Swim Bike Run
Slowtwitch.com
  • Login >
Slowtwitch.com
Search menu
Hot Forum Topics

Poll

Best Recent Tech for Tri
What is the most beneficial recent bike tech used in tri bikes
View Results


Home > Forum > Triathlon Forum > Di2 on the TT bike manual vs synchro-shift

Triathlon Forum

Back To ForumPrint Thread

Login required to started new threads

Login required to post replies

Tri
Classifieds
Lavender
Jobs
Notices
Di2 on the TT bike manual vs synchro-shift
Quote | Reply
flogazo
Feb 8, 21 8:01
Post #1 of 16 (3019 views)
Hi,
I have Di2 on my TT-bike with the newer 1-button shifters on the extensions(SW-R9160) as well as the brakes (ST-R9160).
This pretty much mandates the use of full synchro-shifting if you want to shift the full range of gears from the basebar as-well as the extensions.
For this to work, you also need to assign all 4 buttons to only shift the rear derailleur.

That's my current setup and it is OK, even though i still can't get as smooth a shift down into the smaller ring under load (including corresponding upshift of the RD) as with mechanical shifting. It is just slow and noisy and i have to soft-pedal for at least 2 seconds.

So I wanted to give manual mode another try.
Yes - I can reconfigure with e-tube so that the base-bar shifts the FD, but why can't it be configured so that the basebar shifters shift the rear mech in full synchro and the front-mech in manual or semi-synchro mode? That way, I'd just have to switch the shifting mode (which you can do while riding) and not reconfigure the base-bar-buttons with e-tube.
if you can read this
YOU'RE DRAFTING!
Last edited by: flogazo: Feb 8, 21 8:01
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [flogazo] [ In reply to ]
Quote | Reply
ToddRodd
Feb 8, 21 17:30
Post #2 of 16 (2953 views)
Sorry no solution for you, but I too have struggled with the logic of full synchro on TT bikes. I have often wondered why you can't simply push both brake shifters simultaneously to control the front FD. I transitioned back (at a cost) to manual shifting. Im sure its a personal thing, but i just couldnt stand the soft pedal required.
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [flogazo] [ In reply to ]
Quote | Reply
jharris
Feb 8, 21 17:40
Post #3 of 16 (2947 views)
Did you try to change the shift speed? There is slow, normal, and fast.
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [jharris] [ In reply to ]
Quote | Reply
flogazo
Feb 8, 21 23:10
Post #4 of 16 (2881 views)
jharris wrote:
Did you try to change the shift speed? There is slow, normal, and fast.

I have to check again but i thought it was only something like: Normal, Slow and Slower
if you can read this
YOU'RE DRAFTING!
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [ToddRodd] [ In reply to ]
Quote | Reply
flogazo
Feb 8, 21 23:12
Post #5 of 16 (2879 views)
ToddRodd wrote:
I have often wondered why you can't simply push both brake shifters simultaneously to control the front FD.

Yeah, that'd be a good solution. And if SRAM have some sort of patent on this: Make it long-press that triggers it (i don't use multi-shift at all, much rather just quickly press the button to know exactly how many gears i'm shifting at once)
if you can read this
YOU'RE DRAFTING!
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [flogazo] [ In reply to ]
Quote | Reply
TomvdS
Feb 8, 21 23:41
Post #6 of 16 (2873 views)
The issue with pressing multiple button buttons is that in the software you always have to wait to check whether one or two buttons are pressed, making the shifting inherently slower. Just another idea, would it be possible to add the climb shifters and program them for FD shifting?
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [TomvdS] [ In reply to ]
Quote | Reply
flogazo
Feb 8, 21 23:57
Post #7 of 16 (2870 views)
makes sense. Though I think I'd get used for some small delay for the shift process to start. My issue is more with the shift taking too long.

In the meantime, as a workaround I'll try this: Use full-synchro, but without an automatic counter-shift of the RD when shifting the front. Than I'd be doing that myself like with mecahnical. Hopefully makes it faster.
if you can read this
YOU'RE DRAFTING!
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [TomvdS] [ In reply to ]
Quote | Reply
exxxviii
Feb 9, 21 19:26
Post #8 of 16 (2760 views)
Spend 5 minutes riding an eTap bike and you will know this is not a thing. Shifting FD on eTap is immediate.
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [exxxviii] [ In reply to ]
Quote | Reply
TomvdS
Feb 10, 21 0:16
Post #9 of 16 (2704 views)
In practice yes, in software no. There is no way to detect a double button press otherwise. It actually applies to both the front and rear shift, since for a single button press it also has to wait whether a second button is pressed. Obviously this "delay" is short enough for you to not notice it. However, given the way Shimano operates, I can imagine that this ambiguity is something they want to avoid.
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [TomvdS] [ In reply to ]
Quote | Reply
exxxviii
Feb 10, 21 2:53
Post #10 of 16 (2685 views)
Again, if you ride with Di2 and eTap, you would know that this this is not a thing. Both shift undetectable instantaneously. Here's another theoretical concept to consider... eTap's radio signals travel faster than Di2's electricity signals, so maybe that cancels out? Another thing... Di2's messages have to travel to the battery, be interpreted, and then relayed to the appropriate derailleur. All that software stuff, yet Di2 shifts immediately.
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [exxxviii] [ In reply to ]
Quote | Reply
TomvdS
Feb 10, 21 3:10
Post #11 of 16 (2677 views)
exxxviii wrote:
Again, if you ride with Di2 and eTap, you would know that this this is not a thing. Both shift undetectable instantaneously. Here's another theoretical concept to consider... eTap's radio signals travel faster than Di2's electricity signals, so maybe that cancels out? Another thing... Di2's messages have to travel to the battery, be interpreted, and then relayed to the appropriate derailleur. All that software stuff, yet Di2 shifts immediately.

