Bottom bracket drop

[slowgoing]

What model year did Serotta go from a 7cm bb drop to 8cm?

[Marcusaurelius]

What model year did Serotta go from a 7cm bb drop to 8cm?
I am not sure how you can get a 8cm drop when an average road bike with 41 chainstays has a 26.7 bottom bracket height with a 7cm drop. I believe that was with 700x25 tires.

[Ray]

I am not sure how you can get a 8cm drop when an average road bike with 41 chainstays has a 26.7 bottom bracket height with a 7cm drop. I believe that was with 700x25 tires.
Yeah, but I think that all evolved in the days before clipless pedals. With clipless, it's a lot harder to lean far enough in turns to actually strike a pedal and bb's can be correspondingly lower. I've had a couple of bikes with 8cm of drop and others with 77 and 78mm and I've never had a problem with pedal strikes on any of them. If I raced crits the odds might go up, but I've heard of plenty of crit racers that have had low BB bikes and not had problems.

-Ray

[e-RICHIE]

but I've heard of plenty of crit racers that have had low BB bikes and not had problems.

-Ray

pedaling through is the slowest way atmo.

[jerk]

pedaling through is the slowest way atmo.


real crit bikes have low bbs imho.

jerk

[Brian Smith]

real crit bikes have low bbs imho.

jerk

I've never agreed more with 2 short sentences as I do with those two posts above. Cool.

[e-RICHIE]

I've never agreed more with 2 short sentences as I do with those two posts above. Cool.
that's no bs from bs atmo -
don't get high, get on the downlow.

[Fixed]

bro that is if you know how to corner .

[e-RICHIE]

bro that is if you know how to corner .
well if you don't, get out of the way atmo.

[bcm119]

How do you corner "correctly" on your 8cm drop bike if you're in a tight pack of guys with higher BB's who are pedaling through? One cm makes a fairly big difference in lean angle of pedal clipping threshold. I've been in situations where I have to drift through a few strokes while most everyone else pedals through a wide sweeper at speed, and theres no maneuvering room.

[e-RICHIE]

How do you corner "correctly" on your 8cm drop bike if you're in a tight pack of guys with higher BB's who are pedaling through? One cm makes a fairly big difference in lean angle of pedal clipping threshold. I've been in situations where I have to drift through a few strokes while most everyone else pedals through a wide sweeper at speed, and theres no maneuvering room.

if they're pedaling, they're slowing you down.
go around them.

[Grant McLean]

I think what they are saying is don't slow down,
find a way around. If you don't go slow into the
corner, you won't need to speed up.

The theory goes, you don't steer and brake at the
same time, use all the grip possible to turn at
the highest speed the rubber will let you hold on
with.

g

[e-RICHIE]

I think what they are saying is don't slow down,
find a way around. If you don't go slow into the
corner, you won't need to speed up.

The theory goes, you don't steer and brake at the
same time, use all the grip possible to turn at
the highest speed the rubber will let you hold on
with.

g

agreed.
a low cg is a tool to use,
but not as an excuse.

[Grant McLean]

agreed.
a low cg is a tool to use,
but not as an excuse.


I've been riding with some newbies lately, and it's hard for them to
not react by hitting the brakes. I think it's an MTB thing, where
they were programed to throw on the binders every time they approach
a corner. I tired to get them to just keep their darn fingers off the
brake levers! That proved hard for some of them.

g

[jerk]

the inside line is always fastest. take it and don't pedal.

jerk

[bcm119]

I think what they are saying is don't slow down,
find a way around. If you don't go slow into the
corner, you won't need to speed up.

The theory goes, you don't steer and brake at the
same time, use all the grip possible to turn at
the highest speed the rubber will let you hold on
with.

g
I know how the theory goes, but sometimes it isn't realistic to use it. The theory applies to a single cyclist going into a corner. If you're speed is dictated by who's on your front and rear wheel, you can't put the theory to use. Having a low BB in a crit, IME, makes it more difficult to ride smoothly in a pack that is pedaling through wide sweepers. If you're out in front jamming through the turn, its a different story I guess, but unless you're racing in the wrong cat. thats a small percentage of the time.

