Stupid chainring questions

[kevinvc]

I bought a used bike that has a Dura-Ace double crankset. The bike rides great, but I need better climbing gears. The big ring is stamped SG-X 54-A. I don't know what the smaller ring is, but I'm assuming its 54/42 since that seems to have been the standard pairing with a 54.

I think a 52/36 would probably do ok. I don't race, but do go on group rides. I do a lot of climbing but don't go very fast on the flats anyways. Can I buy 6700 Ultegra rings in those sizes and throw them on without any other modifications? Is there a better strategy?

Thanks for the insight.

[oldpotatoe]

I bought a used bike that has a Dura-Ace double crankset. The bike rides great, but I need better climbing gears. The big ring is stamped SG-X 54-A. I don't know what the smaller ring is, but I'm assuming its 54/42 since that seems to have been the standard pairing with a 54.

I think a 52/36 would probably do ok. I don't race, but do go on group rides. I do a lot of climbing but don't go very fast on the flats anyways. Can I buy 6700 Ultegra rings in those sizes and throw them on without any other modifications? Is there a better strategy?

Thanks for the insight.

Probably 130mm BCD and smallest small ring is 38t. But easy to find 52/38 rings, TA rings is a good suggestion.

[Ken Robb]

I think our experts need more info: what is bolt circle diameter, type of derailer, shifters, crank model? I gather this is old stuff. 6 or 7 speed perhaps? You might want to get bigger cogs out back instead or in addition.

[kevinvc]

Sorry for the lack of details. It's a 7800 10 speed group. Cassette is Ultegra 6700 11/28. BB is 7900. Shimano's spec sheet (http://www.shimano.com/media/techdocs/content/cycle/SI/Dura-Ace/FC-7800-7803/SI_1F30H_En_v1_m56577569830605111.pdf) for the 7800 group says the BCD is 130 mm. I don't know the inner ring size for sure, but I'm assuming it's 42 since that seems to be the standard pairing with a 54.

[shovelhd]

What chainrings are on it now?

[kramnnim]

I've been using 52/26 for some time and like it a lot.

If your 7800 is in nice condition you could probably sell it and buy a crankset with 52/36 rings.

[Ken Robb]

I've been using 52/26 for some time and like it a lot.

If your 7800 is in nice condition you could probably sell it and buy a crankset with 52/36 rings.
52/26?? Nah, must be 52/36 huh?

[kevinvc]

I've been using 52/26 for some time and like it a lot.

If your 7800 is in nice condition you could probably sell it and buy a crankset with 52/36 rings.

It is in good condition. I wouldn't have any idea what it's worth, but I could probably sell it.

I can't find 52/36 listed anywhere as a 10 speed; only 11. There seem to be 52/39 around, but I don't know how much of an improvement that is for climbing compared to what I have now.

[11.4]

I don't know the inner ring size for sure, but I'm assuming it's 42 since that seems to be the standard pairing with a 54.

Ummm, count the teeth?

And that's a Shimano stamping so in that size range in that version of crankset it's a 130 mm BCD, right?

[AngryScientist]

7800 cranks were never available in compact BCD, so you're at 130. smallest inner ring is 38t, easily findable, just like a 52 outer.

[dcama5]

Just as both Old Potatoe and Angry Scientist have already said, a 38 is the smallest you can run on a 130BCD. I ran a 50X38 at one time because I didn't need anything bigger than a 50X11.

[OtayBW]

I've been using 52/26 for some time and like it a lot.

Yow!

[rburnham13]

7800 cranks were never available in compact BCD, so you're at 130. smallest inner ring is 38t, easily findable, just like a 52 outer.

This is spot on. If you want smaller go with a compact crank 110 BCD

[kevinvc]

Thanks for all the info.

A friend of mine has a an old 6500 crankset with a 48 / 38 set of rings in 130 that he says should work. Is this something I can just slap on or will I need to adjust cable lengths, derailleur height, chain length, etc.? Is this a weird combo to try out?

[Ken Robb]

Are the rings ramped/pinned like yours? I think you will at least have to shorten chain, lower derailer, adjust cables.

[kevinvc]

Yes, they're ramped and pinned. The other question I have is that 6500 is a 9 speed group. My 7800 group is 10 speed. Will this create a compatibility problem?

[Ken Robb]

6500 uses Octalink BB. I don't remember what you have for a BB now with 7800 group.

[djg21]

6500 uses Octalink BB. I don't remember what you have for a BB now with 7800 group.

The 7800 crank has an integrated BB spindle.

[kevinvc]

I currently have a BB 7900. The intranets lead me to think it is not compatible with the 6500 crankset, but I don't know if the rings are interchangeable.

[11.4]

I currently have a BB 7900. The intranets lead me to think it is not compatible with the 6500 crankset, but I don't know if the rings are interchangeable.

The bottom brackets are incompatible. I don't recall whether you have a threaded bottom bracket shell or a press-fit version. You can get adapters that let you use an Octalink bottom bracket (which only came threaded) in a BB or PF bottom bracket, but it's probably not the ideal way to get a crankset on your bike. If you need lower gears, why aren't you just looking at a 6800 Ultegra bottom bracket? You can get them for prices that are less than used 7700, 6500, or 7800 cranksets are going for.

[kramnnim]

My fingers are fat and typing is hard. :p

48/38 is kind of odd, and yes, you would have to move the FD down. Chainrings would fit on your crank arms just fine.

A 52/36 11sp will work just fine with your 10sp stuff.

[fogrider]

What size cogs are on the cassette? You should be able to get a 27 in the rear, which should help with a 38 in the front.

[kevinvc]

I'm being convinced to switch to Shimano 9000 rather than just get new rings. The flexibility of ring options with the 4 bolt system is appealing and people seem to believe that the overall performance is an improvement over previous generations, although that could just be drinking the Shimano-ade.

I'm trying to figure out if I should upgrade my bottom bracket as well as the crankset. Does anyone have firsthand experience comparing the BB 7900 to the 9000 or Chris King?

[djg21]

I'm being convinced to switch to Shimano 9000 rather than just get new rings. The flexibility of ring options with the 4 bolt system is appealing and people seem to believe that the overall performance is an improvement over previous generations, although that could just be drinking the Shimano-ade.

I'm trying to figure out if I should upgrade my bottom bracket as well as the crankset. Does anyone have firsthand experience comparing the BB 7900 to the 9000 or Chris King?

I use a 7900 crank with Praxis mid-compact rings and a CK bottom bracket. I've used a 7900 BB in the past. I just like anything made by Chris King. I have the CK grease injector tool for the BB, and regrease it a couple of times each season. My sense is that any gain in actual improvement resulting from the CK BB is probably marginal, but CK stuff is great and just lasts forever.