Shifter adjust geo question

[kgreene10]

Is there a rule of thumb for the extra drop you get from pushing the shifters 1mm further forward on the bars?

I realize that the curve radius is different across bars and that it depends where the levers are on the curve to begin with. Nevertheless, for the typical lever positions and for common compact bars, is there a ballpark rule of thumb?

I ask because it’s pretty easy to compare the current bike fit to possible new bikes using geo charts and some trigonometry in Excel. Inevitably, the ideal for falls between the available increments supplied by fixed length stems and bars. So then it’s about playing with shifter position. There’s probably enough wiggle room there to make things work, but if there’s a rule of thumb to add to my calculations, I would like to use it. Anal? Well, yes, but bikes are really expensive and so why not use all the available info?

[Mark McM]

Originally Posted by kgreene10

Is there a rule of thumb for the extra drop you get from pushing the shifters 1mm further forward on the bars?

I realize that the curve radius is different across bars and that it depends where the levers are on the curve to begin with. Nevertheless, for the typical lever positions and for common compact bars, is there a ballpark rule of thumb?

I ask because it’s pretty easy to compare the current bike fit to possible new bikes using geo charts and some trigonometry in Excel. Inevitably, the ideal for falls between the available increments supplied by fixed length stems and bars. So then it’s about playing with shifter position. There’s probably enough wiggle room there to make things work, but if there’s a rule of thumb to add to my calculations, I would like to use it. Anal? Well, yes, but bikes are really expensive and so why not use all the available info?

Sadly, no. As you say, it depends largely on the curve shape, and where on the curve the shifters are (not to mention also the hood size/shape). If the levers were all the way at the top of the curve, shifting the levers would result in only reach changes, and not height changes; if the levers were at the forward most part of the curve, shifting the levers would result only in height changes, and not reach changes. Anywhere else, and there will be combination of reach and height changes - but the proportion between those changes will depend on many variables.

While reach changes may only be adjusted in increments of 10 mm or so, height changes (via stem spacers) are adjustable in increments of 1 mm, and I can't imagine why you'd need finer resolution than that.) So, you could adjust the shifter position for fine precision in reach, and then select stem spacers as necessary to compensate for any height changes.

[Kontact]

Originally Posted by kgreene10

Is there a rule of thumb for the extra drop you get from pushing the shifters 1mm further forward on the bars?

What does this mean? Shifters are already up against the bars - they can't get any closer. Are you referring to sliding them up and down the bar's curve, or tilting them in toward center?

Stems can be had in half sizes - 95mm, etc. And different bars have different reaches. Just by playing with different combinations you could get down to 2mm increments. And then you can address the rest with with bar angle.


And, as long as it is only 2-3mm, there is nothing wrong with addressing a very small amount of reach with saddle set back. Though I would always vote for moving the saddle back and using the shorter stem than moving the saddle forward, but either way a very small set back change shouldn't affect pelvic angle much, but it will nudge the bars your way.

But if it is 5mm, buy a new stem.


Overall, any bike that is reasonably close to what you need for a fit can be made to fit. But even the most precisely cloned fit will still have variations that you feel or think you feel. So in the end every bike's final fit adjustment should be via actual riding.

[John H.]

The curves on bars vary so much from bar to bar that there is no correlation between moving the shifter and changing reach or hood height from bar to bar.
This is also compounded by the angle that you run the bars themselves.

Many "short reach" bars are not even really short reach. When you set the bars to be flattish on top- Hoods end up out at the apex of the curve and are effectively longer in terms of reach.

A newer bar that I like is the Zipp SL70 in carbon. The variable radius allows you to get a nice hood position with a short effective reach.

Lastly, Shimano 685/785 levers are larger and longer than their rim brake levers- This adds to the reach.
Thankfully the new Dura-Ace level Hydro (and hopefully Ultegra) is shorter and more like the rim brake levers in terms of size.

Originally Posted by kgreene10

Is there a rule of thumb for the extra drop you get from pushing the shifters 1mm further forward on the bars?

I realize that the curve radius is different across bars and that it depends where the levers are on the curve to begin with. Nevertheless, for the typical lever positions and for common compact bars, is there a ballpark rule of thumb?

I ask because it’s pretty easy to compare the current bike fit to possible new bikes using geo charts and some trigonometry in Excel. Inevitably, the ideal for falls between the available increments supplied by fixed length stems and bars. So then it’s about playing with shifter position. There’s probably enough wiggle room there to make things work, but if there’s a rule of thumb to add to my calculations, I would like to use it. Anal? Well, yes, but bikes are really expensive and so why not use all the available info?

[kgreene10]

All righty. This is about what I figured, but was sorta hoping someone even geekier than I had determined the range of reach:drop changes over the usable portion of the most commonly employed contemporary road bars. Not to be.

The point about micro adjustments is well taken but the move to integrated bars and stems fouls it all up. I’ve been wrestling with a Madone 9 for some time now - no bar or stem replacements (except with other stock integrated sizes) and no bar angle adjustments, so shifter placement becomes your major weapon in tuning fit. Mine remains sorely outa tune.

[Kontact]

Originally Posted by kgreene10

All righty. This is about what I figured, but was sorta hoping someone even geekier than I had determined the range of reach:drop changes over the usable portion of the most commonly employed contemporary road bars. Not to be.

The point about micro adjustments is well taken but the move to integrated bars and stems fouls it all up. I’ve been wrestling with a Madone 9 for some time now - no bar or stem replacements (except with other stock integrated sizes) and no bar angle adjustments, so shifter placement becomes your major weapon in tuning fit. Mine remains sorely outa tune.

The Madone bar/stem is a nasty piece of gear - super deep drops and 90mm being the shortest stem length. Good luck!

[kgreene10]

Originally Posted by Kontact

The Madone bar/stem is a nasty piece of gear - super deep drops and 90mm being the shortest stem length. Good luck!

Bars on the Madone 9 aren’t so deep - 123mm - but reach is a significant 93mm.

[Kontact]

Originally Posted by kgreene10

Bars on the Madone 9 aren’t so deep - 123mm - but reach is a significant 93mm.

Excuse me - I meant reach, not depth. For shorter riders these bars really create problems.

[kgreene10]

Originally Posted by Kontact

Excuse me - I meant reach, not depth. For shorter riders these bars really create problems.

Agreed. Very looooong.

[Mark McM]

Originally Posted by kgreene10

The point about micro adjustments is well taken but the move to integrated bars and stems fouls it all up. I’ve been wrestling with a Madone 9 for some time now - no bar or stem replacements (except with other stock integrated sizes) and no bar angle adjustments, so shifter placement becomes your major weapon in tuning fit. Mine remains sorely outa tune.

The only integrated bars/stems that make sense are the one that team Sky uses - and only because they are each custom made for a particular rider.

Putting the shape of the curve aside, there are 3 different dimensions in the bars and stem that affect fit - reach, width, and drop. It is not practical to manufacture all combinations of these variables to fit everyone's needs.

Take me for example - I typically use narrow bars, but a long bar/stem reach. I can easily get narrow bars and long stems separately. but when I looked into integrated bar/stems, I found that the ones with narrow bars all had short reaches and the ones with long reaches all had wide bars. Maybe that's fine if you happen to be in the center of the bell curve, but what if you are one of those poor suckers that deviates for "average"?

[John H.]

You could try to get one of these? Picture 21-

http://www.cyclingnews.com/features/...-race-gallery/