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Josh and Slowman Debate Cp and Handling
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So I posted this the comment below on Dan's preview of the new Specialized and he responded that he disagreed with the Cp rationale, so we're moving it here to discuss further:

"...As for fork leg placement, we proved from a number of angles that you need the center or pressure for the front wheel in front of the steering axis and not behind it. This is due the way that countersteer affects lean angle..if the Cp is behind the steering axis, a transient gust of wind will steer the wheel into the wind which makes the contact patch go in that direction initiating a lean in the opposite direction (lean with the wind) which then requires a large steering correction to stabilize. It seems counterintuitive, but having the Cp in front of the steering axis means that a gust of wind will steer the contact patch away from the wind which initiates a lean into the wind, so the effect is naturally stabilizing.
Sadly, Zipp doesn't show much CFD or data anymore, we used to have lots of interesting stuff on this when I was there, you can Google AIAA Matt Godo Zipp CFD or my name and find a lot of it, but the great example we used in the original Firecrest stability white paper was that a front disc has a Cp well behind the steering axis which is why a front disc outdoors can be stable in stable wind, but can be downright terrifying in gusty or variable wind. Similarly most 3 spoke wheels have Cp in front of steering axis at low yaw and behind it at high yaw which explains some of the challenging handling behavior of those designs in high yaw or variable wind."


The backstory here is that when we were developing Firecrest using Matt Godo's CFD protocol we realized that we could predict handling using side force mapping and Center of Pressure (Cp) calculations that were already beautifully built into the FieldView software.. the problem them became where to move it? Initially we wanted it positioned aft to give the wheel a rudder effect, but early prototypes were NOT stable. Benchmarking wheels at that time we realized that wheels people thought were stable, namely shallow wheels all had Cp that was forward of hub and of course low side force and wheels that people thought were unstable, front discs, the 1080, 3 spoke/5spoke wheels all had Cp behind the steering axis or Cp that migrated from in front to behind during the yaw sweep. The only other player who has really made a claim in this area is ENVE who along with Simon Smart targeted a Cp in front of the steering axis that resulting in a linear torque rise with wind angle, while the Zipp philosophy was to try and keep the Cp in front of but as close to the axis as possible... the difference is that the Zipps had lower torque that was non-linear to yaw angle while the ENVE's had higher torque that behaved more linearly.

Having said all that, this was roughly 10 years ago now and I've been out of the game for a few years so I'm free to talk and really interested to hear Slowman's input as he's much closer to that side of the industry at this point than I am..
Josh

http://www.SILCA.cc
Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
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Re: Josh and Slowman Debate Cp and Handling [joshatsilca] [ In reply to ]
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Fascinating info! I don't know, or understand enough, to really have an opinion, but it does go to show how conventional wisdom, or a layman's understanding, can really fall short.
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Re: Josh and Slowman Debate Cp and Handling [joshatsilca] [ In reply to ]
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Does this somehow relate to the fork design on the Louis Garneau Gennix bike about which Dan has written in the past? https://www.slowtwitch.com/...d_of_Bikes_6299.html

"Let’s dispel a myth. Surface area doesn’t make a bike hard to handle. Surface area in front of the steering axis makes a bike hard to handle, if it’s a lot of surface area and if it’s especially windy. "
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Re: Josh and Slowman Debate Cp and Handling [Rachela] [ In reply to ]
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That's what I immediately thought of, as well. We had a brief thread going on it, but it didn't go very far:

https://forum.slowtwitch.com/...ring=gennix#p6142370

Perhaps the handling characteristics created by Cp for a fork are different than a wheel because of other factors such as the fork rake/offset or trail?

Travis Rassat
Vector Cycle Works
Noblesville, IN
BikeFit Instructor | FMS | F.I.S.T. | IBFI
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Re: Josh and Slowman Debate Cp and Handling [joshatsilca] [ In reply to ]
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Having spoken with motorcycle racers about how they steer, your post made perfect sense to me. Curious to hear the other side.

***
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Re: Josh and Slowman Debate Cp and Handling [Rachela] [ In reply to ]
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Interesting that the Gennix has come into the discussion. Hasn't Sanders mentioned he thinks he's lost time on the Hawi descent because he's not confident in high speed, gusty crosswind situations? And that's also why he runs a Jet 6 up front, while many of his competitors are running something deeper? I'm sure Garneau designed what they thought was a more stable fork design, based on conventional wisdom, but did they actually test it against a counter-design? Honestly, with the resources they have (including an in-house wind tunnel), I'm more inclined to believe Specialized has this figured out than Garneau.

