PacificSpray

I live and tour in steep hilly areas and want an easier climbing gear for mostly pavement and rail trails.
I have an HPV FX20 Gekko trike (20” rear wheel).
Hub is SA 3-speed, Cassette 8-speed (11-34) and Chainring 1x110bcd (5 bolt) 46T. So effectively a 1x 24 speed.

I’m considering a 34T or 36T chainring. The crank arm looks like 170mm.
I never use the highest gears.
My online searches reveal that I could easily err because of my limited knowledge of chainrings, and I’m not confident to proceed.
Would you knowledgeable folk please guide me and/or suggest something suitable, and point out potential pitfalls?

HillRider

Your 110bcd 5-bolt crank will fit as small as a 33T chainring (34T is far more common) so your proposed change will work. I don't know if your current 46t chainring is a "narrow-wide" design to aid chain retention but try to find a replacement of that type.

PacificSpray

Thank you. Are chainrings specific to 1x, 2x or triple setups or can I ignore that?

HTupolev

They can be, but narrow-wide chainrings are in general 1x-specific. The narrow-wide profile is specifically intended to prevent the chain from derailing, which obviously is problematic if you're using a front derailleur.

PacificSpray

The teeth, on close inspection, appear to be of constant width, but on either side of the ring are very effective supports. This suggests to me that a smaller ring might no longer be supported as effectively. So a narrow-wide would become more important?

HillRider

OK, your current crank has chain guards on both sides of the chainring and these keep the chain in place. A smaller chainring will probably allow the chain to rub on the guards when on either end of the cassette. So, delete the guards and use a narrow-wide chainring to accomplish the same thing. Depending on the thickness of the current set-up you may need shorter chainring bolts when the guards are removed.

bwilli88 

Here is the equivalent of your setup now. The SA 3 speed gives you the same as a 55x46x33 triple. With this you have a low of 21.9 Gear inches


Changing to a 34t chain ring will lower that to 15.7 gear inches.


Not too much of a difference. When you get that small you can almost walk faster. Going to a 42 or 39 might be easier and still give you some in the upper ranges.

PacificSpray

Thank you for your work. I appreciate it.

PacificSpray

That makes sense to me. Thank you.
The plate thickness of the 46T is 3mm (aluminum). Two prospects on Amazon are both 4mm. Without the side pieces I may be able to use the existing bolts/screws.

HillRider

The OP is riding a trike so there is no such thing as too low a low gear. They are heavy and climb very poorly since you can't stand to use your weight and they can go at a crawl speed since they can't fall over. Yes, you could walk faster than the lowest gear will let you pedal but not uphill and pushing the trike.

PacificSpray

You are correct. The OP also has very old knees.

SoSmellyAir

PacificSpray is using an 8 speed cassette and presumably an 8 speed chain. Are there narrow wide 8 speed chain rings? Is he not better off with a regular chain ring?

Surly 34t x 110mm Stainless Steel 5-bolt Chainring - Modern Bike

Surly 36t x 110mm Stainless Steel 5-bolt Chainring - Modern Bike

PacificSpray

I have replaced the factory 46T narrow chainring with a Deckas 34T 110x5B round narrow-wide (Amazon). It fits perfectly and has addressed my climbing problem. And I learned what I needed to learn from the replies. Thank you.