# What is Zero Loss?



## AndreyT

So, what is "Zero Loss"? 

I have been trying to find a meaningful description on the Net to no avail. Most explanations boil down to saying that Zero Loss is Zero Loss. 

The description on SRAM site says that it "engages the cable instantly". This, of course, does not immediately make any sense by itself, since SRAM shifters use DoubleTap action. They cannot possibly engage anything instantly until they "know" for sure whether the user wants an upshift or downshift. 

Take the right shifter, for example. At what points of shifter action will I feel the difference with no-Zero Loss SRAM shifter? And what would that difference be?


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## Peter P.

Zero Loss, from the SRAM web site.


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## AndreyT

Peter P. said:


> Zero Loss, from the SRAM web site.


Yes, that is exactly what I quoted in my original message. And, again, that page explains absolutely nothing and, frankly, makes no immediate technical sense, especially in context of SRAM (DoubleTap) shifters. It is a marketing page. I need a more technical one. 

I'm looking for a detailed technical explanation of at least functional difference. When exactly does Zero Loss shifter "engage the cable instantly" and non-Zero Loss doesn't?

It says "There is no middle-ground where you're waiting for the shift to come". What "waiting" does it refer to in non-Zero Loss shifter?


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## Peter P.

Sorry; I apparently wasn't paying attention to your original post.

The Zero Loss must be trying to differentiate itself from Shimano in the marketplace. For instance, my 9 speed Ultegra levers have a few degrees of "dead space" where the lever moves laterally but it's obvious it hasn't engaged the cable pull mechanism yet. I'm not sure of any benefit but I guess SRAM thinks instant engagement implies better. The dead space is hardly an annoyance.


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## Mapei

Peter P -- The way you describe it, Zero Loss has been a feature of Campagnolo shifting since the 1960's.


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## AndreyT

Peter P. said:


> The Zero Loss must be trying to differentiate itself from Shimano in the marketplace. For instance, my 9 speed Ultegra levers have a few degrees of "dead space" where the lever moves laterally but it's obvious it hasn't engaged the cable pull mechanism yet. I'm not sure of any benefit but I guess SRAM thinks instant engagement implies better. The dead space is hardly an annoyance.


The plain concept of "eliminating dead space" would make perfect sense in case of Shimano shifters, which use separate levers for upshifts and downshifts. But, sorry, this does not immediately make sense in case of SRAM shifters.

The key detail here is that SRAM used DoubleTap interface - a _single_ lever is deflected in _the same_ direction for both upshifts and downshifts. Upshifts are achieved by shallow lever deflection, while downshifts are performed by deep lever deflection (referring to the RD shifter).

For this reason, when you start deflecting the lever in SRAM shifter, the shifter initially does not "know" whether you want an upshift or a downshift. The shifter always have to "wait and see" what you are going to do next. If you go for a deep deflection, the shifter says "Aha!" and performs a downshift. If you release the lever after a shallow deflection, if says "Aha!" and performs an upshift (note that for this reason upshifts are performed on the return travel of the lever, i.e. after you released it).

To me it immediately looks like this DoubleTap mode of operation makes it impossible to operate without a "dead zone". It is not possible to "engage the cable immediately" in a DoubleTap shifter. At least that applies to regular SRAM shifters.

So, what am I missing about DoubleTap action of a Zero Loss shifter? The basic fact remains unchanged: initially, a DoubleTap shifter cannot tell whether you want an upshift or a downshift. How are Zero Loss shifters different? How do they "engage the cable instantly" then?


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## Chader09

AndreyT said:


> The plain concept of "eliminating dead space" would make perfect sense in case of Shimano shifters, which use separate levers for upshifts and downshifts. But, sorry, this does not immediately make sense in case of SRAM shifters.
> 
> *The key detail here is that SRAM used DoubleTap interface - a single lever is deflected in the same direction for both upshifts and downshifts. *Upshifts are achieved by shallow lever deflection, while downshifts are performed by deep lever deflection (referring to the RD shifter).
> 
> For this reason, when you start deflecting the lever in SRAM shifter, the shifter initially does not "know" whether you want an upshift or a downshift. The shifter always have to "wait and see" what you are going to do next. If you go for a deep deflection, the shifter says "Aha!" and performs a downshift. If you release the lever after a shallow deflection, if says "Aha!" and performs an upshift (note that for this reason upshifts are performed on the return travel of the lever, i.e. after you released it).
> 
> To me it immediately looks like this DoubleTap mode of operation makes it impossible to operate without a "dead zone". It is not possible to "engage the cable immediately" in a DoubleTap shifter. At least that applies to regular SRAM shifters.
> 
> So, what am I missing about DoubleTap action of a Zero Loss shifter? The basic fact remains unchanged: initially, a DoubleTap shifter cannot tell whether you want an upshift or a downshift. How are Zero Loss shifters different? How do they "engage the cable instantly" then?


