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An Odd, But Significant, Difference


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...between two very similar derailleurs - the Ultegra "long" and the GRX one.   Both use a clutch, but they are slightly different in "total" capacity and also in max front.  Seems the GRX is going for a slightly larger max front difference (which I would have thought was a front derailleur consideration), but at the expense of a slightly lower total capacity.  I'd love to be able to swap the GRX off the gravel bike and onto the road bike in rare circumstances where a 11-34 cassette was desired over my current 11-28, but it seems like that would be one tooth too many since the road bike is a 50/34, so the total capacity would be a 39 (Ultegra), not an 38 (GRX).   I wonder if the "38" is a hard value or could be really higher than that, but overly cautious?  Supposedly, even my current road RD - rated at max of 28 - is actually easily adjusted to run fine up to 32 teeth cassettes.  Likewise, what's up with there being no 12-34 11sp road/gravel cassette from Shimano?  Seems a min/max top sprocket of 11T is nuts.

Or maybe I'm just reading & interpreting this all wrong :scratchhead:  Wouldn't be the first time.

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I've always had the sense that Shimano specs lean more to an apparent quality of shift. I don't buy that much stuff but I always say figure out what you need and buy it. So the question becomes, What do you need?

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1 hour ago, donkpow said:

I've always had the sense that Shimano specs lean more to an apparent quality of shift. I don't buy that much stuff but I always say figure out what you need and buy it. So the question becomes, What do you need?

It's more a "what do I have" and "can I get to where I want" situation.

What I have is a road bike with a "short" rear DR and compact crank - so right now a 50/34 front, 11-28 11sp rear - and a gravel bike with a "long" GRX rear DR and a gravel compact crank - so a 48/31 front, 11-34 rear.

My thinking (hope) was I could - if need be for a very hilly road ride - swap on JUST the GRX long DR and bigger cassette to the road bike giving a very nice extra set of granny gears without having to go to a front crank swap as well to make the "total capacity" fit.

I think there is wiggle room in Shimano's specs since the short DR I have can run a 32 teeth cog, but may be irrelevant to my idea that the 11-34 cassette would be my goal and would most definitely require the Ultregra RX (within spec) or the GRX (just out of spec - seemingly).

IOW, I'm not looking to buy an "extra" DR, but if the gravel bikes DR can be swapped relatively easily with the current road DR, that's optimal - ie no new cost except a longer chain.

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Quality of shifting will suffer. Or at least the quality and precision that Shimano tries to build in. I've thrown plenty of junk into a drivetrain. What it amounts to for me is a certain degree of adaptation on my part. Of course, the majority of my exploration has been with friction shifting components. I've gone as far as building a custom hanger that dropped the derailleur down so I could use bigger cogs.

How does electronic shifting compare to mechanical shifting?

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2 hours ago, donkpow said:

How does electronic shifting compare to mechanical shifting?

Better in every way imaginable or quantifiable :)  However, mechanical still is 99% as good.

But put simply, in almost five years of Di2, I can't remember a mis-shift.  I have hit the up lever instead of the down, but I've done that on mechanical too.  And, while this is very dependent on bike build and adjustment, I have never dropped a chain due to a shift from big ring to little ring on Di2, but used to have to be careful with my mechanical set-up going from big to little.  But that's an "unknown" as it is two different bikes and one was DA 10sp mech vs DA 11sp Di2 - so could have just been a slightly maladjusted mech front derailleur setting.

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59 minutes ago, Razors Edge said:

Better in every way imaginable or quantifiable :)  However, mechanical still is 99% as good.

I don't know if we have a basis of friction shifting in our discussion. I guess my question should be is, How forgiving does the Di2 system feel? There are some adjustments even with indexed manual shifting that can be exploited to help it operate outside its narrow intended operational design. 

Now we are looking at skill on three levels; operational, adjustment,  and mechanical/electrical.

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2 minutes ago, donkpow said:

I don't know if we have a basis of friction shifting in our discussion. I guess my question should be is, How forgiving does the Di2 system feel? There are some adjustments even with indexed manual shifting that can be exploited to help it operate outside its narrow intended operational design. 

Now we are looking at skill on three levels; operational, adjustment,  and mechanical/electrical.

I think Di2 is identical to mech except instead of using a mechanical pull to advance/release a pawl(s) equal to a shift, it uses a more precise servo.  On the derailleur themselves, you still have the ability to adjust the alignment of the derailleur pulleys over the cassette cogs (electronically, not using barrel adjusters), and then there are physical stops H & L screws, and then the B screw that seems to be the one folks "max out" to achieve using the not-to-spec 11-32 cassettes with the short rear DR. 

So, I think where index trumps all is in the near infinite micro adjustments one can make, but where Di2 wins is that there are never needs for micro adjustments.  Of course, that changes if working outside "the box" and outside spec.

