number of gears

bobjim99

hi folks, bike newbie here.
im buyin a road bike for triathlons , a standard trek , giant or specialised.
so do i need 24 /27 gears or will 16 /18 do?
im fit enough ( running ) and i'm not goin mad for hills unless they are on a race route - which they may well be!
ta for any info.

kenmc

it's not the actual number that matters, rather the range. Most of the time there's an overlap whereby different comination of gears produce the same or almost the same gear ratios.

redmaxi

Whether it's 9 or 10 speed doesn't really matter for now. More important is the chainring choice (at the pedals).
Three choices here: 1) Treble chainring
2) Double chainring
3) Compact chainring
For mostly flat something the standard 53/42 chainring should be fine.

Check out Sheldon Brown

Lumen

Don't get a triple.

Get a standard double (or compact double, if you also want to do lots of hills at easy pace or plan on getting a dedicated tri bike when you get a bit faster).

10 speed is nice, 9 or 8 speed is going to be a bit gappier.

Fit is most important, particularly if you're going to be using aerobars. Don't just buy any old road bike.

blorg

24/27 has three chainrings at the front; 16/18 has two. For racing you generally want two, so 16/18 is better than 24/27.

Most triathlon courses are pretty flat and even if there are hills in a typical short tri bike leg you should be able to manage with a double.

bikenut

Lumen wrote: »

Don't get a triple.

Get a standard double (or compact double, if you also want to do lots of hills at easy pace or plan on getting a dedicated tri bike when you get a bit faster).

10 speed is nice, 9 or 8 speed is going to be a bit gappier.

Fit is most important, particularly if you're going to be using aerobars. Don't just buy any old road bike.

+1 on avoiding a triple unless you're going up very steep hills. In my experience a 3rd chainring on the front causes the chain to rub against the front derailleur unless it's set up absolutely perfect. That slow grinding noise of chain against derailleur has become my sort of calling card.

I'm not sure I've ever really used the inner (smallest) ring on the front. As for buying a triple and changing it afterwards to a double - like buying a Renault and then deciding your going to turn it into a Ford. As usual - try before you buy on 2nd hand bikes in store or friends bikes.

Lumen

bikenut wrote: »

In my experience a 3rd chainring on the front causes the chain to rub against the front derailleur unless it's set up absolutely perfect.

Are you sure you weren't cross-chaining?

Nothing wrong with a triple, I just think it would be an odd choice for triathlon.

blorg

It is a lot easier to adjust a double FD so it won't rub in my experience. The chain angles are less extreme.

poochiem

This might be of interest to OP - and experts please give your comments http://bicycletutor.com/gear-shifting/

Signal_ rabbit

What's wrong with us triples???!!! that's cogist is that!

Conor20

Lumen wrote: »

Nothing wrong with a triple, I just think it would be an odd choice for triathlon.

Can you be more specific? This isn't really intuitive considering the only logical difference in having one less chain ring is a smaller gear range, so there's probably some other factor here than the different maths of the gear ratios for each front/rear combination (between three front chain rings versus two).

Conor.

blorg

Conor20 wrote: »

Can you be more specific? This isn't really intuitive considering the only logical difference in having one less chain ring is a smaller gear range, so there's probably some other factor here than the different maths of the gear ratios for each front/rear combination (between three front chain rings versus two).

Conor.

Front shifting performance particularly under stress is worse and you are more likely to throw a chain (and I did, in my first triathlon, would have been top 5-10 in the bike leg otherwise.) That is really the only disadvantage. There is a weight one too but it is trivial. Generally with racing if you are in any way competitive you will not need the granny ring in any case, and tri courses tend to be relatively flat.

Outside racing triples are often a very good idea as they give you a wider gear range and the shifting issue isn't as critical.

Conor20

blorg wrote: »

Front shifting performance particularly under stress is worse and you are more likely to throw a chain (and I did, in my first triathlon, would have been top 5-10 in the bike leg otherwise.) That is really the only disadvantage. There is a weight one too but it is trivial. Generally with racing if you are in any way competitive you will not need the granny ring in any case, and tri courses tend to be relatively flat.

Outside racing triples are often a very good idea as they give you a wider gear range and the shifting issue isn't as critical.

Thanks! Good use of the phrase "granny ring" also.

bobjim99

thanks all , i realise now my question was whether to go for double or treble chainring. It seems double is what i need.