12 × 25

mark42

Hi all I have an old Allez specialist with carbon forks There's a 12 × 25 8 speed on it . Im I better off putting a 12× 28 8 speed can it be got all I see are 12× 28 10 speed I cycle to blessington and back to tallaght

quozl

Do you struggle with the hills on the route? If not then don't change anything. If you do and you're fairly new to this then don't change anything and give it some time to see if the natural improvements you'll quickly make sort things out. There's nothing really major on that route and if you can get up the embankment (or whatever the slightly steeper one parallel to it is called) then I wouldn't change things.

You can get 11-28 freewheels and cassettes. Ask your LBS. (see here for example http://www.woollyhatshop.com/cassettes/8-speed-mountain-bike-cassettes/cat_386.html)

What do you have at the front? Is it two chain-rings or three? How many teeth on the smaller of the rings? If it's 2 rings then it's probably 39 and another more expensive option would be to change both the cassette at the back and the chain-set at the front to what's known as a compact and has a 34 tooth small ring rather than the 39 on your double. That's a slightly bigger decrease than going from 25 to 28 on the back but less than going from 25 to 30 on the back (which would probably need a new derailleur). it's a lot more expensive though so you'd probably only do it if you needed the big drop in gearing from changing both your chainset and your cassette.

First option though would be to stick it out for a bit if you're new to this. You really will improve rapidly.

NeedMoreGears

http://www.chainreactioncycles.com/ie/en/cassettes?f=4294963630

Several to choose from, if your rear mech can take 'em

mark42

I Don’t sruggle On the blessington run thats only 40k . But I have cycled out to wicklow by stepaside to bray to greystones The hills out that way Killed me I had to stop on the big one coming back into greystone the legs just could not get me up it . There is 39 on the lower front

quozl

Ahh, you'd been pretty specific about cycling Blessignton to Tallaght.

If you're going up Wicklow and want to go further into it then I'd get a compact put on and the biggest rear cassette that your derailleur will take. Hopefully a 28, though some older short derailleurs won't go that large.

It's a job for your local bike shop really and I'd guess you're heading for about 100e all-in?

mirv

Get either one of these in 11-28 or 11-30 for €13; although the gaps between gears are going to be a bit bigger than you're used to with a 12-25. If you have a 2200/2300 or Sora rear derailleur you should be fine up to 30t, although some people have reported being okay up to 32t but it really depends on the design of your derailleur hanger. You'll need to sort yourself out with a chain whip and a cassette tool though, or visit a LBS and get them to sort it for you. It's also a good idea to replace your chain at the same time as a new cassette.

http://www.chainreactioncycles.com/ie/en/shimano-alivio-hg51-8-speed-mtb-cassette/rp-prod67295

http://www.chainreactioncycles.com/ie/en/sram-pg830-8-speed-mtb-cassette/rp-prod6388

mark42

Just trying to get the mileage up a bit. doing cycle against suicide the dublin to Waterford part . The derailleur Is a shimano tiagra cant see it been to hilly I'll probably just up the back cassette

mirv

Change the chain if you get a new cassette, otherwise your old worn chain will skip on the new cassette as well as wearing out the new cassette prematurely. A new 8 speed chain is only about a tenner anyway.

mark42

Well I put 11.28 on the bike cycled tallaght baltinglass and back Not to many hills but still a 100k . Few more practice runs To the cycle against suicide .Thanks for all the feed Back