Cycling Equipment · Public discussion

Bottom bracket , frame dimensions

Started by nath1 · · Last activity · 8 posts · 820 views

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Cycling Equipment
Published
28 April 2006
Last activity
28 April 2006
Original author
nath1
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8
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  1. Hi , i have just finished building my training bike, and have so far spent about two weeks training on it, and doinig lots of power training, ready for some time trials. I noticed when i was building the bike up ,that the bottom bracket which is for a double ( 110 square taperd) has what seems an iregularity. With the crank arms tightly secured onto the bottom bracket there is a 4 mm diffrence from the chainstay part of the frame to the inside of the crank arm. I have put the crank arm on the chainwheel side at 9 o clock and measeurd with a vernier gauge and it is the same as my racing bike,perfect, but the other side when the crank arm is in the same position is about 4 mm diffrent away from the chainstay. The reason it bothers me so much is that i have began to get an irratation on the Iliotibial band area of the knee when riding and i cannot help but think it it due to this diffrence in measurement, on the other hand i thought it could be just the heavy workload at the mo.Should the both crank arms be the same diffrence from the chainstays when the padals are pointing to the rear and in line with them. Im using a shimano tiagra chainset , and i think a low range bottom bracket which is also shimano( I think it too is tiagra) . I have a good cycling book and i have referd to it for advice on the injury and it says that normally it is a narrow bottom bracket that causes Iliotibial injurys, but i have no probs what so ever on the narrow side with regards to my knee . I thought i would ask before i start to spend money, as just going out and buying a new chainset or bottom bracket may not be the answer. Thanks in advance nath.

  2. What brand BB; shimano or campy? What width shell? Shimano square taper double with a 68mm shell calls for a 107 width.

  3. Yes good question, but all i know is that it is a tiagra 110mm square taper for a double chainset.Could you elaborate? do you think that it is poss i neededthe 107, that would that then pull in the left hand crank thanks

    capwater said:

    What brand BB; shimano or campy? What width shell? Shimano square taper double with a 68mm shell calls for a 107 width.

  4. nath1 said:

    Hi , i have just finished building my training bike, and have so far spent about two weeks training on it, and doinig lots of power training, ready for some time trials. .....

    .....The reason it bothers me so much is that i have began to get an irratation on the Iliotibial band area of the knee when riding and i cannot help but think it it due to this diffrence in measurement, on the other hand i thought it could be just the heavy workload at the mo.

    Are you bending your knees inward when you pedal? That would cause the IT band problems. I bet you are just working too hard too soon. I don't think that a few MM will make that much difference.

  5. nath1 said:

    Yes good question, but all i know is that it is a tiagra 110mm square taper for a double chainset.Could you elaborate? do you think that it is poss i neededthe 107, that would that then pull in the left hand crank thanks

    Are you saying one side is 4mm further out than the other? If so, the BB is too long. 110 -107 = 3 (damn close to your 4mm measurement)

  6. Yes that is right, the left handside is 4mm further out,i did not realise they do a 107mm bb; thanks nath

    capwater said:

    Are you saying one side is 4mm further out than the other? If so, the BB is too long. 110 -107 = 3 (damn close to your 4mm measurement)

  7. 68x107 18 bucks.

    http://www.nashbar.com/profile.cfm?category=73&subcategory=1096&brand=&sku=8104&storetype=&estoreid=&pagename=

  8. Thanks for all your help, much appreciated nathan

    capwater said:

    68x107 18 bucks.

    nashbar.comprofile.cfm

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