gearing for TT's

addicted to Langbar

Dear all,

Just after a bit of advice about the effect of gearing before investing in a new bike. Would having a 52/39 chainset make much difference in a time trial compared to a compact (50/34) or a triple? I live near lots of nice hills so don't want to sacrifice losing lower gears for no real benefit at the top end.

Thanks.

Bronzie

Only if you can spin out your 50x12 during a TT (unlikely)

Being more serious, it may well be beneficial to have closer gearing on the front - a 36T inner ring is next to useless in anything but a very very hilly TT. A 50/42 or even 50/44 would give you a much better range of useable gears, but of course the downside is having to change chainrings before and after each race (depending on what other terrain you cover when not racing).

Mad One

Are you talking about a bike specifically for TT's, or are you gonna use it for regular riding too?

wjws

5034 will be fine - an 11 tooth cassette will make more difference than going to a 52t chainring.

Dess1e

Mad One wrote:

Are you talking about a bike specifically for TT's, or are you gonna use it for regular riding too?

The only pertinent reply so far.

kilo

addicted to Langbar wrote:

Would having a 52/39 chainset make much difference in a time trial compared to a compact (50/34) or a triple? I live near lots of nice hills so don't want to sacrifice losing lower gears for no real benefit at the top end.

Thanks.

Hi

Last year I time trialed on my road bike which had a 50/34 on it, this year I'm using a tt bike with a 52/39 on it - last year when racing I didn't use the 34 and this year i haven't used the 39! Admittedly I haven't been racing on any particuarly hilly courses but as others have stated even with a 50 on the front you will be able to get a sufficiently big gear to stop you spinning out. The biggest difference I have noticed between the two set ups is the fact that the cassette on my tt bike does not have any big jumps between cogs so I don't go from spinning to pushing and vice versa but keep a reasonably consistent cadence. The most important factor in choosing the chainset is what you are going to be using the bike for. If it is a dedicated tt bike and your strong then a 52/39 should cut down on big jumps between the ratios if you ride sporting courses and use the inner ring. If you are going to do lots of other riding and tt'ing is not such an important part a comapct should be fine.
More important for time trialing will be your position, training and wheels rather than the chainset ratios, as empahsised in the write up in Cycling Weekly for the Anfield 100, which was won on a converted hybrid. A final point is that if you use Shimano hollowtech chainsets you could get both and probably swap between a compact and a 52/39 in about 10 minutes.

good luck

sub55

kilo wrote:

addicted to Langbar wrote:

Would having a 52/39 chainset make much difference in a time trial compared to a compact (50/34) or a triple? I live near lots of nice hills so don't want to sacrifice losing lower gears for no real benefit at the top end.

Thanks.

Hi

Last year I time trialed on my road bike which had a 50/34 on it, this year I'm using a tt bike with a 52/39 on it - last year when racing I didn't use the 34 and this year i haven't used the 39! Admittedly I haven't been racing on any particuarly hilly courses but as others have stated even with a 50 on the front you will be able to get a sufficiently big gear to stop you spinning out. The biggest difference I have noticed between the two set ups is the fact that the cassette on my tt bike does not have any big jumps between cogs so I don't go from spinning to pushing and vice versa but keep a reasonably consistent cadence. The most important factor in choosing the chainset is what you are going to be using the bike for. If it is a dedicated tt bike and your strong then a 52/39 should cut down on big jumps between the ratios if you ride sporting courses and use the inner ring. If you are going to do lots of other riding and tt'ing is not such an important part a comapct should be fine.
More important for time trialing will be your position, training and wheels rather than the chainset ratios, as empahsised in the write up in Cycling Weekly for the Anfield 100, which was won on a converted hybrid. A final point is that if you use Shimano hollowtech chainsets you could get both and probably swap between a compact and a 52/39 in about 10 minutes.

good luck


yeah, but the anfield 100 was won by one of the best distance racing cyclist this country has ever produced.
you are all wrong anyway, the optimium chain ring size is a 56 and i`ll tell you all why later, cos i got to go out now.

kilo

yeah, but the anfield 100 was won by one of the best distance racing cyclist this country has ever produced.



I know, the point I was tryimg to make is it's not worth getting overly hung up on your kit spec if your position and training is all wrong.

I'm dead curious about the 56 ring - I need all the help I can get!

nmcgann

Depends if you can keep the power on at high revs when you are tired. I can't, so I run 53x11on my TT bike.

I recently changed from a 12-21 cassette to a 11-21 and I've used the 11 a lot more than I thought I would, especially when getting blown along a dual carriageway with a tailwind

Neil

BeaconRuth

addicted to Langbar wrote:

Just after a bit of advice about the effect of gearing before investing in a new bike. Would having a 52/39 chainset make much difference in a time trial compared to a compact (50/34) or a triple? I live near lots of nice hills so don't want to sacrifice losing lower gears for no real benefit at the top end.

It all depends on how fast you're likely to go.

A 50x12 gear is 112.5" which would have you going at 30.0mph with a cadence of 90rpm. If there are likely to be occasions when you'll go faster than 30.0mph and you'd prefer not to spin above 90rpm then you'll need a bigger gear.

