Cassette – teeth

miller82

Alright folks…. Question…. Buying a new cassette (105) …. Never had the option before to pick teeth range. Its for the training/road/commute bike. Suggestions ???
Options :

11-28t
12-25t
12-27t
11-25t

07Lapierre

Do you really need an 11 tooth sprocket? Be honest now!

miller82

07Lapierre wrote: »

Do you really need an 11 tooth sprocket? Be honest now!

honestly..... i havent a notion mate this is totally over my head

Alek

I'm happy with 12-27. Very rarely use 12... No use for 11t unless you're road racing and good at it, imho.

miller82

okay so, should possibly go 12.... and 25 or 27 or 28 ??

Alek

If you have double in the front I'd go 12-27, if triple - 12-25.

jimm

Ignore the lower no's. ie. 11t & 12t

If the terrain on your spins is hilly, go for a higher toothed sprocket as it will be your "easiest" gear ie. 27t or 28t

07Lapierre

miller82 wrote: »

okay so, should possibly go 12.... and 25 or 27 or 28 ??

If you intend cycling in hills/mountains, then get the 27 (Hills) or 28 (mountains e.g. Alps) otherwise, stick with the 12-25.

What cassette is on your bike at the moment?

maesrichard1

First question is, what size chainrings have you up front? Ive a 53 x 39 and i ride a 25-11.

The closer the highest and lowest number of teeth is, the smaller the jump between gears, allowing for a smoother gear change. However, having closer geared sprockets will normally decrease the size of the largest sprocket on the cassette, leaving you with a gear ratio that may be less suited to climbing and tough terrain.

If you ride lots of hills, or you struggle with hill climbing, a cassette with a low sprocket of 27+ teeth may be beneficial, allowing you to keep spinning for longer, rather than grinding. Ensure that your derailleur is compatible with the largest sprocket on the cassette if you so choose to change, as you may require a longer cage rear derailleur to accommodate it.

Simples

miller82

Thanks

lennymc

do you race?

hf4z6sqo7vjngi

12-25, very few hills in Ireland would need any more than a 39 and 25 on the back.

jimm

Franklin Bewildered Sunglasses wrote: »

12-25, very few hills in Ireland would need any more than a 39 and 25 on the back.

Are you joking? :eek:

Seweryn

Franklin Bewildered Sunglasses wrote: »

12-25, very few hills in Ireland would need any more than a 39 and 25 on the back.

You can never have enough (low) gears.

maesrichard1

Franklin Bewildered Sunglasses wrote: »

12-25, very few hills in Ireland would need any more than a 39 and 25 on the back.

Anything over 10% might demand higher than a 25 for some people. mhave to keep in mind than everybody is not at the same level.

NeedMoreGears

I've a 11-28 105 cassette paired up with 50/34 at the front. I'd rarely use the 11 but the 28 is called into service on things like Windgate in Howth. It's also very handy when I get knackered going up Sally Gap from Enniskerry. I don't race but do a few sportifs each year.

G1032

I've a 12/30 with a 52/39

IIRC a 34/28 will give you 4% or so lower gearing than a 39/30

Edit - Seems closer to 7.5% lower ( I think my calculations are correct?).......

39/30 - 34.2
34/28 - 31.8

((34.2-31.8)/31.8)*100 = 7.5

Somebody can correct me if that is wrong

nilhg

I was in Spain on holidays recently and hired a bike, didn't realise that it had a 11-25 cassette instead of the 12-28 that was advertised until I hit the first big 12% ramp, a bit of a shock to the system but no real choice but to grind it out. I did think of asking for a change but stayed as is and cycled away, didn't let it put me off doing anything I wanted to do, but the steep stuff (and there was some really steep stuff) was just a hard hard grind, cadence must have been down to 30 at times, you wouldn't want to be doing that too often or with any much amount of KMs in your legs.

At home most of the time I use a 12-28, with a 11-25 for club league races and the faster sportives, I had a 12-30 for the Wicklow 200, hills look a lot bigger after 150kms.

smacl

Seweryn wrote: »

You can never have enough (low) gears.

