Every time I start thinking about what is the best bike geometry, I remember that people can and do ride unicycles for XC and DH.
Could it be that it doesn't matter what the geometry is, and that we adapt to whatever is the current fashion used by the racing teams?
Yep.
Could it be that it doesn't matter what the geometry is, and that we adapt to whatever is the current fashion used by the racing teams?
Someone with the skills can get down anything on pretty much any MTB. See Yohann Barrel riding a cross bike down whistlers black runs.
I like how my bikes ride, would something else be faster? Probably. I just ride for fun. My cove stiffee was super slack for the time (70 degree head angle). My g13 was slack at the time (64 degree head angle).
£1000 on skills coaching would make more difference down hill than any bike.
Losing 10kg off my belly would make more of difference up hill.
I'm with Eddy Merrex. I need to ride up grades, not buy upgrades.
It was an interesting article. I also loved the grim donut series on pink bike. I did wonder why they didn't try and sell 10/50 or 100 of them. Someone made some with similar geometry, I don't think I've ever seen a photo of one built up.
Agree 100% about XL head tubes, non of them are long enough and leave me with a saddle miles higher than the bars. Only option is a stupid amount of spacers or a stupidly high bar, both of which are aesthetically sub optimal.
I assume it's because very long head tubes don't look pretty, much like XL bikes with 26" wheels?
Every time I start thinking about what is the best bike geometry, I remember that people can and do ride unicycles for XC and DH.
Slowly and with much greater difficulty.
Could it be that it doesn't matter what the geometry is, and that we adapt to whatever is the current fashion used by the racing teams?
That was what happened in the late ‘80s - XC dominated and MTBs changed shape to be better uphill which made them worse downhill. Then freeride got a bit carried away and BBs went sky high. Eventually things starting heading back towards klunkers and then on toward motocross geometry but adjusted so pedalling works too.
As Benji said, it’s pretty sorted now, just needs to scale better for sizes.
A Professional with advanced skills can get down anything on pretty much any bike.
FTFY
What geometry for robot ai?
I would like taller front ends. I would also like lighter bikes for short travel duties. It’s getting a bit ridiculous imho that short travel bikes seem to be built to dh strength and therefore weights.
I kind of think it’s gone too far. I’ve got a ‘trail’ bike. 140/130. Bought for the geometry for my southern forest riding, would prefer a bit more travel for the occasional big hit, but that doesn’t seem to exist.
High rise bars look awesome.
to what limit? A little bend looks better than flat (IMO). But some of the high rise things these days look ridiculous. If that’s where you want your bars then so be it, no argument for physiology.
But that’s a glaring condemnation on the bike brands for not making a bike that fits taller people.
High rise bars are generally better than a long head tube. A long head tube, just like lots if spacers, moves the bars further and further backwards. You end up losing reach, having a super long front-centre to compensate, and having less weight on the front axle.
I've just bought 50mm risers for my new bike before I've even got it cos I know the stack isn't going to be high enough. I have the mountain bikers curse of long legs/short torso
It's a Specialized and their 'S' sizing is reach based rather than increasing seat tube and head tube as well as length. As another consequence I'm going to have an unsightly amount of the 170mm AXS dropper showing above the collar
I've gone for an S4 which is technically a large as that's what I normally have and a reach of around 480mm seems to suit me - I've only found this out recently, as my old Kenevo felt too short in the front and the Ragley I built up last year feels great. But the Ragley has a fairly high stack
It (Specialized sizing) might work, I'll find out shortly....
@eddd - other way round. If your headtube is long so that you don’t need to artificially raise the bars either with spacers or tall bars, you achieve close to the frame’s reach figure.
Adding spacers or running tall bars on a shorter headtubed frame reduces the effective reach. Tall bars and spacers do the same thing unless you roll the bars forward which also effectively lengthens the stem , so has other handing effects.
So here we are talking about bike geometry! Is the the same as roadies constantly discussing gears?
Just go out and ride the bike.