"They're made of latex, not nitroglycerin"
Last edited by: gary p: Oct 18, 18 12:21
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Re: Josh and Slowman Debate Cp and Handling [joshatsilca] [ In reply to ]
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Interesting, thanks for sharing. Can you comment on how the CP for a 303 is different than an 808 and how the CP changes for those wheels across a yaw sweep? Is the location of the CP for a 303 more stable than that of an 808?

My intuition is that CP for the front wheel and the bike/rider system should be different. E.g. the further to the rear for the bike rider system the better. Unless the winds were so bad I thought they could literally knock me over, I always felt the most stable running a rear disc.

Since you brought up the tori-spoke designs, did Zipp ever investigate such a design? What's your feeling about the "watts to spin" advantage of such a design?
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Re: Josh and Slowman Debate Cp and Handling [joshatsilca] [ In reply to ]
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This would be an easy thing to test out with some model rocket motors placed laterally, both in front of and in back of the steering axis....fire one of them off and see which way the bike moves :-)


Have Dan watch this video...


https://www.youtube.com/watch?v=llRkf1fnNDM

http://bikeblather.blogspot.com/
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primer on how geometry effects handling [ In reply to ]
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"https://www.velonews.com/...-lennard-zinn_480109"


If you need a primer on how geometry effects handling this was a great podcast about it. (not you Josh, just in general)


  1. The concepts of fork rake, head-tube angle, and trail, among others, and why each is a crucial element of bike design.
  2. How these factors act together to make the bike more or less stable, and why greater stability may not be what you’re looking for.
  3. The effects of wheel flop and how it impacts your ability to corner, including an explanation of counter-steering and when you’d want to use it.
  4. How understanding rake, trail, and flop can have a significant impact on your performance, as well as how you can put it to good use in selecting the right bike for you.
  5. The evolution of bike design and how it has been influenced by both fashion and performance.
  6. And finally, some guidelines on selecting your next bike and how to get the ride experience you want.

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Re: Josh and Slowman Debate Cp and Handling [joshatsilca] [ In reply to ]
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This makes perfect sense. But only IF one understands the highly counterintuitive way that cycles (bikes and motos) balance and steer.

That said, from a purely scientific perspective, your post makes me wonder to what degree this stays true if one could artificially move the steering axis CP far out in front of the bike, say 5 feet in front of the leading edge of the bike. It would be an interesting experiment to try out ...

Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook

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Re: Josh and Slowman Debate Cp and Handling [M----n] [ In reply to ]
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M----n wrote:
Having spoken with motorcycle racers about how they steer, your post made perfect sense to me. Curious to hear the other side.


Cyclists steer the same way that motorcycle racers do (at speed)...whether you realize it or not. This is why it's so difficult to ride one of those reverse steering bikes that someone posted about yesterday. Your brain learns how to counter steer when you first learn to ride a bike and it becomes part of your senses. You may not be actively telling your left hand to push the bar forward in order to turn left, but it does.
Last edited by: Jason N: Oct 18, 18 10:38
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Re: Josh and Slowman Debate Cp and Handling [joshatsilca] [ In reply to ]
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joshatsilca wrote:
This is due the way that countersteer affects lean angle..if the Cp is behind the steering axis, a transient gust of wind will steer the wheel into the wind which makes the contact patch go in that direction initiating a lean in the opposite direction (lean with the wind) which then requires a large steering correction to stabilize. It seems counterintuitive, but having the Cp in front of the steering axis means that a gust of wind will steer the contact patch away from the wind which initiates a lean into the wind, so the effect is naturally stabilizing.
Josh

how did you determine steering torque during your investigations? this is a leading question, but i would ask the court for indulgence.

Dan Empfield
aka Slowman
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Re: Josh and Slowman Debate Cp and Handling [joshatsilca] [ In reply to ]
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Interesting thread .. hopefully I understand the topic right (in the right direction) .. to try to understand how cornering works best my attempt is to adopt the scenario (situation and adjustments) .. in favor cornering can be divided in different shares with the aim to have a promising direction in summary without loosing speed unnecessarily .. these shares are build by the rider (physics and biology with senses & skills), the bike (physics) and the circumstances (changes) .. for cornering there are two principles possible .. let's say first is steering and second is balance (to lean in) .. different speeds, radii, bike geometries, weight distributions and so on prefer different steering and balance shares .. in which way does the Cp affect these actions?

