A sneaky speeding crackdown.

[jim dalton]

These devices have been tested and use telemetry and GPS data to show what's going on. I think it would be unlikely that they would come into use for infringments tho as there will be public uproar. However, given another generation of compliant non rebellious kids, I'm sure that will change. However if you look at the current Insurance Black Box technology you will see that they already exist and the insurance company now phone up or write to you for explanations.

Later this year I believe, the trails in Birmingham, Cardiff, Swindon will start with driverless cars. That is a technology that will take off and it will be interesting to see how it will work in law (eventually). It will also be interesting to see how long it will take to transfer to PCV and HGV's if the public accept it.

Imaging just sitting there admiring the view in your campervan as you travel around Europe without having to touch the controls!!

Jim

 

[st3v3]

The sidewall will not be significantly more than the bike tyre, certainly the overall diameter of the tyre will be less than the bike one on a 17" rim.

So the speed error will be more on the mini wheel right?

Also it is obvious bikey fella is meaning a 5 mph gain on his speedo when the engine is at a set rev speed.

your displayed speed can vary by as much as 5mph simply due to the difference between a new tyre and a worn one (due of course to circumference changes - so with new boots on your speedo will read less for a given speed than when worn. These days that could possibly be enough difference to get you nicked).

Where did he mention engine revs? Not that it matters, as:

no matter what size of tyre you put on the speedometer will still register the same speed for the same rpm in the same gear.

Is completely incorrect as explained to you by David.

total bollocks!

Let's keep it civil please.

 

[GRWXJR]

Im afraid that Mr Winker is determined to robustly defend what he says regarding the basic physics of a change in diameter affecting a fixed ratio speedometer gearing system.

This is despite the fact that (as others have tried to point out) he is making a total hash of it and his statements are entirely incorrect.

This 'bikey fella' can prove this both theoretically and factually should he like to try to learn and understand the basic principles.

Example 1. Put a fixed gear speedometer onto the rear wheel of a penny farthing, then ride until you indicate 30mph. Then switch the drive to the front wheel, and see if you achieve the same speedo reading without having to pedal and travel a LOT faster.

Actually, if the example above doesnt make the penny drop, then I'm not sure if anything will get through.

This is a case where the phrase " making the most noise doesn't make you right" should be rolled out.

 

[jamesmarshall]

Quite right David, thankyou.

 

[GRWXJR]

A tachograph is only really a verg well calibrated sppedo thats checked and set n on the actual vehicle in question.

Make s significant change in tyre diameter and it will be incorrect in the same manner.

Smaller wheel = over read
Bigger wheel = under read

 

[Winker]

The difference in speed / rpms? It was a while ago when I did the last back to back old tyre v new tyre and paid it much attention, but itd have been at a typical cruising speed of between a bit naughty and less than instant ban on a motorway.

The really noticeable effect is when you stay at a constant throttle and speed and go from a straight to a big lean through a corner and back upright. As of course the diameter on the edge of the tyre is far less than on the crown, you can distinctly hear the revs rise and fall significantly at the same speed. 125cc racers used to exploit this effective lower gearing phenomena by momentarily flicking the bike on its side when accelerating up the gears on a straight to assist acceleration with limited hp.

I admit I havent looked at the speedo to note the indicated speed variance - its generally a good idea to look where youre headed when doing this!

And THAT is my point exactly!!!

There will be no indicated speed variance, therefore the accusation of your post being senationalist nonsense!!!
You would only see a difference on a gps unit, not a speedometer, and a 5 mph gain with an extra 12mm on the diameter of a tyre the size you quoted would not happen at any remotely sensible road speeds. The maths can be done, try it.

