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Semi-compact rings

davidb67davidb67 Posts: 39
edited September 2015 in Road buying advice
Speccing a new bike - n+1 :-) - and for my usual rides, I do rely on my Madone's compact chains and 28t botton gear (10spd).
New bike will be 11spd, Ultra Di2 (as is my Madone albeit 10spd), and I'm tempted to try semi-compact, although worried I'll struggle up some of the hills on a 36-28 that I can just about haul up now on 34-28.
From what I understand, Shimano's cassette gearing jumps from 28 to 32 - no "30", but even if I put an SRAM cassette with 30t, I'd then need to spec a mid-cage rear derailleur.

Yes, MTFU I hear people shouting, but I'm no lardy, down to 70kgs now, but having suffered from knee pain previously (not bike-related, and happy with my position following good quality bike fit session last year), happier spinning up hills than trying to grind a larger gear.

If I go regular Ultegra "compact", is it possible & easy to change chainrings to 36/52 - not as permanent replacement but to try, or will that require I re-index gearing and possibly lengthen chain anyway?

Posts

  • oxomanoxoman Posts: 10,468
    No idea on the tech side, but listen to your body and make it a bit easier.
    Too many bikes according to Mrs O.
  • They are all (AFAIK) 110mm 4 arm spiders, irrespective of chainring tooth count, so yes it should be easy to change out chainrings. If you go from a 50 to a 52, you would need to reset derailleur height (52 tooth ring will be larger diameter), and as for vice versa, you'd probably be best to reset the height there too, though you might get away with not resetting it.
    On the inner, I'd say you could change freely between 34, 36 and 39 without having to reset anything, but I'm sure someone will be along shortly to correct me... :P
  • kirkeekirkee Posts: 369
    I am not able to give much advice regarding your Shimano 11 spd options-

    Im not exactly advocating the compacts or semi compacts on offer, this is what works for me. Regarding gearing I have recently gone to a custom semi compact 36 51. A few years back I went to 34 50 from 39 52 which i rode for ages. I ended up going back to the 39 52 as I didn't like the gearing relative to usage, 50t over use and 34t great on steep stuff but censored for anything else and cadence issues. For me the compact 34 50 was awful.

    I have got knee probs and Ive got tired of grinding up the local hills around here in Devon. The 36 51 compact paired with existing 13 29 cassette. The change was good straight off. On the hills I am spinning slightly more and the 51 feels more useable than the 52. I have lost a bit of top end but I don't miss it. The 36t ring will keep you spinning along slighter inclines or into headwinds etc where you may have otherwise changed up to the 50t when on a 34/50 and generally the chain line is less extreme.
    You may get away with chain length depending on how short your existing was cut.

    Check the gear charts and you may not lose much at the lower end with a semi compact 36 52?
    I dont race or TT but on the down side of the semi compact and alot of cassettes on offer Id guess alot of riders wont req a 52/11 top gear.
    Caveat - I buy and ride cheap, however, I reserve the right to advise on expensive kit that I have never actually used and possibly never will
  • jimwinjimwin Posts: 208
    "New wrote:

    If you're worried about struggling up hills on a 36-28, then don't do it. I live in West Devon which can be very hilly. On my Campag equiped carbon bike, I was using 50/34 chainrings with a 11~27 cassette. I had the same setup on my Ti bike and wanted to differentiate it from the carbon bike. So I changed the carbon bike to use 52/36 chainrings with a 11~29 cassette. The shortest gear was still similar, but the longer gears are now a few % longer. It works. The difference is small but noticable and this has the psychological effect as you feel you are going faster. And with the change of cassette from 11~27 to 11~29 means I can still get up the steepest inclines.

    One other aspect is that the Campag 52/36 chainrings are plain vanilla (no ramps for chainring changes). But frankly, I don't miss the chainring ramps of the 50/34 setup - chainring changing is arguably more positive using the plain vanilla 52/36 chainrings.

