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How does one interpret the delineation of horizontally-aligned boxes on the Shimano compatibility charts? Below is a screenshot (with added blue numbering) for discussion purposes.

enter image description here

For example, why are Boxes 3, 4, and 5 separate if they're all compatible with Box 1?

Now, it's pretty clear the Box 2 components are compatible with Box 7. But are ALL Box 1 components compatible with ANY from Box 3, 4, or 5? That would also imply that any Box 1 component is interchangeable with another Box 1 component, but according to this source, ST-R3000 and St-3500 (aka the new and old versions of Sora brifters) should have different amounts of brake cable pull and would be dangerous to interchange.

As a further inconsistency, there are no levers listed as compatible with Box 6 brakes. One would expect that at least the components from the same groupset to work with each other, yet ST-R353 (Box 1) and BR-R353 (Box 6) are supposedly incompatible based on the chart.

Note: There is no 3rd column of components for this part of the chart that might explain limited vertical interchangeability.

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    you haven't mentioned the gold colour of some items. It is probably relevant.
    – Noise
    Commented Nov 11, 2022 at 20:26
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    Brown font indicates items that are out of production. Blue font (not in screenshot) indicates items new to that production year. If you click through the link, you'll see it's stated on the chart page.
    – ETL
    Commented Nov 11, 2022 at 20:57
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    Generally, I go by what the manufacturer says over some random internet video clip. I have found people having difficulty reading Shimano's charts fall into two groups - novices to bike maintenance and seeing them for the first time or having difficulty coming to terms that the parts they want to use are not compatible.
    – mattnz
    Commented Nov 12, 2022 at 0:33

1 Answer 1

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Why are Boxes 3, 4, and 5 separate if they're all compatible with Box 1?

Boxes 3, 4, and 5 are separate because they are groupings of different types of brake calipers/types. They are separated for convenience because they are distinctly different from each other:

  • Box 3 contains traditional cable-actuated road rim brake calipers, including a few that are designed to mount under the bottom bracket/chainstays.
  • Box 4 contains cable-actuated center-pull rim brakes.
  • Box 5 contains cable-actuated (mechanical) disc brake calipers.

Box 1 contains a bunch of brake levers/brifters used to control the brake calipers, etc. in boxes 3, 4, and 5.

Box 6 contains "V-Brake" brakes that require a different cable pull ratio than what is offered in boxes 1 and 2. if one used the Box 1 or 2 brake levers with Box 6 brake types (V-Brakes), the pull ratio would provide too much leverage on the brake for the type of brake which could be hazardous to a rider, hence the "No!" indicator.

Chasing this down from the V-Brakes direction back to compatible brake levers, Shimano gives a stern warning regarding the proper "mode" being set for the brake type being used (word-for-word from the Shimano page):

Warning

If the mode is not set correctly for the brake type, the leverage will not be correct resulting in either “inadequate or excessive” braking power.

The brake levers in Box 2 match up well with the brakes in Box 7. The diagram shows that the Box 1 brake levers also will work with Box 7 brakes (a footnote on the diagram states "Braking power is slightly less than standard combinations"), however Box 2 levers are not linked to Boxes 3, 4, and 5 brakes. There is a difference in the pull ratio that is tolerable in the Box 1-7 link, but the corollary match up of Box 2-3/4/5 is not desirable.

One would expect that at least the components from the same groupset to work with each other, yet ST-R353 (Box 1) and BR-R353 (Box 6) are supposedly incompatible based on the chart.

That is a good observation, and after looking up both components, I would have to assume that even though they appear to be from the same groupset by the numbering, they actually are not. ST-R353 is part of the Sora groupset family, and the BR-R353 does not appear to be part of the same family. It is a Shimano part numbering decision.

The likely reason that Box 6 is listed here is because someone can incorrectly assume that because of the common numbering, the two components are compatible, when in fact they are not. So Shimano chose to distinctly call out that the ST-R353 is not compatible with BR-R353 (and ST-R460 is not compatible with BR-R463). There are other V-Brake models besides these two. However, these two V-Brake models just have a greater potential for a false assumption of compatibility due to similarity in their numbering with the Box 1 brake levers/brifters.

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    I recall when I first converted to V-Brakes on my MTB, that my XT brake levers needed to be adjusted to correctly change the leverage/pull of the cables to match up with the superior leverage the V-Brakes imparted. When using traditional center pull MTB rim brakes, the brake levers were set up to pull less cable giving me more leverage. When switching to V-Brakes, the cable end moved away from the handlebar providing more pull and less leverage. The brakes gave a warning that if the high leverage position was used, the compounding of superior leverage could cause problems (lock ups/skidding).
    – Ted Hohl
    Commented Nov 11, 2022 at 22:40
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    Good answer, especially re: the R353 confusion. I'm inclined to mark this answer as accepted, although it would be good to know if you have any insight about whether the different gen levers with different cable routing (e.g. R3000 vs 3500) indeed have different pull amounts?
    – ETL
    Commented Nov 11, 2022 at 23:10
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    @ETL This answer is correct. The SLR-EV difference is real, but it's a little sticky because many people have ignored it and run bikes with the mismatch in both directions, so it's an area that is rife with differing opinions. I personally disagree with the verbiage chosen by the article you link to, where it says that the the more dangerous combination is new calipers on old levers. That combination feels like garbage but tends to be able to set up to produce good power. It requires very small pad gap. The other combination is where you're likely to just not have enough power. Both are bad.
    – Nathan Knutson
    Commented Nov 11, 2022 at 23:19
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    @ETL I cannot offer any direct evidence that the pull amount/leverage is the same between the two cable routing types. However, it would be safe to assume that if there was a significant difference, they would be grouped separately instead of together.
    – Ted Hohl
    Commented Nov 11, 2022 at 23:58
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    @ETL There is also the seldom discussed angle on this conversation where some types of brakes can be set up different ways depending on whether the lever is SLR EV vs traditional pull. Popular mechanical disc brakes like BB5R, BB7R, and TRP Spyres are an example. Where you set the starting position of the actuation arm has a bearing on how well it will play with the leverage of different brake levers, i.e. Shimano versus everyone else.
    – Nathan Knutson
    Commented Nov 12, 2022 at 3:29

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