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Discussion Starter · #1 ·
It seems that BB height trends dictate that a lower bottom bracket is ideal. But my 5.5"-travel trailbike's 13.2 inches BB height seems to be too low for me because I keep on hitting my pedals. But I'm building another bike (old 6"-travel frame) which has 14.5 inches of BB height. I'm anticipating that there is quite a huge difference. Will it be drastic? How would it feel? Or is it just a matter of getting used to?

Whadya say? What could be an ideal BB height for the current AM bikes that are supposed to be the best balance of various compromises?
 

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mbtr member
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bb height is so user and terrain specific that it's hard to take one person's experiences and apply that to yourself. Sure, a low bb height is really nice when you coast through the rough and there isn't much rough to slog through, but if you're a pedaller, run flats, and have rough trails, a higher bb is going to serve you better.

For my part, my long travel hardtail has an 11.5 inch bb height before sag, which is super super super fkn low, and it's awesome 80% of the time. When it sucks it's super obvious,and whether you're willing to tolerate it depends on you and your trails.

A small change in bb height is pretty obvious to the rider, but what works out to be the best compromise is a pretty user-specific deal. Sorry i don't have a number that is the best, but this is totally a riding-style speciic number.
 

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on my 3rd wind...
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It does to me but depends on bike travel.
I prefer 13.0"-13.5" for 4" FS bike. Inch lower on HT.
For 13.5-13.75" for 5"-5.5" FS bike.
And 13.75"-14.0" for 6" FS bike.

13.2" to 14.5" BB height will be a huge difference. Less pedal smash on rocks but you won't corner as well and will feel little tipsy during slow technical moves.
 

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noMAD man
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BB height is always an interesting discussion. scott is so correct about some of this being preferential. I absolutely hate serious pedal smack, and some bikes have it in spades...others don't. There are so many factors. On the handling issue with some tall bikes and many riders, there is often a problem with a decently tall BB. I had an '03 Bullit with a very tall BB...forget the number at this point...but I had installed a longer shock and fork. Though it didn't quite carve like my Nomad, I had no problem with fast cornering. I've ridden some other tall BB bikes and didn't have much cornering issue with them either.

I got to thinking that perhaps it was because I was used to riding very tall long travel dirt motors. While not a 100% comparison, you have to be very conscious of where the CG of the dirt motor is when you lean it into a corner aggressively. The height of the bike is less of an issue when you have the CG planted directly over the tires and into the bike's footprint...if you get my drift. I basically do the same thing with my mountainbikes, right or wrong. I think lots of people are more into steering and remaining as upright as possible. Of course you have to lean to some degree regardless of skill or fear factor, but leaning into the corner right at the point of the bike's CG and tire contact point being in line diminishes the impact of the BB height. It's a little bit of balancing act, and it can bite you once in awhile, but you can get used to it.

Funny thing...that Bullit didn't pedal all that efficiently, but you could pedal that sucker through some pretty nasty rock gardens without pedal smack. On the last trip to Moab with a riding buddy, his frame broke on his Spec Enduro the second day out on a 10-day trip. I bring the Bullit as a backup bike, and even with a 170mm single crown fork and the OEM sized 8.5 X 2.5 shock, the Bullit is known for a tall BB. My buddy rode that bike the rest of the trip, noticed the serious lack of pedal smack in many of the technical, rocky trails there, and absolutely loved it. As already stated...people are different.
 

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wuss
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titaniumgearsolid said:
It seems that BB height trends dictate that a lower bottom bracket is ideal. But my 5.5"-travel trailbike's 13.2 inches BB height seems to be too low for me because I keep on hitting my pedals. But I'm building another bike (old 6"-travel frame) which has 14.5 inches of BB height. I'm anticipating that there is quite a huge difference. Will it be drastic? How would it feel? Or is it just a matter of getting used to?

Whadya say? What could be an ideal BB height for the current AM bikes that are supposed to be the best balance of various compromises?
Don't take anyones word regarding BB height too seriously unless you know they are riding similar trails. The lower ones will feel better when carving along, but if your trails are very rocky you'll just end up banging your pedals all the time and losing your flow.

My trails are very rocky, and low bikes just don't work very well here. Luckily I have adjustable drop outs (which I generally have to keep on their highest setting for most trails around here). However I've been riding some places where the trails are smooth enough that banging pedals would never be an issue, there the lower BB would work great.

You can learn to smack pedals less, but it's not just about skill.

Also, when you look at the listed BB heights remember that it's an unsagged value. My previous bike had a higher BB on paper, but the increased travel and the way the suspension is set up results in the new one having a lower BB when sagged and with compressed suspension. I don't think the different drop out settings on my bike make more then a 3-5mm differnce in BB height, but it feels like a huge difference on the trail.
 

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Discussion Starter · #6 ·
Thanks for the responses so far.:thumbsup:

I did some back-reading on my old MTB magazines, and I noticed that my 2005 6"-travel frame's "batchmates" had pretty much the same lofty BBs. Mine is a 2005 Giant Reign and the others from the same magazine article were a Cannondale Prophet, Gary Fisher Cake, Kona Dawg and Marin Quad TARA. All their BB heights hovered at around 14 inches, considering most of them were 5"-travel trailbikes. I guess that was the trend during that time, to have that much ground clearance on their BBs.

So, now I'm thinking that if ever the Reign's BB feels a tad too high, I could just try compensating by dialling more suspension sag. Which leads me to this question: how much sag is too much? (Just for a point of reference, I've always found 28-29% of sag on my 5.5"-travel DW-Link bike to be its sweet spot.)
 

