Compact vs Standard double for sprinting

[winstonw]

Cadence and Speed for 23-622 clincher, inflated to 120psi, diameter 209mm with rider and 1/2 filled drink bottle.

[Chris249]

="Alex Simmons/RSTI've won A grade on the Eastern Creek downhill sprint and was in the 53x13.

Damn, there goes my excuse for getting rolled in the finish sprint there last Sunday in 52 x 13! Bugger bugger bugger!

Compact criticism is just another form of elitism. Which is common in road cycling...

Is it? I've turned up to races and TTs with a $799 (new price) Sora/2200 roadie or an old $600 TT bike, Katmandu jersey, MTB shoes and cheap Cell knicks, and never had a single elitist remark. All the club and ATTA events have been very welcoming and everyone has been very friendly.

[ft_critical]

I've won A grade on the Eastern Creek downhill sprint and was in the 53x13.

how fast, what cadence?

The B and sometime C grade sprints are faster than A grade in my experience.

[sogood]

Cadence and Speed for 23-622 clincher, inflated to 120psi, diameter 209mm with rider and 1/2 filled drink bottle

Said rider deserved to lose the sprint for over estimating his hydration requirement!

[winstonw]

Said rider deserved to lose the sprint for over estimating his hydration requirement!

Or deserved to lose the sprint for not drinking all of his hydration requirement, which is probably more common.

And if he drank the half bottle 10-15 minutes pre sprint, the weight on the tires in the sprint would be close to what it was by not drinking it.

[diggo19]

i always max out.. if the hill is big enough

[sogood]

And if he drank the half bottle 10-15 minutes pre sprint, the weight on the tires in the sprint would be close to what it was by not drinking it.

That assumes,
1) There's no water loss during the drinking phase, which we know happens regularly.
2) The rate of insensible fluid loss is identical between the two hydration states of said rider, which may not be true.
3) A fuller stomach will alter the aero profile of said rider, affecting the sprint outcome.
4) Risk of stomach upset by that 1/2 bottle of water.
5) Weight on tyre is a determinant of sprint success.

[sblack]

I have raced the same two courses on both a 12-25 and an 11-23 on 172.5 cranks and a 39/53 Chainring set. Both times I raced the 12 I ran out of gearing. At West Head, solo, chasing the break into Salvation Creek and a second time at Eastern Creek in the sprint finish (68kmh, 158rpm is my best sprint here on a 11-23 by way of reference.)

Is there are typo in there somewhere? If not then maybe it's time to replace the 20 inch wheels.

[Alex Simmons/RST]

The B and sometime C grade sprints are faster than A grade in my experience.

Quite possibly, but when you aren't exactly smashing yourself much before the sprint, that's no surprise. That was my point about the pros sprint power. Per se it's not that spectacular. But after smashing yourself, it is damn fine work.

I've won A grade on the Eastern Creek downhill sprint and was in the 53x13.

how fast, what cadence?

Actually I was wrong. I was in the 53x14, not the 13.
So I still had a 13, 12 and an 11 cog left. At Heffron I don't think I go past the 14 much, if ever. I won there on junior gears one day as I got a spare rear after a puncture. Might have even been in the 15.

Not that fast really, only 63-64km/h but only 3 of us and a longish sprint. 130 rpm. I was just smarter. I'm sure not a sprinter, I lost a heap of top end when they cut my leg off. I wasn't a sprinter before that either.

[ft_critical]

I have raced the same two courses on both a 12-25 and an 11-23 on 172.5 cranks and a 39/53 Chainring set. Both times I raced the 12 I ran out of gearing. At West Head, solo, chasing the break into Salvation Creek and a second time at Eastern Creek in the sprint finish (68kmh, 158rpm is my best sprint here on a 11-23 by way of reference.)

Is there are typo in there somewhere? If not then maybe it's time to replace the 20 inch wheels.

No typo sblack, but fair to call it out. This is from my notes, and at the time I was only using a PRO wireless computer. So the top speed is accurate, but I don't know when that 158 was printed. Whilst not a lie, it was just the top rpm on the PRO computer for that day. But owing to your keen eye I checked two recent Garmin sprints, I don't know the gears but not more than a 12, probably a 13, but at 100rpm I was at 55, and at 110 at 62, both flat. And, I don't think I can spin faster than about 130 anyway. So let's call 158rpm bull. Thanks for keeping it honest.

[mikesbytes]

I'm sure you could spin faster FT. The 158 was probably bad data, perhaps a spike like those sometimes seen on heart rate monitors. At one gym I have been using spin bikes that have readouts and the cadence on them is wrong, on one bike it was reading 130 when I was doing 136 and another it exceeded 140 (where it cuts out) when I was doing 132, one bike read 110 when I was doing 130. Anyway the point being that it makes me wonder about the accuracy of bike computers.

