Larger chainset on folding bike

[Squibnocket]

I own a Dahon folding bike with the original 7 speed nexus hub in the rear wheel and original chainset which has a 38 tooth chain ring with a 16 tooth sprocket.
Could I put 45 chainset on the front with a 21/22 sprocket on the rear with a new chain, and would it all still work?
I understand the gearing would change but I use it for commuting and shopping no major hills to climb.
Thank you

[Norman H]

What are you hoping to achieve ?

38/16 = 2.375:1, 45/21 = 2.14:1 and 45/22 = 2.05:1

If you are looking for a higher top gear either increase the size of the chainring or reduce the size of the sprocket, or a combination of the two

If you want a lower bottom gear do the reverse. Increase the size of the sprocket or reduce the size of the chainring.

[Squibnocket]

Thank you for the reply, I wasn't sure if putting a bigger chainset on would unbalance the nexus hub so to speak.

[Norman H]

Putting a larger chainring on won't harm the nexus hub it will merely raise the overall gearing. However fitting a larger sprocket at the same time is counterproductive as it will simultaneously lower the gearing. I'm not familiar with the Dahon but a larger chainwheel may affect the fold.

You need to be be more cautious when lowering the gearing so as not to exceed Shimano's recommended torque limit for the Nexus hub.

Here's a link to your current gearing (upper chart) and for comparison the lower chart shows the effect of swapping the 16T for a 19T sprocket. You can investigate other combinations by dragging the chainring and sprocket symbols at the bottom of the page. A “High Torque!” warning appears on the left hand side if you exceed the torque limit of the hub.

[fausto99]

You'll need to change the chain length. Also check that a larger chain wheel does not foul the frame or interfere with the folding.

[thirdcrank]

Your plan seems unclear in that you are talking about increasing the size of both the chainwheel and the sprocket.

[Bonzo Banana]

Decathlon do a very reasonably priced 52T crankset for £14.99 which they fit to some of their Tilt folding bikes. Whether your frame allows such a large crankset is another matter but its a decent option if you want to make all gearing higher/faster. Derailleur folding bikes are typically very low geared but unsure about Nexus hubs. I know the Nexus 7 is actually a 9 speed hub with two gears mapped out from selection one of which is the direct drive gear so the Nexus 7 is mechanically more complicated than the Nexus 8 and doesn't have the Nexus 8's 1:1 direct drive gear which is gear 5 so the Nexus 7 has a reputation for being less reliable than the Nexus 8 despite having less gears. Anyway here is a link to the Decathlon crankset below. Even though its normally fitted to a derailleur based bike I can't see it being an issue being used for a single speed chain of the Nexus 7, the chain pitch is the same and its only one chainring so no front derailleur shifting. Also its a steel crankset so typically very long lasting albeit at the expense of some weight.

https://www.decathlon.co.uk/p/single-ch ... 81&c=BLACK