# Speeds on Strava



## Andywinds (24 Aug 2015)

Hi all,

I've been looking at some of the segments on Strava and some speeds on downhill sections. I was suprised to see that on certain routes near me some were hitting over 50mph. I've gone through some of these at 40mph and thought if I miss-judged a corner I'm in trouble. Also to add a lot of these segments go through 30 zones. Surely even at 40 the stopping speed on a road bike is terrible? Plus going downhill would make stopping harder.


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## Karlt (24 Aug 2015)

No, not really. There's a downhill near me where you can get to 45 pretty quick and I can be down to 15 for the bend at the bottom in a few seconds.


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## young Ed (24 Aug 2015)

on a good day with a dry road with a good surface if i am confident i know i can stop my road bike in less than the diameter of a british 2 pence piece from upto about 20mph 
with the right tyres, right road, right conditions, good brakes and a confident and skilled rider it is surprising how quickly you can slow down/stop on a road bike
Cheers Ed


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## Spinney (24 Aug 2015)

young Ed said:


> on a good day with a dry road with a good surface if i am confident* i know i can stop my road bike in less than the diameter of a british 2 pence piece from upto about 20mph*
> with the right tyres, right road, right conditions, good brakes and a confident and skilled rider it is surprising how quickly you can slow down/stop on a road bike
> Cheers Ed


Stop in 2 cm? Is that really what you meant to say?


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## JMAG (24 Aug 2015)

Spinney said:


> Stop in 2 cm? Is that really what you meant to say?



I can do it. In fact I just did it on Saturday. Not sure how it can be done whilst staying on the bike though


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## ColinJ (24 Aug 2015)

I don't think it is a brilliant idea to support downhill records on open roads!

I have even heard of some downhill Strava segments spanning multiple sets of traffic lights and even roundabouts. I'd call those 'accidents waiting to happen' ...

Oh, like THIS ONE.

(I agree that it is the rider's responsibility to ride safely, but it might be better not to encourage competition where high speeds are not safe.)


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## Andywinds (24 Aug 2015)

I would much rather be able to be competitive climbing than going downhill, downhill seems to be more about how much your prepared to risk.


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## Milkfloat (24 Aug 2015)

Andywinds said:


> I would much rather be able to be competitive climbing than going downhill, downhill seems to be more about how much your prepared to risk.



I am a big lad, so I makes up lots of time on the descents - unfortunately I have to make it up, because I lost it on the climbs. There is a huge amount of skill in descending fast, it is not just having balls the size of melons - I would venture there is more skill in descending than then is in climbing.


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## Andywinds (24 Aug 2015)

My post came off wrong, I meant that it technique and fitness going up. Don't get me wrong, going downhill for me is easier as I am heavier than my mates and find that I'm applying brakes more often. I am just aware I'm not a sports bike with leathers.



Milkfloat said:


> I am a big lad, so I makes up lots of time on the descents - unfortunately I have to make it up, because I lost it on the climbs. There is a huge amount of skill in descending fast, it is not just having balls the size of melons - I would venture there is more skill in descending than then is in climbing.


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## Hacienda71 (24 Aug 2015)

It is just a question of being sensible. I can descend pretty well but if I don't know the descent or I feel it is dangerous I ease off. Strava is a bit of fun it isn't serious however serious some people get about it.


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## Milkfloat (24 Aug 2015)

Andywinds said:


> My post came off wrong, I meant that it technique and fitness going up. Don't get me wrong, going downhill for me is easier as I am heavier than my mates and find that I'm applying brakes more often. I am just aware I'm not a sports bike with leathers.



I am yet to have a big 'off' - so I may reassess my speed in the future  I have years of MTB behind me so feel pretty good with my bike handling, but even so, I tend to descend at more than 40mph only on the straights or where I have a great view ahead. Funnily enough, I would not trust myself on a motorbike.


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## fossyant (24 Aug 2015)

I have one downhill record but you can only really do it at weekend. It's actually not a steep hill but you can hit over 40 on it. There aren't any bends but there are a couple of junctions which care. I don't generally bother with other downhills. I also have one off road one but it's half flat and half downhill on a track.


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## Spinney (24 Aug 2015)

JMAG said:


> I can do it. In fact I just did it on Saturday. Not sure how it can be done whilst staying on the bike though
> 
> View attachment 101426


That's what I was thinking - I could do it easily with a wall, but I'm not going to try! (Hope you are OK!!)


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## JMAG (24 Aug 2015)

I'm fine thanks @Spinney, a bit banged up and sore, but fine. Why is road rash so much more painful than heavier injuries though?


