BikeNube

I hope this topic hasn't been beaten to death here, but I was wondering where you all keep keep your power when you're going down hill vs up hill vs flat during a TT.

Say there were several , maybe (3%) 1 minute hill climbs in a for example, 9 mile TT you want to average 300 watts in.

What power up and over and what power down would you want to keep your power at?Holding wind constant, of course.

Nate552

Depends on whats at the top of the hill. If the hill crests to a flat section, then I don't go too much harder on the hill. However, if there is a downhill right after the hill then I go harder. How hard? depends on how I'm feeling.

kleinboogie

I'm big and I do better descending and on flats. I consider uphills payback to gravity for the help on the other side. I just try to stay near my climbing power and not blow-up. Worst situation for me is burning too much ascending and having to coast or under-power on the descent and flats. GL

mollusk

Paging RacerEx ... RacerEx ... Paging RacerEx ...

Truth be told it is quite complicated and really depends a lot on you. A lot depends on how long and hard you can go over threshold and how quickly you can recover. It is an almost certainty that going up short hills you will be better served going over threshold and getting recovery on the downhill part. The amount over threshold on the short hills for optimum performance depends a lot on you and how you react to it.

grolby

+1.

The math on this is pretty simple: going a little faster on the uphill does a lot more for your average speed than going a little faster on the downhill. And, of course, the converse is the same: losing a little time on the uphill hurts you worse than losing a little time on the uphill. So, just on the math, you're better off going harder uphill and recovering on the descent. But like mollusk says, it's complicated and depends upon you and your body. The best possible thing is to ride your TT setup a lot and do plenty of TT's, and you'll start to figure out what's faster. Time trialing rewards patience, practice and attention to detail; one of many reasons that I suck at them.

Racer Ex 

Did someone sacrifice a virgin? Or at least a goat? Because if you're going to summon me I want...blood.

It's going to depend in part on the individual, and as Nate pointed out, what comes after the climb will determine how you ride it. You can gain time going up a hill only to put yourself into a deficit that you'll never recover from if you are looking at a lot of flat/headwind after you crest.

Those of us who are looking at a second here or there being the difference between winning or losing never shrug the downhill off BTW; I bring a 56t big ring with me to quite a few TT's and use it as conditions might warrant.

Me, I want to see the actual course, the prevailing conditions, the wind outliers, and then formulate a strategy.

mollusk

Old joke:

Q: Why did the islanders always sacrifice virgins to the Volcano God?

A: Because virgins are no fun.

OptimalCycling

You mean a time trial power pacing strategy calculation that is similar to something like this?:



You can do these types of calculations with my Optimal Cycling program that I just released last week (first public release, it's a command line tool right now). It's the most advanced tool of its kind and can take into account things such as hills, wind, acceleration, varying CdA, varying power, varying CRR, power output limits, etc.... https://optimalcycling.com/power-pacing/

Nate552

I don't agree with the philosophy of going harder on the downhills. As your speed increases, the power required to go faster increases exponentially. Mainly due to drag. To increase from 20 to 25 mph, there is something like a 75% increase in the energy required to achieve that additional 5 mph.

"At 20 mph, four-fifths of your total power is already spent overcoming air resistance. To go 25% faster, you need to increase your total power by 83%." --cycling mathmatics

It's just not worth it, I'd rather expend the energy when my bike is going slow. (Obviously this doesn't apply to short TTs)

Nate552

Interesting, I'll enjoy looking this over, thanks.

OptimalCycling

If you are interested, I'll be posting up an article on my website later tonight that uses Optimal Cycling to calculate the optimal power pacing strategy for the 2km Stage 1 ITT of the Tour of Qatar 2011. It should be a good example for those interested in time trial pacing strategies and using Optimal Cycling to calculate them.

kleinboogie

Understood. That just doesn't work for me. I'd power up the ascent, essentially way over my threshold, and have nothing at the top and use the descent to recover. Over long, or even medium, rides I do much better holding a steady at or above LT effort over the whole ride. Maybe I need more matches but that's worked for me. Cheers

aham23

i have nothing to add. wrong thread. carry on. later.

Racer Ex 

It becomes a fairly complex formula. The other part of the math equation that gets overlooked is the watts required to gain additional speed going uphill... which can be pretty significant. For a 75kg rider the difference between 9 to 10 mph on a 10% grade is around 45w.

If you throw 300w at a hill only to be able to put out 220 for two minutes after you crest, the net might be negative, especially if you consider that you're not going to pop right back up to FTP.

One of the things I learned racing motorcycles is the speed you generate carries ahead to some degree. Ramping up to speed quickly on a downhill to the point of stasis between drag and gravity and you'll carry at least that stasis all the way down. Cresting then relying on gravity to get you up to stasis can be a long wait depending on the gradient.

And the ability to generate speed above that stasis carries a benefit when you leave the decline.

The key is modulating that uphill effort to allow for some reserve and to minimize any negative impact going forward.

rruff

It's always better to go harder on the uphills... it's just a question of how much harder. On 1 min climbs you should be able to go ~15% over FTP and recover on the downhills. Maybe more, but you'll have to experiment. Actually you would want to keep the power up over the crest of the hill until your speed has come up, then slack way off... you could probably drop down to 150W or so until you hit the next incline.

Try it and see what happens.