For a while, the odd time I drive my partners Vectra, it's always seemed like at 30mph especially, I'm travelling quicker in her car than at 30 in mine. I know some cars do feel quicker than others at certain speeds, but this was really noticable. Decided to do a little test today.

She drove in front of me, and when she reached 30, put her hand out of the window. Not an exact test, I grant you, but would get me near enough. Turns out my speedo reads 34. Tried it at 50, mine reads just over 52. I'm obviously some way off.

Now I know that so long as I go at 30 by mine past a speed camera, I'll never be done, but that's not the point.

Where do you get speedo's recalibrated, and how much is it?? A place in NE England would be spot on.

Thanks,

Andy.

 

ive got 225-35-18 on my clasic and its way out, ive just been through a speed camera at 30 mph on my speedo, and it flashed, ive been done for 35 in a 30 so beware, i need 215, on really but as i get my toyos at £50 ea, off ahem some one they cant get any 215, or 205, so im stuck with 225-35-18,

 

get yourself a micro road pilot,its a gps camera detector that gives you a sattelite readout of your speed...@ 30mph my speedo says 32mph,@ 62mph my speedo says 65mph,and @ 148mph my speedo says 152mph;all testing done on a private road of course.

BM

 

the 215 205 part of the tyre size is the width so it wont make any differance...

BM

 

I have recently fitted 215/45's to both front wheels, whereas the old tyres were 215/40's. The backs are still 40's.

Would this make that big a difference. Not sure if the car seemed slower at 30 before the new tyres were fitted. Can't remember when I first noticed it.

Andy.

 

had some wheels on my classic with 215/45/17 tyres and had to pull them off as they were over an inch higher than the standard wheel size

 

A good gauge to check your speedo accuracy is to follow an HGV when you are on the motorway. they are speed limited to do 56 mph. they are checked every year at MOT time. Some are "fiddled" to go faster, but if you see several in a line you know they're reading the same. Most cars show roughly 59 mph.

 

the aspect ratio is 35, so if you have a 225-35 -18 then 35% aspect ratio is of 225, but if the width was 215, with an aspect ratio of 35% then it is 35% of 215, so its less, so width with the same ratio does make a difference, havent you ever worked it out, lol every one knows if you had a narrower tyres but with the same aspect ratio then the rolling dia is smaller

 

of course i know this,but at the end of the day 35% of 225 gives a 78mm wall and 35% of 215 gives a 75mm wall,therefore being as the difference between the 2 is less than the difference between a new and a worn tyre this wouldnt make a noticable difference.

BM

 

i would imagine this would cause a very uneven wear between front and back by having different sizes on,im not 100% sure but its something to do with the 50/50 dif IIRC.

BM

 

The backs are getting changed soon, 1 ain't got much life left in it.

Andy.

 

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