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Old 07-15-09, 08:45 AM   #1
dgearhart
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Anyone know an online calculator for calculating time gaps / chase speed requirements

I was in a 35 mile breakaway in a 55 mile RR this weekend which had a 2 min gap on the peloton at 10 miles to go. It was hard to calculate what distance/gap was required before we could ease up our pace. Does anyone have a simple calculator for "what if" scenario building? (i.e. 5 mi remaining - 1 min gap - peloton needs to ride + 2mph...or whatever it is...). Please post any spreadsheets or online calculators...I know the Pro Teams have all that stuff on computers, so it must exist somewhere on the internet.
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Old 07-15-09, 08:51 AM   #2
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Simple.

Don't. Ease. Up. Your. Pace.

You don't have the benefit of someone yelling in your ear to tell you that you've made it. I wouldn't trust the time gaps they give either. Just go.
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Old 07-15-09, 08:55 AM   #3
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I was in a 35 mile breakaway in a 55 mile RR this weekend which had a 2 min gap on the peloton at 10 miles to go. It was hard to calculate what distance/gap was required before we could ease up our pace. Does anyone have a simple calculator for "what if" scenario building? (i.e. 5 mi remaining - 1 min gap - peloton needs to ride + 2mph...or whatever it is...). Please post any spreadsheets or online calculators...I know the Pro Teams have all that stuff on computers, so it must exist somewhere on the internet.
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Old 07-15-09, 09:06 AM   #4
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my calculator isnt on line, but it always says "ease up just after crossing the finish line"
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Old 07-15-09, 09:31 AM   #5
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You need to know distance remaining and current speed + gap.

for example 10 miles to go, 2 min gap. If break and group riding around 20mph you have tons of time to chase them down, if everyone is doing 30, your pace has to be relatively higher.

I'm not sure how an online calculator is gonna help you while racing...
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Old 07-15-09, 09:35 AM   #6
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Simple time calculator should work. http://www.machinehead-software.co.u...time_calc.html

Make an assumption as to the average speed of the chase group. Calculate their time to the line. Then calculate the speed necessary to get there a few sections faster.

Problem is that the math is only as good as the assumption of the speed of the chase group.

Of course unless you're planning to do this on your Iphone while riding, its not going to do you a lot of good absent a coach in a car, and a radio.
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Old 07-15-09, 09:39 AM   #7
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A moe practical way to do this if you're getting updated times, is to observe the burn rate, i.e. how many seconds are they closing each mile.

Of course that's likely not to remain constant so simple extrapolations could be dangerous.
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Old 07-15-09, 09:44 AM   #8
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I'm not sure if this helps by I use a 1 foot per second per mph rule. It's actually 1.4 but I can't calculate tenths at threshold.

If someone is 100 yards up the road travelling at 25 mph. I have to go 26 mph for 300 seconds or 28 mph for 100 seconds. Since I can do neither, I sit in.
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Old 07-15-09, 09:45 AM   #9
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I think Paul Sherwin always says the chasers can gain about 1 minute per 10 kilometers, at least for the TdF riders. Ymmv.

So with a 2 min gap and 16 km left, by his calculation you should be able to hold off the peloton. (By not easing up the pace, of course)
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Old 07-15-09, 10:10 AM   #10
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Simple.

Required average speed = Distance to catch the break / ((distance to catch/avg. break speed) - time gap)

Keep all the units in hours and it works out.

So say there's 22k to go with a 6 minute lead (0.1 hours), break moving at 40 kph, you want to catch them with 2 to go, distance to catch = 20km.

20 km / ((20km / 40 kph) - 0.1 hours) = 50 kph to catch them in 20km.
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Old 07-15-09, 10:16 AM   #11
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The formula: (V2 - V1)/(V1 * V2)*3600 will give you the change in gap time per mile in seconds where V1 and V2 are the lead and chase group's speed in mph.

In your example if the pack is chasing at 30mph and you were riding at 27 they would gain 13.3 Secs/mile and you would be caught. A reasonable approximation is to multiply the speed difference by 4 or 5.

The formula and calcs are the simple part of course. The difficult part is getting a reasonable estimate of the chase group's speed which is a function of their capability and motivation. In the tour it is much simpler because they know the speeds of each group in real time.
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Old 07-15-09, 10:25 AM   #12
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Why on earth would you want to ease up? Are you trying to save yourself for another day of amateur cycling? Push it to the line.
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Old 07-15-09, 12:13 PM   #13
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OK, for all those blasting about "why" you'd ever ease up, it is for a couple reasons.

1. We finished a 55 mi road race with a 2+ min gap on the field. Yes, we all had a crit to do the next day and widening the gap really makes no sense at some point. We were getting time splits from the marshal on the motorcycle that were growing by about 10 sec every couple miles...however, that left us pretty spent for the next day's crit and was not needed. Several riders suggested that a Masters 35+ div race with a 2 min w/ 10 mi to go is pretty much over on a rolling hill course assuming there were a few teams represented in the break so chasing would be "somewhat" contained. A simple calculation would allow me to know that at 2 min with 10 miles remaining, I can go safely 1mph slower than the pack and be fine, or whatever......make sense?

2. There was some game playing in the group with workload. Had I known that a 2 min gap was more than enough when we hit 10 miles and again at 5 miles, I could have eased up a bit on the rotation and left something for the sprint finish since we were not going to get caught at 5 miles with 2 minutes or 3 miles with 2 minutes....or whatever number I could calculate to myself, "OK, we've got this, let me conserve a bit for the sprint." In my group of 4, all the others were doing that pretty early, but I wanted to make sure we didn't get caught. However, I would have liked to have a "guestimate" calculation for knowing when the "fat lady is warming up".....

There were a couple good formulas given, and I appreciate those who tried to answer the question. We can kill the thread now.
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Old 07-15-09, 01:17 PM   #14
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There was some game playing in the group with workload.

This is really the relevent point. What you need to know is whether you have to go all out to drive the break to make sure it stays away, or are you at the point where the break is going to survive, you can let off effort, and begin working on setting up, o attacking, your breakaway companions.


If you start dicking around too soon, everyone is caught. You work too hard, your cooked and lose to one of your companions.


So just how hard you need to work for the break to survive is relevent information.
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Old 07-15-09, 01:51 PM   #15
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Yes, Merlin gets my question 100%. Thanks for clarifying.
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Old 07-15-09, 01:53 PM   #16
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I took the formulas that you put on this thread and threw together some basic TDF calculators. If there are any errors, let me know. I hope this proves useful to some of you.

TDF Calculators
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Old 07-16-09, 01:20 PM   #17
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I'm not sure if this helps by I use a 1 foot per second per mph rule. It's actually 1.4 but I can't calculate tenths at threshold.

If someone is 100 yards up the road travelling at 25 mph. I have to go 26 mph for 300 seconds or 28 mph for 100 seconds. Since I can do neither, I sit in.
I think your calculations are too conservative.

1 mile = 5,280 feet.

5280 ft. / 60 (minutes) = 88 feet per minute

88 feet = 29.33 yards (roughly 30 yards)

Therefore, if you are travelling 1 mph you are travelling roughly 30 yards per minute.

If you are travelling 1 mph faster than the guys up the road, you are catching up to them at a rate of 30 yards each minute.

So in your example of someone who is 100 yards up the road travelling at 25 mph., you would have to go 26 mph for 200 seconds (not 300 seconds), i.e. 3.33 minutes, not 5 minutes.

Bob
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