[e-RICHIE]

snipped - Having a low BB in a crit, IME, makes it more difficult to ride smoothly in a pack that is pedaling through wide sweepers. If you're out in front jamming through the turn, its a different story I guess, but unless you're racing in the wrong cat. thats a small percentage of the time.



that's the thing - pack riding doesn't count.
the race occurs as the pack is whittled down.
if it doesn't whittle down, the race won't be won
in a corner by a guy with a higher cg, it'll be won
by a guy with the most nerve.
if you have the tools, and you have the nerve, what
else is there? otoh, if you're in the pack wondering
where to go next, you're likely gonna follow rather
than lead. you need to make your own luck, and
the bicycle is not what holds you back atmo.

[Fixed]

my bro shook can still slide his rear wheel around a corner .
cheers

[bcm119]

you need to make your own luck, and
the bicycle is not what holds you back atmo.
true

[Fixed]

bro lots of wisdom on this thread i.m.h.o.
cheers

[Too Tall]

What Twizz said is a fair assessment and BCM119 still has this dilema. How to race to finish the race and not contend. Trust me I've "trained" in many crits where I'm riding mid pack with 100 of my bestest friends all intent on the inside line. The effect is a very poor pace thru the best part of the corners and noooobody is strung out. Welcome to masters racing ;)

HOWEVER, Twiz is dead on and a useful technique to use is find a line that let's you approach the corner accelerating at a pace that exits you on the other dewds wheels. Assuming you are going to be 3-5 deep thru the corner what you need to do is softpedal just a bit before the turn letting a bit of a gap open as you tighten your own radius (to protect your line) and accelerate TO the riders wheel(s) infront of you. Done right it will not screw anyone up and your pace thru the corner will be smooth and steady no wasted effort.

Listen to the guys that race, you really have nothing to complain about if you are not contending...in this case you need to cope, manage, do your best and don't yo yo the pack. K?

[e-RICHIE]

What Twizz said is a fair assessment and BCM119 still has this dilema. How to race to finish the race and not contend. Trust me I've "trained" in many crits where I'm riding mid pack with 100 of my bestest friends all intent on the inside line. The effect is a very poor pace thru the best part of the corners and noooobody is strung out. Welcome to masters racing ;)

HOWEVER, Twiz is dead on and a useful technique to use is find a line that let's you approach the corner accelerating at a pace that exits you on the other dewds wheels. Assuming you are going to be 3-5 deep thru the corner what you need to do is softpedal just a bit before the turn letting a bit of a gap open as you tighten your own radius (to protect your line) and accelerate TO the riders wheel(s) infront of you. Done right it will not screw anyone up and your pace thru the corner will be smooth and steady no wasted effort.

Listen to the guys that race, you really have nothing to complain about if you are not contending...in this case you need to cope, manage, do your best and don't yo yo the pack. K?



i think the message here is that racers race, and race
regardless of a drop measurement or a heat treat spec.
things sorta change when there's a prize list and the gun
goes off. suddenly, it's (that bicycle) no longer a high-
brow consumer good. it's a tool. and it goes where the
operator throws it. jmo atmo.

[lnomalley]

i think the message here is that racers race, and race
regardless of a drop measurement or a heat treat spec.
things sorta change when there's a prize list and the gun
goes off. suddenly, it's (that bicycle) no longer a high-
brow consumer good. it's a tool. and it goes where the
operator throws it. jmo atmo.

word to the mother. racing is not like any other kind of riding. your bike is just this thing that happens to be between your legs... it's like you wake up to find a bear is attacking you and so you grab whatever is nxt to you to attack the bear back and if you really really want to live.. you win. and then afterwards you go.. wow... i needed a gun and not an oprah book.

[e-RICHIE]

wow... i needed a gun and not an oprah book.


t shirt and bumper sticker material atmo.
you get a one week window or i co-opt that
phrase starting in the nutmeg state cheers.

[ergott]

this thing that happens to be between your legs...

Now that's bumper sticker material!

