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Old 05-19-14, 05:52 PM   #1
tedi k wardhana
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20t chainring, who needs 'em? I do!

right after i got myself a rigid steel 29er, some folks here who are not so familiar with 29ers, would comment: "this thing is heavy to ride uphill!"
they might have misunderstood. maybe it is heavy, when equipped with the gearing of 26" wheel, since 29er has bigger diameter than 26.
so i searched the net, and found some nice threads about low gearing for 29ers.
i am aware that one option is to get the 11-36t cassette sprockets.
but i am a cheapskate. so i looked the other way. i looked at the option of putting a smaller chainring.
at the local market, someone is selling new old stock 42-32-20 crankset. $40. but still it's expensive for me.
and then i found a thread of 20t chainring conversion.
wow. stambeco mountain goat 20t. actiontec. still expensive.
so i decided to make my own.
took a $1 20t steel cog. ground the teeth manually to make it thinner to accomodate 8sp chain. drilled 4holes bcd64(?). and put that on my existing $20 FSA crankset, replacing the 22t.
there were some more grinding of the spider to give more chain clearence, just like it was explained in the 'stambeco 20t chainring conversion' thread.
voila! now i have low gearing of 17 gear inch. 20t chainring with the 34t sprocket.
17 gear inch on my rigid steel singular swift.
thank you all for your inspirations on the internet!
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Old 05-24-14, 09:57 PM   #2
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You just fitted gearing slower than you can walk the bike!
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Old 05-25-14, 12:46 AM   #3
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Love hearing stories of shade-tree fabs and mods. Way to improvise, tkw
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Old 05-25-14, 01:27 AM   #4
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My second bike has a chain-ring of equal size to the granny sprocket on the rear cluster. I'm finding I like that more lately. I am in a hilly area and it means I can ride up the hills rather than walk. Walking hurts my ankle so, yeah, I like it!
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Old 07-19-14, 04:17 PM   #5
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Good thread - I'm wondering about 26 vs 29 just for the lower resulting gearing on the 26. I'm in no hurry and have steep climbs.
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Old 07-22-14, 10:20 AM   #6
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20 tooth?!? Heck, I want an 18 tooth crank ring for my touring mountain bike conversion/upgrade. It might be "slower than I can walk" but I don't like walking up hills and I'll be pulling a trailer.
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Old 10-10-14, 12:45 AM   #7
tedi k wardhana
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after several months with this setup,
I think I'd write a quick review.
the diy 20t chainring is doing just fine.
on some hilly trails, it just feels good to have a
34t biggest cog as bail out.
combined with one dollar non indexed thumbshifters
positioned under the bar,
i am just fine.
yeah, people may search and eventually find out that my
frameset's pricelist is 475gbp. (they don't necessarily have to know for how much i got it second hand.)
but i feel comfortable with the cheap parts on it.
at least i know it's reliability..
cheers!!
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Old 10-11-14, 01:17 AM   #8
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Good mod work,
same low gearing if U would have swapped the 11-34 cassette to 12-36, cost about $69 and no work.
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Old 10-15-14, 06:49 AM   #9
tedi k wardhana
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forgot to add.
i decided to remove the 42t outer chainring.
replaced with a used $10 fsa gravity bashguard.
so, my bike is 2x8 now.
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Old 10-27-14, 04:19 PM   #10
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Good mod work,
same low gearing if U would have swapped the 11-34 cassette to 12-36, cost about $69 and no work.
you are right osco53!
but for me, $69 is something
while the one dollar 20t cog-into-chainring costs me almost nothing.
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Old 11-13-15, 03:46 AM   #11
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i have moved one step further.
found out i could modify a 94/58 bcd crankset, replace the 22t or 20t smallest ring with a 19t.
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Old 11-13-15, 12:43 PM   #12
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My 26er came with a 22-28 bottom gear, so I can see how a 22-32 would be good on a 29er. But I don't think I could keep the bike upright with gears much lower than that.
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Old 11-13-15, 06:04 PM   #13
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Running 1 x 11 now,, 32 up front and 11-42 out back.. 27.5 full squish, I have a silent drive train now. I am happy



Shimano Deore XT M8000 and a Race Face Narrow wide up front,,,no chain guard, I never drop the chain,,
Externally user adjustable clutch,,good stuff...

very affordable,,, google it

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Old 11-13-15, 11:02 PM   #14
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Mine's a 29'er with 32 up front and 11-40 out back --- I'm in that 40T more than i care to admit and considering going to a 42 rear cog paired with a 30 front for another trip to the mountains soon--- If i'm spinning at 110 rpm, -- still faster than walking
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Old 11-14-15, 05:20 AM   #15
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I never could spin the little granny ring very well, Always seemed to be, 'Chopping Wood' so to speak.

And when the need arises and I shifted down to the little ring I'd loose so much momentum. Then I noticed I was no longer using it... or the big ring.
The side benefit was the bike lost 1.1 pounds taking off all the front shifting junk.
Two front rings and spacers.
Trigger shifter,
Front Derailleur,
Cable and housing,

Made for a much cleaner looking cockpit also.
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Old 11-21-15, 09:50 AM   #16
tedi k wardhana
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dear friends.
what i did was nothing extreme.
if you got a calculator, you can see that what i tried to replicate was the lowest gear on your 26er.
22front with 34t at the back yields 16,8 gear inch.
with my 20t front and 34t at the back on my 29er gives me 17gear inch..
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Old 09-21-16, 11:24 PM   #17
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It's been a while now.
I finally found a bcd94/58 crankset 42-32-22.for usd18 And finally had the cash to buy a 20t chainring for usd10.
Sugino impel 42-32-20.
So now the diy 20t (and fsa crankset) goes to a friend.
Good bye..
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Old 09-26-16, 10:02 AM   #18
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Way to go Tedi!
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Old 09-27-16, 09:18 AM   #19
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Seems like way too much work. All you needed was a 36 T cog for the cassette. Take off the 34 and replace.
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Old 09-27-16, 09:29 AM   #20
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Yeah 29ers need much lower gearing for steep long climbs. I'm running 20/40. With 22 in front it requires 44 teeth in the back because two less teeth in the front is roughly the equivalent of four more teeth in the back. Manufacturers need to return to 58/94-BCD triple crank production for these new bigger/fatter wheeled bikes. By the way, for people who want to run larger range cassettes but don't to buy new rear dérailleurs or shifters, Wolftooth makes an extension called the Goat Link and they work great. For 9 speeds running 40-42 teeth you'd buy the roadie version Goat Link. I made my own custom 9 speed 14-40 cassette but in the future I'll probably just buy a 10 speed cassette and leave the small cog off (with the thinner chain?).

I like this gearing so much I did the same thing to my 26 inch bike, 20/36 is about the equivalent gear in this case. I consider the hill unclimbable if this gear won't do. The lower gearing is for actual mountain rides daily, not just dirt trails or occasional rides. I have no sore legs the next day. If the thought of climbing a steep mountain has you wondering if you mow the lawn instead this is an indication you need easier gearing.

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Old 09-27-16, 10:11 AM   #21
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Seems like way too much work. All you needed was a 36 T cog for the cassette. Take off the 34 and replace.
One larger gear in back isn't the same as lower gears everywhere. Your legs will thank you.
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Old 09-27-16, 11:08 AM   #22
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My 22-36 gets me up any hill I've been to in New England. YRMV. If it works for you great.
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