Will HA become steeper again in the future?

PB Forum :: All Mountain, Enduro & Cross-Country
Will HA become steeper again in the future?
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flag RadBartTaylor
Posted: Jan 12, 2020 at 21:46 Quote
kiksy wrote:
rpet wrote:

Downhill bikes have had roughly the same HA for a decade.


This. Bikes that are bought primarily for going downhill should have dh style geometry.

Steep head angles, short wheelbases and high bbs just feel horrible now.

If you want xc geo, buy an xc bike? If it's still not steep enough, reverse angleset 2 degree, and offset bushings in reverse to raise bb a little and steepen head angle more.

In my mind, we're still not quite there yet there with the long low and slack geo. Especially on XL bikes.

he didn't say he wanted a 'steep' angle.....just will they steepen from being so slack.

I'm 100% in the camp of yeah, they will steepen up a bit, not back to 68 degrees, buy maybe back to 65'ish.
flag englertracing
O+
Posted: Jan 12, 2020 at 23:26 Quote
I think they wont get any slacker but will get shorter offsets/more trail. Maybe, maybe some all mountain/trail bikes will go back a half degree with shorter offset
flag bikefuturist
Posted: Jan 13, 2020 at 4:43 Quote
RadBartTaylor wrote:
kiksy wrote:
rpet wrote:

Downhill bikes have had roughly the same HA for a decade.


This. Bikes that are bought primarily for going downhill should have dh style geometry.

Steep head angles, short wheelbases and high bbs just feel horrible now.

If you want xc geo, buy an xc bike? If it's still not steep enough, reverse angleset 2 degree, and offset bushings in reverse to raise bb a little and steepen head angle more.

In my mind, we're still not quite there yet there with the long low and slack geo. Especially on XL bikes.

he didn't say he wanted a 'steep' angle.....just will they steepen from being so slack.

I'm 100% in the camp of yeah, they will steepen up a bit, not back to 68 degrees, buy maybe back to 65'ish.

Isnt like every trail bike 65ish nowadays
flag R-M-R
Posted: Jan 13, 2020 at 8:33 Quote
zeeLLAMA,

I actually agree with what you're saying, I just think you may not be expressing it effectively.

Your thought process appears to be what Mondraker's WC DH team did when they developed their long geometry:

• Realize bikes were too short, especially in the front-centre
• Slacker head angles, all the way out to sub-60°
• Like the front-centre, but realize this puts the bars in your lap
• Keep the same front contact point, but get there via longer reach and not as slack head angle

If I'm interpreting you correctly, you're suggesting doing this with the current geometry trends by keeping most of the length, keeping the steep seat-tube angles, and using steeper head angles to ensure sufficient top-tube length. If that's what you're saying, I mostly agree, though I don't feel we need to reduce length from currently long, but not outlier, bikes.

My thoughts on some variables:

• Seat-tube angle: Depends on the rear travel. More travel produces more sag, so the two parameters should vary together. In general, steep is good.
• Head-tube angle: It's misunderstood. If we design for front-centre and trail, head-tube angle becomes the outcome, not the driving variable. Current (i.e. models released in 2019 - 2020) enduro category numbers are probably close, the "extreme" designs may have gone too far, and XC numbers will become slacker.
• Trail: Plenty of it. DH bikes and trail / AM / enduro bikes with outlier geometry are on the right track.
• Front-centre: Unsure how much longer we can go, relative to the current vanguard bikes, before they become difficult to handle on flat terrain due to lack of pressure on the front wheel. If seat-tube angles get steeper and head-tube angles remain about the same, there remains some room to increase front-centre, especially if we reduce fork offset.
• Fork offset: Less. This will reign in front-centre length, improve fork function, and increase trail.
• Reach: Hasn't kept pace as seat-tube angles get steep and stems remain short. Can increase, especially on long-travel bikes with steeper seat-tube angles, but front-centre needs to be managed unless the bike is to be optimized for steep descents.
flag zeeLLAMA
Posted: Jan 14, 2020 at 16:23 Quote
@R-M-R Yes, I do say that, but I take the level of complexity way further, considering wheelbase and even BB to grip distance.

I think for someone who's a veteran rider, who has settled down to be a social rider, who paces off of people who are casually riding (safe and fun riding, avoiding injury risk), a shorter wheelbase is more engaging (fun).

