Most BB heights from the ground seem to be around 12-13' please correct me if I am wrong here.

Does it make any noticable difference the lower you go?

Say, for example, going from a HT with a BB height of say 13', to the same setup but with a BB height of 12', apart from the increased chances of a pedal strike the lower you go, what other differences would you start notice?

how low can you go?

Does that make any sence? I think I need a Coffee 😉

Lower BB gives a more stable bike as your overall weight is lower. Good for railing those turns!

You could have a low BB bike with a shortish wheelbase that would feel as stable as a longer wheelbase bike with a higher BB. It's all in the mix.

^^ is correct. I think it gets a bit odd when you start looking at bikes with lots of travel as you would think the bottom bracket should be high to prevent you bouncing the cranks when at the ends of the travel… but how often are you pedalling when bouncing off the stops… not a lot.

Higher bottom brackets make bikes feel more nervous in rock gardens and steep descents where lower is better, but if lower watch out for those pedal to rock/stump events. Tyres and suspension set up can also make a difference – and manufacturer listing are as reliable as on old MG Metro.

I guess it also depends on which fork you decide to run as well.

So how low can you go?

So how low can you go?

That really all depends on the application. I think the latest Specialized Demo 8 has a BB height of around 13.5" with over 8" of travel. To put it into perspective, that's not much higher than an Orange Five with just under 6" of travel.

Had Marins for years with really high (13"+) BBs, loved them.
Struggling with lower stuff, especially my HT, due to pedals hitting roots, rocks, etc, and no noticable increase in stability from lower centre of gravity.

That really all depends on the application.

Was thinking for HT use geetee1972, something to give me more confidence on decents, nothing too wild trail wise.

Been using a HT and mine runs at roughly 13' seated, but had a go on a Dale HT, sorry don't know which one it was, but the BB felt noticably lower, should have asked him which frame it was, are well 😉

It is quite hard to talk accurately about because so many of the measurements quoted are acieved in different ways. Some quote static, some sagged, some measure the drop btween the axle centre line and the BB centre line others measure literally how high off the ground the BB is.

As a reference point, Ragley are saying their frames with a 2.5" tyre and 140mm fork sagged by 40mm will have a BB that is 12.4@" off the ground, so what maybe around 12.75" static?

In contrast, DMR are quoting their Trailstar LT as having a 11.8" BB but it's not clear whether that is with a 130mm fork, sagged, or whatever. Sort of makes their quote a bit pointless.

Point is that a lower BB will make the bike feel more stable and lower your centre of gravity. I like my bikes to have a low BB for this reason and I always end up running shorter cranks to compensate.

I always end up running shorter cranks to compensate.

Even though shorter cranks raise your COG?

Even though shorter cranks raise your COG?

It would only be at top and bottom pedal stroke, where your weight on the bottom pedal is higher, but when you are going over obstacles or jumping pedals are normally level. I guess it kind of ruins the cornering advantages (if you lower your outside pedal) I wonder if the bb height has any effect on pedaling?

Even though shorter cranks raise your COG?

Brant that's an excellent point; you spotted the deliberate mistake 😳
I've never actually thought about it like that before so certainly appreciate the insight. For reference I was citing the Ragley because more than any other manufacturer I'v come across, Ragley is making the effort to be clear and transparent with it’s numbers. Plus they ride superbly well.