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DH Bikes - Why is Reach so Short?

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DH Bikes - Why is Reach so Short?

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flag aerosxl
Posted: Nov 4, 2021 at 6:32 Quote
I'm currently looking at buying a DH bike to complement my trail bike for racing, park days, etc. However, I've noticed that a lot of the DH bikes I've looked at have much shorter reach than my trail bike. I swapped to my latest trail bike (XL - 500mm reach) in part because my previous frame (L - 475mm reach) felt too short on downhill trails. Of course this applies to the older, used bikes I've seen, but even a brand new Canyon Sender AL would be 20mm shorter. Given that I likely won't be able to test ride any of these bikes before buying, Is this reach difference vs a trail bike that noticeable? I'm sure they wouldn't be so much shorter if there wasn't a reason for it, but as a pretty tall guy who only recently discovered the joys of a properly sized bike, I don't want to be disappointed.
flag BenLow2019
Posted: Nov 4, 2021 at 6:51 Quote
Geo is totally different between trail and DH. When riding DH you rarely/almost never sit on the saddle. Riding DH you'll be up on your feet and your body will be keeping the weight distributed over the bike to keep control down the track. Very often you'll find your posterior will be above or behind the seat post. The reach feels right.
Trail bikes have you seated all the time so the geo is different.
flag Danzzz88
Posted: Nov 4, 2021 at 14:41 Quote
For numerous reasons, one reason, at least a few years ago, dh bikes were slacker than enduro, with longer forks and often longer chainstays so the wheelbase was already massive as it is, a longer reach would just make the wheelbase too long. Secondly as stated above, due to enduros needing to climb, a more forward weight shift via means of a steep seat angle was introduced to make up for the fact the bikes got longer and slacker to improve dh performance...some people swear by this modern geo, for me personally I am not 100% convinced, I ride an sb165 and although the geo feels nicer overall than my older sb6 I still prefer the geo of a dh bike. The shorter reach means you can be more upright and in less of a push up position over the bars, as the slack head angle, high stack, long wheelbase keep you in a safe position, additionally long chainstays help generate more front wheel traction by inducing a more forwards weight bias so it doesn't become as neccessary to hang over the front to generate grip creating a more comfortable, relaxed and arguably safer dh riding position. Ofc there is some exceptions to the rule, some enduros are super slack like dh bikes or have long chainstays, but you can guarantee those that have all those traits and a long reach will have stupidly long wheelbases and turn like a canal boat.
I also am not a fan of steep seat tubes, as in order to get full leg extension during pedalling you need to have your saddle pretty damn high up as you are more centred over the bb, this creates more hand pressure during casual riding, it's better for cornering grip while seated conpared to older geo bikes, but tbh if you are ripping corners fast, you don't do it sat down, you stand up and tilt the bike over, so what is kind of an advantage to the steep seat tube becomes a mute point in reality. But disregarding dh bikes for a minute, in general the newer bikes are better overall than the old enduros both climbing and descending, so they have moved in the right direction but maybe have took a slightly skewed path. Slack, with decent wheelbase, shorter reaches, longer stays for stability and front wheel grip and keeping the wheel down during climbing along with a slightly reduced seat tube angle I thing would be ideal, at least for me.
flag englertracing
O+
Posted: Nov 6, 2021 at 0:17 Quote
Danzzz88 wrote:
For numerous reasons, one reason, at least a few years ago, dh bikes were slacker than enduro, with longer forks and often longer chainstays so the wheelbase was already massive as it is, a longer reach would just make the wheelbase too long. Secondly as stated above, due to enduros needing to climb, a more forward weight shift via means of a steep seat angle was introduced to make up for the fact the bikes got longer and slacker to improve dh performance...some people swear by this modern geo, for me personally I am not 100% convinced, I ride an sb165 and although the geo feels nicer overall than my older sb6 I still prefer the geo of a dh bike. The shorter reach means you can be more upright and in less of a push up position over the bars, as the slack head angle, high stack, long wheelbase keep you in a safe position, additionally long chainstays help generate more front wheel traction by inducing a more forwards weight bias so it doesn't become as neccessary to hang over the front to generate grip creating a more comfortable, relaxed and arguably safer dh riding position. Ofc there is some exceptions to the rule, some enduros are super slack like dh bikes or have long chainstays, but you can guarantee those that have all those traits and a long reach will have stupidly long wheelbases and turn like a canal boat.
I also am not a fan of steep seat tubes, as in order to get full leg extension during pedalling you need to have your saddle pretty damn high up as you are more centred over the bb, this creates more hand pressure during casual riding, it's better for cornering grip while seated conpared to older geo bikes, but tbh if you are ripping corners fast, you don't do it sat down, you stand up and tilt the bike over, so what is kind of an advantage to the steep seat tube becomes a mute point in reality. But disregarding dh bikes for a minute, in general the newer bikes are better overall than the old enduros both climbing and descending, so they have moved in the right direction but maybe have took a slightly skewed path. Slack, with decent wheelbase, shorter reaches, longer stays for stability and front wheel grip and keeping the wheel down during climbing along with a slightly reduced seat tube angle I thing would be ideal, at least for me.

