I modded my crank so I could run a 20T chain ring. I currently have a 11-34 cassette. I would really like to run 20x36.
Does anyone know the options. I know Shimano has the Deore 9 speed steel cassette with a 36 but that seems a bit heavy.
I have been told if I run a 10 speed cassette the smallest chain ring I can run is 24 which does not cut it. I like to ride both big and steep hills. Do not care if the option is Shimano or Sram.
Thanks for the help.
Here's to sweat in your eye.
Ok, i will post my own answer from what I can find.
Shimano 10 speed looks possible but is untested and all three chain rings will most likely need to be replaced with after market chain rings
SRAM X0 10 speed should work by just replacing the the stop 22 with a 20 and modifying the crank.
Shimano 9 speed Deore Cassette a bit heavy but not too bad.
Modify an xt cassette.
Conversion kit 11/32=>12/36
xtr cassette (xt would work too of course) in 11-32. it has to be that range. removed the 11t cog, the next one up is a 12t, serrated for a lockring. got a 12t lockring, a cassette spacer, and an action tec 36t cog to put behind the largest cog. worked perfectly with my x.0 rear derailleur using a longer b-screw.
small note- youd think that a 9sp cassette spacer would be perfect, but i got some chain rub in the second-largest cog. the sides of the chain would just be sliding along the 36t. so i used an 8sp spacer instead, no problems.
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Here's to sweat in your eye.
I have tried 20t rings and can say, I had good luck with 9 speed chains and bad with 10.
That could just be me, but I couldn't get it to stop skipping with a ten speed chain. It won't matter sram or shimano, I don't know why someone said that. And you can run 22t 9 speed chainrings on 10 speed cranks just fine, as long as they are 64 bolt diameter cranks.
Go with the actiontec cog if you want. No experience with that.
The 20t 64bcd rings you can get on ebay will work with either 9spd or 10spd chains.
BUT #1 - you have to reduce the diameter of the four bolt-heads so the chain does not ride on them. I reduced mine on a metal lathe, but it could be done with a file and a lot of time.
BUT #2 - you will have to fully relieve the four posts on the crank that the 20t gear attaches too. Bolt the grear onto the crank and wrap the chain around the gear to see where it is touching the bolt-heads and posts then take apart and start filing. Repeat until the chain no longer contacts the bolt-heads or posts.
I've been using a 20t granny this way for a year with10spd chain with no problems.
I am glad somebody has had luck with the ebay 20t, but not me. I can't say I did a scientific experiment, but I went from a 20t actiontec ring with 9 speed that worked fine for a couple years until it wore out, to the ebay ring on 10 speed which skipped from day one.
I was using the same xt crank with the two rings, and I had shaved down the crank pretty good. I proceeded to shave down the bolts(it is easy with Al bolts) and it didn't help. I could shave my crank down some more, but it is getting scary. I even ordered a 21t to see if that would be ok and it skipped the same. This is with sram and shimano chains that are newish or new.
I am soldiering on with a 22t now, but I hate it.
I think the old actiontec rings were slightly square to keep the chain off of the bolt heads which is why they worked (though that also increased the moment arm thus defeating the purpose of a 20t). The ebay ones are fully round. Scary or not, if you wrap the chain around the ring while installed then take apart and file where the chain contacts the bolt heads and the posts on the crank (and repeat until no more contact) you will succed. Work slow and careful and easy uphill pedaling will be yours!
Originally Posted by Gilarider
I followed the good advice of 4crawler above and ground more of my crank off and the 20t works great.
ps the action tec 20t I have is not squared off, it is the same shape as the ebay one.
I think the trick is to take off more material than you think you need. You need to leave a little breathing room for the chain even when things get dirty on the trail. I find I get a little chain lube build-up in between the chain ring and the mounting studs on the crank. I need to take a brush or small screwdriver to those areas from time to time to clear out the build-up. If you just take off enough material to just clear the chain, there is no room for any crud and that may cause skipping.