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On 1/22/2021 at 12:53 PM, Razors Edge said:

I think Di2 is identical to mech except instead of using a mechanical pull to advance/release a pawl(s) equal to a shift, it uses a more precise servo.  On the derailleur themselves, you still have the ability to adjust the alignment of the derailleur pulleys over the cassette cogs (electronically, not using barrel adjusters), and then there are physical stops H & L screws, and then the B screw that seems to be the one folks "max out" to achieve using the not-to-spec 11-32 cassettes with the short rear DR. 

So, I think where index trumps all is in the near infinite micro adjustments one can make, but where Di2 wins is that there are never needs for micro adjustments.  Of course, that changes if working outside "the box" and outside spec.

Trying to understand this thread makes my head hurt. 15 years ago I wanted a lower gear on my road bike. It had a 12-28 cassette so I bought an 11-30 cassette online. It almost worked. I could get the bike shifted into the 30 tooth gear for climbing but it was so maxed out it made a loud clicky noise the whole climb. Velobro back in the love forum told me I needed a long cage derailleur like they use on mountain bikes. I found one online and posted the link. He told me that should be perfect and it was. I did the all hills century that Saturday with no issues. That is the only time I changed gearing on any of my bikes. My touring bike came with the gearing I needed for Mercer county hills.

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25 minutes ago, Longjohn said:

Trying to understand this thread makes my head hurt. 15 years ago I wanted a lower gear on my road bike. It had a 12-28 cassette so I bought an 11-30 cassette online. It almost worked. I could get the bike shifted into the 30 tooth gear for climbing but it was so maxed out it made a loud clicky noise the whole climb. Velobro back in the love forum told me I needed a long cage derailleur like they use on mountain bikes. I found one online and posted the link. He told me that should be perfect and it was. I did the all hills century that Saturday with no issues. That is the only time I changed gearing on any of my bikes. My touring bike came with the gearing I needed for Mercer county hills.

Good to hear that velobro helped you out!  My bike barely has a low enough gear for me to get up the steepest hills here but I am not changing a thing!  It would be nice to have a touch lower gear though.

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1 hour ago, Longjohn said:

Trying to understand this thread makes my head hurt.

The bicycle industry is trying to sell like single chainrings instead of 2 or 3. Then there are people that are leaning towards riding their bike on gravel roads.  I've always found the triple crank does a good job and is not that hard to shift.

Talking about the "B" tension screw adjustment:

"If the angle adjuster is set too loose, the jockey pulley will bump into the largest sprocket when the bicycle is in the lowest gear (large rear, small front). "

https://www.sheldonbrown.com/derailer-adjustment.html

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1 hour ago, Longjohn said:

I could get the bike shifted into the 30 tooth gear for climbing but it was so maxed out it made a loud clicky noise the whole climb. Velobro back in the love forum told me I needed a long cage derailleur like they use on mountain bikes.

 

50 minutes ago, Philander Seabury said:

It would be nice to have a touch lower gear though.

Watching the Phil Gaimon Everesting video where he just spins up 15+% using MTB gearing (and 300+ watts) got me thinking about it.  I don't think for normal riding it makes sense to go beyond my 50/34 and 11-28, since that gives me plenty for regular rides and climbs - just not high cadence sort of climbing.  I've done plenty of long sustained climbs and pre-11sp, I was on a 50/36 with a 12-27, and that worked fine for Alpe d'Huez or Galibier or my local Skyline loops.  However, when I got the 11sp with one extra low combination (34/28 combo) and one extra high combo (50/11 combo), it was EASY to appreciate the wider set of options, and makes me appreciate the 12 speed future and the related super-wide range of the tiny "10" and the giant "34" (or bigger) options :)  But that seems to come at a cost derailleur wise with 11sp - for now - so I was just spitballing a "what's needed beyond what I already have" sort of thing and using the least amount of mixing and matching.

If it is as simple as throw on the GRX long DR, swap on the 11-34 cassette, and add a longer chain, that seems fantastic as an option for something like the Garrett County Gran Fondo or SW's assault up Mt Washington.  All in, that sort of "simple swap" would be like an hour of work and with tools I have readily available.  But if it then heads into a "might as well swap the crank, adjust the front DR, maybe also do...", it becomes a more royal PITA.

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1 hour ago, Razors Edge said:

 

Watching the Phil Gaimon Everesting video where he just spins up 15+% using MTB gearing (and 300+ watts) got me thinking about it.  I don't think for normal riding it makes sense to go beyond my 50/34 and 11-28, since that gives me plenty for regular rides and climbs - just not high cadence sort of climbing.  I've done plenty of long sustained climbs and pre-11sp, I was on a 50/36 with a 12-27, and that worked fine for Alpe d'Huez or Galibier or my local Skyline loops.  However, when I got the 11sp with one extra low combination (34/28 combo) and one extra high combo (50/11 combo), it was EASY to appreciate the wider set of options, and makes me appreciate the 12 speed future and the related super-wide range of the tiny "10" and the giant "34" (or bigger) options :)  But that seems to come at a cost derailleur wise with 11sp - for now - so I was just spitballing a "what's needed beyond what I already have" sort of thing and using the least amount of mixing and matching.

