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Completely unscientific question...

I have a 42 front 10-42 rear setup on my gravel bike... for the last couple years I'm trying to convince myself to pull the trigger on a road bike with 52/36 front 11-30 rear setup.

For a recreational and never will be competitive rider, is there any reason to let this stupid thought win out?

It would certainly give me more top-end but would the gearing be any easier/more efficient to pedal? I have absolutely no mathematic principles to apply to it but I just feel like having more teeth up front (52 vs 42) would be more efficient since that force is pretty direct compared to having less in the back (11 vs 10) which takes more indirect force to spin.

To answer the obvious--no I will not change my gravel bike gearing and no I won't want to sell it to switch over--I'd want to keep both bikes. It actually came stock with a 50/34 11/36 setup but there's something in my head that wanted to stick with a simple single ring setup.

There's also something in my head that really wants to go with a di2 setup and is trying to win over the other half of my brain that reasonably doesn't want to drop 4 grand to get me there to do essentially the same type of riding anyway (I primarily use my gravel bike as a road bike).

Thoughts?

22 comments

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Boatsie [230 posts] 6 months ago
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I ain't a strong rider. Tall leverage is on the bike primarily to bolt downhill and downwind. 52-10 is heaps tall.
Here I'm waiting on a chain breaker to finish my bike. Tall is 53-13 which I'm guessing will be rarely used. Usage intended is coming down 5-7% grades and long flats with 20+ knots on the back.
But aye, if you can get good pedal rpm on tall cogs,, let me admire your tree stumps. Been commuting solid 2 months, getting more speed with pedal rpm rather than heat on knees.
On an aero 8kg fixed drive 50-16 I find sprints of 40kmph, cruising of less than an hour at 30kmph and all day at 20kmph.
With my tall ratio bike I built that above my strength because our local conditions are a continual downhill road of 25 km and dominant winds that blow me home and blow me along flats and downhill of distances about 30-40km.
With only 10 teeth on rear, a compact 50-34 would be heaps tall!

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Boatsie [230 posts] 6 months ago
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Mathematics of powering a bike is fairly simple.
If your mate peddling along with you at the same pedalling rpm. If you were to double the force on your pedals you would double your power output.
Likewise if you were to remain with consistent force on the pedals, by doubling your rpm you would double your power output.

We are mere mortals. We have a limit of force we can comfortably apply to the pedals. Pros know this better than I hence to improve horse power they lower their ratio and increase their rpm at the crank.
Just common cyclists like me don't bother exerting large efforts knowing knees/cranks/peddles will wear faster and increasing rpm at crank is slower at first yet brings thirst to eat properly and use slightly different muscle group coordination.
Per example. If you're riding into the wind and peddling gets harder. A drop of a couple of cogs might result in slightly less effort (about the same) yet twice as fast rpm at peddles. Hence twice horse power.
Therefore, a speed that is about 30% faster!!!!

Big ratios might tend towards downhill sprinting with us non pros.
50/34-11/36 covers a lot of ratios. Already set up hence no need to configure chain length.
Reads awesome bro. (Better than walking up the steep hills. Lol)

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ChetManley [95 posts] 6 months ago
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I use my gravel bike for all sorts, flirted with 1x but not that into it. I use a 46/34 double for everything now, it's plenty of top end for non racers who aren't putting down a load of watts.

It was also good enough for the guy who won the TCR last year.

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hawkinspeter [2381 posts] 6 months ago
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I don't think the gearing will make as much difference as the difference in tyres and aerodynamics on a road bike vs a gravel bike. In general, drivetrain losses/inefficiencies are tiny, so recreational riders are unlikely to notice any real difference beyond which gear ratio you are using.

Di2 is lovely to use, but in my mind is more of a luxury thing. If you've got the money, then go for it but if you have to dress your children in sackcloth in order to afford it, then maybe a mechanical 105 groupset would be a better spend.

Since upgrading to a Di2 road bike, the biggest difference that I found was hydraulic disc brakes vs calipers. I'd assume that your 4k road bike would be equipped with hydraulics.

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kil0ran [1078 posts] 6 months ago
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I did the Di2 thing - great for commuting as it guarantees reliable shifting in all weathers, although the buttons are harder to use in winter gloves than mechanical.

I think if you can find a used 6870 Ultegra Di2 group then that's the best option, at worst you'll need to replace the battery.

