Position of cassette on hub

[Nics]

Hi everyone,

I'm struggling a bit with finding an answer to the following question:

Is it standardized or otherwise knowable where the right edge of the cassette is relative to the hub (for example the end of the hub)? This is important to have proper clearance between cassette and seatstays when building a frame.

One could measure that of course but I don't have the hub and the cassette and won't get it soon.

My hub has a 142.3mm OLD and the cassette is either a 40-11 or a 42-11. Hub drawing: https://www.bitexhubs.com/upload/products/drawing/5a716345c58c3.jpg

The question is complicated by what is described here https://bike.bikegremlin.com/3573/bicycle-cassette-rear-chainrings-standards/: "Cassettes with 10 and more sprockets are designed so that largest sprocket overhangs the freehub body and goes a bit towards the wheel spokes (without hitting them). This enables mounting wider cassette onto a standard sized freehub body (Shimano 11 speed road cassettes still require a longer freehub body)."

Based on the attached image from the the Shimano documentation I have come to the following conclusion:
I guess the best I can do is to assume no overhang off the cassettes towards the weel center which gives me a worst case scenario in the sense that if there is overhang the clearance to the dropouts and the seat stays will be greater. As per the hub drawing (link above) my "R" is 42.6 and acc to the bikegremlin article 11-speed MTB cassettes are 40.6 (somewhere else the Bike Gremlin says he himself measured 40.9, so I assume 40.8). So the right edge of the cassette is 42.6 - 40.8 = 1.8 mm away from the right side OLD surface IF I had a 135.3mm axle but because I have a 142.3mm axle (that hub allows to swap axles to change the OLD dimension) the value instead is 1.8 + 3.5 = 5.3mm.

Has anyone measured this (to back up my calculation) or is there a flawed assumption in my calculation?

 

[BikeGremlin]

Short answer:
I don't know (hope some other visitor has the data).

I haven't got any measurements or stats (as explained below), but if this helps, this is the information and knowledge that I have gathered:

1. My 11-speed cassette measurements​

This is more of a digression but I think the extra info can only help.

My full report on the measurements I took for Shimano 11-speed road and MTB cassettes:
(link to the original cassette measuring question and replies)

I have re-measured, with two brand new high/mid-end 11-speed cassettes:
Road CS-R8000 (Shimano 105)
MTB CS-M7000 (Shimano Deore SLX)

The measured width of the entire cassette:
Road: 40 mm (per calculation it should be 39)
MTB: 40.9 mm (per calculation it should be 40.6)

The measured width of the largest 3 sprockets (they are placed on the same spider – but I measured sprocket width alone):
Road: 9.15 mm (per calculation it should be 9.08)
MTB: 9.6 (per calculation it should be 9.4)

Sprocket width:
1.6 for both cassettes

Spacer width:
I’ve measured exactly 2.2 mm for both cassettes!?!

To confirm and eliminate any possible error, or bias, I asked a colleague from Planet-Bike service to do the measuring as well.

He’s mix-matched 11-speed road and MTB cassettes with no problems and was convinced they are exactly the same, suggesting he needn’t even measure.
I agreed they work perfectly fine in practice, but Shimano says they aren’t 1-1 compatible, and I wish to confirm if they really are exactly the same, or just not different enough for it to make a noticeable difference in practice.

His measurement also showed that the MTB cassette is slightly wider.

We hadn’t measured the exact distance between adjacent sprockets, because that is very difficult to measure accurately. At least using the tools we had (callipers). I think it’s more accurate to measure across several sprockets, preferably the entire cassette, as we did.

His practical experience “aligns” with mine: he too has used a Shimano MTB 11-speed cassette, with Shimano 11-speed road shifter and derailleur – and it worked fine.
He also tried what I hadn’t so far: using a Shimano road 11-speed cassette with a Shimano MTB 11-speed shifters and derailleur – and says that too works perfectly fine in practice and on the workstand.

2. Swapping same-speed cassettes​

When swapping cassettes, even if it's the same number of speeds (even the same manufacturer), you often need to fine tune your rear derailleur limit screws and shifting cable tension.

This is not relevant to your dilemma though, as these are fraction of a millimetre differences from one cassette fit to the next.

3. Cassette to right locknut distance​

In my experience, when measuring these things, I would say that cassettes' smallest sprocket usually (or very often) starts at about 2 to 4 mm from the right locknut (i.e. the part of the hub that leans against the frame - not all the hubs use locknuts).

However, take this information with a grain a bucket of salt, as I never bothered to write that stuff down. In practice, for me, it was important to make sure there is enough clearance for the chain to not rub the frame when it's on the smallest sprocket.

Also note that for freewheels (i.e. not freehubs with cassettes - not technically), the right-locknut-to-cassette distance varies depending on whether you screw on a 6 or a 7-speed freewheel cassette (most freewheel hubs come with enough room for 7 speeds).

4. Things to note and consider​

4.1. MTB cassette overhang​

11 and 12-speed MTB cassettes are designed to overhang the hub's right flange, so their total width is greater than the length of the freehub mechanism they slide onto.

4.2. Boost hub specifics​

See my website's hub article's section about boost hubs.
TL/DR:
"142 mm hubs" don't provide a wider "effective OLD" (let's call it that ). The extra 3.5 mm on each side of those hubs (compared to 135 mm OLD hubs) is used in a similar fashion that quick-release hub axle protrusion is used - to be placed inside the indents of the frame (there's a photo in the above-linked section that depicts what I'm trying to explain here).

4.3. Frame, chainstays and chainline​

Chainstay length, and the difference between the front chainline and the rear chainline, affect the chain's angle when it leaves the smallest sprocket (and all the other sprockets of course).

Also, the shape and design of the frame's rear triangle could affect chain clearance (i.e. how close you can get the smallest cassette sprocket to the dropout's inner side without the chain scratching the frame when on the smallest sprocket).

5. Conclusion​

As I like to say: "One accurate measurement beats a thousand expert opinions."

The safest thing to do is to measure the particular cassette on the particular hub you intend to use.

Having said that, even if you could do that, if designing a frame, it would make sense to err to the side of caution, and design the frame so you can use different cassette and freehub models further down the road.

To achieve that, it would make sense to figure out the worst-case scenarios: the hub and cassette combos with the smallest distance from the right locknut to the cassette's smallest sprocket). Unfortunately, I haven't got that data.

Relja DidNotMeasureThat Novović

 

[Nics]

See my website's hub article's section about boost hubs.
TL/DR:
"142 mm hubs" don't provide a wider "effective OLD" (let's call it that ). The extra 3.5 mm on each side of those hubs (compared to 135 mm OLD hubs) is used in a similar fashion that quick-release hub axle protrusion is used - to be placed inside the indents of the frame (there's a photo in the above-linked section that depicts what I'm trying to explain here).

This is my view of the 135/142 difference: The effective OLD is wider by 7mm on a 142mm vs a 135mm hub because if you "clamp"* the hub by the two dropouts a) on a 135mm hub the surfaces that are 135/2mm away from the hub center are where the clamping force is applied while b) on a 142mm hub the clamping force is applied to the surfaces that are 142/2 away from the hub center.
As far as I know the quick-release hub axle protrusion doesn't experience any of this lateral clamping force.

* pushing the two dropouts each to the wheel center may or may not happen anyway depending on whether the hub is slightly wider or narrower than the distance between the dropouts. If this clamping doesn't happen anyway you can push each dropout to the wheel center for the purpose of this thought experiment.