7 speed cassette for old road bike

briN_s

My gf after being given an old road bike, but is struggling with it on any hills, as it seems to be geared quite highly. The front cogs are 52 and 42T and the rear cassette is a 7 speed 13-21T. I was going to order a new cassette but I am not sure if there is a particular type to match the freewheel/wheel, or are they pretty much universal? I can read the following from the current cassette: Hyperglide GH KM 13T3 LH Shimano.

Would any of the following work with it? And also what ratio would you recommend for average cycling (no crazy steep routes)?

Shimano-cs-hg50-7-speed-cassette 12-28T
bbb-bcs-07s-7-speed-cassette 12-32T
shimano-mf-tz21-7-speed-freewheel 14-28T
sram-pg730-7-speed-cassette 12-32T

Thanks
Brian

quozl

That is one seriously nasty gearing setup!

Even a 42 front and a 28 back is still pretty harsh. It'd fall between a 34/23 and a 34/22 if you had a typical 34 tooth compact front ring.

I know you said no crazy steep routes but even any moderate hill would be tough on that if you're not strong.

I think I'd get the 12-32T SRAM or BBB cassettes for that reason.

SRAM 7 speed are compatible with Shimano 7 speed - http://sheldonbrown.com/k7-7.shtml . The BBB also says its shimano compatible. I don't know that brand, check the reviews. SRAM are good but the other is probably fine too.

If you're getting a nice new cassette you might want to get a new chain too - if the chain is worn then it'll kill your new cassette quick smart. You can test by measuring 12 links (1 foot) of chain and making sure that it's pretty accurately 1 foot. 1/16" over 1 foot means it's a pretty bad IIRC. Or just get a new chain if in doubt - they're cheap - and save yourself the hassle.

briN_s

Great, thanks for the info, will take a look at that site. Was thinking I will prob have to change chain anyway as it will need to be that bit longer to go around the extra teeth on new cassette. I'm not sure the derailleur will stretch far enough with the existing chain

quozl

****e, that's a thought. The derailleur you have probably won't be able to handle the extra chain length.

You're adding 11 teeth, which is 5.5" if you're going from a 21 to a 32.

Best post up the details of your derailleur and hopefully someone can tell you. You might need to get a 7 speed MTB derailleur to handle that. Something like http://www.chainreactioncycles.com/ie/en/shimano-acera-m360-7-8-speed-rear-mech/rp-prod38673 . Adding extra expense though.

briN_s

All I can see on the derailleur is Shimano RSX, can take some measurements from it if necessary? I have attached a photo, hopefully thats of some use?

happytramp

Your derailleur will be fine with a 28t rear cog. It'll also make a HUGE!! difference to your ability to go up hills.

briN_s

Is the 28T the biggest you think will work with the setup on the bike?

Paul Kiernan

Check out WoollyHatShop, it's a lot cheaper than Wiggle for that type of stuff.

I presume it has down tube shifters? Square taper cranks? You could possibly change to a cheap triple as well getting the front down to 28 or 30. Again WHS has cheap crank setups.

Is the current rear a freewheel or freehub? Just make sure you order the correct replacement!

happytramp

briN_s wrote: »

Is the 28T the biggest you think will work with the setup on the bike?

I'm assuming it's an old steel framed racer with downtube shifters etc based on the gear ratio you've mentioned . If this is the case and the wheels are original (as in 70's/80's) you'll need a Freewheel not a cassette.

http://sheldonbrown.com/free-k7.html

It's also likely that with your current set up that at 28t cog is the largest that your derailleur will be able to handle. That said a 42x28t gear ratio will get you up most hills once you get used to it. I had no problems with the same set up cycling around the dublin and wicklow mountains when I was starting out (once I got relatively fit and rode around Howth hill a lot first though)

briN_s

Thanks everyone for the replies. The bike had the downtube shifters but were converted to the handlebar type, similar to the sora type. So would prob need new shifter if switching to a triple. Cost will rule that out for now.

I am presuming they are the original wheels on the bike, or reasonably old ones. So maybe the freewheel is what I need. That sheldonbrown website seems to have some good info so will look at the bike a bit closer over the weekend and figure out exactly what I need.

clog

From the info given you have a 7 speed freehub (you can see the removal splines, freewheels are different). That rear mech has a limit of 28 teeth.

briN_s

Is this (Shimano-HG20-7-Speed-Cassette-Sprocket-12-28T), likely to work with the bike? It is classed as MTB cassette on the website. But I assume that is more to do with the ratios?

I will order a chain with it as well. Is a quick link the best way to join the chain afterwards?

studiorat

That HG 20 cassette is a cheap and nasty bit of tat. If the bike is half decent you should look at HG 50 cassettes or ones made by Sram or even IRD. Or you could search ebay for a nos durace or something.

Having done it myself I think putting a large cassette on the back ruins the look of a bike. Have you tried to get a 39 tooth inner ring on the bike? You should be able to fit one right on there with very little hassle.

Like others have mentioned make sure its a cassette you need and not a freewheel. For modern freewheels I guess IRD are the best.

[URL="http://http://www.chainreactioncycles.com/shimano-acera-hg50-7-speed-mtb-
cassette/rp-prod38302"]
[/URL] http://http://www.chainreactioncycles.com/cassettes?f=4294963616

http://http://www.sjscycles.co.uk/ird-comp-7-speed-cassette-shimano-compatible-prod22885/



I find SJScycles really useful for older and odd fitting components. And KMC chains a bit easier to put together and take apart.