I don't know whether 30.0mph sounds fast to you but bear in mind, as Neil says, that many testers only need a bit of tailwind and a slight downhill to find themselves going that fast. If you're going to average 25mph then you'll probably spend a portion of most races at 30mph or above, even if only briefly. But if you think you average speed is likely to be lower, say 20-22mph, then you'll probably be fine with the 50 chainring.

How fast do you think you'll be going (on average)?

Ruth

John.T

I'm dead curious about the 56 ring - I need all the help I can get!

A bigger chain ring means you can use a bigger cog for the same gear ratio. The smaller percentage difference in size means that one tooth change alters the gear ratio by less so you get closer gears. There is also a small drop in friction some say.
Put a few examples in Sheldons gear calc and you should see.
http://sheldonbrown.com/gears/

sub55

John.T wrote:

I'm dead curious about the 56 ring - I need all the help I can get!

A bigger chain ring means you can use a bigger cog for the same gear ratio. The smaller percentage difference in size means that one tooth change alters the gear ratio by less so you get closer gears. There is also a small drop in friction some say.
Put a few examples in Sheldons gear calc and you should see.
http://sheldonbrown.com/gears/

hurray, at least theres someone on here that knows what they are talking about.

beyond that , by using a bigger chain ring , you move the chain ring further up the cassette. which in turn give you a wider range of usable gears ,which could well come in handy if you find yourself on a quick section of a course.
beyond that, having the chain in the middle of your cassette, gives you a straighter chain line. so your not permently wasting energy trying to straighten it out.
beyond that, the further you move the chain away from the centre of the axle, less force is exerted trying to pull the wheel towards you. that energy is then tranferred to the force required to turn the wheel over.
so forget the compact and get a 56, you will see the benefits.

BeaconRuth

sub55 wrote:

hurray, at least theres someone on here that knows what they are talking about.

beyond that , by using a bigger chain ring , you move the chain ring further up the cassette. which in turn give you a wider range of usable gears ,which could well come in handy if you find yourself on a quick section of a course.
beyond that, having the chain in the middle of your cassette, gives you a straighter chain line. so your not permently wasting energy trying to straighten it out.
beyond that, the further you move the chain away from the centre of the axle, less force is exerted trying to pull the wheel towards you. that energy is then tranferred to the force required to turn the wheel over.
so forget the compact and get a 56, you will see the benefits.

So the chain in the middle of the cassette, say 56x16, gives a 94" gear which at 90rpm gives 25.2mph............. what if the OP thinks he'll be doing more like 22mph on average? How can you possibly say a 56 is best for everybody without knowing how fast he will be going on average?

Ruth

andyp

sub55 wrote:

hurray, at least theres someone on here that knows what they are talking about.

beyond that , by using a bigger chain ring , you move the chain ring further up the cassette. which in turn give you a wider range of usable gears ,which could well come in handy if you find yourself on a quick section of a course.
beyond that, having the chain in the middle of your cassette, gives you a straighter chain line. so your not permently wasting energy trying to straighten it out.
beyond that, the further you move the chain away from the centre of the axle, less force is exerted trying to pull the wheel towards you. that energy is then tranferred to the force required to turn the wheel over.
so forget the compact and get a 56, you will see the benefits.

Dear god. Are you for real? :shock:

John.T

Ruth is quite right about speed and gearing. It is pointless having gears that you can not realisticaly use. If you have only one bike then fit the chainset that will be most use to you and make do on the TTs. You will loose very little time. If you have a dedicated TT bike then using a larger chain ring and cogs to give closer ratios is worth while. I have been doing TTs on a 50 for some time with no trouble (except lack of strength) but would probably go for a 55 with 13/23 on the back for a TT bike. The inner ring is pretty much irelevant except for hilly events.

kilo

John T , thanks for your explanation that i can see the logic in that - and agree with your later post.


["i]hurray, at least theres someone on here that knows what they are talking about." [/i]

Pleasant reply, perhaps you could refer back to the original question; "Would having a 52/39 chainset make much difference in a time trial compared to a compact (50/34) or a triple? I live near lots of nice hills so don't want to sacrifice losing lower gears for no real benefit at the top end. "

This is the question the other posters and i were trying to answer hence the debate about 50 chainrings as opposed to 52's, not what is the optimum chainring size for time trialing -sorry if our appaling ignorance has offended you.

addicted to Langbar

Thank you for your answers guys. Just found out that there is no pay rise for me this year so it looks like I'll have to make do with what I've got and get my legs to go faster.

John.T

If you have a wide ratio cassette you could get a BBB 11/21 and slip that on for TTs. You should get round the Pool Triangle on the big ring with that OK. Back in the 60s I just had a 52 ring and 14/18 5sp block. I managed 32 min for one lap and 1.1.32 for a 25 on there.

nmcgann

addicted to Langbar wrote:

Thank you for your answers guys. Just found out that there is no pay rise for me this year so it looks like I'll have to make do with what I've got and get my legs to go faster.

What a tease :roll: Just when we were all settling in for a long and pointless argument about gearing

Neil

addicted to Langbar

Sorry Neil,

My hopes of getting one of these has been dashed -

http://www.bikeradar.com/gear/category/ ... d-08-31982

I'll have to settle for trying to go faster on one of these -

http://www.vintagebicyclepress.com/imag ... shaker.jpg

It has definitely got faster since I fitted the clip on aero bars!