let's see here, a quick check of a few geometry charts reveals the following:

bb drop on (all) 700c wheeled cervelo's = 6.0 cm. 650 = 4.3cm

bb drop on (all) 700c quintana roo's = 6.8 cm. 650 = 4.0cm

bb drop on (all) 700c multisport waterfords = 7.5cm. 650 = 5.0cm

anyway, getting back to original question, this average difference in bb drop between wheelsizes of 2.0 cm DOES result in observable changes in the angle of the chainstay, in a practical sense, to the horizontal. a quick eyeball of that angle of a bike rolling down the road such as the two bikes at the top of the thread will tell a fellow if the frame is a 650 or 700 frame by design. thanks for playing, diablo, vanna white has a lovely parting gift for you backstage.

OK, let's make this simple, you are both wrong. BB drop does depend on wheelsize in a given frame, but not the way ttn says it does. If you take a 700c frameset, it will have a certain drop. Now, if you toss in two 650c wheels, the front and rear wheel axles come closer to the ground (by about an inch) as does the bb. So the bb drop from wheel axle to bb is zero, nada. So in that sense Diablo is sort of right. Except it would be more likely to change the fork into a 650c fork. If you do that, the headtube of the frame drops, while the rear stays at the same spot. The bb drops (roughly by about 1cm), but the front and rear axle stay in the same spot (they are still 1/2 wheel off the ground). So the bb drop increases compared to having that same frame with 700c wheels and a 700c fork.

But the whole discussion is moot, there is no way Lori would ride a 700c frame with 650c wheels. This frame is an obvious custom, just like Peter's bike is.

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Gerard Vroomen
3T.bike
OPEN cycle

i think you need to read what i said again, gerard.

obviously, if you simply slap a set of 650 wheels into a 700c frame the bb drop will not change in that frame, tho the bb height will. however, if you did that the bb height would be so low as to be a problem in riding the thing. my point is that a 650 wheeled frame needs to have less bb drop designed into it from the get-go, in order to place the bb at a suitable height and that design results in observable aspects. in the case of a cervelo, 1.7 cm less. so then, when fitted with wheels, sitting on the ground and in reference to it, the angle of the chainstay on a 650 wheeled P3 is observably different from that of a 700c wheeled one. the 650 wheeled P3's chainstay will be closer to horizontal. if you made a 16 inch wheeled P3 and placed the bb at a suitable height with that frame for riding, the chainstay would slope UP from the axle, to meet it. all i am saying is that an observer, standing alongside these various bikes, can look at them and see these design features fairly easily - can tell if the thing was designed with 16 inch, or 700c wheels in mind - or with a little extra scrutiny 700 vs 650.

i have a custom bike built with 650 wheels and it sure looks a lot like lori's bike. the frame size are similar 47 cm as i'm 5'6" tall. the bike was designed for ironman distance races and the long stays give a comfortable ride and the chain line is not as severe as a bike with short stays and this equates to a smoother shifting and performance.

gerard, don't worry, ttn tends not to read other's posts well before responding either;-)

In his desperate attempts to prove himself right ttn's arguments are a bit helter skelter because he claims these global absolutes regarding the relationship between wheel size and bb drop (or height), but then as examples only uses a specific frameset.

Regardless, ttn is wrong.

As another poster commented, bottom bracket position is dependant on several things. I'll see if I can make this simple so ttn can understand it. Lets look at it as bottom bracket "height" off the ground. For track and crit bikes the bottom bracket can tend to be higher because of the pedal clearance needed while pedaling in the turns, whereas touring or time trial bikes can tend to have lower bottom brackets. (I'm not going to get into the argument of bikes or companies that vary from that traditional norm because those are exceptions.) That height varies from the extremes of around 9.75 inches to 11.5 inches just based on catalogs I have laying around. Do your math and you'll see that the difference is 1.75 inches. Now, the difference in axle height between a 650 and 700c wheels is less than 1 inch, so there's a lot of room for variance, and a 650 touring bike (for example) could have a greater "drop" than a 700c crit bike depending on how high or low the bottom bracket is on each respective bike. Furthermore, a 650 bike with a low bottom bracket could have it's chainstays slope downwards towards the bb shell (with more "drop") instead of being relatively horizontal, whereas a 700c bike with a high bottom bracket could have chainstays that do not slope downwards and are more horizontal towards the bb shell (having less "drop") instead of sloping downwards. The shorter the chainstay the more accentuated it looks, but we're not talking about kiddie bikes here, we're talking about 650 versus 700c with on average about .9 inch difference in axle heights. Lastly, regarding ttn's latest ridiculous and illogical evidence to support his argument, lets look at another ABG bike, the Litespeed Vortex, which in 700c wheels sizes it's bottom bracket height varies from 6.7 to 7.4 cm.

From the pictures of Lori's bike, all I can tell you is that it's a 650 bike with relatively long chainstays and maybe it's designed that way for comfort and chainline as another poster stated.

sigh.

mojo, yes, if you poke around and find a 650 wheeled touring bike and compare it to a 700c crit bike you can catch me out, you clever rascal ( talk about " desparate need to be right" . . . . . 650 wheeled touring bike ????????? ).

but we are not talking about 650 wheeled touring bikes, and high bottombracketed 700c crit bikes, are we? altho, as you know ( i hope), everything i have said up to now would be equally true by way of comaprison if we were discussing 700c touring bikes and high bottombracketed 650 crit bikes in comparison, respectively.

anyway, getting back to topic at hand from the top of the thread, we are discussing looking at two bikes of identical intent, from the same manufacturer, and using elementary geometry to tell us that such bikes will invariably use different bb drops for different sized wheels and if you put one such frame designed for one sized wheel next to a ( similarly intended) frame designed for another sized wheel you can see the difference of that geometry in the angle of the chainstay. that is all. what is there to argue about, it is a freaking triangle with the dimensions written out in front of you !

finally, as for the vortex . . . . . guess what - if the vortex came in a 650 wheeled version it would have a bb drop about 2 cm less than the ones you list, and if you held the 650 version up alongside the 700c version you could tell the difference from the angle of the chainstay being less as compared to the horizontal. funny how that works, eh?

he come on guys, do you all think gerard knows a damm thing about bikes? please show him how it works! I mean.... he's just.......building them?

Why is it the most band-width seems to be taken up by the most mundane topics. Whatever the bikes configurations, they seem to be doing reasonably well on them.

Do you think that Lori is cruising along the Queen K wondering about the length of her Chainstays!

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Steve Fleck @stevefleck | Blog

As always, your arguments are fallacious and your logic is flawed. No matter how much you attempt to modify the argument, ignore the facts and peoples' posts, edit your own posts or come forward with more non sequiturs, you were wrong.