Head Angles - how slack is slack

h34e0f

Lets discuss head angles.

What kind of angles are most common for trail bikes / AM rigs?

Would a change from a bike with say, 69° to one with 66° be that noticeable or affect ride much? I know it would also depend on other factors like stem and handle bar length but assuming both bikes were using the same cockpit, how much difference would be noticeable out on the trail?

nicklouse

it depends on the bike and what travel it was designed for. It also depends on how it is measured.

and to answer your question it would be crap and changing bars and stem would not make it better.

not to mention stressing the head tube to possible failure.

h34e0f

nicklouse wrote:

it depends on the bike and what travel it was designed for. It also depends on how it is measured.

and to answer your question it would be crap and changing bars and stem would not make it better.

not to mention stressing the head tube to possible failure.

I was referring to a change in frame to one with a differing angle. Sorry, that wasn't clear.

CycloRos

very generally on trail bikes a typical HA would be between 68 and 71 deg, AM and DH 68 or slacker

in terms of feel it's equally as much about fork length as HA, and how the HA was actually measured (static or sagged).

the slacker head angle does generally make a bike feel more stable on the downs

h34e0f

I need to get myself an adjustable fork and have a play. I can now see myself going round my mates house late at night and stealing his 100-130mm Revs......................... 8)

supersonic

It also changes seat angle. When you are sat, a slacker seat angle puts your weight further back. Couple that with a slacker head angle too, and steering will be fun...

h34e0f

supersonic wrote:

It also changes seat angle. When you are sat, a slacker seat angle puts your weight further back. Couple that with a slacker head angle too, and steering will be fun...

Is that sarcasm? Damn internet

supersonic

No, it's true! With so little weight on ther front end, putting a fork on a frame not designed for it really buggers the handling up.

h34e0f

No no you lot have got totally the wrong idea. I'd talking about TWO DIFFERENT FRAMES.

Comparing a 69° frame to a 66° frame.

supersonic

So why mention your adjustable fork?!

h34e0f

supersonic wrote:

So why mention your adjustable fork?!

I don't have an adjustable fork.

All I wanted to know is if I'd notice much difference from switching from a frame with a HA of 69° to one with 66°.

lawman

geometry semms to be getting slacker year on year, the latest 140-150mm travel bikes hover around 66-67HA and 72-74SA, and imo HA wise are getting towards the perfect compromise, my mojo HD is about 67.5, would like to slack it out abit more to around 66.5, but for 90% of the time its pretty much spot on and very stable, but geometry is only part of the whole bike, a bike can have great geometry but can be let down by poor suspension performance, and in most instances a bike with better suspension, but slightly "out" geometry will outperform a bike with spot on angles but suffers in the suspension department

supersonic

Ok, your mates fork - is quite easy to assume from that you are planning to see what the fork lengths do!

But for two identicle frames BAR the head angle, the steering will feel slower and more stable with the slacker head angle.

But pay attention to seat angles too when looking at frames.

h34e0f

supersonic wrote:

Ok, your mates fork - is quite easy to assume from that you are planning to see what the fork lengths do!

But for two identicle frames BAR the head angle, the steering will feel slower and more stable with the slacker head angle.

But pay attention to seat angles too when looking at frames.

The fork comment was in reply to CycloRos's comment saying that fork length is equally important.





Some good points raised, will add to my thoughts, thanks.

Anonymous

h34e0f wrote:

All I wanted to know is if I'd notice much difference from switching from a frame with a HA of 69° to one with 66°.

So, essentially, in essence, really, what you're asking, actually, is.....

Will you be able to tell the difference between two completely different bikes?

Erm, Yes, you should do.

h34e0f

yeehaamcgee wrote:

h34e0f wrote:

All I wanted to know is if I'd notice much difference from switching from a frame with a HA of 69° to one with 66°.

So, essentially, in essence, really, what you're asking, actually, is.....

Will you be able to tell the difference between two completely different bikes?

Erm, Yes, you should do.

Clearly.

This was intended as a theoretical discussion. Two identical bikes, but with different head angles. I want to know the difference HA makes to a bikes ride and feel, ignoring all other factors, and if 69 to 66 degrees was worth bothering with.

Anonymous

h34e0f wrote:

Two identical bikes, but with different head angles.

Then they would not be the same bike.

h34e0f

yeehaamcgee wrote:

h34e0f wrote:

Two identical bikes, but with different head angles.

Then they would not be the same bike.

As said. Theoretical.

Please stop with ridiculous replies. I'm clearly just trying to gather some information to learn more about geometry. Difficult/argumental coments don't help.

Thanks to those who gave sensible answers.

Anonymous

It's really n0ot a ridicilouse reply, it's a ridicilouse question. Changing one thing WILL change other things.

warpcow

h34e0f wrote:

yeehaamcgee wrote:

h34e0f wrote:

Two identical bikes, but with different head angles.

