13/23 to 14/28 rear derailleur question

[Jamin]

Hi,

So today I ordered some new wheels for my 700c conversion. The wheels come with a 7 speed freewheel which is just what I need. However, my current cassette is 13/23 and the new one is 14/28. What adjustments will I need to make to the rear derailleur so that it will shift smoothly and accurately on the new cassette.

Jamin

[DaveM]

Probably not much, but it depends.
First, you will have to adjust limit screws and cable tension even though they're both 7 speed.
You might need to lengthen your chain so it can handle the 28. Unless the one you have now is pretty new, usually a good idea to change chain at the same time as the cassette anyway.
You need to check if your rear derailleur can handle a 28 tooth. You can try looking up the make/model specs and see what it's rated for. Or you can just put the wheel on the bike and see what happens. But some very short cage road derailleurs won't work well on a 28.

Just a side note that if you're putting smaller wheels (27 --> 700) and larger rear gears on the back, you're going to have noticeably lower gear range than you did before.

Finally, make sure if you have a 7 speed "freewheel" or "cassette". The difference is important and you will want to know what you have. http://sheldonbrown.com/free-k7.html

[Jamin]

Hi Dave. Thanks for your reply. It is a freewheel. I thought they were called cassettes as well. Lol

Lower gearing is why I bought the freewheel. The 13/23 that sits on the bike now is paired with a 52/42 double chainring and I find that to be overgeared. I'm hoping that the new freewheel will mean I dont have to get a set of 50/39 or 50/34 chainrings.

It's a Shimano 105 rear derailleur......not sure of the actual model number. There appears to be plenty of screw showing out of the B adjuster. I understand that if I screw that further in then
it will move the derailleur down to accommodate the bigger sprockets. I think I will need a new chain as it's still rocking the chain itnhad when I bought the bike and it's seen 2 winters use since then......in other words it's filthy!!

[DaveM]

On the inside surface of the cage on the rear derailleur, there should be a model number stamped. You may be able to look up the compatiblity from that. There are two issues, if it can swing down far enough to clear the 28 tooth and if it has the range to handle going from a 42-14 up to a 52-28. Some short cage road deraileurs can't take that wide a range, but you may be fine. Good luck

[nfmisso]

Just to reinforce one point Dave made:

New Freewheel (or cassette) = New Chain.

[cny-man]

Yes, ABSOLUTELY necessary when the new freewheel has a larger cog!

[Jamin]

I had a look on the rear der this morning. It is a Shimano Rd1055 or 1056. I can't tell as my eyes can't read that small. Had a quick look on velobase and both the Rd1055 and Rd1056 have a max tooth capacity of 28t so it should work but I'm going to go to LBS this afternoon to pick up a new chain.

Gentlemen, thanks you your help and input. Wheels and freewheel should arrive in the next couple of days along with the tires and tubes. Got to wait till next week to receive my long reach calipers