Thread: tyre size

7.50R16 was the original size. It's the same rolling diameter as the 235/85/16.

According to my GPS, my '95 defender speedo is out by about 5-7km/hr at 100K/hr when running my around-town 235/85R16 tyres. It overstates the speed, hence others passing you.

When I run my 255's, the speedo is correct.

I believe others experience the same issue/results.

Originally Posted by isuzu110

According to my GPS, my '95 defender speedo is out by about 5-7km/hr at 100K/hr when running my around-town 235/85R16 tyres. It overstates the speed, hence others passing you.

When I run my 255's, the speedo is correct.

I believe others experience the same issue/results.

Yes. Many others have reported similar figures. Mine, on standard tyres overreads by 7%. Most but not all cars do overread, at least when new - it is outside ADRs for it to underread. A very few are spot on.

John

my 96 def90 came out on 205 16s. I changed them for 265 75 16s which makes my speedo read 100 when I am doing 103 via the gps. You change the speedo pinion for one with more teeth. one has 22 teeth the other has 20.

Same on my Disco with the cooper sts, I was overtaken doing 110kph, think all these maniacs on the road, then passed a speed detector device that said I was only doing 101 kph. with that difference at least you shouldn't get any speeding tickets

Yep, my 96 Def overreads by 5-6 km/h at 100km/h. it kinda annoys me but then I get ambushed by a speed camera and I drive through without it going off, so it's saved me fines.

Slight thread hijack warning but semi related:

Incidentally you talk of doing the speed limit of 110km/h. I have found that my Tdi likes to sit at a max indicated 105 (100) on country runs. I know it's what your engine is used to that counts but fuel economy is a lot better on most cars if you just drop it to 100.

Last year when our convoy (2 Defenders, a Troopy and a Prado) went on the annual 9000+km trek from Perth to NT, fuel was extremely expensive and we agreed (eventually, some were not so keen) to all take a chill pill and roll along at 90-95kmh. Well we saved a lot of money, Defenders got over 10k to the litre loaded and off road. The guzzling Toyota drivers were delighted they showed even better improvement.

But what's more significant to us is everybody agreed that for that small change in cruising speed, fatigue was way down and we enjoyed the scenery more and saw more.

So the moral of the story is, whatever you speedo is saying, when out in the country slow down and let the hoi polloi past.

Okay I sound boring, but I'm right.

must admi i sit mainly about the 90-95 klm the defender seems to be built for this speed must be all thoughs narrow roads in england

I find 90 kmh annoying as you don't have enough revs or momentum to get up hills like you do at 100-105 kmh, and you need to change down more often.

Jeff