Replace chain with new cassette?

[nameused]

Hello.
I'm replacing my the cassette and I've been reading everywhere that I should replace my chain with it. Is this necessary? If so why?
Thanks.

[trevgbb]

Depends on why you are replacing it, if it's due to wear, the chain and possibly the chainset (look for worn or hooked teeth) may also be worn out and you may need to replace these also.

[nameused]

The reason I'm replacing it is because I'm getting a new wheel for my bike that has a cassette rather than a freehub. I've had the chain on there since I bought the bike about a year and a half ago.

[trevgbb]

New wheel? does it have the same no. of gears, are they the same top ring and is the OLD the same?
If so you should be able to fit out of the box but you won't know if the chain will work until you try.

[nameused]

I'm changing from a 7 speed to an 8 speed and both have the same top ring, 34 teeth.

[cyclerUK]

(10-30-2010, 04:50 AM)trevgbb Wrote:  New wheel? does it have the same no. of gears, are they the same top ring and is the OLD the same?
If so you should be able to fit out of the box but you won't know if the chain will work until you try.

Do you have an 8 speed changer?
If you still are using the 7 speed then it won't match!.
You will need an 8 speed changer for an 8 speed cassette unless you use friction shifters.

If you use an old worn chain on a new cassette, it will jump over the teeth when under pressure. An old chain stretches and doesn't drop into the well of the teeth of the new cassette..

---

Just on a point of terminology. A cassette is the set of cogs that fit on a "freehub".
The older type of cogs that screw on is called a freewheel.

[trevgbb]

before spending a lot of money increasing the no. of gears (and yet keeping the same ratios?) read this article;
http://www.jakesbikes.co.uk/content/348.php
I agree with every word.

[nameused]

(10-30-2010, 05:30 AM)cyclerUK Wrote:  Do you have an 8 speed changer?
If you still are using the 7 speed then it won't match!.
You will need an 8 speed changer for an 8 speed cassette unless you use friction shifters.

If you use an old worn chain on a new cassette, it will jump over the teeth when under pressure. An old chain stretches and doesn't drop into the well of the teeth of the new cassette..

---

Just on a point of terminology. A cassette is the set of cogs that fit on a "freehub".
The older type of cogs that screw on is called a freewheel.

I'm planning on getting an 8 speed changer, but until then a 7 speed changer should still be able to get me through 7 gears in the back correct?

(10-30-2010, 12:30 PM)trevgbb Wrote:  before spending a lot of money increasing the no. of gears (and yet keeeping the same ratios?) read this article;
http://www.jakesbikes.co.uk/content/348.php
I agree with every word.

Well the original freehub was the shimano hg-50 megarange 7 speed, which i loved having the huge jump up to the 34 tooth gear when climbing up steep hills. Since I bought the bike they've discontinued that one and have the hg-40 megarange 8 speed cassette. I love the range of gears on it so I wanted to keep it.

[cyclerUK]

(10-30-2010, 12:30 PM)trevgbb Wrote:  before spending a lot of money increasing the no. of gears (and yet keeeping the same ratios?) read this article;
http://www.jakesbikes.co.uk/content/348.php
I agree with every word.

jakesbike has a point about duplicate ratios.
But to use a lesser number cassette, and to keep a reasonable cadence going, would entail jumping from one chainring and back again.
Or you would use a close ratio block and not have the range of gears required for a varying landscape.
If you had the range of gears (say 11-30) that's common on todays mountain bikes, with a 5 speed block, then the jump between sprockets would be quite large. Don't get me wrong though as I still use generally 8 speed cassettes with triple and double chainrings.
I do have one road bike with a 10 speed cassette (12-25) and compact (50/34T) chainset. I don't find it of any advantage compared with my 8x3 setups.