- BB heights – how important?
Since I last bought a bike (full suss trail) bottom bracket heights seem to have got lower and lower and around 335 mm now seems the norm for a 5″ trail bike. I can see the sense in this as lower mass of rider has to be a good thing as long as pedal clearance is still acceptable. Also coming from a bike with a sky high BB, I really do not want to go there again.
So my question is this. Is the difference between a 335 and 350 mm BB likely to be a deal breaker for you? – not pedalling huge rock gardens so pedal clearance will not be a big issue. I’m asking because one of the bikes I was seriously considering (Trek Remedy 29) happens to have a 350 mm BB compared to everything else I’ve looked at with 335 mm for the same travel. Reviews do tend to comment on the Remedy’s high BB, but otherwise it appears to be a great all round trail bike at a reasonable price (£4K RRP for the 9.8). Interestingly Trek have lowered the 650b version down to 338 mm, which suggest they might have **** up with the 29.
Thoughts on this please as I’d kind of written the Trek off on this basis and perhaps I shouldn’t have?Posted 5 years agojonathanMember
It’s a very tricky thing to compare, particularly across wheel sizes. Also you need to factor in how the bike moves through it’s suspension sag, and how much BB drop that generates.
It’s interesting to see that Scott drop the BB lower the larger the wheel size. Of course it’s never easy to tell if this is all planned, or marketing guff just to put a spin on the fact that they’re 29er and 27.5 frames ended up different shapes 😉
Personally I’m in the-lower-the-better camp these days. I’ll put up with the occasional pedal strike for ripping through corners better. You really got to ride them to be sure, and then trust your feelings when you do.Posted 5 years agochiefgrooveguruMember
It’s complicated. The greater the BB drop, the greater the stability but the more the flickability is reduced – so a higher BB will be better at quick slalom turns whilst a lower BB will be better at carving long flat corners. Also, it depends on what % sag suits the bike best, and how the bike’s anti-squat holds the bike up and how the damping does likewise.
Also, the BB height depends on what tyres you run and what nominal diameter was used in the geometry charts, so I find BB drop a much more useful measurement. My Spitfire is 346mm BB height (12mm BB drop) in the neutral setting which is 306mm with sag. I’ve tried it in the lower setting and it’s great on steeper/faster/more open trails but you can’t pedal as early out of corners so you end up slower and quick left-right-left-corners are harder with the lower BB and resulting slacker angles.
As with all things, there is no ideal and ‘medium’ is often best despite it not sounding as exciting as ‘super slack’ or ‘ultra low’ or ‘super stiff’ etc…Posted 5 years ago
True not easy to compare, but the Remedy is the odd one out compared against rival 29ers and is supposed to ride high in its travel with the dual chamber shock. Have to say it puts me right off this bike. Why would they run it so much higher than their 650b version unless it was just a compromise on frames e.g. common front triangle.Posted 5 years ago
The greater the BB drop, the greater the stability but the more the flickability is reduced – so a higher BB will be better at quick slalom turns whilst a lower BB will be better at carving long flat corners.
Good point, I hadn’t thought of that and could explain why Trek chose a higher BB for their 29er – presuming it was a genuine choice and not simply a cost saving compromise. Maybe they thought the 29er was inherently stable enough to cope with a higher BB? But their rivals seem to have gone down the lower route.
Forgot to mention I’m quite tall at 6’1″ with long legs, so I’m quite conscious of seat height. Dropper posts help massively, but would like a reasonably low pedalling position if possiblePosted 5 years agoroverpigSubscriber
Higher BB also makes it easier to loft the front wheel up (playful seems to be the preferred term). As always there is no right answer. The current trend is for bikes that are super stable at speed in a straight line, so you can just let go of the brakes and smash through stuff to get that all important Strava time. But if you like to hop around, bouncing off stuff and changing lines for the hell of it then a higher BB (particularly on a 29er, where the axles are higher) may suit you better. Anyway, 350mm (unsagged) is hardly extreme.Posted 5 years ago
mmm…. maybe in that case the Trek should really stay on my shortlist, but the Spesh Camber is still winning the battle on paper, closely followed by the Stumpy FSR. Just wish I could actually demo any of these bikes, or even just sit on one in a shop! When I went to my LBS during the week they had virally nothing sat in the showroom apart from a 2014 Spesh Camber in my size that they had just sold FFS!Posted 5 years ago
A low BB can be crippling, until I put shorter cranks and thinner pedals on my Rocky it was a pain trying to ride twisty singletrack.
Yes, that’s something I haven’t had to worry about at all with my current bike with the BB up at 380 mm! It does feel very high, so I suppose 350 mm would feel positively low anyway in comparison. Maybe I’ll encounter new problems with a 335 mm BB?Posted 5 years agoricky1Member
Took me a while to get used yo mine,but now I find my pedaling suffers as I’m always paranoid for the pedal strike,I try not to run to much sag iff I’m just doing normal trails,you sort of adapt to it but now inm going yo get some shorter cranks and get some new forks with slightly more travel,on the other hand the bike corners really well which is a good plus.Posted 5 years agodocrobsterMember
That Scott link doesn’t say that the bb gets lower as the wheel size gets greater, just that the bb drop gets greater, which you’d expect as the axles are higher on bigger wheels.Posted 5 years ago
The bb height can be exactly the same on 3 different wheel sized bikes with different bb drops. 26 bikes may have bb above the axles wheras on 29 it would be below the axles but same height off the ground.
