Are you imagining something like this?


Its a one position rig if your bb lines up with the green/blue crosshairs, a dual jig if your bb does not line up (line up bb with green for seat, than line up bb with blue for extensions)

yeah, that's it. here's what i wrote up earlier this morning, a riff off of tom's drawing. in this case, the forward line is built off the saddle height +5cm motif. yours is built off tom's idea of 66cm + the angled line. i guess i would just like to plot tom's line, via how you did it, and then just start checking sampled saddle heights and see if it makes sense.

---

Dan Empfield
aka Slowman

luxurious is in the eye of the beholder I guess. cuz if I use saddle height plus 5, I lose 2 cm of extension from current rules and that would be at saddle height, but bars are not at saddle height, so I would lose another 7 cm from that and basically be limited to 75+5-7=73cm in front of BB to extension tips

the 66 plus 78 deg would give me 80cm to same point and would be preferred

I would not change saddle rule for split nose, as some of use don't like those and you would then be basically prescribing them, just as current rules currently prescribe di2 if you want to keep the same reach you had with mechanical.

So the 66cm + angled line equation would look something like this:

Saddle tip to Extension Tip = Saddle tip to BB + 66cm + [Extension height above BB / tan(78)]

or if saddle tip is on the 78 degree plus 17cm wire it would look like this:

Saddle tip to Extension Tip = 66cm + [Extension height above BB / tan(66)]

I'm a bit new to this, but I've thought about the 17cm (or whatever that might be) piece before, which is for 1.3.013. I don't know if folks will agree, but it seems to me that by using 17cm no matter what the saddle height, the shorter-legged athlete can gain more effective seat tube angle than Mr Lankypants. I'm not convinced that the 17cm shouldn't vary subject to effective saddle height. I'll try and explain...

Take an average Joe like me with effective saddle height 741mm. I'll use that number randomly as the hypotenuse of a right-angle triangle who's angle of 76 degrees is from the horizontal (or adjacent) is centred at the bottom bracket. These numbers will give you an adjacent (distance along the horizontal to the vertical line that intersects with the hypotenuse..) of 179mm.


I don't know if it's obvious from the schematic, but the 170mm forward offset has a greater impact on the effective seat tube angle for lower saddle heights (or hypotenuseseses), and a lesser impact for higher saddle heights. If you imagine a point a little bit back from the saddle nose where you can realistically rest your sit bones, say 7cm back so 100mm forward of your 76 deg line. As you reduce the effective saddle height that position on the saddle generates a steeper and steeper angle. I did the math...

For me, as above a hypotenuse of 741mm with 76 degree angle generates an adjacent of 179mm. If you consider the above, and deduct, say, 100mm from that 179mm you have a new adjacent of 79mm. So your new effective seat tube angle is based on a hypotenuse of 741mm (unchanged, your legs haven't grown) and an adjacent of 79mm.


So for x = cos-1(adj/hyp) this gives a new effective seat tube angle for me of about 83.9 degrees.

Now if I did some similar maths based on somebody with shorter legs than me (and there aren't many), say 641mm effective saddle height, 17cm forward offset gets them an effective seat tube angle of 85 degrees. So I don't know whether the end game is to limit the effective seat tube angle, but that rule doesn't do that. You can imagine that were somebody diddy enough they could get there bum ahead of the bottom bracket.

So perhaps the thing to do is draw another line which determines what the forward offset should be at different saddle heights? I don't think it would be that difficult, you determine what the steepest effective seat tube angle is you want, then draw a parallel line to this offset by an amount equal to whatever you decide the unusable saddle tip length should be. A bit like this, in red.


So your harp becomes more of a narrow right-angled trapezoid.

Whaddya reckon? Did that make any sense at all? Apols, your question is more about 1.3.023, but here y'go anyways.

Rich.

You're right, as of now it penalizes rider with a long torso in absolute terms (i.e. in inches/cm), whereas using the saddle height+5cm would penalize riders with a long torso in relative terms (i.e. compared to their leg length).

An idea could be to use your suggestion of your angled line, but instead of using the extension height as the point for determining the extension limit saddle height could be used instead. I've used fierceSun's sketch to try and show it:




This would then not penalize riders with more drop or riders with straight extensions instead of ski bends. Each centrimetre you increase or decrease your saddle height (measured vertically) will then also only change your extension limit 0.2-0.25 cm (depending on the exact angle chosen). This would of course complicate the jig a bit.