Lee McCormack found an interesting fit system: RAD and RAAD. I used to be skeptical, but it makes sense. Where the grips are, in relation to the BB is huge for all the techniques done when standing. People seem to be too uncompromising when it comes to seated riding, but a rider is standing when things get demanding, and it's odd to compromise that.

I thought about how to combine everything together, and thought about what role head angles actually played. I found that it can affect how effective telescoping forks are, by better aligning it with a bump. Steering and stability are from mechanical trail and front center, which can be tweaked through fork offset and reach.

With steepening STA, lengthening reach, and perhaps some rising demand for short wheelbase, steep HA just seemed to be something that needed to be accepted.

That Pinkbike prototype wouldn't be so ridiculous if it had a steeper HA.
flag Oscillation
Posted: Apr 13, 2020 at 20:16 Quote
R-M-R wrote:
zeeLLAMA,

• Head-tube angle: It's misunderstood. If we design for front-centre and trail, head-tube angle becomes the outcome, not the driving variable. Current (i.e. models released in 2019 - 2020) enduro category numbers are probably close, the "extreme" designs may have gone too far, and XC numbers will become slacker.

That's a new way of thinking to me but digging it for sure. It makes sense as all other associated variables taken into account, one 65 degree bike is not necessarily going to handle like another. Curious if I'm just out of the loop or are manufacturers thinking in these terms already? Sure doesn't sound like it given the mumblings among the bike community..
flag R-M-R
Posted: Apr 13, 2020 at 22:22 Quote
Oscillation wrote:
That's a new way of thinking to me but digging it for sure. It makes sense as all other associated variables taken into account, one 65 degree bike is not necessarily going to handle like another. Curious if I'm just out of the loop or are manufacturers thinking in these terms already? Sure doesn't sound like it given the mumblings among the bike community..

There are two streams of folks in any community, including bike designers and the bike-buying public: those who understand (or sometimes misunderstand) the physics and those who go with the flow and eventually - maybe - absorb the knowledge around them. Some bike designers just take their last generation of bike and tweak it, producing incremental change. Some are "fast followers" who look around the industry and follow emerging trends. Nothing wrong with either approach - certainly less risky. Some designers are the ones driving things forward - and often sideways!

Broadly speaking, no, this approach isn't common, but it's not rare. Much of the seemingly vanguard thinking about bike handing was well understood a century ago. As an example, have a look at Bicycles & Tricycles: An Elementary Treatise on Their Design and Construction by Archibald Sharp, 1896. As motorcycles and cars became more popular and more sophisticated, considerable literature was published on chassis dynamics and suspension. I don't recall whether Sharp specifically address this relationship, but these ideas aren't entirely new; sometimes, it's just in how to combine known variables. Unfortunately, not every designer in the industry is keen on reading about our collective history.


zeeLLAMA wrote:
I think for someone who's a veteran rider, who has settled down to be a social rider, who paces off of people who are casually riding (safe and fun riding, avoiding injury risk), a shorter wheelbase is more engaging (fun).

True. The bike should suit the terrain and the riding style. If either or both is less intense, less stability is required.


zeeLLAMA wrote:
Lee McCormack found an interesting fit system: RAD and RAAD. I used to be skeptical, but it makes sense. Where the grips are, in relation to the BB is huge for all the techniques done when standing. People seem to be too uncompromising when it comes to seated riding, but a rider is standing when things get demanding, and it's odd to compromise that.

I'm not a fan of McCormack's fit systems. I do agree there should be minimal compromise on standing position and I think recent geometry accomplishes that with super steep seat-tube angles. The butt-to-bar distance on such a bike may be awkwardly short for the rider, then the rider stands and the bike is plenty long due to the long reach. Some bikes may even take this too far and may benefit from even greater reach with a bit steeper head-tube angle. The only way to know is to push the limits until we've clearly gone too far and I'm grateful a few folks are exploring these limits.


zeeLLAMA wrote:
[Head-tube angle] can affect how effective telescoping forks are, by better aligning it with a bump. Steering and stability are from mechanical trail and front center, which can be tweaked through fork offset and reach.

I agree and all these properties are well known. Linkage front suspension has the potential to solve the issue of bushing friction.


zeeLLAMA wrote:
That Pinkbike prototype wouldn't be so ridiculous if it had a steeper HA.

True, but it wouldn't generate so much website traffic!
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