Easy to get confused.
Anyway, sticking with 26 FS bikes I’ve gone from 365 usnagged, to 350 on same bike with offset bushes, to 335 on a different frame. The lower bb frame seems to corner better and be more stable going down as expected but there are more pedal strikes. Shorter cranks may be in order.
JCL – there are still a few 2014 spec Cambers available in the UK, but no realistic chance of a demo. I would probably go 2015 spec anyway to get the XT brakes and the new Roval fattie wheels. Discounts on 2014 spec are not quite enough to tempt me. Obviously I could swap out the brakes, but that would eat into a fair bit of the discount. There are however more 2014 Stumpys kicking around if I went that route and discounted slightly more. Very tempted to bite the bullet on one of those actually, but still debating other alternatives such as the Trek Remedy. I thought I’d ruled the Trek out on its higher BB height, but this thread has certainly made me think twice!Posted 5 years ago
[PERSONAL OPINION]There are a lot of numbers thrown around these days, in isolation they are meaningless, even in combination they can be misleading. There is only one way to see how all those numbers stack up on a bike and that is to get on it and ride it.[/PERSONAL OPINION]Posted 5 years agoTom_W1987Member
I prefer bikes that I feel sat in as I tend to muscle bikes around and corner with my feet flat when I can, high BB’s make things feel to skittish.
This whole “you can’t tell how a bike rides by it’s numbers” is a half truth, If you’ve ridden dozens of bikes over 20 years you start to get an idea of what works for you and what doesn’t.
Took me a while to get used yo mine,but now I find my pedaling suffers as I’m always paranoid for the pedal strike,I try not to run to much sag iff I’m just doing normal trails,you sort of adapt to it but now inm going yo get some shorter cranks and get some new forks with slightly more travel,on the other hand the bike corners really well which is a good plus.
Pedal less, pump more. If you’re pedal striking you’re doing it wrong. 😉 Keep sag at normal levels. The top downhillers don’t pedal as much as the rest of us, watch out in regards to adding more travel to the front as it may mess up the handling. 180mm Totems completely ruined my SX Trail for example.Posted 5 years ago
yes it’s a start but there are a bunch that I have ridden that have surprised me, the internet opinion which dismisses bikes because of a 1 degree head angle different to current fashion or stays 5mm shorter than a certain number is one of those things that people should avoid until ridden.Posted 5 years ago
Classic example was somebody commenting on a bike that had an op paper steep HA, when ridden the feeling was described as slack and felt slacker than other bikes with slacker on paper HA’s.Tom_W1987Member
Mike, that’s where sag comes into play. Head angles aren’t static, they are dynamic so it’s influenced by your shock/fork sag ratio. That’s ride a quick ride doesn’t tell you the full story either.
I have a base setup and feel that I like, my guesses are usually fairly close. I can for example, easily imagine what a high bottom bracket and short top tube/wheelbase feel like. But I find head angles harder to judge, as you have mentioned as well. I’ve tried offset bushings in my old mans Nomad for example, they did make a difference but it was reasonably small.Posted 5 years ago
Mike, that’s where sag comes into play. Head angles aren’t static, they are dynamic so it’s influenced by your shock/fork sag ratio.
Wow that’s where I’ve been going wrong all these years….
FWIW I’ve ridden more bikes than I can remember, tried most of suspension designs out there and I know I have a good idea of what I like and what works but the overall package is something I like to check out properly with an actual demo with the bike set up and ridden over some varied terrain. If a manufacturer isn’t willing to put a bike up for test it’s off my list.Posted 5 years ago
There is only one way to see how all those numbers stack up on a bike and that is to get on it and ride it
I agree, but unfortunately it’s not really an option at this time of year. The demo bikes are simply not available so I’m having to rely on reviews, geometry analysis and of course forums! I think you can get some good insight from studying the geometry providing you look at it as a whole and can relate it to your own experience. I know for sure I don’t want a really high BB like my current bike, but I haven’t got any personal experience of running a very low BB, so it’s good to hear about the potential pros and cons. This thread has certainly made me more aware of the potential cons of a fashionably low BB.
I think it’s also quite useful to be clued up on a bike before you eventually take a test ride so you know what things to look out for during the ride.Posted 5 years ago
One thing on sizing (just read your other post) is to keep an eye out while you are riding, you could well see one especially at a busy trail centre car park.
If you are near BPW you can play all day on the RemedyPosted 5 years ago
Mike – great idea to rent one for the day (could also try the Fuel that way too to get an idea if I would be happy on a shorter travel bike). Only issue is that the alloy Remedy has a completely different sizing to the Carbon one. You couldn’t make it up could you?!Posted 5 years agosmatkins1Member
Just out of interest I dropped the air out of my shocks last week to see how close my cranks got to the ground at full travel.
I don’t even think I’ve got a particularly low bb to start off with so some of you on your modern low slung slack +150mm travel enduro machines must be creating sparks with your chainrings over the rough stuff!Posted 5 years ago
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