[Grant McLean]

t shirt and bumper sticker material atmo.
you get a one week window or i co-opt that
phrase starting in the nutmeg state cheers.

you can put this photo on the back...

http://forums.thepaceline.net/showpost.php?p=200131&postcount=19


g

[David Kirk]

that's the thing - pack riding doesn't count.
the race occurs as the pack is whittled down.
if it doesn't whittle down, the race won't be won
in a corner by a guy with a higher cg, it'll be won
by a guy with the most nerve.
if you have the tools, and you have the nerve, what
else is there? otoh, if you're in the pack wondering
where to go next, you're likely gonna follow rather
than lead. you need to make your own luck, and
the bicycle is not what holds you back atmo.

Word squared.

Dave

[lnomalley]

you know how you kill a bear with an oprah book? read it out loud to the bear.

your turn.

[e-RICHIE]

you know how you kill a bear with an oprah book? read it out loud to the bear.

your turn.

if you meet your book reviewer, kill him.

[chrisroph]

Bikes with low bb's ride better. Period.

[lnomalley]

Bikes with low bb's ride better. Period.

um.. that's like saying one legged girls are better kissers. it's a relationship thing. bb, chainstay length, vertical compliance, front center and rear center.. all together in relationship effect how and what a bike does.

i'll take a nervous bike over a long one anyday. one bums me out and the other makes for good conversation. so.. no definitive statements about better cuz there is no there there. oversteer or understeer or balance has as much to do with where you are riding as what you are riding. now if i could change the angles as the terrain changed.. that would be chill.. but you sort of can by moving your body around on the bike... you can change the seat tube angle and you can drop your center of gravity and all kinds of stuff.

you don't talk ot the bear about the symbolism in chapter 5... you wack it in the berries...and play dead.

[manet]

.

[flydhest]

one-legged girls actually are better kissers.

[Fixed]

bro it funny how 1 cm can feel so different in the b.b. i.m.h.o.
cheers

[lnomalley]

even 5mm in chainstay length can change the personality of a rig.

[e-RICHIE]

twins have more fun

[cpg]

one-legged girls actually are better kissers.

True but are they vertically compliant?

Curt

[flydhest]

True but are they vertically compliant?

Curt

Curt,

I'm more interested in compliance after we get horizontal.

[Brian Smith]

True but are they vertically compliant?

Curt

yeah, but not "laterally rigid," so it's a huge tradeoff.

:crap: :crap: :crap:

[slowgoing]

Who? Eileen?

[chrisroph]

um.. that's like saying one legged girls are better kissers. it's a relationship thing. bb, chainstay length, vertical compliance, front center and rear center.. all together in relationship effect how and what a bike does.

i'll take a nervous bike over a long one anyday. one bums me out and the other makes for good conversation. so.. no definitive statements about better cuz there is no there there. oversteer or understeer or balance has as much to do with where you are riding as what you are riding. now if i could change the angles as the terrain changed.. that would be chill.. but you sort of can by moving your body around on the bike... you can change the seat tube angle and you can drop your center of gravity and all kinds of stuff.

you don't talk ot the bear about the symbolism in chapter 5... you wack it in the berries...and play dead.
\
We all have our preferences. I've never kissed a one-legged girl but I'm sure there are many with great lips.

Sure, there are many factors that go into how she rides, but I've always liked bikes with lower bb's, and dark skinned girls with full lips and hips.

[Dr. Doofus]

one-legged girls actually are better kissers.

ask

Mr. Pointer

he would know

i-d-h-o atmo

yo

[Fixed]

\
We all have our preferences. I've never kissed a one-legged girl but I'm sure there are many with great lips.

Sure, there are many factors that go into how she rides, but I've always liked bikes with lower bb's, and dark skinned girls with full lips and hips.
yeah.. bro me too
cheers

[vandeda]

bro it funny how 1 cm can feel so different in the b.b. i.m.h.o.
cheers

ok ... i'm bringing back an old thread ... but yeah, this is sooooo true. The vast majority of my commuting (and riding) is only my Surly Steamroller with a 7 cm bb drop, 170 mm cranks and fixed gear of course. Today, I decide for whatever reason that I want to commute on my new to me Fierte with it's 8 cm bb drop, 170 mm cranks and geared.

