A sneaky speeding crackdown.

[ricc]

back in the dim mists of time i had a mk2 escort 1.1 litre estate car, it had drum brakes on the front.

no problem a pair of front struts from a 1.3 saloon in the scrap yard will give me disc brakes.

the 11 inch wheels wouldnt fit over the calipers

another trip to the scrap yard ....for a set of `13 inch wheels.....


gearings a bit high , wont go up hills

another visit to the scrap yard

1.6 litre capri gt engine

went like sh one t of a shovel

speedo was a bit off ... had to follow a mate at 30, 50, and 70 and stick a dot on the speedo at the critical speeds.

overall it was a change from 155 11 inch tyres to 175 13 inch tyres.

 

[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.

post #58

What W anker has failed to realise is that 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.

post #77

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.



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



you replied with:

And who said tyres have a part in the calculation first??

 

[piman]

Hello GRWXJR,

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

I agree with Mr Winkler's original statement that overall tyre diameter does not affect the speedometer reading, how can it as all the speedometer is reading are the output revolutions of the drive. It matters not if larger or smaller diameter wheels are fitted, the speedometer will read the same for the same output rpm. You will note, on older cars, a revolutions per mile number etched on the dial. On the same model car but with different final drive ratios, e.g. manual or automatic transmissions required a different tpm speedometer to maintain accuracy which is no different than using a varying diameter drive wheel.

Alec

 

[izwozral]

I am getting TYRED of this TREAD.:lol-053:

 

[GRWXJR]

Hello GRWXJR,

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

I agree with Mr Winkler's original statement that overall tyre diameter does not affect the speedometer reading, how can it as all the speedometer is reading are the output revolutions of the drive. It matters not if larger or smaller diameter wheels are fitted, the speedometer will read the same for the same output rpm. You will note, on older cars, a revolutions per mile number etched on the dial. On the same model car but with different final drive ratios, e.g. manual or automatic transmissions required a different tpm speedometer to maintain accuracy which is no different than using a varying diameter drive wheel.

Alec

Ok, have it your way - its not that important. The actual variance isn't enough for anyone to have worried about it overmuch, as a speedo has always just been an indication of speed with a +/- 10% degree of accuracy. I mere;ey made the point that, as we are now being measured and prosecuted with exactitude, using sophisticated means, that to rely on a speedo reading as being 'close enough' potentially isn't reliable enough (though the vast majority under-read).

You are actually incorrect though about it not changing the reading - its basic gearing/maths - it HAS to. If you read distance & speed based on the rolling circumference of a circle, then that reading HAS to vary when you alter the circumference (unless you also alter the gearing to compensate - which the instruments do not do).

The truth is, is that cars are fitted with generic instruments with a permissable degree of (in)accuracy that now exceeds and is 'slacker' than the exacting measurements and methods used by the Scamera's to punish you if you stray from a limit.

I'm sorry, but the change of tyre diameter affecting a speedometer reading isn't open for debate - it is a fact.

However, believe differently if you wish :idea-007::rulez:

 

[st3v3]

EDIT: apologies Alec, GRWXJR has posted that on his bike, you're correct.

Alec, we're talking a motorbike which as per David's post some time further up, takes the speedo drive from the front wheel.

 

[GRWXJR]

Alec, we're talking a motorbike which as per David's post some time further up, takes the speedo drive from the front wheel.

Actually, while they USED to almost exclusively, most motorcycles in recent decade + now read from the gearbox, or from the gearbox output shaft with a sensor instead of a cable. But they still read off the rotation of the (rear) wheel indirectly through the transmission to get the information to translate as a speed reading.

My bike is an '04 and reads off the gearbox.

 

[Winker]

Alec, we're talking a motorbike which as per David's post some time further up, takes the speedo drive from the front wheel.

We are NOT!!

Pay attention man, Gixxer's bike has it's speedo drive from the transmission, i.e. directly linked to the REAR WHEEL!

 

[st3v3]

You might have mentioned that earlier lol.

 

[st3v3]

We are NOT!!

Pay attention man, Gixxer's bike has it's speedo drive from the transmission, i.e. directly linked to the REAR WHEEL!

I had posted that I'd seen his reply, before yours appeared. And you'll notice he only told us that after my reply to Alec.

 

[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.

Post#76

What W anker has failed to realise is that 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.

Post#77. You acknowledge that you have seen the speedo drive does NOT come from the front wheel.

EDIT: apologies Alec, GRWXJR has posted that on his bike, you're correct.

Alec, we're talking a motorbike which as per David's post some time further up, takes the speedo drive from the front wheel.

We are NOT!!

