C200

I have a Cannondale Synapse and would like to install a smaller chainring in place of the 30 tooth ring. Is it possible to install a 24 tooth chainring in place of the 30 tooth ring? If not what is the smallest ring that will work with that set up? I have 52-42-30 chainrings on the bike at this time. My concern is how well the bike will shift with the smaller chainring.

HillRider

I've installed 26T granny rings to replace the stock 30T on a bunch of Shimano cranks including 7, 8 and 9-speed 105 and Ultegra. They all work fine. You lose the ability to use the granny with the two or three smallest cogs but that's no sacrifice.

I've never tried a 24T so I can't comment from experience but I know a 26T works.

C200

I also live where there are a lot of hills. I like hills and that is the main reason that I want to go to a smaller chainring. The small cog loss is no big loss. If the 26 works than I have a feeling that a 24T would work also. I am anxious to see if anyone else on this thread has actually used a 24T ring. Thank you for your input. It has shed some light on what I can do to lower those gears. I was under the impression that a smaller chain ring would not work.

Michel Gagnon

The 24 works with your derailleur. If you use STI, from what I heard, it will work, but you should install a gizmo like the n-gear to prevent the chain from falling onto the bottom bracket. Maybe it's not necessary.

My tandem has had 48-38-24 with bar-end shifters. It worked fine.

gm1230126

Shimano triple road front derailleur specs say a maximum capacity of 15T which in your case would mean 27T small ring for optimal shifting. If you go smaller it may work but hesitate when shifting into the middle.

Thor29

I ran a 52/39/24 for awhile with an Ultegra front derailleur. Worked fine most of the time but every once in awhile it would drop off to the inside (maybe 1 out of 10 downshifts). Eventually I swapped the 52 for a 48 and now the shifting is perfect.

HillRider

Fitting a Third Eye Chain Watcher or equivalent is a good idea even with the standard 30T granny but even better if you go smaller.

Michel Gagnon

I haven't looked on Shimano's website for their word, but I think that "15-teeth" is the maximum difference between large and middle rings. As far as I remember, they recommend 10 to 12 teeth differencial.

I know for a fact that the cage of both the Ultegra and 105 front derailleurs work fine with 44-34-22 and with 48-38-24 – without chain catcher in my case, but I'm also working with bar-end shifters, not STI. The derailleur cage is even long enough to work with a 48-38-28-18 quad... but then, you need friction shifting to shift through those four rings.

HillRider

Wow, where do you get a bottom bracket long enough to clear four rings?

cyccommute 

I used to have a Quad adapter on a mountain bike. You didn't need a longer bottom bracket, you just needed a derailer that would travel inward far enough. The 3rd and 4th rings were mounted on an adapter that just shoved the 4th ring inboard. Worked okay.

cyccommute 

I ran a 24tooth wheel on a 48/38 crank that came stock on my T800. It works but the occasional problem I had was that the chain would jam between the middle and inner ring. A crank with a 135mm bcd has a lot of open space between the inner and middle ring. This combination works much better on a 110 bcd crank.

C200

I was going to have the lbs, from where I purchased this bike, install a 48-38-24 set of chain rings. They told me the bike wouldn't shift right with that setup. I than decided to go with the 52-42-30 rings and 170mm cranks. Until I saw a thread where someone was running a set of chainrings with a small 24T ring, I didn't realize that a smaller chain ring could be used. The Synapse is Cannondales newest road bike with the standard road bike shifters

2manybikes

What crank do you have on that bike? A DA 9 speed triple won't work, for example. The BCD is wrong on the granny gear. Yet the Ultegra and the 105 will work.

Al.canoe

I had to go to a TA (French) crankset to be able to run 22/36/46 on my ti cyclocross frame which I use it only as a road bike. It has three bolt circles so I can use about any ring that I want. I use a 12 to 27 Ultegra cassette. My front derailleur is ultegra, rear is XT long cage. Shifters are ultegra STI.

In theory, the shifting is not supposed to be as slick as the matched Shimano rings. I haven't noticed.

You can also go to a mountain bike crank. That's what my wife uses on her road bike. I think you can go as large as 48 on the larger (non compact) ATB cranks, possibly more.

Al

C200

I have a Tiagra triple with a 105 derailleur. I have a 9 speed cog set on the rear

2manybikes

As far as I know the BCD will allow you to go down to a smaller granny gear. The problem with DA is they bolt the granny to the middle ring and use an odd size BCD.

Michel Gagnon

No change to the bottom bracket.

My experience is related on this webpage, along with the reasons motivating this installation.

I eventually did one minor tweak: I added a 1-mm spacer to the right of the bottom bracket, so the bottom bracket is shifted to the right by 1 mm. Improvements:
– shifting onto the 18 was OK in good weather, but iffy in snow; now works ok at all weather;
– the second ring used to work only with 4 or 5 cogs; it now works great with 5 and just OK with 6.

Note that if I were riding the tandem only with an adult, I would probably never have done such a modification. But loaded touring with two children has its challenges!

Regards,

cyccommute 

I switched my T800 to a 44/34/20 without problems using the standard Tiagra shifters and front derailer. A 48/38/24 shifts just fine. I have used a 52/40/24 on other touring bikes but that was with friction shifters.

Retro Grouch 

There are lots of things that I'd do on my own bike that I'd hesitate to do for a customer.