Back on topic, when I first started club riding in a situation like the Sutherland sprint, I would run out of gearing on my 52-12. In a nutshell I had crap cadence ability. When I switched to 53-11 the problem went away. From what Alex has written, I'm guessing that nowadays I am similar to him when it comes to cadence, so I'd say that in a sprint, even downhill, a compact would not be an issue for me. However I also have no need for any gear lower than 39-25

Alex, some questions;
1. You corrected yourself to saying you were using the 14 in the A grade sprint, do you keep data on your gears? If I remember correctly there was a tail wind down the straight.
2. You have noted that max power comes out in the 130 - 140 range, have you got any more info on this? I'm also interested in this figure from a training viewpoint

[sblack]

I have raced the same two courses on both a 12-25 and an 11-23 on 172.5 cranks and a 39/53 Chainring set. Both times I raced the 12 I ran out of gearing. At West Head, solo, chasing the break into Salvation Creek and a second time at Eastern Creek in the sprint finish (68kmh, 158rpm is my best sprint here on a 11-23 by way of reference.)

Is there are typo in there somewhere? If not then maybe it's time to replace the 20 inch wheels.

No typo sblack, but fair to call it out. This is from my notes, and at the time I was only using a PRO wireless computer. So the top speed is accurate, but I don't know when that 158 was printed. Whilst not a lie, it was just the top rpm on the PRO computer for that day. But owing to your keen eye I checked two recent Garmin sprints, I don't know the gears but not more than a 12, probably a 13, but at 100rpm I was at 55, and at 110 at 62, both flat. And, I don't think I can spin faster than about 130 anyway. So let's call 158rpm bull. Thanks for keeping it honest.

Thanks ft-critical, those numbers make better sense, pretty much right for a 53x12 combo. What data do you have on the times you felt you'd run out of gearing with the 53x12? That'd give better details on what cadence you feel you spin out at and maybe provide a better estimation of how you'd go with a 50x11 (bringing it all back to the 53 vs 50 originally asked). From what you provided so far it would seam it's somewhere in the 120-130 range, where the 53x12 combo may not allow you to hit your 68 km/h sprint but a 50x11 could. It would be interesting to see how you'd go on those same courses with a 50x11.

[winstonw]

That assumes,
1) There's no water loss during the drinking phase, which we know happens regularly.
ok let's presume 30mls makes its way into the jersey but that's still weight on the tyres, and another 30ml gets tossed with the bottle.
2) The rate of insensible fluid loss is identical between the two hydration states of said rider, which may not be true.
it's possible he sweats more in the underhydrated state, considering he will be shunting heat less effectively. Hard to say which state retains the greater weight.
3) A fuller stomach will alter the aero profile of said rider, affecting the sprint outcome.
any aero disadvantage of a fuller stomach will be offset by having tossed his water bottle.
4) Risk of stomach upset by that 1/2 bottle of water.
true. ideally if sweat rate was 1L/hr, 300mls should be taken in over 20 minutes
5) Weight on tyre is a determinant of sprint success.
I've never witnessed a constant speed sprint, so I'll presume acceleration, hence weight, matters.

Regarding max power occurring around 130-140, my googling says TdF sprints are commonly around 110-125.
As Alex says, maybe they are just too shagged after 200+km.
And is anyone efficient doing 130-140 out of the saddle?

An interesting power readout for Andre Griepel in final 5 minutes of Stage 7, TdF 2011. He finished 3rd behind Cavendish and Pettachi.
http://www.srm.de/images/stories/Tour_de_France_2011/Stage_7_Greipel/tdf%202011%20s7%20greipel%205%20k.gif

Andre developed 1680w peak power at ~117 cadence, to achieve 72kph.
Extrapolating to determine gear, that cadence and speed fit nicely with 53/11.
Thought about calculating what total weight leads to 72kph at 1680watts, but acceleration and unknown slope make it too hard.

[sogood]

...too hard.

Still a good try though!

[winstonw]

Still a good try though!

OK, after giving my brain a rest
Wiki says Andre was/is 6ft and 75kg
UCI min bike weight is 6.8kg.
So let's say Andre 75 kg; bike 7kg; shoes, clothes, power meter, helmet, misc 0.5kg = 82.5kg.

On a perfectly flat smooth course with no wind, steady state 72kph requires 1566 watts.
But
- it only takes a 0.7% gradient (0.7metre over 100metres) to push that out to 1680 watts.
- he was still accelerating during peak power, and acceleration requires additional power to steady state (there's a formula but I can't be bothered now)

[Alex Simmons/RST]

Anyway the point being that it makes me wonder about the accuracy of bike computers.

Of all things, cadence is the easiest thing to measure on a bike, so you have to wonder about whatever is hooked up to those bikes.

Alex, some questions;
1. You corrected yourself to saying you were using the 14 in the A grade sprint, do you keep data on your gears? If I remember correctly there was a tail wind down the straight.

Don't need to, speed and cadence tells you what gear you are in. You can plot it if you like.

2. You have noted that max power comes out in the 130 - 140 range, have you got any more info on this? I'm also interested in this figure from a training viewpoint

It's pretty common finding in the science studying maximal power development. We are talking very short range power here. Here's an item that might be of interest:
http://www.trainingandracingwithapowerm ... om_07.html

Note figure 4.
Maximal power at a circumferential pedal velocity of ~ 2.5m/s
On 170mm cranks that's ~ 135-140 rpm

[Alex Simmons/RST]

Regarding max power occurring around 130-140, my googling says TdF sprints are commonly around 110-125.
As Alex says, maybe they are just too shagged after 200+km.
And is anyone efficient doing 130-140 out of the saddle?

We are talking short range maximal power.
TdF and other pro roadie sprints are not about maximal power, and the sprints are long, hence the lower average cadence.