Aurion Kappa Wheels tyre Size

[andyhui01]

Hey Guys. I've just picked up a Sportivo ZR6 with some Kappa wheels last week.

I did a quick search around here to see what tyre sizes you guys run and all of you are running 225/45/18 or 235/45/18's. My cars came with 235/40/18 tyres which I found odd.

I just assumed that someone along the life of the car, the previous owner / tyre shop / dealer must have decided to use a different sized tyre for the car.

Yesterday, I was cleaning up the car and thought I'd have a look at the condition of the spare wheel (also a 18" Kappa) and I noticed that it was fitted with 235/40/18 too. (This spare is new and looks untouched, I assume it was fitted by Blood Toyota (Selling dealer when the car was new).

The tyre throws the speed of by 3%

Does anyone else here have a dealer fitted 18" Kappa with 235/40/18 Tyres?

[bigVAN]

If u dont mind, could someone please explain to me the safety risk involved here?

Messing with the wheels in changing the rim size and tyre profile will mess with the speedo reading. It'll inaccurately point somewhere where in fact you might be actually going slower / faster hence safety and obvious financial problems, like speeding..

Not only that, if you mess with your rolling diameter to the point that it is a fair bit of a change (3% is usually the maximum change recommended), if this is in the negative direction (smaller) then that means that for a given speed, your wheels will be rotating faster. Your brakes will then be working harder as a result.

Why wouldn't u go 235/45/18 to keep the rolling diameter almost the same??

Tires in 235/40R18 are more common and therefore cheaper than tires in the size of 235/45R18. Personally, if you are going to do something, do it right instead of trying to just save yourself some money at the expense of your own safety etc.

so if i was you , i would try and fix/resolve the problem , to stop the speedo going off + incorrect odometer increasing at a faster rate.

Edited June 5, 2012 by simplyvandinh

[andyhui01]

I understand that but isn't it weird that if the rolling diameter is so far off and I assume illegal? the dealer shouldn't have put it on the car in the first place?

Edited June 5, 2012 by andyhui01

[bigVAN]

I understand that but isn't it weird that if the rolling diameter is so far off and I assume illegal? the dealer shouldn't have put it on the car in the first place?

did you buy from a dealership ?

[Boondy]

From what i remember, Toyota sets there speedos to 8% discrepancy.

With those tyres your speedo will be a little more honest now.

[andyhui01]

I did not buy from a dealership but as I said in the first post, I suspect the car had this sized tires fitted from the dealer as the Spare wheel is 235/40/18 as well and from the previous owners original invoice, the car was optioned with Sunroof, Sat-Nav, Tow Bar and 18" Kappa Wheels.

[bigVAN]

I did not buy from a dealership but as I said in the first post, I suspect the car had this sized tires fitted from the dealer as the Spare wheel is 235/40/18 as well and from the previous owners original invoice, the car was optioned with Sunroof, Sat-Nav, Tow Bar and 18" Kappa Wheels.

For real ? Then I'm guessing that it would factory tuned then to the specs of those tyres.

So I assume you are safe in terms of speedo error. So what it displays then most likely is correct if it was an option/extras purchased by the previous owners from a Toyota dealership.

So nothing to worry about I hope

[andyhui01]

I might just test the speedo accuracy with a GPS or iPhone app and report back.

[bigVAN]

I might just test the speedo accuracy with a GPS or iPhone app and report back.

Yeah I was gonna say that , dl the free one on the iPhone pretty accurate I'd say

[Buff Hamster]

The Aurion speedo reading is 5% faster than it should be.

[andyhui01]

ok. So on the Freeway, at 100 on the Speedo, GPS reads 92-93. 100 on the GPS, Speedo reads 108-109.

Is that normal or out of normal?

[Buff Hamster]

Sounds normal to me.

[Boondy]

Oooh yeah. Good test.

Looks good to me.