# Switching Chain Ring Sizes



## bikerdoug (Mar 27, 2005)

I have a dura ace set up on my Cervelo Soloist. Can I simply switch the chain rings from a regular 53/39 setup to a compact setup with a 50/34? I know that I would have to adjust the front and rear derailleurs and have a different length chain. But, can I just bolt on new chain ring sizes, or do I have to buy a new compact crank to get the desired sizing? My goal is to be able to use both the regular and compact setups and switch between them for races requiring different gearing.


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## Keeping up with Junior (Feb 27, 2003)

*Cassette*



bikerdoug said:


> ...My goal is to be able to use both the regular and compact setups and switch between them for races requiring different gearing.


It is a lot quicker to simply switch cassettes to match the terrain you are racing.

What cassette are you running now?


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## Dave Hickey (Jan 27, 2002)

You need a compact crank...A 34T ring is too small for your crankarms.. 

Your DA cranks have a 130 bolt circle diameter.. Compact cranks have a 110 bolt circle diameter


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## Stogaguy (Feb 11, 2006)

*New Crank Needed*

A standard road double has 130mm bolt circle diameter (BCD), a compact 110mm. Chainrings are not interchangable between the two. At the very minimum, you will have to buy a compact crank with chainrings that is compatible with your existing bottom bracket. Then you could change out the crank as needed to change your gearing.

IMHO, this sounds like a big hassle. Personally, I would switch to the compact crank and change cassettes and inner chainrings as needed for different races. There will be others that disagree with this approach. The whole compact versus standard crank issue has been debated to death in this forum.


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## bikerdoug (Mar 27, 2005)

I'm already using an 11/28 cassette and wouldn't want to add larger cog because of the larger jumps that would be needed. I also want to keep the 11 cog for going down some of the big hills ...


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## bikerdoug (Mar 27, 2005)

Thanks Dave. I thought it would be too easy to simply switch the rings and save the money that I'll have to spend the money on an additional crank.


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## bikerdoug (Mar 27, 2005)

Thanks Stogaguy! I'm using a Sram 11/28 with my 53/39 and also have a DA 12/25 available. I think I do need to go with the compact crank and experiment on different terrain using the two cassettes. Do you have any other thoughts on what I should try? What would you suggest as far as another alternative to try for the inner chain ring size vs the standard 34?


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## gnatman (Jan 14, 2009)

bikerdoug - I looked into this once before and found a 46T inner ring with 130mm BCT at a bike. They had to look through catalogs to find it. It was intended for cyclocross use, but if you want to use it for road racing, such a ring might be suitable.

In the end, I installed a compact (50/34) crank and suit up the cassette to suit my needs.


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## Opus51569 (Jul 21, 2009)

I had a similar question as the O.P., so this has been very informative and helpful. So, if I'm understanding everyone correctly, compact and standard double rings are not interchangeable because of the differing diameters 110 vs. 130. 

In my case, I have a Shimano 105 compact 50/34 with an 11-25 rear cassette and find that the gears that feel the most comfortable in are the ones that seem to put me in a position of cross-chaining. I had thought about swapping the 34 with a 36 or even a 39 if I could find one that worked. After reading posts here, I am guessing a cassette change would be the better option.

So, are cassettes interchangeable as long as the number of gears are consistent (10)? Are there any other modifications (FD, RD, chain) that are required?


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## ARP (Mar 7, 2002)

*The 34 ring is the problem*



Opus51569 said:


> I had a similar question as the O.P., so this has been very informative and helpful. So, if I'm understanding everyone correctly, compact and standard double rings are not interchangeable because of the differing diameters 110 vs. 130.
> 
> In my case, I have a Shimano 105 compact 50/34 with an 11-25 rear cassette and find that the gears that feel the most comfortable in are the ones that seem to put me in a position of cross-chaining. I had thought about swapping the 34 with a 36 or even a 39 if I could find one that worked. After reading posts here, I am guessing a cassette change would be the better option.
> 
> So, are cassettes interchangeable as long as the number of gears are consistent (10)? Are there any other modifications (FD, RD, chain) that are required?


