how to get accurate speed after changing size of tyre/rim???

bfb515 · 05-06-2008, 09:25 PM

as we know, the rate of speed shown at the speedometer change after changing rims or tyres..
for example...
original wira use 13' rim, the speedometer show the accurate/nearly accurate speed on land...
if we change the rim to 16', the speedometer doesn't show the accurate speed on land...might be more or less...
so..
any idea...
how to solve the prob???
sifus???

DLegend · 05-07-2008, 12:57 PM

the original speedometer also not 100% accurate. (got +-5% error).

The only accurate one is GPS. Even RSM won't be 100% accurate.

bfb515 · 05-08-2008, 02:50 PM

13' change to 16'
how much/percentage is the different?

DLegend · 05-08-2008, 03:24 PM

try this:

http://www.1010tires.com/TireSizeCalculator.asp

simon · 05-09-2008, 01:07 PM

ok my wira original was 175/70/R13 & i have changed several sizes over the past few years...like 185/60?R14 , 195/50/R15 and now im on 205/45/R16 ..... i always get my friend on a wira with stock sized rims to run alongside with me on a free road to check our speedo......my speedo is still acurate.....i was not satisfied and then i checked with my sis kancil.......it was also same..... the can be some difference though...like +-5 kph....but it shd NOT be a cause for concern much.....

FVel · 05-09-2008, 05:25 PM

If your new overall tyre diameter is significantly different, the reading is going to be out.

+/- 5kph may appear fine but if you plan to tease the highway speed limit by, for example, 10kph you may end up going beyond the leeway threshold that the cops will allow.

I don't think it is such a difficult thing to get the speedometer recalibrated. Those tuning shops should be able to do it easily enough.

Shah790120 · 05-14-2008, 04:18 PM

Dear all bro's,

you shouldn't be bothered by this ....
this is because no matter what sizes your tires are ..
your speedometer will still be accurate (+- 5%)
the thing that count your speed is at the center of the tires ...
some cars might have gap but its a consistence gap ...
so its the same ...

imagine a circle ..
mark a spot 5cm from circle center ..
then you role the circle few times ..

then try to make another bigger/smaller circle ..
mark a spot 5cm from the circle center ..
then you role the circle few times also ..

the SPOT you mark is going through same speed with the other circle ..
notice that?

the circle is your tires ..
the marked spot is your speed cable from your speedometer ..

thats why when you try to run alongside with other cars its still same ...

DLegend · 05-14-2008, 05:51 PM

Quote:

Originally Posted by Shah790120

Dear all bro's,

you shouldn't be bothered by this ....
this is because no matter what sizes your tires are ..
your speedometer will still be accurate (+- 5%)
the thing that count your speed is at the center of the tires ...
some cars might have gap but its a consistence gap ...
so its the same ...

imagine a circle ..
mark a spot 5cm from circle center ..
then you role the circle few times ..

then try to make another bigger/smaller circle ..
mark a spot 5cm from the circle center ..
then you role the circle few times also ..

the SPOT you mark is going through same speed with the other circle ..
notice that?

the circle is your tires ..
the marked spot is your speed cable from your speedometer ..

thats why when you try to run alongside with other cars its still same ...

Bro, what are you talking about?

The circumference of the wheel will affect the total revolutions per kilometer, which will in turn affect the speed reading. Refer to this:

The RED CIRCLE shows how many times the wheel will spin in a mile (different sizes of tyres and rims) , which will surely affect the speedometer reading.

The BLUE GREEN box shows the resulting difference in percentage (the speedo reading)

Using this example, the best upsize from a Waja standard tyre (195/55/R15) is to go to 205/40/R17 (plus 2 upsizing), but then again, its blardy uncomfortable because of the 40-series tyre.

Figures and results from : http://www.1010tires.com/TireSizeCalculator.asp

cYBorG · 05-14-2008, 11:27 PM

useful info indeed bro DLEgend..

DJgErM · 05-17-2008, 04:51 PM

yea..i do agree with Legend's statement as RSM isn't that accurate too..But like normal GSM map navigators could give your actual velocity..

if i've not mistaken, the rsm gets the signal from the ecu and its similar like our meter right?sorry..i am a noob..and the diameter of the rim is the factor..

szekeiemme · 05-18-2008, 12:16 AM

i tot RSM got those tire size setting wheel size setting? correct me if im wrong..

monazarudin · 05-18-2008, 01:51 AM

you're not wrong.. but you need to install the separately sold G sensor..

joexxo · 05-19-2008, 12:24 AM

bro,
just a thought.... 175/70/13 = 185/60/14 = 195/50/15 = 205/40/16 i think the total diameter for all this read the same except the tire wide. we increase the rim diameter but we decrease the tire thickness. so its suppost to read same diameter. (ye ke ni )

i've tried stand 3 size of rims which is 70/13, 60/14 and 50/15 the result same height. when stack upon another same diameter. Dunno la.

maybe im wrong

alantan350 · 06-13-2008, 12:09 PM

http://www.1010tires.com/TireSizeCal...?action=submit