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## HLaB (24 Aug 2015)

If they are short downhill segments be very sceptical of the speed, iirc one segment has me at 133mph. And there's one right opposite from me that's a short sharp bend approaching a busy roundabout where even in the ideal conditions, no traffic and strong tail wind you'd struggle to get up to 25mph where the KOM is 40mph


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## Drago (24 Aug 2015)

My Missus did some walk for life thing. She tracked the journey in Emdomondo and apparently at one point was walking at 44mph.


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## young Ed (25 Aug 2015)

Spinney said:


> Stop in 2 cm? Is that really what you meant to say?


no, i meant to say i can stop in 20mm!  i genuinely reckon at anything upto 20mph i could stop on a 2 pence although it wouldn't be normal braking and would involve the rear wheel jumping up in the air!


ColinJ said:


> I don't think it is a brilliant idea to support downhill records on open roads!


i don't ever encourage other riders to go for high speed, downhill records on a public road.... it makes it easier for me to get the KOM that way! 
Cheers Ed


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## JMAG (25 Aug 2015)

young Ed said:


> i genuinely reckon at anything upto 20mph i could stop on a 2 pence although it wouldn't be normal braking and would involve the rear wheel jumping up in the air!



I'd love to see that. Make a video and if you can stop your bike from 20mph in 20mm, I'll buy you a lollipop. 

If you're still at school, find a physics teacher and I'm sure he'll make a bet with you too


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## young Ed (25 Aug 2015)

JMAG said:


> I'd love to see that. Make a video and if you can stop your bike from 20mph in 20mm, I'll buy you a lollipop.
> 
> If you're still at school, find a physics teacher and I'm sure he'll make a bet with you too


can i exchange the lollipop for a lemon sherbet? 
just passed my physics so now i've no got a physics teacher to also make a bet with 
the video may have to wait though as the roads are wet (flooded by a few inches in places) and until i've worked out how to test my stopping distance accurately enough...
Cheers Ed


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## JMAG (25 Aug 2015)

You passed physics? You should be able to follow this then.

20mph = 32.186kmph
32.186kmph = 8.9405 m/s or 8,940.5 cm/s
To stop in 2cm, you would need to stop in 0.002237 seconds. This deceleration would be approximately 6666.7 mph/s or 303.03 g's.

No go and look what astronauts and fighter pilots can withstand


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## Spinney (25 Aug 2015)

I used to be a physics teacher* - I'll make that bet with you @young Ed

Also, assuming young Ed and his bike have a total mass of 70 kg, at 9 m/s his momentum is 630 kg m/s

I made the stopping time 0.004 s, so the braking force would be change in momentum/time, so 630/0.004 = 157 500 N (or the same as the weight of a 15 tonne mass, very roughly).

This is the kind of thing often known as a back-of-the-envelope calculation. But even if the figures are out by quite a long way, I think you may have rather over-estimated your stopping power.


*and therefore hoping I've got this right so I don't make a total arse of myself!


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## Spinney (25 Aug 2015)

JMAG said:


> I'd love to see that. Make a video and if you can stop your bike from 20mph in 20mm, I'll buy you a lollipop.
> 
> If you're still at school, find a physics teacher and I'm sure *he*'ll make a bet with you too



or she!!


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## ianrauk (25 Aug 2015)

Does Ed means he can stop from 20mph in the width of a 2p piece, or does he mean he can stop ON a 2p piece?


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## Spinney (25 Aug 2015)

The former. His first claim was ambiguous, I can see, but see this one...



young Ed said:


> no, i meant to say *i can stop in 20mm*!  i genuinely reckon at anything upto 20mph i could stop on a 2 pence although it wouldn't be normal braking and would involve the rear wheel jumping up in the air!
> 
> i don't ever encourage other riders to go for high speed, downhill records on a public road.... it makes it easier for me to get the KOM that way!
> Cheers Ed



Even I could stop ON a 2p, as long as it was sufficiently far away to allow for normal braking!!


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## ianrauk (25 Aug 2015)

Spinney said:


> The former. His first claim was ambiguous, I can see, but see this one...
> 
> 
> 
> Even I could stop ON a 2p, as long as it was sufficiently far away to allow for normal braking!!




OK.
Yup if it is the former that he means, then no way in a million years could he stop in that distance.
Ed. You are so wrong young man.


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## Sea of vapours (25 Aug 2015)

Spinney said:


> ...
> Also, assuming young Ed and his bike have a total mass of 70 kg, at 9 m/s his momentum is 630 kg m/s
> 
> I made the stopping time 0.004 s, so the braking force would be change in momentum/time, so 630/0.004 = 157 500 N (or the same as the weight of a 15 tonne mass, very roughly).


And for extra marks: assuming Young Ed has decelerated that rapidly, approximately what area. perpendicular to the original direction of motion, will what-used-to-be-Young-Ed now cover?


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## Andrew_P (25 Aug 2015)

You see I always knew there would be a use for my Physics classes, pity I never listened...


