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Extreme climbing cassete

Old 09-08-20, 12:37 PM
  #1  
acsoaresbr
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Extreme climbing cassete

Hi there!

I will be facing climbs that are steeper than my legs would allow me to (over 25% gradients) and I was considering to use a 11-34 Ultegra cassete. I have a 11 speed Shimano Ultegra groupset, long cage rear derailleur, 34/50 crankset). However, I noticed the 11-34 cogs are 11-13-15-17-19-21-23-25-27-30-34 - meaning I have a 4t jump to my last gear, which is a bit too much. I looked at my existing 11-32 cassete (cogs: 11-12-13-14-16-18-20-22-25-28-32), and realized mixing them would be ideal. I could potentially end up with a 30-32-34 bigger cogs. However, the last cogs seem to be machined together! So, that is not an option... quite frustrating.

Is there any way to get a 11-speed Shimano compatible cassete that would look something like: 12-14-16-18-20-22-25-28-30-32-34?
Is there any company that build custom cassetes?

Thanks in advance!!
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Old 09-08-20, 12:44 PM
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Triple crank is your next buy ... Shimano Ultegra had a 130 -74 _ 50 -39- 30, 74bcd will take a 24t..
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Old 09-08-20, 12:48 PM
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If you are climbing 25% grade you will be in the 34 cog on the rear all the time. Consider 11-36 cassette instead, if you can get it to work.
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Old 09-08-20, 12:52 PM
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I'm not upon 10 & 11 speed stuff, being happy as a clam with my 3X9.
The cheaper 9 speed cassettes don't have the 3 largest cogs mounted on a spider. (Tiagra)
I'm not sure what the lowest 11 speed level is, but you might look there.

I think you'd actually be disappointed at your 6% jump from your lowest gear vs an 18% jump at your highest.
Is there a smaller "small" ring you can install? A couple teeth less there and keep your current cassette would probably give more "balanced" gearing.
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Old 09-08-20, 01:00 PM
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It's not as big as you think. When in the 34 ring the difference in ratio between your 11 and 12 cog is a bigger difference than your 30 and 34 cog.

(34/11) - (34/12) = .26
(34/30) - (34/34) = .13

So actually the change in gearing from that 4 tooth difference is only half the change of a 1 tooth on the small side of your cassette.


You need to figure out how long that section of 25% actually is. If only a few hundred feet, then maybe not so big deal if the rest of the section is only 6% or something less.

Last edited by Iride01; 09-08-20 at 01:41 PM. Reason: 12% to 25%
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Old 09-08-20, 01:03 PM
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fietsbob
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Issue the carrier for all but the smallest cogs solved, was the cog spline digging a divot in the cassette driver spline
due to the concentrated force of going up hill against gravity , has on the thin edge of the cog interface ..
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Old 09-08-20, 01:10 PM
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Originally Posted by acsoaresbr View Post
I noticed the 11-34 cogs are 11-13-15-17-19-21-23-25-27-30-34 - meaning I have a 4t jump to my last gear, which is a bit too much. I looked at my existing 11-32 cassete (cogs: 11-12-13-14-16-18-20-22-25-28-32),
Is it currently too big of a jump as well?

I think I have 10spd SRAM cassettes where 3 largest cogs are riveted together, but I have never measured if the carrier dimensions are the same for both. If they are, it should be easy enough to mix and match.
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Old 09-08-20, 01:27 PM
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25% gradients on a 34-34?

Glenn
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Old 09-08-20, 01:45 PM
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Originally Posted by trailangel View Post
If you are climbing 25% grade you will be in the 34 cog on the rear all the time. Consider 11-36 cassette instead, if you can get it to work.
Indeed... just found a ZTTO 11-36 which I will consider. Thanks
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Old 09-08-20, 01:47 PM
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woodcraft
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The jump makes no difference when you are only going ~ 4 mph,

and 1:1 is not that extreme- mtn bikes go 1/3 lower.
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Old 09-08-20, 01:48 PM
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acsoaresbr
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Got it!
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Old 09-08-20, 01:52 PM
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Buy a single 34 cog and remove one of the smaller cogs you don't want and use the spacer from it. And you can go back to your normal one when you want.
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Old 09-08-20, 02:59 PM
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Originally Posted by acsoaresbr View Post
Hi there!

I will be facing climbs that are steeper than my legs would allow me to (over 25% gradients) and I was considering to use a 11-34 Ultegra cassete. I have a 11 speed Shimano Ultegra groupset, long cage rear derailleur, 34/50 crankset). However, I noticed the 11-34 cogs are 11-13-15-17-19-21-23-25-27-30-34 - meaning I have a 4t jump to my last gear, which is a bit too much. I looked at my existing 11-32 cassete (cogs: 11-12-13-14-16-18-20-22-25-28-32), and realized mixing them would be ideal. I could potentially end up with a 30-32-34 bigger cogs. However, the last cogs seem to be machined together! So, that is not an option... quite frustrating.