I've now gone back to a mix of Tiagra and 105 (chainset & front mech) on both my bikes as that's definitely the sweet spot in terms of performance/weight/functionality/price. Unless you're racing you really don't need 11-speed, a 10-speed Tiagra wide-range cassette will do the job.  You do need to know how to set up and service your drivetrain, or be willing to pay your LBS to do it for you (that soon gets old, and drivetrain tuning is pretty easy once you've done it a few times - certainly easier than wheel building, or diagnosing Di2 issuess).

To get back to your question, it doesn't matter what size the rings are, if the development is the same then the same amount of effort will be required. Crank arm length can make a difference to efficiency but that's one for an advanced bike fit to determine.

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Canyon48 [1062 posts] 6 months ago
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Short answer, bigger gear up front and smaller gear out back is more mathematically efficient.

Drivetrain efficiency improves as mechanical advantage increases. When you are using the 42 front ring with the 42 cassette, you have no mechanical advantage, therefore, the drivetrain loses are significant.

If you could have a gearing with infinite mechanical advantage (i.e. infinitely large front gear) it will be 100% efficient.

Obviously, you can't have an infinitely large gear ratio.

Chain line is important too, the straighter the chain line, the lower the drivetrain losses. With a 42 tooth, you'll spend more time using the small cogs on the cassette, so the chain line will be better.

By far the most important thing is if the range of gears is suited to your type of riding. You could have the most efficient drivetrain, but if the gear range is wrong, you won't be able to use the gears efficiently.

Your gear choice should be influenced by the speeds you ride at, hence why the gravel bike has lower gearing. My road bike, Canyon Ultimate, has 52/36 with 11-28 - absolutely great for fast road riding, as I use the whole spread of gears over a ride. My commute/winter road bike has 50/34 with 11-32, I don't need such top-end gears as I don't hit really high speeds on commutes and I need to lower gears when I taking it easy up hills (with a full rucksack).

 

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Daveyraveygravey [612 posts] 6 months ago
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My road bike has 52/36 and 11-32, I use all the gears.  If I lived in the Alps I would be tempted to go proper compact at the front but other wise I think you want a big chainset.

I am old school though, until 3 years ago I rode a 53/39 with 12-28.  I could get up the Sussex hills with that, but I would be painfully slow and out of the saddle to do it.  My friends on compacts would sit and spin and ease away from me.

 

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Boatsie [230 posts] 6 months ago
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Daveyraveygravey wrote:

My road bike has 52/36 and 11-32, I use all the gears.  If I lived in the Alps I would be tempted to go proper compact at the front but other wise I think you want a big chainset.

I am old school though, until 3 years ago I rode a 53/39 with 12-28.  I could get up the Sussex hills with that, but I would be painfully slow and out of the saddle to do it.  My friends on compacts would sit and spin and ease away from me.

 

That reads perfect. I ended with 53/39 with 13-23. Mainly because price. Less than 10 quid each on 2 cassettes and £15 a combination on 4 cassettes.
Being a tight group might have made chain easy too.
I don't mind walking up steeps though; sort of used to it. If I had used my brain better I would have liked to try 50/39 13-14-15-16-17-18-19-21-23 and will be at such later.

Gear ratios are important if you want to remain in comfortable effort zone. A real example is into a head wind . If hurting at 53 -13, by dropping back 2 to 53-15 and increasing peddling rpm by 50% the road speed increases 71%!
Muscles love heat, ligaments enjoy the beat. Less energy is wasted although diet is where food ware brings enjoyment of wear.
But like Daveyraveygravey wrote. I believe you'd like a 52  3 you get used to what you have.

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zero_trooper [269 posts] 6 months ago
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It may be a 'completely unscientific question', but it's certainly an interesting one.
Enjoying the responses.

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VeloUSA [268 posts] 6 months ago
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I am going to assume you've ridden your gravel on the road with gravel tires. With this in mind and knowing good road tires would improve rolling resistance how much gear changes are you looking for, and how often do you spin on the smallest cog?

For example on gear rations:

1. Running 52/12 is 8.7%. Running 42/10 is 8.5% - .2% difference

                       52/11 is 9.5% - 1% difference

2. Running 50/11 is 9.2%. Running 42/10 is 8.5% - .7% difference

The least expensive option to try is getting good road tires. eg; Conti 4000s II in 25/28mm. Mount them an go ride (if your current rims can take smaller tires). You'll know then if a bigger chain ring is what you want, or not. You'll also know that you can mount the Conti's on your new ride.

