Chainsets and gearing

[Hutch118]

Hi folks, I'm looking for advice on gearing and chainsets for my bike. When I bought it (an Orbea Avant road bike) it came with the factory fitted chainsets and gears. They are Shimano Sora 3550 34/50 chain rings and 12-27, 9 speed rear cartridge

When I'm out on the bike, everything's ok I get on fine but the problem is this, I'm not fit enough at the moment to climb reasonably decent hills, my legs absolutely ache and I inevitably have to stop. Now I know I have to improve my level of fitness, that's obvious, plus I need to improve on the distance and time I'm on the bike. I can do all that.

My query is, can I change the rear gearing sprockets to make climbing a wee bit easier till I improve and what would be the best combination to go for.
The bike came with the Shimano Sora/Claris set up but I really don't know what to go for or what I actually need. I take it the cartridges can be changed. What would suit me better as I don't understand the gearing correctly. Is there a thread I can read so I can understand it better?

Any advice and help ppreciated, thanks. Hutch.

 

[Nibor]

The simple answer is yes I managed to fit an 11-34 10 speed cassette to my set up relatively easily bt adjusting the B-screw. There are 11-34 9 speed cassettes available http://www.chainreactioncycles.com/sram-pg980-9-speed-mtb-cassette/rp-prod8332 however you would need to check if your rear derailleur is at least a medium cage. Without knowing what model your Orbea Avant is I can't check for you.
If you are at all unsure I would recommend you contact your LBS for advice buyt I suspect you should at least be able to get a 32 sprocket on the back of your bike.

 

[Hutch118]

Thanks for the reply Nibor, that's just the sort of thing I was looking for.

I take it the higher number of teeth just makes it that wee bit easier on the pedals ?

Oh yeah and the bike is an Avant H50 model.

 

[Nibor]

Looking a bit closer you should easily if this is the model of your bike the derailleur looks plenty long enough

 

[Hutch118]

That's the bike.

 

[Nibor]

Thanks for the reply Nibor, that's just the sort of thing I was looking for.

I take it the higher number of teeth just makes it that wee bit easier on the pedals ?

Yes more teeth on the back the easier the gear
Front Rear Gear
34 27 1.259
34 32 1.063
34 34 1

The gear is the number of times the back wheel turns for each complete turn of the pedals

 

[Nibor]

hasn't formatted very well

 

[byegad]

Yes you can and if it's spoiling your ride do it sooner rather than later. Your troubles start as soon as you change the rear cassette. 12-27 is already pretty wide for a road bike and you need to check if an 11-32 or 11-34 can be accommodated by your rear derailleur. The easiest way is to take it the LBS and ask, but if you do that you should let them change it for you. Their time and expertise are money. You may need a new derailleur in which case the costs go up. the changers at the handlebars should deal with any 9 speed cassette so look at £30-50 for a Tiagra cassette, fitted and about the same again if you need a new derailleur. From Wiggle you get them both for £50 and fit them yourself. I started with a basic tool set and now do everything short of wheel-building myself. As the cheap tools wore out I bought better replacements and over the last 17 years have saved a lot of money.

 

[Hutch118]

Understand it now, thanks you've been very helpful. The actual 9 speed cassette, does it have to be a Shimano Sora to match the components that are already fitted or can I fit something else, I'll just keep it as a 9 speed as well.

 

[Dogtrousers]

As above. I refitted an 11-32 cassette replacing the ... erm ... something else on a friend's bike just recently. It had standard Claris (I think) medium cage mech and all that was needed was a new cassette and chain. She was very happy with the result

Technically what you need to know is two things.

What is the maximum sprocket size your rear mech can cope with? (number of teeth) That's fairly self explanatory and as people have said above you can often push it a bit and use a slightly bigger one.

What is the capacity of your rear mech? (number of teeth) This is the mech's ability to take up slack in the chain. If you have a greater difference between the big and small sprockets then it needs to cope with a wider range of differences. This is given by (Big chainwheel teeth + biggest sprocket teeth) - (Small chainwheel teeth + smallest sprocket teeth). If you wanted to fit an 11-32 you would need (50 + 32) - (34 + 11) ie a capacity of 37 teeth.

You can find these two things by searching on the web.

The medium cage Claris on my friend's bike was fine.

You may want to consider, instead of say 11-32 getting something with a bigger smallest sprocket (ie not 11) which will give you smaller gaps between the gears. Something that was discussed recently in this thread: https://www.cyclechat.net/threads/1...e-what-noticeable-difference-is-there.204707/


Do it! Low gears rock!

 

[Hutch118]

Thanks for that link, it was also what I was looking for and exactly the answer. I'll look into it a bit more.

Cheers for the advice folks, very helpful as always.

 

[Nibor]

Understand it now, thanks you've been very helpful. The actual 9 speed cassette, does it have to be a Shimano Sora to match the components that are already fitted or can I fit something else, I'll just keep it as a 9 speed as well.

any shimano or Sram 9 speed cassette should be fine

 

[Garry A]

This is what I have on my Sora setup in 11-30 range.

you may or may not need a longer chain also.

 

[Hutch118]

Cheers Garry

 

[TheDoctor]

I think the widest ratio 9 speed is a 12-36, which should get you up practically anything. You will need an MTB rear mech, and a longer chain, but it will be geared as wide as possible.