Converting compact double to 1x11

[vickster]

I’m changing my Sabbath to a SRAM 1x11 gravel set up. Currently a compact double 50-34 and 11-32 on back and in the process of acquiring chainset and cassette.
Would a 42 front and 11-42 rear give me a similar top and bottom or do I need something else?
I’m rather clueless about such things!
Thanks for any help!

 

[Hacienda71]

A 50:11 is a higher ratio than a 42:11 so it will be a compromise.

 

[vickster]

A 50:11 is a higher ratio than a 42:11 so it will be a compromise.

Can you explain?
I can also get a 50T chainring if I go rival (I have Apex shifters although I’m not too bothered about matchy match, but I’d need a Rival rear mech, just ups the cost a bit). Much of my riding is pretty flat, I rarely use the little ring at present (and I have other bikes for hilly terrain, the Condor 🦄 will be getting the existing set up to replace Ultegra triple)

 

[Ajax Bay]

https://www.gear-calculator.com/?GR...25,28,32&UF=2215&TF=90&SL=2.6&UN=KMH&DV=teeth
https://www.gear-calculator.com/?GR...32,37,42&UF=2215&TF=90&SL=2.6&UN=KMH&DV=teeth
And you can have a play! The suggested 42/42 will 'obviously' give you a slightly shorter lowest gear (than the current 34/32).

 

[vickster]

https://www.gear-calculator.com/?GR...25,28,32&UF=2215&TF=90&SL=2.6&UN=KMH&DV=teeth
https://www.gear-calculator.com/?GR...32,37,42&UF=2215&TF=90&SL=2.6&UN=KMH&DV=teeth
And you can have a play! The suggested 42/42 will 'obviously' give you a slightly shorter lowest gear (than the current 34/32).

Which means what in laywoman terms?

 

[Ajax Bay]

Very slightly easier on a steep hill with the 42/42 - 6% difference.
The proposed 42/11 will mean that you'll spin out a bit earlier on the downhills: if your comfortable cadence limit at speed is 100rpm then 50kph max before freewheeling (as opposed to ~60kph with your current compact).
Worth considering crank length choice when you buy eg if less than 170cm: 165mm.
Uselessness is a false g0d. Claiming it will mean you are missing all the fun of gear lengths, and the like.

 

[vickster]

My cadence rarely goes above 80 and I don’t go above 30mph, if so I’d just be freewheeling
All my bikes have a 172.5mm crank so I’ll stick with that

 

[ColinJ]

I’m changing my Sabbath to a SRAM 1x11 gravel set up. Currently a compact double 50-34 and 11-32 on back and in the process of acquiring chainset and cassette.
Would a 42 front and 11-42 rear give me a similar top and bottom or do I need something else?
I’m rather clueless about such things!
Thanks for any help!

I have exactly that gearing on the bike I keep at my sister's house in Devon.

As mentioned above, the low gear is a little bit lower than your current lowest gear so that can only help.

The high gear is still pretty high. It would not be high enough for racing but I don't need higher, and I suspect that you probably don't either! I am not fit enough to spin out on 42/11*** except on significant downhills and on those I just freewheel.


*** I can still pedal that gear to 50+ kph/31+ mph (cadence around 100 rpm)

 

[cougie uk]

I’m changing my Sabbath to a SRAM 1x11 gravel set up. Currently a compact double 50-34 and 11-32 on back and in the process of acquiring chainset and cassette.
Would a 42 front and 11-42 rear give me a similar top and bottom or do I need something else?
I’m rather clueless about such things!
Thanks for any help!

Hang on - you've been here 12 years and can't calculate gears yet ?

 

[MichaelW2]

Most UK club riders compare gears using "gear inches". A 30 gear inch is the same on any bike no matter what combination of chainring, rear sprocket and wheel size you select to arrive at that particular gear. Most gear calculators have an option for Gear Inches.
If you work out your current useful gears in Gear Inches you will see what you need.

 

[Jameshow]

You'll gain at the bottom end and loose at the top end, not a bad compromise tbh.

 

[vickster]

Hang on - you've been here 12 years and can't calculate gears yet ?

Indeed, as I ultimately have no interest in such things and pretty much have the same on all my 2x bikes which works for me, however 1x is different hence my question

 

[vickster]

Most UK club riders compare gears using "gear inches". A 30 gear inch is the same on any bike no matter what combination of chainring, rear sprocket and wheel size you select to arrive at that particular gear. Most gear calculators have an option for Gear Inches.
If you work out your current useful gears in Gear Inches you will see what you need.

I don’t ride in a club, never have, never will

 

[Jenkins]

Have a look around for a gear calculator that gives an output in figures such as gear inches and input the details of what you run at the moment. Make a note of what the figures are for the gears that you use most with the current set-up. Then input the details of the set-up that you are thinking of running and see whether the output figures match up (or come close to) with those for the gears you use most at the moment. If they don't, try inputting the details of another set-up to see if you can find something that does.

The one I used was this one as it allowed a side by side comparison, but seems to have gone missing for the moment.

 

[vickster]

Another question…whats the difference between a chain marketed as 1x 11 eg https://www.biketart.com/products/sram-x1-11-speed-chain

and a normal 11 speed chain eg https://www.tweekscycles.com/uk/sram-pc-1130-11-speed-chain-srmchpx113/

can I use the latter with a 1x set up? As I have one in the spares box