More gearing questions

by Harryb2996   April 13, 2014  

I have a new(ish) bike and on my old one i ran a compact on the front and a 12-28 on the back. the new one however is not a compact and has an 11-25 back. The rides are killing me at the moment and i have considered swapping out and fitting a compact to make it easier.
Do you recon it's worth leaving it and ruffing it for a few more months till i build myself in to it or switching to a compact now?

10 user comments

Oldest firstNewest firstBest rated

You don't say what your setup is, but I think any Shimano 105 rear derailleurs (for example) from the last few years can officially take up to a 28t, but depending on the frame you may get away with a 30t (and perhaps a 32t). If you can fit a 30t, that will take you pretty close (within about 10cm per rotation) of what you used to have.

You can probably pick up a new cassette for less than £20, which has to be worth it if it makes you more comfortable.

posted by FMOAB [238 posts]
13th April 2014 - 22:03

1 Like

What type of rides are you doing and what aspects of the ride are you having probs with?

I'm switching out my 11-25 cassette to an 11-32 because I've been doing a lot of hill training (short steep grades ~20% and long sustained climbs ~2-4 mile) to train for a sportive this summer which is 106 miles with 7000 ft elevation gain which, since my last name isn't Froome, has been a rather painful slog with the 11-25 and August seems to be looming over me.

Melancholy is incompatible with bicycling. ~James E. Starrs

movingtarget's picture

posted by movingtarget [136 posts]
13th April 2014 - 22:49

2 Likes

Yes, before bothering with the chainrings, try out a 27t or 28t on the back. That's around 8-12% difference in gearing. Going from a compact to "normal" is something like 6% (big) or 15% (small). So, you're not far off achieving the same change in gearing just by swapping up to a 28t. If you can fit a 32t, you'll get a whopping 28% difference in gearing.

You pays your money and takes your choice. But, given relative cost and difficulty, I'd go for a different cassette. You can easily swap around for different profile routes.

Enjoy tinkering....

posted by Jimbonic [111 posts]
14th April 2014 - 6:35

1 Like

You'll probably need a new chain too, if you go with a massive block on the back.

posted by bashthebox [647 posts]
14th April 2014 - 8:36

1 Like

With a 53/39 (diff of 14) and 11/28 (diff of 17) - (Ultegra 6700 - SS) and still using a short cage derailleur (SS can take up to 33 tooth difference) so theoretically can stick on a 30 tooth rear without having to move up to a GS - mid range rear cage....and prices for Ultegra getting reasonable...means you don't necessarily need to go compact up front...just change to an 11-30 cassette (105/Ultegra)...and power up those climbs...

The_Kaner
FREEEEEEEEDOM!

The _Kaner's picture

posted by The _Kaner [488 posts]
14th April 2014 - 13:36

1 Like

" I have a new(ish) bike and on my old one i ran a compact on the front and a 12-28 on the back. "

It seems like nobody actually read ur initial post above.
I was in the same position as you when I bought my first road bike ,53/39 front 11/25 rear , after coming from an mtb to full race rings and living in S.Wales climbing comfortably is important , I tried the 12/28 rear block on the std front and it isn't massively different , as such I spent 30 quid on a set of compact front rings (105 should have the same bcd whether compact or race and I've never looked back.

All in you should be able to do rings / chain / rear block(tiagra) for under 100 quid and it will be money well spent

posted by chiv30 [879 posts]
14th April 2014 - 16:07

0 Likes

bashthebox wrote:
You'll probably need a new chain too...

Oh yeah, forgot about that.

posted by FMOAB [238 posts]
14th April 2014 - 19:36

2 Likes

Yup, I didn't read it properly. Despite that, a 34 chainring with a 28 cog on the back gives about 2.6 meters of development (on a 23mm tyre). A 39 tooth chainring with a 32t cog gives 2.6 meters of development. You pays your money, you takes your choice.

posted by FMOAB [238 posts]
14th April 2014 - 19:55

1 Like

FMOAB wrote:
Yup, I didn't read it properly. Despite that, a 34 chainring with a 28 cog on the back gives about 2.6 meters of development (on a 23mm tyre). A 39 tooth chainring with a 32t cog gives 2.6 meters of development. You pays your money, you takes your choice.

Short cage rear mech won't handle a 32 tooth cog on the 53 ring it will pull the top jockey wheel into the 32t cog ending in possible spoke mashing at best and it will only take one mistaken gear change for that to happen .

The other alternative is a Shimano deore rear mech and 12-32 which will enable the required combination without the danger when on the 53

posted by chiv30 [879 posts]
14th April 2014 - 20:47

1 Like

I have a felt f95 that came with sora groupset. 50 - 34 on the front and 11 - 25 cassette. I managed ok but after failing to finish a sportive in bad weather and with a cold I looked into changing the cassette. I managed to fit an 11 - 32 using the medium sora derailleur despite being told it wouldn't work. Also fitted a new kmc chain. Removed one link and it works a treat. Makes it a lot more practical on hills and also means you can stay in the 50 for longer on the flatter bits. The cassette is a shimano one that cost around £12 from wiggle. I got it for the ratios. Not the lightest but works for me.

posted by Hensteeth [53 posts]
14th April 2014 - 21:06

1 Like