Maintaining a rolling speed

[DaveReading]

For example picture a hill that is 7 miles long, and you go at up at 7mph then down at 21mph. It will take you 1 hr to get up and 20 mins to get down, so 1:20hr total for 14 miles so that is 10.5 mph if I've got my sums right.

Another way to look at it is this: if your climb is at half your average speed up to that point, then even descending at light speed won't get your average speed back on track (assuming the climb and descent are of equal length).

Or put even more simply, you never get back on the descent what you lose on the climb.

 

[vickster]

I base mine on strava which is a moving average through the iPhone

 

[Big Nick]

That's not actually true though.

For example picture a hill that is 7 miles long, and you go at up at 7mph then down at 21mph. It will take you 1 hr to get up and 20 mins to get down, so 1:20hr total for 14 miles so that is 10.5 mph if I've got my sums right.

Ruddy hell a hill 7 miles long, I wouldn't be on that in the first place!!

The maths is mind boggling! So how fast would you have to come down then to maintain your 15 mph average ??

The whole length of the ride needs to the factored in, if you spend an hour riding up hills at 7mph you've covered 7 miles. If you then spend an hour doing 21mph you've done 21 miles. So 28 miles covered in the above 2 hours means you'll recover your average I think???!!!

My head hurts!

 

[livpoksoc]

I often suspect that people base their average speed on what they keep seeing when they glance at their computer - if it always seems to say 14 mph that doesn't necessarily mean your average is 14 mph, it will probably be a bit lower. And as DaveReading says, it's easier to drag the average down than it is to pull it back up.

Avg taken from my edge 200 & is same as when I loaded it to Strava.

Have found a group near me so will hopefully be able
To join them this weekend & join them for a 40 miler at a 14mph pace.

 

[jefmcg]

Ruddy hell a hill 7 miles long, I wouldn't be on that in the first place!!

The maths is mind boggling! So how fast would you have to come down then to maintain your 15 mph average ??

The whole length of the ride needs to the factored in, if you spend an hour riding up hills at 7mph you've covered 7 miles. If you then spend an hour doing 21mph you've done 21 miles. So 28 miles covered in the above 2 hours means you'll recover your average I think???!!!

My head hurts!

Yes, but we are talking about averaging it over a hill. so you go up the hill at 7pm, get to the top in an hour. up and down again is 14miles, so to bring your average back to 14mph for the hill, you need to get to the bottom immediately.

If you go up at, say, 10mph, then you get to the top in 42 minutes and you have 18 minutes to get down. so that's around 24mph down.

 

[Big Nick]

Yes, but we are talking about averaging it over a hill. so you go up the hill at 7pm, get to the top in an hour. up and down again is 14miles, so to bring your average back to 14mph for the hill, you need to get to the bottom immediately.

If you go up at, say, 10mph, then you get to the top in 42 minutes and you have 18 minutes to get down. so that's around 24mph down.

Ultimately though, who cares!

 

[Rob3rt]

Ruddy hell a hill 7 miles long, I wouldn't be on that in the first place!!

The maths is mind boggling! So how fast would you have to come down then to maintain your 15 mph average ??

The whole length of the ride needs to the factored in, if you spend an hour riding up hills at 7mph you've covered 7 miles. If you then spend an hour doing 21mph you've done 21 miles. So 28 miles covered in the above 2 hours means you'll recover your average I think???!!!

My head hurts!

Absolutely...

 

[jefmcg]

Ultimately though, who cares!

people who need to average a certain speed to avoid the sag wagon, which is the point of the thread

(personally, I find the maths interesting. It seems intuitively obvious that doing a distance at one speed and the same distance at another speed, then the average should be the mean of the two numbers. )

 

[NorvernRob]

Avg taken from my edge 200 & is same as when I loaded it to Strava.

Have found a group near me so will hopefully be able
To join them this weekend & join them for a 40 miler at a 14mph pace.

Are you having any stops along the way and leaving the Garmin running without auto pause?

 

[TheJDog]

(personally, I find the maths interesting. It seems intuitively obvious that doing a distance at one speed and the same distance at another speed, then the average should be the mean of the two numbers. )

Yes, it's the time spent doing a low speed that needs to be countered by spending the same amount of time at the same amount over the average speed. Obviously that means doing a much greater distance fast if you've been slogging up a steep hill very slowly.

If the distances up and down are the same, the theoretical maximum average over the hill is only twice the average speed of your climb. So if you climb it at 6mph, you can only drag your average up to 12mph over the whole hill by descending it instantly. Which does seem strange.

 

[Big Nick]

people who need to average a certain speed to avoid the sag wagon, which is the point of the thread

(personally, I find the maths interesting. It seems intuitively obvious that doing a distance at one speed and the same distance at another speed, then the average should be the mean of the two numbers. )

Sounds like a top night out!

 

[srw]

people who need to average a certain speed to avoid the sag wagon, which is the point of the thread

(personally, I find the maths interesting. It seems intuitively obvious that doing a distance at one speed and the same distance at another speed, then the average should be the mean of the two numbers. )

Intuitively obvious, but as @TheJDog almost points out, wrong. Speed is a time-weighted measure (distance divided by time), so you need to think about the time you've spent doing each bit, not the distance you've done.

It is, honestly, interesting.

In this context, if you're spending half an hour slogging two miles up Leith Hill at 4mph you need to spend half an hour pelting along on the flat (or downhill) at 19.5mph to make the average up to the required 11.8mph. In that half-hour you've got to do nearly 10 miles. If you've spent half an hour with your feet up having a sit down you've got to spend half an hour doing 23.6mph. In that half-hour you've got to do nearly 12 miles.

I suspect my beloved stoker wishes I hadn't set the maths out in quite that way. As, to be honest, do I.

(OK, Leith Hill itself is only a mile, but Box Hill is a bit longer, as is the hill up to Newland's Corner. Fortunately there are plenty of very wide, fast roads to make up, and with two of us on the bike we win downhill, even if we lose uphill.)

 

[livpoksoc]

Are you having any stops along the way and leaving the Garmin running without auto pause?

Not sure if it's auto pausing, but yes initially I stopped every 8 or so miles, second time I stopped every 12, I reviewed it on rwgps the other night & the route only has one flat section in the middle when I loop around Alton, then I come back (albeit with a couple of deviations) along the same hilly route.

 

[stu9000]

Probably you should ask this over here .... http://www.cyclechat.net/threads/ridelondon-surrey-100-2014-anyone.137105

This was the setup

Ok thanks! What were the facilities like for breaks etc. (i.e. Roughly how many were available, rough dist between them & what was on offer in terms of refreshment?).

Last years map has the stopping points marked on.
https://www.google.co.uk/url?sa=t&s...cQFjAA&usg=AFQjCNETiC488FBA4MwPqHnb_DPI2xzxAw