Gearing for IMWI

duffeymt_24

 I am running a 50/34 and 11/25.  I know we are advised to have at least a 12/25,27,28, but what is the difference between a 11/25 and a 12/25?  

I am possibly going to try a 12/27, but I just wanted to know the advantages on hills with a 12/25 over an 11/25.  Or how about an 11/28 versus the 12/28?  

 

After looking at these I lost track of the logic behind these different combos.  

Spokane_Al

There is no advantage for hills moving from a 11/25 to a 12/25 other than tighter gearing gaps. The improvement comes by moving from a x/25 to a x/27 or x/28. Moving from an 11 to a 12 in conjunction to moving to a 27 or 28 will perhaps provide some smoother shifting in that the gearing gaps are a bit tighter.

jburbatt

The difference between the 11 and 12 will happen on the flats/downhills giving you more gears on that end. Like Al said, depending on how you spin might give you smoother shifting with one over the other. But it won't affect your ability to go up the hills. And for WI, IMO I'd go with the 27/28, mo' gears is mo' better

jburbatt

PS- If you haven't already, feel free to join the EN Chicago Sleeper Cell page on FB. You can search me out and I'll be glad to add you to the group!

William Jenks

Matt- I was just out on the course with the rally.

It all kind of depends on your priorities. The stock answer is that you can never have too low of a gear, particularly on that course. To that extent, the 12-27 or even 12-28 is the way to go.

On the other hand, there are lots of uppy-downy spots on the Madison course, and you MAY benefit by having an 11 (rather than 12) as your highest gear if you are willing to pedal more on the downhills in order to ride up the next little roller faster without slowing as much or working as hard.

Finally, i fyou go to something like 11-28, it's very likely that you'll have a gear gap that you aren't very happy with.

This is a nice little site that lets you visualize various gearing combinations and see where the gear gaps are and how far the gear ratio extends:
http://public.tableausoftware.com/views/bikegears/CompareBicycleGearing

I run a 50/34 in the front as well. Until this point in the season, I had been running a 12/25 in the back and am quite familiar with how it rides (e.g., I did the KS half which is similar in hills.) Over the weekend, I tried out an 11-26 in the back. I am a middling cyclist...not any stud by any means. For the record, I liked the 11-26 a lot and plan on sticking with it. If I could have replaced the 26 with a 27 and changed nothing else, I probably would have done it...but I am not sure where different cog gaps are on a real 11-27.

Coach Patrick

Great advice William....thanks for putting that out there!

Jeff Unruh

Matt,

Not sure how strong a cyclist you are but I rode a compact with 12-27 and would have loved more gears. I can't remember the name of which climb (2nd shorter climb after Uphill Grind) it was but I was struggling to keep my watts under 250 (220 FTP) and was in granny gear, 42 Cad and 4.5 mph.

My cycling has a long way to go (2.6 W/Kg) so take that as a data point from a BOP biker.

duffeymt_24

Thanks everyone! Makes sense now. So, in regards to cost/benefit of a 12x27 versus a 11x28, the latter gives me an extra gear going uphill AND a faster downhill gear, but I give up a tight gap between ~21 and ~23 mph, which seems like a sweet spot.

I rode IMWI last weekend with a 11x25 and I reached for another gear that I didn't have a few times and I don't think I made it down to my 11 more than a few times.

Any advice on what I should consider when deciding between a 12x27 and 11x28?

mancona

@Matt - if you are particular in your cadence I would recomend the 12-27 as the cadence gap in an 11-28 can drive some folks crazy. However if you are flexible and can ride at a range of maybe 15rpm comfortablely then the 11-28 with give you the best of all worlds as you can spin up climbs and still have the 11 for the descents.

William Jenks

If you have them both, then just try them on some hilly ground. If not, I'd suggest having a look at that utility I put up to try to eyeball the gear gaps, which will obviously be bigger for 11-28 than 12-27.

Remember that gearing is a ratio of front/rear, so that the difference between 50/12 and 50/11 is bigger than the difference between 34/27 and 34/28 (just check on a calculator!)....this is too bad, since it's really at the low end that you probably want the help. But again, that utility I put up will help you at least visualize the difference.

Coach Rich

After two days on the IMWI course, and after riding the loop 4x now, I think the cadence gap issue of a 28-12 vs a 27-12 is less of an issue on WI, simply because you aren't at any one cadence for more than a couple minutes on that course. I was a gear changin' fool, all weekend, really giving my drive train a great workout.

As for the 11 vs the 12, I think it's a function of "at what speed do you start to wig out?" While most of the high speed stuff (ie, stuff that will take you up > ~37-38mph where you'll likely spin out on a 50-12) is straight, good visibility, road surface, not into a corner, etc. some people get wigged at 34mph and so don't need the 11t. I think the 11t is best for those people who want to squeeze every once of speed out of every downhill and are comfortable with any braking or cornering that has to be done to negotiate the next terrain feature.

