Speedo accuracy

[ganyb]

So does anyone know if the Corolla speedo is electronic or cable driven. I was just wondering how speedo accuracy is maintained when changing wheel size (say from 16 to 17)?

I know on some electronic ones you can reprogram the module, but if it's cable I dont know how you'd be able to adjust it.

A copper friend of mine said that an inaccurate speedo makes the car unroadworthy, and technically your insurance will not apply if you dont maintain the car in a roadworthy condition.

If you have a prang most insurance companies will look hard for reasons not to honour the claim and this could be a good one.

Any thoughts folks..??

[Blade Hunter]

Generaly when you increase wheel size you would decrease the profile of your tire so the diameter for the wheel plus rubber would be the same there would simply be more alloy and less rubber.

Therefore increasing to 17s should theoreticaly not make a difference assuming you follow what I said above and get a lower profile tire.

[Exec6speed]

Blade is right on the money... When you change wheel size you should be attempting to maintain the same rolling diameter... Thats why you need a good tyre shop...

BTW my Stivo shoes 4 kms slower than what its reading on the cluster... Checked that with a Garman GPS...

[xTiGeRx]

i presume it's eletronic. the reason why is that....

i had a lancer 2001 model. and took the dash apart. and the instrument cluster just 'clips' off the back of the dash...and all it is is eletronic contacts.

so..i presume that the corolla would be the same..because it's newer.

(hopefully)

m2cw.

[illuminati]

liek blade said, u should use a lower profile of tyre to maintain the same diameter.

if u dont then ur car will have slower acceleration and i cant see why anyone in their right mind would want to do such a thing.

[peekay]

They are definitly electronic they have no cable on the back of the cluster other than wires.

[ganyb]

Cool..cheers guys.

[jaxx]

if it helps ppl have a look at this site at the wheel size conversion, rollin radius bit

Car Bible

[jamsbong]

ok instead of starting a new topic. I'll continue on this one.

I've known that the speedo on default wheels 195/60 r15 reads wrongly slower. about 5km/h slower from 60km/h+

so I don't really have to "wipe off five" if I choose to be staring at the speedo all the time.

anyway... using the tyre size calculator

http://www.miata.net/garage/tirecalc.html

and the gear-ratios on brochure. I've worked out what is the RPM for

60km/h = 1943rpm

100km/h = 3239rpm

120km/h = 3880rpm

max speed 185km/h at 6000rpm (max power)

197km/h = 6400rpm (at rev limit)

the speed is actual speed (not speedo) and calculated based on fifth gear of a conquest (not sportivo)

I've never reach more than 170km/h coz I have not found the right place to do it and I am too scare to run it when it is windy.

but the calculations says that it is possible to almost reach 200km/h if one is one a downhill or extra tailwind. :D

i suppose bigger size wheel will make the speedo accurate and reduce the milleage on my ODO. but it willl make acceleration slower. overtaking slower too and maybe consume more fuel.

[DANZZT231]

Wow this topic is back from the grave.

Anyway, I was on freeway last week and there was this speed check sensor on the bridge where u can see how fast u r going. I was driving 100km/h, but the speed check sensor indicate 93km/h. Must be the 215/40/17 tyres. Cool, never will I pass the speed limit.