Considering an unusual gearing setup

abtrumpet
abtrumpet Posts: 16
edited June 2019 in Workshop
Backstory: I was riding Ultegra 50/34 x 11-28 and found it acceptable with the exception that I actually didn't have enough gears when going downhill or on a smooth flat. I'm a big guy with an FTP around 300. A local dude made me an irresistible trade: he gave me a Quarq powermeter with a bunch of nice chainrings and an upgraded Di2 junction box for some old groupset parts I had no need for. The Quarq is 130 BCD. So, I fit an 11-32T rear and 53/39 front on it. I have a Di2 long cage rear mech. Here is what I am thinking: maybe reduce the inner to 38 for better climbs, or, fit an 11-36 SRAM cassette on it. Crazy I know, but I very much like this powermeter so I am constrained to 130 BCD.

Comments

  • imposter2.0
    imposter2.0 Posts: 12,028
    39>38 teeth is going to make very little real-world difference. I'd go for the cassette option instead..
  • joe2008
    joe2008 Posts: 1,531
    abtrumpet wrote:
    Backstory: I was riding Ultegra 50/34 x 11-28 and found it acceptable with the exception that I actually didn't have enough gears when going downhill or on a smooth flat.

    50 x 11 is a bigger gear than Eddy Merckx used.
  • imposter2.0
    imposter2.0 Posts: 12,028
    abtrumpet wrote:
    I actually didn't have enough gears when going downhill or on a smooth flat.

    Doubtful. 50x11 at 90rpm (for example) will give you 32mph on the flat. On a downhill, if/when you spin out, just tuck in and freewheel.
  • akh
    akh Posts: 206
    I'm not clear what you want to achieve on the low end. I guess the implication is that 39x28 isn't as low as you'd like, but are you looking to match your old set up or go even lower? 39x32 is almost the same as 34x28.

    Try this website, you can compare two different setups. You can also drag the chainrings and sprockets to make any combination you like.

    http://www.gear-calculator.com/?GR=DERS ... 8&UF2=2135

    Percentage wise, you've lost a lot more on the low end (about 15%) than you've gained at the high end (about 6%), but of course it's up to you how you feel about that trade-off.
  • abtrumpet
    abtrumpet Posts: 16
    Yes, which is why I'm asking the question as to what would be most comparable to my previous setup. As I am constrained to 130 BCD with the Powermeter I'm looking at various options...it seems though, that maybe a 11-34 or 11-36 cassette is the better option and keep the 53/39
  • abtrumpet
    abtrumpet Posts: 16
    Thanks for showing me the calculator. I'm looking at it right now -- you are correct, I probably won't use such a massive gear on the high end. On the low end, it does appear I am losing something with 39/32, but not a ton. With 39/36, that's mostly mitigated. The tradeoff is the massive gear differential in the cassette.

    With the 53/39 + 11/36 combo vs 53/38 + 11/36, I see that I would gain maybe 0.5 kph @ 90 on the low end, but the tradeoff there also would be a number of redundancies between the big and little rings. So...I think 53/39 + 11/36 will be my choice, and I will see how that goes.

    The other option, of course, is find somebody with a 110 BCD Quarq to do an even trade...but that seems unlikely given that most people are moving away from 130 anyway!

    I'll update you all on my choice. I live in Utah where we have plenty of steep climbing. I certainly didn't intend to compare myself with Eddie Merckx! :) But I do like to go fast downhill.
  • cougie
    cougie Posts: 22,512
    I think you need to learn how to spin a gear.
    50*11 should be ample. Try riding a fixed gear for a while.
  • cycleclinic
    cycleclinic Posts: 6,865
    The R8000 RD will just about cope with a 11-36T and a double. Your starting to push the limtis of the rear mech though.
    11-34T is very viable though. Do you have this rear mech or the older 6800 in which case 11-32T is all that should be used.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • abtrumpet
    abtrumpet Posts: 16
    I can't do a compact, remember, because of the BCD? Otherwise, I would. If I found somebody to trade my Quarq powermeter for a 110 I'd go for it.

    I am using the RD-6870-GS derailleur. 11-34T should work well. I think 11-36T might be overkill, but I don't know for sure.

    Since I just bought the 11-32T and made this crazy setup, I don't think I'll change anything else out quite yet. We shall see how I do on the hills.
  • svetty
    svetty Posts: 1,904
    A 38 inner chainring won't make a huge difference but it will make some difference and is relatively cheap. It also won't push the limits of your mechs. Why not try it and see?
    FFS! Harden up and grow a pair :D
  • philbar72
    philbar72 Posts: 2,229
    sounds like a 32/34 sprocket is whats needed. stick to the 53/39 on the front, usually a 130bcd's lowest limit is 39 tooth inner....
  • timothyw
    timothyw Posts: 2,482
    39/32 is pretty near identical to 34/28, struggling to see why this thread even exists given you have said you wanted more top end choice of gears, which is what you now have?

    You can put on a 38 if you want, but the change is small. It's also the smallest you can get with 130 BCD.

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