LeithB64

Hi, new to this forum. I recently got a bike from a friend for free, and its cassette and chain are corroded and kind of worn. Since I’ll be replacing them anyway, I wondered if it would be a good idea to get a cassette with smaller sprockets, because on my old bike that I’ve had for years, I regularly bike on the highest gear, and I’d like to have some higher gears so I can go faster. Wanted to get some advice, though, before I did it. Mainly: 1) Should I do it 2) will this require any adjustment/replacement of the bikes derailleur 3) Any suggestions for the cassette? 4) Would it be better to get the same size rear cassette and larger sprockets for the front?
Edit: I fixed my mistake in saying that I wanted larger sprockets and added a fourth question

Koyote

1) "Larger sprockets" are actually lower gears, which are useful for climbing steep grades.
2) At minimum, you will need a longer chain if you have larger sprockets, but it seems like you need a new chain anyway.
3) I have no suggestions for the cassette, since I don't know what's currently on the bike -- and it doesn't seem like it'll do you any good, anyway. (See item 1, above.)

You should probably take the bike to a shop for advice. They can look at what you've got and make suggestions. They've also got the tools and knowledge to make any desired swaps.

soyabean

That's why you got a bike for free.

You asked for an opinion, and in my honest opinion is to return/re-gift/curb toss the free bike and buy something with some higher gears to go faster.

alcjphil

Without knowing more about the bike that was given to you it isn't possible to know if it is even worthwhile to repair it. The "fastest" gear on your bike is the smallest sprocket. not the largest one.Bigger sprockets are used for when you are climbing hills or riding into gale force winds

noimagination

Speculating here, but: I'm thinking that you may be used to a bike with numbers on the shifters, arranged so that the higher numbers are for higher speeds; and I'm thinking that you've assumed that higher numbers on the shifter indicator mean larger cog on the cassette. If the previous is true, then you are correct that, for the left-hand shifter (assuming you have two shifters), larger numbers = larger chainring (the "sprocket", the rings the chain goes over on the front that are attached to the pedals). However, if you look in the back (cassette) when you shift using the right-hand shifter, you will see that, on the right-hand shifter, when you shift to a bigger number on the gear indicator the chain moves to a smaller cog on the cassette, not to a larger one.

It's a bit confusing, so errors of this type are pretty common for people new to cycling to make, or even for long-time cyclists who do not pay attention/do not work on their bikes/have not thought about how the bike works/don't care just want to ride.

Kai Winters

Replace the chain and cassette/freewheel...
What do you consider 'faster'??? are you in the bike's largest gear...fewest teeth cog in back and big chain ring and you are spinning out this gear...meaning more than 120rpm...if not you are just plodding along at a fast pace for you and a larger gear won't help you go much faster.
What kind of bike are you talking about...so little info considering what you want makes it near impossible to get useful suggestions...

Iride01 

Cassettes and chains actually can handle quite a bit of rust and still work. Many times it's only surface rust and for the most part only looks bad. Even a chain rusted so bad that the links are hard to flex or completely frozen together can be freed up with some lube and a little effort. Sure the chain might not last as long. But any time it lasts is miles you can go before starting the clock on the new chain.

In order to really decide if you can go bigger or smaller with cogs and rings, we really need to know what it is that's on your bike. Not just the name of the model, but the actual part numbers and versions. 105, DuraAce and etc don't tell us anything much.

And it's really a better discussion for theBicycle Mechanicssub-forum. Though quite a few of the actual bike mechanics and DIYer's come here too. But not all of them.

Pic's might help too. You can't post them in the thread till you get 10 posts and a day. But you can upload them to theGallery here on BF and just let us know to look for them.

Welcome to BF.

LeithB64

I did know that; I just sent this at like midnight last night and I was tired and stupid(er than usual). I do know that smaller is actually faster; I just made a mistake in my post.

alcjphil

Smaller isn't necessarily faster. To be able to go faster you have to be able to turn the pedals at the same speed against harder resistance. Sometimes, you will actually slow down because you don't have the physical strength to overcome that higher resistance

LeithB64

Yes, this bike has the same size sprockets as my older one, and on that one I use the highest hat almost exclusively, so this is also a way to not only work up to higher speeds, but also work up more muscle by biking on higher gears.

alcjphil

How many teeth does the smallest sprocket have? How many cogs? It may well be that the bike has a freewheel and not a cassette. In any case, the smallest cogs are often the smallest that will fit on that freewheel or cassette.

beng1

Usually with larger sprockets you just need a longer chain. It is better to have a larger front chainwheel on a road bike because it puts less strain on the chain so everything lasts longer. Do a Google search for a website which tells you how fast a bicycle goes with a certain pedal rpm and certain sized sprockets, that way you can plug in how fast you want to pedal and it will show which combinations of gears will give you the speed you want at that pedal rpm or cadence.

Russ Roth

As others have mentioned, this will require knowing what you have. If a cassette which is some 7sp, virtually all 8sp, and all 9sp then an 11t cog is the smallest size possible. If a freewheel, which will be most 7sp and virtually all 6sp, then a 14t cog is the smallest you can go. In general, bikes will come with an 11t if cassette and a 14t if freewheel and the only thing you can really change is the range from there.
Not typically, though if you buy something with a wider range, meaning a taller rear sprocket for the low gear, you may have to adjust the B limit screw and replace the chain. Anything the same size or a smaller range shouldn't be an issue.

