My commuter is a singlespeed. Because it’s a mountain bike frame the teeth on the chainring have always been in the 30s and the teeth on the sprocket the mid 10s. However, if I go larger (but keeping the same gear inches, obvs) will there be less wear because there is more teeth to share the load, or will it be the same?

I’m asking as it’s a bit of a conundrum as much as its practical value to be honest! 🙂

Yes.

Steel ring will help even more.

Bigger is better

Yup, and for an even longer life go with odd numbers, e.g. 33-15. That way each tooth sees inner and an outer roller every other revolution.

That and 3/32 sprockets, chains and chainrings rather than cheaper pressed steel stuff which is a false economy.

Less wear and also greater drivetrain efficiency (primarily because the angle through which the links rotate is reduced).

I was thinking about this the other day while out riding. With a larger ring, the chain tension will be lower because you have less leverage, plus that lower tension will be spread over more teeth, so the load on individual teeth and chain links should be reduced by the square of the proportional increase in chainring size. In other words, going from a 24 tooth ring to a 36 tooth ring (1.5 x) should reduce the load on each tooth by a factor of 2.25 (1.5 x 1.5). That should reduce the wear on the teeth and chain, although I have no idea how it plays out in the real world. I suspect it would make a greater difference to aluminium rings than steel.

My Rohloff set up is 40 16 and a chain lasts 3 years of muddy all year round commuting with never a proper clean, just the occasional very quick wipe over and more gearbox oil liberally applied. The oil is just what has been lying around from a previous car. The steel chain ring is reversed after 3 years and the steel cog replaced. I could reverse that too but it wouldn’t last another 3 years so don’t bother.

If you keep the same gear inches then your cadence remains the same so therefore the chain interacts with each tooth less often which equals less wear.

With a bigger front ring, each link of your chain will visit the chainrings more frequently. and also be in the muddy splash zone more frequently.

I was thinking about this the other day while out riding. With a larger ring, the chain tension will be lower because you have less leverage, plus that lower tension will be spread over more teeth, so the load on individual teeth and chain links should be reduced by the square of the proportional increase in chainring size. In other words, going from a 24 tooth ring to a 36 tooth ring (1.5 x) should reduce the load on each tooth by a factor of 2.25 (1.5 x 1.5). That should reduce the wear on the teeth and chain, although I have no idea how it plays out in the real world. I suspect it would make a greater difference to aluminium rings than steel.

@hols21 – I would think the load-spreading as toothage increases is more likely to approach a maximum value asymptotically, meaning no further load-spreading above a certain size.  What that size is, havne’t a clue.

Bigger rings are more efficient.

I suppose there is also more chain the share the load?

And also, the larger the chainring and sprocket, the shallower the angle the chain has to flex and extend by to circumnavigate them, therefore each joint will go through less range of motion, and therefore wear out less with each revolution?

@greyspoke – I suspect you are probably correct about there being a limit to the load spreading, surely someone must have studied that and there must be published tables of optimum sprocket and chain sizes for different levels of power. Factories use chain drive with electric motors with hundreds or thousands of kW, so there must have been research into it.

hols2

Member

@greyspoke – I suspect you are probably correct about there being a limit to the load spreading, surely someone must have studied that and there must be published tables of optimum sprocket and chain sizes for different levels of power. Factories use chain drive with electric motors with hundreds or thousands of kW, so there must have been research into it.

I’d love to see that!! 🙂

<span style=”color: #444444; font-size: 12px;”>”With a bigger front ring, each link of your chain will visit the chainrings more frequently.”</span>

But it’s a single speed so if there is an increase in teeth there must also be an increase in chain length so more links to go around. 🙂

Actually the thing that would increase life expectancy the most would be a chain guard

<span style=”color: #444444; background-color: #eeeeee;”>load spreading</span>

You’d be surprised!

Even on a new/unworn chain relatively few teeth actually take the load. Once you throw in some wear it can be down to literally just a few.

Go and prop your bike up, get someone to hold the brakes on and then apply some force to the crank arm to put the top run of chain under tension. Now pick random points from about 3 o’clock onwards on the chainring and pull the chain away from the ring (while still it’s still under tension). You’ll realise pretty quickly that very little of the ring past that point is actually doing any real work!

bah, edit broken!

in above comment I obviously mean in terms of sharing the instantaneous load, it’s only a few teeth at a time, but more teeth/bigger ring still better for wear and efficiency for the reasons discussed earlier.

Optimum is to have an odd number rear and even number front to even out wear, and if my reasoning is right then super optimum is to have a prime numbered rear and a front that is an even number but NOT a multiple of the prime – so eg: 32:17 or 32:19 are super optimum but 34:17 is not. That way the teeth experiencing maximum load at both ends are changing at different rates to each other so when one set are loaded you are loading a different set at the rear more frequently, and because it’s a prime number then the division of the full number multiples of one by (different) full number multiples of the other is an integer less frequently. There is an equation somewhere, but that would be too geeky.

I think to be super super optimum, you should also use a prime numbered front ring, but I can’t find a 31T NW anywhere, and a 37T would be too big, but if anyone knows where I can find one, I’m listening.  I guess 33 – 17 would be quite good though.

Why would an even numbered chain ring even out the wear? If it’s better to have an odd numbered sprocket, why doesn’t the same apply for the chain ring?

Because multiples of odd/odd is an integer more often than even/odd, particularly if the denominator odd is a prime number*.

Sorry if that wasn’t clear, not easy to explain maths in words.

* unless as noted both are prime, but clearly not equal, and obviously not if the chainring prime is a whole number multiple of the sprocket prime.

“not if the chainring prime is a whole number multiple of the sprocket prime.”

For that to happen wouldn’t the sprocket need to be 1?

technically, yes. Which is why i said obviously.

Guess the questions is answered.

Maybe also a possibility to look at the problem:

You transfer power. You can describe your sprocket / chainring / chain as “GEARBOX”.  If this gearbox which transfers the power gets smaller the peak forces “in this gearbox” automatically move up. Physics. Higher peak forces meas higher LOCAL PRESSURE on the contact points.

And this pressure creates – in the end – wear.

So yes – smaller gearbox for same power means less lifetime…

try the chain sections here: https://my.misumi-ec.com/maker/misumi/tech/mech/index.html

@theotherjonv

Having difficulty finding an odd numbered NW ring.. think for a minute why that might be 😆