I have a bike with an old (1980s) Sugino AT triple crankset (110 BCD; 48-44-28) and I'd like to replace the smallest chainring with one that is 24-tooth. What would be advisable in this case? The crankset is in pretty good condition, overall. Would it be better to just replace the entire crankset? I should mention that the 6-speed freewheel and chain on this bike are new. What brand of chainring would it be best to replace it with if I chose that option?

I'd like to hear your opinions. Thank you!

Whatever brand you decide upon, I'd suggest steel, as opposed to aluminum. The wear rate of aluminum 28T rings is high, especially if used in off-road conditions.

Note that the inner ring BCD on that crank is 74 mm, but then I'm guessing you already knew that. TA generally makes the toughest chainrings, but then you'll pay a premium for those. Sugino chainrings are pretty reasonable.

A bit of detail first. The current 28T is likely attached by it's own bolt circle, a 74mm one. A 24t ring is the smallest that fits this 74mm pattern. One could just swap out the inner rings.


There might be some shifting performance change, slight ft der adjustments too. A 20T shift (24 to 44) is a lot but not impossible. Chain length in the new small/small might sag a bit. Also agree with steel small ring unless wear rate is acceptable.


As to brand I'd first seek a Sugino if Al is acceptable. They're low cost and nicely made. Also the fit WRT the ring to ring spacing (c-c) should be the same.


No reason to change the crankset or BB. But I would change out the middle and large rings, but that's my gearing preferences speaking. Andy

Unless your going to be in the 24 tons, aluminum will be fine. If ur like me its your emergency bailout. Nice to have it as low as possible but not a gear you use a lot.
Ymmv

Spoken like one who has not spent hours in his granny on the same hill before. Andy

Andy, I have a 30" low gear before I get to my granny. I spend lots of time in 40-36 before I go to my 26_tooth granny.

Thank you.

I am curious--what size middle and outer chainring sizes would you prefer? What I have on there now (28-44-48) yields roughly between 23 and 99 gear inches with my current setup (35mm tires). I have been considering possibly getting a smaller middle ring as well, but I do like my bigger gearing in the big chainring.

You should also probably pay attention to Sheldon's advice and get a chain deflector when having that huge a leap. 74 mm BCD Road and Mountain Bicycle Chainrings (Chainwheels) from Harris Cyclery

I'm starting to think that the jump down from the 44 to the 24 would not be the best thing. I know myself and if shifting quality were to suffer so would I! Perhaps it would be wiser at some point to go to a 48-36-24 setup such as the Sugino Alpina 2 crankset. That would preserve my higher gearing and also give me a few inches more at the bottom end.

Thank you all for your comments. They were helpful.

I agree that you should reduce that enormous jump between the middle and small rings. I would strongly suggest spending some time here HTML5 Gear Calculator before spending money on chainrings.

I run 46T big (well sort of, just say outer position) rings on most of my bikes, independent of ring count. A 46/11 is still too big a gear for all but a few downhills, and those are faster in a deep tuck anyways. My middle rings (on triples) are usually a 36T. But I spin and spend a lot of time in the 12 tp 18mph range.


I moved on from half step gearing a long time ago. Although did use it for many years too. Andy

I run a 1.5-step-plus-granny with 12-13-15-17-19-21-24-28 (made from parts of three cassettes) in back and 48-40-28/48-40-24 up front. When I use the 24, I do have to take the 24-40 upshift gently and slowly, but it does work fine with my SunTour XC derailleurs. I like your 48-44 half-step, but by going to 1.5-step you might be able to reduce your granny-to-middle jump and still have a nicely interleaved set of ratios. (Your current jump, before dropping to 24T, is the same as my 40-24, which, as mentioned, does push the envelope somewhat.)

I prefer steel granny rings on my commuter and mountain bikes, they last longer than aluminum. Rivendell sells the Sugino steel 24t chainring in 74 bcd, for not a bad price. The alloy version is available from several sources, such as Universal Cycles.
https://www.rivbike.com/products/sug...74-x-24t-12027
https://www.universalcycles.com/shop...6&category=650

This is a good plan. The 36 will keep you out of the 24 in only the most extreme circumstance and shifting will be easier. Frankly with friction shifting I don't have much trouble going 26-46. I don't have that setup anymore but it worked well with an old school suntour FD.

I also use step and a half gearing, in my case 47-40-26 chainrings and a 13-30 9-speed cassette, and a 48-42-28 with 13-34 cassette on another bike. Both cassettes are custom from Harris: Cassettes 9-speed - Harris Cyclery bicycle shop - West Newton, Massachusetts

BTW, I don't have significant issues with the shift between middle and small chainrings.

My blog post on gearing choices, with some examples, here: https://valvejob.wordpress.com/2011/...gear-sequence/

52telecaster- Perhaps I read your post wrong. The "24 tons" comment didn't make sense till later. I suspect we are far closer to agreement based on this "The 36 will keep you out of the 24 in only the most extreme circumstance" as I do much the same. I have been on the same hill for 4+ hours at a time a few times in my touring life though, up to 500 feet of elevation a mile with 70+ pounds of load takes it's toll on me. At these times a gear low enough to have balance challenges is about low enough. Andy

+1 on Andy's and T-Mar's always valuable suggestions, as well as Andy's thoughts and experiences regarding typical speeds and time going up long hills.

I've been using it 46-36-24 chain rings on triples for several years and loving them with 12-28 or 12-30 cassettes. Nearly all my time is on the 36T ring, with the 46 for long downhills in the mountains or the rare downwind leg, but the 24T grannies get regular daily use up the steep local Seattle hills, as well as more moderate hills when touring with panniers. I'm using a Riv-supplied Sugino steel 24T ring on one bike, and an older Shimano steel 24T on the other. They last and last, compared to aluminum granny rings.

The OP's Sugino AT cranks (which are fabulous and quite pretty cranks, BTW. Keep them!) will take any 5-bolt 74mm granny ring.

I can appreciate that half-step gearing might be preferable with only 6 cogs in back.

Yup -- yet another acknowledgment of the superiority of non-indexed shifting up front, irrespective of what one likes for the rear derailleur.

Andy, its just possible you have done way more climbing than I have! 4+ hours in the granny would be pretty rough. I like to keep it fairly simple gearing wise which is why I go with the 40-26 up front but if I had to face the climbs ur talking about I might go with a triple.

Bet ur quads are monsters.

No, if they were I wouldn't need such low gearing Actually I find climbing is as much as what's between one's ears as it is a strength thing. Around here (Finger Lakes) we have climbs of 500 to 900 feet over a mile+ to a few miles. But out west has some real mountains. Andy

Oh, so this is not as much an issue with plain friction shifters; because that is what I have on the bike.