Bill Kapaun

It's not written in stone. Sometimes they can change due to parts availability etc.


Is your smallest cog 12 or 13T?

oldschoolbike

If the crank is really 130/74 BCD, then the OP can add a 74 mm BCD granny ring as small as 24T easily. The bolt holes are there. Ignore or remove the outer ring if high gears are not needed, and the rear derailler will probably be fine. Lower the front derailler, shorten the chain, and (probably) fit a bottom bracket cartridge about 7 mm longer. For best shifting to the 39 T, using a "middle" chainring will provide shift aids. 39T may be too small anyway, an excuse to look for a 44 or 46 tooth "middle" ring for use as the bigger of two rings. Specialities TA or Spa Cycles. Going triple (ie keeping the outer ring) will definitely require a long cage derailler and a longer chain.

I am running a Campagnolo 135/74 mm BCD triple as a 46/30 tooth double, and it's great for me at 67 and still climbing.. I have the rings for two more "downgrades" as time passes.

oldschoolbike

KCT1986

You should double check your actual eqmt. The bike may not have the exact parts in the listing. It may have had changes made to it, at the purchase point or later. What you stated in your original post is different from the specs on the site and also from the 98 catalog.

Things to check and post are, rear derailleur, front derailleur, crankset & chainrings. Also, when checking the chainrings, verify that it is still in OK condition. Parts should have a model # stamped on it, usually on the back side in small characters, e.g. FC-A550 for the crank.

A few of the suggestions are for a triple crankset, which doesn't seem to be confirmed. The 53/39 combo is more common for doubles.

Jeff Wills

The bolt holes aren’t there. The RX-100 crank only had the 130mm bolt circle and nothing more.

130mm/74mm triple cranks would not appear until the early 2000’s, ten years after this bike was made.

Duragrouch

Why bother? On amazon there are 50/34 cranks on smaller BCDs for the same price as just chainrings, and if hollow spindle, often coming with new external bearings. Key is to find one "road" with a low q-factor, if desired, like me.

Kontact

And why bother with that, when the OP has such a narrow gear range right now and may get everything he needs with a 28t low cog? There are lots of places where the hills are neither particularly steep nor long.

Duragrouch

Totally agree. I just meant if they were decided on changing the chainrings.

KCT1986

There was a RX-100 triple crank, marked '-T'. This was from earlier than the OP's bike, about '92 (7 speed group). It was one of Shimano's early use of 130/74 triple for road. Followed a few years later with the FC-1057.

Thus, triples were made by Shimano. Probably not standard on OP's bike. Reason that the post before your asked OP to confirm the parts.

t2p

I had two early 90’s Cannondale road bikes - R400 and R800 / 900

the R400 was a 7 speed - the R800 / 900 was a 8 speed

first thing I did to the drivetrain was to change the rear cassette to a 12-28 cassette

I was able to use the existing chain and rear derailleur with no changes

as others mentioned - a cassette change would be a good first / easy step … cassettes are available … 12-28 … maybe 11-30 or 11-32 depending on your rear derailleur … ? … a new chain should also be used with a new / different cassette

if the cassette change alone does not provide lower gears - your current crankset might be limited to 38t small ring minimum (which would barely be a change from your current 39t) - so a new / different crankset (maybe a compact 50-34 or whatever) might be the next possible step

70sSanO

There are a couple of directions to go.

The first consideration is if your shifters, and the rest of your drivetrain, will last another 5 years or so. It might be foolish to invest in 8 speed if 20+ year old STI’s are on their last leg.

The other consideration is the chainring you predominantly ride in. If you are pretty much always in the 39, then you need to replicate enough of the gear inches in a new big ring. This is even more so with newer cassette 1st position 11t vs 13t.

Personally, I’d opt for a new 46/30 crank if you ride in the 39t. You might be able to squeeze out a 30t on that Cannondale. I’ve found their hangers to be generous.

The downfall of going from a 13-23 to 11-28/30 8 speed is wider gapping. It might be possible to find a 12t. 13t/14t are gone unless you are enterprising and have some stash. All this brings you to whether you can live with the gapping with only 8 speeds. All the what-ifs in the world are useless if you don’t like the finished product.

John

oldbobcat

39 is as low as you can reliably go on a 130 mm BCD. I've seen 38s, but for the single-tooth gain they aren't worth the bother. At the first hint of wear on the teeth and chain, the chain starts to skate over the nuts or spacers between the rings.

Iride01 

If the shop is correct and your ring or rings on the crank is worn too much, then almost none of your other options will work. Or at least you should be prepared to have to replace the crank or rings too.. I replaced a chain and cassette once only to have the new chain skip on the rings occasionally while putting a lot of power into the cranks.