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Miller [128 posts] 6 months ago
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Don't worry about gearing efficiency, drivetrain losses are not significant with derailleur gears assuming they're not faulty or gunged up. Stop thinking about direct, indirect, whatever.

What does count is having the range of gears you need.  Your proposed 52/36 11/30 setup would work fine although 52-11 is a very tall gear more suited to racing than normal riding around. I'd prefer a 50-34 up front but it's not a big deal.

Di2, or EPS as I prefer to call it, might be a luxury but you'll absolutely love it.

 

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Boatsie [230 posts] 6 months ago
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Mechanical advantage isn't always an advantage.
Take a car. Like a human the car has a torque band. At a climb, we the pilot has choice. Drop it back or hold top cog . If we hold top cog we slow and then stall yet if we had dropped it back we could have easily climbed the hill. Hence the mechanical advantage became an impossible task.
We all get head winds, tail winds, gradients. The flatter your routes the tighter your groups or your prepared to walk up a swift descent.
The cogs on that will get you up and down, reads really sweet broad range but unless you're an Olympian peddling 150km pre work daily or similar, I guess 52-11 would be used as rather swift descents.  1

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kvert [2 posts] 6 months ago
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Excellent comments. To answer the road/gravel tire question... yes, I currently ride on a Maxxis Rambler/Re-fuse 40mm combo. The Re-fuse is probably the closest I want to get to road slicks on the bike, without being a road slick at all, even though the rims could certainly take thinner ones.

Again, very interesting and it at least it basically confirms what I felt in my gut--that there is not really going to be some magical advantage that I can hope for in gearing alone. I feel like I'm the epitome of a rec rider where if I do a couple hours on Zwift I can hover around the 3.5kw/g mark but I also consider that a very hard effort and I'll be spent afterwards.

Yea, my downhills will probably go by quicker and my long and steady ascents might improve just a bit--but the majority of the ride will be the same. So I'm back to not being able to use some "need to have it" mechanical advantage to convince myself of making the purchse... pure luxury purchase now. Hah.  1

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Miller [128 posts] 6 months ago
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Can you get some test rides on road bikes so your thinking isn't all theoretical? You might just love the road bike experience. 

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jterrier [210 posts] 6 months ago
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I am not quite sure what you are getting at but just bear in mind that it takes a very very fit rider to sustain power through either a 50-11 or 52-11 combo for long periods. If you look at the wear on the average riders cassette, its all in the middle. You maybe spend 3% of your ride in that absolute top gear (50-11 with a compact, for example). So its barely worth having. More usable gearing in terms of front chainrings is 46/32, as you can easily envisage spending a good amount of time turning the 46-11 combo on a nice A road run, and the smaller ring means you can run a tighter block at back (11-28 maybe) which eliminates some of the indelicate shift action getting up to/coming off of a 32 tooth sprocket.

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madcarew [797 posts] 6 months ago
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For the same ratio, ignoring utterly miniscule drivetrain efficiency differences, the pedalling effort is the same at the same speed. Overall your 42 chain ring set up is about 1-2 gears lower than your 52:36 would end up, so easier overall, but at any given cadence for the same speed, it is just as easy / hard to pedal on either combo

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Boatsie [230 posts] 6 months ago
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madcarew wrote:

For the same ratio, ignoring utterly miniscule drivetrain efficiency differences, the pedalling effort is the same at the same speed. Overall your 42 chain ring set up is about 1-2 gears lower than your 52:36 would end up, so easier overall, but at any given cadence for the same speed, it is just as easy / hard to pedal on either combo

