General Discussion Triathlon Talk » Chain Ring Rss Feed  
Moderators: jmk-brooklyn, Ron Reply
2013-10-04 8:42 AM


Subject: Chain Ring
Hi Triathletes,

i am building up a new bike. i have decided the frame and wheels. now is the group set.

i am look at the SRAM Force and it new to me as i usually go for shimano.


as i am looking at the crankset for SRAM it offer me the 53/39T combo. so i though of changing it to a 56/42T combo with Sram Force/red crank arm.

but i am stuck and kinda lost. (correct me if i am wrong) i notice Shimano's Chainring there is type A and Type B. i read online that mention type A outer ring best to match with a type A inner ring vice versa for type B.

so now for example if i use a FSA 56T outer chainring with a 130 BCD, 5bolt patten and Sram 42T inner chainring with 130 BCD, 5bolt patten on my crankset. WILL IT WORK???? is there such thing as type A or type B chainring for SRAM,FSA,Vision and etc..

what special tool do i need? any form of adjustment i need to do beside shifting the front D upward for space clearance??

Pros out there, please enlighten me... Z.Z


2013-10-04 8:51 AM
in reply to: 0

User image

Tacoma, Washington
Subject: RE: Chain Ring

Yes, they will work. It's a matter of degree. I've mixed and matched chainrings for 35 years, including 'rings with no ramps and pins. The only thing that's truly needed to match is the BCD (bolt circle diameter) and the number of arms on the spider (5-bolt vs others). Yes, matching Shimano A-types or B-types will work better, but others will work, just may need a little more coaxing to make the shift.

But... a 56/42? Do you really have the legs to push that 56? Most mere mortals are dropping down to compact (110mm BCD) cranks with 50/36 or 50/34 combos...

Edited by briderdt 2013-10-04 8:52 AM
2013-10-04 8:56 AM
in reply to: 0

User image

Knoxville area
Subject: RE: Chain Ring
First... You probably don't need a 56/42 chainring. That's a BIG gear, bigger than most pro's need. Heck, even Tony Martin only used a 58t and he's the world champion.

That said, if you do decide to go that route... yes a 56/42 is fine so long as the bolt pattern is the same.

The things that won't work are something like a 130bcd and 110bcd mix. Also, a big drop in ring sizes from big to small (like a 56/39) can cause shifting issues/dropped chains. 56/42 should be fine.

As to shimano's "A/B" system, it has to do with where the ramps/pins are located on the rings. You match them up for smoother shifting. It is not a big deal though... MANY people have mix/matched a's and b's with success.

*Crap... beat by Dave.

Edited by Leegoocrap 2013-10-04 8:58 AM
2013-10-04 9:59 AM
in reply to: Leegoocrap

User image

Tacoma, Washington
Subject: RE: Chain Ring

Originally posted by Leegoocrap *Crap... beat by Dave.

Hey, at least we agree. Wink

2013-10-05 6:38 AM
in reply to: Ronnieosy

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Greater Pittsburgh
Subject: RE: Chain Ring
A and B chain rings are designed for different inner/outer ring combinations. Type B is the most common, used with 52 or 53 with 39. Type A is the 53, 54, 55 to be used with a 42 inner. There's actually a type E as well, which is 56/44.

But to Chris and Dave's point, very highly unlikely you need a 56/42... about the only pro's riding 56 are the ones on 650 wheels and even at that point, they're very few.

56x12 would give you almost 33mph at 90rpm... and even a 56x19 is well over 20mph. Are you averaging close to 30mph in your races? If not, then you'll be way over geared. Keep in mind that you can average over 25mph over a 40k with a compact (50/34 or 36) and a 12x25 cassette... a 50x12 gives you almost 30mph at 90rpm...
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