for those who think they know geometry and bb drop

[eddief]

For the last few years, my bikes have been built or bought around thinking I need/like 8 cm of bb drop. That is true for my Riv Ram, my Gunnar Sport, and my Rex. I am looking at a bike with steeper angles 73.1 STA and 73.5 HTA and 6.8 BB drop. The contact points could be dialed in perfectly and I know this bike should feel quicker in the steering?, but what sensation would the higher bb bring to the feel of the ride?

I have 3 sort of middle of the road sport bikes, but thinking something lighter and racier might be fun.

Any info or ways to consider steeper angles and higher bb appreciated.

[crankles]

what are the HT/ST and trail of your other bikes?

[Ken Robb]

with similar contact points your standover clearance will be reduced.

[eddief]

60 cm Gunnar Sport

HTA 72.5
STA 73
BB drop 7.5
Trail 61

Bike to be named later

HTA 73.5
STA 73.1
BB drop 6.8
Trail 56.1

[bicycletricycle]

At first a bike with a higher bb feels like it resists side to side movement more than usual. You can feel it a fair amount when out of the saddle and you want to sway the bike back and forth. I remember Grant Peterson describing this feeling when he was talking about the Legolas CX bike they used to make. He said it felt like you were riding in a small trench that limited side to side movement. This feeling goes away. I know that many people also feel a difference in descending at high speed, I have not noticed this as much.

[Ralph]

I think my 56 CM (no CF) CAAD 5 rides fine. It has 6.9 CM BB drop according to C Dale web site.

TT is 56 CM
STA is 73.5
HTA is 73
Chain stay length is 40.5
Fork Rake 4.5
BB height 26.8
Trail 5.6

Some consider this a race bike, but I like riding it as a daily rider. I also have a more relaxed built slightly longer WB 56 CM custom steel bike. With nice tires on both, I can't tell near as much difference in how they ride as Internet "wisdom" would have you believe.

[slowandsteady]

Am I mistaken or won't you notice the trail difference MUCH more than the BB height in your scenario above 6.1 vs 5.6 is a pretty big difference - the lower number being more racey,

[TimD]

I look at it this way - a lower BB (more BB drop) effectively reduces the saddle height and, potentially, the saddle-to-bar drop. I cannot really tolerate more than about 3cm of saddle-to-bar drop.

Reduced saddle height, in turn, reduces the required HT length / stack height somewhat. Sloping TTs (of which I'm not a fan) solve any standover issues.

When you are in the realm of 330mm steerers and 230+ mm HTs, as I am, a BB drop of 8cm vs. 6.5 cm can make a significant difference in how long/far I can ride in semi-comfort, all other things being equal.

I'd second the notion that the fork trail decrease probably affects the handling more, but a higher BB has to raise the CG somewhat, at least when the pedals are loaded.

[e-RICHIE]

I look at it this way - a lower BB (more BB drop) effectively reduces the saddle height and, potentially, the saddle-to-bar drop. I cannot really tolerate more than about 3cm of saddle-to-bar drop.

Reduced saddle height, in turn, reduces the required HT length / stack height somewhat. Sloping TTs (of which I'm not a fan) solve any standover issues.

When you are in the realm of 330mm steerers and 230+ mm HTs, as I am, a BB drop of 8cm vs. 6.5 cm can make a significant difference in how long/far I can ride in semi-comfort, all other things being equal.

I'd second the notion that the fork trail decrease probably affects the handling more, but a higher BB has to raise the CG somewhat, at least when the pedals are loaded.

no it doesn't work this way - it (a lower bb/more drop) lowers the entire bicycle by said amount,
except for the top of the wheels since the diameter is constant atmo. and if the chat is about a
drop difference of a cm or less, unless you are height-challenged, the lower (or higher) saddle from
a standing-next-to-the-horse perspective will be negligible.

ps

arrange disorder

:cool: :cool: :cool:
:cool: :cool: :)
:) :) :cool:

[eddief]

who has a tough time visualizing some of the geo dynamics. Richie, might you take a swag, if you could, at some sort of description of the difference in handling and overall ride feel, if any, those two factors would make to an "average" non-race rider?

that being a smaller trail number combined with a higher bb number.

[David Kirk]

I hate to sound too obtuse but.......... describing the differences is a bit like describing a color. One thing I can say for sure is that it will feel a bit different. You may like the difference and you may not.

that said - normally a lower BB will make the bike feel more stable and make it feel like you are more 'in' the bike than 'on' the bike. I like this feeling myself and tend to use lowish BB's when I can.

A smaller trail number will in most cases make the bike feel more intuitive at lower speeds and possible a bit busy at higher speeds. But..... the trail is just one factor. Weight distribution, front center, bar drop, wheelbase.......etc all factor in and can not be separated.

I personally like low BB's and trail in the 5.7 range and think many would agree with me. But you can not be sure until you ride it.

Obtuse I know.

Dave

[eddief]

and since my current bikes are all of a type, I am going to take a whack at the geo listed above. I sometimes think that "I think" I like slacker angles and lower bb's, but may have come that based on a trend I started for myself in the last 5 years and last 10 bikes.

Quite frankly, I may like being at taller angles, more forward a bit, and with smaller trail steering. Time il tell.

[pbjbike]

The new BB will only be a tad more than 1/4 inch higher, (.27"). I doubt you'll notice the difference in a straight line, and you'll be able to pedal through corners. The front end will be a more noticeable change, and, IMO, a welcome one from the slacker angles you are used to. You aren't pushing the limits with the changes. Let us know how it works out. :beer: