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Shimano XT/XTR cable vs DI2 rear derailleur shifting speed - which is faster?

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inverse_of_zero

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Discussion starter · #1 ·
Hi guys, tried searching the web but found little info addressing this specific question so thought I'd try here.

Comparing 'like-with-like' only (e.g. XT-with-XT, 11-speed etc.) which rear derailleur system (independent of anything up front) would shift faster, the latest cable offerings M8000/M9000 or the latest DI2 offerings M8050/M9050?

I propose two tests, broken into two sub-races for up and down shifting:

1) single-gear shifts (anywhere within the range of the cassette)
2) entire-cassette shift progressions (e.g. from biggest to smallest gear)

Timing would start from when the thumb touches the shifter paddle, and end when the chain has completely engaged with the destination gear.

My web research (mostly watching YouTube demo videos of shifting) leads me to suspect that DI2 wins race 1, but cable would win race 2. From the videos, it looks like the derailleur movement between single gears is freaking fast like instant, and I don't know if any cable system can match that. However, all videos I have watched of DI2 rear mechs progressing through large chunks of or entire cassettes seem to be rather sequential and they simply don't 'dump' gears quite like a big thumb-ful of lever on a cable system does.

Does anyone here have any suggestions or conclusions regarding the two 'races' above, based on some empirical evidence (and not just pure thought, speculation or please)? If so, I'd love to hear the results!

I didn't post the reasons WHY I'm asking this question as they're subjective and I don't feel they contribute to the science/discussion.

Cheers!
 
Discussion starter · #3 ·
Well like I alluded to explaining this is not constructive to the discussion, but if it helps I'm comparing shifting speeds in 1x setups, electronic vs cable actuated, for performance reasons..

Sent from my 0PJA10 using Tapatalk
 
#4 ·
Not a direct answer, but I can program the rear shift speed of my di2 anywhere from normal to super fast. For my mechanical shift bike I use SP41 housing and clean cables, and my clutch tension is set as light as can be without excessive chain slap. I would bet 99% of riders never played with their clutch derailleur adjustment. It makes a big difference in feel and speed.

I've never "timed" the shifts up or down the cassette between di2 and mechanical.

Not that you asked, but di2 with synchro shift (only 1 shifter handling both) is the main reason I went di2. For me di2 1x makes no sense so in a way I guess that answers your original question to an extent: rear shifting with sp41 and clean cable is a very fast setup in both directions.
 
Discussion starter · #5 ·
Thanks for your insight, much appreciated.

Indeed I suspect that shifting speed with cable would be on-par with DI2, but was hoping for some real-world anecdotal evidence from an end-user such as yourself. I was contemplating upgrading to XT DI2 (M8050) from regular XT (M8000) if one benefit would be to simply increase speed in rapidly progressing up and down the cassette. My riding frequently induces large accelerations and decelerations whereby I would ideally like to jump from one extreme of the cassette to the other in less than a second. I guess ultimately that's what a front derailleur does in a 2x drivetrain (namely, an extreme change in gear ratio upon a single lever actuation in sub-second timeframes) but with wide-range cassettes reaching typical 2x gear ranges (think e13 TRS+ 9-44T cassette @ 489%) and rapid-fire shifting we can have the lighter weight and simplicity of 1x :)

So in conclusion, if you're implying that DI2 is unlikely to be quicker than cable in progressing large chunks of the cassette in one hit then I think I'll stick with cable for the time being, unless someone else chimes in with evidence to the contrary. Cheers!
 
#6 ·
When I customize my di2 for the fastest shift speed it will NOT go from one end to the other in less than a second. If the pedal speed is not fast enough to get the cog teeth utilized for said shifting then it will cause clunk crunch clack.

di2 may be a hair quicker than a finely tuned cable, but not by much. In its defense di2 would be quicker due to fatigue; tired rider simply has to press or hold the button which they programed pre-ride for specific gear change speed, whereas a tired rider on mechanical would have to "remember" to push the paddle several times and with timing to get accurate fast shifting.

Best of luck.

inverse_of_zero said:
Thanks for your insight, much appreciated.

Indeed I suspect that shifting speed with cable would be on-par with DI2, but was hoping for some real-world anecdotal evidence from an end-user such as yourself. I was contemplating upgrading to XT DI2 (M8050) from regular XT (M8000) if one benefit would be to simply increase speed in rapidly progressing up and down the cassette. My riding frequently induces large accelerations and decelerations whereby I would ideally like to jump from one extreme of the cassette to the other in less than a second. I guess ultimately that's what a front derailleur does in a 2x drivetrain (namely, an extreme change in gear ratio upon a single lever actuation in sub-second timeframes) but with wide-range cassettes reaching typical 2x gear ranges (think e13 TRS+ 9-44T cassette @ 489%) and rapid-fire shifting we can have the lighter weight and simplicity of 1x :)

So in conclusion, if you're implying that DI2 is unlikely to be quicker than cable in progressing large chunks of the cassette in one hit then I think I'll stick with cable for the time being, unless someone else chimes in with evidence to the contrary. Cheers!
Click to expand...
 
#7 ·
I can't picture any real-life situation where you would need to go from one end of the cassette to the other in less than one second, short of running into a wall or riding off a cliff. In both cases, slow shifting will be the least of your problems.
 
Discussion starter · #8 ·
@Crossmax - commuting. 95% of my rides with my MTB are along a bike path that is shared with pedestrians and frequently intersects with traffic including traffic lights and driveways.

On nearly every ride, I am travelling at considerable speed downhill, and frequently I need to slam on the brakes because a pedestrian has just walked out or a car hasn't stopped at an intersection or checked their blind spot, through no fault of my own. I suddenly find myself at a walking speed in the highest gear ratio (~4.2 on my bike). So on a nearly daily basis, I rely on the ability to be able to shred down the gears on my cassette because if I don't shred these gears before the bike has come to a significant slow down, it's a ***** to get back up.

Conversely, I find myself in situations where I am frequently in too low a gear for the conditions, again through no fault of my own. For example, if I know there is a busy part, then for the sake of hazard anticipation and safety I'll usually dump half the cassette and ready the brakes, but more often than not it'll be completely clear and then I'll jump back into the highest gear ratio to carry on with my momentum; I am a low-cadence rider. Also there are instances where I'll be carrying a low gear through most of my ride and then there will be a break in the traffic where I can (legally and safely) ride in the bus lane at the same speed as the cars so my speeds will literally go from 5-10km/h on a bumpy uphill bike lane to around 50km/h on smooth downhill tarmac in a few seconds, so again, I find myself going from one extreme of the cassette to the other in as short a time as possible.

The remaining 5% of offroad riding is also justified because similar 'close calls' frequently happen whereby an animal or other rider suddenly comes into your view and you drop heaps of speed and likewise dump heaps of gear ratio in a very short amount of time, especially if you're new to the trail or the conditions have changed. Admittedly the opportunity for needing to *increase gears rapidly* on opposite sides of the cassette would happen very rarely offroad but happens often enough on my daily commute. On my most recent offroad ride there were a few instances where a couple of blind corners, steep switchbacks after very fast sections and riders that popped out of nowhere had caused me to dump a whole cassette in a single second or as quick as possible.

Perhaps this is my lack of experience of offroad riding needing to dump a whole cassette in one actuation in an emergency or blind spot situation, but I won't attribute lack of experience to my commuting as I've been commuting for at least twenty years.

I didn't think that my request was unreasonable so I don't understand why I have been questioned about it in a condescending way as if it were unreasonable. It was a fairly simple (and I think interesting and valid) question and I wasn't looking for people to criticize or make judgement on my use of the manoeuvre, just simply to answer the simple question.
 
#9 ·
inverse_of_zero said:
On nearly every ride, I am travelling at considerable speed downhill, and frequently I need to slam on the brakes because a pedestrian has just walked out or a car hasn't stopped at an intersection or checked their blind spot, through no fault of my own. I suddenly find myself at a walking speed in the highest gear ratio (~4.2 on my bike). So on a nearly daily basis, I rely on the ability to be able to shred down the gears on my cassette because if I don't shred these gears before the bike has come to a significant slow down, it's a ***** to get back up.
Click to expand...
If you're encountering situations like this on a daily basis you might want to either check your speed or your riding style, I used to commute daily in heavy city traffic and despite riding pretty aggressively that sort of thing was a rarity.

Dumping the whole cassette one way or the other on the road seems like a weird situation to me, more common off-road but I hardly ever do it there either.
 
Discussion starter · #10 ·
@JB I think you might be right, thanks, it's got me thinking..

Before I moved to where I live now, on my old commute I never had these problems, because the bike lanes were actually integrated into the *roads* themselves, so bikes moved along the general flow of the cars, and so there was very rarely the 'emergency stop' situation where I had to dump a whole cassette in one go.

It's not until I moved recently and subsequently changed to a different set of bike lanes that this problem started happening. My current bike route (completely structured and registered by local councils) is IMO inherently more dangerous than my prior route, because the bike lanes are integrated with the footpaths. In this case, pedestrians don't know/realise that their footpath is shared by many fast-travelling bicycles (and I suspect it may be one of the busiest cycle routes in Australia, connecting Sydney CBD to the Inner West) and they just blindly treat it as a pedestrian-only space, not realising it's a shared commuting space. Furthermore, there are three petrol stations and close to ten bus stops (along my portion) that run alongside the cycle paths, and unfortunately again, cars and bus travellers (respectively) don't realise they're entering a council-established cycleway when they drive/step out of the petrol station/bus stop. But of course they always stop before they get to the road for fear of cars, but overshoot the cycleway out of ignorance of bicycles. The story of our lives as cyclists I guess...

After some thought spurred on by the above post by @JB ^^ I have decided that any downhill portions are maybe too dangerous to travel along cycleways that are integrated into footpaths. Fine for kids or slow commuters (or going uphill), but I like to ride fast to get to work/home etc. So I have decided, in the interests of safety for everyone on the roads and paths, I'll be moving as much of my downhill portions to the road whereby I can travel without fear of these factors aforementioned. Then I won't be needing to worry how quickly I can dump my entire cassette. Let's see how that goes.

In any case, I think my original question was answered, namely, a well-tuned cable XT drivetrain is likely at least on-par with XT DI2 in terms of the speed of dumping large gear ratios in rapid succession.

Thanks again, George
 
#14 ·
It's kind of tongue in cheek, underlining the fact that it appears the problem you are attempting to solve isn't really the problem, or rather that you are looking for a solution to a problem that does not exist.

With a grip shift, you can dump the whole cassette in one twist (assuming you can pedal fast enough to keep up with the dump lol) So from a technical perspective, this will be pretty much guaranteed to be the fastest way to switch a large number of gears. But it's **** and wouldn't help you anyways.

With modern drivetrains and shifters, this just isn't a problem. I mean, I read your example...I commute on a 1x10 29er fairly regularly. I'll come in hot in my highest gear, just miss a light and have to dump speed...which I do while dropping gears, and within the time it takes to stop I'm down in the gear I'll want to be to get rolling again. Any faster shifting mechanism would start to introduce problems with actually changing and engaging over the gears you are shifting through...like with the gripshift.

Your drivetrains ability to immediately drop gears across the entire range is not going to address your needs. Better shifting technique will.
 
#15 ·
inverse_of_zero said:
Could you please clarify exactly what you mean and referring to? I was interested/thinking about the speed of grip shift vs conventional trigger shifting..

Sent from my 0PJA10 using Tapatalk
Click to expand...
Going from biggest cog to smallest as quickly as you can twist the grip.
Smallest to biggest, a bit slower, but still faster than triggers.
 
Discussion starter · #16 ·
@Wayward, thanks for your personal insights, but I have to disagree. For me the problem does exist, though I am willing to put the possibility that it's due to poor technique. I argue that in your cases, when you "miss the lights" you have ample time to shift down and adjust, then you come to a stop because you have to. When a car or pedestrian comes into your right of way blocking your lane illegitimately, not only do you need to actually stop much more quickly (due to less reaction time), but you also need to shift quicker, because you are not obliged to stop should the pedestrian move or you can move around the car (something I've had to do a couple of times to avoid a crash). In this instance: you have to make an emergency slow down in the sub-second to second timeframe, but you would like to avoid completely stopping if possible, thus getting down to a lower gear as quickly as possible would be desirable. Even if it's just me who experiences this, I know that I want rapid shifting across the cassette. My current shifting is too slow so anything quicker would be a bonus though of course not a necessity.

Motivated by this question of gear progression speed through the range of a cassette and also @Nordie's info, I started to research into Grip Shift (GS). I learnt heaps of valuable info, namely, that it's the thing that started SRAM when I was born, and the technology is current and not limited to cheapie $100 chain store bikes from the 90s. I didn't even realise that current (or at least recent) pro XC racers often use GS.

After watching this video on YouTube


I am convinced (as alluded to above) that GS has the most rapid whole-cassette progression. I have never seen any trigger system (whether electronic or cable) progress across a whole cassette like that. Though I think the individual single-cog shifts are probably quicker with DI2.

Okay, put it down to my poor shifting technique perhaps, but this is how I ride. At the top of the hill, I'll jump right down to the smallest teeth. I'll scream down the hill as fast as I can (so as not to piss of the cars behind me), then I'll get to an intersection that I can pass through, and it's a big uphill, so I'll dump nearly the whole cassette in one go right at the last second then slow down and climb. It's just my riding style, which probably unfortunately, was motivated by my car racing training (whereby yet again, I would go down the straight in 5th gear at full throttle, then break as late as possible, then 'dump' my gears all the way down to 2nd gear for the first corner which would often be a very slow speed turn as well).

Aside from suiting my personal (and perhaps flawed) shifting technique, GS serves two other benefits: it allows me to run my brake levers more inboard than they currently are due to handlebar constrains, and furthermore I have small hands and I find it difficult to fully engage the Shimano shifting paddles to dump the full 4 gears as it stands, and honestly all that thumb acrobatics is exhausting after a while. Whilst not as effortless on the hands/thumbs as DI2, I am sure that GS is far less exhausting in terms of raw energy requirement for actuation for dumping a whole cassette versus triggers.

I have a XT 1x11 drivetrain already set up, but I am thinking that I'll give GS a try (looking at purchasing a SRAM X01 1x11 setup tomorrow) and keep the XT kit as a spare if it doesn't work out.

So in conclusion then, Grip Shift is much faster than DI2 which is marginally faster but on par with good cable drivetrains in terms of large cassette progressions. Would you guys agree?

And finally, thanks again to @JB for the obvious suggestion. I changed my route last night so that all my fast downhill sections were ridden on the road with the cars and not on the footpath, and it made a big difference. I was not only able to go faster due to less slowing down from obstacles and potential dangers (mentioned in previous posts), but I felt safer too. Just ride and obey the road rules, no need to stop, swerve, etc. I know that drivers get the shits with cyclists that don't use cycleway infrastructure and ride on the road instead, but in this case I think it's safer for me to ride on the road than on a congested footpath with ignorant pedestrians and motorists exiting driveways.

Cheers again guys! :)

George
 
#17 ·
I was using a 9-speed X0 GripShift with a tweaked Zee clutch derailleur until I caught the single speed bug.

The tweak is that small 4mm block under the cable pinch bolt in the vid.
Only needed to run a Shimano mech though.
 
#18 ·
Di-2 reliability and insufficient benefit compared to cable shifters

I run 9-speed drive trains with X0 triggers and a 10-speed M-986 clutch derailleurs on my two geared bikes... works like a champ (only thing I do different on my single speeds is run beefier Whipperman White Start 108 chains).

The Di-2 is great except when it stops working. Twice now I've been on rocky/technical rides with people using them and ended up with shifting problems. On one of the rides where shifting failure eventually occurred, it happened to one of four guys who were all riding the Cannondale Black Inc XTR Di2 version ($$$$$$$$$$).

Cable shifting technology is fine by me and if there is snappage, it is easy to rig up something to avoid a long walk of shame (or freezing my arse off in the winter).
 
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#19 ·
Having ridden Ultegra 11 speed mechanical and Ultegra Di2 11 speed, shifting speed is more complete/precise on the Di2 both ways. The derailleur is so precise, that the shift is faster and smoother.

I have my "auto shift" (hold the button down and it shifts continuously) set to full speed. It is still too slow for extremely rapid shifts.
If I click the crap out of shifter, it's lighting fast, but the auto shift is slower than mechanical, even full fast speed.
 
Discussion starter · #20 ·
@Deth thanks for your anecdotal input! And I agree (at least from what I've seen), the individual shifts for DI2 (especially road) are so super smooth, quick and crisp, but yeah 'horses for courses', road DI2 is suited to road riding whereby super smooth transitions in cadence are prioritised; there is little to no need for a road cyclist (excluding commuting) to jump across two extreme ends of the cassette.
 
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