Go Back   The 75 and ZT Owners Club Forums > The 75 and ZT Owners Club Forums > The 75 and ZT Owners Club General Forum
Register FAQ Image Gallery Members List Calendar Mark Forums Read
Notices

Reply
 
Thread Tools Display Modes
Old 21st December 2014, 19:52   #1
michael peters
Regular poster
 
rover 75 tourer

Join Date: Oct 2014
Location: crediton
Posts: 59
Thanks: 21
Thanked 7 Times in 6 Posts
Default Speedy Speedo

Was driving home last night along a Devonshire B road and noticed the speedo was indicating something over 70mph. No way I thought, so today I had a little drive with my Garmin sat nav in the car which indicated that the speedo was fast by 6/7 mph at a genuine 60mph. That's 10% plus error. Is this normal? anyone else noticed this on their own cars?. My car is on it's original wheels with correct size tyres.
michael peters is offline   Reply With Quote
Old 21st December 2014, 20:00   #2
pab
Banned
 
MG ZT V6 190+

Join Date: Sep 2008
Location: Leeds
Posts: 33,223
Thanks: 41
Thanked 1,614 Times in 1,416 Posts
Default

Most manufacturers over read their speedo readouts. It's nothing unusual.
pab is offline   Reply With Quote
Old 21st December 2014, 20:08   #3
michael peters
Regular poster
 
rover 75 tourer

Join Date: Oct 2014
Location: crediton
Posts: 59
Thanks: 21
Thanked 7 Times in 6 Posts
Default

Quote:
Originally Posted by pab View Post
Most manufacturers over read their speedo readouts. It's nothing unusual.
I agree they certainly used to but I thought more modern stuff was reasonably accurate. This sat nav has been used in my Mercedes van and my sons Toyota, both these vehicles are accurate to 1 or 2mph.
michael peters is offline   Reply With Quote
Old 21st December 2014, 20:23   #4
SD1too
Doesn't do things by halves
 
SD1too's Avatar
 
Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model.

Join Date: Mar 2007
Location: Former Middlesex
Posts: 20,262
Thanks: 1,587
Thanked 3,749 Times in 3,181 Posts
Default

Michael,

There's a lengthy thread somewhere on this subject with many diverse views including just whether sat. nav. readings are themselves reliable.

If you have a message centre in your instrument pack, a digital speed display can be activated by T4. This will give you the more "accurate" speed you desire. Since the same signal drives both this digital display and the analogue dial, its likely that the error was deliberate as pab suggests.

Simon
__________________
"Whatever is rightly done, however humble, is noble."
Sir Henry Royce.
SD1too is offline   Reply With Quote
Old 21st December 2014, 22:23   #5
alanjay
Passed Away
 
Rover 75 Connie Tourer

Join Date: Dec 2013
Location: Guildford
Posts: 2,582
Thanks: 682
Thanked 979 Times in 612 Posts
Default

Quote:
Originally Posted by michael peters View Post
Was driving home last night along a Devonshire B road and noticed the speedo was indicating something over 70mph. No way I thought, so today I had a little drive with my Garmin sat nav in the car which indicated that the speedo was fast by 6/7 mph at a genuine 60mph. That's 10% plus error. Is this normal? anyone else noticed this on their own cars?. My car is on it's original wheels with correct size tyres.
Apparently there is an EU directive that dictates speedo's misread, so in a 30 mph area your speedo says 30 mph but you are doing 26/27 mph.
Lot's of threads on here about it, I now rely on my Sat/Nav for a true reading, after all if it accurately shows when I pass a side road, it must be very accurate at showing my speed.

Lot's of threads on here about it but most of us find, to get an accurate speed reading, let the needle point 5 mph above the speedo marking.
alanjay is offline   Reply With Quote
Old 21st December 2014, 22:31   #6
michael peters
Regular poster
 
rover 75 tourer

Join Date: Oct 2014
Location: crediton
Posts: 59
Thanks: 21
Thanked 7 Times in 6 Posts
Default

Quote:
Originally Posted by alanjay View Post
Apparently there is an EU directive that dictates speedo's misread, so in a 30 mph area your speedo says 30 mph but you are doing 26/27 mph.
Lot's of threads on here about it, I now rely on my Sat/Nav for a true reading, after all if it accurately shows when I pass a side road, it must be very accurate at showing my speed.

Lot's of threads on here about it but most of us find, to get an accurate speed reading, let the needle point 5 mph above the speedo marking.
I take your point and see the logic, agree re sat nav but as I said previously, two other cars I checked were almost spot on speed wise.
michael peters is offline   Reply With Quote
Old 21st December 2014, 22:36   #7
klarzy
This is my second home
 
none but not gone

Join Date: Mar 2013
Location: March, Cambs
Posts: 16,437
Thanks: 894
Thanked 4,247 Times in 3,025 Posts
Default

Quote:
Originally Posted by michael peters View Post
I take your point and see the logic, agree re sat nav but as I said previously, two other cars I checked were almost spot on speed wise.
most speedo's are between 4 and 10% over actual
the digi speedo on the ipk is more accurate but depends on tyre size and pressure..
__________________
[SIGPIC][/SIGPIC]….All praise Bananaswan….
klarzy is offline   Reply With Quote
Old 21st December 2014, 23:27   #8
NickAX54
Avid contributor
 
MG ZT-T

Join Date: May 2014
Location: Romford
Posts: 203
Thanks: 35
Thanked 33 Times in 28 Posts
Default

As tyres wear out they could be anything up to 30mm smaller on the circumference over new tyres. So maybe manufactures build this in. Not sure though
NickAX54 is offline   Reply With Quote
Old 22nd December 2014, 00:18   #9
bl52krz
This is my second home
 
bl52krz's Avatar
 
Rover 75 cdt club + Rover 2.5 KV6 Conni SE

Join Date: May 2008
Location: Birmingham
Posts: 11,356
Thanks: 6,587
Thanked 2,262 Times in 1,729 Posts
Default

BBeen through 50 mph areas on the m/way at 55mph and never had a flash on the cameras
__________________
Great Barr, Birmingham.
bl52krz is offline   Reply With Quote
Old 22nd December 2014, 00:40   #10
alanjay
Passed Away
 
Rover 75 Connie Tourer

Join Date: Dec 2013
Location: Guildford
Posts: 2,582
Thanks: 682
Thanked 979 Times in 612 Posts
Default

Quote:
Originally Posted by michael peters View Post
I take your point and see the logic, agree re sat nav but as I said previously, two other cars I checked were almost spot on speed wise.

I think I'm right here but if you can pin point just how far out your speedo is, Klarzy can make you a re-calibrated speedo facia.

If I'm wrong I'm sure Klarzy will correct me.
alanjay is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 10:31.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright © 2006-2023, The Rover 75 & MG ZT Owners Club Ltd