custom chainrings

[r_mutt]

are there any "rules" for making custom chainrings? i see that there are lots of choices for 110 BCD chainrings. for example what if i wanted to make a chainring using a 53/37 or 52/36? is this too large a gap between the the two chainrings? why am i doing this? i'd rather not have a 50 big ring that comes with the standard compact.

[RPS]

i'd rather not have a 50 big ring that comes with the standard compact.
If you don't mind me asking, what's wrong with a 50T big chainring for your use?

To answer your question directly, a 16T jump is not unusual in larger sizes. It's the normal jump for compacts, and I've seen it used successfully on Shimano 130 BC also. A friend rode a 54/38 ring set for a long time.

Unless you are already using an 11T cog and need more high end I see little reason to go bigger on a compact 110 BC. :confused:

[Charles M]

Tooth count isn't the problem in making rings...

It's shape and ramping detail that are stopping the average person from having someone cut em a new set.

Chainrings are under rated by most in their complexity.

They're farking hard to get right.

[r_mutt]

If you don't mind me asking, what's wrong with a 50T big chainring for your use?

To answer your question directly, a 16T jump is not unusual in larger sizes. It's the normal jump for compacts, and I've seen it used successfully on Shimano 130 BC also. A friend rode a 54/38 ring set for a long time.

Unless you are already using an 11T cog and need more high end I see little reason to go bigger on a compact 110 BC. :confused:

i want to use a 12/25 or a 12/27 cassette rather than an 11/23 or an 11/25. if i had a 50/12, it would not be tall enough going downhill. i need the upper range to climb the mountains, and the lower to catch up to the pack as i get dropped before the top! using somethig with an 11 leaves big gaps in the middle.

[RPS]

using somethig with an 11 leaves big gaps in the middle.
I don't follow what you mean by leaving big gaps in the middle. What cassettes are you comparing?

If I compare an 11-23 against a 12-25 of similar design (say Shimano 10-speed as an example) I find the 11-23 superior. :confused:

In the end it doesn't matter much. You should use what you like best. ;)

[r_mutt]

i use campy. as i said, i need at least a 25 or a 26 (27 if 11 speed), and a 12/25 or a 12/27 works better in the middle of the cassette than an 11/25 or an 11/27. having that 18 is nice. using a 50 big ring would force me to use a 11, and that would spread out the ratios more when using a cassette shorter than a 25. a 50/12 is long enough to descend with and a 34/23 isn't short enough for me to climb with!

[cp43]

I'm running a 44-22 double on my winter comuter. The shifting is not perfect, but very good with a standard Ultegra 6600 FD. You should be fine running a 16 tooth jump between rings.

Chris

[Steve-O]

Can't offer much support but love my 11-26T SRAM cassettes for exactly the reasons you list above...

[RPS]

i use campy. as i said, i need at least a 25 or a 26 (27 if 11 speed), and a 12/25 or a 12/27 works better in the middle of the cassette than an 11/25 or an 11/27. having that 18 is nice. using a 50 big ring would force me to use a 11, and that would spread out the ratios more when using a cassette shorter than a 25. a 50/12 is long enough to descend with and a 34/23 isn't short enough for me to climb with!
When comparing cassettes in this context, the 11/23 is the counterpart of the 12/25 and the 11/25 that of the 12/27. Regarding the importance of the 18T cog, don’t forget that a 53/18 ratio is for all practical purposes the same as a 50/17. The importance of any individual cog size is greatly dependent of the chainring sizes being used because we should think in terms of ratios, inch-gears, or whatever system you prefer, but teeth count alone doesn’t mean much at all if viewed in a vacuum.

In my opinion it makes it easier to evaluate different options by compare them on equal basis (i.e. – avoiding the proverbial apples and oranges comparison). For example, assuming you actually meant that a 50/12 is “NOT” long enough for descending (otherwise the whole discussion doesn’t make much sense to me), I’d compare drivetrains with similar top and low gears. If 52/12 is adequate for custom chainrings (as you requested in the OP), then a 48/11 should also work, right? Given that a 50/34 is the “standard” compact setup, it’s probably best to keep it as a baseline for comparison rather than compare against a 48T chainring that is not as common. However, for high speed descending, a 50/11 is considerably taller than a 52/12. It’s even taller than a 54/12 (not that it should make much difference to most riders).

[sailorboy]

SRAM Red has a 52-36 option. I had one but sold it. Haven't seen another since, so I guess they didn't make a lot of them!

[Tobias]

are there any "rules" for making custom chainrings? i see that there are lots of choices for 110 BCD chainrings. for example what if i wanted to make a chainring using a 53/37 or 52/36? is this too large a gap between the the two chainrings? why am i doing this? i'd rather not have a 50 big ring that comes with the standard compact.
A 52/36 set is relatively common although I don't know if that applies to Campy. For normal 110 BC 5-bolt cranks there have been rings around for a long time. I think when Hamilton first used a compact crankset in a major Tour he reportedly used 52/36 rings.

The only "rule" I've noticed is that the large ring is never greater than 50-percent larger than the small ring; provided the difference doesn't exceed 16 teeth. The two combinations you ask about should work if you can find them. And as you said, there are lots of choices.

When comparing options, the difference between 11T and 12T cogs is about equal to 4-1/2 teeth on typical large chainrings. The difference between 50 and 52 is not as much by comparison. Everything else being equal, it would only represent the difference between descending all out at 50 MPH versus 52 MPH. I think a difference of 2 MPH or less (given you are probably descending somewhat slower than 50 MPH while pedaling) is not as important as most riders think.