Then they would not be the same bike.

As said. Theoretical.

Please stop with ridiculous replies. I'm clearly just trying to gather some information to learn more about geometry. Difficult/argumental coments don't help.

Thanks to those who gave sensible answers.

The problem is that two "identical", apart from the head-angle, bikes would in no way be identical. Changing the head-angle would change everything else too (seat-angle becomes steeper, wheelbase longer, BB lower, etc).

h34e0f

warpcow wrote:

h34e0f wrote:

yeehaamcgee wrote:

h34e0f wrote:

Two identical bikes, but with different head angles.

Then they would not be the same bike.

As said. Theoretical.

Please stop with ridiculous replies. I'm clearly just trying to gather some information to learn more about geometry. Difficult/argumental coments don't help.

Thanks to those who gave sensible answers.

The problem is that two "identical", apart from the head-angle, bikes would in no way be identical. Changing the head-angle would change everything else too (seat-angle becomes steeper, wheelbase longer, BB lower, etc).

That's the answer to the question.

Briggo

If you knew the answer why did you ask the question.

FBM.BMX

Since everyone else is being pedantic and finnicky.

A slacker head angle will slow down your steering and lengthen your wheelbase. NOTE: A slacker HA will also effectively shorten the tt.

(i'm differentiating steering speed and turning speed here. Steering speed is how quick the front wheel turns, turning speed is how quick the bike turns)

Longer wheelbase = more stable at speed and slower turning.

The main reason people like slacker head angles is that it makes the wheel base longer than a equivalent length ttubed frame. This makes the bike more stable at speed, thus more confidence inspiring.

People don't generally like how much slower the front wheel moves with bar input, it's all down to "castor angle", you've got to fight harder to turn the bars. this is solved by running a shorter stem.

Shorter stem = less front end room in the saddle, (slacker head angle also shortens the tt length), so the tt gets longer. then we enter the realm of modern "trail" geo with slack HA's, short stems and long tts.

I hope that helps.

Yes, if you took two identical frames, then adjusted HA through angleset or fork length, this would change the BB height and SA. But i get that you're doing this theoretical like, to get a grasp of geo. Shame the others have to get out their e-nuts to demonstrate how large they are (not meant to be offensive, just a metaphor to demonstrate what you're doing).

As for effect, from personal experience, haven't found it matters on the ups, or on the downs when i'm comfortable and in control. i've really noticed it when i've been going flat out and got loose, of riding really steep down.

So if you normally ride well inside your comfort, doesn't make a real difference, if you push things occasionally, you'll notice it.

nicklouse

FBM.BMX
but as he is asking about two different frames most of the above is not relevant.

supersonic

I find it makes a difference - front end more likely to lift and wander with a slacker head angle, but again is hard to equate without mentioning seat angle and other measurements. Seat angle plays a huge role in seated bike handling. Too steep in slow corners and the front end feels like it is tucking under.

I think a common mistake is people upping travel, fitting a shorter stem and using layback to compensate - this on many bikes (again depends on the exact figures) as it takes away weight on the front end and makes it more liable to wash out.

We see many longer travel bikes nowadays with 73-74 degree SA to push that weight back forward. Most 'pre suspension' corrected bikes problems came form slack seat angles and high BBs rather than HA.

h34e0f

FBM.BMX wrote:

Since everyone else is being pedantic and finnicky.

A slacker head angle will slow down your steering and lengthen your wheelbase. NOTE: A slacker HA will also effectively shorten the tt.

(i'm differentiating steering speed and turning speed here. Steering speed is how quick the front wheel turns, turning speed is how quick the bike turns)

Longer wheelbase = more stable at speed and slower turning.

The main reason people like slacker head angles is that it makes the wheel base longer than a equivalent length ttubed frame. This makes the bike more stable at speed, thus more confidence inspiring.

People don't generally like how much slower the front wheel moves with bar input, it's all down to "castor angle", you've got to fight harder to turn the bars. this is solved by running a shorter stem.

Shorter stem = less front end room in the saddle, (slacker head angle also shortens the tt length), so the tt gets longer. then we enter the realm of modern "trail" geo with slack HA's, short stems and long tts.

I hope that helps.

Yes, if you took two identical frames, then adjusted HA through angleset or fork length, this would change the BB height and SA. But i get that you're doing this theoretical like, to get a grasp of geo. Shame the others have to get out their e-nuts to demonstrate how large they are (not meant to be offensive, just a metaphor to demonstrate what you're doing).

As for effect, from personal experience, haven't found it matters on the ups, or on the downs when i'm comfortable and in control. i've really noticed it when i've been going flat out and got loose, of riding really steep down.

So if you normally ride well inside your comfort, doesn't make a real difference, if you push things occasionally, you'll notice it.

Thank you, great response.