Being that I'm used to pedaling through corners because ... well ... I have no choice on the fixed gear, I just did the same on my Serotta as I'm a fairly leisurely rider as it is. Did my typical commute ... and my gosh, at least 3 pedal strikes on what I felt was anything but aggressive cornering. I couldn't believe how much of a difference a mere cm made, but it seems like I couldn't keep that pedal off the ground.

Anyway .... I love the Fierte I picked up off the classifieds here from thwart. Man, I can see why the Fierte won the plush ride award ... this thing is way comfy. I really like the way it rides ... this bike may actually be a keeper.

d

[Chief]

What model year did Serotta go from a 7cm bb drop to 8cm?

To address your question, I cannot be exactly sure, but I have a 2002 Ottrott with a 8 cm drop and I believe Serotta went to a 8 cm drop when they first offered the Ottrott. I have yet to drag a pedal since the outside pedal is the one that should be down and loaded when properly cornering. I will tell you that at 6'2" I feel much lower on my Ottrott with its 8 cm drop than guys that are several inches shorter than me on bikes with 7 cm drops.

[vandeda]

I have yet to drag a pedal since the outside pedal is the one that should be down and loaded when properly cornering.

That I completely understand. To me this was leisurely cornering .... not aggressive at all. Being that they felt leisurely, I felt that I could just pedal through as I would my fixed gear. But, I just need to retrain my brain as to what "leisurely" and "aggressive" mean when it comes to cornering, pedals and the ground on the Fierte vs. my other bikes.

I will tell you that at 6'2" I feel much lower on my Ottrott with its 8 cm drop than guys that are several inches shorter than me on bikes with 7 cm drops.

My Calfee always felt like I was sitting very high up on the bike compared to all my other bikes, even ones with the same bb drop. It was always a weird sensation to me and I never really enjoyed it (probably one reason I don't own the bike anymore either).

[merckx]

Doesn't BB drop have more to do with BB stiffness than CG change? Lower BB requires longer DT and CS and maybe softer ride? Does a 1cm change in CG really make a difference?

[Ray]

Doesn't BB drop have more to do with BB stiffness than CG change? Lower BB requires longer DT and CS and maybe softer ride? Does a 1cm change in CG really make a difference?
Go back and read the thread (skip the part about one-legged girls kissing better if you must!). Lower bb's do matter in terms of CG. There are a lot of variables and, like anything else, a low BB rarely occurs in a vacuum. But, all else being equal, a bike with 8cm of drop will handle differently and lean into corners differently than a bike with 7cm of drop. I've had plenty of both and I like lower better for any on-road application.

-Ray

[RPS]

I will tell you that at 6'2" I feel much lower on my Ottrott with its 8 cm drop than guys that are several inches shorter than me on bikes with 7 cm drops.The elevation of the center of gravity of a tall rider can easily be 10 centimeters or more higher than that of a short rider.

At your height you probably ride in the order of about 5 centimeters higher than I do. In any case our CG differences exceed BBKT.

[RPS]

If the CG has that significant an impact on how a bike corners, does it mean that tall riders are at a considerable disadvantage when cornering?

[CarlosContreros]

even 5mm in chainstay length can change the personality of a rig.

In what way?
Would moving my skewer back in my dropouts help to transfer a bit
of weight to the front?

I could move my wheels about 1/2" further back in my dropouts..and since
my bike feels a bit "back-heavy" I'm hoping this will help to equalize weight
distribution.

[RPS]

In what way?
Would moving my skewer back in my dropouts help to transfer a bit
of weight to the front?Carlos, the question we should ask IMHO is how big a difference does it make (or should it make) relative to other factors.

Let's take an average guy riding a bike with 100 CM wheelbase with a weight distribution of 60-rear/40-front as an example.

If we move the rear wheel back 1 centimeter by stretching the chainstays and do nothing else, the weight distribution will change to about 59.4-rear/40.6 front (disregarding the effect of the rear wheel's weight).

How does that compare with a little extra upper-body weight due to weight lifting, or a little extra weight around the belly and butt during winter, or an extra water bottle in your jersey pocket, or a heavier tool bag? Only the rider can know how sensitive he/she is to those kinds of changes IMO.