Sneaky but futile bit of editing, lol.

Pay attention man, Gixxer's bike has it's speedo drive from the transmission, i.e. directly linked to the REAR WHEEL!

I had posted that I'd seen his reply, before yours appeared. And you'll notice he only told us that after my reply to Alec.

HORLICKS. You have been well caught out, piece of advice son, when in a deep hole chuck your bl00dy shovel away!

 

[st3v3]

Post#77. You acknowledge that you have seen the speedo drive does NOT come from the front wheel.

No, I actually didn't take any notice - hence why I carried on assuming it wasn't. My reply was about your lack of understanding that the error will be bigger on a small wheel.

Sneaky but futile bit of editing, lol.

How is it sneaky? I've clearly identified it as an edit, you can see at what time I've edited (i.e. after GRWXJR pointed it out) and I've left the original post in tact. I wanted to be clear to Alec that he was correct. (See how I can admit when I'm wrong? You might want to try that ) What's your point?

 

[Fazerloz]

Watch this to see the relationship between tyre diameter, engine rpm, and speed . Well worth a watch in its own rights. https://www.youtube.com/watch?v=-VF0JwxQqcA

 

[pheasantplucker]

A few years ago I joined Drive Protect, run by Adam Blair, after having been caught speeding three times is as many weeks.
No problems with that, but I needed to cover myself against another one.
Thank goodness it hasn't happened, and the info from them has been a help.

They do send me regular updates, and their latest one may be of interest to a few of us.
As it may be what's on the cards to come, (To raise more cash???).
So have a look below, and see what you think.
Rgd's Graham.

Hi GRAHAM,

A sneaky speeding crackdown
is set to catch motorists out on
the M42 and M6 in Coventry
and Warwickshire.

Drivers could soon be booked
for going just over the 70 mph
limit.

The threat comes from "stealth
cameras" which were introduced to
enforce variable speed limits on
“Smart Motorways”.

However it has now been
disclosed that these cameras may
be used to strictly enforce the
70,mph speed limit during non
variable limit hours.

The West Midlands has two sections
of Smart Motorways; the M42, to the
West and the M6, to the North of
Coventry.

Also sometimes called “Managed
Motorways”, the hard shoulder is
opened as an extra lane to ease
congestion at peak hours.

Overhead gantries display variable
speed limits, supposedly to keep
the traffic flowing as efficiently
as possible.

Up until now the cameras have
been switched off at quieter times,
when no variable speed limits are
in force.

But that's all set to change...

This misuse of these types of
cameras has already happened
before, in Kent…

The first victims of the “stealth
cameras” (also called Hadecs3)
were on a section of the M25.

668 motorists were caught in the
first three months after they were
switched on.

Of those, 520 drivers and riders
received tickets where the limit
was set at exactly 70mph.

Now this totalitarian crackdown is
set to be rolled out in the near
future on the M42 and M6...

So much for the Freedom Bill that
was introduced by the Government
in 2012!

If you’re driving in these areas any
time soon, watch out.

All the best,

Adam

How do they do that? Most police forces allow the speed limit + 10% or even the limit +2mph +10%. All speedos should read high or +zero mph, which is the case when comparing the dial with the satnav reading.

Might better to go by satnav rather than vehicle speedo.

 

[Winker]

No, I actually didn't take any notice - hence why I carried on assuming it wasn't. My reply was about your lack of understanding that the error will be bigger on a small wheel.

That is your problem, you spout off without paying heed to previous posts.
Best you keep quiet now, that hole is still getting deeper sonny.

If anyone is remotely interested I can explain how tachographs are calibrated and how to present a vehicle for calibration if you want an extra few mph on your speed limiter.
The thing is I have been present many times when this has been done, have you st3v3y boy?

 

[st3v3]

And again you haven't answered a direct question. A bit of a theme for you...

The thing is I have been present many times when this has been done, have you st3v3y boy?

Well done you. No, I haven't done it. It's not really rocket science is it? I've calibrated other things - You put a known stimulus in, and look for the expected result. If you don't get the result you adjust.

I'm going to ask you one last question. I posted:

What W anker has failed to realise is that 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:

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

What exactly did you mean by that?

 

[Winker]

That's a NO then.

 

[Admin]

The tone of this thread is not very nice. Stop it now please and play nicely.

 

[st3v3]

That's a NO then.

I didn't think you'd want to answer that. Is your shovel broken?

The tone of this thread is not very nice. Stop it now please and play nicely.

Ok, I won't reply again.

 

[izwozral]

Hurray, at last. The children have been spanked & sent to bed. Good on you Admin.