53/42 A or B??

Bozabyka
Bozabyka Posts: 252
edited August 2014 in Workshop
I have a 53 chairing type B.
I need a 42 chainring should this also be type B?

Comments

  • Bozabyka
    Bozabyka Posts: 252
    Or do I need a 39 type B?
  • Bozabyka
    Bozabyka Posts: 252
    From what I understand A and B are not compatible.
    Does that mean I can not use a 105 bottom ring/?
  • crankycrank
    crankycrank Posts: 1,830
    edited August 2014
    A & B have different orientations of the chainring teeth to aid shifting. I have used mismatched sets with varying results and shifting being not quite as slick as matched sets but having said that the difference isn't glaring and can sometimes be improved by rotating the inner ring in the mounting holes. Unfortunately I can't remember which way to rotate but experimenting with a few different mounting positions isn't too hard. Obviously it's better to have a matched set but may also work fine if you don't. Most (but not all) people would prefer a 39t to a 42t
  • Moonbiker
    Moonbiker Posts: 1,706
    Dunno but found this thread & now im still confused. Didn't even know chainrings came in A & B types.

    http://forums.roadbikereview.com/compon ... 89160.html
  • Moonbiker
    Moonbiker Posts: 1,706
    Iv'e just bought & fitted this a NOS 105 crank with 42t inner:

    http://velobase.com/ViewComponent.aspx? ... 624d08db10

    Was hoping a Stronglight Dural 39t ring instead of the 42t would work smoothly on it.



    http://www.thetallcyclist.com/2013/01/t ... hainrings/
  • rolf_f
    rolf_f Posts: 16,015
    Moonbiker wrote:
    Was hoping a Stronglight Dural 39t ring instead of the 42t would work smoothly on it.

    I'm sure it will. Sensibly, they are just cogs. No silly orientation shenanigans to worry about. It's all very well having ramps and wierdly shaped teeth on the big ring to aid the downshift but it seems perhaps overkill to muck around with the inner ring which doesn't really need it. The sign of a good inner ring should be the ability to reverse it when worn to double its lifespan!
    Faster than a tent.......
  • Moonbiker
    Moonbiker Posts: 1,706
    Ok thanks shifting seems fine after all, even if shimano say A type rings like mine should only be matched with 42t inner rings.

    Crank is now on with the 38t dural innering fitted,(had to make my own chain bolt wrench as didn't have one) but cross chaining still causing rub on big chainring in the 2 small cogs on rear, whereas with the 42t original on this new NOS crank it was only an issue with the inner one.

    Maybe this can't be helped due to the increase in tooth gap between the rings from 10t to 14t but im finding it annoying as was used to using that second cog at back with the inner ring ( on the old miche monlithic campy crankset 38t-52t it worked without any crosschaining rub). Odd thing is this crank suggested I use a shorter length BB with it which i think would of made cross chaining worse so I kept the old BB from the previous crankset.

    Iv'e spent ages trying to sort out cross chaining rub even bought a hanger aligment tool to measure the chainline etc. Screwing in the B tesion screw on rear derallier seems to help slightly.
  • Moonbiker
    Moonbiker Posts: 1,706
    Sorry OP for the thread hijack. :roll:

    I think with type B ideally you should use a 39t according to shimano.

    If you had type A they are suposedly to be matched with 42t inner.


    In reality it might not be so critical.

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