@Sillyoldman to get to that given reach figure, a longer head tube needs a longer front-centre. Like spacers, the tube goes up and back, not just up.
I need reach but like a short front centre, so I really like S sizing. I slam my stem and use high rise bars.
@eddd Any quoted teach figure is measured from the top of the headtube, so a tall headtube without a stack of spacers and/or tall bars accurately reflects the each figure achieved. If you need to move the bars up from a low headtube, you’re shortening the reach vs what’s quoted. Front centre is a combination of other additional metrics.
I’m firmly of the opinion that geometry trumps all.
Here here. It's taken me long enough but I'm firmly a geometry geek/bore.
Yes, there is the Geometron G1 but that’s arguably stepping out of most folks’ trail bike remit due to its 175mm of travel (personally I’d be fine with a G1 as a trail bike but that’s a story for another time).
There's also Nicolai's shorter-travel bikes such as the 130mm-travel Saturn 14 that are very much from the same geometry school of thought. 14.5kg inc pedals on a sensible build and nearly 3kg lighter than my G1. Not so subtle advert, there's a XL one of those for sale at the moment.
As well as my XL G1 I've discovered that (some) current XXL Santa Cruz bikes fit me well despite being well below the recommended height chart at 'only' 187cm. XXL Tallboy with a 518mm reach, 155mm HT and 41mm BB drop. Chainstays are 446mm and I think I'd like them to be longer, but that's better than others I looked at and are on par with the Saturn 14 above. Would be nice if the ST was shorter but I've still squeezed a 210mm OneUp on there so I guess it's short enough.
It is a good article, I enjoyed it a lot Benji.
I like what I like, but it’s always interesting to see what others prefer. And then people like Bryceland who is (6 foot?) and rides a medium, very fast for all he does (and not just tricks in the woods)
Being able to alter bar height using different rise bars means multiple bar heights are possible without effecting reach. More riders and their bar height preferences can be accommodated without compromising the handling for anyone. Of course headtube can be too short on larger sizes... plenty of examples of that out there (especially in the carbon world)... but super long headtubes bring their own compromises and limitations.
If we adjust bar height we're either shortening reach or effectively lengthening the stem but imho that doesn't matter too much, not a problem within the normal range of adjustments. What's more important in a bike is that the front centre and rear centre are balanced, as Benji's getting at with variable CS length. Most of the time most of your weight is through the BB so if FC and RC are balanced for you then I'm not sure the exact reach figure really matters? e.g. I might like a longer reach on a bike that has a longer rear end, but if the bike has a short rear and proportionately short front / reach too it might also feel good (just in different places or for different riding).
Look to Geometron for well sorted geometry. Chris Porter’s geo has trickled out worldwide to other manufacturers since the first ones in 2015.
my Kenevo SL is very very close to my “longest” 2015 Geometron G1.
I'm making my own frames with geometry that a magazine journalist says doesn't work - so I must be doing something right 😀
One thing that is curiously never mentioned - it is generally easier (and therefore cheaper) to design and make tubular metal frames with with long chainstays and straight (hence steep angled) seat tubes.
But that’s a glaring condemnation on the bike brands for not making a bike that fits taller people.
And if they raised the headtubes people would complain they lacked stand-over clearance.
There's no benefit to long headtubes beyond making them long enough that the headtube, steerer, spacers, stem and bar combination is adequately stiff.
Reach is reduced by raising the bars (whether by stem, spacers or bars as long as you keep the grips to steerer relationship constant) but if the frames reach is 20mm longer on a given size, then for a constant bar height the actual reach is still >20mm longer if there's any extra headtube at all.
Not on an XC bike they don't.
Only because slamming the stem and flat bars is fashionable. A 250mm headtube would look equally fugly. We'd all end up riding bikes like Emily Batty.
If you want a 'perfect' fitting bike with flat bars, flat stem, no spacers, it'd have to be a custom build for you otherwise geometry needs to be literally be the lowest common denominator so that the most people possible can then pick anything from a flat bar to +80mm rise.
