Groupset help please - all these numbers are baffling me!

[raleighnut]

I'm not entirely sure on my current gearing, will have to find out. Short of counting each individual cog, is there a quicker way?



Would that mean 11 at the rear and 3 at the front for 33 total? Not 33 ratios obviously, but 33 different selectable gears?

That would mean using the right hand shifter from one groupset and the left hand shifter from another.
I would expect the 11 speed rear mech to work with a 10 speed shifter and cassette though as it is the amount of cable pulled that affects indexing, never tried this combination though but I have 'mixed and matched' other Shimano components successfully.

 

[Sharky]

It is worth counting all the cogs and understanding where the overlaps are. Say your favourite gear is around 70". With a compact, you can achieve a 69" gear with 50*19 or 34*13. Depending on the cassette, certain cogs may not be included and you may have to use a slightly higher/lower ratio. You could also find that these example options would give a poor chain line.

All good fun - good luck
Keith

 

[Eurostar]

You've got to start by being honest about how fast you like to go at your cruising speed, the kind of climbing you'll do and how much crap you'll carry. Will you use the bike for light touring? Will you go to the Alps or Pyrenees? Do you want to get much fitter and faster than you are? You should aim for a one tooth gap between gears at your cruising speeds. These will be the gears you use most. They need to be near the middle of the block to reduce chain deflection.

Lots of people end up with ratios that are too high, or with a crap spread of ratios which necessitate changing rings at cruising speeds. I found page 30 of this doc v. helpful. You don't need to be considering a Rohloff to be guided by it.http://www.sjscycles.com/thornpdf/ThornLivingWithARohloff.pdf

 

[sabian92]

You've got to start by being honest about how fast you like to go at your cruising speed, the kind of climbing you'll do and how much crap you'll carry. Will you use the bike for light touring? Will you go to the Alps or Pyrenees? Do you want to get much fitter and faster than you are? You should aim for a one tooth gap between gears at your cruising speeds. These will be the gears you use most. They need to be near the middle of the block to reduce chain deflection.

Lots of people end up with ratios that are too high, or with a crap spread of ratios which necessitate changing rings at cruising speeds. I found page 30 of this doc v. helpful. You don't need to be considering a Rohloff to be guided by it.http://www.sjscycles.com/thornpdf/ThornLivingWithARohloff.pdf

At the moment I average 10-12mph on my road bike but the gearing is too high - I don't know what it is, but it's too high.

My main use will be a reasonably flat commute with the odd pleasure ride thrown in as well, with light touring coming in around 12-18 months or so when I've lost some weight and I'm fitter. On my commute there's a sod of a hill right at the start but apart from that it's not too bad. I do live next to the water though (River Mersey) so generally to go anywhere, I have to go up before I go down, which is a pain.

I do indeed want to get a lot fitter and faster but for now a bike I can cruise at 15mph on the flat will be ideal - obviously the more I ride, the fitter I'll get but then equally the more the drivetrain will wear, so I can always change to a different gearing when I replace bits.

I'll give that PDF a read, cheers.

 

[Eurostar]

You also need this: http://sheldonbrown.com/gears/index.html It's rather brilliant. If you know your cruising cadence you can see the ratios for your range of cruising speeds. I can't tell you how much fun I've had planning my transmission with this!

Edit: I think it's a good thing to be fanatical about, because if you get it right nearly all your miles are in the middle of the block and transmission wear is greatly reduced. And it's very satisfying to get everything so efficient.

 

[Eurostar]

That would mean using the right hand shifter from one groupset and the left hand shifter from another.
I would expect the 11 speed rear mech to work with a 10 speed shifter and cassette though as it is the amount of cable pulled that affects indexing, never tried this combination though but I have 'mixed and matched' other Shimano components successfully.

I'm fairly sure the indexing is built into the lever. The cable is irrelevant. If you use a 10 speed indexed lever with an 11 speed mech and 11 speed cassette, you get 10 speeds.

 

[Eurostar]

Would that mean 11 at the rear and 3 at the front for 33 total? Not 33 ratios obviously, but 33 different selectable gears?

Yes, you can select 33 gears but to avoid excessive chain deflection you're advised to select 31 at most, preferably fewer. The Thorn pdf covers this in detail.

 

[Eurostar]

Sabian, Ralighnut mentioned this above, but to expand: some groupsets have a choice of a normal rear mech or a touring one, which is longer and has a greater capacity. If you are buying a groupset in a box it may have the normal mech in it so you'll have to ask about swapping it.

With Shimano stuff if your mech is too short you can nearly always use a touring one from a different group.

 

[raleighnut]

I'm fairly sure the indexing is built into the lever. The cable is irrelevant. If you use a 10 speed indexed lever with an 11 speed mech and 11 speed cassette, you get 10 speeds.

The spacing is different on 11 speed (the sprockets are closer together)

 

[Tojo]

You want the 12-27 cassette an the 50-34 chainset then. Good luck with the purchase

I think if you look a the present 105-5800 they only list three cassette choices 12-25, 11-28 and 11-32 I think from what your wanting you'll be better with 50-34 chainset and the 11-32, you'll have to get the medium cage rear derailleur as the short only covers up to 28t .......

 

[Eurostar]

The spacing is different on 11 speed (the sprockets are closer together)

I didn't say that all 10 speeds would be quiet!

 

[raleighnut]

I didn't say that all 10 speeds would be quiet!

 

[Eurostar]

Actually they would be quiet if, like me, you have 7400 because you can turn the indexing off.

 

[raleighnut]

I can do that on my bike with downtube shifters and also on the one with bar-end shifters.

 

[Tojo]

Evening,

I'm currently in the process of deciding the components for my next bike (A Disc Trucker). I know I want Shimano 105 but there's a few different gearings for both the cassette and the chainset, and it's got me confused.

Do I want 11-25 or 12-27 for lowest gearing on the cassette, and 50-34, 52-36 or 53-39, for the chainset? I want the lowest gearing possible (mainly because I'm a fat sod ) and I can't work out which is the lower one.

I'm going for a triple if that makes any difference.

Ta.

I think if you look a the present 105-5800 they only list three cassette choices 12-25, 11-28 and 11-32 I think from what your wanting you'll be better with 50-34 chainset and the 11-32 cassette, you'll have to get the medium cage rear derailleur as the short only covers up to 28t. also Shimano don't make a triple chainset in 105-5800, sorry.