I agree. Same power output.
If we use 1cubic solid cube blocks moved 1 inch to demonstrate torque and further inches to demonstrate rpm of crank.
We as humans can measure strength(torque) and as example. If I struggle to move a 100kg cube then I would view such as my peak strength. If I move 50kg 3 inches I have done so easier than 100kg 1 inch yet I have demonstrated 150% horsepower doing such.
Theorically I could push 1kg hundreds of inches yet I know I don't find comfort at either ends, eg busting my knees and back with 100kg nor losing control and tripping at more than 2-3 rp.second.
Balancing power and strength is better with practice.
Regardless of strength, it takes 4 times the power to push twice the speed. In reality I can comfortably cruise along at 30kmph in 6th cog whereas I exhaust faster sitting at 25kmph in 8th cog. A similar setup, I think the front is a 44t (or near) and the rear is an 8 speed.
I agree with earlier regarding trying skinnier tyres on the gravel bike because you can feel your routes and decide better plus most bikes I see aren't top shelf hence the front rear tyre combo becomes a front and a spare. Tyre liners are excellent..
An advantage you might find with the very tall cogs is if your a lazy casual, in no rush rider that convexs a peak and just rolls using gravity, catching breath, into top cog where assistance isn't hurtful to your stride and just poking her a bit to let you ride faster. Faster ma star faster. Lol
Just reread your initial write. I'm going opposite way from 23-25-28 mm to 38mm. I'm guessing it will be much the same yet slower and heaps more 'don't care with concentration and want to protect rims' on the nice cushiony fatties.
Hence should enjoy either. 50 or 52 is honestly plenty of crank. To save some life more teeth on rear grip better when worn. 50-12 is pretty strong. Although no where near as high as 52-11, the bloke I bought a bike off was a multiple seasoned daily commuter and he rarely used 52-12. Much flat, slight continuous downhill of 10m drop 15 km roll. Something like that.

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Nixster [406 posts] 6 months ago
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Advantage of a double over a single up front is the smaller jumps in the cassette for the same coverage of ratios, which can help maintain cadence.  For the road that's more important however not everyone is sensitive to it.  If you frequently find yourself running out of top end gears then go 52-36.  If not, compact or below will likely suit you better and give lower drive train losses as others have said.  Drive train losses are not insignificant but if you're using knobblies then road tyres will give you the biggest benefit.

Everyone has their preferred cadence and finding the gears that work for you and your type of riding is going to help you.  If it's flat, you're bigger and you like to pedal at 80rpm then larger chain rings, if it's proper hilly, you're Quintana-esque and you like to spin then smaller.  There is no right answer.

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Daveyraveygravey [612 posts] 6 months ago
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jterrier wrote:

I am not quite sure what you are getting at but just bear in mind that it takes a very very fit rider to sustain power through either a 50-11 or 52-11 combo for long periods. If you look at the wear on the average riders cassette, its all in the middle. You maybe spend 3% of your ride in that absolute top gear (50-11 with a compact, for example). So its barely worth having. More usable gearing in terms of front chainrings is 46/32, as you can easily envisage spending a good amount of time turning the 46-11 combo on a nice A road run, and the smaller ring means you can run a tighter block at back (11-28 maybe) which eliminates some of the indelicate shift action getting up to/coming off of a 32 tooth sprocket.

 

Most of what you say is right, but I would argue you don't have to be THAT fit to spin out a 46-11.  It wouldn't be too steep a downhill or too strong a following wind to run out of gears with that set up.  In my opinion, of course!

Another advantage of a front mech is sometimes the chain bounces off either ring, and if you are lucky you can use the mech to get it back on again.  Not something you want to make a habit of though.

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Boatsie [230 posts] 6 months ago
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An advantage of a tall geared road bike vs a tall geared trail bike is topography. On the road during a descent there isn't that need to have an accelerating gear ratio because roads aren't weaving trees and bumps and such similar loves.
Hence if you have a capable ratio selection to climb and motor along flats with; I ;not being a racer, you might be lazy like many of us and after a peak, hit top cog and regard less concerning acceleration because you're underway and may input light or heavy stance on your crank and enjoy the distance. Ohh look a tree  1 whoo it's the other side of the gutter.
50/11 is pretty tall man. 53/13 similar. Both plenty enough to push wind coming down or slow crank and recover

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kvert [2 posts] 6 months ago
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I guess I was approaching it more from a tighter grouping being more efficient, angle.

 

i.e. My gravel bike is 42;10-42 and the road is 52/36;11-30. So 11 gears to cover 1-4.2 vs 22 gears to cover 1.2-4.73. Not an exact range match, and I'm sure there's some overlap in the big/small, but there's still a slightly tigher grouping overall.

 

Either way, nothing that would matter enough anyway... just trying fiddle with numbers to justify the purchase.

 

But, I ordered the road bike anyway (Canyon ENDURACE CF SL DISC 8.0 DI2) and it actually should be arriving within a few hours.

 

Faster/more efficient ponderings go out the window now... it doesn't matter... I'm still excited about it.

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Miller [128 posts] 6 months ago
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kvert wrote:

But, I ordered the road bike anyway (Canyon ENDURACE CF SL DISC 8.0 DI2) and it actually should be arriving within a few hours.

Yay. Doesn't matter what the question was, that's the right answer, lol.