Reach is reduced by raising the bars (whether by stem, spacers or bars as long as you keep the grips to steerer relationship constant) but if the frames reach is 20mm longer on a given size, then for a constant bar height the actual reach is still >20mm longer if there's any extra headtube at all.
Correct, but the reduction in reach from fitting a higher rise bar is much less than the reduction from adding spacers under the stem. I'd much rather have a longer HT if it means I achieve/maintain my desired stack without faffing around with spacers (and losing reach) or very high rise bars. Doesn't mean all frame sizes need to have longer HTs but increased proportionality for XL frames would help IMO.
There's a few Deviates among the folk I ride with and I'm really not a fan of the short HTs their designer favours: 121mm on a XL, and that's an integrated headset too so not height gained from that. Just looks out of place on a XL frame.
Even on my XL G1 with 140mm HT I have 15mm of spacers under the stem and a 40mm rise bar and am still tempted to try higher rise bar. I'm not even that much of an outlier in height at 187cm. It's be harder to achieve the same position with a shorter HT such as the above-mentioned Deviate.
”but the reduction in reach from fitting a higher rise bar is much less than the reduction from adding spacers under the stem”
Only if you accept the steering feel changing. You can’t raise the grips on any bike without reducing the reach - the stack and reach are firmly linked by the head angle.
but the reduction in reach from fitting a higher rise bar is much less than the reduction from adding spacers under the stem.
That is dependent on the shape of the bars though and how you rotate them.
In your example you're effectively lengthening the offset between the bars and the steerer tube (like running spacers + longer stem and flat bar).
For most people they would want to keep that constant, either by picking bars where the rise was added inline with the steerer rather than by bending them forwards, or by then running an even shorter stem,
I'd much rather have a longer HT if it means I achieve/maintain my desired stack without faffing around with spacers (and losing reach)
You would, someone who likes a low front end wouldn't. And the frame needs to fit both.
And you're not 'losing reach', as we've already agreed, if the grips are ~300mm above the fork crown on a Large, and the XL has 20mm longer reach, the bars are still 20mm further forward.
You only get less than the advertised reach increase if you do something nonsensical like compare two sizes with the same number of spacers and different HT lengths. If you compare two sizes with the same steerer tube length (but the larger one has any extra HT at all) then the reach increase will always be MORE than the advertised value.
If you want a taller headtube and more reach than an XL, then the solution isn't to increase reach and stack but keep calling it XL, it's buy an XXL surely?
There's a few Deviates among the folk I ride with and I'm really not a fan of the short HTs their designer favours:
But presumably he's made a few sales to people who want their bars ~140mm above the fork crown that would otherwise not have happened as you can add rise but can't take it away (in an aesthetically pleasing, not going to crack your top tube in a crash with the stem way).
I'm in a similar boat as at 6ft but with short legs (31" jeans) I tend to end up riding either "Large" frames with quite an upright position and swept back bars (Stooge Moto bars FTW!), or for more 'efficient' riding either XC or Road I tend towards frames that fit bigger than stated (i.e. labeled 56 for the seatube but have reach figures more like a 58-59) which gives me more space to tuck my elbows in and get low. Which is a roundabout way of saying for me at least the longer the frame is the LOWER I want the front end because it gives me the room to tuck in without having to hunch.
I get that tall people (usually) want longer head tubes, but do you think bike companies don’t put them on because they make bikes look uglier? I’m not saying that this is a good reason to have shorter head tubes, but I have always thought that shorter ones look nicer.
Bike geometry has a way to go as it still isn’t taking into account basic principles. If you got a group of 10 men lined up, with each one 5cm taller than the other I guarantee the difference in torso lengths would be much smaller than the difference in leg lengths. Yet for some reason we still size bikes on total height. Most bike brands would recommend that a man who is 5ft 9” should ride a Medium frame and a man 5ft 11” a Large. The % difference in the reach of a Medium frame compared to the Large frame will be a larger % than the torso % difference of each man.
