Hello, I just wanted to share my experience with this kind of upgrade, because the info I found online from other users trying a similar thing was very helpful but none matched my setup completely.
My bike is a Megamo West 15, a bike that (at least here in europe, it's a spanish company) I just highly recommend for its excellent quality-value/price ratio: it's very hard to see a carbon bike with hydraulic disc brakes for less than 2K euros.
Anyways, this bike is equipped with GRX 400 2×10 groupset, with the standard 40-36 crankset and deore CS-HG50 11-36 cassette.
I wanted to get more teeth on the rear. But I felt like 40, which I knew worked without modifications (same chain and stock rear derailleur link), was not much worth the effort and, provided that higher tooth number needed changes to other parts, I just wanted to go for a 11-46 cassette, with a massive 10 teeth boost from the previous one.
I chose the Deore CS-M4100 11-46 cassette, for basically two reasons: compatibility (same model and manifacturer of the old one) and almost same sprockets (grouping two sprockets into one, 19t and 17t into 18t), with the second biggest having only one tooth more than the previous one (37 vs 36), granting for at least 9 sprockets to work as before.
So, being in this cassette the gap between the first and the second sprocket this big, I think of the 46 sprocket as a life-saver on those really steep climbs, where it can make the difference from pushing the bike or pedaling.
Given this (not so) little introduction, let's move to the hot stuff. This is what I needed for the upgrade:
- Deore CS-M4100 11-46 cassette
- WolfTooth Goatlink 10v
- New chain
That's it.
Some extra info:
Even if rated only for 40-42t conversions, the Goatlink 10s was perfect. One of my biggest questions was If I needed to go for the 11s, being it a little bit longer and rated for bigger sprockets. The answer is no, the key (in this case) resides in the design of the piece rather than in the actual length of the link itself.
The position of the notch hit by the B-screw is such that it makes the rear derailleur stick out more (backwards) with respect to the stock link, being this way able to extend its range up the 46t sprocket, with almost the same screwing of the B-screw.
One thing I (as a novice) noticed is that this comes not for free: in fact, when on the smaller sprockets, rear derailleur's inner pulley wheel is way more far from the sprockets with respect to the stock derailleur link, introducing shifting inaccuracy (i'll cover this later).
As per the chain, I opted for SN-LG500 from Shimano, being the one with the biggest number of links (138) I found for a fair price (~20eur), because I was not sure how many links I would've needed for the upgrade.
I ended up discarding around 21 links, for a total of 117 (or 117+1, accounting for the quick-link) links used.
This number of links DOES NOT allow me to do the extreme cross-chaining of 46 front-46 rear. I mean, I think that the grx 400 rear derailleur's long cage would have allowed me to cover it, but I did not want to have too much slack on the chain during the opposite cross-chaining (30-11), which I happen to do more frequently (eg. when after a climb I rush down the upcoming descent forgetting to shift to the big chainring on the front).
What happens when you are on the big chainring and you try yo shift up to the 46 sprocket the chain does not manage to get on, reminding you that you were already cross-chaining and a switch to the smaller chainring is needed.
The final (and more delicate part) was the derailleur tuning. As mentioned early, the bigger distance from the derailleur's wheel from the smaller sprockets led to missed shifts even when using the big chainring. This (i suppose) is due to the fact that the bigger distance of the derailleur wheel makes the sllight movement of the derailleur from two adiacent positions (eg. from 9 to 10 spd) less effective. I solved this by adjusting the lower limit screw a little bit out (with respect to before) to adjust that.
Then came a subtle and fine regulation of the cable tension to try to get the right force to upshift and to let the derailleur downshift on all the sprockets.
Now is almost working perfeclty, the only thing I can say is that on some shifts is a bit slower compared to older sprocket, but I can tolerate this
Long comment but I wanted to share my experience so far, trying to be as clear as possible.
Next I'll ride it and test it on gravel roads, to see if I can spot some criticalities and find some improvements
This is a pic of the result:
https://postimg.cc/62fChS9H
by rugginee