Different Gearing For Higher Grade Ride

Greetings, I’m looking to change the gearing on my 2022 SWorks SL7 Tarmac.

Stock, the bike came with a Dura Ace 12 speed 11-30t cassette, and a 52/36T chainrings.

The ride I’m looking to do has some 15-20% grade climbs, that are a bit longer in distance. Not punchy stuff.

I was thinking I could maybe just change my cassette out and leave my chainrings.

Looks like the next size Shimano Dura Ace 12 speed cassette would be 11/34.

Would the 11/34 cassette be compatible with my existing 52/36T chainrings?

If so would this be good gearing to tackle 15-20 grades? Also, not sure if my rear derailer would need to be adjusted.

I’m decent at some bicycle maintenance but gearing is next level for me.

Appreciate the input everyone.

Thanks

You will need a longer chain, otherwise you can damage your derailleur. You will also need to adjust the B screw. There are plenty of videos on YouTube.

Also, your derailleur has to be capable of that bigger cassette size (or you have to use an adapter linkage, like a goat link)

Okay, I have a second chain so I’m looking good there. But my rear derailleur, yeah not too sure if that’s compatible with the bigger cassette. I believe cassette change it’s only 1 size difference so I don’t know. 12 speed 11-30 then next 11-34, I think 11-32 is skipped not sure if that makes a difference.

Post a picture of your derailleur from the side (showing the pulley wheels) so we can see how long that pulley cage is.

Appreciate the help hughes, is this photo okay?

Reading here that Shimano for their new 12 speed system, only makes one derailleur, and it’s designed to work with all three cassettes sizes, up to the 34 tooth one I’m looking at.

So I think I’m looking good, should be okay with my chainrings?

https://www.trainerroad.com/forum/t/di2-12-speed-ultegra-8100-and-11-36-or-taller

check out this recent thread. for you though, you’ll get a huge improvement by just getting another set of chainrings as that improves your entire range of gears rather than just adding a single extra granny gear.

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Yes.

Nope.
I’d change cassette and chain rings for sure: if you want to ride 20 % grades you really need 1:1 gearing or better. For reference, when I ride some of these steep bits on a long climb at 220 W, my cadence drops to 55–60 rpm, and my lowest gear, 42:36 = 1.17, is a little easier than your lowest gear, 36:30 = 1.20.

Gearing is easy to understand actually. The best tool is Gear Calculator: as you can see, switching both, chain rings and cassette will give you 1.5 extra gears on the climbing end and you will lose half a gear at the top end.

Once you switch to speed you see that at the top end at 100 rpm the difference is 61.0 km/h and 58.6 km/h — if you can pedal at these speeds, which you only can in a sprint or downhill. IMHO this is completely irrelevant.

Compatible, yes, but definitely not ideal for climbing such steep grades.

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Appreciate your comments, Oreo.

Okay so if I’m switching out my 11-30 cassette for the 11-34, what’s the ideal chainring setup for 15-20 percent grades. I’m about 155 lbs and climb with about 185 watts for longer stuff.

Really appreciate everyones help, spent a lot of time studying this stuff, and it’s just not clicking. Also with the new 12 speed, I could not find many other discussions.

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You should change the cassette to the 11-34 and get 50/34 chain rings (aka compact chain rings). Like others have said, you might need a new chain, too, to accommodate the four extra teeth in the cassette.

For reference, I am slightly heavier than you (74–75 kg, about 160–165 lbs) but have more watts in my legs. Climbing at endurance power means 220–250 W for me.

Basically, I’d always err on the side of having more climbing gears — especially for steep stuff. For the life of me, I really don’t understand why bike manufacturers still sell bikes that are way overgeared for the vast majority of the population. That’s especially a problem when you are on Shimano.

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Thank you very much Oreo. You saved me a great deal of time and headache. But I will continue to study this stuff. That’s some nice power, I do good on some of the punchy stuff, but have not had much experience with much past 12-15 percent grade and even more endurance type climbing.

One last thing, I imagine I just order the 50 tooth chainring and 34 tooth chainring, and that’s goes onto my preexisting crankset? Or do I have to buy an entire new crankset? Thank you again.

Your crankset should fit compatible shimano 50/34 chainrings, it often comes as a set. If you climb regularly, i would seriously look into a second set of crankset, maybe a cheap aliexpress 46/30 or grx 48/31. Its alot more comfortable imo

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According to Shimano your current crank is fully compatible. You only need to change chain rings.

BTW, you are one lucky man, a fully decked out SL7 is one nice bike!

Okay perfect, one less thing. Cassette, and two chain rings. Let’s see if I can make it happen for this weekend, haha. Tour of the Catskills here in New York. Also looking at Green MTN Stage Race in VT next month.

And thank you! Yes, very lucky, it’s a killer of a bike. Much different than my 10 year old Bianchi that it replaced. Though I still enjoy taking my Bianchi out, much smoother ride. The SL7 is very stiff and fast.

Appreciate your time, I can finally sleep on this matter now. Been going back and forth for a week now lol.

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I just got a wolf tooth’s roadlink so my rear mech would be further away from a larger cassette.
this allowed me to go from 11-28 to 11-32 on my 1st edition red eTap.
You may not need that gadget on this bike but it’s a useful gadget to know about.

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If you’re going steep, get all the gear you can to keep your cardio out of the red and your legs in one piece. Im not a good climber; I tried San Diego 18% gravel climbs on 42x42 gravel gearing and it sucked. I tried similar climbs on 32x51 MTB gearing and it was way less fatiguing.

I’d put a 34t little cog in there even if it doesn’t shift well. Maybe just get a separate cheap crank and 32t 1x chainring. That’d give you 12% more leverage in front. Maybe another 2% if you upsize the crank arms.

In back, I’d get a 34t cassette. You can use it as a trainer cassette if you don’t want to just run the 11sp one.

If you’ve got a short friend with 650b wheels in the right size with tires, that’d net you 6% more leverage with 28c tire.

That gets you 20% lower gearing. Beyond that, this might be an excuse to get a gravel/endurance bike so you can put a big cassette on it as well as put more rubber on the ground, which might be needed at these inclines.

Looks like I’m seeing a lot of climbing bike setups with 11-30 cassette and 50/34 chainrings. 11-34 cassette with 50/34 chainrings, maybe a bit overkill?

Aside from gearing, at the steepest parts, you can

  • reduce cadence to limit going too far in the red
  • if the road is wide enough, you’re far from others and it’s safe to do so, move in zig-zags. A bit like switchbacks, this reduces the actual gradient.

I would go all in on and do the 11/34 and 50/34. 15-20% grades are no joke. Especially sustained, so you can’t carry momentum or just burn a match.

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