 

[Siimplyloco]

I don't think it should be forgotten that the primary purpose of the tachograph is to record the driver's hours spent at the wheel, thus providing evidence that statutory breaks have been taken. Given that the vehicles are governed, nicking for speeding might be a secondary issue.
John

 

[Winker]

Well I get about a 5mph difference for a given rpms in top gear when I fit a new rear tyre on my motorcycle ( the speedo reads off the gearbox, and it runs 17" rear wheel with a 180/55 section tyre. Drive is via a crownwheel and shaft drive, much in the same manner as a rear wheel drive car might). Tread depth is 7mm when new.

But then maybe Im just making it up to sensationalise.

Giving you a generous allowance here by stepping up a size rather than a wear allowance on a tyre, you would be going 2.8 mph faster at 100mph withe the tyre, check for yourself bikey boy and stiff.

P.s. the tyre diameters are different by 18mm, and the tyre wear on bikeys tyre would account for only 14mm IF going from totally bald to new.


Tire Size Finder (optional):
56 motorcycle tires available in 180/55-17 @ BikeBandit.com
Understanding metric sizes
Current Tire Size: 180/55 R 17
New Tire Size:180 /60 R 17
Your Calcs (x):


Speedometer Difference
Speedo Reading Actual Speed
20 mph (32.19 km/h) 19.44 mph (31.29 km/h)
25 mph (40.23 km/h) 24.31 mph (39.12 km/h)
30 mph (48.28 km/h) 29.17 mph (46.94 km/h)
35 mph (56.33 km/h) 34.03 mph (54.76 km/h)
40 mph (64.37 km/h) 38.89 mph (62.59 km/h)
45 mph (72.42 km/h) 43.75 mph (70.41 km/h)
50 mph (80.47 km/h) 48.61 mph (78.23 km/h)
55 mph (88.51 km/h) 53.47 mph (86.05 km/h)
60 mph (96.56 km/h) 58.33 mph (93.88 km/h)
65 mph (104.61 km/h) 63.19 mph (101.7 km/h)


Over to you st3v3.

 

[Siimplyloco]

Excuse me for asking an innocent question, but why all the fuss over a small difference in speed reporting? Life's too short to worry about it, especially when driving a 4.5 tonne motorhome at leisure!
John

 

[GRWXJR]

Fair play, youve gone to one hell of an effort to win a point !

I do note though that you have at least now decided that a change in diameter does alter speedo reading.

Im far too lazy to check your stats, so I'll take your word for it on the numbers :banana:

 

[st3v3]

Good, some actual maths.



Which backs up everything I've posted. Please go ahead and quote anything I've posted that isn't factually correct.

And still you demonstrate a lack of understanding:

There will be no indicated speed variance, .... You would only see a difference on a gps unit, not a speedometer,

The speedometer drive isn't taken from the gearbox.

 

[Winker]

Well I get about a 5mph difference for a given rpms in top gear when I fit a new rear tyre on my motorcycle ( the speedo reads off the gearbox, and it runs 17" rear wheel with a 180/55 section tyre. Drive is via a crownwheel and shaft drive, much in the same manner as a rear wheel drive car might). Tread depth is 7mm when new.

But then maybe Im just making it up to sensationalise.

Good, some actual maths.



Which backs up everything I've posted. Please go ahead and quote anything I've posted that isn't factually correct.

And still you demonstrate a lack of understanding:



The speedometer drive isn't taken from the gearbox.

It is, not that it makes any difference smart lad. Anychange in tyre size will require recalibration if the speedo is to remain accurate.
Given that gps units are not acceptable in law at the moment.

Next?

Edit for st3v3, quote from Gixxer he has conveniently overlooked???? (the speedo reads off the gearbox, and it runs 17" rear wheel with a 180/55 section tyre.)

 

[Winker]

Fair play, youve gone to one hell of an effort to win a point !

I do note though that you have at least now decided that a change in diameter does alter speedo reading.

Im far too lazy to check your stats, so I'll take your word for it on the numbers :banana:

Read my post way back, I quoted a 1mph gain at 56mph on a truck, same for same, new tread, and the site I quoted from backs that up too. Reason for taking so long is that my posts have to go through mods, free member an that.