  • If I go regular Ultegra "compact", is it possible & easy to change chainrings to 36/52 - not as permanent replacement but to try, or will that require I re-index gearing and possibly lengthen chain anyway?

    I changed from 50/34 to 52/36 this year and just about got away with the same chain. When I change it I will add an extra link though. It's only the 52x28 combo that is a potential issue and I avoid that anyway.

    It takes me around 15 mins to swap back to 50/34 which I did recently for a Surrey hills ride. I didn't use the 28 but it was nice knowing it was there.

    Obviously the front mech needs adjusting every time you swap.
    "You really think you can burn off sugar with exercise?" downhill paul
  • Get the 50t outer chainset and buy a larger inner ring. You don't really need a 52 with an 11 at the back. No front derailleur adjustments, and the inner ring is cheaper to buy.

    I run a 36/50 front and a 38/50 on two of my bikes.
  • In March I went from a triple to a 11 spd semi compact and I love it. I've done a few steep climbs and never had an issue getting up them. I would say unless you are always riding steep hills a semi compact is fine. One benefit I did find was because of the closeness of the large and inner ring, you don't spin like mad when you drop down to the small ring. Perfect for most UK climbs.
  • Thanks for all the replies & comments everyone, very much appreciated.
    Never thought of the idea of getting the compact chainset and buying a larger small ring - 36. Sensible plan methinks.
  • philbar72philbar72 Posts: 2,228
    i've run a 52/34 on an ultegra based drivetrain (power 2max rotor and TA chainrings). no issues. you can get up most Uk hills on a 36 x28, its not that hard. i'm pretty poor up hills and i get by with 36 x 26 in Surrey and Kent.
  • neebneeb Posts: 4,445
    Get the 50t outer chainset and buy a larger inner ring. You don't really need a 52 with an 11 at the back. No front derailleur adjustments, and the inner ring is cheaper to buy.

    I run a 36/50 front and a 38/50 on two of my bikes.
    I agree. I've been running 36/50 exclusively for years (with an 11t sprocket at the back), and I can't see why anyone who doesn't need a 34-28 gear would want anything else. With an 11t sprocket the highest gear is the same as a 52 or 53T ring paired with a 12t sprocket, and unlike a 36/52 or a 34/50 the gap between the two rings is no more than with a 39/53, so you don't get that uncomfortable jump.

    36/50 + 11-25 is basically exactly the same in use as a 39/53 + 12-27. You just have a little more room to play with if you do need to change the sprockets at the back to get a lower climbing gear, and as a bonus the whole setup is a little lighter as both the sprockets and rings are smaller. Unless you really need a 52-11 gear (which is massive - are you a professional sprinter?) you don't need anything bigger than a 50t front ring.
  • paulmonpaulmon Posts: 315
    One thing worth noting is that it can be cheaper to buy an new chainset than new rings especially if its Shimano.

    I run a 52/36 on my Ti/Winter bike and a compact on my other bike. I much prefer the 52/36 for the riding I do in the colder/wetter months but prefer the compact for climbing. I have a 11-28 on both bikes and 11-32 for stuff like the Fred Whitton.

    If you plan to use both than make sure you fit the chain for the bigger rings otherwise you run the risk of ripping your mech off.

    P
  • GrillGrill Posts: 5,610
    Yes changing chainring size is easy. What's even easier is to just go with the 11-32 cassette with the GS mech. You're going from 10spd to 11spd so you won't notice a jump.
    English Cycles V3 | Cervelo P5 | Cervelo T4 | Trek Domane Koppenberg
  • Thanks for all the advice and suggestions, reckon I'll try putting a 36 inner ring on at some point once I get the new bike, see how it goes.
    I'm no sprinter, so my weedy little legs are not going to spin-up a 52 on an 11 rear anytime soon, 50/34 with a swappable 36 inner is what I'll do.
    Cheers,
    David
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