Is there any way to get a 11-speed Shimano compatible cassete that would look something like: 12-14-16-18-20-22-25-28-30-32-34?
Is there any company that build custom cassetes?

Thanks in advance!!
Since you already have a long-cage derailleur, and you want an extreme climbing cassette, you might consider installing an 11-40t. This will take your derailleur capacity from 39t to 45t, but a long cage should be able to handle it. You would end up with a ~23 gear-inch low gear, which should guarantee you can sit & spin up a 25% grade. The downside is you'll have a 5t change from your penultimate gear to your lowest gear, but it should feel like a comfortable change at only a 14% difference.
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Old 09-08-20, 04:46 PM
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Originally Posted by BoraxKid View Post
Since you already have a long-cage derailleur, and you want an extreme climbing cassette, you might consider installing an 11-40t. This will take your derailleur capacity from 39t to 45t, but a long cage should be able to handle it. You would end up with a ~23 gear-inch low gear, which should guarantee you can sit & spin up a 25% grade. The downside is you'll have a 5t change from your penultimate gear to your lowest gear, but it should feel like a comfortable change at only a 14% difference.
Funny stuff.
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Old 09-08-20, 05:02 PM
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Originally Posted by fietsbob View Post
Triple crank is your next buy ... Shimano Ultegra had a 130 -74 _ 50 -39- 30, 74bcd will take a 24t..
The last generations of both Ultegra and Tiagra triples had the granny chainring bolted to the middle chainring like the old TA cranks. The granny bolt circle was about 92 mm and a 30T chainring is the smallest that will fit.

Shimano's last "true" road triple was the 10-speed 105 FC-5703 that did indeed have 130/74 bolt circles but they have been out of production for several years and finding one is not easy. Shimano still makes "Trekking" triple cranks but they aren't available in the USA, only in Europe, and most European dealers won't ship Shimano or SRAM components to the US.
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Old 09-08-20, 05:05 PM
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I just did the calcs. An average sized person on an average bike would have to push about 365 watts to spin at 90 rpm up a 25% grade with a 34/40.

Edit: I mixed up MPH/KPH on the calculations. It's actually ~580 watts. I thought the first one seemed a little low, but they're both too big for me anyway, which must be why I struggle on 25% climbs

Last edited by kingston; 09-08-20 at 05:43 PM. Reason: Correct calculation error
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Old 09-08-20, 05:16 PM
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Originally Posted by tomato coupe View Post
Funny stuff.
huh? I gave advice on how OP might adjust their drivetrain to better suit their preferred riding style. Everything I said is technically valid. What are you trying to say with your comment?
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Old 09-08-20, 05:18 PM
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Originally Posted by kingston View Post
I just did the calcs. An average sized person on an average bike would have to push about 365 watts to spin at 90 rpm up a 25% grade with a 34/40.
Can you show your work? How much power would be needed to spin up a 25% grade at 65-70 rpm?
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Old 09-08-20, 05:38 PM
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Originally Posted by BoraxKid View Post
Can you show your work?
I cannot. I just used some online calculators. I also just realized that I mixed up MPH/KPH: It's actually ~580 watts

https://www.bikecalc.com/ to calculate speed at cadence by GI
Bike Calculator to calculate power by grade, speed and weight

Originally Posted by BoraxKid View Post
How much power would be needed to spin up a 25% grade at 65-70 rpm?
About 350
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Old 09-08-20, 05:50 PM
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Originally Posted by trailangel View Post
If you are climbing 25% grade you will be in the 34 cog on the rear all the time. Consider 11-36 cassette instead, if you can get it to work.
Word.

The idea that you're going to be in a 32t and save the 34t for a bailout on a 25% grade is just hooey. As is the idea that the 32t is the ideal gear for hills that are only 20% grade.
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Old 09-08-20, 05:54 PM
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Originally Posted by BoraxKid View Post
huh? I gave advice on how OP might adjust their drivetrain to better suit their preferred riding style. Everything I said is technically valid. What are you trying to say with your comment?
There aren't many cyclists who are going to "spin" their way up a 25% grade with that gearing.
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Old 09-08-20, 05:56 PM
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Originally Posted by tomato coupe View Post
There aren't many cyclists who are going to "spin" their way up a 25% grade with that gearing.
I'd like to see someone spin up 25% with a 34/34.

Glenn
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Old 09-08-20, 06:02 PM
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Originally Posted by GAtkins View Post
I'd like to see someone spin up 25% with a 34/34.

Glenn
You need about 7 W/kg at 80 RPM.
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Old 09-08-20, 06:07 PM
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Originally Posted by tomato coupe View Post
There aren't many cyclists who are going to "spin" their way up a 25% grade with that gearing.
How else do you do it then? No matter what gear you're using, you still have to spin the pedals in a circle to make the bike go. Otherwise, I guess you just admit defeat and walk?
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Old 09-08-20, 06:22 PM
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You can stand on it instead of spinning.
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