If it is as simple as throw on the GRX long DR, swap on the 11-34 cassette, and add a longer chain, that seems fantastic as an option for something like the Garrett County Gran Fondo or SW's assault up Mt Washington.  All in, that sort of "simple swap" would be like an hour of work and with tools I have readily available.  But if it then heads into a "might as well swap the crank, adjust the front DR, maybe also do...", it becomes a more royal PITA.

Could you repeat that for me? I think I must have missed something.

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On 1/21/2021 at 7:20 AM, Razors Edge said:

...between two very similar derailleurs - the Ultegra "long" and the GRX one.   Both use a clutch, but they are slightly different in "total" capacity and also in max front.  Seems the GRX is going for a slightly larger max front difference (which I would have thought was a front derailleur consideration), but at the expense of a slightly lower total capacity.  I'd love to be able to swap the GRX off the gravel bike and onto the road bike in rare circumstances where a 11-34 cassette was desired over my current 11-28, but it seems like that would be one tooth too many since the road bike is a 50/34, so the total capacity would be a 39 (Ultegra), not an 38 (GRX).   I wonder if the "38" is a hard value or could be really higher than that, but overly cautious?  Supposedly, even my current road RD - rated at max of 28 - is actually easily adjusted to run fine up to 32 teeth cassettes.  Likewise, what's up with there being no 12-34 11sp road/gravel cassette from Shimano?  Seems a min/max top sprocket of 11T is nuts.

Or maybe I'm just reading & interpreting this all wrong :scratchhead:  Wouldn't be the first time.

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FWiW  I’m running the Ultegra RX mechanical with a low gear of 36 X 34 on my cross bike.  It had CX cranks so 46/36 and I have a 11-34 cassette.  I don’t think I have used the granny on the road but have many times on steep dirt pitches.  
 

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50 minutes ago, ChrisL said:

FWiW  I’m running the Ultegra RX mechanical with a low gear of 36 X 34 on my cross bike.  It had CX cranks so 46/36 and I have a 11-34 cassette.  I don’t think I have used the granny on the road but have many times on steep dirt pitches.  
 

My Diverge has the super easy 31 front, 34 rear that lets me sit to keep weight over the back tire on steep but slippery climbs. I use it often. :)  The Tarmac has the less (but still relatively) easy 34/28 combination, and on paved surfaces, I can generally stand and ride up almost anything I encounter.  But this sort of "what if" exercise using stuff I own to create a set-up where I can pretend to be able to climb like Phil G. just gets me wondering about why it is not just very simple plug and play process.

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1 hour ago, Razors Edge said:

My Diverge has the super easy 31 front, 34 rear that lets me sit to keep weight over the back tire on steep but slippery climbs. I use it often. :)  The Tarmac has the less (but still relatively) easy 34/28 combination, and on paved surfaces, I can generally stand and ride up almost anything I encounter.  But this sort of "what if" exercise using stuff I own to create a set-up where I can pretend to be able to climb like Phil G. just gets me wondering about why it is not just very simple plug and play process.

Yeah I haven’t put too much thought into it... If I ever do up another road bike I think it would be a 50X36 with a 11-34 though.  I like my cross cranks for how I ride my bike but if it was strictly a dirt bike I may go single if not a 31.  

I find a 34 is just too low a gear on the road unless I’m really climbing and find myself cross chaining a lot more than on my 46X36.   I also find I rarely spin out as if I’m going 30+ downhill I’m coasting anyway.

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1 hour ago, ChrisL said:

Yeah I haven’t put too much thought into it... If I ever do up another road bike I think it would be a 50X36 with a 11-34 though.  I like my cross cranks for how I ride my bike but if it was strictly a dirt bike I may go single if not a 31.  

I find a 34 is just too low a gear on the road unless I’m really climbing and find myself cross chaining a lot more than on my 46X36.   I also find I rarely spin out as if I’m going 30+ downhill I’m coasting anyway.

I had the 50/36 compact for a decade on the 10sp Roubaix and loved it. BUT when I got the Tarmac 11sp with the 50/34 and the 11-28 (vs 12-27), it was a OMG this is great event!  Now, five years into the 11sp world, I realize - on the big ring - I spend 98% of my time in the 11 to 19 cogs, about 2% in the 21, and almost never (except by accident) in the 23, 25, or 28 cogs.  On the little ring, the opposite is true - never in those hardest 11, 12, or 13 tooth cogs, and really mostly in the easy peasy cogs.

Looking at the two cassettes, it is reasonable to think the 11-34 is not a bad option if you have some sharp climbs ahead of you.  On the flats, my faves - the 15, 17, & 19 cogs - would still be there for me to use, but losing the 14 might be a little annoying for slight downhills but not enough to be a deal breaker. The 12 is really a "meh" gear I usually pass through quickly to get to the high speed 11 :)

11-12-13-14-15-17-19-21-23-25-28

vs

11-13-15-17-19-21-23-25-27-30-34

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