Hello! My new CX bike (2017 Kona Private Jake) has a 42t front ring and a 11-32 cassette. As I intend to swap this over to gravel duty for the summer I'd like to put a 11-42 cassette on (probably CS-M8000). The bike has a long cage Rival1 rear D.
The chain on the bike (SRAM PC-1150) has 117 links. This seems to allow a bit of play in the derailleur at both the big and little gears of the cassette.
If I swap in a 42t cassette will the 120 link option that seems to be a common size online be long enough to handle 42x42 with a 16.5" chain stay length?
If I use the calculator here: http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html it tells me I should only have 54 links (108?) and will size up to 56 links (112?) after I put on the new cassette?
Any feedback from people more experience with chain lengths? Thanks in advance!
You can't use undersized chain (>0.1" difference to unrounded chain length from your link to calculator) You can only use oversized chain (0.1..0.9 extra is recommendation, 1.0..1.9 extra is ok, +2.5" is not ok)
I have checked your link and it gives me other numbers (using input 420mm instead of 16.5"): 42x11-32 = 52.61 = 53 chain (106) 42x11-42 = 55.07 = 55 or 56 chain (110 or 112) this is too much difference
You need to change front chainring to use the same chain 38x11-42 = 54.07 = 54 or 55 chain (108 or 112) 40x11-40 = 54.07 = 54 or 55 chain (108 or 112)
This way you can use 108 chain on 40x11-40 or 38x11-42 (-0.1" short is ok) and 42x11-32 (+1.4" long is ok)
Thanks for the great response. It sounds like the math says the difference between a 42t and 42t large cog with the same front ring is too great for the same chain. I'll have to order a new chain when my cassette arrives (wish I had of done that when I put the order in).
I don't agree with your chain length numbers though. I'm not sure what variable isn't right, but I have some feedback. I have two chains for this bike, I counted 53 links (106") and 57 links (114"). The 106" chain was extremely tight on the bike, to the point that the RD wasn't relaxed in the smallest cog and extremely tight in the largest, to the point that it didn't like shifting at the top of the cassette (or the bottom really).
I've attached some picture (sorry for the background, next time I'll put up a sheet or cardboard.
43x32 w/114inch chain
42x11 w/114inch chain
The 114" chain could probably stand to lose a link from my experience.
42x28 w/106inch chain (didn't want to shift on it's own to the 32 cog)
I got numbers from calculator, they may be inaccurate if..: - chainstay length is not 420mm (measure it manually) - b-tension is not optimal - you need to reset it for each cassette (guide pulley must be close to cogs)
(I can see that your chain stay length is adjustable - this make it possible to use same chain for 32 and 42 rear cassette and same front chainring with different chainstay length dropout positions, BUT I do not recommend it - moving dropout regularly takes some time and can wear your frame dropouts)
Thanks Hub. I totally forgot about the sliding dropouts affecting chain length as well. I love the idea of being able to stretch out the bike for spring/summer gravel rides and then tuck the back wheel underneath for CX in the fall.
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\nTo measure CS length, I use B.B. centre to axle centre?
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\nIn your opinion, given the top pictures with the 114 link chain, would you pull suggest pulling a link and seeing where it ends up?
I did 1x conversion on two mountain bike and one fatbike plus some new chain adjustment. I've never used a calculator. There's a lot of video on youtube just using this method: https://www.youtube.com/watch?v=ZUybJs7uork
@LewisQC, your method is more common, but I used this calculator before and it give me the same chain length. In this case, two chain measuring methods can be used to be sure..
@Spreader, yes, center to center When you change chain length you need to reset b-tension (even with the same cassette/chainring)
43x32 w/114inch chain -> it looks like chain is too long (cage should be vertical somewhere in the middle of cassette) 42x28 w/106inch chain (didn't want to shift on it's own to the 32 cog) -> it looks like guide pulley is too far away from cogs (need b-tension adjustment)
Thanks Hub . TBH I checked the limit screws but didn’t think to adjust the b-screw tension after getting the bike. My 11-42 cassette will be here soon, I’ll position the axle and make b- screw adjustments then. Hopefully the 114 link fits the cassette or else I’m heading out for a new 118 link. I’ll post up again after that.
