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  1. #1
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    Anybody ever made a 27t 5 bolt 74mm chainring ?

    As far as I know, TA made them but not anymore. 26 and 28t are common of course, but I'd like to find a 27t 74mm ring. Does such a thing exist ? Would be nifty to find a vintage one, but a newer ring would work too if the tooth count is right.

  2. #2
    GMF
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    How deep are your pockets? For $100 (gulp) you can get a nice CNC 27t 74bcd chainring from Rotor. Why not 26 or 28? 1 tooth isn't a very noticeable difference (although i'd also like to run a 42/27 double on my 110/74 crankset). I'll give rotor credit for channeling the early to mid 90s in their parts, though...

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    My pockets are so deep I'm not sure what to do with it all. I've got 75 dollars in savings, easy.

    Actually I'm splitting hairs over gear inches. I want to run a 1x8 drivetrain. A 28t ring will be great for the high end but a bit low lacking on the low end. 26t would be better there, but it would be lacking on the high end.

  4. #4
    GMF
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    Well, given a $100 chainring may be an impractical purchase, I would recommend a 28t chainring. I believe vuelta makes one for less than $20. I was running a 2x8 drivetrain with a 44/29 in front and an 11/32 out back. The 29/32 low could handle most every climb with a little effort, but I haven't done any huge sustained grinders.
    For reference, single speeders will usually run a 2:1 drivetrain (32-16, etc).

    Basically, I'm getting at it sounds like you are picking a small chainring for a 1x8.

    Good luck, though, and I don't think you'll readily find a 27t. Keep watching ebay.

  5. #5
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    I agree with GMF... a 26, 27, or 28 all seem small for a 1x8. That would be almost like being in your small ring all the time. I could see using this gear on really technical trails - like those around Fruita - but for most riding that seems a really low gear ratio.
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  6. #6
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    Quote Originally Posted by laffeaux View Post
    I agree with GMF... a 26, 27, or 28 all seem small for a 1x8. That would be almost like being in your small ring all the time. I could see using this gear on really technical trails - like those around Fruita - but for most riding that seems a really low gear ratio.
    It all really depends on local terrain, altitude, rider strength, etc, but depending on his cassette, a 28:11 could get you close to 30mph I'm guessing... For short, little climbs (<2 min) you can get away with much higher gears.

    I was doing the math for what I'd need/want if I were to run the new SRAM XX1 (1 x 11) and I think I'd go with the 28 or 30t in front. Granted XX1 has a 10t cog. Turns out it's not really enough range for my favorite trails and would be a bit of a compromise on one end of the range. Now if we could just get a 1x12. I really love the concept, but my trails range from 4mph to 40mph.

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    Quote Originally Posted by Fillet-brazed View Post
    It all really depends on local terrain, altitude, rider strength, etc, but depending on his cassette, a 28:11 could get you close to 30mph I'm guessing... For short, little climbs (<2 min) you can get away with much higher gears.
    It definitely does vary a lot. I've found that although it's theoretically possible to turn the cranks at a high RPM, for me it's hard to do on certain trails. On a geared bike I often find that I spin out a 34/11 or 36/11. I could probably spin that gear on a smooth trail, but when it's rocky and when I'm moving in and out of the saddle, I just can't spin it easily. I'm more comfortable in a larger gear mashing a bit than a smaller gear spinning.

    That said, when I'm on my single speed with a a 2:1 ratio, I'm not pedaling at all downhills and pretty much going the same speed downhills as I do on a geared bike. So maybe "spinning out" early really isn't that big of a deal.
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  8. #8
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    Anybody ever made a 27t 5 bolt 74mm chainring ?

    Quote Originally Posted by phoenixbikes View Post
    My pockets are so deep I'm not sure what to do with it all. I've got 75 dollars in savings, easy.

    Actually I'm splitting hairs over gear inches. I want to run a 1x8 drivetrain. A 28t ring will be great for the high end but a bit low lacking on the low end. 26t would be better there, but it would be lacking on the high end.
    Any 1X setup is a compromise. I do not see enough difference between the 26 and 28 to justify searching for a 27. Pick one of the available rings and struggle SLIGHTLY more on the steepest slopes or coast a bit more on the "fast" bits. You are going to do both in any case.
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  9. #9
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    Quote Originally Posted by shiggy View Post
    Any 1X setup is a compromise. I do not see enough difference between the 26 and 28 to justify searching for a 27. Pick one of the available rings and struggle SLIGHTLY more on the steepest slopes or coast a bit more on the "fast" bits. You are going to do both in any case.
    I agree. I think a 1x setup would work really well for racing since you're not gonna be cruising on the climbs, but I like my bikes to be able to suit those days when you want to enjoy a nice ride in the mountains without having to mash.

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    I am running a 28t ring already. I do struggle a bit on steep climbs, or spin out occasionally. If I had my choice, I'd rather spin out once in awhile than lack low end range for climbing. I was going to change the ring, along with the back cog. With whatever combination I end up with, I want to get a less-than-18 inch low gear.