[CarlosContreros]

Carlos, the question we should ask IMHO is how big a difference does it make (or should it make) relative to other factors.

Let's take an average guy riding a bike with 100 CM wheelbase with a weight distribution of 60-rear/40-front as an example.

If we move the rear wheel back 1 centimeter by stretching the chainstays and do nothing else, the weight distribution will change to about 59.4-rear/40.6 front (disregarding the effect of the rear wheel's weight).

How does that compare with a little extra upper-body weight due to weight lifting, or a little extra weight around the belly and butt during winter, or an extra water bottle in your jersey pocket, or a heavier tool bag? Only the rider can know how sensitive he/she is to those kinds of changes IMO.

Yeah!
Thanks for the reality check RPS....I know the problem!
When I'm at 190 lbs......I have no problem with a sensation of
the bike being....."rear-heavy"!
But I'm currently at 200 lbs...and I feel the weight in the back!

It's not like I'm fat...I'm over 6'4''....but nonetheless all my poor Merckx
feels is the 200 lbs.!! :confused: :confused:

[Fixed]

bro this is easy ..do you want to be lite in the loafers or not ? imho
cheers :beer:

[Pete Serotta]

CPG, e-Richie, and Dave Kirk are the exert bb sources.

We now know Flydhest is the one legged source for bike riders... :D

[e-RICHIE]

CPG, e-Richie, and Dave Kirk are the expert bb sources.

We now know Flydhest is the one legged source for bike riders... :D
pete gets it atmo.
i'm in the 8cm camp since 1978.
i simply heart it.


ps
arrange disorder
:D ;) ;)
;) :D :D
:D ;) :D

[Dave]

If the CG has that significant an impact on how a bike corners, does it mean that tall riders are at a considerable disadvantage when cornering?

At the very end of this discussion, comes an obvious point. Small riders on small frames will have a much lower CG than those riding frames that are 5-10cm larger. A 1cm lower riding position, while helpful, is a drop in the bucket compared with a 5-10cm lower saddle height. Riding a 51cm frame, I don't need an 8cm BB drop to corner fast.

[David Kirk]

Low is the new black.........or at least the new norm.

And yes the tall rider gets the short end of the stick on this and a good number of other fronts in cycling. The increase in the height of the CG is nothing compared to the increase of frontal area of the tall guy. Don't ask me how I know.

I can only speak from a personal perspective on this but as a tall guy myself I've always favored events that are inherently slow. By that I meant races that were steep. When you are going slow uphill then aero drag is much less of an issue and my fairly good power to weight ratio could come into play. Combine this with the simple fact that as a guy who is 6'4" it's pretty hard to get much of a draft or a rest behind a 5'9" guy. This, for me at least, was a good reason to race off road. The lower speeds of mountain bike racing made it possible to be more competitive. Whether that is the reason or not I'll never really know but I did have much more success in the dirt.

All that said I like the BB to be low.

Dave

[merckx]

pete gets it atmo.
i'm in the 8cm camp since 1978.
i simply heart it.


ps
arrange disorder
:D ;) ;)
;) :D :D
:D ;) :D

This is a pretty good endorsement to get down and low. e-Ritchie, can you please explain how you came to this conclusion? Is it really a CG thing?

[merckx]

I drag this up again because I just came across this. Valid?

www.davesbikeblog.blogspot.com/2007/02/bottom-bracket-height.html

[e-RICHIE]

This is a pretty good endorsement to get down and low. e-Ritchie, can you please explain how you came to this conclusion? Is it really a CG thing?
it's a CG thing and it's a gestalt thing atmo. first of all, atmo there is no
reason to be any higher than needed and, in general terms, an 8cm drop
covers most bases on a road bicycle. i am not able to get into the but i
can't pedal through corners excuse because i feel that leaning over at
speed is the fastest route through any turn, and when the bicycle's CG is
low, the act of resuming the pedal stroke while still leaned over is much
more confidence inspiring. otoh, if you do not race and the bicycle is not
a tool, none of this matters at all atmo.

there are other benefits of a low CG, and some are real and others are
visual. all things being equal (on level frames, at least) the down tube
and seat stays are shorter, and the head tube (the part below the top
tube) is smaller. atmo, the angle at which the chainstays leave the bb
shell is much more elegant on a bicycle with a low CG. to me, this also
matters atmo. hey - gotta run.





ps
arrange disorder
;) ;) ;)
;) ;) ;)
;) ;) :D

[merckx]

Thanks, buddy.

