[Sandwich]

On your enduro/trail/whatever bike, how low would you go for a static BB height? I know this depends on several factors including tires, wheel size, and travel, but humor me- what height would you want to be at for what travel and wheel size, assuming a 2.3-2.5in tire?

 

[StiHacka]

My trail bike is just under 13". 29er frame with 27.5 wheels, 170/150mm, 2.35/2.3 tires. I like it there, would not go lower, would not go more than .2" higher either.

 

[buckoW]

Depends on how much travel you got. The less travel then the lower you could go. I wouldn’t go lower than what @StiHacka said above and if you’re in the 330mm to 335mm zone then you should be good. Just make sure you keep the reverse Gooseneck seat post just in case the seat angle gets too slack.

 

[Gary]

Ebike 12.9" BB - 170mm front, 160mm rear 27.5 wheels 2.5 front, 2.3"rear tyres
Capra 12.7" BB - 170mm front, 165mm rear 26" wheels 2.5" front, 2.35" rear tyres

Perfectly happy with both but prefer a 10-15mm higher BB on similar travel 29" wheel bikes. But also prefer longer reach with bigger wheel frames.

 

[Gary]

My trail bike is just under 13". 29er frame with 27.5 wheels

What bike is it?

 

[kidwoo]

I had a 160mm travel bike that ended up at 12.2". That was too low. Not because I hit shit but because handling suffered.

12.7-13" for 150-170mm travel bikes is pretty awesome.

 

[StiHacka]

What bike is it?

Gen 1 SC Hightower.

 

[sethimus]

Ebike 12.9" BB - 170mm front, 160mm rear 27.5 wheels 2.5 front, 2.3"rear tyres
Capra 12.7" BB - 170mm front, 165mm rear 26" wheels 2.5" front, 2.35" rear tyres

Perfectly happy with both but prefer a 10-15mm higher BB on similar travel 29" wheel bikes. But also prefer longer reach with bigger wheel frames.

 

[Lelandjt]

I've never ridden a bike that jumped out at me as having too low a BB. It's certainly possible but does a production bike exist with this problem? I don't like a lot of sag and wallow so when climbing with my weight shifted back I always use a shock's climb lever and I absolutely love Scott's system that noticeably reduces sag with a thumb lever. I also have always liked a very forward seat to reduce this weight shift. I also run my forks with very little sag. Maybe those are the keys to living (pedaling) with a low BB.

 

[Gary]

View attachment 151375

Being educated in a tiny forward thinking country obscured by a huge letter "A" on your map I actually do. Yes.
Unfortunately the global bicycle industry has as yet to.

Just for you. With love.

Ebike 328mm BB - 170mm front, 160mm rear 650b wheels 63.5mm front, 58.3mm rear tyres
Capra 323mm BB - 170mm front, 165mm rear 559mm wheels 63.5mm front, 59.7mm rear tyres

Perfectly happy with both but prefer a 10-15mm higher BB on similar travel 700c wheel bikes. But also prefer longer reach with bigger wheel frames.

#5594LYF

 

[Andeh]

My Sentinel (140mm 29er) had 345mm BB, no issues with pedal strikes, could probably have gone a smidge lower. My GG setups are a Smash (145/160 29er w/ 350 BB) that feels a smidge high and a Gnarvana (short travel Frankenstein at 148/160 29er with 345 BB) that feels normal and more planted. I did mullet the Sentinel for a day resulting in a 335mm BB that was noticeably too low and unrideable for me. So my opinion is around 345-350mm is good for a LT 29er if you have to pedal over roots and rocks, 340-345 is good for mostly flowy trails, and anything below that you better not be pedaling over anything other than flat.

 

[Sandwich]

My Sentinel (140mm 29er) had 345mm BB, no issues with pedal strikes, could probably have gone a smidge lower. My GG setups are a Smash (145/160 29er w/ 350 BB) that feels a smidge high and a Gnarvana (short travel Frankenstein at 148/160 29er with 345 BB) that feels normal and more planted. I did mullet the Sentinel for a day resulting in a 335mm BB that was noticeably too low and unrideable for me. So my opinion is around 345-350mm is good for a LT 29er if you have to pedal over roots and rocks, 340-345 is good for mostly flowy trails, and anything below that you better not be pedaling over anything other than flat.

