I've been told if you have tires that are wider than what was fitted as standard it'll make your cars speedo under read depending on how wide they are? So is it true that the standard tires on a clio are 185/55/r15 and the tires i got fitted at national tyres are 195/55/r15 make my speedo under read slightly therefore they are illegal???
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Heard it was illegal for speedo's to under read?
- Thread starter JaysonD
- Start date
JamesBryan
ClioSport Club Member
As Martin said, it's the diameter difference i.e. the profile 40, 45, 50...
not the 185, 195....
Won't be a huge difference though.
not the 185, 195....
Won't be a huge difference though.
clio 172
i though the same... plus your speedo is aloud to be 10%out and changing wheel size wouldnt put it out by that much
Would it be a MOT failure?
BoatNonce
ClioSport Club Member
Being wider doesn't necessarily make the speedo over/under read. It's the middle number.
195
55
R15
This means that the tyre is 195mm wide
the sidewall height is 55% of the width
on a 15 inch rim.
When you make the tyre wider, you have to compensate by lowering the percentage sidewall height, or profile.
A 195/55/R15 isn't actually that far out, and a 195/50/R15 is about the same amount out in the other direction, so I'd be tempted to say leave it. If anything it'll make your speedo more accurate since they slightly overread in the first place.
195
55
R15
This means that the tyre is 195mm wide
the sidewall height is 55% of the width
on a 15 inch rim.
When you make the tyre wider, you have to compensate by lowering the percentage sidewall height, or profile.
A 195/55/R15 isn't actually that far out, and a 195/50/R15 is about the same amount out in the other direction, so I'd be tempted to say leave it. If anything it'll make your speedo more accurate since they slightly overread in the first place.
0.6 mph extra per every 30mph shouldn't have too much effect, other than raise the car 9mm
I'm sure National Tyres would've had the sense to fit 195/50/15 as they are a specified tyre in the clio manual, so therefore wouldn't be 'illegal'.
The police surely can not penalise you for doing so.
clio 172
no as they woudnt test it...just be a visual cheek to make sure it works if anything and if they did fail it coz of diffident size wheels {as long as they wasnt outside the body} i would tell them where to stick the MOT and take somewhere else
Golf GT & A4 Avant
Directly, no. Indirectly, yes the width will have an affect on the rolling radius.
You should have reduced the profile size when increasing the width
You should have reduced the profile size when increasing the width
0.6 mph extra per every 30mph shouldn't have too much effect, other than raise the car 9mm
I'm sure National Tyres would've had the sense to fit 195/50/15 as they are a specified tyre in the clio manual, so therefore wouldn't be 'illegal'.
The police surely can not penalise you for doing so.
Ahh, so the sidewall is a percentage of the width - which will of course change the circumference. I was just about to berate anyone who argued there would be a difference in speed - but yes, there would be a small difference. Interesting.
Roy is trolling. 185s are almost the same diameter as 195s, thus the practically the same reading will be obtained by the speedometer. It will not fail an MOT.
p.s. McGherkin has the best explanation.
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Ahhh so bascially 60mph will actually be 61.2mph? That's alright then as speed camera's have tolerances of more than that! Thank you mate!
0.6 mph extra per every 30mph shouldn't have too much effect, other than raise the car 9mm
I'm sure National Tyres would've had the sense to fit 195/50/15 as they are a specified tyre in the clio manual, so therefore wouldn't be 'illegal'.
The police surely can not penalise you for doing so.
Okay well thank you bud 10mm wouldn't make it wider than the arches anyway!
Rather good anwser like always cheers man very well explained
Agreed! In your picture looks like you have angel lights?! May i ask where you got them from?
Ahhh yeah looks like it! know anywhere where i can get the angel lights that have the 3 sidelights on each side?? I saw one once at night time and honest to god it looks mad!They are just he normal 182 Xenon's ones. Its the optic section your seeing I think
I'd wager your sat nav is wrong.
Clio 1.2 2.3 2004
But I use it for work everyday. I hope it is wrong haha
It's not that Eco on the fuel otherwise
Sat navs are always different mate, in the work van, my car, mums car, step dads car the speed on the sat nav says around 10mph slower the greater the difference and higher speeds. I know its something to do with the car says its speed by how fast wheels moving while, sat nav does it in a more mathematical way! What tyres you got anyway?
Correction, not actually 10mph but like 5!
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BoatNonce
ClioSport Club Member
10mph?!? The difference between my speedo and GPS is only 2mph at over 100, your family running go kart wheels or something?
Clio 1.2 2.3 2004
Iv got 165/50/15
I had 195/50/15 before
My wheels are 7j so they are stretched that's probably why.
Oh fair enough! Looking at my mates car yesterday his are 205/40/16 aha they are wide
