Hills vs Flat

[Grarea]

I wondered if there was a kind of general rule for hills vs flat?

I know that it will vary so much due to the amount of effort you put into the hill and your weight and so on and so forth.
But maybe just a kind of 'ish'.

I just can't justify a power meter just to answer my curiosity on that point.
Has anyone got any real life datas(?)

Like for eg if you have a 10% hill and x amount of watts on the flat is 15mph and the same amount of watts is x mph up said hill for example?

I am curious as I don't have much flat around me.
I know that hills knacker me by about 4-10x but i push harder up the hill.

[meic]

I cant say much about any specific hill or instant on that hill.
You can make predictions for a longer ride though, using Naismith's rule.
This helps to estimate ride times by using your normal flat cruising speed and adding an hour for every "so many" 100 metres. I found that it worked very well as a predictor once you had good figures for your speed and the climbing which cost you time. You work them out and fine tune them from results of previous rides. Strangely the amount of descent makes no noticeable difference, possibly because what goes up goes down on average over a ride.

Another thing, about capability, I find when trying to prejudge if I am fit enough for a ride, the amount of climbing matters more than the distance.

[thirdcrank]

I think one point is that unless you are in competition, you are perhaps unlikely to be riding on your limit on the flat, where you soon can be up any decent sort of hill. I mention this because if you know your limit on the flat, then the extent that you need to change down while climbing using a similar style - ie not standing up and grinding out the last ounce - should give a reasonable idea of the difference in effort.

I think meic has it right about hills, although it doesn't necessarily apply on tricky descents. I think of climbing as money in the bank, to be enjoyed later freewheeling but if the descent means keeping a tight hold of the brakes, a lot of the investment is lost.

Wind is the other biggy. It's amazing how often there's a head wind blowing from every direction.

[Norman H]

Try inputting a few numbers into this.

[foxyrider]

My general rule is 25% - add that to time for a hilly route and subtract the same for distance/time. It seems to work for most stuff I ride although I change to 30% for the alps. When I look at all sorts of rides (touring/sportives etc) it generally works out fairly close for similar intensity rides.

Not very scientific but the accumulation of many thousands of kilometres and rides over some 40+ years.

[Grarea]

My general rule is 25% - add that to time for a hilly route and subtract the same for distance/time. It seems to work for most stuff I ride although I change to 30% for the alps. When I look at all sorts of rides (touring/sportives etc) it generally works out fairly close for similar intensity rides.

Not very scientific but the accumulation of many thousands of kilometres and rides over some 40+ years.

Excellent, thanks for that.
I don't really have any flat near me, so it is either up or down.
I can't get far enough to find the flat yet.

and also:

Try inputting a few numbers into this.

Nice one, that will keep me quiet for a while. Excellent fun.
Having put in some numbers and just changed the gradient on the chart, for the same wattage,
speed goes from 23.47km/h to 6.45 km/h for a change from 0 to 5% gradient.
Calories used over an 11km distance changes from to 675 to 2456.
So a 5% is 4x harder than 0%. Haven't decided about how to build in the downhill, but I guess you have burnt the calories haven't you?
You don't get them back going downhill.
So, double the calories for the flat, makes it 1350 vs 2456 calories.

[eileithyia]

Well I time trial have a power meter and am currently in Mallorca, when I TTI am looking at riding at around top end of 150-160/5 watts, on the flat non-TT it would be around 100w. The climbs in Mallorca are longish and steady-ish, I usually find I am climbing them at around 150-154w or there abouts. But my speed certainly does not equate to the speed I can put out on the flat in a TT... more likely to be around 6-8mph

[foxyrider]

My general rule is 25% - add that to time for a hilly route and subtract the same for distance/time. It seems to work for most stuff I ride although I change to 30% for the alps. When I look at all sorts of rides (touring/sportives etc) it generally works out fairly close for similar intensity rides.

Not very scientific but the accumulation of many thousands of kilometres and rides over some 40+ years.

Excellent, thanks for that.
I don't really have any flat near me, so it is either up or down.
I can't get far enough to find the flat yet.

and also:

Try inputting a few numbers into this.