C200

On my Raleigh C200 I have a set of 42-32-20 chainrings, however, the shifters are twist grip shifters. I have never had a problem with shifting. There are at times that I have to make small adjustments but nothing major. When I got my new Cannondale I also wanted to go with the lower gearing and ran into the lbs problem. The Synapse is not a cheap bike and I don't want to do anything that will ruin the drive train. But after reading everything that has been posted on this thread I am beginning to believe that going to a lower set of chainrings is possible. This is a good thing.

HillRider

Truer words were never typed. Actually they apply to any form of transportation, not just bicycles.

Michel Gagnon

This is a major issue of mine. Why is it that most bike shops are afraid to do something like that when it has been demonstrated countless times that it works? Even with the limitations imposed by STI – indexed front –, there are quite a few tourers who ride such a crankset successfully. There are even some who ride 52-42-26 or 24 without problems. Shifting "less efficiently" in this case usually means a 1 or 2 second extra delay when shifting in or out of the granny, but what the heck? A tourer or a commuter is not a racer! It still is a better shift than with a top notch derailleur of the 1970s!

Basically, as long as the customer understands the limitations of such a "non-standard" setup, why not! There are so many advantages in having a drivetrain properly designed for the legs of the customer rather than for the legs of an athlete doing peloton riding. Including the advantage of keeping the customer cycling because he/she doesn't find hills a painful experience.

After all, when we are customizing a drivetrain, we are NOT talking about a safety compromise. It's not like selling a bike without proper brakes or with sub-standard wheels. If I were pushing it a little bit, I would suggest that it's much more dangerous to sell a bike without fenders or lights, because a rider could be blinded by water thrown off his/her wheel, etc.

C200

I don't know if this makes a difference or not, but I am running a 9 speed 34T cog set on the rear. The lbs installed the cogs and at first told me that a smaller set of chain rings would work. When I told them that is what I was looking for they told me that the smaller chain rings wouldn't work. Go figure

kahn

Oh, boy can I relate. I'm nearing 60 but my knees have been nearing 80 for years. PUSHING gears is for me, harder than hiking up steep hills. I don't believe training my thighs will work so while I can hike up 4,000 feet in 4 miles it is not like trying to pedal up steep hills. I can feel the joints grating and I NEED LOW GEARS.

SOMEHOW when I had a new custom road bike built after a top tube break, they managed to move my xt rear and xt crank from the last ROAD bike to the new but also put on sti 105's (the older bike had bar-end friction). When I was purchasing my Madone I wanted to replace the small inner with a 26T and also needed a higher stem so I brought my current bike in to show. We started talking about the gearing and the repair manager with lots of experience looked at my custom setup and said: "That canNOT work!" I politely informed him it DID WORK. He said sti-105 index could not work with the 26-42-52 triple. I offered to allow him to ride the bike since I had been using it for 4 or 5 years and it did WORK.

Now I don't know the mechanics of this stuff but it worked OUT OF SPECS and it worked FINE.

Now the triple on the Madone with the replaced 26t inner is reguarly dropping the chain to the inside. It may need more tweaking (still newish - 2 months).

My problem is that the diameter of the seat tube and the joint between the seat and down tubes makes using those chain guard things nearly impossible. And it appears that the chainstay might interfere with the device from AJ (for mt bikes) or the bottom bracket might not allow its installation. N-gear has the same problem as the fang-like guard - diameter of the seat tube.

I did dremel a fang-guard and used zip ties and it generally works but is not quite rigid enough or placed right (using poorly fitting jerry-rigged zip ties) to keep the chain UP and occasionally the chain has dropped below it making it hard to retrieve the chain.

I was hoping to actually add (yes, I don't care about weight of bike as opposed to being able to just ride in comfort long distances and high hills) a FOURTH, larger chainring to the inside (I now read there are really such things) which would really serve merely as a chainguard but again, the chainstay probably does not afford the necessary spacing. I actually had this fourth machined for me and spacers provided by a shop down in Austin but I don't think it will work. The shop also provided longer bolts so that it would bolt both the normal inner triple and this improvised 4th in the same bolt holes.

My problem like many here, is that we don't work on our bikes ourselves and rely on the bike shops to help and also to accommodate. Also, I'm still under warranty and want to deal with the lbs.

I apologize for the length and possibly confusing narrative.

I know, I should have gone custom (too much money this time) since light and fast means "who needs a triple" but some of us do and some of us need a very low triple.

Michel Gagnon

Kahn, there are three solutions to solve your problem.

– On quite a few bikes with odd chainrings, I have had a lot of success by installing the derailleur at a slight angle. I install it "crooked" with the bottom part sticking out by 1-2 mm. It works fine with friction shifting (48-38-24, 44-34-22, 50-45-30..., 46-24), but I have never used the trick on a bike with STI.
– The [ur=https://n-gear.com/whatis.html]N-Gear Jump Stop[/url] is a gizmo that does exactly what you want. You set the plate close enough to the small ring so that the chain stays within 1 mm of the plate. There is another gizmo similar to it, which is less efficient, but works on ovalized seattubes.
– I have done a "poor man's job" when I installed a quadruple on my tandem. Basically, after looking in my parts bin, I found an old bracket for a rear light that worked in a similar fashion. You may find a picture here (towards the bottom of the page).