Thanks, I think I'm right where I need to be. My BMC is at 335mm with a 130 fork and 150mm rear end. Short shocking will give me 135mm with the same geometry, so I'm going to do that. lowering the fork from 150 to 130 lengthened my reach, lowered my BB, and steepened the HA, which i am fine with for an east coast trail bike. I have occasionally hit my pedals with the bike setup like this, but not often.

To give more background, I acquired a 190x50mm shock to test fit and it dropped the BB to 320mm with my current setup, though travel would reduce to 115ish mm. Wasn't sure if that was going to work, but it returned the reach back to normal and I think that's too short for me, so we'll stick with the longer shock, more progression, and steeper angles.

 

[Cerberus75]

My Riot has a 350mm BB height. At 140mm/140mm it has a short wheelbase and it felt too high except for flat peddling. I put a -1 angleset and bumped the fork to 160mm and it feels great. I agree that long wheelbase bikes benefit from a higher BB. The Pivot Switchblade is longer this year and the BB has been raised to 350mm as well.

 

[mykel]

135mm travel Knolly Fugitive LT

12.9 Slack / 13.3 Steep.

12.9 feels better, but does pick up a few more fuck-up moments.

 

[jackalope]

GG Trail Pistola: 13.2" / 335 mm

Ancient GG Megatrail (26" hoops): 12.8"/ 325 mm

TP could be a smidge lower, but not complaining where it's at. Wouldn't want the Megatrail 1 mm lower.

 

[jonKranked]

i had an old one off DH bike with a bb height of 12.625". did a lot of pedal smashy, and crank arms too.

 

[jstuhlman]

bromad, high setting, 27.5 wheels, 13.25". never thrown it into low. maybe i'll flip the chip and try.

guess when i ran it as a 26 it would've been mid-12"...felt fine then too although i quickly learned to time my pedaling a bit better.

*edit* - "low" chip setting yielded maybe a few mm difference. curious to see if it translates to anything on the trails this weekend.

 

[Muddy]

To me BB height is just by-product Geometry, where standover / HT Angle / TT Length are the starting point to find a fit. There's not a formula to relate this number - be it 14.55" or 11.85" - to much of anything on a bike with suspension. I don't think it means much of anything as a single quantifier in terms of handling and control. Gets alot of bikes off the showroom floor I bet though.

 

[marshalolson]

Just one additional thought here is that while BB height is more “an easy number to measure” more than anything, too much / too little BB drop does make a difference.

Generally the quicker handling the bike, the more it benefits from increased drop. The longer the bike, a bit less drop can be preferred.

 

[Sandwich]

Just one additional thought here is that while BB height is more “an easy number to measure” more than anything, too much / too little BB drop does make a difference.

Generally the quicker handling the bike, the more it benefits from increased drop. The longer the bike, a bit less drop can be preferred.

I feel like BB drop is hard to measure unless you do the trig. you can start with a MFGers number, but it would theoretically change with a new fork, no?

 

[Muddy]

Just one additional thought here is that while BB height is more “an easy number to measure” more than anything, too much / too little BB drop does make a difference.

Generally the quicker handling the bike, the more it benefits from increased drop. The longer the bike, a bit less drop can be preferred.

BB drop is sometimes included in frame geometry. Problem w/ suspension is it's never linear / true vertical.

 

[Muddy]

I feel like BB drop is hard to measure unless you do the trig. you can start with a MFGers number, but it would theoretically change with a new fork, no?

BB Drop gets touted on road and now, gravel frames for reasons of crankarm choices per rider and also a sense of stability. BB height on trailbikes needs a better descriptor along the lines of a full-compressed measurement plus something in the middle.

But still, an arc of rear wheel travel plus a degree of front wheel ingress while cycling through travel generally defeat this measurement being comparable amongst similar frames/builds.

 

[marshalolson]

I feel like BB drop is hard to measure unless you do the trig. you can start with a MFGers number, but it would theoretically change with a new fork, no?

well, it’s easy to estimate if you can accurately measure BB height and the axle height, then subtract the two (*assumes similar front/rear diameters).