I agree that as a sizing metric a mtb’s reach is the most important. If we are to size bikes properly though we need to stop thinking about total height and base it on a combination of torso, arm length and flexibility.
"If you got a group of 10 men lined up, with each one 5cm taller than the other I guarantee the difference in torso lengths would be much smaller than the difference in leg lengths."
I have no idea what you're basing that statement on - I've never seen anything to suggest that is true. In fact the range of leg lengths on mens' trousers tends to suggest the opposite!
"If you got a group of 10 men lined up, with each one 5cm taller than the other I guarantee the difference in torso lengths would be much smaller than the difference in leg lengths."
I have no idea what you're basing that statement on - I've never seen anything to suggest that is true. In fact the range of leg lengths on mens' trousers tends to suggest the opposite!
Geometry change seems to be (rightly) settling down lately, it's getting pretty good. The biggest issue I still see now is there are brands giving effective seat tube angles that have little bearing on reality at saddle height. The difference between some bikes that should be the same angle is quite shocking.
I wouldn't necessarily object to a taller headtube, but it's got to be done in combination with the rest of the geometry. As a taller rider I've typically run low-ish bars. For one thing I've got long arms, so can reach down and still maintain the same general body position. But often I've been running lower bars to compensate for overly slack seat tubes. Which creates its own issues, like closing down the hip angle. A higher front end/stack isn't any good without a steeper seat tube. Otherwise it feels like I'm falling off the back. Front end/stack has gotten higher in recent years. Seat tubes often haven't gotten steeper by enough to overcome that shift in body position.
I think the next thing is probably going to be lower BBs matched to shorter cranks. Some people are doing this already but I reckon it'll become more mainsteam.
When you look at the more extreme older bikes, this is what really stands out- I just bought myself a 2016 geometron for a laugh, and what looked absolutely bananas in 2016 now frankly just looks pretty sensible, except that BB drop.
It’s just something I remember from Uni, basic anatomy. A quick google though brought this up
There will be more if you want to look.
Anecdotally though you can see it yourself. Go in a clothing shop that has trousers with a regular, short and long leg variant and measure the difference. Then measure the difference in length between a small, medium and large t-shirt. There will be both a bigger difference both in actual and % with trousers than t-shirts.
I guess a lot of this depends on what you want the bike for. I haven’t got a very modern progressive geometry bike but whenever I ride one I find the steep seat angles great for short distance trail riding… but as an old bit I wonder how long it would take me to adapt to all day, every day backpacking type riding.
“It’s just something I remember from Uni, basic anatomy. A quick google though brought this up”
The sample size in that paper is pretty small, and the lack of difference between ethnicity is at odds with another study I read. That study found a higher LBR for people of African heritage and a lower LBR for people of Northern European heritage (which makes sense for cold weather evolutionary adaptation).
Still using a Whyte T129, with various upgrades, just the frame now really. My only issue is rear wheel clearance for larger tyres. Geometry is just fine. I prefer to get and ride rather than stress over a degree here or there.
If you got a group of 10 men lined up, with each one 5cm taller than the other I guarantee the difference in torso lengths would be much smaller than the difference in leg lengths.
This is probably correct because leg length is affected by nutrition in pre-teen years as well as genetics, torso length will be genetics only. Greater wealth and thf better nutrition has meant that the average height in China has increased in the last 20-30 years and a lot of that will be leg length averages.
Then measure the difference in length between a small, medium and large t-shirt. There will be both a bigger difference both in actual and % with trousers than t-shirts.
We're more sensitive to half-mast trousers than t-shirt hem position? : )
I think the next thing is probably going to be lower BBs matched to shorter cranks.
Could be - already a driver of different size kid's bike design beacuse there's a lean angle test in ISO that gives a minimum, as with MTBs. But a low kid's bike saddle is good, a low MTB BB pins the bike down and makes getting the front up less easy so not always better? BB drop probably has an ideal for a ride feel aim as well as the need for pedal clearances.