There isn't a right and wrong. But, IMO, there is an acceptable range of BB Height that is narrower than one might think for each application of bicycle design (high performance road, touring, X/C, DH, etc). Too tall, and the bike feels tippy, dives into corners, loses drop-off stability. Too low, pedal strikes.cheepnis said:It seems to me that the 29er geometry should be able to eek out a little more BB height/ pedal clearance than a 26er. I may be wrong in general, but from the tiny bit of looking I've done it seems that 29er BB height is about the same as a 26er. Why's that?
... How wrong am I on this?
BB height on my rigid forked HT WaltWorks is 10.75-11.25" depending on tires. Took little or no time to adjust to it, don't hit a pedal more than once every 10 rides. Of course a lot depends on where you are riding. I can imagine hitting pedals riding through baby head rock gardens, but I'd usually be going up hill slowly, and a pedal strike there doesn't bother me. Going down through the same area I would have the pedals horizontal anyway. The benefit for me of a low center of gravity on fast downhill corners and less lofting of the front end on steep uphill steps is a good trade off for the occaisional pedal strike. Personal choice however, YMMV.I realized that I was able to rail corners on loose chunky gravel sickeningly fast, that could do drop-offs that seemed way over the top. It was fun. And, I could sit comfortably and grind along on long easy climbs, benefitting from the comfort and stability of a low BB.
So, I thought long and hard, and then asked my custom builder to tweak the design one more time, back down below 12", but not below 11.75". What I got now measures something like 11.8" or 11.85", and it's very much right. For ME. That's how I like to have it.
So, my opinion, big wheels or little wheels: get the lowest BB you can stand. But that's for an XC Hardtail. Not sure what my opinion is about BB height with a fully-suspended bike. I've never owned one.
And of course, YMMV.
It is the overall geometry that matters. The wheel size is not really much of a factor. With a longer wheelbase a higher BB may be necessary to maintain pedal on rough terrain.cheepnis said:won't a 12" BB height on a 26er feel more awkward than a 12" height on a 29er? Or does BB height have the same effect on both geometries? Without a study on the cycling mechanics of BB height it just seems like the BB could be raised a little bit without affecting the feel relative to a 26er. Wheelbase is longer, wheels are bigger, seems like an extra 1/2" or so of clearance would do no harm.
Of course everyone will have their own preference in general. But what I'm wondering is what increase in BB height can occur when moving from 26er to 29er before a real change of feel is noticed?
Below 12in, but not below 11.75in - ie: you're zooming in on something that's within a range of 6mm - you think you could tell the difference in 3mm either way - on BB height?team_bfd said:So, I thought long and hard, and then asked my custom builder to tweak the design one more time, back down below 12", but not below 11.75". What I got now measures something like 11.8" or 11.85", and it's very much right. For ME. That's how I like to have it.
My thoughts, too. Using a Klaw 29" tire vs a Spec Fast Trak 29" will change the BB height by ~6mm.[email protected] said:Below 12in, but not below 11.75in - ie: you're zooming in on something that's within a range of 6mm - you think you could tell the difference in 3mm either way - on BB height?
Oh my.
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And if we're sticking to fairy stories, this phenomena is what I call "Emperors new clothes" Syndrome, where you're trying to convince yourself that something you found a negative, is a positive.team_bfd said:But then a funny thing happened. I started having less trouble with pedal strike because I was being more careful and adapting to the bike. Then I realized how I was exploiting the low center of gravity. I realized that I was able to rail corners on loose chunky gravel sickeningly fast, that could do drop-offs that seemed way over the top. It was fun. And, I could sit comfortably and grind along on long easy climbs, benefitting from the comfort and stability of a low BB.
Oh my, what a jerk.[email protected] said:Below 12in, but not below 11.75in - ie: you're zooming in on something that's within a range of 6mm - you think you could tell the difference in 3mm either way - on BB height?
Oh my.
I was talking about BB height in the context of designing a custom. So, I was saying (to my builder), using a motoraptor rear and a jones ACX front, and a White BW.8 fork, I want my BB height to be right here (more than 11.75, less than 12).shiggy said:My thoughts, too. Using a Klaw 29" tire vs a Spec Fast Trak 29" will change the BB height by ~6mm.
Memphisrider- Put the chain int he big rig for crossing the big logs, even if it means having to cross-chain a bit. With the chain on the big rig it will slide right over the log instead of the chainring biting inMemphisrider said:I bash the heck out of my chain ring over logs that I normally clear with my 26.
I have to agree with you bfd... I notice small changes in my set up... millimeters. By their logic, you wouldn't notice the difference between a 175mm crank and 180, but they all claim that they need 180mm cranks...team_bfd said:Oh my, what a jerk.
I can feel a 5mm change in bar position, probably a 2mm change in seat height. Instantly. Why shouldn't I be sensitive to BB height?
I like a low BB. As I mentioned earlier, YMMV. (Maybe y'all should look up what that means)
What do you care anyway? I certainly wouldn't ever bother you for one of your shite bikes.
