Cycling UK Forum

Hi All,

Never worked on a bike technically before but very technically minded having rebuilt motorcycles and cars in spare time so i'm sure ill pick it up quick enough, just need a little advice on getting correct parts for replacing cassette, chain and crankset for my new pre-loved specialised vita (pretty sure its this one - https://www.specialized.com/gb/en/vita- ... 573-106273).

According to the website it has a:

CASSETTE - Shimano, 8-speed, 11-32t

CRANKSET - Shimano FC-M131, 48/36/26T, w/ chainguard.

Does this mean that I can put any 48/36/26T crankset on the bike or does it have to be the shimano FC-M131? Same question applies to the cassette - can it just be an 8-speed, 11-32t or only the shimano branded product?

Equally speaking, does it have to be a 48/36/26T crankset or can I, for example, use a 48/38/28T shimano crankset?

I guess what i'm asking is, what specs are important when replacing with new cassettes and cranksets or can I use any three cog parts?

I've watched a few youtube videos and the replacement I can easily handle. I just need to know the correct parts.

TIA

Does this mean that I can put any 48/36/26T crankset on the bike or does it have to be the shimano FC-M131? Same question applies to the cassette - can it just be an 8-speed, 11-32t or only the shimano branded product?

It just needs to be compatible with Shimano, which will give you a choice of manufacturers. The cassette may have spacers behind the largest sprocket that you'll need to hang on to, some (or all) may be needed again

Equally speaking, does it have to be a 48/36/26T crankset or can I, for example, use a 48/38/28T shimano crankset?

No, but you'll possibly need to alter the chain length a little if you change tooth count

I guess what i'm asking is, what specs are important when replacing with new cassettes and cranksets or can I use any three cog parts?

Spec isn't too important for the changes that you have in mind, but you might need a different style of bottom bracket that also needs to preserve the chain alignment

I've watched a few youtube videos and the replacement I can easily handle. I just need to know the correct parts.

Parts aren't really the problem, but you'll possibly need a pile of new tools. In the light of your experience you might find that an exciting prospect, but it will cost

Consider a chat at your local bike shop or an organisation like this one in Leeds https://pedallers-arms.org/who-are-we/ to get more in-depth help

The key, point being that it's the specification that matters, not the part number, unless you are going for an exact replacement.

Hi Lorna, welcome to the forum.
Shimano parts have the part number on them, you have to search around a bit.
as already said, you don't necessarily need the exact part, just something which will work with what you have on the bike. Shimano produce tables of compatible parts, there are forum members who are much better than me at navigating all the specifications; i tend to just Google the part number.
For example, an 8 speed chain is an 8 speed chain, there is no reason to go for a Shimano chain; cassettes much the same.

Now, its a very long time since i had a motorbike, but its my recollection that on motorbikes its the chain thats the expensive bit, so you replace the chain and sprockets all in one go.
On pushbikes, its the other way round; chains are cheap, cassettes and chainsets (relatively) expensive.
Wear happens where the inner link plates pivot on the rivets, so the chain rollers get further apart. (people used to say the chain "stretched".....of course, steel is fairly resistant to stretching!
When the chain rollers are further apart than designed, the chain rides up the sprocket teeth to where the new roller spacing matches the gap between the teeth. Left too long, the teeth will wear to the "wrong" shape, and if you then fit a new chain it won't work, the new chain will skip on the worn sprocket.
So, unless you are sure that the whole transmission is knackered (cassette teeth like sharks' teeth) its worth trying just replacing the chain; if you replace the chain and the new chain works on the existing cassette, its happy days. If the new chain skips on the old cassette, bung the old chain back on until you can get a new cassette (and the tools, as somebody said). Chain joining is easy these days, with a magic link.

If everything is truly kippered, you may have to get a new chainset as well, I doubt your existing chainset has replaceable chainrings.
This is a bit more complex; your front mech. will be designed to play nicely with a particular set of chainrings. the difference in number of teeth between the middle and big chainrings should be kept exactly the same, eg. 38/48 = 10 teeth difference. The middle to small difference is less critical. If you go from a 48 big ring to a 44 (just grabbing numbers out of the air) you will have to lower the front mech. a bit. You don't have to stay with Shimano for the chainset, but you do have to keep the chainrings the right distance from the bike centreline; so a different chainset may well require a bottom bracket bearing with a different axle length.

Phew!....probably put you off for life!