False Hills or Climbs

[PaulSB]

I realise this isn't really a technical question but I can't see where else to ask.

On my local training runs I have two false climbs. By this I mean despite being able to see I'm riding up hill I'm either accelerating or at least maintaing speed. These are not short bumps. Occasionally I come across this when further afield.

A friend who is a fell runner says he encounters the same thing. His theory is the power output / effort perfectly matches the gradient in this situation and helps maintain speed / pace.

Two questions then do people think his theory is correct and is it possible to change riding style to gain this benefit more often?

 

[amaferanga]

If it looks like a hill, but your speed doesn't decrease for the same effort then it's not a hill. Some kind of optical illusion probably. Try riding it in the other direction and see how it seems that way.

 

[oldfatfool]

As above, it is just the lay of the land giving the your brain the illusion that it is a hill.

False flats are more usual.

 

[ColinJ]

These are optical illusions.

There are several deceptive stretches of road that I can think of round here.

There is a false flat on the A646 between Burnley and Todmorden. It looks flat but it actually rises at about 2%. (It is obvious coming the other way). 2% isn't steep, but when tired after a long ride, I have often crawled up that drag and wondered why I am going so slowly.

There is also a climb above Hebden Bridge that looks a lot steeper than it actually is. It comes straight after a steepish climb up to a RH bend (from the Hare and Hounds in Old Town, heading towards Midgley). The road appears to be climbing as steeply as before but I can accelerate up the second section in the same gear that I was grovelling in just before the bend.

The most dramatic example that I can remember was in Snowdonia. My g/f and I had gone for a ride on hire bikes and came to what looked like a 4-5% climb but our speed kept going up. It wasn't long before we were doing close to 30 mph. It was the most bizarre thing I have ever experienced on a bike. My brain was telling me that we were climbing but we were clearly on a significant descent. I'm sure it was just misleading visual cues from the slopes of the surrounding hillsides, treelines etc.

 

[PK99]

There is a false flat on the A646 between Burnley and Todmorden. It looks flat but it actually rises at about 2%. (It is obvious coming the other way). 2% isn't steep, but when tired after a long ride, I have often crawled up that drag and wondered why I am going so slowly.

c.

putting some numbers on that:

150lb rider on the flat @ 15mph = ~100W

on 2% slope = ~ 200W

http://bikecalculator.com/wattsUS.html

 

[Red Light]

It could be what are known as Gravity or Magnetic hills. The more spectacular ones are listed.
http://en.wikipedia.org/wiki/Gravity_hill

 

[ColinJ]

putting some numbers on that:

150lb rider on the flat @ 15mph = ~100W

on 2% slope = ~ 200W

http://bikecalculator.com/wattsUS.html

That sounds about right. It feels like the brakes are dragging - enough to make it feel harder than it should, but not enough to be an obvious climb. Streetview of it.

 

[Red Light]

That sounds about right. It feels like the brakes are dragging - enough to make it feel harder than it should, but not enough to be an obvious climb. Streetview of it.

Looking at the contours on the OS1:25,000 map it looks like it could well be slightly downhill. The easy way is to try a roll test - starting from stationary does your bike roll forwards or backwards under gravity - or to take a spirit level with you and find the slope direction.

 

[ColinJ]

Looking at the contours on the OS1:25,000 map it looks like it could well be slightly downhill. The easy way is to try a roll test - starting from stationary does your bike roll forwards or backwards under gravity - or to take a spirit level with you and find the slope direction.

Well, it isn't a consistent gradient, but overall there isn't any question about it, it rises up about 40 metres over 2km or so. It is a slow drag going away from Burnley, and it is easy to do 25-30 mph in the other direction - it just doesn't look that way!

 

[Cyclopathic]

I tend to find most roads are uphill. I just thought that's how cycling works...All uphill.

 

[ColinJ]

I tend to find most roads are uphill. I just thought that's how cycling works...All uphill.

... into a headwind!

 

[Red Light]

Well, it isn't a consistent gradient, but overall there isn't any question about it, it rises up about 40 metres over 2km or so. It is a slow drag going away from Burnley, and it is easy to do 25-30 mph in the other direction - it just doesn't look that way!

I bow to local knowledge.

 

[Red Light]

... into a headwind!

....an againsterly headwind.

 

[ColinJ]

....an againsterly headwind.

An, er, 'forerly' headwind would be a tailwind!

 

[Cyclopathic]

Often against two headwinds.