Go from 38t chainring to 42t chainring

[james105]

Hi, I have a quiestion. Can I used the same chain? Where I live there are very few hills and I want to get more speed. I have a SRAM SX Eagle
(1 x 12) 11-50 38t chainring. I would like to get a 40t or 42t chainring. Would I need a longer chain? Any assistance would be greatly appreciated. I have never used the 50 ( just not hilly enough) I was thinking maybe a 46t but that might be to big.
Thanks
James

 

[I like Skol]

Depending on original chain length then yes, you would need a longer chain. On the otherhand, some bikes are shipped with a chain longer than needed because.... just because! If you changed your cassette from the 11-50 to 11-46 that would cancel out the change in chainring size and the chain length should then remain the same, but when fitting a new cassette it is customary to fit a new chain anyway. You could go even smaller on the cassette, maybe something like an 11-36? Try experimenting not using the biggest two or three cassette sprockets and see how you get on. The advantage of running a smaller range cassette is that there are smaller jumps between each gear so you are less likely to find yourself struggling in one gear but spinning too fast in the next.

I did exactly this when I bought a hybrid commuter bike many years ago. It came with an 11-32 cassette but for urban road use I found an 11-25 or 11-26 (whichever was cheaper at replacement time) was more suited to my riding style and requirements.

 

[Cycleops]

40 isn't going to make much difference so go for a 42 or larger if you want.
Try the chain with the new set up. Wrap it around the 50 tooth sprocket onto the chainring ( not through the derailleur) + two links and check.

 

[Ajax Bay]

Depending on original chain length then yes, you would need a longer chain.

"I want to get more speed."
Go for a 46t: it will not be too big in "not hilly" terrain. That'll still give you a perfectly good 'low' gear but allow you to bowl along on 46-11.
The chain (if the right length now) needs to be one half link (1/2") longer for every 2 teeth you increase the chainring by.
If the current cassette has done less than 1000 miles, the new chain will work fine.

 

[james105]

Thanks everyone........ Great info I really appreciate it.