Viewing 25 posts - 1 through 25 (of 25 total)
  • Compact Chainsets – Road Bikes Also…BB30 Conversions
  • slowjo
    Free Member

    What is the rationale behind compact setups? Winter and CX bikes aside, I have never had a big ring smaller than 52. To my mind, a 50 is going to be terribly twiddly.

    If I wanted to use a 105 chainset on a BB30, any recommendations for a decent conversion kit?

    njee20
    Free Member

    Your mind is wrong, 50-11 is a taller gear than a 53-12, and how often do you spin that out?

    The 16t jump is a pain IMO, and a 34t is quite twiddly, particularly if combined with a dinner plate cassette, but it does mean most people can ride up most things without having to reduce cadence below 10rpm.

    slowjo
    Free Member

    Your mind is wrong

    😆

    OK thanks.

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    cynic-al
    Free Member

    Yup, you are pushing your gears, or you are strong, or live somewhere flat.

    oliverracing
    Full Member

    Unless I’m descending I find a 42-11 hard to spin out! (on a 1×10 setup)

    EDIT: but then again I will quite happily have a cadence of about 110 for most of the ride where I know most prefer 70-90rpm

    njee20
    Free Member

    Even at 90rpm 50-11 is 32mph, and 50-12 is 29.3mph, 120rpm is 42.6 and 39.1 – better to get aero at that point!

    cookeaa
    Full Member

    50-11 is a taller gear than a 53-12, and how often do you spin that out?

    This…

    Changed the Rings on my 105 Standard chainset from 39/53 to 38/50 a few weeks ago, just to try and get the gearing range to match my feeble legs with an 11-28 cassette, much better now, using more of the gears in the big ring, could probably have kept the 39t inner, but losing one tooth hasn’t hurt climbing any…

    I’d say the key thing isn’t actually having “high enough” ratios as such, it’s finding those comfortable gears to spin for 95% plus of the time spent on the bike…
    Mashing hard in top gear is an infrequent thing (for most people I’d have thought), so why prioritise chain ring selection around having a big ol’ dinner plate when plus or minus one tooth at the back has the same overall effect?

    thomthumb
    Free Member

    What is the rationale behind compact setups?

    that most people riding bikes don’t need racing gears.

    Alright if your in a chaingang doing 30-40 kmh. but most people ride around on there own/ with their similarly slow mates riding at 20-30 kmh.

    whitestone
    Free Member

    My first “proper” road bike had 52/42 and 12-24 on the back. Hard work in the Lakes 🙄

    Now with 50/34 and an 11-28 block I’m rarely in 50-11 even when blasting along in a chain line at 50kmh. I’ll manage 35kmh in the middle of the block without spinning like crazy or mashing the gears.

    stumpy01
    Full Member

    😳

    I’ve got a 50/34 compact with an 11-28 rear mech (it’s an SLX).
    I bought myself a 48T Stronglight chainring so I could make more use of ‘the big ring’ but couldn’t get it to work with the front mech (think I need some chainring spacers to get it to shift properly).

    I am pretty unfit though….

    mrblobby
    Free Member

    I’m tempted on the winter trainer just to be able to run a narrower cassette and still have a better selection of the “right” gearing.. Do a lot of z2 riding and power based intervals on the road and thinking it may be a better fit.

    captain-slow
    Free Member

    I’ve got a 50/34 compact with an 11-28 rear mech (it’s an SLX).
    I bought myself a 48T Stronglight chainring so I could make more use of ‘the big ring’ but couldn’t get it to work with the front mech (think I need some chainring spacers to get it to shift properly).

    Did you try lowering the front mech on its mounting? Son changed from a 50 to a 45 front chainring and we had to lower the front mech a good half inch to get it to work properly.

    stumpy01
    Full Member

    captain slow – Member

    Did you try lowering the front mech on its mounting? Son changed from a 50 to a 45 front chainring and we had to lower the front mech a good half inch to get it to work properly.

    Yeah, I tried all sorts. Had an extended attempt and gave up after ages struggling with it. Put it away and forgot about it, then tried about 4 or 5 months later but still couldn’t get it to work. It will shift from small to large, but then won’t go back down to small again.

    I think it’s the ‘dish’ (for want of a better word) on the chainring putting the teeth too far inboard (only by a tiny amount). With the mech in the right place (height-wise and rotation-wise), the cable removed and the screw that adjusts how far the mech can swing inwards wound as far out of the way as it’ll go (can never remember if that’s the high or low adjust screw), the mech physically can’t move inwards enough to shove the chain off the ring. It is very close though, because if I give the mech a push with my thumb, it will just about drop.

