To those flying the Eagle - what size chainrings are you running?

Discussion in 'Parts 'n Stuff' started by Nautonier, Apr 21, 2017.

  1. Nautonier

    Nautonier Eats Squid

    I'm geeking out on gear inches and am seriously tempted by the fantastic spread of the Eagle. Just wondering if folks are using the increased spread at the low end or high end. I tend to ride up some very steep hills and would be tending towards a 30 or 32t up front as I'm not fussed about spinning out on steep tech tracks on the way down and never chase fire road KOMs haha.

    At the moment I have a 32 x 46 combination (on a 170/160mm bike), giving me 19.59 gear inches (81.46 at the other end), which I'm finding not quite low enough. As it's an 11 - 46t cassette, I'm reluctant to go to a 28 or 30 on the front as then I won't have enough at the other end.

    Other bike (130/125mm) has 32 x 42 combo (21.27/89.57), which, whilst being a much lighter bike, also isn't quite low enough for sustained mega-steep climbs.

    Very tempted by the 32 x 50 Eagle combo giving 17.91 at one end and 89.57 at the other. Wish Sunrace or Shimano would come out with an 11 - 50t cassette as that would save a lot of $$...

    What front rings are y'all running on Eagle?

    ##edit: I see the One Up Shark cogs are a cheap(ish) fix.

    ####edit: Has anyone tried using the One Up 50t with a Sram derailleur? Would it work on a Sunrace cassette I wonder?
    Last edited: Apr 21, 2017
  2. pharmaboy

    pharmaboy Eats Squid

    I'm not running eagle as I don't see a need, but I do run a xx1 and a shimano both with 42. The shimano I run with a 30 at front and sram with 28. The sram has heaps more top speed with that extra cog at the back, but really it's not common to think I don't have enough on the shimano bike, it'll still spin up to 50kmh on a downhill piece of road, you just spin 20 times then coast etc

    Don't forget about the 9 tooth options by e13 and Leonardi racing, but you need to have direct mount sram cranksets to get good chainlines on a 28 or even 26 is available as well, so much of this question depends on what you have on the front
  3. nzhumpy

    nzhumpy Likes Dirt

    I'm running a 32 up front, only had 4 rides on it so far but I'm yet to hit the granny, when the bike goes in for its check up in three months I'll be putting a 34 on (depending on space as the 32 is already tight).
  4. Nautonier

    Nautonier Eats Squid

    Good point, I'm running Sram direct mount GXP on both bikes. Interesting to see you're running a 28t up front with the 10 - 42, that's giving you a very low gear of 18.75 gear inches, which would be enough for the toughest climbs.

    I see that Sunrace have indeed come up with an 11 - 50t solution! Looks like it will work with standard Shimano and Sram derailleurs.
  5. pharmaboy

    pharmaboy Eats Squid

    BTW! I should have mentioned I'm 29" only, there's about a gear difference between that and a 27.5, so I'd just go with your own gut reaction, and that is you need one more easier gear - everyone's needs are so dependent on where they ride, how, with whom and what bike
  6. Nautonier

    Nautonier Eats Squid

    Oh yes, I forgot to mention that I'm on 27.5" bikes!
  7. puffmoike

    puffmoike Likes Bikes

    When I'm riding I just think about 'gears' – rather than gear inches – and if you're not changing anything else on your bike (tyre size, etc) I think that's the best starting point for trying to anticipate what changes you should make.

    Do you wish you had 'one more gear'? Two?

    If you're currently running a Shimano 11-46T then as you change down from your sixth down to your second lowest the difference is consistently 14–17% each time. The leap from second to the granny is 24%. If Shimano made a hypothetical 12s cassette that added another granny which had the same jump it would be a 57T. And even if it was just a 'regular' jump it'd be something like a 54T.

    The upshot being if you bought Eagle and kept the same 32T chainring you'd only be gaining about 'half' a gear at best at the low end. I doubt that's going to be a noticeable difference. I think you're going to need to go to a 30T at the front regardless of what you do with the cassette (stick with what you've got and lose top end speed, or buy Eagle or an aftermarket cassette for Shimano with smaller cogs if you're not prepared to give that up).

