Speedo correction, K's off????

guyph_01 · Post by **guyph_01** » Sun Sep 06, 2009 11:47 pm

hi guys,

Here is what i have noticed and i was thinking if there were anything that could be done etc.

I used to get 1L to 10k's with my EJ22 in my touring wagon when i had 14" on with 185/65/14 or similar. I used to do around 380-410 km's on a tank( 40lts).

But since i got my 15" with 225/65/15 and i now have only 300-350 with a full tank (40lts). Also when the speedo is at 85, im actually doing 100.

I had issues with my speedo cable beeing to short, and with the wreakers wanting $50 for a brumby one i bought an aftermarket one for $10 from repco and made it work.

Now could it be the speedo cable thats wrong? Making me think that the car is doing less k's etc? Or is it the tyres thats causing this?

Any ideas or explainations on what could be happening would be greatfull.

thx

AndrewT · Post by **AndrewT** » Mon Sep 07, 2009 12:38 am

Yeah, bigger diameter tyres means they have to turn less to move your car the same distance. You cover more distance per turn of the wheel so end up going faster than your speedo reads. The advantage is your milage will clock up less than your actual milage

If you are keen enough to get it accurate then this is what you need;

AndrewT wrote: Vidler/Lapsed old L series wagon had one of these mods.

"Mechanical speedo cable ratio corrector boxes"

This is what I mean....
http://www.gaugeguys.com/ratioadapt.htm

Here's a place in Australia that does them...
http://www.marks4wd.com/products/tyre_m ... ction.html

That was the first thread that came up on a seach for "speedo correction"

GOD · Post by **GOD** » Mon Sep 07, 2009 2:04 am

^ What he said.

And it's interesting to note that after correcting for your 17% speedo error, fuel consumption has increased from about 10.1 l/100km to 10.9 l/100km. That'll be from monster truck tyres and having all the running gear dangling in the breeze below the car - notch up another point for little tyres and no lift

.

Dane.

AlpineRaven · Post by **AlpineRaven** » Mon Sep 07, 2009 7:37 am

Its a mind confusing thing!
You should be going further with larger diameter tyres, its not the speedo cable causing error, its in the gearbox there is a speedo wheel in it that gives the speedo reading, you need to change that, that involves splitting the gearbox. There are some conversion kits out there but I dunno if it'll fit in Subaru.
Cheers
AP

AndrewT · Post by **AndrewT** » Mon Sep 07, 2009 8:09 am

yes but isn't it way easier to just modify the speedo cable? It corrects the speedo reading, which fixes the problem.

tex · Post by **tex** » Mon Sep 07, 2009 10:58 am

AndrewT wrote:yes but isn't it way easier to just modify the speedo cable? It corrects the speedo reading, which fixes the problem.

How?

Pity its not like other cars where the little plastic cog is on the end of the cable so you just slid off the old one and slid on the new correct one!

AndrewT · Post by **AndrewT** » Mon Sep 07, 2009 4:49 pm

tex wrote:How?

Pity its not like other cars where the little plastic cog is on the end of the cable so you just slid off the old one and slid on the new correct one!

Scroll up to the first part of the thread where I explained it. I've seen it done, it's mega simple.

phillatdarwin · Post by **phillatdarwin** » Mon Sep 07, 2009 10:35 pm

Singapore has them for there cars when u put bigger wheels/tires on as the speeding fines are big over

Post by **TOONGA** » Wed Sep 09, 2009 9:16 am

why dont you just modify your dash or speedo so that 85km/h shows as 100km/h like we did years ago when speedos when from mph to kmph

some little stickers will fix the problem

TOONGA

guyph_01 · Post by **guyph_01** » Wed Sep 09, 2009 10:52 am

yes but the k's the car is doing will still be off... Be better to fix both with that little correction box. Well for now im planning to go with a 5stud conversion so i'll do that after i settle on a set of mags. Also my 15" 4 studs will be for sale at some point:)

Subyroo · Post by **Subyroo** » Wed Sep 09, 2009 12:45 pm

Why don't you ringthese guysand see if they can do anything for you.

steptoe · Post by **steptoe** » Wed Sep 09, 2009 2:33 pm

If the standard factory fit tyre for L and MY was 175/70- 13 it has a nominal overall tyre diameter of 576mm.

175/70-13.........576mm
185/65-14.........596mm
225/65-15.........673mm

I always found my speedo to be gps spot on with 185/65 - 14

Is your concern of having an accurate speedo to look at (try G220 or G200 at ww.nextdestination.com.au ) or odometer to measure fuel

Willie · Post by **Willie** » Wed Sep 09, 2009 3:37 pm

Have a look here:
http://www.miata.net/garage/tirecalc.html