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Slowman
Jun 23, 08 17:58
Post #1 of 30 (2570 views)
Slowtwitch geometry calculator beta comments
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The geometry calculator referred to in the title is explained in
this
article. the calculator itself is
here
. perhaps it goes without saying, perhaps not, but this calculator relies on you (or your fitter) knowing the stack and reach of the bike you want/need.
one way to test out the accuracy of this calculator would be for you to go to our stack and reach database, find the stack and reach of the bike you're riding, and then put in all the other inputs exactly as they are geometrically represented on your existing bike, and see if our calculator faithfully generates the geometry of the bike you're riding.
of course, one element of this calculator that is sort of fun is playing around with the numbers. changing the seat angle, the chain stay, BB drop, whatever, and seeing what geometry you end up with.
the idea behind this calculator (if you're interested in knowing why we built it) is to make it a lot easier for your fitter or retailer to generate the geometry you need for the custom bike you want, if a custom is in your future. but, garbage in, garbage out. this calculator is easy for me to use, because i can tell you exactly what the stack and reach are for the bike you need based on the fit session you and i engage in. but, the delta between my fit session or jordan's, versus that of the tri bike fitter off the street, who can say?
the point is, the calculator is just a math engine. it's not going to tell you what's wrong with your sex life or how to find inner peace. it just crunches numbers.
Dan Empfield
aka Slowman
(This post was
edited
by Slowman on Jun 23, 08 18:47)
docfuel
Jun 23, 08 18:12
Post #2 of 30 (2544 views)
Re: Slowtwitch geometry calculator beta comments [Slowman]
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Is this one going to help with the Adamo users?
_________________
Dick
Take everything I say with a grain of salt. I know nothing.
bpq
Jun 23, 08 18:47
Post #3 of 30 (2503 views)
Re: Slowtwitch geometry calculator beta comments [Slowman]
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and riders of older frames, like say... a 2003 Felt S22?
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Vir prudens non contra ventum mingit - A wise man does not urinate against the wind.
Slowman
Jun 23, 08 18:59
Post #4 of 30 (2482 views)
Re: Slowtwitch geometry calculator beta comments [bpq]
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"
and riders of older frames, like say... a 2003 Felt S22?"
three hands, a carpenter's level, and a metric yardstick, and you can get stack and reach on that bike figured out.
Dan Empfield
aka Slowman
bpq
Jun 23, 08 19:03
Post #5 of 30 (2474 views)
Re: Slowtwitch geometry calculator beta comments [Slowman]
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three hands, a carpenter's level, and a metric yardstick, and you can get stack and reach on that bike figured out.
I've gotten pretty close with two hands, two plumb bobs, some masking tape and a level... but, it's always nice to get some afirmation online. :-)
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Vir prudens non contra ventum mingit - A wise man does not urinate against the wind.
ShawnF
Jun 24, 08 9:24
Post #6 of 30 (2173 views)
Re: Slowtwitch geometry calculator beta comments [Slowman]
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I input the fit coordinates from Tracy's fit session with Hank at Edge and the numbers your calculator spit out were different than what Guru sent back. However, they were very, very close. I would need to double-check a couple of the measurements to be sure I had all the inputs correct.
shawn
AVIA Running
AVIA on Facebook
Rahzel
Jun 24, 08 10:00
Post #7 of 30 (2156 views)
Re: Slowtwitch geometry calculator beta comments [Slowman]
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Edit: Oops!
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Pointy Helmet Coaching - currently accepting new athletes
(This post was
edited
by Rahzel on Jun 24, 08 10:32)
Tom A.
Jun 24, 08 10:08
Post #8 of 30 (2147 views)
Re: Slowtwitch geometry calculator beta comments [bpq]
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In Reply To:
three hands, a carpenter's level, and a metric yardstick, and you can get stack and reach on that bike figured out.
I've gotten pretty close with two hands, two plumb bobs, some masking tape and a level... but, it's always nice to get some afirmation online. :-)
I can do it with 2 hands, a 4ft. drywall square, and a metric tape measure :-)
Why do I feel like we're playing "Name That Tune"?? ;-)
Slowman
Jun 24, 08 10:08
Post #9 of 30 (2146 views)
Re: Slowtwitch geometry calculator beta comments [Rahzel]
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"
I think I may have found a bug in your engine. I plugged the following values into your calculator: Stack 47 (I have long arms and a steep position) Reach 52"
that would be a good set of metrics... if you were a chipmunk.
the very first sentence: "
All values are in millimeters!"