Nice one, that will keep me quiet for a while. Excellent fun.
Having put in some numbers and just changed the gradient on the chart, for the same wattage,
speed goes from 23.47km/h to 6.45 km/h for a change from 0 to 5% gradient.
Calories used over an 11km distance changes from to 675 to 2456.
So a 5% is 4x harder than 0%. Haven't decided about how to build in the downhill, but I guess you have burnt the calories haven't you?
You don't get them back going downhill.
So, double the calories for the flat, makes it 1350 vs 2456 calories.

One thing I didn't mention - the degree of fatigue. Clearly there will be some fall off in power over the course of a ride which will affect both calorie burn and speed.

From experience I factor this in as part of my distance/terrain 'calculation'. Works quite well for whatever riding i'm doing - If i'm uncertain of the exact terrain I err on the hilly side then i'm surprised how quickly i've covered the ground.

[Vorpal]

Unfortunately, lack of fitness and excess weight make more difference going up hill than anywhere else. Certainly, if I have lost some fitness, or been ill, I notice it first & worst on the hills.

Home to work is a 300 metre climb for me, and there is a big difference in my fitness between doing it every day and doing it once or twice per week. And when I was off the bike for two months a couple of years ago due to injury, when I went back to it, I was huffing & puffing, and still being overtaken by grannies on town bikes.

Looking at it in terms of time....
When I am fit, the trip to work takes 48 minutes, and home takes 33
When I am not fit, the trip to work takes me 65 minutes, and home takes 45

I can do it faster (for both conditions), if I really try hard, but those are the times that it takes, if I go at the rate which is fairly comfortable for me. It will still leave me sweaty when I get there, and puffed on at least the steep sections, but able to easily carry on a conversation for 60 - 80% of the ride (maybe less when I'm not fit). The bike I'm riding, weather, and tyres can also make a small difference, though studded tyres adds about 10% to my times, even if I don't encounter much in the way of snow & ice.

[pwa]

I wonder if the difference in time and effort taken to cover a set distance in hilly terrain, versus flat terrain, is due to the braking you have to do in the hills. It is rare to find a hill on which the climb is rewarded with a descent on which you can simply let the bike go and get the effort-free distance that the previous climb deserves. So some of your energy ends up making your brakes warm.

[Grarea]

I have just been playing with numbers on that chart.
I was wondering about the gradient of the hills I cycle on.
Is there an accurate way to measure them?

I toyed with google maps, but begun to wonder how accurate it is.

Is there a decent way of working it out?

I guess the best way would be an accurate wheel mounted mileometer and counting the contour lines on a detailed map.
But, given my laziness and level of apathy, I am happy enough with something within 5-10%.

I guess thinking like that, google maps is probably within that level isn't it?

[squeaker]

A rough sum shows that the effect of gradient is 0.1W/kg/m/s/% gradient.

So 100kg rider plus bike going up a 4% gradient at 9mph (4m/s) needs to output an extra 160W compared with the same conditions on the flat - which explains a lot

[Mick F]

............ only if he does the same speed?

It has been stated by "experts" ......... and I sort of agree .......... that the output of a cyclist should be constant. Change gear and therefore speed to suit the terrain.

If you get out of breath climbing a hill and it hurts, you are in too high a gear.
Relax, and enjoy the hills.

[Vorpal]

............ only if he does the same speed?

It has been stated by "experts" ......... and I sort of agree .......... that the output of a cyclist should be constant. Change gear and therefore speed to suit the terrain.

If you get out of breath climbing a hill and it hurts, you are in too high a gear.
Relax, and enjoy the hills.

Everybody runs out of gears eventually

[Mick F]

Everybody?
Not sure about that.
Mine go down to 16" on the Moulton and I think that Tigerbiten of this forum goes even lower.

16" on a steep hill is ok. 25% hill or steeper is fine, but there's a lane round here at 25% but with grass and mud up the centre of the road. This gives maybe eighteen inches of tarmac to ride on, and going slow in 16" make me wobble a bit, so I tend to use a higher gear and go faster ........... and therefore get out of breath.

If the road was wider to allow a weave and a wobble, 16" will get me up just about any road I've ever come across without much effort ......... so long as I take my time.