A 36t solved my problem. you are probably too strong of a rider AND your choice of riding terrain is such that your preferred gears are right in that so called cross chain zone, a 36 or 38 will fix ya right up


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## Stogaguy (Feb 11, 2006)

*Key off lowest gear needed*

When choosing gearing for a specific race, it is best to scout/ride the course ahead of time. Use this reconnaissance to determine the lowest gear needed to effectively ride the course. This then helps determine your required setup. Make sure you have a low enough gear for any conceivable racing contingency. Getting dropped on a climb because you are over geared just plain sucks. It is better to have one cog lower that you never use, than to be wishing that you had a gear that was just a touch easier to turnover.

With the above in mind, a 11-23 or 11-25 will cover most racing situations when paired with a 34/50 compact. Many would question the need for the 11 (another hotly debated topic). If the 34 is too low, change it out for a 36 or 38. 

One thing to keep in mind is that modern outer chainrings are designed with shift ramps. These ramps work best when paired with the specific size inner chainring they were designed for. As a result, for best front shifting performance, you need to swap chainrings out as a set. Stated differently, if you had size 34, 36 and 38 inner chainrings, you would have a "matching" 50T outer chainring for each of the inners. No big deal, just more stuff to buy.


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## Opus51569 (Jul 21, 2009)

So, in my case a chainring swap would be a better option than switching out the cassette? Are there chain length issues or adjustments to the derailleurs required for the switch or is it a plug-and-play swap?

I wouldn't call myself a strong rider, but definitely more of a wannabe masher than a spinner. The gears that feel the most comfortable for pacing seems to be the 34 in the lower third of the cassette or the 50 in the upper third of the cassette, hence the cross-chaining.


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## bikerdoug (Mar 27, 2005)

Good advice. Last weekend I did the New York State Championships and truly suffered. During the two laps of the 20 mile course there were two climbs at 19% and eight at 15% (too many 10% rollers(?) to count) and most of these were in the initial 10 mile section of each lap. Total climbing was about 3,500 feet. I had a 53/39 with an 11/28 cassette which works great when I'm in Arizona for half the year, but back here in the East, which I live in the other half, I've been really suffering in the races with significant multiple climbs. I'm 62 years old and just don't find the regular crank is enough and is causing me to almost get off the bike on some of these big climbs!


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## Opus51569 (Jul 21, 2009)

bikerdoug - sorry about stepping on your thread. I thought my problem was similar enough, but it sounds like we have different gearing issues. I'll start a different thread.


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## bikerdoug (Mar 27, 2005)

No problem ... we all need help and this is a great place to get it!


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## khaizlip (Aug 21, 2008)

bikerdoug said:


> Good advice. Last weekend I did the New York State Championships and truly suffered. During the two laps of the 20 mile course there were two climbs at 19% and eight at 15% (too many 10% rollers(?) to count) and most of these were in the initial 10 mile section of each lap. Total climbing was about 3,500 feet. I had a 53/39 with an 11/28 cassette which works great when I'm in Arizona for half the year, but back here in the East, which I live in the other half, I've been really suffering in the races with significant multiple climbs. I'm 62 years old and just don't find the regular crank is enough and is causing me to almost get off the bike on some of these big climbs!


I was at that same race - I did see one guy off of the bike for the second really bad climb (Whitbeck) on the second lap. 
That was the first time since April that I've used the lowest ring on my triple, and thank god I had it!

The last 10 miles of that course were great though.


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## bikerdoug (Mar 27, 2005)

I saw several people off their bike for that climb on the second lap. I was thinking to myself that I was going so slow at one point (about 5mph) that I should get off ... but my pride stopped me (how can you be proud when your going 5mph!). Wish I had a triple for that one!!


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## Gimme Shoulder (Feb 10, 2004)

If your talking about DA 7800 series, I believe Shimano DID come out with a compact chainring set for the 130 bcd crank.

Here's the outer 50T ring
http://www.excelsports.com/new.asp?...00+Outer+50T&vendorCode=SHIM&major=1&minor=12

Couldn't find the inner ring though.


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## Salsa_Lover (Jul 6, 2008)

DA 7800 has only standard version

minimum inner ring is a 38, only 39,42 and 44 are avaliable on DA, the Truvativ, FSA or Ritchey 38 rings 130bcd work well with the DA.

Outer ring DA is 56/55/54 for TTs and you have 46/47 for cross and 50/52/53 for road.


I tried 52/38 shortly but saw no benefit and went back to the 53/39

Compacts are only good if you climb a lot or go often on long or steep hills, otherwise the gears are "off" and you'll have your chained crossed more often than not.


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