Another suggestion that would yield similar results with regards to lessening the effect of saddle height on extension limit would simply be to say extension limit should be e.g. 65 cm + 0.2*saddle height - but this would probably not be as easy to put into a jig.

how much are we talking about here REALLY? because by my calcs we're fussing over a few millimeters. assume 2 people, same saddle size, one with 3cm of drop more than the other one. what are we really talking about here, in total allowable cockpit?

---

Dan Empfield
aka Slowman

If the angle is 78 degrees I get 21%, i.e. 0.21 cm more allowed extension if you have 1 cm less drop. If talking about straight extensions vs. ski bends (which can easily be up to 10 cm in vertical height including shifters) this means 2.1 cm more reach for the one with ski bends.

the assumption of 3 cm is the problem. some folks might has 5cm drop other 20, at same height. also as Martin points out, the difference between straight and ski bends can add 10 cm difference and each cm is 0.2cm change in reach. so take 10cm and ski bends vs 20cm and straight and you could be looking at a 20cm difference in measuring points which would be a 4cm shorter cockpit. if you have to shorter you ride by 4 cm, likely you wont be happy

I like MTM's jig addition. a sliding bar that drop to top of saddle nose and then has a vertical arm at extension. simple sliding form should only take a few seconds to measure a bike as the horizontal arm would slide out at saddle end

"the assumption of 3 cm is the problem. some folks might has 5cm drop other 20, at same height"

remember, this isn't tri, these are UCI rules. i think for the same height saddle, 3cm or 4cm is huge. however you do bring up a great point about ski bends versus straight bars.

to me, the jig addition would require a framing square with a level. maybe you just say that the measure is taken at the height of the pads, rather than a saddle. that way you probably just need a relatively short - 12" or 18" - level.

---

Dan Empfield
aka Slowman

quandary, I mean there are folks my height that ride with 8-10cm more drop than I do for uci positions. they even ride same bike, but 1-2 sizes smaller. this is anecdotal and likely not the folks you are targeting.

the extensions point was MTM's, but yes very valid.

can't we make a sliding arm that is not dependent on the angle of the floor the jig is on?

personally I am against anything making my reach shorter or pushing my saddle back :)

Seems complicated. Nose even with BB and extensions not past front of wheel.
Done and done.

Precisely, that is why I think it should be measured to the end of the shifter body (the fixed position component) - that way there is no judgement of the centre of a bolt. Nor is there a penalty for not having Di2

In the workings I linked to I made allowance for the variation in torso length but didn't really apply that to what I wrote above as I was trying to relate the proposal to the old rule.

The Dimensions tab of this google sheet allows you to play around with options for fixed and angular reach and see what it does.

For the "Seat Height +5cm" Extension limit, why not just have a painted line jig:



It could be painted up with small increments (say 2.5cm), which ever line you are below, you have to fit that extension limit. Just roll the bike up so the saddle nose is at the start of the line.

"Seems complicated. Nose even with BB and extensions not past front of wheel.
Done and done."

i think you should go back and read the thread.

---

Dan Empfield
aka Slowman

I read it the first time in 2007 and read the first page again before posting. In your experience of all the fits you have done, how many ideal positions would fall outside 0 bb (even with snub nosed saddle) and extensions not in front of the front wheel. How many had ideal fits that would not be legal under USAT rules?

You yourself said in the second or third post it should be simple and easy to follow rule. You don't need a fancy jig to measure right angles.

..

"how many ideal positions would fall outside 0 bb (even with snub nosed saddle) and extensions not in front of the front wheel?"

a ton. all the ladies - everyone under 5'6" - would violate 1.3.013, all the men - everybody over 6' - would violate 1.3.023. yes, you could get all the ladies to meet the rule if you mandated that they use a split nose saddle. you would basically mandate the use of a saddle of that nature.

would they violate USAT's rule? no. but the UCI would see USAT's rule as over-expansive, which it is. USAT assumes that everybody should get the rules that the farthest outlier would need, and that means most people get a more expansive rule than they'll need.

the goal is to give the UCI a set of rules that are not over-expansive, while not being unfair to people just because of their stature.