But certainly it’s super hard to figure out, without a built bike in front of you, if it is not published on theGeo table!

the trick with published Geo table BB height is that it is theoretical, and offen fairly off (tires, forks,headset etc) once your setup is on the bike. Where drop is a direct input value to the design of the frame.

 

[marshalolson]

BB drop is sometimes included in frame geometry. Problem w/ suspension is it's never linear / true vertical.

not sure I understand the point being made here. Doesn’t all Geo on a bike change as the suspension is moving due to wheel and rider inputs (hence static Geo tables)?

 

[Muddy]

not sure I understand the point being made here. Doesn’t all Geo on a bike change as the suspension is moving due to wheel and rider inputs (hence static Geo tables)?

What other fixed area is given a vertical measurement on a FS complete bike?

Point being that it's something able to get a measurement, as opposed to something representing consistency toward handling and control.

 

[WestCoastHucker]

1 Kidwoo should be the standard bb height. so approx 13" tall...

 

[marshalolson]

What other fixed area is given a vertical measurement on a FS complete bike?

Stack? Stand over? Rear wheel travel (in some cases it is listed as chord length opposed to arc length)?

reach of course being defined as vertical line from BB as well?

 

[Muddy]

Stack? Stand over? Rear wheel travel (in some cases it is listed as chord length opposed to arc length)?

reach of course being defined as vertical line from BB as well?

Standover varies, as does Stack which gets measured at the BB Shell center. Wheel Travel has a measured range but, it is a variable sweep through that range. So, it's never 'true'.

Only BB Height has a measurement from the ground vertically which seems to keep an even-keel through frame sizes.

 

[Muddy]

1 Kidwoo should be the standard bb height. so approx 13" tall...

We should just bolt wheels onto old Corvette leaf spring ends. Plastic Fantastic.

 

[marshalolson]

Standover varies, as does Stack which gets measured at the BB Shell center. Wheel Travel has a measured range but, it is a variable sweep through that range. So, it's never 'true'.

Only BB Height has a measurement from the ground vertically which seems to keep an even-keel through frame sizes.

stand over isn’t a vertical measurement from the ground? (from the mid-point of the toptube to ground).

anyways, not arguing, genuinely interested, but not understanding exactly Your point.

What does it matter if it’s a vertical measurement from the ground, or the BB shell, or from the axles?

Sort of get where you are going, but not seeing it precisely.

 

[6thElement]

Not that I have any skin in the game, those claiming they notice 1/4" difference in BB height, I'm sure there's more variability in that measurement based on rim/tyre/pressure combinations. BB drop is going to be the better fixed measurement, but no one "knows" what they like in that measurement...

 

[Jm_]

160 RFX is sitting at 13.2, 170 fork and -1 angleset. Based on the **** I've hit, I'm not convinced I want it any lower.

 

[jstuhlman]

most of you running 170mm cranks?

 

[Jm_]

most of you running 170mm cranks?

This was a 175

 

[Muddy]

...not understanding exactly Your point.

What does it matter if it’s a vertical measurement from the ground, or the BB shell, or from the axles?

Not here to call anyone out. The product of applied-math in each example of yours are each an independent factor of being either a bare frame or a complete bike or, as w/ stack height, not at all related to ground clearance.

BB height - on a complete bike, with front and rear suspension - a secondary function as the effective rotational-axis of the bike + rider, reverts by default to offering ground clearance performance.

Point-is is, this cannot be a rational figure to contrast among similar complete bikes.

There's nothing incoherent here, it's not traditional road bikes being discussed. It's full suspension bike frames, becoming complete bikes, with independant rates of suspension travel. ...which therefore skews any consistency to having a 13.1" BB height be anything relative amongst two manufacturer's bikes.

That's all.

 

[canadmos]

This was a 175View attachment 151509

Thats what you get running cranks made out of styrofoam

 

[Sandwich]

it's tubeless sealant, in case of a puncture

 

[jonKranked]

most of you running 170mm cranks?

only on my DH bike.

 

[jonKranked]

another aspect consider re: bb drop, it will also affect how easy/difficult it is to manual a bike. more drop = more difficult

 

[Jm_]

Thats what you get running cranks made out of styrofoam

For what they put up with, I wasn't disappointed.