This is probably an outdated comparison, as MTB cassettes have moved on to 12 speeds. However, I don't have the chance to compare Shimano 12 speed MTB cassettes, as I no longer have a MTB that can use these cassettes. The last 12 speed cassettes that I compared were the S-Ride and SRAM NX Eagle cassettes, which can fit on existing freehub bodies instead of XD or Microspline types.
Therefore, I can only compare the older but still popular 11 speed MTB cassettes. I have been doing a lot of road cassette comparisons, here is one of the few MTB cassette comparisons.
11 speed MTB cassettes are actually great for gravel riding, as the wide range is well suited for off-road riding, while the ratios are still close enough to use on-road without huge gaps. A prime example is the Cervelo Aspero gravel bike that I have, which is using a 1x11 speed drivetrain. Besides, 11 speed components are very common nowadays, so they are easy to find.
Today, this comparison is all about the 11 speed 11-40T cassettes. This is the smallest cassette that can arguably still qualify as a MTB cassette, as smaller ones like 11-36T are considered gravel or even road cassettes. To be honest, a 11-40T cassette is now more commonly classified as a gravel cassette, since it is one of the cassettes recommended for use with a GRX gravel groupset.
This comparison is between the XTR, Deore XT and SLX version of the 11-40T 11 speed cassette. As expected, the XTR version will be the lightest, but also the most expensive. I have not used the XTR 11-40T cassette yet, while the other two have been used on my bikes.
The Deore XT 11-40T cassette is used on the Bike Friday Haul-A-Day cargo bike, for a wide gear range. I am very happy with the gear range on that bike as it is spot on, and I don't require a lower or higher gear on that bike.
The SLX version was tested on the Cervelo Aspero, when I was attemping to make a super wide range 2x11 speed drivetrain with a 11-40T cassette. Unfortunately the Di2 version cannot support this wide range, but I believe a mechanical drivetrain can.
XTR CS-M9001 11-40T 11 speed cassette, with 4 separate spiders!
Deore XT CS-M8000 11-40T 11 speed cassette, with 2 spiders.
SLX CS-M7000 11-40T 11 speed cassette, with just 1 spider, and a spider-shaped spacer.
The focus for this post will be on the XTR cassette, as I have not studied it in detail before, unlike the Deore XT and SLX cassettes. I am interested to know how it differs in construction with the Deore XT and SLX version, allowing it to be so lightweight.
Biggest two sprockets (40T and 35T) of the XTR cassette are mounted on a 7-arm carbon fibre spider. Largest sprocket is aluminium, while the 35T sprocket is made of titanium.
Deore XT and SLX share the same design, as the last 3 sprockets (31T, 35T, 40T) sprockets are mounted on an aluminium spider. The 40T sprocket is made of aluminium, with the rest being steel.
Rear view of the XTR 7 arm carbon fibre spider, which looks pretty awful to me.
Rear view of the Deore XT/SLX aluminum spider. Looks better in my opinion.
Let's do a weight comparison of these three cassettes, before moving on to check out the XTR cassette in more detail. There is a big weight difference between these cassettes, which correspond to the big difference in prices.
XTR cassette weighs only 324 grams! This is because it has 6 titanium sprockets, 1 aluminium sprocket and just 4 small steel sprockets.
Deore XT cassette is quite a bit heavier, at 413 grams. Just 1 aluminium sprocket and 2 aluminium spiders.
SLX cassette is heavier still, with also 1 aluminium sprocket, but also just 1 aluminium spider. It means that all other steel sprockets are full sized and thus heavy.
Closer look at the XTR cassette, with the above mentioned 1 aluminum sprocket, 6 titanium sprockets and 4 steel sprockets.
Design of the spider, which is made of carbon fibre reinforced nylon (PA-CF). Spline is reinforced with an aluminium insert.
Rear view of the spider, which looks very bulky with the large surface area.
With 1 titanium and 1 aluminium sprocket, plus the carbon fibre spider, these two large gears weigh 117 grams. Although it is considered lightweight, it already accounts for more than 1/3 of the cassette weight.
Next two sprockets (27T and 31T) are made of titanium, also riveted to a carbon fibre spider. This time, a 6 arm design is enough.
Splines are also reinforced with an aluminium insert for strength. The CS-M9001 is a revised version of the original CS-M9000.
There are some holes on this carbon fibre spider, but it is blocked by the ribs running behind it (previous picture). Strange design.
This second set of sprockets weigh just 79 grams.
Here is the 3rd set of sprockets (21T and 24T, both titanium) on the aluminium spider.
Since the spider is aluminium, the splines are machined directly into the spider.
3rd set of sprockets weigh just 49 grams.
There is still a 4th spider for the 17T (steel) and 19T (titanium) sprockets! Even road cassettes don't use a spider to mount the 17T sprocket.
Being small means that only 5 arms are needed for the aluminium spider.
These two sprockets weigh 38 grams. I don't think there is much weight saving over a standard full steel 17T and 19T sprocket, since they are already quite small.
Finally, only 3 loose sprockets, the 11T, 13T and 15T. Extremely rare to find a cassette with just 3 loose sprockets, with the rest mounted on the spiders.
From this, I can see that the weight saving efforts applied to this XTR cassette is quite extreme, with so many spiders and so many titanium sprockets used. The best balance between cost and weight should be the Deore XT version, as it is more durable, a lot cheaper, with some weight penalty.
Some examples of alternative cassettes with the same 11 speed 11-40T are the Sunrace CSRX8, and the extreme KCNC version which is even lighter!
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