For example a bumpy cross wind at hight speeds can steer my 60mm fw and it balances out if I don't counter steer too much and just do balancing a bit, too ..

*
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the s u r f b o a r d of the K u r p f a l z is the r o a d b i k e .. oSo >>
Last edited by: sausskross: Oct 18, 18 13:15
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Re: Josh and Slowman Debate Cp and Handling [sausskross] [ In reply to ]
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sausskross wrote:
Interesting thread .. hopefully I understand the topic right (in the right direction) .. understanding how cornering works best my attempt is to adopt the scenario (situation and adjustments) .. in favor cornering can be divided in different shares with the aim to have a promising direction in summary without loosing speed unnecessarily .. these shares are build by the rider (physics and biology with senses & skills), the bike (physics) and the circumstances (changes) .. for cornering there are two principles possible .. let's say first is steering and second is balance (to lean in) .. different speeds, radii, bike geometries, weight distributions and so on prefer different steering and balance shares .. in which way does the Cp affect these actions?

A cross wind can steer my 60mm fw and it balances out if I don't counter steer too much and just do balancing a bit, too ..


before we get too far into this, there are two ways "countersteering" is used in the nomenclature. one is while descending, and involves executing (say) a right hand turn by pressuring the left hand side of the handlebar. i'm boiling this down to a one-sentence explanation and if anyone has a problem with my wording then fine, but can you please start another thread on that?

the second is very obviously true, is not in debate, it's simply the way we ride our bikes. if i'm riding down a flat road, straight line, no wind, i'm almost constantly countersteering to stay upright. if i drift to the left, i can't turn to the right. in fact i must turn more to the left, so that i can get my center of mass between the line my bike is now taking and the line i want to reacquire. it isn't until that happens that i can actually execute a turn back toward the direction i intend to ride.

countersteering in the context of THIS discussion is limited to that second definition. i want to know who josh measured steering torque with a sidewind or side gust applied. because, you can't (in my mind) model that with confidence. you can't math that. you have to test that. and i've gotten the football pulled out from under me too many times by people who test in the wind tunnel and then i ask them if they actually tested for steering torque and they say yes but then i ask for the data and that data never arrives.

so, when josh says what he says, if i understand what he says correctly, i'm just saying i don't believe it. it's not that i don't think there's reasoning. modeling. it's that i don't think there's data. i have to be shown that there's data, and that this data is in some way analogous to real world riding.

it seems to me that, while not pretty, while not easy, while noisy, the way to do this is with field trials. were field trials done? what was the tooling? what was the protocol?

i'm glad to be proved wrong. i don't have an dog in this. i just would like to actually know that steering torque is a *thing* people are testing for, and that it's done in a way that makes clear sense.

Dan Empfield
aka Slowman
Last edited by: Slowman: Oct 18, 18 13:15
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Re: Josh and Slowman Debate Cp and Handling [Slowman] [ In reply to ]
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Slowman wrote:
. it's that i don't think there's data. i have to be shown that there's data, and that this data is in some way analogous to real world riding.

Yes! So far we're dealing with Josh's memory from 10 years ago and Slowman's memory from 50 years ago (or whatever it was). I imagine Zipp's data could be proprietary. And I imagine a lot of other data and testing could be proprietary. So it might be hard to find good data without some Good Samaritan testing or donated data from some company that decides in it's best interest to publicly release some information.
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Re: Josh and Slowman Debate Cp and Handling [joshatsilca] [ In reply to ]
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What changes of a build do effect Cp location in which direction ?

*
___/\___/\___/\___
the s u r f b o a r d of the K u r p f a l z is the r o a d b i k e .. oSo >>
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Re: Josh and Slowman Debate Cp and Handling [trail] [ In reply to ]
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trail wrote:
Slowman wrote:
. it's that i don't think there's data. i have to be shown that there's data, and that this data is in some way analogous to real world riding.


