123123user

I bought a bike at a lower price and it seems that some parts aren't Shimano-branded like its sprocket and derailleurs. I plan to buy the better parts so I can replace the generic ones. Can I just get that spare part and use it in the bike, or does it need to be compatible and the same with the already Shimano parts? I would try to look for any shimano derailleur according to bike transmission.

okane

Hard for me to understand your question(s) from what you have written.

I think you are asking if the drive train, i.e., shifter, chain rings, rear gear cluster (freewheel or cassette) needs to match or all be from the same group.

If you are using index shifters, the answer is generally yes but not always. If you are using friction shifters you have a much betteer chance of everything working properly.

You need to be more specific about your request: what bike, what components (model nos./name). Shimano makes an incredibly large array of components for everything from wally world bikes to high end bikes.

dabac

Bike parts are a lot more expensive when bought piecemeal than when bought as a complete bike, so thorough upgrades are usually a very poor idea financially.
Always try to buy a bike as close to what you want as possible from the start, to get the most for your money.
Assuming the parts work well enough for the kind of riding you do, don't obsess about branding. Ride and be happy.
What you can possibly do is a little "stealth" upgrading by replacing-with-better when parts fail or wear out.

123123user

Sorry, I'm fairly new to the assembly of bikes so I struggle a bit in finding the right terms for its components.

Well, yes I am asking if parts of another group could work interchangeably with another, if I were to replace my current one since its just a generic SunRun and I want to replace it with Shimano parts. Also, on the cassette,(also SunRun, but I'm thinking that I'll let it wear first before I replace it) "INDEX" is written on the biggest cog. Is that what you are referring to?

123123user

I've been itching to ride again since I use bikes to commute and ride with friends. I have an old bike but its parts are old and kinda hard to find replacement parts for, so I went on the other option.
Yeah, stealth upgrading sounds good.

dabac

What parts is it that you are struggling to find?
Bike parts tend to be a lot more generic than, say car or motorcycle parts.
So even if fully identical parts may no longer be around, functionally identical parts tend still to be available if you know where to look.

Although Uni-glide cassettes can be a challenge...

123123user

It's an old rigid bike with a cantilever brake, and one problem is that the brake pads are already smooth and its brake has a larger slot so I need to find the right pad with the iron that fits into the lock. Also, the gear's teeth are not sharp anymore you can't really ride properly.

Homebrew01

If you can post pictures of the parts you think need replacing, you might get better advice.

Andrew R Stewart 

Yes, there needs to be some compatibility maintained for the parts to 1- actually fit on the parts not being replaced (like a cog set being a cassette or a freewheel), 2- then whether the new parts will play nice feature wise (as in the same number of cogs being the same c-c spacing so that the indexed shifting is retained) and 3- some parts really should be replaced as a "package' so their interaction is problem free (as in a new chain not meshing with a worn cog set).

If you have access to a LBS I strongly suggest you go to them and BOTH get their advice and then BUY FROM THEM the parts that will work. I do agree with both dabac and Gabe in that the financial value of doing this might be debated and that photos would help us to help you better. Andy.

dabac

Smooth brake pads as such isn't much of a problem, if any.
The pattern on a brake pad is supposed to help clear away water (and any particles) from the rim, but I've worn any number of pads well beyond smooth w/o noticing the moment the treads disappeared.
IMO, you should be OK as long at there is rubber left to wear on.

The brake pad thing probably isn't an issue. Don't think I've come across any brake pad standard that has gone obsolete yet.
Gear teeth not being sharp is a so-so thing.
Sure, cassettes can wear to the point of not engaging properly with the chain, but "teeth not being sharp" isn't the thing to look for.

okane

Using proper terminology is vital. For instance as I previously stated, group usually refers to front and rear DRs, Chainrings, rear cassette/freewheel, and shifters. You can usually change groups successfully if all components are the same type, but you will could run into problems if you try to change a friction shifter group to an index shifter group. In this case at the least you would need to change cable housing also because index shifters require a "stiffer" housing to operate properly.

If you want to mix and match components from different groups you will more often than not run into problems. Yesterday I tried using a Sun Race index thumb shifter on a Shimano cassette. Didn't have sufficient index cable housing so I used brake cable housing and can only catch the top 6 or lower 6 gears of a 7 speed shifter. The cable flex was very visible.

Whether it would work with the proper cable is open at this point, but the bike is a cheapo so I'll just use a friction shifter I have because almost any brand/style will work. However in other mix/match situations I have had success.

For me, changing or interchanging parts is a hit or miss situation and I don't know for sure until I try. I'm using parts bin supplies so no money lost if things don't work.

If you are putting up some cash I suggest you first check with you LBS or on this forum for advice not only to see if it will work, but if the bike is worth the time, effort, and money.

By the way, index shifting is a system where the control has stops or clicks telling you that a new cog has been engaged. Friction shifting you engage cog by moving the control until you feel you have fully engaged a cog or chainring...no stops or detents, you do it by sound and feel.