[Closed] Tell me about frame angles - how do they affect handling?

http://www.pinkbike.com/news/bike-frame-geometry-2009.html

Thanks for posting that but if it's 'in depth' then it turns out I was an expert already!

The bikes are quite different angles aside! You get the steep vs slack thing right? Length of tubing, and cockpit dimensions further alter this. Then there's fork type, length, settings etc etc.

Angles on their own aren't enough to differentiate. You have 40mm more fork and a rear shock on the Zesty not to mention different masses and weights.

The difference you have pointed out can be created and remedied based on bar and stem combinations!

It's all relative innit.

EDIT: there's also fit and riding posture to add more variables to the haystack within which your needle is hidden.

The bikes are quite different angles aside

I mentioned that in my OP.

What I really wanted to know was what aspects of the difference in ride can be attributed wholly or in part to angles.

I fully appreciate that this is a difficult thing to tease out as there are lots of interacting factors involved.

I'm not sure what your question is. They're totally different bikes with totally different geometry so of course they'll handle and react differently.

Do you mean bar height, width, tyre size, etc.? If you do then you'd need to make those alterations to 2 bikes identical in everything else other than the bits you want to analyse.

I'm not sure what your question is.

what aspects of the difference in ride can be attributed wholly or in part to angles?

Perhaps my initial post was a little confusing but the above is what I was really getting at.

2 bikes identical in everything else other than the bits you want to analyse.

Ok lets assume we've got 2 identical bikes one with a 71 degree head angle and one with a 67 degree head angle

What aspects of the differences in handling I noted in the OP would we see on 2 such bikes?

Come on lad, use your brains...

Slack angle at the front males a bike slower to respond to steering input, so more stable or less twitchy.

Slack angle at the front males a bike slower to respond to steering input, so more stable or less twitchy

Why?

And what about my point regarding the propensity of the hardtail front wheel to drop into holes? Is this a result of head angle or are other factors (including rider incompetence!) at play?

I have a suspicion that lots of people think they understand these things but it stops at slack = stable steep = twitchy. Is that the height of it or is there more involved?

Why?
Because it does. You are over analyzing this to a large degree, accept that as a basic theory and move on.

Because it does. You are over analyzing this to a large degree, accept that as a basic theory and move on.

Deary me. I hope you are not a teacher of any sort or even a parent with an attitude to questioning like that!

I'd like to know why my bike behaves in the way it does. What's wrong with that?

And, assuming you had the same forks on these imaginary bikes the rake would also change which would further affect the handling.

And, assuming you had the same forks on these imaginary bikes the rake would also change which would further affect the handling.

And more rake = slower steering? Am I right?

So our test rig would need adjustable rake too.

.... Hmmm.
What you are doing is childish and immature. I am a parent, not that its any business if yours, and if you where a child of mine I would suggest that if you wish to know more about the physics of bicycle design, perhaps you could use a reference work, or maybe the internet to find out more.

Or carry on being petulant...

Deary me.

:facepalm:

When I get on a proper keyboard rather than a phone I might answer this properly, but get ready to read a long reply. There's lots of factors involved as I'm sure you've already gathered.

or maybe the internet to find out more

Where are we now? I thought that perhaps someone on here might know, much better to engage in discussion with enlightened individuals than trawl through loads of stuff that doesn't directly anwer your questions.

What you are doing is childish and immature

If asking questions is childish and immature then guilty m'lud.

Fork length can counteract or exaggerate head angle (steep climbs well, reacts fat (road, DJ, BMX) and descends nervously on the rough). Likewise seatpost layback or not plus saddle position and height adjusts your position above the BB shell and proximity to the rear wheel contact patch. Again the chainstay length then adjusts the weight distribution.

Flickable (DJ):
Short wheelbase, low weight, frame size biased to smaller, 26" wheels, hardtail.

Confident descending (DH):
Slack, long travel, full suspension, slack seat tube, low top tube, short stem & wide bars, big tyres.

Climbs well (XC):
Steep head angle, steep seat tube angle, short travel/rigid, longer stem, hardtail, lightweight, skinnier lighter tyres.

I'd stick a shorter stem and longer travel fork on your hardtail. FS bikes just don't climb as well, saving some weight on it will make it a little more flickable and climb better. Suspension settings have a huuuuge impact too, this may 'upgrade' the Zesty.

Spin - Member

Why?

And what about my point regarding the propensity of the hardtail front wheel to drop into holes?

