# 40 mph my ass



## Merida (28 Oct 2011)

I was casually cycling home from the shops the other day on my road bike, I had a hoodie trackie bums and a messenger bag full of booze and rice on. A renault clio approached me from behind and the passenger wound down the window and shouted at me over the wind 'mate you now your doing 40 mph right?', now bearing in mind I was on a 3% hill going down and it was wet and I wasnt pushing particularily hard and I wasnt wearing aero clothes I found what he said very hard to believe, however upon glancing through the window the speedo in the car was registering about 37-8 mph. I thanked the occupants of the clio and then raced ahead of them to get through the level crossing in time. I am still at a loss to understand how this is possible, unless the french make very innaccurate speedos which is entirely possible given the state of their cars.

At the end of the day Im just happy that not all drivers are mindless prats, and I was impressed with the respect that they gave me


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## HLaB (28 Oct 2011)

That was some tail wind  IIRC, I think car speedos are allowed to read over not under, they can make the driver seem faster than they actually are but not slower.


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## oldfatfool (28 Oct 2011)

swmbo's Citroen overreads by about 10% you would still have been doing 35 ish though


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## JonnyBlade (28 Oct 2011)

3%, downhill, natural body weight, laden with goodies, wet ......................... seems tome like a recipe for a quick decent


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## screenman (29 Oct 2011)

Sorry mate but you are a total muppet, if you were close enough to look inside the car and see the speedo whilst doing that speed you should be banned from the road. 

Internet speed alert.

Apologies if the joke has gone right over my head.


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## Tyke (29 Oct 2011)

MPH or KPH, 40 kph is about 25 mph and a car can be up to 10% out and still be legal.

Agreed you should not be able to read a speedo from the near side at that speed without being a danger to yourself and others.


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## Moodyman (29 Oct 2011)

I think HLAB has it bang on. Car speedos are deliberately designed to read more than actual. Something to do with building in a safety margin with speed cameras, driver error etc.


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## Merida (30 Oct 2011)

screenman said:


> Sorry mate but you are a total muppet, if you were close enough to look inside the car and see the speedo whilst doing that speed you should be banned from the road.
> 
> Internet speed alert.
> 
> Apologies if the joke has gone right over my head.


Truly I dont believe I was doing that speed at all, and as for passing close to the car window the driver didnt give me much choice! I dont think he understood that a pothole could send me flying, fortunatley I know the road very well and it has an excellent surface. I was entirely expecting him to whizz past me like most drivers do but he just hoverred alongside me and decided to have a chat.


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## col (30 Oct 2011)

Cars have 3 mph difference to true speed, check it on a sat nav, you will see. So travelling at 33 is really 30. And I doubt you were doing 40, as I was pushing as hard as I can down a local steep hill and only reached 40, you sure the numbers you saw werent KPH? Some cars show those numbers more than MPH.


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## screenman (30 Oct 2011)

I still struggle to see how you managed to read the speedo without actualy leaning inside the car, on the Clio the speedo is set well back behind the steering wheel.


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## sheddy (30 Oct 2011)

A LH drive car ?


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## cycleruk (31 Oct 2011)

40 mph on a pushbike, what ever you are on, can i have some please


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## addictfreak (31 Oct 2011)

col said:


> Cars have 3 mph difference to true speed, check it on a sat nav, you will see. So travelling at 33 is really 30. And I doubt you were doing 40, as I was pushing as hard as I can down a local steep hill and only reached 40, you sure the numbers you saw werent KPH? Some cars show those numbers more than MPH.



While I have a few doubts about this tale. It is certainly possible to achieve 40+mph downhill. I have done 50+ coming down from Kilhope Cross in the Pennines, and I wasn't the fastest in the group.


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## BrumJim (8 Nov 2011)

Which Clio? I find most renault speedos easy to read from the car alongside. These are the digital ones.


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## Muddyfox (8 Nov 2011)

col said:


> Cars have 3 mph difference to true speed, check it on a sat nav, you will see.



This will vary from vehicle to vehicle .. we have 10 cars in our fleet and even the same model vehicles will vary anywhere between 3mph and 5 mph


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## lukesdad (8 Nov 2011)

Muddyfox said:


> This will vary from vehicle to vehicle .. we have 10 cars in our fleet and even the same model vehicles will vary anywhere between 3mph and 5 mph




Thank you vice admiral


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## VamP (9 Nov 2011)

sheddy said:


> A LH drive car ?




Hmm, with speedo in kilometers per hour. And a bunch of jokers trying to see how gullible cyclists are. Perhaps.

At least they didn't shout abuse or cut OP up, which is as far as a lot of joker's in cars imaginations stretch.


