tyres + speedo

[markd]

hi there got a question for all u in the no. if i raised my tyre size from say
265x70/16 to 265x75/16 whould i need my speedo recalibrating & if so were
can u get it done . cheers mark

 

[m4dc0w]

from 70 - 75 is just the width abouyt 1/2". No recal of the spedo is required.

-mc

 

[Howard]

I am running 265*75*16's and as far as I can tell the speedo is now more accurate than it was. (tested against a sat nav unit and speed cameras). It would appear that with the standard 255*70*16's at an indicated 70 you are actually doing about 66. With the 265*75*16's 70 is just about spot on. Beware that you will get some rubbing on the inner arches with no lift.

 

[markd]

hi . i've looked on the us site and they say if u go to a bigger tyres u need it doing , confussed .com

 

[Howard]

Personal experience tells me that with 265*75*16 you are ok. Any bigger and you would have to do several things. Lift it, change the gearing and calibrate the speedo.

 

[markd]

hi . forget the last bit . and thanks for putting my mind at rest i'll go for the bigger tyre thanks guys

 

[m4dc0w]

if you go bigger... Yes you do, from 235 75r15 to 265 75r16 I noticed a 10% discrepency to my spedo. It was showing me going 10% slower than I actually was. Depending on you X, it can be a computer adjustment or a gear adjustment.



but the sizes you indicated is a change in width not height.

-mc

 

[Howard]

Our x's come with 255*70*16 as standard so the speedo's are set for those. The change to 265*75*16 is nearly an inch in diameter as well as width.

 

[Ian5700]

I can also confirm that 265/75/16 tyres will fit fine with no lift. I was also concerned at the time when i was first thinking about increasing tyre size, as a lot of the info on the forum points to needing a lift, but this is not needed. The rubbing isn't really noticeable, except on full lock. You will get the front tyres touching the top of the wheel archs if you are used to going over speed bumps like they aren't there. But none of the rubbing will do any harm, just noise.

 

[kevin p]

I agree with howard. I run standard 255/70/16 and at indicated 70mph the sat nav shows 65mph. 75 series will increase the height of the tyre ie; the circumference, and should make the two readings more or less spot on. The 75 makes a difference to the height not the width.

 

[dugco]

The section height is a percentage of the width so if its 255mm wide and a seventy series tyre the hight of the tyre will be 70% of the width. it will alter the speedo. but like you say, may make it more accurate be carefull when going to high with tall cars they can roll if you have a blow out at speed. sorry for been boring I have spent to long in the tyre trade and seen some nasty things with tyres

 

[markd]

hi there thanks everyone jobs a good'n

 

[shaunskiman]

My Ex is booted with 265/70 16 and at 70 mph my Navman reads 67 mph and when I doing a ton it reads 96 mph or :thumbdwn: who knows

Cheers Shaun