Look at the ratio between the chainring and cog.
36/30 = 1.20
34/26 = 1.31
1.31 is higher than 1.20, so the low gear on the TT bike is higher than the low gear on the road bike. By how much? 1.31/1.20 is 1.09, so the TT bike's low gear is 9% higher.

You can also do algebra to figure out what cog size you'd need on the TT bike in order to match the gear ratio on the road bike.
34/X = 1.2
34 = 1.2 * X
X = 34 / 1.2 = 28.33
So, the 11-28 cassette would be pretty close to giving the TT bike the same low gear as the road bike. It would technically still be slightly higher, but it would be close.

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Note that this all assumes that the diameter of the inflated wheel is the same in both cases.
If two bikes have 700c wheels, but one has 23mm tires and the other has 28mm tires, this could result in an inflated wheel diameter of something like 675mm for the first bike and 685mm for the second bike.
685/675 = 1.015.
So, "the same gear ratio" would be 1.5% higher on the second bike than on the first bike, because of the second bike's larger rear wheel.


Depends on your strength, pedaling style, and the terrain you're riding. Are you bottoming out your gearing frequently on the TT bike right now?

So, I need some clarification.

when you say "Higher" are you referring to an easier gear or stronger gear?

I am looking for a way to get a nice easy gearing for climbing on hills via TT bike. I KNOW THE the 11-30 would be easier than the road bike since I have the 50x34. Would the 26 be easier, or the same or more challenging?. Hope that helps.

Stronger.

A higher gear is more gear inches.

Simple math.

To put it another way, the TT bike with the 34 / 26 will be harder to pedal up a hill (ie need more muscular force per rev) than the road bike with it's 36 / 30.

As per the other post it assumes the same diameter of tyre.
It also assumes the same crank arm length (if the arms are different lengths you get a different leverage).

Two of my favorite sites. I use both to help inform cassette decisions like this regularly.

http://bikecalc-staging.herokuapp.com/speed_at_cadence


https://www.gribble.org/cycling/power_v_speed.html

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Dr. Alex Harrison | Founder & CEO | Sport Physiology & Performance PhD
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Your tri setup will be faster for the same power. So a hair different on the gearing maybe. But, IMO, you have it backwards. If I had to have a bike to have the 50/34 on, it would be the road bike. Not the tri bike. The tri bike is already a whole gear faster due to the aero position. Especially if the road bike ever sees some mixed gravel use with a little mean uphill or two.

Just me. You do you. You say you like the roadie gearing, so I see no reason to not make it match on both cassette and chainrings.

I assume it is a triathlon setup. For TT, I know of stories of folks bashing out stellar fast times on a compact 50/34 in a 50/12.......but where I live we have hills where on my bike I get up to some good speed downhill. I feel more stable and make faster times being able to spin at my normal cadence and producing some power downhill. I could never do that on a 50/11.

50/11 at 100rpm is 35.XX mph on a 25mm tire. If there's an extended downhill or downwind, you'll be at a ripping cadence for some time in an inefficient rear cog bleeding watts.

So.........I say 52/36 and 11/30 for your tri bike. But keep the 11/26 if it's a bit flatter. No reason to not keep it handy.

The tri bike came with 165 50x34 cranks. The road bike came as 52x36 and 175. I don't want to buy another crankset for the road as I have a powermeter on it.

I'd just rather change a cassette if that will solve my problem.

No need to buy any cranksets.

Just change chainrings.

Thanks, never thought of that.

I need to ake a course in basic bike mechanics!

My favourite for this:
http://ritzelrechner.de/

The OP's setups compared:
http://ritzelrechner.de/?GR=DERS&KB=36,52&RZ=11,12,13,14,15,17,19,21,24,27,30&UF=2135&TF=90&SL=2.6&UN=KMH&DV=teeth&GR2=DERS&KB2=34,50&RZ2=11,12,13,14,15,16,17,19,21,23,26&UF2=2135


As HT said, an 11-28 gives almost exactly the same lowest gear as the other bike, but you do lose the 16 in the middle if that matters.

Nice. Great page.

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Dr. Alex Harrison | Founder & CEO | Sport Physiology & Performance PhD
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📱 Check out our app → Saturday: Pro Fuel & Hydration, a performance nutrition coach in your pocket.
Join us on YouTube → Saturday Morning | Ride & Run Faster and our growing Saturday User Hub

Yea I got a new bike last year and it came with the 50/34 setup. I hated it and a few months later swapped to 52/36 chainrings. Easy to do now with the 4 bolt cranksets So much happier.

My biggest issue is wanting the 34/28 on the low end but the 50/11 not being enough . I am toying with the idea of a Wickwerx 53-34 front set of rings and see how that goes.

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Banger

The Ultegra shadow derailleurs (RX800) with the clutch take a pretty big cassette. I think they fit a 34 tooth. Then the world would be your oyster on having something more than 50/11 but as easy or easier than 34/34.

All Shimano mid-cage road derailleurs spec at least a 34T cog nowadays, and they'll usually handle significantly more. But the 11-34 cassette is more widely-spaced than a lot of people want on a road or TT bike.

I was talking about the front being 53 and 34 tooth chainrings. From what I have seen WickWerx is the only one stating they can make the 19 tooth jump work in the front. If there is something else out there it would be great to find.

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Banger