[swoop]

for my race bike i like a 6.5 drop. its high (i'm not tall).... it's an acquired taste... and it does buy you a little something coming out of a corner and getting on it early.
i swear buy it... and there were times this year when i felt it gave me an advantage...
but i also like pepper on my cottage cheese. e-richie has forgotten more than i'll ever know... but i just wanted to add this because you know... you never know if you're that guy that likes things everyone else hates unless you try it.

if its just a bike for riding and not racing.. for club rides or for riding for happiness.... low is the way to go... but man sometimes i just like way too much pepper on that cottage cheese.

call me weird.

[e-RICHIE]

call me weird.
weird.

[swoop]

you ever date a girl you hated just because the tension between you was somehow fulfilling?

its the bike equivalent.

really weird?

[e-RICHIE]

you ever date a girl you hated just because the tension between you was somehow fulfilling?

its the bike equivlent.

really weird?
that is so dr joy atmo.

[thejen12]

At the very end of this discussion, comes an obvious point. Small riders on small frames will have a much lower CG than those riding frames that are 5-10cm larger.
Another advantage that we small riders have is shorter cranks! That gives us less chance of hitting a pedal with a low BB than the longer-crank riders.

Jenn

[11.4]

Just for some additional pepper on that cottage cheese ...

The Aussies have been bumping up their bottom bracket heights quite fiercely. The Aussie team BT Stealths now have only a 3 cm drop and a couple prototypes have even less. They're now adopting this drop on their road TT bikes and even on some regular road bikes.

Their reasoning: They did a lot of wind tunnel studies on bikes and found that there's a huge amount of air turbulence (and thus resistance) under the bike, created by both the front and back wheel throwing air in that direction as well as the simple profile of the bottom bracket hanging down. Rider times improved when they raised the bottom bracket.

Specialized situations, of course, but interesting that there's another aspect to speed and bottom bracket drop that we perhaps hadn't been focusing on before. I'd never discard handling to improve aerodynamics in a regular road bike, but I do have to say that despite the minimal drop, the new Stealths have incredibly good handling and maneuverability.

[RPS]

At the very end of this discussion, comes an obvious point. Small riders on small frames will have a much lower CG than those riding frames that are 5-10cm larger. A 1cm lower riding position, while helpful, is a drop in the bucket compared with a 5-10cm lower saddle height. Riding a 51cm frame, I don't need an 8cm BB drop to corner fast.Exactly Dave; that was the point I was making.

Its one thing to say you shouldn’t need a high BBKT in the first place and another to imply that placing a rider 1-CM closer to the road makes a bike corner significantly faster. These are two separate issues.

A strong case can be made for not pedaling through most sharp corners in order to maximize available traction, but the positive effect of a lower center of gravity is much weaker (although it exist the difference is insignificant for most of us IMO).

As Dave Moulton states in his blog, a bike is not like a car because it leans into turns. And whether you are short or tall or ride a bike with 7 or 8 CM of BBKT drop, the angle to the pavement will be the same for a given set of conditions.

If nothing else, it’s easier to throw your leg over a bike with a lower BBKT. ;)

[e-RICHIE]

...even on some regular road bikes.
mebbe the idea is to make a normal frame design
and compact it bt reducing the metal at the bottom
of the s.t. rather than at the top atmo.

[chrisroph]

Just for some additional pepper on that cottage cheese ...

The Aussies have been bumping up their bottom bracket heights quite fiercely. The Aussie team BT Stealths now have only a 3 cm drop and a couple prototypes have even less. They're now adopting this drop on their road TT bikes and even on some regular road bikes.

Their reasoning: They did a lot of wind tunnel studies on bikes and found that there's a huge amount of air turbulence (and thus resistance) under the bike, created by both the front and back wheel throwing air in that direction as well as the simple profile of the bottom bracket hanging down. Rider times improved when they raised the bottom bracket.