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wuss
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Suspension design can affect how much sag you should have (and usually does). Also the shock you have can make a difference on what works. If you have something that blows through it's travel easily (RP23 with too low compression tune or high volume casing for example) increasing sag could result in quite compromised suspension performance.

But it's definitely something worth trying. I used to have an air cartridge in my fork and switched to coil. It travels far higher in travel resulting in a higher BB. This will probably allow me to use one step slacker setting my my drop outs keeping the BB at the same height as before (it's winter now so hard to judge, snow evens out all the rocks). On the opposite note I tested having a softer spring on my shock last autumn and it caused me to bash my pedals quite a bit more.
 

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meow meow
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i look a tt length, ha, and sa before i check bb height. to me it is not a huge deal, i assume, maybe naively, that the bike manufactor will get it right. it has never detered me from buying a bike.
 

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www.derbyrims.com
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titaniumgearsolid said:
It seems that BB height trends dictate that a lower bottom bracket is ideal. But my 5.5"-travel trailbike's 13.2 inches BB height seems to be too low for me because I keep on hitting my pedals. But I'm building another bike (old 6"-travel frame) which has 14.5 inches of BB height. I'm anticipating that there is quite a huge difference. Will it be drastic? How would it feel? Or is it just a matter of getting used to?

Whadya say? What could be an ideal BB height for the current AM bikes that are supposed to be the best balance of various compromises?
Going to a 1.3 inch higher BB before sag with hardly any more travel is a huge difference. Some of the change in handling and balance can be reduced by using much deeper sag, softer springs, and tune a little firmer damping to prevent too much wallow from the higher weight center and softer suspension.

There is no ideal BB height. Rock crawlers like higher BB for pedaling clearance to avoid dangerous pedal strikes. Downhill riders with mostly smooth climbing prefer lower BB where pedal clearance is a rare problem. Longer travel bikes with softer suspension need higher BB to maintain some pedal clearance when sagged and compressed further in turns and while pedaling through bumps.
 

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noMAD man
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I don't think I'd put a lot of sag into the Reign to achieve a lower BB. Most bikes get mushy and harder to handle in many types of terrain. Even with carefully tuned compression and rebound, excessive sag usually has more negatives than positives in the resulting ride. Some examples are where the sagged bike tries to stop in slower, technical terrain...the geometry and feel of the bike changes in hard cornering at just the wrong point...and pedaling efficiency is almost always affected negatively. It's not a good bandaid. As dropadrop suggested, strictly going by BB numbers is not the whole picture.
 

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noMAD man
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PissedOffCil said:
If your pedals hit the ground or rocks, then some work on your technique is required. If your BB hits the ground or rocks, then a higher BB is the solution.
I don't know about that statement. I don't think there's one blanket that can be thrown over this whole issue. There's some truth there in many situations, but it's not absolute depending on terrain and the bike...even a bike in perfect setup. The myriad of bike designs and suspension designs alone just about make that impossible.
 

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The Punk Hucker
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TNC said:
I don't know about that statement. I don't think there's one blanket that can be thrown over this whole issue. There's some truth there in many situations, but it's not absolute depending on terrain and the bike...even a bike in perfect setup. The myriad of bike designs and suspension designs alone just about make that impossible.
Yes, it's to be taken lightly. My point was that everybody talks about pedals hitting the ground, yet you have control over that in many cases. It can be annoying, I agree, but it's something to keep in mind.
 

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Ratcheting won't get you there all the time. A lot of times you just can't get enough power to get over some big rocks without at least full revolution. It's also dependent to some degree on your rear hub engagement. There's one super rocky trail I hit my pedals at least 5-6 times per ride. The more I focus on avoiding pedal strikes, the more problems I have with not cleaning sections I've cleaned successfully before.
 

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As people have said, it's a ton of personal preference. I ride a ton of rocky stuff and yet prefer a low BB for handling traits. I don't mind having an occasional pedal strike and have gotten quite good at timing pedaling to avoid them.

FWIW the two bikes I ride the most are a 5/6" FS AM bike with a 13" static BB height and an 8" FS DH bike with a 12.9" static BB.
 

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Biking Like Crazy!
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adjustible seatpostto lower CG

Don't worry too much about the BB height as per these posts!
Put an adjustible seatpost on your bike and lower your CG by alot when needed.
I'm rocking a 14.65 in. BB with a 4in drop seatpost! No problem what so ever!:thumbsup:
 

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I have ridden FS bikes anywhere from 13" to 15". As mentioned very terrain specific. Some of my worst pedal smackers were 5" trail bikes equipped w/ air shocks - they just ate travel making the pedals magnetize to the ground. Anytime I went into rocks I felt like I was driving a lowered car approaching a speed bump.
 

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Riiiiiide...
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Hardtails Are Better said:
8" FS DH bike with a 12.9" static BB.
Holy cripes!! You probably can't even pedal that thing out of turns :eekster:
On my 7" bike with a 14.1" BB and 36% sag i reeeally have to be careful.

I can now see the future of DH. Bike parks with tracks that require no pedaling.. hence bikes with no drivetrain and uber low BB's.
 

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PsyCro said:
Holy cripes!! You probably can't even pedal that thing out of turns :eekster:
On my 7" bike with 36% sag i reeeally have to be careful.

I can now see the future of DH. Bike parks with tracks that require no pedaling.. hence bikes with no drivetrain and uber low BB's.
You'd be surprised. I've learned to ride it, and it works pretty damn well. Is it too low? Honestly, yes. Is it a lot to low? Nope.
 
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