Luckily I already had a new crank coming that hadn't arrived yet.

bboy314

In my opinion, a bike you’ve had for 20 years that rides well and fits you is worth dropping a couple hundred bucks on to refresh/change the gearing. I’d recommend the 50/34 crankset, new chain, and new cassette, possibly a 12-28 tooth or so. I live and work in a shop in a very hilly town in New England and we routinely make these changes for customers who are aging and want to keep riding a road bike they’ve owned for decades, and they tend to be very happy with the results.

Kontact

I hate to go against the popular theme, but you can buy a pair of replacement 53/39t chainrings for $30 delivered. So it isn't cheaper to replace the whole crankset.

Jeff Wills

Point taken. Thank you.

Odd that the RX-100 version appeared before the 105SC. AFAIK they were identical except for the painted finish on the 105SC.

Duragrouch

That's a good price. So perhaps. However in my case, a 50/34 hollow spindle crank, including BB bearings, on sale for $52 (20% off $65), was a deal-and-a-half, as I needed a new BB also. I sure hope they get more of that crank in stock on amazon, been sold out for a long time.

Ah, there's a different one now, same setup, 5x110 BCD, but 11 speed and 175mm arms, $58 with BB bearings:

https://www.amazon.com/SAMOX-R3-Cran...dp/B088XSYQ8H/

Kontact

The cranks weigh differently, recall the shifters were different, etc. Not the same.

Kontact

But, that is ugly no-name potential garbage. The OP has a nice all RX100 group, and maybe just slapping random stuff in its place is unappealing. It's unappealing to me.

The OP could also find some lightly used chainrings for a very few bucks.



In general, people on this forum seem to love suggesting swapping this and buying that, forgetting all the potential downsides to doing so. A replacement 50x34 crank may sit too low for the front derailleur - that was a very common problem with compacts when they first came out. That RX100 crank is relatively low Q and has lots of ankle clearance - a replacement might give the OP fit problems or rubs.

I would be surprised if someone getting by with a 23t low suddenly needs 1:1 gearing for the rolling hills he rides on. It is simply bizarre that keeping things simple with a 28t isn't everyone's first suggestion. Does everyone on BF live in the mountains, or just have bad knees?

Duragrouch

Agreed, aesthetics do matter. That was why I wanted a 5 arm crank and not 4. But everything aftermarket seems black these days, not matching a bike with classic silver. It's cheaper to paint than polish. As to the quality, that cheap crank I got is just superb. I had originally ordered a square taper triple, but with my very fat seat tube, it wouldn't fit, FD would not go in far enough, and, it really was cheap and weighed a ton. The hollow spindle double I got is better in every respect, and even has low Q-factor, a priority to me.

I'm not in the mountains per se, but a west-coast city on the water, and roads perpindicular to the waterline can get really steep. I do have a bad knee, it bothers me more walking, but I can't push a tall gear hard with either leg if sitting, it's either spin up in low, or stand and climb two gears up. Going down, I need a disc bike, bad.

siearly

Double checked and it is 13.

siearly

So I appreciate all the information. Here's some more data.

RDRL is a Shiamano 105
FDRL is a Shiamano SM-AD11, that's all the markings I could find
Crank is a Shiamano RX100

I feel my current gearing is too closely spaced and I frequently skip multiple gears. I also find that there is too much overlap (i.e. small crank gear with small cassette gear is higher than large crank gear, large cassette gear.

Based on advice here, I've ordered a Shiamano Claris FC-R2000 crankset (50/34). I've made an appointment at the local bike coop to help me install it with a new chain. We'll evaluate the cassette at that time.

To provide more info on the riding conditions here. I'm in SE Pennsylvania in Avondale. We have what folks like to call "rolling hills". I can handle most of the terrain currently but where I struggle are the rather steep hills that are longer. I see others doing those on the small ring of a triple. I've tried that and it is sooo much easier for me.

Duragrouch

Yep. In flat land, I rode my road race bike with 52/42 for well over a decade. Moved to a place with hills, it wasn't long until I traded that out for a triple. But that was before wide doubles.

Bill Kapaun

I love closely spaced gears.
I often shift 2 at a time when accelerating.
Once up to speed, I can shift 1 tooth as head/tail winds change slightly or the slope has slight changes and maintain the narrow cadence range I need.

You WANT "some" overlap between rings, else you can get in a scenario where you are constantly making double shifts back & forth under the conditions encountered in part 1 above.

Duragrouch

I dunno about that. If, theoretically, you have a big enough difference in chainrings so that there is no overlap, then you start on the small ring, go through the entire cassette, switch to the big ring, then go through the entire cassette. Sequential. Bromptons are like this, no overlap. Low range on the IGH, 1,2 on the cogs. Medium range, 1,2 on the cogs. High range, 1,2 on the cogs. Zero overlap. And, the spacing between 1,2 on the cogs, is the same as the jump to the next range. So 6 equally spaced gears. I prefer no IGH, but darnit, they really did think out the gearing well. But they also have a special "Brompton Wide Range" IGH, not a standard Sturmey Archer 3.

Bill Kapaun

Don't care.