Specialized situations, of course, but interesting that there's another aspect to speed and bottom bracket drop that we perhaps hadn't been focusing on before. I'd never discard handling to improve aerodynamics in a regular road bike, but I do have to say that despite the minimal drop, the new Stealths have incredibly good handling and maneuverability.

interesting and counterintuitive, which to me at least says that the lower rider pushes less wind. raising the bb of course perches the rider higher in the air which seems like it would catch more wind, and make drafting a little tougher too (if we are discussing mass start bikes as opposed to tt bikes).

[CNY rider]

mebbe the idea is to make a normal frame design
and compact it bt reducing the metal at the bottom
of the s.t. rather than at the top atmo.


Every so often I start thinking I have a clue what you builder types are talking about when it comes to geometry and fit.

Then you throw out something like this and i have to ponder it for hours just to scratch the surface.

Could you repeat that, and explain a little more? I think the rest of the class wasn't paying close attention. ;)

[swoop]

Every so often I start thinking I have a clue what you builder types are talking about when it comes to geometry and fit.

Then you throw out something like this and i have to ponder it for hours just to scratch the surface.

Could you repeat that, and explain a little more? I think the rest of the class wasn't paying close attention. ;)

he's saying make a sloping downtube.... make the bottom end of the triangle shorter rather than the top like they do in sloping..
for all the new bells and whistles it surprises me that more companies don't play with bb width too... there was perhaps something to that superbike stuff...

[11.4]

interesting and counterintuitive, which to me at least says that the lower rider pushes less wind. raising the bb of course perches the rider higher in the air which seems like it would catch more wind, and make drafting a little tougher too (if we are discussing mass start bikes as opposed to tt bikes).

If the rider is in the same profile and higher up, he still presents the same profile to the wind. One thing that I suspect the Aussies are addressing is the tendency for much more air friction closer to the ground (any air turbulence the bike creates near the ground is slowed -- and thus becomes more significant to efficiency -- because it basically hits the ground and then is reflected back into oncoming waves of pressure, which increases the effect of the turbulence or wind resistance). This is also why racing sailboats strive to get as high a masthead as possible and put as much sail area as high as possible -- the wind velocity is significantly higher as you get away from the surface of the water.

To e-Richie's last comment, that would make sense but the Aussies aren't decreasing the frame size, just raising the whole triangle. Of course with every tube curved on the BT except the fork steer, plus with a massive seat tube extension, it's fair to say that the apparent seat tube length on my BT is a lot less than on my traditional steel track frame -- so Richard may actually be correct.

Anyway, on the track at least it's quite impressive how well this bike handles. The basic geometry isn't extreme (74/73 angles, and a fairly moderate trail) but you wouldn't know you had such a high bottom bracket until you get off the bike and drop down an extra 4 cm or so.

[11.4]

Oh, and with 165 mm cranks, I've never found a need for a particularly high bottom bracket, even on steeper tracks. The old pedal clearance issue tends to be a phantom. This is partly because on steeper tracks you have to ride faster just to avoid tire slipping and partly because track events have changed in recent years so sprints and such are faster and much longer. There isn't really any trackstanding and it's more about riding a fast long sprint. In that mode, you don't need the bottom bracket clearance. Even riding the top of the banking as you get ready for a 200m effort, the current approach is to be up to a much higher speed before you dive for the line. Some of this is to give better results with more power, some is because on 250m tracks you pretty much have to come down on the pole on the back straight and in effect are doing more like a 300m effort. Interesting how things change. My primary steel track frame has a 6 cm drop and is well more than enough clearance. It doesn't even come close. This increased available clearance does enable riders to go to longer cranks, which is increasingly common these days -- you see pursuiters riding 177.5's and see riders doing 200m efforts on a tall track like Moscow switching from normal 170's to 177.5's. So much for old-style track racing.

[Grant McLean]

he's saying make a sloping downtube.... make the bottom end of the triangle shorter rather than the top like they do in sloping..
for all the new bells and whistles it surprises me that more companies don't play with bb width too... there was perhaps something to that superbike stuff...

I wonder if it would catch on?

Maybe keep moving everything in until you end up with 1 big beam?

-g