    This gear calculator is good for comparing combinations if you don't want to set up an Excel table from scratch.
  8. puffmoike

    puffmoike Likes Bikes


    Asking people what gears they ride is useless to you. You already know what you ride, how fit you are, and in particular what trails you're currently struggling on. Back your experience to decide if you need 'one more gear', 'two more gears' (or even just 'half a gear') and only after you've done that then start playing with Excel or an online gear calculator to work out a suitable configuration.
  9. Nautonier

    Nautonier Eats Squid

    It's hard to quantify exactly in terms of needing 'extra gears', but yes, I agree that it's personal preference. I think the best way forward is experimentation, which can hopefully be achieved at minimal cost if I start with chain rings.

    I find that gear inches are a useful measurement as it's easy to see the differences across cassettes and chain rings.

    In terms of an 'extra gear', my understanding based on comments above, is that this is a gear which is approximately the same percentage jump up from the last one. At the moment it feels like the bike with 32 x 46 is giving me less than one extra gear from the bike with 32 x 42. Should we call this 'half a gear'?

    Not sure how the unit of gears relates to graduations on the chain ring. Would going from 32 x 42 to 30 x 42 be more than an extra gear? Two? How many gear inches is a gear?

    At the moment I can confirm that I'd like about half a gear more on the 32 x 46 bike and a whole extra gear on the 32 x 42 bike. At a guess I'd imagine this would be about the same as 32 x 50.
  10. Keachy

    Keachy Likes Dirt

    Got thru the Otway 300 with eagle on 32t up front. Even the 25% sections were a breeze. Just rode up with steady cadence and kept the weight over the front end.

    Sent from my iPhone using Tapatalk
  11. puffmoike

    puffmoike Likes Bikes

    Agreed (see below)

    Agreed within reason: they're useful when you're ready to compare specific chainring and rear sprocket combinations (and especially if you need to compare across different wheel sizes, tyre diameters, etc).

    But I just don't think it's a particularly intuitive way of trying to initially think about gearing, when you're simply trying to establish how much easier (or faster) you want to be able to go.

    If you're anything like me you just intuitively change gears, almost without realising you're doing it. Sometimes you go one gear up or down, and sometimes you grab a couple all at once. You have no idea how many gear inches you're currently pushing, or what you're gear inches you're going to change to. You probably don't even know what cog you're in. You just know you want to make it a bit easier/faster (one 'gear' change) or a lot (two or three 'gear' changes). And on a modern mountain bike, regardless of what cog you're in, each gear change roughly equates to 15% difference in gear inches (a notable exception being the granny gear on your 11–46).

    In my opinion thinking of each 'gear' as a 15% difference in how far you travel per pedal revolution is a better starting point than trying to understand what the difference between say 19.5 and 21 gear inches, or 81 and 93 gear inches, means when you're on your bike (they both happen to be about 15%, but unless you're a bit of a rain man that probably wasn't obvious to you as you read it).

    FWIW I bought a 29" Trek Fuel EX late last year, replacing an eight year old triple chain ring 26". I test rode a 1x Fuel EX 9 for two days at the You Yangs and was (pleasantly) surprised that I wasn't wishing it went lower. But when it came to buy the bike I was mindful that when I'd last ridden up the Stonefly climb at Mount Buller I swore that if I ever bought another bike it had to have as low a gear ratio. So I used an online gear configuration tool to convince myself to get the 2x XT setup rather than the 1x SRAM option. Here are the two different bikes' gearing calculations (which accounts for cassette, chainrings, wheel diameter and tyre size) .

    Yep. You're feel is pretty much spot on. Which is why I reckon you should back your feel to work out how much more 'gear' you want overall. Once you've done that then you can work out combinations of chainring and cassettes with the online tool I've begun configuring for you (see below).

    Gear inches can't be thought of as a 'gear' because it's the percentage difference between gear inches that equates to how we intuitively think about gears when we ride (and as my examples above show, the difference measured as a raw number, as distinct from a percentage, might be small (1.5) or large (12) depending upon which end of the cassette you're talking about)

    This is the point that gear inches, and excel tables or the aforementioned online gear calculator become useful.

    Here's the online gear calculator setup for you, with five variants: 32/11-42; 32/11-46; 30/11-42; 30/11-46; 32/10-50 (Eagle).

    (all assuming 2.3" tyres on 27.5" wheels, but so long as these values are consistent it doesn't matter what they are for the purposes of comparison).

