FSA Megatooth chainring 104 BCD!? Smallest chairing size?

jxrx

Member
Dec 12, 2022
100
37
Zürich
Hey all, have a Strive:On CFR Green with Shimano 12spd. I just replaced by 36T FSA chainring with a Raceface 34T (for good reasons...) however I didn't realise that the old chainring (yeah I didn't really look that close to be fair) is actually a 104BCD (I think) spider!

So does that mean I could theoretically go smaller (and yes adapt chain length) if I really wanted to? I ask as I climb in the Alps and appreciate the easier gearing so I don^t need to be in turbo all the time

Also I'm chronically asthmatic so climbing is harder for me and I don't really push it to 40km/h+ on the flats but I figure a smaller chain ring will help push past the 25km/h limit anyway (34T + 51T still gives 40km/h+ with a decent cadence - if I could do that)

What is the smaller chainring anyone has put on a Strive:On with the Shimano XT 12 speed?
 

maramouse

Active member
Mar 24, 2018
185
126
Genoa Italy
Hey all, have a Strive:On CFR Green with Shimano 12spd. I just replaced by 36T FSA chainring with a Raceface 34T (for good reasons...) however I didn't realise that the old chainring (yeah I didn't really look that close to be fair) is actually a 104BCD (I think) spider!

So does that mean I could theoretically go smaller (and yes adapt chain length) if I really wanted to? I ask as I climb in the Alps and appreciate the easier gearing so I don^t need to be in turbo all the time

Also I'm chronically asthmatic so climbing is harder for me and I don't really push it to 40km/h+ on the flats but I figure a smaller chain ring will help push past the 25km/h limit anyway (34T + 51T still gives 40km/h+ with a decent cadence - if I could do that)

What is the smaller chainring anyone has put on a Strive:On with the Shimano XT 12 speed?
Hi, on the same bike, size S I use a 32T raceface 104 BDC, work fine no problems
 

maramouse

Active member
Mar 24, 2018
185
126
Genoa Italy
Thanks that’s good to know! Did you use alloy or steel? Did the chain guide suit still or did you replace it?
Alloy, but only because It was the only chainring 32t 104 available in the store, i prefer more durable steel chainring, no problems with the original chain guide just slightly lowered andI took two links off the original chain ( if I remember correctly ), in my bike the original chainring was 36T.
 
Last edited:

justbet502

New Member
Oct 4, 2024
1
0
Alabama
Any guidance for removing the original chainring? First EMTB and having a bear of a time getting the lock ring off. Do I have to remove the spindle from the hub?
 

jxrx

Member
Dec 12, 2022
100
37
Zürich
Any guidance for removing the original chainring? First EMTB and having a bear of a time getting the lock ring off. Do I have to remove the spindle from the hub?
I bought the bottom bracket tool (don't know which one off top of my head) and used a 3/8" ratchet connected to that to remove the lock ring. I'd YouTube to find a how to

EDIT:
OK the tools I bought were Park Tool BBT-18 for the lock ring removal
1728109608842.png


Also the Park Tool TWB-36 so I could use my Park Tool torque wrench on the BBT-18 - bit of a pain the BBT-18 doesn't have a 3/8" interface but hey it is what it is
1728109657915.png


Oh and a crank puller to get the cranks off, I just bought the Park Tool one again
1728109755292.png


Assuming you have a torque wrench for the correct Nm (mine is yep you guessed it Park Tool ahahah and 3/8" interface to match the above claw) then you should be good to go
 
Last edited:

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