Yes! So far we're dealing with Josh's memory from 10 years ago and Slowman's memory from 50 years ago (or whatever it was). I imagine Zipp's data could be proprietary. And I imagine a lot of other data and testing could be proprietary. So it might be hard to find good data without some Good Samaritan testing or donated data from some company that decides in it's best interest to publicly release some information.

or... there is no data. no relevant test data, relevant being: side wind hits a rider, does that push the rider's steering wheel in the direction the wind is going? i think so. or does it push the wheel into the wind? i'm very skeptical of that. if my assumption is right, then, putting surface area behind the steering axis (but attached to the steerer) corrects for that? normalizes for that? or, putting surface area in front of the steerer normalizes for that? reduces that tendency? my sense tells me that behind the steerer is better. i'd need to see test data that demonstrates otherwise.

if there just is no relevant data, that is no sin. just, that is what has always turned out to be the case.

Dan Empfield
aka Slowman
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Re: Josh and Slowman Debate Cp and Handling [Slowman] [ In reply to ]
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Slowman wrote:
trail wrote:
Slowman wrote:
. it's that i don't think there's data. i have to be shown that there's data, and that this data is in some way analogous to real world riding.


Yes! So far we're dealing with Josh's memory from 10 years ago and Slowman's memory from 50 years ago (or whatever it was). I imagine Zipp's data could be proprietary. And I imagine a lot of other data and testing could be proprietary. So it might be hard to find good data without some Good Samaritan testing or donated data from some company that decides in it's best interest to publicly release some information.


or... there is no data. no relevant test data, relevant being: side wind hits a rider, does that push the rider's steering wheel in the direction the wind is going? i think so. or does it push the wheel into the wind? i'm very skeptical of that. if my assumption is right, then, putting surface area behind the steering axis (but attached to the steerer) corrects for that? normalizes for that? or, putting surface area in front of the steerer normalizes for that? reduces that tendency? my sense tells me that behind the steerer is better. i'd need to see test data that demonstrates otherwise.

if there just is no relevant data, that is no sin. just, that is what has always turned out to be the case.

How about designing it so that the Cp is ON the steering axis? Sidewind then creates no steering torque.

Then you're just dealing with the bike being leaned by the side wind...which starts a turn away from the wind.

HEY! I know...what if we moved the Cp to a position that would initiate a turn INTO the wind at the same time? Where would we place the Cp relative to the wind then? ;-)

http://bikeblather.blogspot.com/
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Re: Josh and Slowman Debate Cp and Handling [Tom A.] [ In reply to ]
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Tom A. wrote:
Slowman wrote:
trail wrote:
Slowman wrote:
. it's that i don't think there's data. i have to be shown that there's data, and that this data is in some way analogous to real world riding.


Yes! So far we're dealing with Josh's memory from 10 years ago and Slowman's memory from 50 years ago (or whatever it was). I imagine Zipp's data could be proprietary. And I imagine a lot of other data and testing could be proprietary. So it might be hard to find good data without some Good Samaritan testing or donated data from some company that decides in it's best interest to publicly release some information.


or... there is no data. no relevant test data, relevant being: side wind hits a rider, does that push the rider's steering wheel in the direction the wind is going? i think so. or does it push the wheel into the wind? i'm very skeptical of that. if my assumption is right, then, putting surface area behind the steering axis (but attached to the steerer) corrects for that? normalizes for that? or, putting surface area in front of the steerer normalizes for that? reduces that tendency? my sense tells me that behind the steerer is better. i'd need to see test data that demonstrates otherwise.

if there just is no relevant data, that is no sin. just, that is what has always turned out to be the case.


How about designing it so that the Cp is ON the steering axis? Sidewind then creates no steering torque.

Then you're just dealing with the bike being leaned by the side wind...which starts a turn away from the wind.

HEY! I know...what if we moved the Cp to a position that would initiate a turn INTO the wind at the same time? Where would we place the Cp relative to the wind then? ;-)

yeah. what you're asking for is what i've been advocating we do. or at least investigate. there is a discrete center of pressure of just what's attached to, and pivots around, the steerer (it seems to me). so, THAT construct needs to have a neutral center of pressure, that sits right on the steering axis.

the question is, where does it typically sit now on our bikes? i think it sits in front of the steering axis. if so, then it seems intuitive to me to place surface area behind the steering axis, to neutralize the Cp. easier said than done i'm sure. but this is the nature of the debate we're having now in this thread. i think it's finally the right time to have it, because we've exhausted every other way to make a cool front end dealy bobber. this piece of paper we keep putting on the bottom of the stack has again risen to the top of the to-do pile.

