Cassette confusion (?)

neil_uk

I recently bought a second hand Giant road bike. It has a twin ring chain set, and the largest ring on the rear cassette is only 23 teeth. Coming from a mountain biking background - I'm finding this very high geared! I don't want to mess about changing the chainset as it's a shimano 105 that has seen very little use.

I'm wondering - can I replace the cassette with something bigger e.g. a 28toothed sora, or will that mean i also have to replace my rear mech which is also a 105 (with what looks like a very short cage), with a longer caged mech?

Any help would be really appreciated as roadie gearing is completely new to me!

Cheers guys!

Neil

springtide9

I assume you have a 'Compact' chainset (50/34 teeth)?

You can fit cassettes from with Shimano or SRAM.
http://www.sram.com/sram/road/products/ ... erm-id/148
http://www.shimano.com/publish/content/ ... _road.html

SRAM generally have a larger range of 'cogs'. A personal preference is to go for an 12-26 (or 28) rather than starting at "11" - as you get tighter ratio's in the middle of the sprocket.

Looking at Shimano's webpage, it looks like you can run upto a 28T on the rear:

http://www.shimano.com/publish/content/ ... _road.html
http://www.shimano.com/publish/content/ ... _road.html

Hope that helps.

neil_uk

Brilliant, thanks for that! The other problem is - it's only seven speed - and that limits my choices quite a bit, and I don't want to go to great expense of replacing everything.

I'll have a hunt around online and see if i can find something like a 12-26!

Cheers mate
Neil

springtide9

Shimano Tiagra Cassette 7 Speed HG50 12-28
http://www.chainreactioncycles.com/Mode ... elID=38302

racingcondor

You're likely to be fine moving to the 12-28 above but you'll probably find that your chain is too short if you do (it's having to reach around a much larger circle on the granny gear).

I'd install the cassette and then take a look at a couple of YouTube vids (or the vids on the Park Tools website) on installing a new chain just to check if your rear derailleur is being stretched too far.

pdw

The link to the rear derailleur above is for a 10 speed. I think the older 7 speed may have a lower maximum sprocket size, but I'd be inclined to just try it before shelling out for a new rear mech.

As others have said make sure to check the chain length - it's quite likely to be too short, and that can cause damage if you ever select big-big.

neil_uk

Brilliant - thanks for that Simon. I've ordered the cassette this morning.

Yeah, if I have to change the mech - so be it. I should be able to pick up something like a tiagra fairly cheap.

Thanks for all the help and advice guys - I'll let you know how it works!

Cheers
Neil

Pickled Pig

@springtide9
Thanks for the informative post - I have an ultegra 11-28 cassette and would find the 16 on the SRAM 12-28 cassette very useful. Is there any drop in shifting performance if I move to a SRAM cassette? I've always assumed that Shimano and SRAM used different chain architecture so that, even if they work together after a fashion, there is a drop in performance due to different ramps and tooth size on the cogs.
Andy

neil_uk

Good news! (sort of lol).

Fited the new cassette today.... the derailleur has no problem with clearance, and the extra few teeth have made a huge difference to the low gear! Very happy!

Next problem!
As It's a new cassette - I fitted a new Connex chain (I always change chains when i fit a new cassette for obvious reasons). Now the problem is that the new chain links wont 'drop' into the new teeth... it's as though the chain links are too short and the new chain needs to stretch itself.

What it isn't is...... not a bent deraileur, or gear cable tension issue, as the deraileur is lining up perfectly. It's not the limit screws either, as again, everything is lined up bang on. The problem is worse on the smallest sprocket where the chain links seems too short to drop into the teeth cutouts - if that makes sense? It's as if the links need to be a couple of hundreths of a mm longer.

Any idea what can cause this?? or does the new chain just need to bed in? did I buy the wrong chain?

This one has me totally baffled!

Thanks again,
Neil

t4tomo

Is it definately a 7/8 speed chain you've put on? A 9 or 10 speed chain is slightly narrower guage which might cause your issue?

neil_uk

Ermmmm.... I hope so lol! am i right in thinking 7 and 8 speed chains are the same??

http://www.wiggle.co.uk/wippermann-conn ... eed-chain/ that's the one i bought.

Cheers
Neil

t4tomo

yes 7 & 8 same size so that should fit your cassette. Seems odd that it doesn't.

Does chain look different to the old chain? or does cassette look different to old cassette.

Also does it fit on the chain rings fine - if so maybe the cassette is the issue and not the chain.

neil_uk

Yeah, the chain fits on the chain rings ok, but that could be due to the fact that the rings have a bigger arc, like the larger sprockets... And, yes - everything looks the same.

I tried putting my old 9 speed chain on from my mountain bike, and that seems to sit in the teeth no problem ?!?!?!?!

hmmmm!

keef66

you sure it's a 7 speed cassette?

neil_uk

LOL - yeah - that crossed my mind as well for a moment... But, yes, it's definitely a 7 speed tiagra HG50 cassette.