---

Dan Empfield
aka Slowman

How about defining the reach to the back of the aerobar pad (and having a limitation on pad length). That way the issue of shifter and extension shape is avoided.
And we only have to worry about variation in torso length, not forearms as well.

I just had a quick play on my bike with defining the centre of an arc at the BB with radius defined by the length to the tip of the saddle.
Then the rear of the pads must fall within that arc (maybe with an extra 5cm added to radius). That way you're not penalised by being low.
It's not so good for long and high, but that is a very rare situation in serious TT.

So the jig would have the STA limit and a swivel arm with a pointer (much like a park DAG-2). It does make the jig more complicated but any system that is fairer than current will do that.
Snub saddles would still give a slight advantage but it would be no where near as compelling as it is now.

Do you think the USAT rules allow for an unfair advantage?
We don't seem to see any Pros with what I'd consider extreme positions.

http://www.slowtwitch.com/News/2013_Kona_Top_15_Men_Bike_4071.html


http://www.slowtwitch.com/News/_13_Kona_Top_16_Women_Bike_4070.html


The women all look to be 0 bb or less to me from those picks, but you would know better.
The men are all well behind the front of the wheel for extensions.
Of course, that is Ironman where you need to be comfortable. I don't see extreme positions in shorter races either though.


..

Checking in quickly here on a break...

I'm not following, I think what dogmile was saying about saddle position is what I was saying earlier. Allow the nose of the saddle to be even with the BB...how does that make women under 5'6" violate 1.3.013? That really IS the most logical solution. Boom. Done.

Also...I've been thinking we (and the UCI) might be focusing on the wrong thing in regards to 1.3.023. Wouldn't it make MORE sense to control pad position as opposed to extension location? The pads are the TRUE support location when using aerobars, not the extension (despite what they've claimed in the past). [edit: I see above that cyclenutnz and I are thinking on the same lines]

How about just using the "box" outlined in 1.3.022 (or a modification) and then say that in TTs that's the limit of pad front edge location as well? Extensions then can be whatever the rider wants them to be.

I know...I'm getting more into the "why" of the situation, rather than the "how"...but, if you want simple, fair, and enforceable, it REALLY needs to start from there. Anything else is going to be a kludge.

---

http://bikeblather.blogspot.com/

"Allow the nose of the saddle to be even with the BB...how does that make women under 5'6" violate 1.3.013?"

because they need it forward of the BB. as long as you have an X/Y rule solution you have a solution that doesn't scale. now, if you want ONLY a bar end rule, and that in itself constrains the forward movement of the saddle, okay. i can see the logic in that. but that rule as well must scale. one, the other, or both rules must scale. whatever rule you have must scale.

---

Dan Empfield
aka Slowman

back of the pad: you and tom a have both brought that up. i would have no problem with that. in fact, instead of back of the pad with a pad length limit, why not to the front of the pad? just, remember, you revisit the whole obree thing. they said, as i recall, you can't allow your arms to touch the bike. so he said, fine, they won't touch the bike. it did not limit the use of the superman. the only thing that limited its use was a limit to the extensions.

---

Dan Empfield
aka Slowman

Aaah...got it...I was silly and forgot about the offset forward of the angled line through the BB...DOH! That's what I get for a "hit and run" check in post ;-)

---

http://bikeblather.blogspot.com/

IIRC, the verbiage about the arm rests not being the supports in the aero position has been taken out...at least I couldn't find it the last time I looked through the rule book.

If you have a reasonable limit on the forward and upward locations of the pads, that will limit any "Superman", no? Like I said above, a modification of the already existing "handlebar location box" in 1.3.022 would do.

Besides, I think they should revisit the whole "ban the Superman position" sillyness anyway ;-)

---

http://bikeblather.blogspot.com/

I agree that the pads are better place to measure than the shifters. Also we should measure the front of the pads, that way people can run what ever length of pad that they want.

The only issue is do you need to define what the pad is? Could you measure the "pad", but then the rider could just not use the pad that was measured and use some other surface to rest their forearms? Of course I guess if someone really wanted to push the rules, they could also have the rider ride on some other surface than the "saddle" that was measured.