Is it really a cassette or a freewheel and how many speeds?

Potentially, swapping chainrings can can also change the whole range but front derailleurs can only shift so wide a jump between the smallest chainring and the largest so you might have to change all of them to maintain the front shifting. Since you're changing the chain anyways you'll also need to size it to fit the larger rings.

VegasTriker

First off it will help if you post more information about the bike. Is the brand and model still on the frame?

The correct name for the "sprockets" at the front of the bike are called chainrings. Count the number of teeth on each of the chainrings and post that information. How many choices do you have in the rear. Take the time to count the number of teeth on the inner sprocket (low gear) and on the smallest sprocket (high gear) and post it. Then use one of the gear calculators to get the current gear range https://www.sheldonbrown.com/gear-calc.html or https://mike-sherman.github.io/shift/. You will need to enter wheel size (on the side of the tire) and crank length (most bikes are 170mm). I like to have the output as gear inches, a whole number easier to compare. It will show you the exact effect of going with a larger chainring.

I'm almost willing to bet your bike is set up for off-road use where you need low gears more than high gears. The largest chainring on my Cannondale SM800 mountain bike is 48 teeth. I don't remember the gear range but it is significantly lower than the gear range on the road bike I used to own with a 52 tooth largest chainring. If you are using knobby off-road tires, switching to smoother city tire might help with the speed.

You can buy a chain for a bike with 6, 7, or 8 speeds (one size fits all three) really cheaply but you will need a chain tool to shorten the chain. A standard chain is usually 116 links. If your bike is older it probably has 8 speeds in the rear for this type of chain. A generic 8 speed chain is just $10 https://www.ebay.com/itm/283950446056 or the chain brand and type I prefer (KMC 8X.93) is $14 https://www.ebay.com/itm/266310389028. I've used the KMC chains for years and thousands of miles without ever breaking one.

Calsun

Spray the chain with lubricant and take the bike for a ride in varied terrain so you can decide what to change. I like to have the larger front chainring in use most of the time and make gear changes with the rear cassette. On a steep long grade I switch to the smaller chainring and like to have the rear cassette in the middle of its range so I can go to lower gears if needed.

Depending on the largest cog on the current cassettee and what you decide to replace it with, there may be a need for a new derailleur with a longer of shorter cage.

Trakhak

Thinking that your gearing is what limits your speed is a common error. Extending some observations someone made earlier, so they don't get lost in the deluge of replies:

The fastest and strongest bike racers spend very little time in their highest gears, which are generally used only in mountain descents and in end-of-race sprints.

Guaranteed: race against a decently strong bike racer, with you in your highest gear and the bike racer confined to using sprockets in the middle of the cassette, and you'll be left in the dust.

I was only a middle-of-the-pack racer, but I always enjoyed having some would-be racer out on the road pass me while he was lugging along in his highest gear, because that was license to kill (his dreams, that is).

Looking to build leg muscle? Use a leg press machine or do squats with free weights. It's impossible to apply much more than your own weight to the pedals of a bike, so riding in the hope of building muscle is a waste of time.

Proof: look at the guys who are dominating the Tour de France this month. They range in build from moderately muscular to skeletal - and one of the most skeletal is currently leading the race. Legs like pipe stems, arms like pipe cleaners. (Fun fact: Skeletal Guy won last year's Tour de France.)

If you're like most newcomers to cycling for fitness, you won't believe any of the above, and you'll continue to try to figure out how to get higher gears. Good luck.

79pmooney

No. Many 6 and 7 speed FWs come standard with 13 tooth cogs and a some with 12 teeth. (Most of my old 5-speeds were 13 tooth.)

That said, riding in huge gears is not a good formula for developing real speed. If it were, racers would have been doing that for the past century, Instead, they put in long miles at far lower gears, developing a good spin and concentrate on developing power vs the high gear approach which might develop strength. (Power is RPM times pedal force.) Rule of thumb we all heard in racing circles - if you can match your opponent's speed at higher RPM, when crunch time comes, you will be able to put it in the big gear and beat him. Yes there are big gear exceptions. But there are far more riders who look strong all race but don't finish in the top 10.

Russ Roth

Not in the last 20+ years, probably closer to 30. From what I can recall of trying to find quality freewheels for older road bikes when I started fixing bikes, Shimano hasn't made one with smaller than a 14t since at least before 2000, and at that time they were the only company making a somewhat decent one. We were sending people to ebay if they wanted one. I had a shimano 600 sis 6sp freewheel with a 13t that I gave to a coworker who couldn't find anything and I haven't worked in that shop since 02. So yes, you're right, doubt it has any bearing on my reply or what the OP is looking for unless you want to send him to ebay to find a relic that's probably worth more than the entry level bike that was passed off to him.

79pmooney

I just went to the SunRace website. They show 7-speed FWs in 13-25, 13-18 and 13-34. 8-speeds in 13-28 and 13-32. 9-speeds in 11-13 and 13-32. I haven't purchased a SunRace in a while. The ones I had used a slightly unusual cog sequence that bugged me a little, the shifting (friction or ratchet on all my bikes) was a little rough but they never did the Shimano "wander" between cogs after a poor shift. Also seem to run forever. Looking at the website I see SunRace has been busy. Looks are updated, tooth profiles look modern and cog choice are logical. I cannot see a reason not to run them on a C&V unless chrome is not an OK look.