Sprocket Chainring What is a "cassette cog" on a bicycle? Need to adjust front derailleur?
I just bought a new Trek "Hybrid" bike for commuting to work. The town where I bought it is a 90 minute drive. As soon as I tried out the bike on hills, it became evident that it would not shift into the lowest gear possible for hill climbing because the chain will not engage the smallest front chainring.
I want to adjust it myself, but I am not certain of the following instructions, as taken from http://www.bike-manual.com/brands/trek/om/hybrid/index.html -
"- Front derailleur clamp
1. Shift the chain onto the smallest front chainring and the largest cassette cog."
I have never heard the terminology "cassette cog" when speaking of bicycle parts. From the context of the sentence I am guessing they are referring to the multiple gears/sprockets lateral to the rear wheel axel, but the name "cassette cog" just does not seem to fit this part of the bike. Why is it called a "cassette" ?
It's called a cassette because the whole cog set is a complete assembly that slides off the hub. The cassette can be dissassembled, depending on the model and manufacturer, and therefore specific cogs or clusters of cogs can be replaced as they get worn.
In the old days, the cogset was similarly attached to the free wheel, which contained the ratcheting mechanism. This freewheel then threaded onto the rear hub. Today, the ratcheting mechanism is integrated into the hub assembly. It's a much better system since the whole assembly can be rebuilt, as opposed to the old freewheels which you could replace the cogs on, but rebuilding the ratchet mechanism was exceptionally difficult.
One word of advice: IF convenient, take the bike back where you bought it and have the mechanic do the adjustment. If the bike is new, they should do it for free, and ask to watch.
If the shop is not convenient, the one thing you need to watch out for is backing off the small chainring stop screw too far. This will result in your chain dropping off on the inside. The danger here is two-fold:
You will suddenly be spinng the pedals but not going anywhere which may cause you to lose control,
The chain may become jammed in between the small chainring and the crank arm spindle shell (aka 'bottom bracket shell'). The worst case here is that the chain may become damaged and it may even be necessary to remove the crank arm to free the chain.
When adjusting the screw, test ride the bike on level ground and use light pressure on the pedals. Make sure not to back off the stop screw any further than necessary for proper shifting. Once the flat ground shifting works, try it on a hill. The added tension on the chain may require you to back off the screw slightly more, but never adjust in more than 1/4 turn increments.
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What are the differences between sprocket/chainring combinations?
I'm a fixed gear riding courier based in London.
I'm just wondering what the advantages and disadvantages are of having a smaller / larger combination are?
For example: both 36:12 and 48:16 equal 81 gear inches, so what differences are there?
I'm bearing in mind things like wear (obviously the larger is better for that one) but also if it effects anything like tricks (wheelies, fakies), ease of climbing, etc...
Please help me out!
If you're running the same ratio, but with different gears, it just comes down to two main differences in the forces put on the chain/components:
Larger rings/sprockets will generally increase the longevity of your chain and sprockets, and reduce chain tension a bit. The caveat is that you may need a higher BB to compensate for the reduced clearance of the larger chain ring up front.
Obviously, the opposite holds true for smaller ring/sprocket combos.
As far as tricks go, generally I see people with smaller chain rings and smaller ratios doing lots of tricks - I think they take the que from BMX in this regard, since you can more easily torque a small ring up front an pop wheelies. In my experience, it's more responsive - Though, you will have more movement required (fraction of a pedal stroke) when doing track stands and such.
If your main use is for your courier duties I'd go 48:16 on a higher BB frame. You can also run a smaller cog on a flip-flop hub if you ever need to cover some ground faster. If you're doing tricks, consider 36:14 or similar. Really it's a matter of personal opinion though - If you've got the $$, get 2-3 fixies if you're really into them.
If you have brakes on your bike, you don't have to use them. Especially in flat cities like London. But having no brakes means that you never have the opportunity to use them if you ever need them.
Riding brakeless is no good for your knees either.
If you do decide to ride brakeless you'd better hope that your knees can stand the constant opposing force, and that you never end up in a situation where you need more friction to stop you than that between your back tyre and the road. And you'd better pray that your chain never snaps and never comes off the sprocket or chainring, and be prepared to make 'alternative arrangements' if that does happen. 1/8″ chains are hard to snap, and with a straight chainline and the correct tension it's highly unlikely to pop off the gears. But it happens.
Brakeless is never safer.
If you have brakes on your bike, you don't have to use them. Especially in flat cities like London. But having no brakes means that you never have the opportunity to use them if you ever need them.
Riding brakeless is no good for your knees either.
If you do decide to ride brakeless you'd better hope that your knees can stand the constant opposing force, and that you never end up in a situation where you need more friction to stop you than that between your back tyre and the road. And you'd better pray that your chain never snaps and never comes off the sprocket or chainring, and be prepared to make 'alternative arrangements' if that does happen. 1/8″ chains are hard to snap, and with a straight chainline and the correct tension it's highly unlikely to pop off the gears. But it happens.
Hutch Sprocket Chainring –