I have 20kph legs

[Oxo]

I had a boss who verbally abused me whenever I got things grammatically wrong. I still twitch in anticipation when I read something like that.

Feel free to have a go, after all, at this time of year it is better to give than receive.
I will/shall (you'll have to help on that one) be upset but I might get over it before the end of the year.

 

[mjr]

But I thought I would try and "Push" it on the way home on my 20km commute tonight. […]
Has anyone else found this with their riding?

Yes. "Pushing it" helps less than tucking down, getting more aero and spinning faster in a lower gear. Also, commute speeds are usually determined mostly by the junctions unless you can go so much faster to arrive at a priority junction a vehicle earlier or a signalised junction an entire cycle earlier (and with a 90s cycle 3miles from me, I'd need to average about 1.4mph faster before it does that). Long straight fen roads show the difference more readily than the commute into town.

 

[ColinJ]

Over the years i've slowly started to convert mph to kph. Watching stuff like the TdF you have to,otherwise you're left wondering how fast that rider is flying down that hill at. "He's doing 67 kilometers an hour" means bugger all if you can't convert it. So i now do the 10 k's is 6.2 m's in my head, So let me see, He's flying down that hill at 67 kilometers an hour, so that's six six's and er let me see60 percent of the 7 is about 4, so without looking it up it's around 40mph i reckon.

A much easier way to look at is that kph ~= mph * 8/5 and mph ~=kph * 5/8.

67/8 = 8 and 3/8. 5 * 8 = 40. 5 * 3/8 = 1 and 7/8 which is 2 - 1/8 which is about 2 - 0.13 which is 1.87 so 67 kph ~= 41.87. Call it just shy of 42!

My top speed on a bike was down Rossendale Rd from the Manchester Rd lights in Burnley. You probably know that descent? I did 56 mph or (56 * 8) / 5 ~= 448 / 5 = 448 * 2 / 10 = 896 / 10 or near enough 90 kph!

 

[nickyboy]

As we all know, wind resistance is the main thing stopping us going faster when you get up to speeds like 20km/hr. And we also know that wind resistance is proportionate to the square of the velocity.
So if you want to increase from 20 to 21km/hr (a 5% increase) you will experience 1.05 x 1.05 = 1.11.....11% more wind resistance. Also cos you're going 5% faster you're going to need 5% more power anyway. So in the end you need 1.05 x 1.05 x 1.05 = 16% more power....just for a 5% increase in speed

It's hard to go faster and similarly it's hard to go slower. I know on a long ride in the Peaks what my avg speed will be. And I'm rarely more than 0.5km/hr out at the end as the extra effort needed to go say 1km/hr faster would kill me

 

[Accy cyclist]

A much easier way to look at is that kph ~= mph * 8/5 and mph ~=kph * 5/8.

67/8 = 8 and 3/8. 5 * 8 = 40. 5 * 3/8 = 1 and 7/8 which is 2 - 1/8 which is about 2 - 0.13 which is 1.87 so 67 kph ~= 41.87. Call it just shy of 42!

Hell, that looks like one of those mathematical equations they used to have on those late night open university programs!!

 

[wonderloaf]

Hell, that looks like one of those mathematical equations they used to have on those late night open university programs!!

Where's the variable for colour, everyone knows that red bikes are faster.

 

[ColinJ]

Hell, that looks like one of those mathematical equations they used to have on those late night open university programs!!

Ok, here's an easier way ...

5 miles (per hour) for every 8 km (per hour).

If the distance/speed is not an exact multiple of 8 then there will be a remainder. Dealing with whole numbers only, a simple approximation for the remainders is ...

• 1 km ~= 0.5 mile
• 2 km ~= 1 mile
• 3 km ~= 2 miles
• 4 km ~= 2.5 miles
• 5 km ~= 3 miles
• 6 km ~= 4 miles
• 7 km ~= 4.5 miles

That is near enough for normal purposes. Not anally accurate, but fine for logging our general riding.

Using that method, here are some examples ... [x km ~= y miles (actual figure z to 2 decimal places)]

• 37 km ~= 23 miles (22.99 miles)
• 53 km ~= 33 miles (32.93 miles)
• 89 km ~= 55.5 miles (55.30 miles)
• 100 km ~= 62.5 miles (62.14 miles)
• 160 km ~= 100 miles (99.42 miles)
• 200 km ~= 125 miles (124.27 miles)

I'm happy with that kind of error.

 

[keithmac]

I just knock a 3rd off the kph to get approximate mph, near enough for me for what I use it for..

 

[Dayvo]

A much easier way to look at is that kph ~= mph * 8/5 and mph ~=kph * 5/8.

67/8 = 8 and 3/8. 5 * 8 = 40. 5 * 3/8 = 1 and 7/8 which is 2 - 1/8 which is about 2 - 0.13 which is 1.87 so 67 kph ~= 41.87. Call it just shy of 42!

My top speed on a bike was down Rossendale Rd from the Manchester Rd lights in Burnley. You probably know that descent? I did 56 mph or (56 * 8) / 5 ~= 448 / 5 = 448 * 2 / 10 = 896 / 10 or near enough 90 kph!

The EASIEST way, IMO, is to half the kilometre distance, for example 80 (40).
Divide the 40 by four (10) and add to the half total (40) to quarter total (10) and you get 50.

It's not 100% exact but near enough. And it's simple.

 

[Aperitif]

So complex! Memorise: 10m = 16k 20m = 32k 30m = 48k. Distance or speed per hour etc. If you're going any longer/faster then chances are that something or someone, somewhere is automatically making notes for you. In the meantime, do some easy division and addition!

 

[dim]

get a new bike, with decent wheels and tyres

on my Surly LHT, I average 20km/hr ... it's heavy and slow, has heavy tyres and stainless steel mudguards etc (but a pleasure to ride)

on my other 2 bikes, I am a lot faster for the same effort

 

[Joey Shabadoo]

meh

What's 40km/h in mph?

Halve the 40 = 20
Add a quarter of that = 5
Add the two together = 25

40 kmh = 25 mph

 

[Dayvo]

meh

What's 40km/h in mph?

Halve the 40 = 20
Add a quarter of that = 5
Add the two together = 25

40 kmh = 25 mph

That was how I did it.

 

[Joey Shabadoo]

So you did My bad

 

[screenman]

Close enough, unless you are heading for another planet.