> Hello, Will a Deore 9spd 11-32 or even 11-34 cassette work on my road
> bike with a tiagra short cage rear mech & 52/42 double chainset? If
> not will it work with a deore rear mech?
There are reasons why long-cage rear derailleurs exist, and trying to use a
cassette with a very large cog is one. You can fake it a bit by tightening
the "B" tension screw, which moves the derailleur away from the cogs, but
doing so adversely affects shifting in the smaller cogs, because it reduces
chain wrap. It can also make skipping more likely as well.
Whether even that might work depends upon the length of the derailleur
hanger. If you have one that's longer than most, it's more likely the
derailleur will clear the larger cogs when shifting up into them. Otherwise,
it might instead just push up against the next-larger cog, instead of moving
the chain further up.
And finally, without the ability to hold enough chain, you might have
problems getting the bike to shift into all possible gears without damaging
the derailleur and possibly the frame. Even though you might think you'll
never shift into the large/large combo, it happens anyway. And here's how-
you're heading up a hill, you're tired, it's hot, and you're not exactly at
your best. All you know is that you need a lower gear, so you reach for that
rear shift lever and click it one step lower and BLAMMO, you didn't realize
you were still in the large front chainring and you've now ripped your rear
derailleur out of the hanger, and possibly damaged the frame as well.
> I usually have a 12-27 cassette, but want to have some of that extra
> range for steep climbs without having to move to a triple chainset if
> that is possible..
Reasonable from a standpoint of saving the expense, but otherwise, modern
triples work extremely well, and allow for much smaller spacing between
gears. You're not as likely to wish you had something just a bit smaller or
larger.
> Thanks, Alan
--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com