Speedo error

[ne jones]

If i fit 235/85x16 mud tyres to my discovery what difference in speedo reading either slow or fast can i expect.

Additionally what difference is there likely to be in fuel consumption?

[shaun and co]

dont know what you'll get with 235/85- i guess it depends where you start from but i did notice today that with 275/75 my speedo is now nearly spot on accurate according to road angel. first time for everything!

[Disco-Ron]

Use this,
http://www.tyresave.co.uk/tyresize.html
put your original tyre size in, and the new, and it'll tell you the difference in %

[thermidorthelobster]

On the Disco II, 235/85s are exactly 10% larger than the standard tyres, as are 265/75s for that matter.  But I can't remember what the standard tyres are on a Disco I.

[Bulli]

like Shaun said, best to borrow a gps if you can as they are miles out as standard and you may find it is now accurate!

[ne jones]

thanks for the replys.

L know that borrowing a gps on the 235/70x16 tyres the speedo is just 2 mph slow.

Using the table above there is a difference in size of tyres of 9.77%

Would that make the speedo that amount faster or slower?

[Budgie]

It should (IIRC) make it read slow as you have a larger distance to travel per rev of the wheel.
If you go for 235/85's then you can bring the speedo back to near normal by fitting a speedo drive gear from a 110 to the Disco or if you phone Ashcrofts and tell them the vehicle, transfer box ratio and tyre size then they should be able to supply you with the correct drive gear.  

[JimsMowing]

On the Disco II, 235/85s are exactly 10% larger than the standard tyres, as are 265/75s for that matter.  But I can't remember what the standard tyres are on a Disco I.

235-75-16

[gimpy]

I have a D2 and run 255/55 18's with AT2 on for general running around and then chang to 235/85 16 with insa sahara on and the difference is 5 mph fasterwith std ratios. this was confirmed by the tom tom.

[ChrisW]

On the Disco II, 235/85s are exactly 10% larger than the standard tyres, as are 265/75s for that matter.  But I can't remember what the standard tyres are on a Disco I.

235-75-16

 :oops: 235-70-R16 or 205/80's  

It is about 10% slower, with 235/85/R16's on mine, doing 65 on the speedo is about 72 on the gps but as with all things LR YMMV!

[Tyke]

It should (IIRC) make it read slow as you have a larger distance to travel per rev of the wheel

For the record, i'm on 265/75's at the mo and the gps is just about spot on with the speedo.

[Range Rover Blues]

Both mine and Tim's are now accurate with that size of tyre on.

[gords]

I have 235/85 x 16 BFG Muds - the speedo is exact upto 50mph, reads slightly slow at 60mph and at an indicated 70mph it is doing around 75mph (by GPS).

[petergalileo]

I have standard wheels fitted to my discovery ES and my speedo is 5 mph too slow according to my GPS which I now use as a speedo.  Was going to try and calibrate it myself but havent done anything on it as yet.

[imspanners]

You need FRC3310 which is the speedo gear from a 110
The downside, is the square drive for the speed sensor is too big.
So you need to pop a couple of slithers of pop-can into the square slot to pack it out!  

My speedo is now 100% accurate at all speeds up to 80mph (don't go over that it's a Defender transfer box!!  :shock:

[BigA]

I have 235/85 x 16 BFG Muds - the speedo is exact upto 50mph, reads slightly slow at 60mph and at an indicated 70mph it is doing around 75mph (by GPS).

I have 265/75/16 BFG's Muds, and almost identical to gords  :?