Not true since they claim "Zero Loss Engagement for fastest shifting" with their MTB shifters that use two separate levers for the different shift directions.

https://www.sram.com/sram/mountain/products/sram-x01-11-speed-trigger-shifter


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## AndreyT

Chader09 said:


> Not true since they claim "Zero Loss Engagement for fastest shifting" with their MTB shifters that use two separate levers for the different shift directions.


That's great, but they also claim Zero Loss on a large set of DoubleTap road shifters. My question is specifically about DoubleTap road shifters. What does Zero Loss mean for a DoubleTap road shifter?


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## Chader09

I can't say that I know. I just wanted to point out that the feature is not exclusive to the DoubleTap shifters as the statement seemed to imply.

The additional statement in the post I quoted, that "Zero Loss" somehow is impossible because a single shifter performs two functions, is pure speculation.

Without knowing the actual performance claimed by the "Zero Loss", it is not possible to determine if it is valid for the DoubleTap shifters.


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## AndreyT

Chader09 said:


> I can't say that I know. I just wanted to point out that the feature is not exclusive to the DoubleTap shifters as the statement seemed to imply.


No, the references to DoubleTap are there specifically to emphasize the key element of my question: the apparent incompatibility of the "marketing" description of Zero Loss (from SRAM web site) with DoubleTap. And this is what my question is about.



Chader09 said:


> The additional statement in the post I quoted, that "Zero Loss" somehow is impossible because a single shifter performs two functions, is pure speculation.


No, the "marketing" description of Zero Loss (as it is given on SRAM site), if taken literally, does not make any immediate sense in contect of DoubleTap operation (DoubleTap specifically, not some generic "single shifter performs two functions"). This is a solid fact, not a speculation.



Chader09 said:


> Without knowing the actual performance claimed by the "Zero Loss", it is not possible to determine if it is valid for the DoubleTap shifters.


Firstly, "the actual performance" is part of my question: what exactly does it do?

Secondly, what we do know is, again, the description from the SRAM web site with "cable is engaged instantly" wording. This is also a part of my question: what does "immediately" mean in case of DoubleTap operation?


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## cxwrench

Judging from the avalanche of replies it seems you're the only one w/ the least concern for discovering the answer to your questions.


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## AndreyT

cxwrench said:


> Judging from the avalanche of replies it seems you're the only one w/ the least concern for discovering the answer to your questions.


Hahaha... Thanks for that remark! Um... Think of me as of David Hilbert with his ten problems in mathematics: I ask questions not to trigger "avalanche of replies", but rather to delineate the borders of human knowledge and define the directions in which that knowledge will progress in the future 

On a serious note, the questions in my previous post are quite rhetorical and addressed more to SRAM than to the contributing posters here. It is already safe to say that it is perfectly clear to anyone that there's no such thing as Zero Loss on a Double Tap shifter. It is just a catchy name, born in MTB product range, which at some moment was applied to the entire SRAM product range.


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## dimethi

Does anybody else's rear shifter have this much play? (4-5mm) Front shifter has no play at all. Doesn't seem close to the advertised "Zero" loss..


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## good.darts

dimethi said:


> Does anybody else's rear shifter have this much play? (4-5mm) Front shifter has no play at all. Doesn't seem close to the advertised "Zero" loss..


Can some of us please answer this question - how much play in your Sram Red 22 rear shifter before the mechanism engages? Mine is a good 9-10 mm of movement at the end of the shift lever, wondering whether I should replace it and if that will eliminate all of the play.


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## cxwrench

good.darts said:


> Can some of us please answer this question - how much play in your Sram Red 22 rear shifter before the mechanism engages? Mine is a good 9-10 mm of movement at the end of the shift lever, wondering whether I should replace it and if that will eliminate all of the play.


Mine is about 4mm.


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