Zarch
Peloton Rider
Posts: 50
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Post by Zarch on Sept 7, 2016 15:18:28 GMT
I live in a hilly area and find the 50/34 with 12/28 combo on my recently purchased 540 a little tough on climbs.
(Note, I bought this in the sale the other month, so its the 2015/2016 model. Not the recently revamped spec version.)
Doing anything with the front chainset would be way too much money to spend on a brand new bike, so I'm wondering if I could straight replace the existing Tiagra 12-28 cassette with the 11-32 model? Will the 105 rear mech handle it? Or will I fall foul of any other limits?
The 11-32 cassette is only Β£19 new, so an easy way to get me some help up the hills? I really don't care about losing top speed.
The other option is the Ultegra 12-30, but its double the price for less of an advantage.
Any help would be appreciated.
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Post by Rocket on Sept 7, 2016 15:57:00 GMT
Don't treat hills as your enemy. Treat them as your friend. Seek them out and train on them. Pretty soon that steep hill won't be so steep.
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Post by erictherat on Sept 7, 2016 16:15:45 GMT
The only issue is the rear mech. If it is a long cage version, then no worries. Otherwise it is a maybe. if the mech cant reach the 32 ring, then a new long cage rear mech aint a lot of money. otherwise - go for some training rides with Rocket
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Post by william39 on Sept 7, 2016 16:54:18 GMT
Should be fine but you will need to pay attention with chain length. B screw can be adjusted if necessary. I used an 11-32 cassette with 50-34 chainset on 105 5800 with a short cage mech with no problems. I see way too many people struggling away grinding up hills with unsuitable gearing as I go spinning past. On the climb I did today I would have been happier with an even bigger rear cassette.
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Post by mark072 on Sept 7, 2016 17:54:33 GMT
105 long cage can handle a 32 the Tiagra short cage rear mech is a max of 30 teeth. The 34/32 combo gives you the same inches in gearing as my T3a triple with 30 front and 28 rear (lowest gear). I do 1 in 4 gradient climbs (Winnats Pass etc) but nothing wrong with wanting lower gearing if like to spin and will be easier on your legs. Have gone past blokes on a lot more expensive bikes on steep climbs like winnats using 30/28.
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Deleted
Deleted Member
Posts: 0
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Post by Deleted on Sept 7, 2016 18:07:45 GMT
I use medium cage with same set up as William. Don't know if there may be chain length issues? Today I know fairly well what works for me when it comes to climbing, all the help I can get, no shame in that.
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Zarch
Peloton Rider
Posts: 50
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Post by Zarch on Sept 7, 2016 19:44:42 GMT
Thanks for the replies. Mark, I live on the outskirts of Sheffield, so you'll appreciate the hills i'm playing in. Although Winnats might be out of my league for now. Rocket, I agree I need to work at it, but I enjoy the triple gearing I have on my mountain bike. I'm happy to spin up those hills, hence i'd like to move to 11-32. Everyone else, thanks...... technically sounds like it should be ok? But how do I know whether the 540 has the short or medium cage? All I can see on the derailleur itself is RD-5701 but no indication of the length of the cage. I can't find anything on the Shimano spec site to indicate. I thought maybe the colour of the cage might indicate? Does this picture help at all? Thanks again.
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Post by william39 on Sept 7, 2016 20:45:44 GMT
It is the short, Shimano says 30 max but 32 will be fine from my experience.
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Post by jondxxx on Sept 8, 2016 6:22:55 GMT
I have the 11-32 Tiagra cassette on my 540 with no problems. Didn't even have to lengthen the stock chain. Fairly sure that the mech. is a medium.
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Post by utriban on Sept 8, 2016 9:25:52 GMT
If you put 32-11 on what you have right now, you should not notice the difference when it comes to short/medium cage.
Two things might happen: - you might need to adjust B-screw to allow for the distance between jockey wheel and the new biggest ring - you might not be able to use front big/rear big combination - which you would not use anyhow, unless in error
length of the cage plays a role in picking up the chain slack on smaller rings when chain is long enough to serve front big/rear big. If you plan on keeping a current chain length, your RD is already dealing with it just fine. drop in small ring from 12 to 11 is negligible for this.
You did make a wrong assumption though, 11-32 will give you more top speed than 12-28 you currently have. What you are going to loose is a refinement in shifting - you won't be able to fine tune your cadence due to bigger jumps between rear chain rings.
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Zarch
Peloton Rider
Posts: 50
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Post by Zarch on Sept 8, 2016 10:56:12 GMT
If you put 32-11 on what you have right now, you should not notice the difference when it comes to short/medium cage. Two things might happen: - you might need to adjust B-screw to allow for the distance between jockey wheel and the new biggest ring - you might not be able to use front big/rear big combination - which you would not use anyhow, unless in error length of the cage plays a role in picking up the chain slack on smaller rings when chain is long enough to serve front big/rear big. If you plan on keeping a current chain length, your RD is already dealing with it just fine. drop in small ring from 12 to 11 is negligible for this. You did make a wrong assumption though, 11-32 will give you more top speed than 12-28 you currently have. What you are going to loose is a refinement in shifting - you won't be able to fine tune your cadence due to bigger jumps between rear chain rings. Thank you for all that....... better hill climbing and faster top speed..... its all win/win then.
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Post by r0b1et on Sept 8, 2016 11:06:32 GMT
Thank you for all that....... better hill climbing and faster top speed..... its all win/win then. Well no, lack of cadence control means you become significantly less efficient.
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Post by william39 on Sept 8, 2016 11:23:13 GMT
Thank you for all that....... better hill climbing and faster top speed..... its all win/win then. Well no, lack of cadence control means you become significantly less efficient. The benefit of having a 32 tooth sprocket enabling you to keep up cadence on climbs will more than make up for a few gaps at the other end for the vast majority of cyclists in my opinion.
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Post by r0b1et on Sept 8, 2016 11:25:05 GMT
Well no, lack of cadence control means you become significantly less efficient. The benefit of having a 32 tooth sprocket enabling you to keep up cadence on climbs will more than make up for a few gaps at the other end for the vast majority of cyclists in my opinion. Indeed, especially if its an issue, but its not all wins getting a wider cassette, there are some more than marginal losses. It certainly isn't "win/win" as I quoted, perhaps win/win/lose.
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Post by chas on Sept 8, 2016 11:56:10 GMT
I think a lot of (particularly older, wiser?) cyclists would like the option of a 13/32 cassette to give a win/win situation where pedalling over 30mph isn't required. I'll stick with a triple for the time being I think
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