Want to remove ads? Become a MK3OC Club Member today!

Speedo seems to be out!!

Joined
Feb 6, 2010
Messages
392
Reaction score
0
Location
Milton Keynes
Hello peeps,

I reckon my speedo is out by about 7-10mph, i have plugged the sat nav in and this seems to agree with what i thought.

I am running the standard 15's with 195 55 15 as it came with out of the showroom.

Is there a way of adjusting this other than altering the tyre sizes?

Cheers

Dan
 
Joined
Jan 31, 2009
Messages
109
Reaction score
0
Location
Milton Keynes
Hello peeps,

I reckon my speedo is out by about 7-10mph, i have plugged the sat nav in and this seems to agree with what i thought.

I am running the standard 15's with 195 55 15 as it came with out of the showroom.

Is there a way of adjusting this other than altering the tyre sizes?

Cheers

Dan

Hello mate,

What speed are you doing? as you will notice that your speedo will be out by around 4-5mph when say you're doing 70ish.. I wouldnt worry about it mate..

Noticed that you are from MK, where abouts mate? as i am from MK also...

Cheers

Lee
 

Andy_Mk3

Administrator
Club Staff
Club Member
Joined
Apr 10, 2008
Messages
39,698
Reaction score
768
Location
Lincolnshire
Vauxhalls are bad for over-reading, especially at 70+ .. when my speedo reads 100 sat nav says about 94.. tested this on private land of course :thumb: but at 70mph on the speedo, satnav says about 66mph
 
Joined
Jan 15, 2008
Messages
10,276
Reaction score
49
Location
Swindon
mines even worse than that, when im doing 70, im actually doing 63, its well gay
 
Joined
Dec 18, 2009
Messages
215
Reaction score
0
I was wondering what tyres to get for my car and thought they would affect the speedo. When you look at the different sized tyres Vauxhall sold the cars with it's no surprise the speedo's are out. I haven't actually looked so I don't how many different speedo drive gears are available. If they are the same all of the cars will be a bit out.
My car originally had 155/80x13 tyres but a lot come with 175/70x14 or 185/60x14 and when you look at the tyre diameters there is a bit of a difference.
Have a look on here and you can calculate what the differences are.

http://www.carbibles.com/tyre_bible.html
 
Joined
May 9, 2008
Messages
2,156
Reaction score
18
Location
West Midlands
I was wondering what tyres to get for my car and thought they would affect the speedo. When you look at the different sized tyres Vauxhall sold the cars with it's no surprise the speedo's are out. I haven't actually looked so I don't how many different speedo drive gears are available. If they are the same all of the cars will be a bit out.
My car originally had 155/80x13 tyres but a lot come with 175/70x14 or 185/60x14 and when you look at the tyre diameters there is a bit of a difference.
Have a look on here and you can calculate what the differences are.

http://www.carbibles.com/tyre_bible.html

The different diameters/tyre sizes wont make a difference if the rolling circumference work out to be the same.
 
Joined
Dec 18, 2009
Messages
215
Reaction score
0
The different diameters/tyre sizes wont make a difference if the rolling circumference work out to be the same.

Hi, yes you are right it's just that some of the sizes that Vauxhall offered standard are different.
I have a parts cd and was just looking at the speedo drives, the gear on the diff and the speedo's themselves. I think all the drive gears have 13 teeth, all the diff gears have 26 teeth. There are a few different speedo versions and these should correct and differences in tyres size.

Has the speedo been changed in the car or non original sized tyres been fitted ?
 
Joined
Dec 18, 2009
Messages
215
Reaction score
0
I have in the past rung up a tyre manufacturer to find out what the wheel revs per mile figure is for a particular tyre. I think it's that figure that is written on the speedo on Astras, I know thats the case on Triumphs and Mini's.
Different makes of tyre that are the same size can be different so I suppose a combination of all the wrong things can make quite a big error.
At least it's the right way. I swapped a back axle on my Triumph and forgot about the speedo. Needless to say I got a fine for doing 82 in a 70 limit, made me sort the speedo out though.
 

Users who are viewing this thread

Top