A couple of years ago I bought a rather cheap racing bike after my mountain bike was stolen. I didn't use it much at first. Now, with corona I spent a lot of time on my bike and probably did around 1000-1500 miles in the last 3 months.

What do I need:

Now the chain isn't that stable anymore and I guess I need new chainwheels. I went to a forum and asked about details on how to measure the size to replace them. The users were mostly amused/shocked about how used my chainwheels look but did not really answer my question. There was one good suggestion to directly invest in a crankset, which makes sense.

What do I need it for:

Like I said my bike was rather cheap ~315 pounds (https://www.decathlon.at/rennrad-triban-500-rot-id_8377759.html). But I am perfectly happy with it, since I can do my daytrips of 20-60 miles or multiday trips 250-400 miles and I don't care much if my bike is 2 pounds more or 10% slower.

My Research:

First I spent quite some time researching chainwheels and how to replace them. But I am also fine, changing the whole crankset (if they include new chainwheels :)). I found that cranksets are much cheaper for mountain bikes than for road bikes. Might be due to the weight but I also read that MTB cranksets might also be used on road bikes, so I am not sure.

The price range seems to be insane, like 20 - 1000 Pounds and more. I prefer a lower price but am aware that the quality should be good enough that the material does not break too fast.

  • Quality Brands:

My research indicated that Shimano has good quality material. But still there also seems to be a wide price range for them

  • Cheap alternatives:

If I may add a few examples:

Shimano 1

Shimano 2

Shimano 3


That price range makes perfect sense for my current bike, from my current perspective.


Are there arguments for not using one of these for my bike if I plan to ride around 1-3k miles the next years?


Concerning doubts that I require new chainwheels. Please don't laugh too hard, Biking just started as a corona-replacement hobby and escalated quickly ;)

enter image description here

  • What you linked as "Smimano 3" is not actually Shimano. It is ProWheel and pretty similar to what you currently have. Some really very basic type. "Shimano 1" would probably work, but you may need a new bottom bracket. The others are doubles and you do need a triple. You cannot just buy a double. Your front shifter and front derailleur need a triple. Jun 7, 2020 at 8:05
  • Can you confirm what the BCD is of the large chainring? it is probably written on it, maybe edit in another photo, of the whole chainset. The one on the product page you linked is 130mm
    – Swifty
    Jun 7, 2020 at 8:23
  • At the very top right of the photo it looks like a chainring bolt. That would be good, because you could change just the rings. Some basic Shimano chainsets are riveted and aren't designed for just the rings to be replaced. To be sure that's the case, a better look at this fastener would be good - if a hex key fits, it's a bolt and you can change just the ring
    – Chris H
    Jun 7, 2020 at 11:22
  • 1
    @Swifty thanks for the pointer, on the Decathlon page it is much better visible than on the photo. Jun 7, 2020 at 11:45
  • Also be aware that Shimano does have a good quality material, but also makes very cheap stuff for supermarket bikes (the A070 Tourney line). The second most common manufacturer is SRAM. But other brands also do good stuff. FSA is a good quality brand and Praxis is as well. Those will be very likely above your budget but the aim is not to recommend a product for you but just to make clear you should not just look on the brand name. Shimano is not everything. Jun 7, 2020 at 12:12

1 Answer 1


You probably foremost need a neww chain and you will also need a new cassette.

What you are linking are chainsets. You can normally just buy new chainrings for your existing crankset. As others mention in the comments, check first, whether the aluminium thing we see in the photograph in the top-right corner is a bolt that can be released with a hex key or a rivet. If it is a rivet, you will need a whole new crankset. See the bottom of the answer for a new crankset.

First for the cassettes

You can buy any 8 speed cassette that fits your rear derailleur in terms of size of the cogs - sprockets. The current one is 12 - 25. You likely have the RD-32 derailleur with max cog 28T and total capacity 39T. That means you cane safely go to even to 11-28T cassette.

In general, 8 speed cassettes are pretty cheap but those with older sprocket sizes (like yours) tend to cost more. I do not know why, but I do see it n the shops. But you can look around for the best deal, they are intercompatible.

With a triple crankset you can keep your small range cassette 12-25 but you can think about a wider 11-28. You get a bigger range, but also bigger differences between gears and more overlap between chainrings. But as I wrote, for some reason they appear to be cheaper and easier to find. Like here https://www.bike-components.de/en/Shimano/Claris-CS-HG50-8-8-speed-Cassette-p35939/

But shop around, look for HG-40, HG-50, HG-200 or Suntour 8-speed cassettes and see if they also have a cheap 12-25 somewhere. I did see it on Czech eshops but they were more expensive.

Do not forget that firstly you need a new chain and measure the chain stretch regularly next time so you do not neet the buy the cassette next time. A new chain is much cheaper. A chain measurement tool (chain gauge) is worth the investment. Even in terms of money saved.

From the update it is clear you also need new chainrings:

Buy new chainrings, unless there is something really bad with your cranks that you did not show. But I regard this as unlikely. If the chainrings can be released by the hex key.

You probably have this crankset http://www.pro-wheel.com/main/?product=ounce-631-tt or a very similar older model. The linked one is 9-speed but you may have an 8-speed version that is no-longer advertised. In that case it is 130 mm BCD and 74 mm BCD. It is best to measure it yourself. Or, you would at least give us a better picture of the crankset. Best with some scale, like a tape measure. In the Decathlon link the BCD size is actually written on the

You can also buy from other brands, not just ProWheel. You also can change the sizes. You have 50, 39 and 30T but that can be changed, if you keep the difference. If you are not experienced judging what is fine, I would keep 50, 39 and 30, though.

For example, something like this https://www.sjscycles.co.uk/chainrings/compact-chainring-steel-110mm-bcd-5-arm-silver-50t/ Just to give you a picture how it should look like. You have to shop around in your country.

If you want to buy a new crankset or even a combo with a chain and a cassette, remember that you need a triple one. Currently you have 50-39-30. You will often see 48-38-28. That should work too. It may require readjusting your front derailleur.

With a new crankset you will probably need a new bottom bracket. They are sold with different length. You will have to find out the correct length for your new crankset. And, if you ugrade to something with a different bottom bracket type (like Octalink or even Hollowtech II) you need the correct type. The cheapest cranksets use all square taper bottom brackets but with different lengths.

  • Thank you so much for the Response @Vladimir (+1). I added a Picture to illustrate that i probably do Need new chainrings(wheels). Thanks for the hint on the chain, i saw some Combo offers for casette + chain + crankset, maybe that would be a good way.
    – Tlatwork
    Jun 7, 2020 at 7:40
  • 3
    @Tlatwork New crankset is always the most expensive. You can go that way, it is easiest, but you will pay much more. Do remember that you need a new chain. And you need to buy it in regular intervals. Get a chain gauge too. Your chainwheels will last much longer. Jun 7, 2020 at 7:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.