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## Muddyfox (9 Nov 2011)

lukesdad said:


> Thank you vice admiral



If this rain keeps up LD .. i'l be breaking the submarines out of dry dock


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## Radman (10 Nov 2011)

Honestly i think you would know if you were doing 40 mph


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## ColinJ (10 Nov 2011)

Radman said:


> Honestly i think you would know if you were doing 40 mph


Er, I hit 54 mph freewheeling down this hill a few months back but didn't realise until I checked my GPS when I got home! I'd have guessed about 45 mph. (Photograph obviously taken mid-winter) ...


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## adscrim (10 Nov 2011)

ColinJ said:


> Er, I hit 54 mph freewheeling down this hill a few months back but didn't realise until I checked my GPS when I got home! I'd have guessed about 45 mph. (Photograph obviously taken mid-winter) ...




Maybe your GPS was wrong. Mine has had me at 60mph before.


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## fossyant (10 Nov 2011)

Cars are out, and chav cars are worse as they just fit wheels without realising the speed impact (although that will make them under read for big wheels) you go from say 205 16 R55 then if you get 215 17 R45 then that might be the same - you have to drop the tyre profile if the rims get bigger.

I've had chav's shout - wow nearly 30, and I was doing less than 25. 

I've taken my 705 in the car to a sky ride and my son said the GPS speed compared to the car, and the car was at least 3 mph higher than real at motorway speeds.

Just smile if a chav shouts. A car is their aim from a rubbish BMX.


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## ColinJ (10 Nov 2011)

adscrim said:


> Maybe your GPS was wrong. Mine has had me at 60mph before.


Maybe you _were_ doing 60?

I'm pretty sure that my GPS was telling the truth. I span out at 40 mph before even getting into an aero tuck.

I might be doing that descent again on Sunday. If the wind isn't against me, I'll check how fast I go by timing myself between two points when I'm at my terminal velocity.


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## Cubist (10 Nov 2011)

The main hill out of my village sees me hit 45 regularly. I've done 47mph on my mountain bike down Ripponden Bank. honestly, you flatlanders haven't got a clue when it comes to hills


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## HLaB (10 Nov 2011)

I guess I'm not pedalling hard enough, the fastest my gps has recorded is 44.4mph (well it recorded 266.6mph once but I think that was interference  ) and I've only been slightly faster when I never had the aero drag of the unit  , 47.6mph.


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## Tigerbiten (11 Nov 2011)

My local steep hill is only a drop of 150' at around 8%
I easily spin out at around 44 mph down it.

I've found to hit +50 mph takes a hill twice as steep ........


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## Mugshot (11 Nov 2011)

adscrim said:


> Maybe your GPS was wrong. Mine has had me at 60mph before.



The best my GPS has shown me was 63mph, I was even more impressed when I noticed that I'd hit top speed in the middle of the Irish Sea! Wondered why my feet were wet.


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## byegad (11 Nov 2011)

My Auris reads over by about 3mph right across the board. My Satt' Nav' gives a reading of my speed so that's how I know.


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## ColinJ (11 Nov 2011)

Tigerbiten said:


> My local steep hill is only a drop of 150' at around 8% I easily spin out at around 44 mph down it.
> 
> I've found to hit +50 mph takes a hill twice as steep ........


Would that be sitting upright on your bike or getting down into a decent aerodynamic position?

On an 8% descent, I could probably reach 60 mph if it was long and straight enough so I didn't have to brake. Mind you, I weigh 15 st 7 lbs so there is a lot of weight dragging me down hills.


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## Banjo (11 Nov 2011)

1595873 said:


> Have we considered parallax?



If it was a dial type speedo with a pointer set on a card Parralax error could well account for 5 mph or more looking at such an extreme angle. Add that to 2 or 3 mph speedo over reading then it becomes more likely.

Even still at anything over 20 I dont think I would be focussing my attention on a car speedo friendly occupants or not. 

Its amazing what a difference nice smooth tarmac makes. A lot of roads near me have been resurfaced and its a magical ride in places (terrible in others).


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## threebikesmcginty (11 Nov 2011)

1595873 said:


> Have we considered parallax?



Very effective - I found it got things moving again.


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## Cubist (11 Nov 2011)

Oh, I get it now! Crap. Sorry.


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## Alembicbassman (12 Nov 2011)

Kev'd up car wrong tyres /wheels = wrong speedo reading.


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## screenman (12 Nov 2011)

I still cannot understand how close someone must be to be able to see the speed, with my cars you would have to press your nose up against the glass.


