Chainring Question- Mtbr.com
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  1. #1
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    Chainring Question

    Hi all,
    please bear with me because I am still learning the proper terminology.

    Thanks in advance for any help.

    Notice how the spider in the circled area is nearly close to the valley on the chain ring.
    How much clearance is need to not effect the chain?
    Will this chain ring work on this crank?
    if not, how do avoid making the same mistakes when buying the next chain ring?



    thanks,

    chs

  2. #2
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    Wrap the chain around the ring and check the clearance. Odds are you'll have plenty.

  3. #3
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    that's more of a crank problem than a chainring problem. All 32t chainrings (or whatever tooth count you choose) will have the same chain/spider clearance as the next ring, unless you change the tooth count. You can file a little flat for clearance on there if need be. Most cranks have less material than that, so you should be fine. What crank/ring is that? How many teeth?

  4. #4
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    Quote Originally Posted by ISuckAtRiding
    that's more of a crank problem than a chainring problem. All 32t chainrings (or whatever tooth count you choose) will have the same chain/spider clearance as the next ring, unless you change the tooth count. You can file a little flat for clearance on there if need be. Most cranks have less material than that, so you should be fine. What crank/ring is that? How many teeth?

    thanks

    hey --

    you saved me a PM. I was just looking at your site. Very nice looking stuff.

    The crankset is a Bontrager giga-x-pipe 7050 that I bought recently. I don't know the model but it has a 5 bolt design. The chainring was
    given to me so I am uncertain the make and model. That chainring is 40T which is fine for me playing bike mechanic and learning about how to build drive trains etc.

    I may just try to sell the crankset and buy a truvativ stylo 1.1 since so many people have
    said it is a great value. Who knows, my old tired legs may not appreciate a SS. It has been
    more of a winter project for fun to help me learn more about bike mechanics.

    I have to assume that the diameter of a 40T is greater than a 32T chainring and in turn the crankset might not even work for a SS.

    I am slightly overwhelmed....

  5. #5
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    Quote Originally Posted by -chs-
    thanks

    hey --

    you saved me a PM. I was just looking at your site. Very nice looking stuff.

    The crankset is a Bontrager giga-x-pipe 7050 that I bought recently. I don't know the model but it has a 5 bolt design. The chainring was
    given to me so I am uncertain the make and model. That chainring is 40T which is fine for me playing bike mechanic and learning about how to build drive trains etc.

    I may just try to sell the crankset and buy a truvativ stylo 1.1 since so many people have
    said it is a great value. Who knows, my old tired legs may not appreciate a SS. It has been
    more of a winter project for fun to help me learn more about bike mechanics.

    I have to assume that the diameter of a 40T is greater than a 32T chainring and in turn the crankset might not even work for a SS.

    I am slightly overwhelmed....
    glad you like my stuff!
    As for the crank, i gotta assume it's a 130bcd if that's a 40t, and that wouldnt be very good for mtb use. The smallest you can go is about what you have with that clearance, maybe a 38t if you filed it down.
    I'd go with a Shimano SLX. They're much better than the stylos IMHO and pretty similar in cost. You can find them around for $120 new online, with the rings and bottom bracket. You can sell the stock rings (they're for shifting, not ideal for singlespeed use) and it'll pay for a nice singlespeed ring and then some. Also, they generally dont need modification like the truvativs if you decide you want to drop to a 31t (not a huge deal).
    The stylos arent horrible, but i couldnt get much life out of the bottom brackets. First one died the first time it got wet (in about 2 weeks of riding). The seals arent as good for harsh conditions as the Shimanos, IMHO. Of course opinions are like...........

  6. #6
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    Quote Originally Posted by ISuckAtRiding
    glad you like my stuff!
    As for the crank, i gotta assume it's a 130bcd if that's a 40t, and that wouldnt be very good for mtb use. The smallest you can go is about what you have with that clearance, maybe a 38t if you filed it down.
    I'd go with a Shimano SLX. They're much better than the stylos IMHO and pretty similar in cost. You can find them around for $120 new online, with the rings and bottom bracket. You can sell the stock rings (they're for shifting, not ideal for singlespeed use) and it'll pay for a nice singlespeed ring and then some. Also, they generally dont need modification like the truvativs if you decide you want to drop to a 31t (not a huge deal).
    The stylos arent horrible, but i couldnt get much life out of the bottom brackets. First one died the first time it got wet (in about 2 weeks of riding). The seals arent as good for harsh conditions as the Shimanos, IMHO. Of course opinions are like...........

    if my math is correct and I understand how Sheldon Brown determines BCD, it is 125. 5 bolt design, measured middle of one hole to middle of closest hole (74mm) multipled by 1.701 = 125MM. Does that sound right to you? The inner spider arm is roughly 42mm multipled by 1.701= 71BCD.

    Thanks for the suggestion on the Shimano SLX.

  7. #7
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    I'm pretty confident that it's 130bcd, but I've been wrong before. That's a typical road crank bcd, and it looks about right, given that it's a 40t. You'd have more clearance if it was 125bcd.

  8. #8
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    Quote Originally Posted by ISuckAtRiding
    I'd go with a Shimano SLX. They're much better than the stylos IMHO and pretty similar in cost. You can find them around for $120 new online, with the rings and bottom bracket.
    Instead of the SLX, take a look at the LX on Jenson for only $79. You can't beat that deal. Also, I totally agree that the SLX or LX is much better than the Stylo.

    http://www.jensonusa.com/store/produ...+Crankset.aspx

  9. #9
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    Quote Originally Posted by ISuckAtRiding
    I'm pretty confident that it's 130bcd, but I've been wrong before. That's a typical road crank bcd, and it looks about right, given that it's a 40t. You'd have more clearance if it was 125bcd.
    thanks -- I think I may be listing it on ebay. Look for my order someday down the road.


    Quote Originally Posted by bad mechanic
    Instead of the SLX, take a look at the LX on Jenson for only $79. You can't beat that deal. Also, I totally agree that the SLX or LX is much better than the Stylo.

    http://www.jensonusa.com/store/produ...+Crankset.aspx

    thanks for the headsup -- I will research it

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