I have both (9100 Dura-Ace and SRAM Red AXS) so I do speak from experience, but that is besides the point. I am talking about the implementation. Both systems do work fine in practice with minimal, of not zero perceived delay. That does not mean that on the implementation side there is none, it's just fast enough for us to not notice it.

Where does your theoretical concept about radio waves traveling faster than electricity signals come from? In the SRAM setup, the rear derailleur is the master unit, whereas for Shimano this is the battery. The wireless signal on the etap system is also encrypted, which also means a "packing" and "unpacking" step.

As said before, my point is not about what you perceive, but how it is technically implemented. There is a difference there which the SRAM engineers managed to design such that it is unperceivable for us.

Some references:
https://www.bikeradar.com/reviews/components/groupsets/sram-force-etap-axs-vs-shimano-ultegra-di2/
https://intheknowcycling.com/etap-vs-di2/
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [TomvdS] [ In reply to ]
Quote | Reply
exxxviii
Feb 10, 21 4:07
Post #12 of 16 (2657 views)
This expands your original comment considerably. That one, in its context, seemed to say that eTap is inherently slower than Di2. But, the reality is that the theoretical difference is irrelevant. Those eTap software engineers worked some excellent code.

Light is faster than electricity. That is not theory.

The big picture is that the implementation differences and double-button push UI are not material. The two shift equally imperceptibly fast, so the difference is moot.

I have both as well. I love them both. I am amazed at how well both perform. I would choose the exact same setups if I were buying again right now.
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [exxxviii] [ In reply to ]
Quote | Reply
rrutis
Feb 10, 21 19:09
Post #13 of 16 (2568 views)
Not questioning that light is faster than electricity but it would be fun to test the circuits to see what the difference is, I am sure it could be modeled if you know all of the circuit elements.

But now that I am thinking about it even if we assume electricity (the signal not the electrons) is travelling at 50% of the speed of light and we assume the signal has to travel 6 feet of wire then the time is 12x10^-9 seconds compared to the EM radio wave travelling 6 feet at 6x10^-9 seconds. Both are really short time spans and probably inconsequential compared to the processing time.

Sorry for the nerd out.

Rich
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [rrutis] [ In reply to ]
Quote | Reply
exxxviii
Feb 11, 21 2:49
Post #14 of 16 (2522 views)
I was really just throwing that out there as another theoretical difference that is pretty much inconsequential, as you noted. It's like telephone design. There is latency in the audio between two people speaking, but industrial psychologists figured out that below a certain point, humans do not detect it. So, latency is OK as long as it is below the threshold of human perception.

I think the speed of electricity is about 1/100 the speed of light. (But, there are circuits on both ends that need to take the signals and translate them to their respective mediums, so there is delay there.)
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [flogazo] [ In reply to ]
Quote | Reply
SBRcanuck
Feb 11, 21 7:24
Post #15 of 16 (2497 views)
flogazo wrote:
Hi,
I have Di2 on my TT-bike with the newer 1-button shifters on the extensions(SW-R9160) as well as the brakes (ST-R9160).
This pretty much mandates the use of full synchro-shifting if you want to shift the full range of gears from the basebar as-well as the extensions.
For this to work, you also need to assign all 4 buttons to only shift the rear derailleur.

That's my current setup and it is OK, even though i still can't get as smooth a shift down into the smaller ring under load (including corresponding upshift of the RD) as with mechanical shifting. It is just slow and noisy and i have to soft-pedal for at least 2 seconds.

So I wanted to give manual mode another try.
Yes - I can reconfigure with e-tube so that the base-bar shifts the FD, but why can't it be configured so that the basebar shifters shift the rear mech in full synchro and the front-mech in manual or semi-synchro mode? That way, I'd just have to switch the shifting mode (which you can do while riding) and not reconfigure the base-bar-buttons with e-tube.


I am about to face the same dilemma. I am doing a new build with disc brakes and want to use hydraulics, so one button brake levers.
I have both types of extensions shifters on hand - the one button shifters and the older two button shifters. What I may do is use 'manual' mode, and install the two button extension shifters. My understanding is that then the brake levers will only control the rear derailleur, and the two button extension shifters will be able to control both fd and rd. So only downside is no fd shifting from the basebar
Last edited by: SBRcanuck: Feb 11, 21 10:25
Quote Reply
Re: Di2 on the TT bike manual vs synchro-shift [SBRcanuck] [ In reply to ]
Quote | Reply
flogazo
Feb 11, 21 10:21
Post #16 of 16 (2451 views)
yeah, that's likely better than my set-up.
if you can read this
YOU'RE DRAFTING!
Quote Reply
Back To ForumPrint Thread

Our Partners

transition-DOT-area-AT-slowtwitch-DOT-com

Advertise with us

©1999-2024 Slowtwitch, Inc., and Slowtwitch.com
Reproduction of material from any Slowtwitch.com page
without written permission is strictly prohibited.