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## JMAG (25 Aug 2015)

Spinney said:


> I used to be a physics teacher



Oooh, can you calculate how fast Young Ed's buttocks will be travelling when they hit the back of his head?


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## Dan B (25 Aug 2015)

JMAG said:


> You passed physics? You should be able to follow this then.
> 
> 20mph = 32.186kmph
> 32.186kmph = 8.9405 m/s or 8,940.5 cm/s
> ...


I don't think it'll end up making that much difference, but this calculation assumes that the bike stays on the ground. If you allow the rear wheel to rise, the CoG of the bike will be able to decelerate over a substantially longer distance - until the weight is over the front axle, at which point you can't control which way it comes down. So, at a rough guess, 20mm plus (length-of-bike/3)

I'd still very much like to see it though;-)


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## Spinney (25 Aug 2015)

JMAG said:


> Oooh, can you calculate how fast Young Ed's buttocks will be travelling when they hit the back of his head?


Mind bleach time!!!


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## JMAG (25 Aug 2015)

@Dan B you may have missed my post on the 1st page of this thread, but I carried out this experiment on Saturday, albeit unintentionally. The shifting of CoG will have a minimal effect on deceleration and I can tell you the rear wheel will come down several metres past the braking point. This was with a metre or so stopping space


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## Tail End Charlie (25 Aug 2015)

Ouch @JMAG that's a nasty arrow through your knee there. 
GWS.


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## Tail End Charlie (25 Aug 2015)

I looked at strava the other day and a segment near me had the top speed as 180mph!! Or it might have been kph.


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## G3CWI (25 Aug 2015)

Tail End Charlie said:


> I looked at strava the other day and a segment near me had the top speed as 180mph!! Or it might have been kph.



Was the athlete a Mr Nibali by any chance?


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## Cannondale Lady (25 Aug 2015)

Strava must be wrong.......it gave my average speed as 9.4 mph.....no way! Never gone that fast an average yet (see my beginners thread)! Best so far was 8.4 mph. Or am I just getting better? *polishes her personal best award*


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## mcshroom (25 Aug 2015)

This is what I got when I tried to instantaneously stop from 20mph lzst year (pedal strike on fixed)





I and bike still travelled further than the with of a 2p though.


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## Cannondale Lady (25 Aug 2015)

Nasty!


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## si_c (26 Aug 2015)

I stopped on the diameter of a 2p once. Unfortunately my means of braking was the back of a car.


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## Spinney (27 Aug 2015)

I thought this might have been @young Ed until I read the link!!


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## JMAG (27 Aug 2015)

I can't wait to see Young Ed's video, although there could be a delay between filming and posting depending on whether his local hospital has WiFi.


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## Rabriguez (17 Sep 2015)

There's a segment on my commute I have gone for a few times and I it in 3rd. Current KOM has an average speed 20mph above my effort!


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## JMAG (18 Sep 2015)

20mph is a lot uphill. Maybe it was a pro or maybe they cheated? There's nothing to stop anyone jumping in a car or on a motorbike with Strava on.


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## jonny jeez (18 Sep 2015)

Andywinds said:


> I would much rather be able to be competitive climbing than going downhill, downhill seems to be more about how much your prepared to risk.


Sort of like motorsport then.


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## Mr. Cow (19 Sep 2015)

They have probably been driving with Strava running.


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## jefmcg (19 Sep 2015)

JMAG said:


> 32.186kmph = 8.9405 m/s or 8,940.5 cm/s


No one seems to have bought you to task for this. 

There's a 100cm in a metre (the clue is in the name). so it's 894cm/s, or 8,940mm/s. So (assuming your other calculations are correct) _only_ 30gs. So he probably wouldn't actually be crushed by the force, as he presumably has strong muscles and bones to apply that braking power with his hands.

Preview of video ....


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## Soltydog (19 Sep 2015)

Andywinds said:


> Hi all,
> 
> I've been looking at some of the segments on Strava and some speeds on downhill sections. I was suprised to see that on certain routes near me some were hitting over 50mph. I've gone through some of these at 40mph and thought if I miss-judged a corner I'm in trouble. Also to add a lot of these segments go through 30 zones. Surely even at 40 the stopping speed on a road bike is terrible? Plus going downhill would make stopping harder.



Back to the OP, if it's a short segment, then it's probably a GPS glitch. Last sunday I went on a club ride on my single speed, my max recorded speed for the ride was 33.6mph downhill, however on a 0.1mile segment I recorded a time of 18 seconds, 1 second of the KOM & my average speed was 37.4mph https://www.strava.com/activities/391250019/segments/9371051273 . I may not be the brightest button on the jacket, but even I realise that my average speed can not be higher than my maximum speed on a ride, however if I get a KOM I'll take it


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