  11. #11
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    Quote Originally Posted by phoenixbikes View Post
    I am running a 28t ring already. I do struggle a bit on steep climbs, or spin out occasionally. If I had my choice, I'd rather spin out once in awhile than lack low end range for climbing. I was going to change the ring, along with the back cog. With whatever combination I end up with, I want to get a less-than-18 inch low gear.
    What rear cassette are you running?

  12. #12
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    It's a stack of assorted cogs. 7 speed freehub body, 8 speeds. 11-40.

  13. #13
    GMF
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    11-40? Where are you finding a 40t cog?

  14. #14
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    You may as well walk up the hill with 40t. I haven't seen the main players with them but some people have made them custom. Cannondale has put them on a bike somewhere.

    Leonardi Factory “General Lee” 25T – 40T Ten Speed Mountain Bike Cassette Adapter - Bike Rumor

    edit: found the cannondale pic.Anybody ever made a 27t 5 bolt 74mm chainring ?-553469_397467480321848_603392123_n.jpg

  15. #15
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    Quote Originally Posted by girlonbike View Post
    You may as well walk up the hill with 40t. I haven't seen the main players with them but some people have made them custom. Cannondale has put them on a bike somewhere.

    Leonardi Factory “General Lee” 25T – 40T Ten Speed Mountain Bike Cassette Adapter - Bike Rumor
    Wow!!! A 40T rear cog paired with a 22T front would allow you to move backwards when you pedaled.
    Each bicycle owned exponentially increases the probability that none is working correctly.

  16. #16
    gobsmacked Moderator
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    Yeah. I would totally be going backwards with that setup, Laffeaux.

  17. #17
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    Anybody ever made a 27t 5 bolt 74mm chainring ?

    Quote Originally Posted by phoenixbikes View Post
    It's a stack of assorted cogs. 7 speed freehub body, 8 speeds. 11-40.
    IME a 28T ring would be WAY too small with that gearing.
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  18. #18
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    Well it's sure a good thing no-one else is riding my bikes. I set them up for ME, on MY trails. A 28t ring is perfect for most of my riding, the majority of which is done between 5-15 mph.

  19. #19
    gobsmacked Moderator
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    heh! Good use of that emoticon.

  20. #20
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    Quote Originally Posted by GMF View Post
    11-40? Where are you finding a 40t cog?
    Gob is on the right track. It's a 40t chainring bolted to the last (34t) cog with chainring bolts/spacers. Works fine.

  21. #21
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    Quote Originally Posted by shiggy View Post
    IME a 28T ring would be WAY too small with that gearing.
    Standard 3x gearing has a 22:34 low which is lower than the low he's talking about... Not sure why that would be way too low...

  22. #22
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    With a 26" 2.1 tire:

    22x34 = 16.8 gear inches
    28x40 = 18.2 gear inches.

    This is adequate for short hills but a bit of a bear for me on longer hills. I am 6'4", 220 lbs or so, and not the fastest climber. I just picked up a 26.2t (3/32) bmx sprocket that has 'fractional' gearing. Going to buy a 41t cog as well.

    26.2x41 = 16.6 gear inches

    That's a bit more like it. It'll be a bit lacking on the high end but the increased low end range will be worth the trade-off.

  23. #23
    GMF
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    Wow... I remember when a 26x28 was considered a low gear...

    Sounds like a cool setup, though. I'd be interested to see your chainring on a cog setup.

  24. #24
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    Me too. Started riding in 1987. I remember being excited about finding a 26t to replace my 28t, and then later finding a 24!

    Sigh, if only I had the strength I had back then with the big cogs I have now. This 1x8 bike is cool and all, but the ratios I have on my 3x8/9/10
    bikes are CONSIDERABLY more ridiculous.

    It's a good thing my bikes have derailleurs so I can shift into more 'reasonable' cogs when the gear ratio police are around.

    I'll see if I can hunt down a few pics of the 34/40 combo.

  25. #25
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    Here's a couple shots of the 34-40t cog combo. I found a 40t ring with a 3 bolt design at a lbs. I drilled 3 holes in the 34t cog and used chainring bolts, spacers, and 3 washers to attach everything together. Once in awhile I check the bolts for tightness. I've been using this setup and another I made, on my bikes for a couple years now with no issues.

    The Redline Flight bmx cranks were sort of tricky to get working. I drilled the spider to 74mm so I could run a 28t ring, but the cranks are not quite evenly distanced. The driveside is a few millimeters further away from the right seatstay than the left one.
    I thought about a 27t ring because I'm going to replace this spider with a bolt-on sprocket. A 3/32 sprocket for a 19mm bmx spindle from Rennen is just the ticket. It'll get the cranks spaced evenly and be more solid.
    Attached Thumbnails Attached Thumbnails Anybody ever made a 27t 5 bolt 74mm chainring ?-34-40t-cog-spacing.jpg  

    Anybody ever made a 27t 5 bolt 74mm chainring ?-34-40t-cog-attachment.jpg  

    Anybody ever made a 27t 5 bolt 74mm chainring ?-b6-bmx-drilled-redline-bmx-cranks.jpg  


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