Do I need to use the same size rings when replacing chainset?

[djmagnifique]

Hi, I need to replace the chainset on my mountain bike. It was a cheap bike that is only used for traveling to work and back. The rings can't be changed seperately so when I change the whole chainset will I need to use one that has the same number of teeth (currently 24/34/42) or can I use one that has a differnet numbet of teeth (like 26/36/48)?

Cheers.

 

[Smokin Joe]

You can use any size rings you like, but going from a 42 to a 48 the chain will probably need an extra link.

 

[Rickshaw Phil]

Hi and

Yes you can change the rings if you want to. My knockabout bike (a cheap Hawk Trakatak) came with the same size rings and changing them to 28-38-48 was one of the first updates I did to get a little more speed out of it.

You'll need the chain to be a bit longer but if you're replacing the chainset due to wear I presume you're aiming to fit a new chain anyway.

 

[Racing roadkill]

Make sure the inter ring spacing is the same. 9 speed 10 speed etc.

 

[gbb]

If the spacing between the chain stay and the existing chain rings are tight, putting a 48 on might then foul the chain stays.

A wider BB with the new chainset might solve it, but equally might effect the chainline.

Note my emphasis on might. I've done this before and had a problem getting the 48 on without fouling. Yours might be OK.

 

[djmagnifique]

Thanks for the quick replys everyone. So should I be buying something like this to replace my existing chainset? https://www.decathlon.co.uk/altus-2...802_ii__vi__&gclid=CLHRw9Ly79MCFa677QodLuYMOA
My bottom bracket looks like a square taper style.

 

[si_c]

Also if replacing the chainset you may need to change the bottom bracket, if the new one needs a longer axle you could find the rings scraping the chainstays

 

[djmagnifique]

Not really wanting to change the chain as well with it being such a cheap bike and I'm only hoping to get another 12-18 months use out of it before upgrading. So if i look for a chainset with the same tooth count on the big ring I will be ok. I have seen some with 44 teeth on the big ring, would that be ok or would it need a change of chain as well?
The bottom bracket is a square taper type.

 

[Milkfloat]

Plus you would most likely need to adjust the front derailleur.

 

[djmagnifique]

After having another look over my bike i've noticed that the jockey wheels look to be quite worn as well. One is pointy and the other looks like shark fins. Could this cause the chain to slip when moving off from stationary?

 

[Tim Hall]

After having another look over my bike i've noticed that the jockey wheels look to be quite worn as well. One is pointy and the other looks like shark fins. Could this cause the chain to slip when moving off from stationary?

Very unlikely, but it is a pointer to general wearing out/lack of maintenance which will be the thing that causes slipping when moving off.

 

[overmind]

After having another look over my bike i've noticed that the jockey wheels look to be quite worn as well. One is pointy and the other looks like shark fins. Could this cause the chain to slip when moving off from stationary?

I would say no since they are not driving the wheel. At worst I would have though they might just not turn as well (more friction). I changed mine when they were in that state however (I cannibalised an old deraileur off a cheap bike and used the jockey wheels from that).

 

[Rickshaw Phil]

Not really wanting to change the chain as well with it being such a cheap bike and I'm only hoping to get another 12-18 months use out of it before upgrading.

Since you've said that you need to replace the chainset and have also asked a question regarding the chain slipping I think it would be fair to presume that the chain is no longer in good condition. Don't skimp - the chain is a consumable item.

It's very likely if the drivetrain is worn to the point the chain is skipping that the block/cassette is worn out too.

My experience of cheap bikes is that the components tend to wear badly. What is the bike?

 

[djmagnifique]

Since you've said that you need to replace the chainset and have also asked a question regarding the chain slipping I think it would be fair to presume that the chain is no longer in good condition. Don't skimp - the chain is a consumable item.

It's very likely if the drivetrain is worn to the point the chain is skipping that the block/cassette is worn out too.

My experience of cheap bikes is that the components tend to wear badly. What is the bike?

It's an 2015 Apollo Evade bought from Halfords, I bought it as a quick fix as the lad who used to give me a lift to work got fired and i'd get no overtime unless I could get myself into work.

Looking at the cassette there doesn't seem to be any visable wear on the teeth. Today I did try setting off on the small ring, which I never use, and it slipped on that as well which made me thing it might be the jockey wheels.

 

[Ajax Bay]

I need to replace the chainset on my mountain bike

You haven't said why, which might help you/us.

Make sure the inter ring spacing is the same. 9 speed 10 speed etc.

The chainset does not have to be speed specific (eg 7 speed, 8 speed): one either side is fine so do not heed this advice. The OP's Apollo Evade has 21 gears so is a '7 speed' system

you may need to change the bottom bracket

'May do' . Mitigation: Don't get a new/secondhand crankset that needs a different axle length.

the jockey wheels look to be quite worn as well. One is pointy and the other looks like shark fins. Could this cause the chain to slip when moving off from stationary?

This is unlikely to be what's causing the slipping (skating).

the thing that causes slipping when moving off

As @Tim Hall says, it sounds very like the OP has worn his chain which has elongated, thus also wearing his cassette which results in the chain skating over the rear sprockets when the OP puts the power down eg from a standing start (uphill?). The jockey wheels are innocent OK!

Looking at the cassette there doesn't seem to be any visable wear on the teeth

You can't tell by looking that the cassette is worn. When you experience skating (which you are) you know it's worn.
Unless there is a good reason to get a new chainset (see my first point above), spend your money on a new cassette with an 11 tooth smallest sprocket, if you desire more 'speed'. This is much more economic (especially as you're going to have to anyway, or put up with skating which will sooner or later result in 'saddle/contact point damage'). Dropping from a 12t to an 11t will give you 8.3% more speed in your top gear (at the same cadence). Changing from 44t to a 48t large chainring will give you 9.1%. This links to a 7 speed 11-28 cassette (for your Apollo Evade)(£12) and a chain will cost maybe £12 [less £5 OFF CODE = ECWJ2R *Minimum spend of £30.] I will guess that you'll need a bike shop to fit these, so go along and ask.