I mostly agree with Dan

To the OP
Another point is imagine you had an imaginary bike with a Pivot in the middle of the head tube that allows you to adjust head angle. As you slacken it your reach goes down as your wheelbase goes up, now throw on a 50mm stem as is common on dh bikes that puts your hands back where they were and you see why a dh bike of comparable feel to your enduro is 20mm or more shorter in reach.

I've got one of the OG long and slack af bikes (it's been dethroned but it was early) a mondraker summum c

To get the thing to turn for park use I ended up running the chainstays long, and taking 1 degree out of the HA and -4mm reach with a custom made headset. This bike has what some people consider a long reach, but by today's standards it's not Very long. f*cking thing was a barge to turn before.....

Dan.
I like the steep seat angles, not super duper long reach, and not the shortest chainstays. The steep seat angle I find the handling seated much better, on easy parts of climbs or rather the flatest parts I find jamming along seated but still hitting the turns hard to be nice.... I also frequent a trail network with "uphill flow trails" bearmed out switchbacks as the climbs.... couldn't imagine wanting a slack sta there....
flag Danzzz88
Posted: Nov 6, 2021 at 8:44 Quote
englertracing wrote:
Danzzz88 wrote:
For numerous reasons, one reason, at least a few years ago, dh bikes were slacker than enduro, with longer forks and often longer chainstays so the wheelbase was already massive as it is, a longer reach would just make the wheelbase too long. Secondly as stated above, due to enduros needing to climb, a more forward weight shift via means of a steep seat angle was introduced to make up for the fact the bikes got longer and slacker to improve dh performance...some people swear by this modern geo, for me personally I am not 100% convinced, I ride an sb165 and although the geo feels nicer overall than my older sb6 I still prefer the geo of a dh bike. The shorter reach means you can be more upright and in less of a push up position over the bars, as the slack head angle, high stack, long wheelbase keep you in a safe position, additionally long chainstays help generate more front wheel traction by inducing a more forwards weight bias so it doesn't become as neccessary to hang over the front to generate grip creating a more comfortable, relaxed and arguably safer dh riding position. Ofc there is some exceptions to the rule, some enduros are super slack like dh bikes or have long chainstays, but you can guarantee those that have all those traits and a long reach will have stupidly long wheelbases and turn like a canal boat.
I also am not a fan of steep seat tubes, as in order to get full leg extension during pedalling you need to have your saddle pretty damn high up as you are more centred over the bb, this creates more hand pressure during casual riding, it's better for cornering grip while seated conpared to older geo bikes, but tbh if you are ripping corners fast, you don't do it sat down, you stand up and tilt the bike over, so what is kind of an advantage to the steep seat tube becomes a mute point in reality. But disregarding dh bikes for a minute, in general the newer bikes are better overall than the old enduros both climbing and descending, so they have moved in the right direction but maybe have took a slightly skewed path. Slack, with decent wheelbase, shorter reaches, longer stays for stability and front wheel grip and keeping the wheel down during climbing along with a slightly reduced seat tube angle I thing would be ideal, at least for me.