    I figured if I use some chainring spacers to move the outer ring a mm or so further out (perhaps less) it would probably be enough for the mech to then shove it off.
    Last time I had it all in bits I should have measured the difference between the original Shimano ring and the Stronglight one.

    mrblobby
    Free Member

    The 16t jump is a pain IMO, and a 34t is quite twiddly, particularly if combined with a dinner plate cassette,

    This is one thing that puts me off. I’d probably go 50/36. If you want to stay in a similarish gear when you change rings there’s an awful lot of shifting that needs to be done at the back, especially if running a close ratio cassette.

    Haze
    Full Member

    https://www.praxiscycles.com/conversion-bb/

    As far as the 50 goes (and assuming you’re in the market for one), if you find you don’t like it you could change it for a 52.

    My first 10S compact was 50/34 and 12-27, that got changed to 50/36 and 11-23 which I got by with for ages.

    Both my 10S and 11S now have 52/36 with 11-25 which I’m happy enough with but really miss the 16 on the 10S. That will be going to 12-25 since the 11 is only really used on the turbo.

    globalti
    Free Member

    My cycling buddy has a 53 big ring and I have a 50. It doesn’t make any difference because as a former mountain biker I’m more reckless and am usually faster down the hills anyway.

    TiRed
    Full Member

    A compact has smaller incremental changes, which helps with spinning. It also has the option of lower gears. I raced E123 on a 50 with 11/23 sprockets on Saturday. Average cadence was 105. Wasn’t really any different to the 52 it replaced, just a sprocket lower down and smaller shifts.

    I don’t spin out on 50/11 in the sprint either (sadly) 🙁

    matt007
    Free Member

    On the bb30 conversion topic, I used a praxis works converter to run an ultegra chainset on my tarmac sl4 which has specialized osbb, but basically same as bb30.

    Really nicely made piece of kit, felt totally solid when installed and hasn’t developed any creaks etc which I’ve heard some converters do.

    mrblobby
    Free Member

    Thought I’d do a quick resurrection on this one.

    Having always had 53/39 on my road bikes I just fitted a compact to the training bike. First ride today. Did a lot of fiddling with a spreadsheet to see what would work best given main motivation was wanting the right gearing with a 23-12 cassette. Went 50/36 in the end. Not much difference in the smallest gear over 39 with 25-11, and I lose a few gears at the top which I use infrequently on z2/z3 rides anyway. Really liked it. Nice close ratios and less shifting at the front.

    geetee1972
    Free Member

    I spent my juvenile and junior years riding the road and being mostly miserable because I was so utterly shit at going uphill (and I grew up on the edge of the Peak District so there was always a lot of up in the club runs).

    As an adult, I’ve come to realise that 52/42 on the bike of someone younger than 18 is tantamount to child abuse. How I ever actually even made it round some of those club rides (thinking of the Eagle and Child at Gradbach still brings me out in a cold sweat) is beyond me.

    My brother says the same thing. He remembers riding over the Sheffield with a mate to visit his mate’s sister on 52/42 and a straight through 13-18 seven speed block (block as in before cassette freehubs were invented). Now bear in mind tht to get back they had to come UP Winnats Pass.

    I am convinced the reason that road riding is so popular these days is because of sensible compact gearing. I know we all aspire to ‘need’ 53t big rings but it’s aspirational not reality.

    As Njee rightly points out the only time you’re likely to spin out is on a descent. If you can twiddle at 30mph i’ll personally give you a BJ!

    TiRed
    Full Member

    Raced a few more times on the compact. I won’t bother going back. The 11-23 is no different to a 12-25. If the puny ring offends the eye, so be it. Tell me at the top of the climbs. I do think 50/36 is probably the right place for most of my riding and all of my racing, but I hardly use the 34. You do notice the closer ratios of a 50 compared with a 52. Spin, spin spin!

    And of course GT, youth and juniors are now on restricted gearing for races. Once you’ve restricted that rear derailleur or swapped to a junior-specific rear cassette, they are set for club rides too. A big advance.

    geetee1972
    Free Member

    We were always on restricted gearing. I think it’s always been that way. IIRC the highest gear you could race as a juvenile in crits was 42×15 maybe?

    mrblobby
    Free Member

    I didn’t even bother trying the 34t, the 16t jump put me off and I didn’t want any smaller gearing. Looking at the data 50/36 seemed a lot more sensible. Shame they don’t sell chainsets in this combo really as I had to buy the 36t chainring separately 😡

    dirtyrider
    Free Member

    50/34 with a 11-28 at the moment, went up winnats at the end of last month, and i was trying albeit into the wind that day, average cadence 62?

    11-28? id have been happy with a 11-32

    dirtyrider
    Free Member

    they look like they needed bigger cassettes/smaller rings on stage 4 of the Tour of Andalusia yesterday

Viewing 25 posts - 1 through 25 (of 25 total)

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