cccorlew

I'm posting this here because at 53 I like a lower gear than the 20-year-olds.
Gearing has got me baffled.
I currently ride a old Cannondale. It came with 52-42 chainrings and a 13-24 freewheel.
It was way to high for, so I swapped the 42 for a 39 and added and changed just the 24 rear for 26.
OK?
Now I'm looking at a bike that has a Shimano Ultegra 50-36 and an 10-speed 11-23 rear cassette. I'd like a gear at least as low as what I have now.

Here are my questions:
Can I just swap out the one 23 sprocket for a 25 or 26, just to get one real low gear? It that a possible thing for a normal person?
Is it possible to buy different size cogs?
What's up with the 50-39? Is that a good idea? It's a far cry from the 52-42 I grew up with.

Perhaps there is an online guide for his stuff somewhere that I can't find. My google-fu fails me. I'm not even sure if this belongs in road bikes or tech instead of here

fifty5

Maybe some usefull info here:
https://sheldonbrown.com/gearing/index.html

stapfam

That 42 chain ring does not offer a low enough gear for me. The 36 would. I run 8 speed and have 12/26 on the rear but your 11/23 should be possible to change to give a lower gear.

I live in a very hilly area and Have a triple 52/42/30 and the 12/26. This is just low enough for the steepest so a 36compact should do you fine- Providing you can get lower than 23 on the rear. Or failing that- Look for a bike with a triple as this will give low gears.

OBXBIKR

Ultegra cassettes offer a number of options, the largest has a big cog of 27 teeth. All cassettes in the same family cost the same. Your LBS should swap it out for you when you purchase the bike at no extra cost. If you want even more reasonable gearing, you can swap out the Ultegra cassette for a Shimano MTB cassett, XT is roughly equivlent to Ultegra. The LBS might want to charge extra for this, but you can get a 34 tooth low gear this way, and it works fine with Ultegra shifters an RDR.

Blackberry

If you want wide-ranging gearing with a nice, low granny, consider a triple chainring up front and the "Harris Century Special" rear cluster, (designed by Sheldon Brown). It's available here (scroll down) and works with all real derailieurs: https://sheldonbrown.com/harris/k7.html

That's why I've done, and it's been a lifesaver on steep climbs.

BlazingPedals

If a 39/26 combination represents the tallest you want for a low gear, then with a 36T chainring you will want at least a 24T cassette gear. I don't know what cassettes offer that gear. Although taking cassettes apart & mixing your own stack is possible, it can be a pain because the largest cogs are usually riveted to a carrier

sauerwald

One thing to be concerned about if you just go to a wider range cassette is that the combination of the range on the front (50-36 Compact) and a wide range rear - perhaps a 13-26 or something may require a longer cage on the rder than what is on the bike.

I am not sure what is available, but here are a few options - if they can change the chainrings to a 44-36, and keep the 11-23 rear cassette, then that will give you about the same gearing range as you have on your current bike. As another old guy, I also tend to use the larger cassettes - I use the Shimano 13-26 because I never need the really high gears that come from an 11 tooth sprocket, and the larger cogs last longer.

On your current bike do you ever use the 52-13 combination? - If not then it may be as simple as just having them change the cassette to a 13-26 giving you a few more links of chain and be done with it. Your top gear then would be 50-13, which is almost as high as you currently have, and the lowest gear, at 36-26 is about 8% lower than the lowest that you currently have.

rmac

I don't think MTB cassettes come in 10sp. Also, I didn't think Ultegra rear derailleurs could handle 34 teeth.

stapfam

Right on both points. I have seen a 10spd MTB but only one and I don't know where the cassette came from.

My lowest gear- with a triple is 30/26. This will take our Steepest long hills but I am planning on going to Mt. Ventoux on holiday. It is not as steep as my hills but a lot longer. I am going to get a Rear cassette with a 28t on it just to make things a bit easier but even this may involve a change of rear derailler. Luckily- I have plenty of Long reach deraillers in my tool box- slightly used but servicable.

Still think it worth looking for a triple front chainset as If you are worried about hills- It does help mentally.

Edit====BB's link to Sheldon shows a 10spd MTB cassette to it is possible to go silly low on 10spd.

https://sheldonbrown.com/harris/k7.html

Cassave

Calculating gears is simple;

Divide the chainring by the rear cog, your old gearing is 39/26 = 1.5 (a simple ratio that can be used as it is to compare to other chainring/cog combinations).

Bicycle gearing is usually expressed in "gear inches" meaning a gear that has equivalence to the front wheel of an old Ordinary (high wheel) bike. To get this multiply the gear ratio by the diameter of your rear wheel (in inches). For a 700C road bike using 26.75" is plenty close so
26.75 X 1.5 = 40.12". Just like riding a Penny Farthing with a 40" front wheel.

A third and I think really useful number is commonly called "development" and it expresses how far the bike will
travel with one full rotation of the pedals.
To find development just multiply the "gear inch" number by PI (3.14 is close enough).
So, with your old gearing of 39/26 you'll travel 126" (10 feet 6 inches) with one turn of the pedals.

The low gearing with the Ultegra compact crank would be 36/23 = 1.56 (a little higher)
gear inch value is 1.56 x 26.75 = 41.9"
and developement is 41.9" x 3.14 = 131" ( 10 feet 11 1/2 inches)

You should be able to get the LBS to mount a 12-25 cassette which would give you 38.55" low.

cccorlew

This is great stuff. Thanks to all who helped. I think the 12-25 idea is perfect, and I'd not have thought of it. I never need my 52x13 now, so I sure wouldn't miss that high gear.

oilman_15106

There are a ton of discussions on this subject on the road biking fourm. I find the 50/34 front and 12/25 a perfect compromise.

Dchiefransom

With the 42 up front and 24 in the back, getting a 36 up front it looks like you'd need a 21 in back for the same ratio. Why not switch to a 12-27 10 speed cassette in the back and practice on Mt Diablo?

cyclezen

since you said "bike I'm looking at", I won't go into big changes from what the bike has.
if you;re not sure about the 50x36 crankset, do a search on road forum for 'compact crankset' - you'll get all the info you could want.
Personally I love my compact setups, and I also love the triples I have. The compact is a bit 'simpler' in that knowing the exact gearing isn't that important. Its enough to know that as the road gets steeper, you 1st run through the gears using the large ring, then drop back on the cassette onto the 3rd from highest cog (small cog) and work your way through using the small ring. Keeping in mind that crosschaining is always a consideration.
Only thing I would do is swap the cassette for 13-25. Personally, I would never use a 12 in normal riding forget the 11. The only 12 I own gets used only for crit racing. Additionally its not so much about the 12 if the next gear was a 14, but usually the cassettes go single steps until you hit 16, then they make bigger jumps between cogs on the subsequent ones. For me, that leaves big holes in frequently used gearing. I spend most of my riding time, on flats, in the 50 x 15-16-17-19 and the same rear cogs with the 34 on most moderate climbs. A 12 high end gives away too many of these more important mid gears.
So for me the 9 spd cassette range that really works is 13,14,15,16,17,19, 21,23,25 and on 10 spds I add a 18 between the 17 & 19 (of course...)
The 13-25 9spd cassette is a std/stock config available in Shimano 105 or Ultegra cassettes. The 10 spd 13-25 is available stock in Ultegra.