+1, better to be looking at them than looking for them, particularly if you start hitting hills towards the end of a long day on the bike. For me, it's never the first hill of the day that's the problem, it's the last one.

ford2600

Franklin Bewildered Sunglasses wrote: »

12-25, very few hills in Ireland would need any more than a 39 and 25 on the back.

Priests leap, Mamore, Mount Leinster etc etc

crosstownk

ford2600 wrote: »

Priests leap,

I struggled up Priest's Leap earlier this year in a 34x32.

That said, I hope to get rid of the 32 as I think the security it gives me is hindering progress because I have a bad habit of shifting to the next lowest gear rather than grinding out so I need to remove the temptation.

hf4z6sqo7vjngi

ford2600 wrote: »

Priests leap, Mamore, Mount Leinster etc etc

I did say very few:)

hf4z6sqo7vjngi

maesrichard1 wrote: »

Anything over 10% might demand higher than a 25 for some people. mhave to keep in mind than everybody is not at the same level.

I was answering specifically to the OPs post given his background.

NeedMoreGears

Just wondering what the advantage of a less gappy cassette is.

A ten speed 11-30 probably only has 8 gears to cover the 11-25 range whereas a "proper" 11-25 has 10. What do the extra two gears provide? Better control over cadence? Better shifting? Weight?

maesrichard1

more gears allows for a smaller jump between cadence with each gear change.

smacl

maesrichard1 wrote: »

more gears allows for a smaller jump between cadence with each gear change.

True, but for a given cadence on a fixed gradient, the extra speed gained / effort required at big end of the cassette per extra tooth is much smaller, and the gaps are often hidden in the middle of the cassette, for example on a typical 11/25 you get the

Cog Teeth Diff %Diff
1 11
2 12 1 8.3%
3 14 2 14.3%
4 15 1 6.7%
5 16 1 6.3%
6 17 1 5.9%
7 19 2 10.5%
8 21 2 9.5%
9 23 2 8.7%
10 25 2 8.0%


I'm currently running 13/28 and get the following, which is less gappy (and easier for a crap climber such as myself);

Cog Teeth Diff %Diff
1 13
2 14 1 7.1%
3 15 1 6.7%
4 16 1 6.3%
5 17 1 5.9%
6 19 2 10.5%
7 21 2 9.5%
8 23 2 8.7%
9 25 2 8.0%
10 28 3 10.7%

Alek

13/28

Is it shimano compatible? Where to get one?

smacl

Alek wrote: »

Is it shimano compatible? Where to get one?

Cheapo BBB campag cassette for piecemeal veloce upgrade; http://bbbcycling.com/bike-parts/cassettes/BCS-10C.

Alek

Cheers, they seem to come in 13-30 for Shimano. Need to think now

Tigerandahalf

I have a compact 50 34 with a 14 28 cassette on the back. I find the lowest 34 28 gear sometimes isn't enough especially when your legs are tiring and you just want to spin up a hill no matter how slow you are going. I have a 7 speed cassette. I am not sure if I could change to a lower gear cassette. Do the number of teeth on the sprocket indicate the diameter of it, e.g. a 14 tooth sprocket will always have a smaller diameter than a 16 tooth sprocket?

Brian?

07Lapierre wrote: »

Do you really need an 11 tooth sprocket? Be honest now!

An 11 comes in handy when descending. I can't really see any benefit in not having an 11, doesn't really make the cassette and gappier for shifting.

I have 3 cassettes on 3 wheelsets; 11-25 for flat spins, 11-28 for hilly spins and 11-27 I don't know why I own.

Edit: I have a compact on one bike, 50x34, this is the climbing bike and a standard, 53x39, on the other.

crosstownk

Tigerandahalf wrote: »

Do the number of teeth on the sprocket indicate the diameter of it, e.g. a 14 tooth sprocket will always have a smaller diameter than a 16 tooth sprocket?

Yes. The 'valleys' between the teeth have to accommodate the chain so less teeth = smaller diameter.