Compact to semicompact conversion

nicolazilio

Hi everyone,

I ride a bike fitted with a 10-speed Ultegra 6700 groupset and a traditional compact chainset/cassette combination, 50-34 + 11-28. I would like to try out a semi-compact setup to see how it compares to the one I use now. Let's say that I am an enthusiastic amateur rider , who prefers climbs over descends or flats. What, allowed, combinations would you recommend as a "balanced" semi-compact? 52-34 + 11-25 or 11-28?

Thanks for the help.

ugo.santalucia

18 teeth drop between chainrings is a terrible idea, don't go there...

markhewitt1978

52/34 wouldn't work I believe as it's outside the range that the front mech can handle.

In any case the semi-compact is usually 52/36 is it not? You should be able to just straight swap it for your current chainset if you want to do that, save for repositioning the front mech and chain length.

If it's right for you; who can say, we already have a thread about semi-compacts which spans 12,000 pages. Only thing to say is that semi-compacts aren't really aimed at riders who prioritise climbing over all else, but again only you can know what ratios you need and you can easily simulate them with your current setup - save for the highest gears of course.

Mad_Malx

I don't understand what you think you are gaining.
If you prefer climbing to flats or descents, why do you need higher gears? Do you often (ever?) spin out at 50x11?
We're all different, but with similar terrain preferences to you I prefer a 50-34 with a 10 speed 12-27 cassette because I wouldn't use the 11 (and don't use the 12 very much) and so have better spaces.

part time waster

You can just buy a 36 inner and choose your cassette to suit , maybe 12-25 .
I ride a 36-50 , and 13-26 in 10 speed or 12-25 in 11 speed campag. I almost spin out on the chaingang at 50-12.
Getting on for over 32mph in the build up for the sprint/world champs effort for the road sign.

fenix

Yeah this makes no sense.

You like the climbs the most but you want harder gears ? Why ?

buckmulligan

I have to agree with everyone else, it doesn't seem to suit your stated goals and the options you propose are all pretty bad ideas. If you want a semi-compact because they're new and seemingly fashionable then go for it, but you'll probably end up having to "convince yourself" that it's an upgrade.

You can achieve a similar change in gear ratios with a new cassette (Ultegra 6700 goes down to 11-23), which would be less than half of the price and less than half of the hassle to install.

nicolazilio

Thanks for those that tried to answer my actual question, which was related to finding out what chainrings and cassette combinations I could use/are mechanically allowed (and maybe why one combination is allowed while one is not) and not why would/should/could want to change from a compact to a semi-compact.

As for the other issues that have been raised, I am aware of the advantages and disadvantages of compact vs. semi-compact: I have gone through the various other posts on this topic already. But, as I am a molecular biologist, I like to do my own experiments, no matter what. I just want to find out how I respond to one setup vs. the other. Call it professional bias .

markhewitt1978

nicolazilio wrote:

Thanks for those that tried to answer my actual question, which was related to finding out what chainrings and cassette combinations I could use/are mechanically allowed (and maybe why one combination is allowed while one is not) and not why would/should/could want to change from a compact to a semi-compact.

As for the other issues that have been raised, I am aware of the advantages and disadvantages of compact vs. semi-compact: I have gone through the various other posts on this topic already. But, as I am a molecular biologist, I like to do my own experiments, no matter what. I just want to find out how I respond to one setup vs. the other. Call it professional bias .

If you didn't want those opinions then you shouldn't have invited them by stating what sort of riding you preferred.

slowmart

I've just gone from a compact to a semi and found no noticeable difference

mrb123

nicolazilio wrote:

Thanks for those that tried to answer my actual question, which was related to finding out what chainrings and cassette combinations I could use/are mechanically allowed (and maybe why one combination is allowed while one is not) and not why would/should/could want to change from a compact to a semi-compact.

As for the other issues that have been raised, I am aware of the advantages and disadvantages of compact vs. semi-compact: I have gone through the various other posts on this topic already. But, as I am a molecular biologist, I like to do my own experiments, no matter what. I just want to find out how I respond to one setup vs. the other. Call it professional bias .

Out of interest, what cadence do you normally ride at?

fenix

So to summarise

You can't use a 52-34 as theres too big a range for the front mech to cope with. That would have given you the same low gears as you currently have - but with more at the top end for coming down hills at speed - which you don't class as your interest.

You could change your block from 11-28 to 11-25 which means you won't have as low a gear for climbing - but you will have more choice mid block.

In my experience I'm never really asking for a higher gear as my lowest. Whatever my lowest sprocket is - it WILL be used.


What you've asked about seems opposite to what you intend to do on the bike.

buckmulligan

We're just trying to look out for your best interests!

You got the information that you wanted, a 6700 front derailleur can only handle a maximum difference of 16T between front rings, so whatever you increase the big ring by, you'll have to increase the small ring by too, e.g. the normal semi-compact setup of 52-36. Cassette-wise you have a lot of options with the 6700 series, I'd check your rear derailleur if you have the newer 6701 model then you're good to go up to a 30T on the rear. However, if you're just going to stick an 11-25T on the back then you're going to be in pretty much exactly the same position as you have with your current compact with 11-28T; you'll basically lose your current easiest gear and thus have to grind a bit more going uphill but you'll be afforded a slightly lower cadence going max speed downhill.