:-)
Dan Empfield
aka Slowman
Rahzel
Jun 24, 08 10:15
Post #10 of 30 (2140 views)
Re: Slowtwitch geometry calculator beta comments [Slowman]
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Sorry about that Dan! Replacing with "470" and "510" makes a lot more sense :)
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Pointy Helmet Coaching - currently accepting new athletes
Hid
Jun 24, 08 10:30
Post #11 of 30 (2130 views)
Re: Slowtwitch geometry calculator beta comments [Rahzel]
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Will check it out.
"Ride Fast & Have Fun"
- Steve Larsen
leggett24
Jun 25, 08 6:03
Post #12 of 30 (1869 views)
Re: Slowtwitch geometry calculator beta comments [Slowman]
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"
and riders of older frames, like say... a 2003 Felt S22?"
three hands, a carpenter's level, and a metric yardstick, and you can get stack and reach on that bike figured out.
Exactly how would you do this? I haven't found it in any of the articles.
I'd like to find the stack and reach on my Planet X.
AndyPeterson
Jun 25, 08 9:33
Post #13 of 30 (1821 views)
Re: Slowtwitch geometry calculator beta comments [Slowman]
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Dan - Seems a little off from my Elite T-class:
Input
Stack 520 Reach 410 Seat Angle 76.5 Head Tube Angle 72 Fork Offset 43 Fork Length 372 BB Drop 80 Chainstay 400 Rear Wheel 334 Headset Lower Stack 13.7 Wheel Size 700
Frame Measurements BB Height 254 Trail 63.3 Eff. Top Tube Length 534.8 Head Tube Length 90.9 Wheelbase 990.1 Front Center 603.5
Actual:
Top Tube 530mm (within 1/2 cm is pretty darn good)
Head Tube: 110mm (that's almost 2cm off - more of a problem)
Slowman
Jun 25, 08 11:03
Post #14 of 30 (1796 views)
Re: Slowtwitch geometry calculator beta comments [AndyPeterson]
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"
Head Tube: 110mm (that's almost 2cm off - more of a problem)"
i'm on the road right now, and don't have access to my parametric programs that would help me sort this out. i'll check it when i get back.
Dan Empfield
aka Slowman
Slowman
Jun 25, 08 11:06
Post #15 of 30 (1793 views)
Re: Slowtwitch geometry calculator beta comments [leggett24]
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"
Exactly how would you do this? I haven't found it in any of the articles."
stack and reach has been written about on slowtwitch more than any other single topic in the last 2 years. you'll find it under the bike fit tab accessed on the home page navbar.
if someone holds a carpenters level through the bb (horizontally) and you run a tape from the head tube top down to that level, that's stack. hold the level vertically thru the bb and run the tap horizontal to the center of the head tube top. that's reach.
Dan Empfield
aka Slowman
footwerx
Jun 25, 08 15:12
Post #16 of 30 (1719 views)
Re: Slowtwitch geometry calculator beta comments [AndyPeterson]
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could the headtube length difference be due to headset stack?
Slowman
Jun 26, 08 7:50
Post #17 of 30 (1620 views)
Re: Slowtwitch geometry calculator beta comments [footwerx]
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"
could the headtube length difference be due to headset stack?"
no. when i throw the numbers of his elite into my "offline" calculator, i get a stack and reach that is not exactly, but close, to what he says his bike's stack and reach is. i get a stack of 525mm, not a stack of 520mm. so, that makes up 5mm of the difference. but still, the online calculator ought to generate a head tube length of 110mm, and it's coming up with 95mm. that's if i'm using 13.7mm as headset
lower
stack.
this calculator is pretty much spot on in every calc with one exception: i know i've got a problem with head tubes. they're consistently coming up a few millimeters too short. once i solve this problem, i'll have it licked. they're just consistently a few millimeters off, always in the same direction, always a few millimeters shorter than the head tube length i'll really need. it's like the thing is measuring bottom to center instead of bottom to top. something like that.
Dan Empfield
aka Slowman
Tom A.
Jun 26, 08 16:32
Post #18 of 30 (1526 views)
Re: Slowtwitch geometry calculator beta comments [Slowman]
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In Reply To:
"
Exactly how would you do this? I haven't found it in any of the articles."
stack and reach has been written about on slowtwitch more than any other single topic in the last 2 years. you'll find it under the bike fit tab accessed on the home page navbar.
if someone holds a carpenters level through the bb (horizontally) and you run a tape from the head tube top down to that level, that's stack. hold the level vertically thru the bb and run the tap horizontal to the center of the head tube top. that's reach.
