Silvercivic27

All this cassette/gear talk made me wonder about this. I have a compact 105 crank, 170mm (50/34). I love being able to climb the hills (which are quite steep in my area with grades in the high 20s/30s), but spin out downhills, wishing I had more. It also wouldn't be bad to have even more for these steep grades, and I noticed I could get an Ultegra cassette in 11/28 for about 80 bucks. Why shouldn't I do this? Is there a problem with the ratios in between, or would it screw something up That I'm not thinking of? Also, a separate question: what is the current thought on the length of the crankarm. I'm a pretty short guy 5'8 with pretty short legs (pant inseam 29ish)

merlinextraligh

1) I seriously doubt the grades in your area are in the high 20's/30's. (There are few paved roads that exceed 30% grade.

2) If your climbing grades in the high 20's/30's with a 12/27 and a standard crank, you don't need a lower gear because you're pretty much ready for your first pro contract.

3) If you're spinning out a a 53/12, you need to work on your spin. That's 50 mph at 140 rpm. Above 50 mph, it doesn't make much sense to pedal, as oppossed to tucking in.

4) If you're descending 30% grades, you don't need to pedal anyway, just tuck, layoff the brakes and you'll hit 70mph+ pretty quick.

Silvercivic27

1) doubt all you want, it's true.
2) compact crank. Compact crank.

Thx.

merlinextraligh

^ descending a 30% grade with 0 watts input tops you out at a speed of 96 miles per hour.

merlinextraligh

And climbing that 30% grade at a speed you can turn over a 34/27 takes about 800 watts.

30% is friggin steep. Unless we're talking a block long section of some City street, you don't routinely see grades like that. Thus I sincerly doubt that there are multiple climbs around you in the high 20s/30s

Brasstown is 21%, and that's only for a few hundred yards. L'Alpe de Huezt tops out at 11%, and that's for a short distance, averaging below 9%. Mt Ventoux is in the single digits, etc, etc.

Bob Ross

Well, I think there's quite a bit of exteremely valid grey area between "needing to work on your spin" and "140 rpm".

ime 120 rpm is the threshold above which it just gets comical, and since to me one of the most important aspects of road cycling is being able to maneuver with grace, spinning any faster than ~120 rpm for more than a few seconds isn't a sensible option. Yet I routinely spun out my 50/12 combination at ~120 rpm during long descents. Changing to an 11-26 cassette was a big help for me in terms of keeping my top end usable.

Silvercivic27

I guess the basis of the question is: what's the downside to a wider range. Will it not be enough to notice/make a difference on either end/etc.

merlinextraligh

setting aside my quibling about grades, It will make a small difference on both ends. Mathmateically the 11 has a bigger effect, than the 28.

You cna get a feel for this with Sheldon Brown's gear calculator. Look at speeds for a given rpm with the various combinations.

Downside is you give up a little in spacing. Biggest difference is you lose the 16, and the jump at the bottom end is 4 teeth instead of 3.

So the advantages and the disadvantages are both fairly minor. Probably not worth changin until you wear out the 12-27 and need to replace it.

Dean V

If the grades you are riding really are that steep and reasonably long I would put a triple crankset on. Then you can get the low and high gears you want and not have to use a cluster with large jumps between gears.

timeforheroes

1. agreed
2. agreed
3. agreed
4. Agreed

urbanknight

I'm actually going to disagree with Merlin about the 11. Although it is perfectly possible to pedal to 45mph+ with a compact and a 12, sustained descents are much more comfortable at a cadence lower than about 120 (at least for me).

merlinextraligh

honestly, I missed that the OP was using a compact. I'll agree that there's more reason to run an 11 with a 50 tooth big ring.

Also, I get that bigger than a 53/12 may allow you to run a desired cadence on a decent. What gets me going is the repeated assertion on BF that "I need an 11 because I spin out my 12"

Phantoj

lol, 20% is friggin steep. What 30% is, I don't know; I've never seen it.

wrr1020

What are the names of these roads with "20-30% grade climbs", i'd love to google them. One steep city block doesn't count.

merlinextraligh

It appears the OP maay live in Pittsburgh, and I'm guessing he may be referring to the Dirty Dozen, one of which is reported to be 37%.