    So going from a 32x42 to a 30x42 will feel almost like your 32x46 (more like a hypothetical 32x45). And if you did go Eagle a 32 would spread the extra range slightly more across the low than top end, but essentially give you an extra gear at each end, whereas a 34-50 would feel pretty similar to your 32x46.
    Last edited: Apr 21, 2017
  12. dunndog

    dunndog Eats Squid

    They sure have, and I'll be running that with a 32. Currently running a 30-11/42, but that was reduced from a 32 mid-transnz... mt cheeseman claimed another victim!
  13. andrew9

    andrew9 Likes Dirt

    This is my favorite, it lays the gears out on a table, so you don't need to compare 1.40 to 1.32 in your head
    you can add a different wheelsize with the "compare two setups" button
  14. Nambra

    Nambra Likes Dirt

    Whilst we have the brains trust on line, a couple of related queries...

    How do oval chainrings affect things? From what I've read from the 'believers', oval rings help to put the power down more consistently, resulting in better traction at the rear wheel - if that's correct, does that give you a sensation equivalent to an easier gear ratio?

    Second, and in relation to wide range x11 cassettes, does the jump from one cog to the next leave you wishing there was one in between? In other words the overall range is too much for the number of cogs? Guessing that as the range stretch is mainly at the granny end, it's not so noticeable.
  15. Nautonier

    Nautonier Eats Squid

    Thanks Puffmoike for a brilliant and detailed explanation of all of the factors at play. Seeing the variants in the calculator gives a really good picture of what is happening with the ratios. I'm on a Sunrace cassette, not Shimano, so not such a big jump at the end (Sunrace uses a 40 before the 46).

    I think the solution in the short term (to try out) in achieving half a gear more on the big bike and one gear more on the little bike will be to switch to 30t and 28t rings upfront, giving roughly the same low gearing:

    Screen Shot 2017-04-21 at 8.03.52 pm.png

    The Sunrace 11 - 50t cassette hasn't been officially released yet, but I'm sure it will be out soon and most likely be around the $100 mark (the 11 - 46 is $80).

    I find the Stonefly climb at Buller fine on 32 x 42, but if I was doing it more than once in a day I'd be wanting a lower gear. I usually do ~1000m climbing on most rides and often there's sections that are steeper than Stonefly. My passion is descending, so my thinking is that lower gearing will allow me to save more energy and get more runs in!

    Attached Files:

    Last edited: Apr 21, 2017
  16. puffmoike

    puffmoike Likes Bikes

    Just in case I'm considered part of the so-called brains trust…

    No idea. And in mathematical terms I don't think there'd be a conclusive answer. Never ridden one, so can't comment in terms of how it feels.

    The jumps on SRAM's 10-50 vary between 13% and 20%. By contrast Shimano's 11-42 range between 11% and 18%. And in both cases the jumps are pretty evenly spread right across the range, and perhaps counter intuitively the biggest jump is between the smallest cogs, not the granny (this is not true of Shimano's 11-46).

    I've never ridden Eagle, but I very much doubt you'd wish there was an extra gear in between each one (in contrast to a road cyclist, who wants those smaller jumps that a tight block like an 11-25 cassette gives so they can maintain a consistent cadence as a road slightly rises and falls).
    Last edited: Apr 21, 2017
  17. Nautonier

    Nautonier Eats Squid

    Hope they come out soon, I've emailed them to see what the deal is. Yeah that Cheeseman road is beast once you get out of the trees and it pitches up! I did it with 32 x 11/42 three times in one day and it almost killed me...
  18. puffmoike

    puffmoike Likes Bikes

    I climbed Buller two weeks ago and whilst I used my 26-42 briefly, I'm pretty confident I could have done it with a 32-42 because a) the new bike climbs beautifully and b) I've been riding lots since getting the bike so I'm fitter and better rider than I've ever been before. ;-)
  19. puffmoike

    puffmoike Likes Bikes

    Nautonier, this is a fantastic visualisation tool. Ignore all my ramblings and just look at this visualisation of your Sunrace 11-46 with a 32T chainring!

    It shows gear inches across the top (with MPH selected). The % difference between each gear is shown to scale, but as you can see the gear inches scale constantly changes, which is why I don't think it's a very useful way to think about gearing (to bel clear it's entirely valid for calculating, I just feel it makes it hard to think about).
    Last edited: Apr 21, 2017
  20. Nautonier

    Nautonier Eats Squid

    Yes indeed, that is a beautiful thing!

    Screen Shot 2017-04-21 at 8.41.23 pm.png

Share This Page