el forestero

I frequently climb long, steep hills and am trying to decide whether it's worth buying an 11-34T cassette for a bike that has an 11-30T cassette and a 34T small chainring. When riding up continuous grades of 10% to 20% for 40 to 120 minutes at a time, how noticeable would the difference be between running on 30T and 34T cassette cogs? Is each pedal stroke likely to feel significantly easier on 34T or does this feel like a subtle change?

obrentharris 

Not at all subtle, at least for me. About a 13% lower gear.
Brent

znomit

For that long a climb a 34 will be a significant benefit.

downtube42

10% is one thing, 20% is a whole different matter.

34.

terrymorse 

10-20%? For 40-120 minutes?!

Where are such R.O.U.G.s (Roads of Unusual Grade)? I don't think they exist.

Racing Dan

I think lots of such claims are simply highly inaccurate guesstimations. Imo, riding a 5% hill intuitively feels like a lot more. Riding a true 20% incline feels like a wall and will drop your speed to a few mph even with a solid effort.

GhostRider62

Mount Washington hill climb in 2 weeks is darned steep at 12% average. Mortirolo averages 11%. I can't recall any climb in the Alps exceeding 14% and most average under 10%, at least from memory. The climbs in Japan must be brutal.

The increased gear ratio will slightly (13%) increase your cadence at the same power. A 75Kg rider making 240 watts on a 10% grade will be traveling about 6 mph or 10 km/h. Double the gradient and half the speeds. At 3 mph, the 34 cog will take your cadence from around 35 to 40 rpm. So, that 34 cog won't help much on the 20% grade. All else equal, in the 10% grade, it would mean going from 70 rpm in the 30 cog to 80 rpm in the 34 cog, approximately.

I don't see a 34 helping much. You need a triple with a 24 up front and the 34 in the back, giving you a mid 50 cadence on a 20% grade. I am assuming a normal, fit cyclist. 75 Kg and 240 watts threshold. YMMV

https://www.tinmountain.org/mt-washi...lclimb-mwarbh/

shelbyfv

If climbing is difficult with the 11-30, try the 11-34 if your derailleur can handle it. Cassettes are consumables. I also suggest you plot your route on RWGPS for a more accurate estimation of the grade, you may be encouraged.

el forestero

Thanks for the helpful replies, all.

I guess those grades do sound kinda crazy. I live in a pretty mountainous area, with Mt Fuji and Mikuni Pass, the steepest segment of this year's Olympic men's road race, very close by.

One of my favorite roads up Mt Fuji, the Azami Line, is about 10% average grade, with some sections signposted between 12% and 20%: https://pjammcycling.com/climb/520.M...Line-Bike-Ride

Mikuni Pass is also about 10% average grade, with some sections signposted 12 to 18%, although Japanese government sources say some part of the road exceeds 20% (https://www.yamanashi-kankou.jp/zenr...ourse/007.html). It was entertaining to watch the Olympic men's race's leaders ride up that road in little more than half my best time. At least I'm beating Google Maps' estimate by a wide margin.


Mikuni Pass climb



I believe this is about where Tratnik began his slide from 1st position to ultimately finishing 67th.

shelbyfv

I'd be scared to ride down that, especially with those circular things in the pavement.

Sy Reene

I think you yourself are in the best position to answer this. If you've been doing these climbs, at what cadence are you pedaling with the 30T setup? Everyone is different, but typically it wouldn't be ideal to be lower than 70rpm. Your proposed gear addition would net you about a 10rpm increase at those ranges.

SSRI

Go BIG - never hurt to have a bail out gear or 2

40 !!

woodcraft

Maybe not each pedal stroke feels easier,

but a substantial difference to the overall effort to have a better cadence on the steepest bits.

xroadcharlie

A 34T cog is about 12% easier to peddle then a 30T. For short steep climbs it helps, Sometimes we can just hunker down and go, Knowing we get to rest in a few minutes. But for long climbs with no rest in sight, it makes a much greater difference.

I don't know why, But when climbing the short challenging hills in my area I feel much better at a lower cadence (60 rpm) then my normal 75 rpm for cruising. I have never ridden very far on hills, But it makes sense to me to try to maintain our normal cadence and power on long hilly rides.

gregf83 

I would definitely put the 34 on. Made a trip to Girona a couple years ago and didn't think we'd have steep hills so only had a 25 on the back. Ended up climbing some reasonably long 12% hills. For me at least it's much tougher to ride close to threshold when my cadence is at 50. I think you should gear so you can ride the hills with a cadence around 90 RPM.

PeteHski

I would go for the 34:34 low gear for any prolonged climbing. It helps to keep your cadence up and can make the difference between climbing comfortably at sweetspot or being forced to go over threshold on the steeper gradients. The longer the climb, or the more tired you are, the more benefit it is. I did a 9 hour endurance event last month with 4000 m of brutal climbing at up to 25% gradient and I was absolutely glad of a 34T front and rear, just to keep moving! But even on the easier slopes, often it is just more efficient to spin a higher cadence. It's very rare that you find yourself spinning out above a 5% gradient and definitely not once you approach 10%. Note that 2nd gear on an 11-34T cassette is 30T. So you would have both gear options when climbing. For me the slight downside of larger gear spacing on the 11-34T cassette is far outweighed by having a lower climbing gear.

SoSmellyAir

Wow! I am surprised no one has suggested an SRAM 11-36 cassette yet.

Seattle Forrest

The road to the Hex Mountain trail is a couple miles at 18%. And dirt. Gated, so covered to cars, but you can bike it.

urbanknight

Depends on how slow the 10-20% grade makes you go

GhostRider62

Looking at the Azami Line up Mt Fuji, there is a 1 mile stretch at around the 4 mile mark that averages 14%. That is hard but it does not require a triple. The 34 rear cog would help and is probably sufficient. Probably more important than gearing is the strategy leading up to that pitch

Kapusta

30 to 34 will be noticeable.

With your 30t cog, do you ever find yourself pushing that right hand shifter, hoping maybe there was just one more lower gear that you forgot about?

The 34t cog is the gear you were looking for.

jrobe

There is no such thing as gears that are too low. I love to climb with as high of a cadence as possible.

hose

I'd also purchase a motorcycle

Kabuto

What chainring are you using? Of course everyone has different needs and fitness, but I ride in the same areas as you and find that a 50/34 chainring combined with an 11-30 cassette is sufficient for me.

I intentionally replaced my Domane's 11-34 cassette with an 11-30 cassette because, combined with the 50/34 compact chainring, not having the 34T cog on the 11-30 cassette bothered me less than the big jumps between the higher gears on the 11-34 cassettte (11-13-15-17-19-21-23-25-27-30-34T vs 11-12-13-14-15-17-19-21-24-27-30T). I have a very low mileage (about 200km max.) CS-HG700-11 105 series 11-34 cassette for cheap if you're interested.

FYI if you do swap out your cassette make sure your RD can handle the 34T cog first. You'll also likely need a longer chain.

Edit: just saw from your profile that you lead bike tours in Japan so I'm guessing you know a thing or two about bike maintenance and repairs. I'm kinda surprised you're asking the question in the first place tbh. Dude, just try it already, and claim the parts as a business expense

Cyclist0108

At the moment I have a HG 11-36 11-speed SRAM cassette on my bike with a 46/30T crank, and I am not ashamed to use the lowest gear on >15%.

My rear derailleur is a Shimano Ultegra Di2 officially rated for 11-32T. The b-screw is your friend.

Off-road, where I can't stand up without spinning out, it is essential.