It's always worth listening to pro's before getting in disputes with them Gixxer.

 

[st3v3]

It is, not that it makes any difference smart lad. Anychange in tyre size will require recalibration if the speedo is to remain accurate.
Given that gps units are not acceptable in law at the moment.

Next? L

I'm sorry, I don't understand what you're trying to say.

 

[Winker]

I'm sorry, I don't understand what you're trying to say.

I have noticed.

It's a recurring problem you seem to have, but ztick with it, the light may yet get turned on stiffy babe.

Damned pur dick tiv txt, grrrrrrr.

 

[Winker]

Excuse me for asking an innocent question, but why all the fuss over a small difference in speed reporting? Life's too short to worry about it, especially when driving a 4.5 tonne motorhome at leisure!
John

But obviously not too short for you to comment though.

 

[delicagirl]

Giving you a generous allowance here by stepping up a size rather than a wear allowance on a tyre, you would be going 2.8 mph faster at 100mph withe the tyre, check for yourself bikey boy and stiff.

P.s. the tyre diameters are different by 18mm, and the tyre wear on bikeys tyre would account for only 14mm IF going from totally bald to new.


Tire Size Finder (optional):
56 motorcycle tires available in 180/55-17 @ BikeBandit.com
Understanding metric sizes
Current Tire Size: 180/55 R 17
New Tire Size:180 /60 R 17
Your Calcs (x):


Speedometer Difference
Speedo Reading Actual Speed
20 mph (32.19 km/h) 19.44 mph (31.29 km/h)
25 mph (40.23 km/h) 24.31 mph (39.12 km/h)
30 mph (48.28 km/h) 29.17 mph (46.94 km/h)
35 mph (56.33 km/h) 34.03 mph (54.76 km/h)
40 mph (64.37 km/h) 38.89 mph (62.59 km/h)
45 mph (72.42 km/h) 43.75 mph (70.41 km/h)
50 mph (80.47 km/h) 48.61 mph (78.23 km/h)
55 mph (88.51 km/h) 53.47 mph (86.05 km/h)
60 mph (96.56 km/h) 58.33 mph (93.88 km/h)
65 mph (104.61 km/h) 63.19 mph (101.7 km/h)


Over to you st3v3.

this has to be one of the most boring pointless threads on here... ... can't you guys just agreed to differ and go to bed ???? please

 

[Siimplyloco]

But obviously not too short for you to comment though.

Well, I found just enough time to make my protest!:scooter:
John

 

[Winker]

5 mph!!! I really don't thin so. On a lgv drive axle a new same for same tyre will give you +1mph max at 56 so a relatively small car tyre with a ar shallower tread….. 5MPH!!! NEVER. Scaremongering raising it's head I fear.

Fair play, youve gone to one hell of an effort to win a point !

I do note though that you have at least now decided that a change in diameter does alter speedo reading.

Im far too lazy to check your stats, so I'll take your word for it on the numbers :banana:

N.b., I always have said tyre size is a consideration, the dispute was to what extent it mattered, you would have to be doing around 200mph for the 5mph gain you claimed, and you 2 dears ^^^ feel free to knock off any time you like. X

 

[st3v3]

I have noticed.

It's a recurring problem you seem to have, but ztick with it, the light may yet get turned on stiffy babe.

Damned pur dick tiv txt, grrrrrrr.

See, this is the problem with you. I've asked perfectly politely for you to elaborate on something you've posted, but instead of doing so you've tried (very poorly) for a cheap shot.

Probably because you've realised it won't end well if you do I suppose.

N.b., I always have said tyre size is a consideration,

Quite the opposite. I've been saying that. Here:

.......truck tyres are massive, so the tread is a small percentage of the diameter. On a small car/bike tyre the percentage is much different, so the error on speed will be higher.

you replied with:

Circumference
Read and learn, then go remove the egg from your face.