Gravel Bike Gear Ratio

[RobertWhitehead]

Hi Ya'll (Place US accent here) 

I need your inputs / help to make up my mind: 

I am building a very sweet gravel bike which I will build with a hybrid of mtb and gravel parts but the one thing that I'm unsure about is, the chain ring size and or if I need to go 2x. 

I want to go hydraulic STI's (11 speed) with a mtb rear mech and cassette (11/50T or 11/46T) and then a monster of a ring in the front, something like a 50T to 53T. If I go 2x I can go smaller at the rear but then I have another derailleur and I like the clean look. Please give me your opinion

[Bub Marley]

The larger you going up front, the larger you gonna need at the back.

 

I personally think a 50 is overkill but the new trend these days seems to be efficiency. Personally, I’d rather go with a 46 front ring with 11/46 cassette and make more use of all my gears. Im not sure how much watts you actually lose by nit having your chainline dead centre but i cant imagine its much. Unless you are racing at the top end of the field where you need that power on the descents, then I wouldnt  go that high for a gravel bike.

[guidodg]

46T up front makes way more sense...and a 50T may not even fit on most frames

[Mongoose!]

40 minutes ago, Bub Marley said:

The larger you going up front, the larger you gonna need at the back.

Together with a looong chain... 

[SSCC]

Is the reason for the 50 chainring because you are using this as a road and gravel bike? 

[Prince Albert Cycles]

1 hour ago, RobertWhitehead said:

Hi Ya'll (Place US accent here) 

I need your inputs / help to make up my mind: 

I am building a very sweet gravel bike which I will build with a hybrid of mtb and gravel parts but the one thing that I'm unsure about is, the chain ring size and or if I need to go 2x. 

I want to go hydraulic STI's (11 speed) with a mtb rear mech and cassette (11/50T or 11/46T) and then a monster of a ring in the front, something like a 50T to 53T. If I go 2x I can go smaller at the rear but then I have another derailleur and I like the clean look. Please give me your opinion

You’ll get 50 responses and 50 opinions.  So many variables.  Where are you going to ride , flat or hilly or mountain passes. How fit/strong are you ?  That will or rather should determine your choice. My personal experience is 1 x11 on my full sus and 2 x10 on my gravel bike running 46/30 upfront. I just love the close ratios on the 2 x .  And chains and cassettes on 10 speed way way cheaper than 12 speed.

Enjoy the build and we want to see the photos 

[dave303e]

My suggestion would always be to see if you can get an AXS shifter. Then you can ride a bit and adjust the front chainring as and when you need it. The AXS gives you the time and distance spent in each gear in your drivetrain allowing you to make data based decisions. Soon you will understand what you need for certain situations...

 

For example my 34t chainring needs to be changed for a 36t for shorter rides in and around our area. As below you can see I don't touch granny gear.

This was 125km gravel ride on mtb from home so fairly flat.

But when it gets a bit more elevation gain and bigger distance(250km) then the 34t is perfect as below:

[Baracuda]

As noted above, horses for courses, but my 2 cents:

I have Shimano 2x11, with 11-36 cassette and 50-34 crankset. Great for almost everything, can stay with the roadies around Cape Town, great on open Karoo Roads, great on any paved mountain pass, but once the gradient gets above 12-13%, e.g. the last 2km of the Swartberg Pass from the south (15%), you really battle.

What I have is great for 99% of our gravel roads and my Shimano 2x11 is rock solid, lasts for ages and is not expensive, but if you want to ride steep jeep track (mtb stuff), then one needs MTB type gearing.

 

[cadenceblur]

I am running a 42 up front with an 11 - 42 at the back, bike can only take a 42 (mtb converted to gravel) It has served me well on the road with other roadies - all be it, I was right in bottom of cassette on the flats. I have done a few gravel events and also worked okay, would like a bigger chainring upfront though - need to check with my LBS if I use a spacer of sorts to clear the frame.

[bleedToWin]

1 hour ago, Baracuda said:

I have Shimano 2x11, with 11-36 cassette and 50-34 crankset. Great for almost everything,

This is where I ended up largely due to the parts in my garage when I started the build. If I could do it all again I'd probably pick the same setup. Really happy with it.

[Baracuda]

14 minutes ago, bleedToWin said:

This is where I ended up largely due to the parts in my garage when I started the build. If I could do it all again I'd probably pick the same setup. Really happy with it.

I see that I can "push" my Ultergra RX derailleur to 11-40 - not officially, but guys do. It may help with a few of these silly gravel races that send you up a goat track in the last few kilometers of 100 miles, but otherwise happy with what I have above.

 

[bleedToWin]

41 minutes ago, Baracuda said:

[snip] to 11-40 - not officially, but guys do. It may help with a few of these silly gravel races that send you up a goat track [snip]

I'll report back after Saturday's "25% on loose rocks" that @guidodg has in store for us!

[RobertWhitehead]

Thank you very much for the input everyone. I think you've convinced me to go with a ring in the front that's in the 40s rather than the 50s. My build will have STI's with drop bars and some mtb stuff thrown into the mix at the back. I will most likely go with 11/46T at the back (mtb setup) with some road gravel crank and ring in the front. I will sell again as it won't be my size. Hoping to make it light and fast 😁

[Kom]

38 minutes ago, RobertWhitehead said:

Thank you very much for the input everyone. I think you've convinced me to go with a ring in the front that's in the 40s rather than the 50s. My build will have STI's with drop bars and some mtb stuff thrown into the mix at the back. I will most likely go with 11/46T at the back (mtb setup) with some road gravel crank and ring in the front. I will sell again as it won't be my size. Hoping to make it light and fast 😁

after a few years riding 1x on Gravel and MTB, im considering a return to 2x:
1 - Efficiency: 1x drivetrains are typically less efficient than 2x drivetrains because the chain runs at more extreme angles, higher speeds, and higher tensions. 
2 - Gear range: 1x drivetrains may not have as extensive a gearing range as 2x drivetrains. (Bigger Jumps)
3 - Component wear: 1x drivetrains experience increased component wear. (Chain monitoring is important)
4 - Chainline: 1x drivetrains have an angled chainline, which can be less efficient. (try rotating your crankset in reverse when the chain is on the top gear, that resistance is real).

I think the most underestimated bargain is the new GRX 2x 12-speed Di-2 which is available for cheap money on certain magician labelled web sites who have excellent service 🫣

[Shwetty]

Another advocate for the 2x11 setup here. 
My 'daily driver' is set up with the 50-34 up front, and an 11-36T at the back. I'm rolling on 50 mm tyres, which adds incredible top-end to the ratios, so I only run out of gears at about 68 km/h (cadence of about 110 rpm). I live in the KZN midlands, and regularly encounter gradients north of 13%, and the 34-36 combo hasn't got me into any trouble (yet). 
A couple of years ago I put an 11-42 cassette on the back for the Swartberg100, and with the b-screw all the way in on a 105 long-cage RD, I could get through all the gears no problem. But as previously mentioned, that was only to get up the last couple km's of the pass with 150 km in the legs already. Ratios like that really aren't necessary for 99% of your riding.
I'm very happy with my setup - on tar, on smooth gravel, and on chunky rocky jeep track. I reckon it's almost perfect for this area. 

[Jbr]

2 hours ago, bleedToWin said:

I'll report back after Saturday's "25% on loose rocks" that @guidodg has in store for us!

I missed that part, did you get a gpx file ? Might then put the 10-52 on... Not sure if I want to put on the small chainring though, at Gallows it was really *** on the fast/flat sections