Centre of gravity - when your centre of gravity goes past the front axle, you go over the bars. Slacker angle puts the wheel further in front of you, making it harder for this to happen. Other factors (top tube length, fork travel, stem length) will play a part also, as they'll all affect the same.

but get ready to read a long reply

I'd be delighted to.

And of course a shorter fork is going to get hung up in holes easier as it has less of an ability to adapt as well as a rear end directly following due to the HT frame. A FS hugs the shape of what you ride over and shrugs off such problems, this is a bigger factor than head angle.

Slacker angle puts the wheel further in front of you, making it harder for this to happen

This was my suspicion but I wasn't sure.

Some good replies coming now I've sorted out initial confusion!

A FS hugs the shape of what you ride over and shrugs off such problems, this is a bigger factor than head angle

This too was in my mind.

Also, as I move weight back on the FS the rear shock compresses. Does this also effectively slacken the head angle?

Spin - Member

Also, as I move weight back on the FS the rear shock compresses. Does this also effectively slacken the head angle?

It would do - and lowers your COG at the same time.

So because I'm not professor of bicycle physics its ok to suggest I shouldn't be a teacher or have children?

I'm not allowed to call you what I think you are. Enjoy your lessons.

So because I'm not professor of bicycle physics its ok to suggest I shouldn't be a teacher or have children?

Whoa there fella. I apologise for that comment but perhaps you should look at the tone of your own posts to see how we arrived at that?

I am a teacher and have an inherent distaste for any answer of the format 'because it does'. A more honest answer would be 'I don't know'

Fellas, getting confrontational about hypothetical frame angles is pretty daft. But wonderfully STW.

Spin, you started being quite vague which Crikey identified. You then were offended and made a personal remark about him and now you're both being all...icky.

I accept your e-knuckle rap with humility. 🙂

Meh....

apologies for assumed grumpiness; I was trying to say that I didn't think it was important enough to go deep into.. 🙂

Cool, now that's over: Spin, did you want to tweak your bikes to behave differently or just understand things a bit more? What's the steel frame?

Now I'm on newly installed computer rather than phone...

There is a difference in handling between different angles, but as noted above a difference in angle is usually associated with a different bike altogether.
I used a trad Dutch bike in Amsterdam; massively slack angles, single speed, laid back bars to the extent that I was almost hanging off the back. It was superb on the cobbles around town; gentle over the bumps, stable at low speeds, and ideally suited to its environment.

The angles were part of the overall package; influential but not the sole difference.

Compare to my road race bike; designed to be a compromise between sharp handling but the ability to sit in a bunch and not take them all down. The difference is chalk and cheese, but angles are only a part of the whole.

As a general rule, the slacker the angles at the front, the less a bike responds to steering input, so takes longer to turn in, but is stable.

Nicknoxx - Member
And, assuming you had the same forks on these imaginary bikes the rake would also change which would further affect the handling.

If by rake you mean offset (the amount that the wheel spindle is ahead of a line through the headset bearings)then this is fixed by the design of the forks and won't change with head angle.
What[b] will[/b] change is trail - the slacker the head angle becomes, the more the amount of trail increases for a given fork.

Spin, did you want to tweak your bikes to behave differently or just understand things a bit more? What's the steel frame?

Just understand the handling differences. But knowing how to tweak would help with that. I like how both handle for different applications. HT for tight single track, FS for steep and rocky.

The steel frame is a 'Pastey Howler' 853. I think they went tits up not long after I purchased.

Ah ok, looks like they did a nice ti frame too.

I don't know whether you've bought into wider bars, but my Sunline V1 711mm risers have had a very positive effect on my Trance. The Trance in it's stock form is probably about as much of an upper as a downer. A 70mm stem and the 711 bar have help it descend better, as has the slightly longer-than-stock Pike. A 60mm stem descended in a more fun way but the 70 makes climbing more comfortable. The light frame and efficient Maestro make it climb quite well, I just need to stay fit to lug the Pike up with me!

I think it's good to have differentiation between the bikes, otherwise there's no point in having the 2 other than n+1 🙂

I don't know whether you've bought into wider bars

After buying the Zesty I put some 690mm risers and a shorter stem on the Pastey which did make a difference.

I think it's good to have differentiation between the bikes

This is a good point.

I guess it was the fact that I had to press the HT into the kind of role I was using the FS for that prompted my post. I think my points have been pretty well answered.