I have a Specialized P.1 which I bought secondhand a few years ago on a whim. I don't have the skills to ride it as was intended but have enjoyed riding it down stairs, just to go outside for a bit when the weather is not great and on pump tracks.
The gearing seemed to slip a bit which made me nervous and now I have taken it off I can see quite a bit of wear. So I want to replace it before a trip to some spots in Brighton. It has 25:12T gearing (a 2.08 ratio) and a KMC chain marked 1F-2 on it.
I always found the gearing very low so I have bought a new 28T chainring and wondering what to pair it with. 28:13 would result in 2.15. Is that noticeable or should I go 28:12?
It will be one of these: https://winstanleysbikes.co.uk/dmr-single-speed-cassette-sprocket
Also the new chain I have bought is a 'KMC Z1 Wide with EPT' and OK-2 stamped on it. Is that going to work OK? It says 1/8" wide on it and the teeth of the chainring are just less than that so I guess so and that a narrower chain would not work.
It is all a bit unfamiliar despite MTB stuff being more complicated really. Advice gratefully received!
2:1 ratio is pretty common. Going above that and you'll start to need longer run ins to accelerate.
12t might not let the chain engage properly without rubbing on the freehub spacers.
1/8 chain is the widest. 3/32 is generally more common although a jump bike may well have had the wider chain. It won't make a noticeable difference being too wide. And doesnt actually make it any stronger.
I run a 32:15 on my 26" jump bike and find that perfectly fine for pump tracks, dirt jumps and the like - which is 55.5 gear inches.
Paired with a 28, that suggests a 13 should be fine!
Great, thanks both. I agree with you @thisisnotaspoon - I suspect there is some chain spacer interference so I think 13T is a good idea for that reason too.
Sounds like it will all work nicely enough for me to do myself an injury 🙂
Why not go bigger on the sprocket and chainring for less wear?
Also, I seem to recall 36:16 was the go to ratio BITD.