SoSmellyAir

I had a cassette made from combining two donor cassettes, but I had trouble downshifting at the transition from one donor cassette to the other.

Bike Forums - View Single Post - Custom 12-28 cassette

PeteHski

It just gives you a wide gear range without resorting to a triple. Why would anyone run their drivetrain in a 34/10 gear? Maybe you just associate a “big plate” on the back with a slow rider, but it isn’t the case.

Racing Dan

At some point an additional small, very light weight, chain ring in the front makes a lot more sense than one or two more dinner plate size cogs in the back. Especially if you didn't already went to 1x and ditched the front DR all together.

Carbonfiberboy 

Well, that's what triples are. I like a 24 or 26 granny ring so I can have my rear cogs even closer together.

PeteHski

So at what point is that then? I’m quite happy with a compact double on my road bike, which is probably why they are so common. I used to hate triples when they were standard on MTBs. Much prefer 1x gearing off-road.

terrymorse 

I don't see very many low-cadence grinders these days. I do see riders using 34/34 on climbs, but they're not spinning high cadences. Maybe 80 rpm or so. One thing I have noticed: I never see them stand (not a good thing--alternating between seated and standing is better).

Personally, my legs are still managing okay with a 34/28 lowest gear. That gear rarely gets used--it's the "bail out" gear when I'm tired, or when the grade is double-digit for more than just a short section.

Pushing a bigger gear isn't the worst thing in the world. It will make your muscles stronger, and it's more aerobically efficient than spinning. FWIW, my best climbing times usually happen when I'm pushing a bigger gear.

My preferred climbing cadence is 65-75 rpm, and my four lowest gears give me several comfortable options in the sub-10 mph speed range:


from bikecalc.com

WorldIRC

I live right on a part of the Niagara Escarpment called the Oak Ridges moraine. We grew up knowing what an escarpment was

vane171

I made that post hinting at triple on the front to 'enrich' the discussion but I believe nobody enjoys shifting the front, besides it being disruptive on pace, most if not all chain drops are on account of that.

HTupolev

I'm not sure how that's relevant, considering that people mostly aren't recommending 1x. And, a well-designed triple can in some cases reduce the amount of front shifting that a rider is doing compared with a double, in addition to reducing the pedaling disruption of shifts by permitting tighter front ratios.

The issue with recommending a triple isn't that they don't have merit in the context of this thread, it's that there aren't a lot of current options for them with modern drivetrains.

SoSmellyAir

I also had to look up "moraine." I should have taken a geography elective.

PeteHski

I have a 34/34 and I'm definitely in it once the gradient goes above 10% unless it's a very short climb that I'm going to power over. I'm usually forced down to 70 rpm or less at that point too. I'm a reasonable climber, but at around 80 kg I'm certainly not going to win any KOMs. I agree on alternating between standing and sitting, but I think that's just a personal preference really. It's not something I think about while riding.

Now I'm interested that you say your preferred climbing cadence is 65-75 rpm. So what is your preferred cadence on the flat at the same power output? I'm assuming it's somewhat higher and in which case why would that be the case? I keep meaning to compare my climbing times on Zwift using ERG vs slope mode to see if I'm actually faster or slower at a higher climbing cadence than my road gearing would actually allow. I'm not talking about spinning as such, just a normal cadence around 80-90 rpm vs a forced 65-75 rpm due to running out of gears. I get the feeling it would be a bit faster overall, especially on a longer climb where muscle fatigue would be a factor at low cadence.

SoSmellyAir

I am trying to learn how to stand and climb. My lowest gear ratio is 34 x 25, and when I try to stand, it feels like I should shift to a small cog, i.e., 34 x 23 or 21; am I doing something wrong?

colnago62

I believe the reason cadence is different on climbs and flats given the same power output is the effect gravity has in those two scenarios. The higher the effect of gravity, the less forward momentum.

colnago62

Most people shift to smaller cogs when climbing vs. sitting.

aliasfox

Most definitely. I can spin up a short 8% grade at 90rpm in 50 x 13, provided there was a long -8% grade right before it.

terrymorse 

It's totally normal to shift to a higher gear when standing. It should feel like a walking cadence.

aliasfox

Or find a steeper hill!

SoSmellyAir

colnago62 terrymorse Thank you, both. Cycling was much more simpler when I was a teenager, even though I only had 10 speeds, but probably a better power to weight ratio than now, most likely due to a vast increase in the latter factor.

terrymorse 

Yes, my preferred flat riding cadence is higher, about 85-95. Why the difference? No idea.

I also find it harder to maintain the same power on the flat as on uphills. It's not an aerobic limit thing, the legs just don't want to push as hard. Why? Also, no idea.

OK, maybe one idea: I climb often, and my body has gotten accustomed to putting out power when climbing. Body's not as accustomed to pedaling on the flat, so it's not as powerful there.

genejockey 

That's the great thing about modern shifting - you can shift two click up when you stand, and back two clicks when you sit back down.

genejockey 

I find that even if I have a gear that lets me climb at 90rpm, I prefer to do it in the low 80s. I have found myself shifting to a higher gear on places like Old La Honda, running 36x30 instead of 36x34 most of the way, but saving the 34 for the toughest bits in the last mile.

On the flats 95-105 feels right.

PeteHski

I find much the same. I think I am just used to climbing at a lower cadence simply because of the limitation of road gearing, especially before compact chainsets became the norm. But on a mountain bike I will tend to use a more normal 80-90 rpm up climbs because the gearing allows it.
I found that a power meter really helped me to pace better on the flat.

Carbonfiberboy 

In a way. Formally, it's known as crank inertial load: https://pubmed.ncbi.nlm.nih.gov/11784546/
But yeah, it's about gravity.

terrymorse 

Same here, it's when I recently got a power meter that I realized my power was much lower on the flat than when climbing. Even though the perceived effort felt about the same.

ZHVelo

This is entirely dependent on gradient and the watts you can push. Yea sure pros can get away with 36-28, because the watts required to push RPM X at gradient Y is doable for them.