I like to measure "stack" by measuring to the ground and then just subtracting off the BB to ground measurement. No need for a level (or an extra person) that way...or even a perfectly level place for the bike to rest.
For "reach", I just take out my 4' drywall square and place the short "leg" on the ground and line up one edge of the long "leg" with the center of the BB. Then just measure from that edge forward.
But...we all have our own preferences I guess...plus it helps to have a drywall square, which everyone might not have...then again everyone might not have a carpenter's level either... :-)
BTW, you're out of town? Does that mean you won't be joining us Saturday morning in Lancaster?
cyclenutnz
Jun 26, 08 16:50
Post #19 of 30 (1523 views)
Re: Slowtwitch geometry calculator beta comments [Tom A.]
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But...we all have our own preferences I guess...plus it helps to have a drywall square, which everyone might not have...then again everyone might not have a carpenter's level either... :-)
I use a tape measure and a laser level - surely everyone has one of them...
Slowman
Jun 26, 08 17:04
Post #20 of 30 (1519 views)
Re: Slowtwitch geometry calculator beta comments [AndyPeterson]
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okay, did a little more checking. it turns out i had the 13.7 HS lower stack in the wrong place on my parametric program, i had 0.0 for that. when i put in 13.7, voila, i got a taller stack, like 540mm. if i place this in my online calculator we're debuting, i get the 110mm head tube.
so, simply put, i think your stack is off. i think the stack of your bike is really 540mm. when i take all the calcs you gave me and stick them in, what i get is 540mm and 403mm for stack and reach respectively.
again, if you have a 53.5cm top tube, 72.5° head angle, 43mm offset, 76.5° seat angle, 40mm chainstay, 110mm head tube, 80mm of BB drop, external chris king headset, you get a stack of 540mm and a reach of 403mm. those of you who have framebuilding programs, you can check this out yourself.
now, in your case, andy, if you really think you have a stack of 520mm, perhaps you've got a bad value for your BB drop. if your BB drop was 60mm instead of 80mm, you'd have that 110mm head tube with a stack of 520mm.
Dan Empfield
aka Slowman
Slowman
Jun 26, 08 17:06
Post #21 of 30 (1518 views)
Re: Slowtwitch geometry calculator beta comments [Tom A.]
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"
BTW, you're out of town? Does that mean you won't be joining us Saturday morning in Lancaster?"
i'm back in town. i was out searching for clear air. believe it or not, i ran for an hour yesterday morning on a road at 10,000' of elevation, in the white mountains. still no clear air, even up there. so, wtf, i just came back home.
Dan Empfield
aka Slowman
WryMouth
Jun 26, 08 19:48
Post #22 of 30 (1492 views)
Re: Slowtwitch geometry calculator beta comments [Slowman]
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Now all we need is a program that will take our geometry and match it with a bike.
When it's good, it's good. When it's bad, you suffer.
Dan
cheyou
Jun 28, 08 17:03
Post #23 of 30 (1299 views)
Re: Slowtwitch geometry calculator beta comments [cyclenutnz]
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laser is the way to go (-: (David White line laser)
I don't drink enough so they won't sell me a rockers square.
you know them rockers (-;
Thom
Reach the Beach leg 8,20,32
ohiost90
Jun 28, 08 18:45
Post #24 of 30 (1284 views)
Re: Slowtwitch geometry calculator beta comments [Slowman]
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looks interesting but I was hoping for a calc, when i opened the thread, that takes input of leg, torso, arm, etc measurments and comes up with a range of stack/reach/top tube lenghts/ etc recomendations.
Rappstar
Jun 28, 08 20:19
Post #25 of 30 (1264 views)
Re: Slowtwitch geometry calculator beta comments [ohiost90]
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looks interesting but I was hoping for a calc, when i opened the thread, that takes input of leg, torso, arm, etc measurments and comes up with a range of stack/reach/top tube lenghts/ etc recomendations.
Except such a thing would never work. There is nothing that can tell you whether you'll be happy riding 78deg or 80deg (for example) of seat tube angle. There is also nothing that will tell you whether you'll be happy with 103 or 97 degrees of hip angle. Mostly it's a function of STA, since small stack and reach measurement differences can mean huge differences in bike sizes (or frames that work).
Such a "cookie cutter" type calculator would be totally antithetical to what Dan and I believe in terms of bike fit. Such "calculators" should be banned.
"BAM!" - Larry Williams
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