Short answer, for most people I'd recommend 27 or 28t and the 12t.

duffeymt_24

Thanks everyone, a 12x27 it is! If I change out a 11x25 to a 12x27, will I need to make any changes to derailleurs, chain, etc?

William Jenks

Assuming you have a pretty normal/stock derailleur, there won't be any adjustment needed there, except maybe a bit of cable tension.

Get the cassette and see if it works with your current chain length. The biggest gear is only a couple of teeth longer, which is a link or two. Depending on how your current chain length/tension is, you may or may not need to do anything. My guess is not. The normal play of the pulleys on the bottom will just be at a slightly different angle. Remember also that you are almost certainly using this new low gear exclusively with your small front chain ring, so the total length of chain required is probably within some other gearing combination anyway. You would obviously only be really testing the limits with the bad cross-chain situation of big chain ring in front and big cog in back.

However, if you are shifting roughly in the easiest couple gears (and it's not just alignment), take it to the LBS and have them measure the chain length...not the whole chain but how long a short section of it is. You are looking to see if you have stretched the chain just through normal wear. There are special little caliper tools that do this in 5 seconds. If your chain has stretched, use this as an opportunity to replace it and get it sized for the new cassette. If it has not stretched, see if they'll just put a link or two on there and not charge you for a whole chain.

[Deleted User]

Posted By Rich Strauss on 01 Aug 2011 12:33 PM

After two days on the IMWI course, and after riding the loop 4x now, I think the cadence gap issue of a 28-12 vs a 27-12 is less of an issue on WI, simply because you aren't at any one cadence for more than a couple minutes on that course. I was a gear changin' fool, all weekend, really giving my drive train a great workout.

As for the 11 vs the 12, I think it's a function of "at what speed do you start to wig out?" While most of the high speed stuff (ie, stuff that will take you up > ~37-38mph where you'll likely spin out on a 50-12) is straight, good visibility, road surface, not into a corner, etc. some people get wigged at 34mph and so don't need the 11t. I think the 11t is best for those people who want to squeeze every once of speed out of every downhill and are comfortable with any braking or cornering that has to be done to negotiate the next terrain feature.

Short answer, for most people I'd recommend 27 or 28t and the 12t.

So Rich, for those folks who are on the higher end of the W/kg scale and don't get wigged out at the high speeds, i.e., the 11t folks, what do you recommend for the rest of the cassette?  25t, 26t, or 27t

mancona

Hey Adam... I've rode the IMWI course with 50/34, 52/36, 53/39 combined with everything from an 11-23 to 11-28. I personally find 52/36 and 11-26 to be my favorite do it all combo for any hilly race including IMWI. FWIW, I'm at 4.6 w/kg right now, and rode that combo last weekend. I was able to stay at my Gear 4 watts on every climb except timber lane. A 27 or 28 would let me get up timber lane under gear 4 watts, but it's so short that I don't think it is worth it for me.

Coach Rich

Posted By Adam Weeks on 02 Aug 2011 03:33 PM

Posted By Rich Strauss on 01 Aug 2011 12:33 PM

After two days on the IMWI course, and after riding the loop 4x now, I think the cadence gap issue of a 28-12 vs a 27-12 is less of an issue on WI, simply because you aren't at any one cadence for more than a couple minutes on that course. I was a gear changin' fool, all weekend, really giving my drive train a great workout.

As for the 11 vs the 12, I think it's a function of "at what speed do you start to wig out?" While most of the high speed stuff (ie, stuff that will take you up > ~37-38mph where you'll likely spin out on a 50-12) is straight, good visibility, road surface, not into a corner, etc. some people get wigged at 34mph and so don't need the 11t. I think the 11t is best for those people who want to squeeze every once of speed out of every downhill and are comfortable with any braking or cornering that has to be done to negotiate the next terrain feature.

Short answer, for most people I'd recommend 27 or 28t and the 12t.

So Rich, for those folks who are on the higher end of the W/kg scale and don't get wigged out at the high speeds, i.e., the 11t folks, what do you recommend for the rest of the cassette?  25t, 26t, or 27t

I put on the 26-11t when I assembled the bike yesterday, so I'm running 50/34, 26-11t. I rode the course this past weekend with 25-12t:

• The longer climbs put me < 60rpms. Not a big deal on the road bike but for some reason on the tri bike I had a very strong impulse to stand. Not a huge deal, as I can stand at nearly the same watts as sitting (ie, I have very good control of my watts), and am much more comfortable, but I'd still like to sit at > 65rpm for a long time before I want to stand.
• With the 12t, there were a few places where I spun out at my watts before I ran out of road. In other words, with the 11t there a few spots where I can wind it up to > 42mph at my watts before spining out vs ~37-38mph with the 12t.

The caveat to all of this is identifying if/when you "need" to stand in order to power the bike vs want to stand due to not being comfortable with the cadence that staying seated would put you at. And then, when you do stand, your eyes are locked on the dial and you are NOT crushing the watts to get up the hill. I can do this with either the 25 or the 26, but will run the 26t to have the extra gear and to have the 11t to conserve momentum on downhills.