However, anything that steep is darn short, not something you'd crank down in a 53/11, and the claimed grades may be just a bit exaggerated.

https://spreadsheets.google.com/ccc?...EE&hl=en#gid=0

Distance (mi) Elevation (ft) Avg Gradient
Center 0.67 396.98 11.22%
Ravine 0.58 401.86 13.12%
Berryhill 0.2 154.2 14.6%
High/Seavey 0.32 209.97 12.43%
Logan 0.33 314.96 18.08%
Rialto 0.13 118.11 17.21%
Suffolk 0.41 321.52 14.85%
Sycamore 0.48 275.59 10.87%
Coast/Canton 0.2 98.42 9.32%
Wenzell/Boustead 0.37 236 12.08%
(Boustead only) 0.22 145 12.48%
Welsh 0.16 167.33 19.81%
Barry/Holt/Elanor 0.51 337.93 12.55%
Flowers/Tesla 0.88 426.52 9.18%

nosignature

i'd love to know as well, 30% is a friggin wall.

but i run an 11-28 cassette to climb with on a standard crankset, and i have no issues with the ratios save for that i can't go crosschain in the big ring thanks to either the size of my chain or the derailleur cage, or both. the big jumps in gearing occur after the 21 cog, and it's never really bothered me since by that time i'm just looking to spin up a hill.

bikerjp

The downside is probably just the increased jumps between gears. A 12-27, for example, goes 12, 13, 14, 15, 16, 17, 19, 21, 24, 27 (sram) so the first 6 are smooth one tooth changes then 2-3 tooth jumps in the upper gears. An 11-28 goes 11, 12, 13, 14, 15, 17, 19, 22, 25, 28 so you get 5 smooth one tooth shifts and then jumps of 2-3 teeth. I got a 11-28 though after a lot of research and decided it was a good split duty cassette. The bottom 5 gears are for flats and downhill and the top 5 are my climbing gears.

Dean V

When the roads are reasonably flat I certainly don't like a cluster without a 16T. The 17-19 jump is ok but don't like a 15-17 jump.
Also got to agree with Merlin about these people that think 53/12 isn't enough gear.

Silvercivic27

It cracks me up that you guys spend so much effort trying to debunk a grade claim instead of trying to actually help me answer my question. So in essence, is the 11-28 cassette really something more suited to a 53/39 crank as opposed to a 50/34 crank due to the ratios? Finally, any comments on crank length?

revchuck 

+1 on this. Unless you live somewhere with long descents, the 11 would rarely be used. OTOH, that 16 tooth cog is right in the middle of the cassette, and gets used quite often.

urbanknight

Yes, the downside is the larger jumps. This is a problem if you are particular about your cadence. I used to be princess-and-the-pea about it, but now I'm comfortable with a 10-15 rpm range, so the wide spacing is fine. Racers going for max efficiency might feel differently, but they also don't need granny gears like I do.

urbanknight

1) There are too many big penis stories on this board for people to resist calling BS on everything.
2) The 11 is great with a compact crank because it makes up for the loss of high end seen with the 50. The 28 is great because, mated with a 34 chainring, it gets pretty close to the low gears most bikes with triples come with. I personally use the 34/28 combination for any grade steeper than about 9% and longer than about 1/4 mile. If I frequently climbed grades around 20%, even if only for 1/2 mile, I'd have a triple. 30%, I'd ride my mountain bike and not worry about pedaling downhill.

achoo

When you're way out in left field about the grades you climb, one starts to wonder what else you're off base on.

captnfantastic

HTFU. Sometimes I climb on my ss at 48x17. Bigger gears put hair on your chest!

Jakedatc

I run 50-36 after swapping out my 34t
I just switched from 9 speed 12-27 to 10 speed 11-28 for that reason and it helps on both chainrings. I can use the 12t in my 36 ring when in rolly sections or a quick downhill before an uphill. can use the 25t in the 50 on an occasional short hill to power up it. I live in an area without large hills but they tend to be steep and punchy 6-10% for 1/4-1/2 mile with longer 1-2mi hills that come up on occasion. So looking at the whole cassette instead of just the ends is useful too.