Dan Empfield
aka Slowman
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Re: Josh and Slowman Debate Cp and Handling [Slowman] [ In reply to ]
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Slowman wrote:
Tom A. wrote:
Slowman wrote:
trail wrote:
Slowman wrote:
. it's that i don't think there's data. i have to be shown that there's data, and that this data is in some way analogous to real world riding.


Yes! So far we're dealing with Josh's memory from 10 years ago and Slowman's memory from 50 years ago (or whatever it was). I imagine Zipp's data could be proprietary. And I imagine a lot of other data and testing could be proprietary. So it might be hard to find good data without some Good Samaritan testing or donated data from some company that decides in it's best interest to publicly release some information.


or... there is no data. no relevant test data, relevant being: side wind hits a rider, does that push the rider's steering wheel in the direction the wind is going? i think so. or does it push the wheel into the wind? i'm very skeptical of that. if my assumption is right, then, putting surface area behind the steering axis (but attached to the steerer) corrects for that? normalizes for that? or, putting surface area in front of the steerer normalizes for that? reduces that tendency? my sense tells me that behind the steerer is better. i'd need to see test data that demonstrates otherwise.

if there just is no relevant data, that is no sin. just, that is what has always turned out to be the case.


How about designing it so that the Cp is ON the steering axis? Sidewind then creates no steering torque.

Then you're just dealing with the bike being leaned by the side wind...which starts a turn away from the wind.

HEY! I know...what if we moved the Cp to a position that would initiate a turn INTO the wind at the same time? Where would we place the Cp relative to the wind then? ;-)


yeah. what you're asking for is what i've been advocating we do. or at least investigate. there is a discrete center of pressure of just what's attached to, and pivots around, the steerer (it seems to me). so, THAT construct needs to have a neutral center of pressure, that sits right on the steering axis.

the question is, where does it typically sit now on our bikes? i think it sits in front of the steering axis. if so, then it seems intuitive to me to place surface area behind the steering axis, to neutralize the Cp. easier said than done i'm sure. but this is the nature of the debate we're having now in this thread. i think it's finally the right time to have it, because we've exhausted every other way to make a cool front end dealy bobber. this piece of paper we keep putting on the bottom of the stack has again risen to the top of the to-do pile.

Well...since in the other thread you've revealed yourself to be quite the daredevil (;-) I propose an experiment for you:

The next time you're out riding, find a nice flat area and ride along no-handed (you can do that, right?). While you're riding, then take one finger and VERY gently push forward on one end of the handlebar (thereby applying a steering torque in the direction of your push). Observe which way your bike turns due to that push. Report back on your findings, since that should inform you of where the Cp should be located to counteract crosswind induced lean-steer.

http://bikeblather.blogspot.com/
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Re: Josh and Slowman Debate Cp and Handling [Tom A.] [ In reply to ]
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Tom A. wrote:
Slowman wrote:
Tom A. wrote:
Slowman wrote:
trail wrote:
Slowman wrote:
. it's that i don't think there's data. i have to be shown that there's data, and that this data is in some way analogous to real world riding.


Yes! So far we're dealing with Josh's memory from 10 years ago and Slowman's memory from 50 years ago (or whatever it was). I imagine Zipp's data could be proprietary. And I imagine a lot of other data and testing could be proprietary. So it might be hard to find good data without some Good Samaritan testing or donated data from some company that decides in it's best interest to publicly release some information.


or... there is no data. no relevant test data, relevant being: side wind hits a rider, does that push the rider's steering wheel in the direction the wind is going? i think so. or does it push the wheel into the wind? i'm very skeptical of that. if my assumption is right, then, putting surface area behind the steering axis (but attached to the steerer) corrects for that? normalizes for that? or, putting surface area in front of the steerer normalizes for that? reduces that tendency? my sense tells me that behind the steerer is better. i'd need to see test data that demonstrates otherwise.

if there just is no relevant data, that is no sin. just, that is what has always turned out to be the case.


How about designing it so that the Cp is ON the steering axis? Sidewind then creates no steering torque.

Then you're just dealing with the bike being leaned by the side wind...which starts a turn away from the wind.

