315?75R16,s without gear change ?

[cruiser99]

Sorry I did not make myself clear.

Yes Jim you figures and logic are the same as mine. The bottom line is that the mileage went down (became worse) AFTER correcting for the odometer error due to tire diameter increase. Or¡K, calculating mileage with the GPS odometer, that is actually more accurate then any speedometer that Toyota can come up with. (Especially when the GPS receiver tracks 4 satellites. After I got the antenna outside of the vehicle I routinely get al least 8)

And yes, 12.5% is correct if you do the nominal change in diameter. As far as distance traveled, I am getting a little less then that (12.1%)

The funny thing is that the difference before the 315 and after is larger when the truck is loaded up. ~1MPG unloaded and ~2 loaded.

Here in the US the truck came with 275/70-16

Oh, for the sake of confusing things some more ļ I have one more thing. I have 2 fuel tanks on this truck. The 2 fill necks come together into a Y right at the cap. The only thing that prevents the gas from flowing from one tank to the other is gravity. I guess there is a possibility that gas can transfer between that tanks when the truck is at an incline (transfer from front tank to back tank) or decline (transfer from back tank to front tank). I doubt it but it is possible when the tanks are full. This will introduce another error to the measurement.

Doron.

 

[Junk]

Whelp, you can lead a horse to water, but you can't turn him into glue till he bites it, so.... get the 315's, put them on with your blower then post back in about 4 months asking what's involved with going to 4.56's. :-/

You'll be back.

 

[landtank]

That would be 4.88s when you regear

 

[MTNRAT]

ok,ok,ok. I am going with the 315's. They will be here on wednesday . Oh by the way what is involved in regearing .
PS. I have the speedo correction gear already, but that almost fixes the speedo for 285's, so you guys figure I may want a truespeed to calibrate for the 315's.
Sean

 

[Photoman]

Unless you regear to 4.56. This ratio will put you back to the stock speedo ratio. If you don't regear then you will need the recalibrator.
Bill

 

[landtank]

Great Choice with the 315s . I installed the truespeed on my truck. It is fully adjustable and has two settings in case you run two sets of tires. This will help with shifts in the tranny and such. Don't follow their instructions on install as they want you to cut into the harness at the sensor. Instead go to Christo's site in the tech zone. He has a bastardised 8) version of what I did. The modulator will velcro up inside the front dash on top of the heater core very nicely.
The modulator will also come in handy when you go with those 4.88s as instead of having a slow speedo it will be a little fast.

 

[MTNRAT]

Thanks photoman and landtank. I guess I better get on the phone again to slee offroad. I tried to find a dealer for truspeed up here in Canada, but the dealers listed on their website don't carry it ???.
Sean