tyre information

i run 265/70/16 on my pajero. my speedo when on 100 is really only 95, this is true with all speeds eg 80 is 75 etc.

what profile should i get when replacing soon to get a more accurate reading.

65 profile?
75 profile?
cheers
keith
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Reply By: ExplorOz - David & Michelle - Monday, Oct 21, 2013 at 20:23

Monday, Oct 21, 2013 at 20:23
Keith,
Try the tyre size calculator I linked into your thread you can put in various sizes and it will work out the speedo difference for you.
David
David (DM) & Michelle (MM)
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AnswerID: 520128

Reply By: Robin Miller - Monday, Oct 21, 2013 at 20:24

Monday, Oct 21, 2013 at 20:24
75 so your tyre rolls further per revolution and you go faster per rev so 95 will be around 100
Robin Miller

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AnswerID: 520129

Reply By: Member - Phil G (SA) - Monday, Oct 21, 2013 at 20:48

Monday, Oct 21, 2013 at 20:48
265/75R16 will increase your real speed by 3.5 kph at 100kph - so you'd get 100 on the speedo when you're doing 98.5 - pretty close.
But I wouldn't change just for this reason.
The upside of the 265/75 come in a greater range of LT construction and will give you an extra 12mm clearance under the axles, and a slightly longer footprint.
Downside is you'll lose a little acceleration, a little braking, and you'll use a little more fuel - all because the tyre is bigger and heavier. And just check to make sure a slightly taller tyre won't touch too much on full lock on the front or full compression on the rear.
AnswerID: 520133

Reply By: Ross M - Monday, Oct 21, 2013 at 21:07

Monday, Oct 21, 2013 at 21:07
Keith W
All vehicles a set with the actual below the indicated speedo reading. Yours is around normal. Mine, Dmax is 100 > 106. Some Mazda's are 100>110

Yes, you can increase the diameter to offset it a reasonable amount but if you tow and even when normal travel the fuel usage WILL increase as the engine works harder to turn the bigger leverage arm called the wheel radius.
Generally manufacturers spend a great deal of effort to tune the torque/speed and power so all is in synch. If you change it you may not be a happy man but your speedo is correct. Just use a GPS to indicate the true, (as accurate as you can) speed.
A small sacrifice.

Extra cost of tyres and extra fuel and less pulling power may see it all out of synch.
AnswerID: 520137

Reply By: Member - johnat - Monday, Oct 21, 2013 at 21:22

Monday, Oct 21, 2013 at 21:22
TBH, I'd be inclined to fit "standard" tyres. Check the user manual, or the tyre placard in the vehicle, if you can find it.
That way, the speedo will be using the settings it was designed for - weird, I know, but that way the speedo might give you a reasonably accurate reading, at least within design parameters (ADRs require speedos to be within +10%, -0% - ie indicated reading must be higher than true speed and may indicate up to 10% higher than true BUT NOT LESS than true.)
Extract from ADR 18/03 Section 5.
5.3. The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship
between the speed displayed (V1 ) and the true speed (V2).
0 = (V1 - V2) = 0.1 V2 + 4 km/h
(Bold emphasis is mine!)

That last bit specifies that the indicated speed cannot be less than the true speed, but may be up to 10% + 4km/h. So, at 100kph the speedo must indicate between 100 and 114 kph.
AnswerID: 520138

Follow Up By: Member - johnat - Monday, Oct 21, 2013 at 21:24

Monday, Oct 21, 2013 at 21:24
I had bolded the words "shall not be less than the true speed of the vehicle" but it seems not to carry through to the page, even though it showed up in preview.
1
FollowupID: 800542

Reply By: Member - KEITH W (QLD) - Tuesday, Oct 22, 2013 at 09:45

Tuesday, Oct 22, 2013 at 09:45
the pajero has the optional 16 in rims with a tyre placard visible on drivers door. mitsubishi placard.[2006 np 3.2 diesel]

i do use GPS so i will go with this to get accurate speed reading.

thanks for all the help
keith
AnswerID: 520163

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