Big Wheels && mis-reading speedo!

[Adamsy]

Do any of you other guys with 19's or 20's with skinny rubber have any problems with the Speedo reading all over the show? at 60 i usually find other cars are right up my butt but then on the odd occasion i seem to slowly pull away from them, then today i get a speeding fine but I’m always very careful around town so I’m sure my Speedo is right up sh!t creek! Anybody else had any troubles with this?

can I can my Service department to recalibrate the Speedo at all?

damm pigs lol :P

[whitestivo]

i read my speed off the gps now, regularly 3-4km faster than i expect from speedo

whitestivo

[DJKOR]

What size are your tires? Remember that a factory Toyota speedo is going to be out a little to start with and then changing your wheels/tires is going to affect this positively or negatively. Every car will be out by a different amount. At least with your tire size, we can calculate which way it is swaying now.

If you have a GPS, this will be useful for obtaining your close to actual speed so you can then determine what is actual speed versus what is shown on the dash.

Toyota themselves won't recalibrate it. The best they will do is replace it if they can be shown that it is more than their 'allowable' 10% error. Otherwise, if you are game, you can build this kit up and install it:

SPEEDO CORRECTOR MKII KIT

i read my speed off the gps now, regularly 3-4km faster than i expect from speedo

I just don't use my speedo

[Adamsy]

Well im running 19 inch advanti gauntlets with 245/35ZR19's, im thinking now that 245/40zr19 would of been a better option because it seem to be between 5-7kms out or so i thought but after today i'm not so sure i worked that out right lol my bad. might have to keep the sat nav in the car at all times now just to be safe... :s

[DJKOR]

With a 235/45R19 tire, your speedo will read approximately 2.175% faster than what it was reading on the stock 215/55R17's. Strange considering from the sounds of things, your speedo is inaccurate in the opposite direction. You can use the calculator here to obtain those figures:

1010 Tires - Tire Size Calculator

[Adamsy]

yes spot on mine reads the other way, to be doing 60 the speedo needs to be showing around 65 not 58 as that calculator suggest :S so im not really sure might have to get the sat nav out again and check again see what the go is :S

[VF-X]

I usually add up around 3-5k on the speedo. And when it's crowded, I just matched the speed with most drivers. An increase in rims' diameter by 2" on a sedan i'd say would have errors around 5-10% of the odo speed..

[DJKOR]

yes spot on mine reads the other way, to be doing 60 the speedo needs to be showing around 65 not 58 as that calculator suggest :S so im not really sure might have to get the sat nav out again and check again see what the go is :S

The calculator can make things a little confusing. It gets me as well. When it says it shows 2% fast, it means that if the speedo says you are doing 100km/h, you are actually doing 98km/h.

Your OP kind of has two opposite scenarios. The first is where you mention that when you believe you are on the speed limit, other people are on your tail. This would be a case of your speedo being fast... which would be correct given your new tire size. From factory, the Toyota speedo usually has an error like this, then when you change your tires as above, you make this error even larger.

But that said, in your OP you also mentioned you got a speeding ticket despite being careful. This would lead me to think your speedo is actually showing a speed slower than what you are actually doing... which goes completely against what has been calculated as I mentioned above.

As I said, it's a little confusing but hopefully you can get it.

So if your speedo is out as per the second paragraph above, then this would be correct and mainly comes down to your new tire/wheel combo.

[Tofuboi]

As DJKOR has stated. This has occured to me aswell after moving from 17" 215/55R17 to 18" 235/45R18's.

The speedometer beforehand would read exactly 2km/h over when doing 100km/h by GPS.

GPS = 100km/h

Speedo = 102km/h

Now it's like this.

GPS = 100km/h

Speedo = 108km/h

That's a 6km/h jump. Pretty scary to be honest, but I dare not go near 108km/h JUST incase it's not as accurate as ive figured it to be. :P

[Adamsy]

Sorry guys i think i have confused my self and you guys.

When i had the rims put on the ZR6 i also put the GPS in the car and at an indicated 60kms on the GPS the speedo would read around 65-67 (was a little hard to be exact with the ZR6's speedo as we all know it has ***** poor markings on it) So after that i figured if i drove around with the speedo showing 65 my true speed would actually be something like 58-60kms which is why im that puzzled to of got a fine...

Might put a different GPS unit in the car and see what it comes up with just to be sure?

[Adamsy]

Sorry guys i think i have confused my self and you guys.

When i had the rims put on the ZR6 i also put the GPS in the car and at an indicated 60kms on the GPS the speedo would read around 65-67 (was a little hard to be exact with the ZR6's speedo as we all know it has ***** poor markings on it) So after that i figured if i drove around with the speedo showing 65 my true speed would actually be something like 58-60kms which is why im that puzzled to of got a fine...

Might put a different GPS unit in the car and see what it comes up with just to be sure?

[David the Viking]

Sorry guys i think i have confused my self and you guys.

When i had the rims put on the ZR6 i also put the GPS in the car and at an indicated 60kms on the GPS the speedo would read around 65-67 (was a little hard to be exact with the ZR6's speedo as we all know it has ***** poor markings on it) So after that i figured if i drove around with the speedo showing 65 my true speed would actually be something like 58-60kms which is why im that puzzled to of got a fine...

Might put a different GPS unit in the car and see what it comes up with just to be sure?

I have found the TRD to give the same inaccuracy that you have found with 19's on the ZR6. The TRD also using 245/35/19 tyres.

A positive is that you are less likely to get a speeding fine!