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g40 and gt tyres

what size should they be and are they different on the 2 models

my g40 wheels had 175/60/13's
my gt had 175/65/13's

so i have put 175/60's back on due to them looking better on the car is this the right move or not

Yeah they're meant to be different sizes, 175/65 on the GT and 175/60 on the G40.

Krupa wrote:Yeah they're meant to be different sizes, 175/65 on the GT and 175/60 on the G40.

165/65 R13 on the GT, 175/60 R13 on the G40.

Oops!

yeah 175/65/13s is too high a profile for a gt/g40, itll make your speedo slightly out. Its a perfect size for a 1.3 SPI ranger though.

Has anyone else tested their speedo?

Mine reads over anyway, with the alloys on it still reads about 3mph too low (tested with a Road Angel) at pretty much any speed, tested up to about 65mph.

With the steelies on that must be an even bigger difference.

Tested it before adjusting the mileage on the G40 clocks, and set about trying to make it more correct afterwards but it wouldn't have it so put it back the way it was.

Apparently the speedo in my mechanic's Rover is out by about twice that on standard wheels.

hmm

i had the 8P box in mine with 185/60/13s and now have the GT box in with 185/60/13s (tar) 175/70/13 (gravel) and 185/55 /14 for economy super hard tyres!

any one recon my speedo is out, i used a tyre size converter on the club polo website and came out with 185 55 14 from 145/80/13 stock but the gt box is probably sendeing this all to cock

I thought you ran around with your speedo disconnected anyway Pinches?

i'm now running 175/60/13's on my G40! was wot was on there in the first place!

gofasterpinch wrote:hmm

i had the 8P box in mine with 185/60/13s and now have the GT box in with 185/60/13s (tar) 175/70/13 (gravel) and 185/55 /14 for economy super hard tyres!

any one recon my speedo is out, i used a tyre size converter on the club polo website and came out with 185 55 14 from 145/80/13 stock but the gt box is probably sendeing this all to cock

the box wont make any difference, all the calibration is done at the speedo end. do you still have non-standard dials in? I think on both my cars its' pretty much on the money when compared to the ratios spreadsheet. but I only ever consciously check when im in 5th gear...

Mine's been about right from Mark's spreadsheet with CL, GT, G40 and Golf 1.3 'boxes on it too - maybe the speedo is optimistic by a few mph. But hard to read speedo and rev counter accurately whilst on the move though - wish I had a Road Angel!

As do I, they're cool.

Only problem is that like mobile phones they go out of coverage every once in a while. Pain in the ass when you're testing a speedo driving around rural Wales.

(If you're wondering, I borrowed the one out of my mechanic's scary as f**k 250bhp Rover 820 Vitesse turbo street sleeper)

are the phone boxes on the motorway still 1km between each? and is that an accurate measurement?

do remember trying to calibrate it by that before. think it was reading something silly like 57mph at 53 and the like. Almost the full 10% legal allowance.

actually to carry on from the quarter mile strip idea i had a couple minutes ago (on a 1/2-mile-plus straight/flat bit of road near by) that would be a handy way of calibrating as well. sure know i dont trust the one in the astra below about 50, and only tenuously above it. (the revcounter doesnt match with the speedo, using the (fairly bombproof so far as i can tell) mph-per-1000 ratings or even if you compare yourself - the ratio is different at higher speeds in the same gear from low ones!)... same story with the polo, but not quite so bad.