Speedo Re-calibration

[ozute]

G'day guys,

Someone mentioned to me earlier that if i got some non stock tyres/rims for my VR that I would have to get the speedo recalibrated. I was given the impression that it's just a matter of a techy plugging in to the onboard compa and telling the car the new sized shoes. Is this the case, and does anyone know if it's costly please?

[Macca177]

at a guess, it would only make 2 or 3ks differnce in a commodore. give or take depending on diamatter

but when i had my 4wd i was near 30- 40 k out due to very large tyres(37")
i see ur in syndey, theres a bloke out beverly hills way, he works out the diffencer(dont ask me how) and works out the gears on the cog to correct it.

i never had mien done but my mates have and hes very good. I can try get his number for u if u like.

dont know if its computer controlled on the commodores, if its a senscor or geared for the car to get the speed.


hope this helps a bit
cheers
hayden

[chicb8t]

I changed my stock 15inch wheels for 17 inch rims on my VR and it made no difference at all. just check ure speed agaist a friend in their car when u get the rims if you get parnoid. probably wont be out by enough to bother with

[ozute]

Excellent, sounds good.. Thanks guys

[michaelw]

Am I missing something (most likely) but even in the rims are different sizes the outside of the tyre is still the same isn't it?

I thought it was just the sidewalls were smaller on a 17' vs 15'?

Mike

[ozute]

That's true mate, but sometimes the combinations are not equal to the original dimentions

[semmi]

check out http://www.1010tires.com/TireSizeCalculator.asp - this is a tyre size calculator which allows you to compare different tyre sizes and what the speedo difference will be.

it's a good way to determine if the difference is worth worrying about or not!!

[ozute]

EXCELLENT, just what I was looking for.. Thanks heaps semmi!

[semmi]

cheers mate

[burnz]

i see ur in syndey, theres a bloke out beverly hills way, he works out the diffencer(dont ask me how) and works out the gears on the cog to correct it.




hope this helps a bit
cheers
hayden

dia x pi x rpm keep gearbox in direct not 1,2,o/d x 60 divide diff

[cizocizo]

i got 19's and my speedo is WHACK
surprised i havent got more fines its like 15-20 under

[burnz]

i got 19's and my speedo is WHACK
surprised i havent got more fines its like 15-20 under

(asuming 19 + 60 series = appox 21inch =533.4mm x pi 3.1415 = 1.6756 mtr x (2000 engine) rpm = 3351.2 mtr x (60=mtrh) /3.08 (diff) /1000 =65.283kph

[kopper69]

I dont know if you can calibrate it through the computer, when i was looking at the speedo assembly i dont think it has that sort of setup. I have seen jaycar selling a unit thats meant to correct it, dont know how effective it is. What does the sensor work off anyway? Does it matter in this type of car what the wheel size is at all>>?

[RufusŪ]

Chck this one out http://www.miata.net/garage/tirecalc.html . This will give all the calculations and tell you how far out you are at 100 kph.

Damo

[ozute]

Thanks Damo