wheel size help

[simon.m]

hi guys this is not for my car but my misses fiat she has not had it long but it come with after market wheels looking in her book the car could have come with 14/60/165 or 14/70/165 its not the wideness i need to no its the wall hight for the speedo being put out it now has 17/40/205 would like to no if this would throu the speedo out and if so how much by and from what speed like if she is doing 30mph


thanks guys

 

[4NT]

Do you have a sat nav? If so see if you can get it to display current speed. But, bear in mind most analogue speedos are out slightly and the higher the speed the less accurate they are.

Don't know if that is any help whatsoever to you mate???

 

[simon.m]

yeah i have one but was more worried about low speed like 30mph as we have speed cams here and think she may have got a flash evan though she was doing 30 on her speedo

 

[4NT]

Your GPS / Nav should register and make a good comparison for you at low speed too. To be fair I think the wrong tyre should only throw the rolling radius out a tad anyway.

Some speed cameras flash during self calibration and testing etc. Awful feeling waiting on a fine dropping through the door though eh!

 

[simon.m]

yeah its not nice at all mate will go have a test now but if any one can put some real light on it for me would be very thankfull.

thanks again 4nt

 

[4NT]

No worries, good luck.

 

[jbcalvin]

To give a comparison, I have 16" winter wheels with 55 profile tyres, however my summer 18's run a 40 profile, so going from a 14" to a 17" then a drop in profile from 60 to 40 would be pretty right, possibly a drop to 35??

 

[simon.m]

so the sat nav is on 29mph when the speedo is on 30mph still dont how much the 17 would change it so i can tell her to do say 27 and that is 30 ;-(

 

[gavsman]

Here's a good calculator.......Visual Tyre Size Calculator | Kouki Tech

 

[simon.m]

that shows evan mine are out s**t i went from 16 55 to 17 45

 

[simon.m]

oh i did not put the widness in as i thought it would not matter but it does now says mine are ok lol

 

[quattrojames]

You need to put the width in otherwise the profile means nothing, as it's a percentage of the width.

 

[simon.m]

yeah see that after my post mate ;-) mine are ok misses ones are hit and miss as we dont no what wheel size was on it from new and fiat dont ether. i put both in and one put it at 31 at 30 the other is 29 at 30 but if she is doing 31 at 30 can fix that by droping the side wall from 40 to 35 but its like no tyer at all as it is so she will have to drive at 29 on the 30s lol