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I would like to custom build a crankset which would like the one I have on my ebike, but with more teeth. My current chainring is 52T, and I would like to go up to 58T. What I have is a four bolt, crankset, with two chain guards. Unfortunately, I am told that it is one piece, forged together somehow, and cannot be taken apart. So, I need to make one myself from parts found in ebay and aliexpress. What I was thinking was buying a 58T chainring, two chainguards, and a 130BCD crankset. Does this make sense? Would it all fit? Are chainrings all metal? Should I worry about plastik? Would it be about the thickness?

Why would I want one? My ebike reaches 30KMH, at which speed I am spinning out... I have 6 gear shimano, but with the motor, I never use anything but the highest gear. I would like at times go faster, pedal assisting the motor, so as to gain few KMH.

The objective is a relatively cheap speed + exercise combination.

I figured out the math that in adding 11.5% (58/52 - 1) to the number of teeth, I could be spinning out at 33 km/h. This is not very much, but it may be cost-effective vs the alternative of changing the motor and controller.

My rear wheel is 20", so the relatively large and not so common chainring does make sense.

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    1. Will a chainguard be as big as a 58t chainring? 2. Why do you need 2 chainguards? 3. A 58t chainring might interfere with the chainstay. 4. Apart from some very exotic carbon-fiber ones, chainrings are aluminum (or perhaps steel for very cheap ones). 5. It looks like you've got an integrated chainring/spider. Hard to say. It might be replaceable, but you'd need to know how it mates to the spindle to find a replacement.
    – Adam Rice
    Oct 14, 2021 at 20:15
  • I found a crankset on ebay, ebay.com/itm/… with 58T. My current has two guards, which seems to be the standard. I edited the question to explain why I would want one.
    – Yossi Gil
    Oct 14, 2021 at 20:30
  • "Spinning out" at 30km/h on a 54 chain ring. What's the wheel size and rear cluster sizes. A 58 won't make that much difference.
    – mattnz
    Oct 14, 2021 at 21:07
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    "ebay and aliexpress" your LBS will also be able to get parts that will work and will be far less likely to maim you
    – whatsisname
    Oct 14, 2021 at 21:42
  • Replacing your cassette might also be a much easier and cheaper option to consider
    – whatsisname
    Oct 14, 2021 at 21:43

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The "two chainguards" is a cheap way of keeping your chain on and keeping clothes off the chain. You could use a narrow-wide chainring to assist in chain retention, and tuck your trouser cuff into your sock.

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