Tire Size. [Archive] - Duramax Diesels Forum

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Durasizzle
04-14-2009, 03:42 PM
i got a PPE hot +2 about a month ago and before that i had a hypertech in my truck. Now i put the tire size to 34.75" (my toyo's are 34.8") and the gear ratio to 3.73 but my speedo is still 10 km/h off.

should i just adjust till it gets correct on my speedo? i was using a Garmin Nuvi GPS to test against.

The Neens
04-14-2009, 03:57 PM
Is the GPS reading faster or slower than the speedo?

DmaxHawk
04-14-2009, 04:08 PM
Tire sizes are not entirely accurate. What I did is use my GPS until its perfect.

Durasizzle
04-14-2009, 04:19 PM
the GPS says that my speedo is 10 km/h faster

ex speedo says 100km/h, GPS says 90 km/h

i never had a problem with my hypertech though :confused:

The Neens
04-14-2009, 04:50 PM
Try dropping the tire size a bit and see how it changes the difference in readings you're getting...Not sure why the Hypertech was accurate and now the PPE isn't...

Durasizzle
04-14-2009, 11:10 PM
ill do that tomorrow and report back

Durasizzle
04-15-2009, 12:22 PM
actually it was the other way around my speedo says 90 but the GPS says 100.

But i tried changing the tire sizes, to 33, 31 and still didnt change anything.

The Neens
04-15-2009, 12:41 PM
If speedo is reading low, you have to enter a bigger value with the PPE programmer...

McRat
04-15-2009, 01:06 PM
Be aware that when you go past 35" dia, most trucks will throw ABS light. You can only reprogram the ABS with a Tech2 dealer tool.

Durasizzle
04-15-2009, 04:17 PM
well i tried going up to 36" and it still doesnt do anything, even went to the dealer and had them reflash my ecm and then tried that but still no luck.

Could there be a problem with my Tuner?

The Neens
04-15-2009, 07:40 PM
well i tried going up to 36" and it still doesnt do anything, even went to the dealer and had them reflash my ecm and then tried that but still no luck.

Could there be a problem with my Tuner?

I would give PPE a call tomorrow...

KEVINL
04-15-2009, 07:52 PM
32.75 will make the speedometer correct don't ask me why they cant get that right

Durasizzle
04-15-2009, 08:03 PM
so put the gears to 3.73 and tire size to 32.75?

ill try and see if that works.