Flash for cash/GOVT donation cameras

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Shann Low
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Re: Flash for cash/GOVT donation cameras

Unread post by Shann Low » August 18th, 2015, 7:13 pm

Theres a trend among 4wders to put bigger tires/rims on their vehicles.

If you increase the rolling diameter of the wheel then the speedo will read anything up to 10% (or more) UNDER what your actually doing!

So rolling thru a speed camera at say 60kph on the speedo - you COULD be doing say 65kph + and still get a fine.

If you have the GPS, you can watch and compare your actual speed to your indicated speed on the speedo.

You can even buy a programmable box to connect to your speedo sender wire to 're - calibrate' your speedo to what your actual speed is with the altered tires / rims.

If you increase the diameter of your overall wheel & tire combo by say 1 inch, then the rolling diameter increases by a factor of pi (22/7) or 3.14 inches. Circumference = pi x diameter.

So say you go from 15 inch rims to 17 inch rims... with corresponding increase in tire diameter as well (i.e. you keep the same profile of tire on the larger rim).

Just the increase in rim rolling diameter from say 15 to 17 inch...

The 15 inch rim increases from 47.14 inches to 53.42 inches!

Thats an increase of 6.28 inches... of the original 15 inch rim... so 6.28/47.14 x 100/1 = 13.32% increase in rolling diameter!

If your speedo is calibrated right at standard 15 inch rims - then 17 inch rims @ 60kps will give you a REAL speed over ground that's 113.32% of 60kph.. or 67.992 kph (call it 68kph)!

Have you got any idea, just how far out your speedo might actually be?

Sometimes those roadside VMS boards saying "slow to 40 kph for roadworks" for e.g. that are hooked to radar speed detectors, will display your real speed as you pass!

They might give you a clue maybe as to what real speed your doing, compared to what your speedo says your doing.

If you had the increase i gave as an example above and were doing say 100kph - you'd be over 110 for e.g. on freeways and open roads i.e. enough to get pinged every time!.

Just curious I guess if you have put say a hand held GPS on your dash, and compared what the speedo is telling you - to what speed your really doing?.

Maybe it's something where someone else modded the vehicle - you bought it & had no idea the speedo is that far out?

It's possible to go the other way too - smaller (wider) wheels can show a speedo reading up to 10% above what your really doing!

So all those "slow coaches hogging the right lane on the freeway doing 90kph"? They probably think they are doing the full 100 by their speedo, and no one has any legal right to speed past them, but for some reason "everyone does".

Maybe that's why they don't move left - according to their speedo, they are doing the limit (just in the right hand lane)?

When you go into you tire place and want bigger rims / tires (suspension lift) for 'better ground clearance / offroad performance' - they will TRY to steer you to the specs for your vehicle so your speedo stays within limits - BUT if it means the difference between a tire and rim sale or not - they will give you what you want to make the sale - even if it does put your speedo out - that's your lookout at the end of the day if it means you cop all the speeding fines.

If your seriously getting pinged for speeding by speed cameras, but sticking to the posted limit on your speedo then it sure SOUNDS like your speedo needs re-calibrating.

http://www.hypertech-inc.com/products-s ... rator.aspx

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foogill
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Re: Flash for cash/GOVT donation cameras

Unread post by foogill » August 18th, 2015, 7:43 pm

At a steady 110 on my GPS with 245s fitted, my speedo would show 118, with 265s fitted the speedo is within a K or so.

Talking amongst mates, that 8K margin seems the norm, regardless of brand.

Goldylux
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Location: Perth

Re: Flash for cash/GOVT donation cameras

Unread post by Goldylux » August 18th, 2015, 8:20 pm

If I drove by the speedo on the hilux I would be getting pinged daily.

Gary_M
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Re: Flash for cash/GOVT donation cameras

Unread post by Gary_M » August 18th, 2015, 8:29 pm

Its based on size so brands shouldnt be too different to each other. Theres a couple of websites you can enter in the stock size, and what you have on it, or want on it, and it will tell you the rolling diameter differences and how far out the speedo will be.

For example this one.... https://www.tacomaworld.com/tirecalc

Theres a heap of them.

Heisenberg
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Re: Flash for cash/GOVT donation cameras

Unread post by Heisenberg » August 19th, 2015, 7:48 pm

Goldylux wrote:
Without taking the matter to court you just have to cop it on the chin? How accurate
are these things? Without me having a camera with the time and date on it and a
speed calculator on my dash,how can I prove I wasn't speeding?
Easy - just tell them you drive a Hilux

Shann Low
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Re: Flash for cash/GOVT donation cameras

Unread post by Shann Low » August 19th, 2015, 8:16 pm

Easy - just tell them you drive a Hilux
Ta boom - Tish! :lol: :lol: :lol:

He makes an excellent point - I'd believe it!. ;)

Goldylux
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Re: Flash for cash/GOVT donation cameras

Unread post by Goldylux » August 20th, 2015, 5:25 pm

About two weeks ago I got pulled over for a breath test and blew over.
(morning after a big night) and Went to sit in the booze bus while we waited for
the alcohol to go down, one of the cops parked the hilux.

Apparantly when he climbed out he said "it's a long way down from here"
then when he came in the bus and said he left the window down and I said
to maybe leave it in gear because the handbrake isn't too flash.

They just smiled. The truck could have had countless yellow stickers
for various things but it's not hard too see it's sensible with mods and well maintained.

Shame the speedo is about as flash as the handbrake.

I think being a sensible driver who concentrates, with a safe vehicle with good brakes and suspension is more important than an accurate speedo.

But yeh it's still a hilux :D


Just for the record,the speeding fine I was thinking of contesting wasn't the one I got in the hilux.
It was in a clubsport with factory wheels and tyre size,usually set on cruise control on the hwy.

Heisenberg
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Re: Flash for cash/GOVT donation cameras

Unread post by Heisenberg » August 20th, 2015, 8:19 pm

Goldylux wrote: But yeh it's still a hilux :D
My 2.8D Hilux was the most gutless car I've ever owned. Wouldn't pull 100kmh into a stiff headwind. I Learnt the meaning of the phrase "always late in a 2.8"

Shann Low
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Re: Flash for cash/GOVT donation cameras

Unread post by Shann Low » August 20th, 2015, 8:30 pm

Wouldn't pull 100kmh into a stiff headwind.
Hence the old saying... "Wouldn't pull the skin off a rice pudding"! :lol:

Goldylux
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Location: Perth

Re: Flash for cash/GOVT donation cameras

Unread post by Goldylux » August 21st, 2015, 5:19 pm

Some of the old diesels where slow, but reliable.

But dreadfully slow. Slow down a steep hill with a strong tailwind.

Since I put the 3rz in,and new brakes and suspension the hilux is
the safest and most reliable car ive ever had. Sits at 100kmh with
ease and will overtake cars pretty easily. Still pulls in 5th
and you don't have to back down a gear (or two) on hills.
Turns the 33's easily, even loaded up.

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