Low hanging a+se - the BB question

[2manyoranges]

Having last year alleviated the pedal strike issues on the mmmBop with some 165 cranks, I suddenly realised I hadn’t done a round of BB height measurements on my bikes. And…? Blimey…the Stanton hardtail 29ers notionally have ‘a low BB’ but at 330mm it’s MILES higher than the mmmBop’s 280mm. The BfEMax sits at 325mm. Stif Squatch at 293mm…..

Whilst ‘BB drop’ is a quoted figure in most makers’ geometry charts, it‘s made complex by the variation in wheel size - 27.5, 29, mullet - and BB height can vary with tyre size and suspension travel. The mmmBop feels really planted…and RA and other niche manufacturers are running low BBs. But don’t expect easy clearance of logs and rocks…bang crash wallop.

Maybe riding trends have changed…I remember a high BB being seen as quite an asset in the 90s….

 

[Russell]

I suspect that ground clearance is better now than in the 90s because we’re not running 52t outer rings any more. If my BB shell is hitting obstacles, I’ve got bigger problems!

 

[2manyoranges]

Good point.

 

[stevet1]

Stanton's normally have decently high BB's, they've not fallen into the 'lower' is better trap just yet.

 

[clubby]

Maybe riding trends have changed…I remember a high BB being seen as quite an asset in the 90s….

So we’re 71 degree head tube angles

I think we’ve hit (literally) the limit of low bb’s and will see a creep back. My Whyte ebike was too low so I changed to the second gen linkage to raise it 12mm. Made a big difference. My Sentinel is also really low and I’ve recently fitted 155 Hope cranks to help pedalling on techy climbs.

 

[2manyoranges]

So we’re 71 degree head tube angles

I think we’ve hit (literally) the limit of low bb’s and will see a creep back. My Whyte ebike was too low so I changed to the second gen linkage to raise it 12mm. Made a big difference. My Sentinel is also really low and I’ve recently fitted 155 Hope cranks to help pedalling on techy climbs.

Argh … 71 deg head angles indeed. And the move to steep from slack seat angles. I argued for steeper seat angles for years - and did my best with long top tube bikes (first gen Marin Team etc) with in line posts and saddles slammed forward on the rails - but I was madly into climbing. I was not even slightly on head tube angle but certainly ran very short stems in a naive attempt to get the front end right. God it was great when boutique and then-small fabricators slackened head angles; and SBG from Transition came along (and it’s amusing that they lied about the head angle - they said 85 but it was really around 83)…

Interesting that you raised the Whyte. I‘ve found my Sentinel OK - in Wales etc - even with quite a bit of sag dialled in - running 170 XT M8000 - but I am an early adopter of short cranks (but only to 165) and may like you start dabbling with 155.

By riding trends, I remember that we were all about natural trails and ‘leave no trace‘ in the 1980s and 90s…and that meant lots of rooty and rocky climbs, over fallen trees etc - in many case more like tech trial riding than anything else.…not sweeping singletrack and prepared DH runs. Long, low and slack makes huge sense if you are barrelling at warp speed down a prepared trail, with prepared table tops etc.

 

[2manyoranges]

So we’re 71 degree head tube angles

I think we’ve hit (literally) the limit of low bb’s and will see a creep back. My Whyte ebike was too low so I changed to the second gen linkage to raise it 12mm. Made a big difference. My Sentinel is also really low and I’ve recently fitted 155 Hope cranks to help pedalling on techy climbs.

Sorry more…

This indeed is L O O O O W W W W …. Almost as if the tubes have sagged…. Low enough? OR too low?

 

[coomber]

I have a squatch. Taken a little to get to grips with low bb and switched to 165 cranks, but I love it

 

[2manyoranges]

Glad the 165s are working out - like you I love mine

Now ….

155s?

 

[coomber]

If they weren't so pricey I would!