The 6700 cassette setups are all listed in the link below, seeing as you're a scientist (me too!) I'd do some maths and try to work out how you're actually going to benefit from this because it's really not looking like a good idea. You're going to have to drop a whole load of cash on new chainrings, a new chain and a new cassette and and give yourself the hassle of repositioning the front derailleur (likely requiring a new FD cable) for very little benefit. As everyone says, unless you're spinning out your 50-11 going downhill and NEED to be able to push faster (e.g. to keep up with a group) then the drawbacks (i.e. having to grind a bigger gear up hills) are totally not worth it.

http://si.shimano.com/php/download.php? ... 00-ENG.pdf

ravey1981

If you currently use the 34-28 combination a lot then a semi compact is no good for you as it will be too high geared. If you don't use the 28 much then you could put on a 36 chainring (this will be almost the same as 34-25, so try that gear out now and see if it is low enough for you) I would keep the 50 as with a 36 is gives less difference between big and small rings making transitioning from one to the other easier in terms of not having to drop 2-3 gears at the back to get the next gear. Realistically if you've got an 11 tooth cog on the back you don't need higher than a 50. Most people can't actually use that gear.

dennisn

ravey1981 wrote:

If you currently use the 34-28 combination a lot then a semi compact is no good for you as it will be too high geared. If you don't use the 28 much then you could put on a 36 chainring (this will be almost the same as 34-25, so try that gear out now and see if it is low enough for you) I would keep the 50 as with a 36 is gives less difference between big and small rings making transitioning from one to the other easier in terms of not having to drop 2-3 gears at the back to get the next gear. Realistically if you've got an 11 tooth cog on the back you don't need higher than a 50. Most people can't actually use that gear.

As above. What possible use would you have for a 52-11? Even with a 50-11 that 11 tooth cog will only sit out there and mock you. One good thing though, you'll never wear it out.

charlie_potatoes

dennisn wrote:

What possible use would you have for a 52-11? Even with a 50-11 that 11 tooth cog will only sit out there and mock you. One good thing though, you'll never wear it out.

I use 52-11 on most rides and I'm no power house. It is often desirable from a training perspective to keep pedalling rather than tuck on the down hill. Even if I didn't I would not allow a cog to mock me and would certainly seek help if I felt that it was.

I agree that, in the OP's case, a compact is probably the way to go but, as usual with these type of posts, it is in danger of being turned into a 'no one needs an 11 tooth' thread.

It has got me thinking that maybe Dennis isn't the only one on here that feels inadequate?

napoleond

I like to ride with a semi on.

Alex99

nicolazilio wrote:

Thanks for those that tried to answer my actual question, which was related to finding out what chainrings and cassette combinations I could use/are mechanically allowed (and maybe why one combination is allowed while one is not) and not why would/should/could want to change from a compact to a semi-compact.

As for the other issues that have been raised, I am aware of the advantages and disadvantages of compact vs. semi-compact: I have gone through the various other posts on this topic already. But, as I am a molecular biologist, I like to do my own experiments, no matter what. I just want to find out how I respond to one setup vs. the other. Call it professional bias .

Even with the smiley, that seems a bit arsey. Do you begin each experiment by proving whether DNA is the carrier of hereditary information, or determining whether the cell exists?

noodleman

Slowmart wrote:

I've just gone from a compact to a semi and found no noticeable difference

Not many 20% + hills round your neck of the woods then? :?

markhewitt1978

Charlie Potatoes wrote:

I agree that, in the OP's case, a compact is probably the way to go but, as usual with these type of posts, it is in danger of being turned into a 'no one needs an 11 tooth' thread.

Well it makes a change from the past where the attitude was always that nobody needs smaller than 39/25 and if you do you need to HTFU or GTFO.

charlie_potatoes

markhewitt1978 wrote:

Charlie Potatoes wrote:

I agree that, in the OP's case, a compact is probably the way to go but, as usual with these type of posts, it is in danger of being turned into a 'no one needs an 11 tooth' thread.

Well it makes a change from the past where the attitude was always that nobody needs smaller than 39/25 and if you do you need to HTFU or GTFO.

It's not really a change as such though. Just the other side of a bad penny.

dennisn

Back in the 70's I recall using a 52-42 with a 13-26 in the back for everything. Then again I was whole lot younger. Still, I think a 50-11 is not a useful gear and that people who claim they use it "all the time" are liars.

charlie_potatoes

dennisn wrote:

Back in the 70's I recall using a 52-42 with a 13-26 in the back for everything. Then again I was whole lot younger. Still, I think a 50-11 is not a useful gear and that people who claim they use it "all the time" are liars.

Lucky no one on this thread has made such a claim then Dennis. knowing how you dislike causing offence.

dennisn

Charlie Potatoes wrote:

dennisn wrote:

Back in the 70's I recall using a 52-42 with a 13-26 in the back for everything. Then again I was whole lot younger. Still, I think a 50-11 is not a useful gear and that people who claim they use it "all the time" are liars.

Lucky no one on this thread has made such a claim then Dennis. knowing how you dislike causing offence.

Sorry, couldn't come up with a better word than liars.

markhewitt1978

I think if anyone uses 50/11 a lot it's likely to be mostly on descents where they just go into whatever is the hardest gear regardless, rather than actively using it a lot. Indeed if you do spend a lot of time in 50/11 then perhaps a semi-compact would be better for you!

dstev55

I wouldn't say I use 52/11 a lot but I know I can get down descents faster than what I can on my other bike that has 50/12.

I'm a cadence over power ride but even I can spin out 52/11 on any descent of 5%+ so I think to keep suggesting that 50/11, 52/12 or 53/11 is pointless, like I keep often seeing on this forum, is a bit misleading to be honest.