calibration of speedo

[andy t]

I am thinking of changing my wheels from the standard mk 3s-14" with 185 60 14 to 17"with 205 40 17 tyres.( a friend is selling a set).
I wondered if i will need my speedo recalibrated. what is involved in the process and where would I need to go to get this done . I live on the sydneys northern beaches so somewhere close would be great.
thanks.

[Golf Houso]

There should be no real difference in the speedo, a few people on here have mk3's on 17's such as Bboyskidz and Bombaquad, and they never complained about inaccurate speedo readings. I myself have a GL with 16's and there is no difference at all in the speedo reading.

Hope that helps!

[JustCruisn]

Your speedo will be out by +3.2%. You will be going faster than the speedo says.
If you speedo is like mine it reads faster than reality anyway.

205/35/17 might be a more correct tyre choice only out by -0.08% you'll be going a tad slower that the speedo value.

http://www.rims-n-tires.com/rt_specs.jsp
or
http://www.carbibles.com/tyre_bible_pg2.html

17inch tyres cost a lot more than 14inch too

[andy t]

the wheels i have been offered have got tyres with a good amount of tread so not worried just yet . more worried about buzzing speed cameras.

[rayray086]

There's no real need to recalibrate the speedo mate. I think it's a lot of hassle for a small and easy change. As JustCruisn helped point out, you'll be going 3.2% faster than your speedo - if it says 100km/h, it would show 103.2km/h on your 14's with 185/60 tyres. Note that I didn't say your actual speed - our speedos aren't exactly accurate anyway, and quoting websites, they could be up to 5% off from your actual speed from the factory. BTW, I don't think there's a 205/35 in 17" readily available, and would be a considerable price hike from a 205/40. My guess anyway - same goes when I was looking for 195/45R15 as opposed to 195/50R15.

If you're worried about speed cameras, just drive 55 in a 60, 35 in a 40 etc.

[andy t]

3.2% isnt very much i guess(I just hope my speeedo isnt 5% over already making it 8.2%!)
i will see if they fit before i buy. fingers crossed.

[Oneofthegreats]

Speedo's alway's run faster than there suppose to, as it's part of ADR's & is allowed to be upto 10% out, but only faster. It doesn't comply if the speedo run's slower!

I think you may find that with fitting those size wheel's, the speedo may end up being 100% accurate.

The overall height increase of you tyre is less than 3/4". It won't make that much of a difference I don't reckon.

[The_Hawk]

If you don't have your own, beg, borrow or steal a GPS and see what it says your real speed is after you put the wheels on. You can calculate what the difference is going to be, but unless you know how accurate your speedo currently is it's not going to be much help.

In my case, I'm running 205/40/R16 and my speedo is *just* and I mean *just* under being 100% correct. The down side to that is that in the wifes car you can cruise at an indicated 120 in a 110 zone and never worry since in reality your closer to 110, but you get to feel good about "speeding"
In the dub I have to remember that when I'm indicating 120 I'm really doing 120

So yeah, get a GPS and check what your final result will is.

[bboyskidz]

I think you may find that with fitting those size wheel's, the speedo may end up being 100% accurate.

yeh its true. I have the exact same setup you are proposing and the speedo is now spot on (I checked with GPS like Aaron suggested).

I have 17" wheels with 205/40/17 tyres and it is sweet. My wheels are 7" wide and with the 205s on it looks crap. next set will be 195/40/17. with the stretch, it will be closer to the original and back to the 'slower' speedo reading.

you probably only need to start worrying about the speedo reading if you are getting 18s or larger. I've always thought a set of those 20 spoke Audi 18 inch rims would look sweet on a mk3. ride could be a bit rought though - lol.