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## oldroadman (15 Nov 2011)

Back when God was a boy and I was a junior (no gear restriction in those days, but a 13 was the smallest sprocket available), riding in a road race north of London. We were descending Digswell Hill on the old A1, going south towards Welwyn GC. The peloton was flat oot chasing asolo break down with about 10km to go. The whole lot of us passed a very surprised bloke and his girlfriend on a small moto, as we went by quite a few noticed his speedo hovering around 55/60, us about 5 mph quicker. Just about terminal speed on a long, wide, main road descent - plus a tailwind. The comisaires confirmed their speedos all showing between 65/70, which when you take out the error is just over 60. A quick day, and I can clearly remember getting in the first 5 or so, but no win!


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## BADGER.BRAD (5 Dec 2011)

Probably had different wheels on the Clio if it was a chav car and that buggers up the speedo readings


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## Ethan (6 Jan 2012)

BADGER.BRAD said:


> Probably had different wheels on the Clio if it was a chav car and that buggers up the speedo readings


 
old thread but I still think its worth a mention.
My friend had a clio that would tell us we were doing 30mph when we had to be doing atleast 60, it was 100% stock for a few weeks until it was sorted.
Its a common problem with the older clios, and obviously if it was a chavwagon its probably had its wheels messed with! So maybe the driver had a similar issue, just not as extreme as my friend had  


I second or third or whatever the idea of 40 upwards being fairly easy to do! I've had 37mph (gps and computer) on a steep, but poorly surfaced road on a mountain bike!
On a road bike, 40 mph is easypeasy!


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## screenman (7 Jan 2012)

Regardless of the speed, how did the rider see the speedo and spend enough time focused on it to read it.


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## smutchin (7 Jan 2012)

screenman said:


> Regardless of the speed, how did the rider see the speedo and spend enough time focused on it to read it.



Aye, that's the bit that doesn't ring true. 

40mph isn't difficult to achieve on a road bike on a long/steep hill but I'd have my eyes fixed firmly on the road ahead at that speed. 

d.


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## Archie_tect (7 Jan 2012)

This is "Rider's Tales" after all...


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## Paul_T (7 Jan 2012)

Hmmm..yes I agree with above comments, I think actually riding at 40mph you would (or should) be so focused on the road in front I don't see how you would be able to "glance" anywhere, let alone looking at a car speedo driving alongside you. I don't see how you managed that speed too under them conditions, I have only ever managed 47, and that was hard flat out on a decent roadie, going down an extreme steep hill, which I must point out here that once you go above the 30 mph mark on a bike, I think you're in very dangerous territory. A collision/crash at this speed doesn't bare thinking about, so I only done it once (just to see how fast etc..as you do ) and wouldn't normally condone riding at this speed.


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## GrasB (7 Jan 2012)

col said:


> Cars have 3 mph difference to true speed, check it on a sat nav, you will see. So travelling at 33 is really 30.


Not even close. Speedos are all over the place. Some random experiences from rolling road runs:

+5mph at 10mph, +3mph at 40mph, accurate at 110mph, -2mph at 150mph
+2mph at 15mph, +5mph at 25mph, +8mph at 70mph, +3mph at 100mph, +1mph at 123mph
+20% at 5km/h liner taper down to to +2% at 140km/h up to 285km/h
-6% at 2mph, accurate at 13mph, +2.5% from 20mph up (aftermarket digital instrument pannel inaccuracies at low speed were cause by vibrations killing off sensor readings)


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## dellzeqq (7 Jan 2012)

screenman said:


> Sorry mate but you are a total muppet, if you were close enough to look inside the car and see the speedo whilst doing that speed you should be banned from the road.
> 
> Internet speed alert.
> 
> Apologies if the joke has gone right over my head.


never ridden with a road group?


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## Holy Warrior (7 Jan 2012)

I spin out at 45 mph and I only weigh 60kgs. A couple of hundred yards at ~8/10% is all it takes. Really can't see the problem here, or is it just a big gag?


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## screenman (7 Jan 2012)

dellzeqq, I have done many group rides, more than likely thousands in the past 40 years, why do you ask?


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## dellzeqq (8 Jan 2012)

because suggesting that somebody should be banned from the road for riding close to a car sounds a tad silly


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## screenman (8 Jan 2012)

Riding close enough to a car at 40 mph and leaning in to see the speedo, and the time taken to do so was my problem with the guy. I have been out today and been close to a lot of cars, not through choice I must add, guess what I did not see one speedo.

Try this walk down the street or past your own car if you have one and glance in quick to see if you can spot and read the speedo.


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## dellzeqq (8 Jan 2012)

if you're riding close beside a car you can usually see the instruments - I don't see the problem. And it wasn't 40mph. And he glanced in - as opposed to leaning. Toughen up, there!


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## col (8 Jan 2012)

GrasB said:


> Not even close. Speedos are all over the place. Some random experiences from rolling road runs:
> 
> +5mph at 10mph, +3mph at 40mph, accurate at 110mph, -2mph at 150mph
> +2mph at 15mph, +5mph at 25mph, +8mph at 70mph, +3mph at 100mph, +1mph at 123mph
> ...