HEY! I know...what if we moved the Cp to a position that would initiate a turn INTO the wind at the same time? Where would we place the Cp relative to the wind then? ;-)


yeah. what you're asking for is what i've been advocating we do. or at least investigate. there is a discrete center of pressure of just what's attached to, and pivots around, the steerer (it seems to me). so, THAT construct needs to have a neutral center of pressure, that sits right on the steering axis.

the question is, where does it typically sit now on our bikes? i think it sits in front of the steering axis. if so, then it seems intuitive to me to place surface area behind the steering axis, to neutralize the Cp. easier said than done i'm sure. but this is the nature of the debate we're having now in this thread. i think it's finally the right time to have it, because we've exhausted every other way to make a cool front end dealy bobber. this piece of paper we keep putting on the bottom of the stack has again risen to the top of the to-do pile.


Well...since in the other thread you've revealed yourself to be quite the daredevil (;-) I propose an experiment for you:

The next time you're out riding, find a nice flat area and ride along no-handed (you can do that, right?). While you're riding, then take one finger and VERY gently push forward on one end of the handlebar (thereby applying a steering torque in the direction of your push). Observe which way your bike turns due to that push. Report back on your findings, since that should inform you of where the Cp should be located to counteract crosswind induced lean-steer.


thank you for counsel and suggestion.

Dan Empfield
aka Slowman
Last edited by: Slowman: Oct 18, 18 15:10
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Re: Josh and Slowman Debate Cp and Handling [Slowman] [ In reply to ]
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The effects of Cp position on handling don't need a fancy wind tunnel or analysis equipment. This could be figured out with 50 cents of duct tape, some cardboard and half an hour on a windy day.

Bodge up some additional fins on your forks and go for a ride, then report the results.
Version A: Fins behind the fork blade
Version B: Fins in front of the fork blade

(It gets fancier if you want to quantify the results and then go design your own bike, but to answer the question "should the Cp be in front of or behind the steering axis" you don't need fancy)
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Re: Josh and Slowman Debate Cp and Handling [MattyK] [ In reply to ]
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MattyK wrote:
The effects of Cp position on handling don't need a fancy wind tunnel or analysis equipment. This could be figured out with 50 cents of duct tape, some cardboard and half an hour on a windy day.

Bodge up some additional fins on your forks and go for a ride, then report the results.
Version A: Fins behind the fork blade
Version B: Fins in front of the fork blade

(It gets fancier if you want to quantify the results and then go design your own bike, but to answer the question "should the Cp be in front of or behind the steering axis" you don't need fancy)

exactly. my idea was something like a fly swatter, attached to the front axle, sticking directly back. different sized swatters. i might've just saved you the cost of a roll of duct tape. i think i mentioned this in several articles over the years. one of these days i'm going to get around to doing that.

Dan Empfield
aka Slowman
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Re: Josh and Slowman Debate Cp and Handling [Slowman] [ In reply to ]
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Slowman wrote:
exactly. my idea was something like a fly swatter, attached to the front axle, sticking directly back. different sized swatters. i might've just saved you the cost of a roll of duct tape. i think i mentioned this in several articles over the years. one of these days i'm going to get around to doing that.
Fly swatters! When I were a boy we used to dream o having fly swatters... We used to have a rolled up newspaper... (etc)
I wouldn't have thought that they would be stiff enough.

I was more thinking a vertical fin say 300mm long (up the fork blade) and maybe 50mm deep. A 300 x 100 mm corrugated cardboard piece folded lengthwise in a sharp V would be nice and stiff and not flop about in the breeze (especially when used as a leading edge).


Side note on the topic of understanding aero while on a budget: does anyone do wool tuft testing in the bike world? Surely it would be an effective way to visualise areas of turbulence and experiment with modifications. Sure you'd look pretty stupid with a helmet/skin suit/frame covered in dangling wool strands like some mutant scrotum, but it might be a way to learn where aero defects are?

Like this but with less beard:

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Re: Josh and Slowman Debate Cp and Handling [MattyK] [ In reply to ]
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MattyK wrote:
Side note on the topic of understanding aero while on a budget: does anyone do wool tuft testing in the bike world? Surely it would be an effective way to visualise areas of turbulence and experiment with modifications. Sure you'd look pretty stupid with a helmet/skin suit/frame covered in dangling wool strands like some mutant scrotum, but it might be a way to learn where aero defects are?

https://www.youtube.com/watch?v=66-_sSr_BDg
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