Classic & Vintage - I was told there would be no math-- an upgrade question

I am replacing the 12-23 8 speed hyperglide cassette with a 12-27 9 speed hyperglide cassette.

I was able to put the new cassette on the hub without difficulty. I was worried that it wasn't going to fit, but it seemed to go just right.

The next task is to replace the chain. I don't know anything about chains. But it seems to me that the new 9 speed chain should just be 4 lengths longer than the old 8 speed chain.

Is that right?

Jared

The bike at issue:

http://i624.photobucket.com/albums/tt327/oldarizona/Paramount/DSC_0262Large.jpg

http://i624.photobucket.com/albums/tt327/oldarizona/Paramount/DSC_0260Large.jpg

Hmmm, upon further review, 53/39 and 12-27 give me a chain wrap of 29. Velobase says the max chain wrap is 26. Is that going to be a problem?

Jared

Well, not quite. One usually uses as long a chain as possible, but short enough to make small/small (39/11 ?) combination work. The jockey wheels should be almost horizontal, but not quite. This is not a combination you would normally use, but should not cause the derailleur to wrap-around or self-destruct. The lower chain line should not be touching the upper jockey wheel.

With this much chain, you should be able to use the largest cog the derailleur supports. Again, you should also check big/big (52/27 ?) combination, to make sure the derailleur does not extend with too much stress.

These are nice looking cranks, what are they?

Those aren't pics of the setup in question...

Forget the math....make the chain as long as possible. If it sags in low/low remove a link.

Hello may I ask a question? (or two) does this bike index shift? you do understand that the reason the 9spd fit your freehub is that the spacing is different. if you only have a 8 speed shifter it may not shift.

those cranks look like Topline cranks maybe from the early '90s?

Those aren't pics of the setup in question...

Forget the math....make the chain as long as possible. If it sags in low/low remove a link.


Also, test big/big gently after you get low/low set right. It's hard to say sight unseen that there will not be a problem. If there is a big problem, it could pull the dropout out of line.

There is a mathematical solution, but I don't think it's better than a careful eye for good operation.

Math? I prefer trial and error.

I go to big/big and make sure I've got clearance and my RD isn't doing the horizontal bop. I run it several times to make sure it's not fooling me. Under load and on a rack can be different...

Then I go to small/small and make sure it's not flopping around. And remember, unless you have a half-link, they come out in twos.

Those aren't pics of the setup in question...


Those pics are the original 12-23

Jared

Hello may I ask a question? (or two) does this bike index shift? you do understand that the reason the 9spd fit your freehub is that the spacing is different. if you only have a 8 speed shifter it may not shift.

those cranks look like Topline cranks maybe from the early '90s?

I have a set of 9 speed dura ace bar ends to replace the current bar ends.

And yes, they are topline cranks.

Jared

Can any help me on the chain wrap issue? Is the max chain wrap for the 600 I have really 26? As I said, I think this would be 29. I also have a 12-25 cassette, but even with that chain wrap would be at 27?

And another questions--what is the chance that the current high/low and B-screw adjustments will work as is?

And one more-- I also have a DA 7700 RD. What is the max chain wrap for that? It is not in velobase.


Jared

Since the chain wraps roughly halfway around the cog, adding four teeth to the largest cog implies that you may want to add two half-links, i.e., 1", to the chain, but this assumes your current chain is correct for your current setup.

Derailleur chain takeup/wrap capacities are generally conservatively specified, so you can usually fudge by a few teeth.

I usually wrap the chain around the big chainring and the big cog NOT through the rear deraileur, pull them together, then add a link. Hasn't failed me, and I've heard of others with the same success. So, basically, if you put a new chain on it. Wrap it like that, and then cut it a link past where they "connect".
-Gene-

I usually wrap the chain around the big chainring and the big cog NOT through the rear deraileur, pull them together, then add a link. Hasn't failed me, and I've heard of others with the same success. So, basically, if you put a new chain on it. Wrap it like that, and then cut it a link past where they "connect".
-Gene-

Yup, this method has worked well for me.

Ok, I decided to play it safer and put on the 12-25 cassette. That should be good enough to avoid any chain wrap issues.

Jared

I usually wrap the chain around the big chainring and the big cog NOT through the rear deraileur, pull them together, then add a link. Hasn't failed me, and I've heard of others with the same success. So, basically, if you put a new chain on it. Wrap it like that, and then cut it a link past where they "connect".
-Gene-

That is basically the same instructions found in the SRAM 971 chain. I will give it a shot-- but I must say that my gut instinct is that it would not leave you with enough chain-- because basically it only gives you two extra links to compensate for it going through derailleur. It seems like it would need more.

But like I said, I will give it a shot.

Jared

Well, with that method you won't be able to use your big-big combination and possibly the one before it. You're not supposed to anyways, but still. Don't worry so much about chainwrap. Worry more about derailleur alignment/position and where it stops on both ends of the gears. It's not rocket science, and your pulley cage isn't carbon fibre so it shouldn't spontaneously 'splode.
So, just do it and ride.
-Gene-

Why make a mountain out of a mole hill.

Install the chain. If.......

Its too long (sags in low low) take out a link.
Its too short (cant go into big big) add a link.

Ok, I followed the instructions, and it seemed to work out just fine. It works on big big, and I don't think there is too much slack on small small.

I did my best to adjust the index shifting of the new bar end, but it is not quite as precise as I would like it to be. I wonder if I could use new cable housings.

Jared

I usually wrap the chain around the big chainring and the big cog NOT through the rear deraileur, pull them together, then add a link. Hasn't failed me, and I've heard of others with the same success. So, basically, if you put a new chain on it. Wrap it like that, and then cut it a link past where they "connect".
-Gene-

This is the correct method of determining chain length.