Gear ratio of less than 1?

[Nigelnaturist]

Wheels are a very common upgrade for Triban 3s, they are likely to be relatively heavy. Any £1500 carbon bike will have better wheels anyway and if you then pop on a good set of tyres (Conti GP4000S for example) climbing will suddenly be easier even if the gearing is slightly higher. That's what I found with my new bike. You might not need that triple.

If possible get some test rides, that will tell you a lot.

The point of a triple is you can have low gearing alongside a close rear ratio cassette, I have a triple 52-40-30 with 28/25/23/21/19/17/15/13, which give me pretty much the same range as compact 12-28, but to get a lower gear on the compact you need to have bigger stepping somewhere i.e. 21-24-28 instead of my 21/23/25/28, plus the drop on the front is quite large, the other thing about a triple is you can use the 30th and say the 21 rear giving the same as a 40x28 but more choice on what to do whilst climbing. It will also go down to 30x15 which would take me to about the same gear as the 52x25 (all but 2"), not something you do often, it is just one click on the shifters front and back however in most gears to be in the right gear when you change the front and not the two or three on a compact.
As most of my riding is on either the 52 or 40 ring basically a full double with close ratios on the rear I consider the 30th front as options to be used as needed, and as my 30x25 is much the same as a 34x28 with only my 30x28 being lower (and this I can change at will by changing the cogs to suite) I dont view the 30th as a granny ring, but as alternative options.

 

[deptfordmarmoset]

"Gears are measured in inches" only in the English-speaking world. Everywhere else they are measured in metres - how far 1 pedal revolution takes you.
The point of using inches or metres is that wheel size is taken into account, which quoting teeth or sprocket ratios doesn't. 1:1 on a Brompton is a much lower gear than 1:1 on a road bike (and is, coincidentally, what the lowest gear on my touring bike is).

Fair point but the question was posed in sprocket sizes for a road bike, which is going to be 700c. And, though the inch is a nice homely measure, I find it harder to think in terms of gear inches - I'd have to go looking them up in tables - and much easier to think in ratios.

 

[youngoldbloke]

When you have an idle moment, work out the gearing in inches for all of the possible combinations of front and rear cogs on your own bike, and it will help you see why one gear is faster or slower, easier or harder, than another.
Top #5 Reply

- or use a gear table .
Shimano now have an 11-32 cassette available with their 11 speed kit. A compact's 34 with a 32 at the back will give you gear of 28", pretty close to the 26" you get from a triples 30 x 30. Of course the triple may have other advantages as outlined above.

 

[midliferider]

Thanks everyone. I value your explanations and opinions.
I have decided that I would like to have the lowest gear ratio as close to 1 as possible. Therefore I would go for a triple in the front (say 50,39,30)and minimum of 10 in the back ( 12-30) to give me required gear ratio.
Thanks for your suggestion of Specialized Roubiax. You can buy 2013 one for £1300.
I will keep looking.
Will keep my B Twin Triban 3 for a rainy day. One can never have too many bikes. I just discovered the way to hang them on the garage wall.

 

[midliferider]

Decathalon has full carbon triple for £1000.
http://www.decathlon.co.uk/btwin-fc-5-white-triple-id_8246256.html

But its rear cassette, though 10 speed is 12-25. But I assume I can upgrade it to 12-30 cassette with this.
http://www.chainreactioncycles.com/shimano-ultegra-6700-10-speed-road-cassette/rp-prod39014

Is that possible?

 

[slowmotion]

If you want a smaller chain ring instead of the 30 tooth one, you can buy one from Spa Cycles. I put on a 28 tooth one and use it with an 11-28 cassette. I don't use the lowest gear very often but it's really handy when you start running out of gears on a steep hill. It's good for morale too.

 

[midliferider]

Slowmotion, perhaps I should try that with my B Twin Triban 3. Find a 8 speed one with 28 tooth and see.

 

[400bhp]

carbon bike + gear ratio < 1.

Hmmmmmmmmmmmmmmm

Point?

 

[slowmotion]

Slowmotion, perhaps I should try that with my B Twin Triban 3. Find a 8 speed one with 28 tooth and see.

Thrash around on the Spa website or give them a ring and tell them what groupset you have. I think my ten speed ring cost about £12.

 

[byegad]

My lowest gear ratio is 22 front to 34 rear. On a recumbent trike with a 20" rear wheel this gives me 12.6" after allowing for a skinny tyre actually measuring 19" in diameter fitted. The only issue with any frame is the amount of torque you are asking the frame to handle. Assuming you are not a potential Grand Tour winner you should be OK with a normal kind of effort and a carbon frame.

 

[swansonj]

My lowest gear ratio is 22 front to 34 rear. On a recumbent trike with a 20" rear wheel this gives me 12.6" after allowing for a skinny tyre actually measuring 19" in diameter fitted. The only issue with any frame is the amount of torque you are asking the frame to handle. Assuming you are not a potential Grand Tour winner you should be OK with a normal kind of effort and a carbon frame.

Surely, for a given gradient, lower gears equals lower torque at the BB? If you're worried about frame strength, wouldn't you want to fit even lower gears?

 

[MikeW-71]

Decathalon has full carbon triple for £1000.
http://www.decathlon.co.uk/btwin-fc-5-white-triple-id_8246256.html

But its rear cassette, though 10 speed is 12-25. But I assume I can upgrade it to 12-30 cassette with this.
http://www.chainreactioncycles.com/shimano-ultegra-6700-10-speed-road-cassette/rp-prod39014

Is that possible?

Perfectly possible. You could also use a Tiagra 12-30 cassette, which is about £25. You would need to lengthen the chain a bit too I believe.

 

[TheDoctor]

Completely possible.
I had a 48/38/24 chainset, with a 13-26 cassette on my carbon uberbike in the dim and distant.
I've now got a 50/34 compact with an 11-32 cassette, which is obviously far more sensible...

 

[midliferider]

That brings us to the next question,
Is Decathalon B Twin is as good as or better than Scott or Specialized?

 

[deptfordmarmoset]

carbon bike + gear ratio < 1.

Hmmmmmmmmmmmmmmm

Point?

Slightly over 1 here but I'm a slow rider and even slower on hills - 34/32. When I'm riding with others I don't want to hold them up. Lightness and a wide gear range make sense to me.