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ChainRing toothcount/cassette compatibility

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ChainRing toothcount/cassette compatibility

Old 09-23-08, 11:53 AM
  #1  
sandman007
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ChainRing toothcount/cassette compatibility

Okay I have been reading up on Chainrings and "gear inches" but for the life of me I don't understand the "Nomenclature" of gearing. So I have no idea what I have. 3-digit numbers, teeth, cm, mm, inches... etc...
Recent discovery on my bike is it used to have an 8-speed cassette and when the one that is currently on it failed (which was a 7-speed) put on by previous owner, I found that I would like to replace it with the correct one. Little did I know that the "correct one" could be one of many.
So throw me a bone and help me out in replacing the current 7-speed with a 8-speed that is compatible with this chainring tooth count.



I can handle the mechanical/manual labor area, I'm just new to this gearing area.

Last edited by sandman007; 09-24-08 at 08:52 AM. Reason: Update picture to 24-42 Chainrings
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Old 09-23-08, 01:15 PM
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this site might help
http://www.srsuntour-cycling.com/SID...gory&tnid=1652
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Old 09-23-08, 01:17 PM
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http://www.srsuntour-cycling.com/SID...gory&tnid=1652
this site might help you
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Old 09-23-08, 01:37 PM
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Basically the most important number you'll need is the size of the largest cog, since you need a low enough gear to get up your steepest hill. Worst case scenario-
That may limit you to fewer choices for a smallest cog.

what kind of terrain? Totally flat slight hills, steep hills....

That said, your RDER may limit you to a 28T cog (or 30 in reality), if it's a "road type" DER. Only a problem if you need something like a 32-34T largest cog.

Other factors will also have an effect such as-
Tire size/weight/diameter/tread
crank length

BTW, 43T would be a very odd size. 42 or 44 would be more likely.

EDIT-
Looked at the pic again and realized you have a triple!
Since your SMALLEST ring looks like it's 22-24T, base your largest cog needed with that ring.
My bike is a triple (28-38-48) with short cranks (160MM) and I ride on flat ground.
I use a 13-24 and the middle ring almost exclusively and it works for me. I have 60 year old bad knees, so I wouldn't say what will work best for you.
I've done a LOT of experimenting with various cog combinations and crank lengths to get where I'm at. You'll almost always second guess yourself some, no matter what you come up with!

Last edited by Bill Kapaun; 09-23-08 at 01:45 PM.
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Old 09-23-08, 02:06 PM
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Generally 7-speed cassettes and 8-speed cassettes are not interchangeable, are you sure that's what happened? Have you count the number of cogs (rear sprockets) on your cassette? Is it possible that you have a freewheel instead of a cassette? Check the descriptions of the differences in cassettes and freewheels at http://www.sheldonbrown.com.
What type of shifters do you have? If they are indexed then they must match the number of cogs on the cassette or freewheel.

Al
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Old 09-23-08, 02:34 PM
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Current Rear sprocket in question. it says dnp ly-1008 kf index (I don't know if this is the correct one or not) the bike was a hand me down. That's why I'm starting the research from the Chainrings. It appears that the larger sprocket has 28 teeth and the smaller one has 13. (13-28)


Shifters are numbered 1-3 on the left and 1-8 on the right... Says Sachs on it.


Crank length is stamped 170 by the pedal.
Tire size is 26".
I weigh about 215 and I'm about 5'9"...
My normal terrain for biking is desert/highway not too much uphill mostly sandy/gravel trails or dirt roads.

Last edited by sandman007; 09-24-08 at 08:59 AM. Reason: update in teeth counts/shifter info/crank info
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Old 09-24-08, 09:30 AM
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Okay here's a quick summary on what I know now...
The bike has a 24-42 chainring, 13-28 Freewheel and the crank is stamped with 170 so I'm guessing the length is 170mm. It has Sachs shifters 1-3 on the left and 1-8 on the right. The reason I say freewheel after reading lastnight and looking at numerous pictures/descriptions is that a cassette... if you take off the lock ring it will come off as 1 ***t. The freewheel on the other hand if you remove the lockring you will be able to remove the sprockets individually. Correct me if I'm wrong. Now the question remains... with this new info. Is the correct 7-speed freewheel on there or is it supposed to be an 8-speed freewheel in order for the bike to be a 24 speed?

thanks to the people that participated so far the links to suntour helped, the archive only goes to 2003 so I e-mailed them for more info... the sheldonbrown site is quite informative & Bill K. after researching last night & reading up on this. I understand what you are saying, now. thanks again.

Last edited by sandman007; 09-24-08 at 09:37 AM.
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Old 09-24-08, 11:16 AM
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I can't find any info on this bike on the web, I got the owner's manual from Pacific Cycle but it covers all bikes. The diagram shown of the bike is pretty informative too. Pacific Conquest SE 24 Speed is evil.

Last edited by sandman007; 09-24-08 at 12:36 PM.
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Old 09-24-08, 03:02 PM
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" Shifters are numbered 1-3 on the left and 1-8 on the right... Says Sachs on it."
Then you should have 3 chain rings and 8 cogs.
AN 8 speed is almost always a cassette, but 8 speed Freewheels DO exist.
You can tell the difference between a Freewheel & Freehub (cassette) here-
http://sheldonbrown.com/free-k7.html

Another way to tell is to look at the spacers between the largest 4 or 5 cogs. On a cassette, they will ALL be the same size, while on a FW, they get larger as the cogs get larger. (the smallest cog or 2 will have a built-in spacer on a cassette, so that will vary)
Notice the cassette has 3 rivets that can be removed and then the cogs come apart.

Something I would check is if the front & rear rims match. Somebody may have taken off the 8 speed set up and swapped in a 7 speed???? It's illogical to swap on a 7 speed cassette to a bike with 8 speed shifters!
The cog spacing is different between 7 & 8 speeds, so 8 speed shifters will NOT move the RDER the proper amount per shift.

aLet us know if it's a Free Wheel or Free Hub.
There are some other potential problems I see, but we need to pass this "fork in the road" first.
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Old 09-29-08, 10:13 AM
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Hey the spacers are the same size. See image...

http://i204.photobucket.com/albums/b...Cassette01.jpg

And the smallest cog does double as a spacer and a sprocket.

The front and the rear rims are the same brand "Pacific Cycle" or "PC".
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Old 09-29-08, 10:18 AM
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so someone did change it from 8-speed to 7-speed...
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Old 09-29-08, 11:14 AM
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Originally Posted by sandman007 View Post
Hey the spacers are the same size. See image...

http://i204.photobucket.com/albums/b...Cassette01.jpg

And the smallest cog does double as a spacer and a sprocket.

The front and the rear rims are the same brand "Pacific Cycle" or "PC".
There are 3 different diameters (size) between the 5 largest. FREEWHEEL!

Pacific handles a lot of different brands, from Wal Mart's Roadmaster , Mongoose, Schwinn Pacific and who knows what else for sure.
Somebody has either swapped shifters or wheels.
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Old 09-29-08, 01:41 PM
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Originally Posted by Bill Kapaun View Post
There are some other potential problems I see, but we need to pass this "fork in the road" first.
So what else do you see?
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