I mostly agree with Dan

To the OP
Another point is imagine you had an imaginary bike with a Pivot in the middle of the head tube that allows you to adjust head angle. As you slacken it your reach goes down as your wheelbase goes up, now throw on a 50mm stem as is common on dh bikes that puts your hands back where they were and you see why a dh bike of comparable feel to your enduro is 20mm or more shorter in reach.

I've got one of the OG long and slack af bikes (it's been dethroned but it was early) a mondraker summum c

To get the thing to turn for park use I ended up running the chainstays long, and taking 1 degree out of the HA and -4mm reach with a custom made headset. This bike has what some people consider a long reach, but by today's standards it's not Very long. f*cking thing was a barge to turn before.....

Dan.
I like the steep seat angles, not super duper long reach, and not the shortest chainstays. The steep seat angle I find the handling seated much better, on easy parts of climbs or rather the flatest parts I find jamming along seated but still hitting the turns hard to be nice.... I also frequent a trail network with "uphill flow trails" bearmed out switchbacks as the climbs.... couldn't imagine wanting a slack sta there....

Yes that is the first thing I noticed with the new geo, the seated handling is much better than the old bikes that's true... But what I don't like is having to have the saddle so high and the increased hand pressure. The trouble is if you raise your bars to compensate for this they then end up too high for standing dh to get enough weight on the front and to feel comfortable. Personally I would like the reaches to be brought back a tad, the seat angles to slacken a couple degrees, the head angles maybe to get a degree or so slacker and about another 20mm adding to the chainstays. This hopefully in my mind would allow a more comfortable seated position with less hand pressure, and no need to ride over the front as much to generate grip...the longer chainstays generating the front grip for you and keeping the wheel down during climbs all whilst keeping the wheelbases the same as they are now...

But I can see a downside to longer chainstays, obviously manuals or those that like to flick their bike around a lot may not prefer them...personally I thought I preferred the shorter stays when I first hopped on my sb165 from my sb6 as manualing suddenly became a lot easier and the rear end felt stiffer and the bike corners fantastic....but I quickly came to realise the rear end will suddenly just go with short stays, it will stay locked in up to a point and then bam it just slides and doesn't feel as controllable during a slide as longer stays...the suspension performance seems to suffer slightly, I'm guessing as for a certain size bump the bb will raise higher with shorter stays than with longer ones.

There is a quick fix, and I think the one most lilely to happen with bike geo in the future as I can't see them taking things back a notch, so I imagine they are just going to start producing lomger chainstays...this will balance the bikes out more but the problem is we will be looking at bikes with huge wheelbases, much longer than most DH bikes and I'm not sure if this quick fix is the best way to go about it.

Personally I find the bb's too low too, I get an awful lot of pedal strikes on the current enduros. If they end uo making the bikes wheelbase longer due to increased chainstay length I'd hope they would raise the bb's a tad. But judging by the recent Pinkbike poll it seems the majority think everything is fine as it is or want even longer reaches...so I can't see my ideal bike happening any time soon. Luckily companies like Nicolai make custom geo frames, I'm also currently considering selling my sb165 and buying a dh frame with a decent seat tube angle and insertion depth and converting it into an enduro.
flag CarolineHix
Posted: Nov 6, 2021 at 10:17 Quote
Eek DH bike is not mean't for pedalling.. the only reason it has a saddle is so you don't get the seat tube up ya b...

The reason why reach is typically shorter is because when going downhill Rolleyes you need to be able to put weight on the front for grip. (That is why there is a general shift toward's mullet style, thin small wheel at the back for less rolling resistance and big chonk for the front)

Also if your arms were stretched out just from sitting on the bike you are generally not going to be able to push the bike out in front of you.

Book enduro's are just wanna-be dh bikes. they will try anything to be edgy. Beer
flag Toymaniac
O+
Posted: Nov 17, 2021 at 5:33 Quote
I wonder if the "dynamic reach" (new term I just made up) is similar between an enduro bike and a DH bike. Reach grows when the front fork compresses. Since a DH bike has more sag because it has more total travel will the reach grow significantly more with a DH bike and make the reach similar between the two when riding?
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