 
Looks pretty close there? 3mph at 40, 5 mph at 25, what was +2.5 % at 20 mph? the speed showing on the cars speedo is generally more than true speed. If its out badly, I hope you give your customers a printout to save them speeding tickets. Checked mine and it does what I said, your examples must have wrong wheels or tyres or faulty speedos.?


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## screenman (9 Jan 2012)

dellzeqq, you are so wrong on this one, I have just gone outside and stood beside all 3 of our cars and cannot see the speedo easily. Most are set back into the dashboard and would need almost a straight on look to see.

The reason why I did this is because I like to know what I write is correct.


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## screenman (9 Jan 2012)

No but after 40 years in the motor trade I have a rough idea of where mot speedo's are. I will check out a Clio today as I am working at a Renault franchise later.


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## screenman (9 Jan 2012)

Can I not just bend down a bit, hold on what sort of bike was he riding? was it night or day? Damn I must get this right.


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## dellzeqq (9 Jan 2012)

screenman said:


> dellzeqq, you are so wrong on this one, I have just gone outside and stood beside all 3 of our cars and cannot see the speedo easily. Most are set back into the dashboard and would need almost a straight on look to see.
> 
> The reason why I did this is because I like to know what I write is correct.


do you, perhaps, have some physical impairment? And could we have a complete list of cyclists that you want to see 'banned from the road'


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## screenman (9 Jan 2012)

No physical impairment here, does anybody on this forum recommend or even can ride a bike at 40 mph whilst looking intently into a car interior.


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## screenman (9 Jan 2012)

Stood beside a Clio today and all I can say is let us advice others not to try, I could not see the speedo clearly enough to rad without putting my head in the window.

As a responsible forum I feel we should be passing out good, honest and safe advice.


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## Friz (9 Jan 2012)

-chuckles-

Man you lads'll argue about anything...


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## Globalti (9 Jan 2012)

Zzzzzzzzz....


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## screenman (9 Jan 2012)

Not arguing, just trying to improve my typing skills. It is a laugh, well I think so anyway.


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## GrasB (12 Jan 2012)

col said:


> Looks pretty close there? 3mph at 40, 5 mph at 25, what was +2.5 % at 20 mph? the speed showing on the cars speedo is generally more than true speed. If its out badly, I hope you give your customers a printout to save them speeding tickets. Checked mine and it does what I said, your examples must have wrong wheels or tyres or faulty speedos.?


The top 3 cars were with stock tyres, though the one on km/h was tweaked to not read +7km/h all the time (eg. even when stationary). Which gives us an accuracy range of -2mph to +8mph, a fair bit different to 'close to +3mph'.


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## screenman (12 Jan 2012)

I agree 40mph not mad fast, but it is with your head stuck in a cars side window.


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## col (12 Jan 2012)

GrasB said:


> The top 3 cars were with stock tyres, though the one on km/h was tweaked to not read +7km/h all the time (eg. even when stationary). Which gives us an accuracy range of -2mph to +8mph, a fair bit different to 'close to +3mph'.


 Yeah but not no where near


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## Moss (22 Jan 2012)

What are you lot talking about? 40mph is not only achievable but surpassable by quite a way! In a bunch decent on the Brecon Beacons (many years ago) being followed by a car who's driver stopped at the same cafe as our small group, made a point in telling us we were doing 68mph at one point on the decent: I believe speed of 35 mph are achievable on a flat road.


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## ColinJ (22 Jan 2012)

Moss said:


> I believe speed of 35 mph are achievable on a flat road.


_And the rest ...  _

I was once on a training camp on the Costa Blanca and we regularly used to sprint to a road sign on the NE side of Altea. (After that, we'd get into the narrow streets of the town and have to ride slowly in traffic.) 

There was an uphill drag to the sign and I was really going for it with a young guy on my wheel and his girlfriend on his. I sustained 30 mph most of the way up the drag, but my legs started to turn to jelly with 50 yards to go. I was doing about 27 mph when the young guy pulled out and shot past me doing about 35 mph, and his girlfriend got past me just before the sign and she was probably doing about 33 mph at that point.

I certainly wasn't superfit. If I could do 30 mph for a minute or so (slightly) uphill then the Cavs of this world can probably hit close to 50 mph in a level sprint! As for a more sustained effort - Bradley Wiggins did a 10 mile time trial in 17:58 which is an average speed of 33.4 mph!

35 mph is _definitely_ achievable on a flat road!


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## screenman (22 Jan 2012)

We were not debating the speed which is certainly attainable, but I for one was saying he should not have been looking inside a car and reading the speedo whilst doing so. At 40 mph I would say there are safer things to look at, which is why I called the OP a muppet, in the nicest possible way.


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