35" tires affecting speedometer, odometer too?

[jordanblea]

Hey guys I posted this question on the 67-72 pickup trucks board but figure the blazer/jimmy guys might be more familiar with a lifted truck question lol.
Hey guys not sure if this is a stupid question or not. I have been keeping a log of how many miles I cover vs how much gas I buy to try and get a ballpark number on mpgs. My question is this, with 35" tires my speedometer is off, says I'm going 50 when im going 61-62 mph, which is ok I can deal with that, but will that also throw off what my odometer is reading? Like if it says I went 40 miles, but really went 50? That'd be nice....Anyways, thanks!

[DeadheadNM]

You are correct, seeing less revolutions so reduced miles on the odometer - see what the odo does between mile markers on Hwy 44 (550). I was ticketed in my old 71 Blazer outside Bloomfield because I speeding despite my odometer reading

[jordanblea]

Originally Posted by DeadheadNM

You are correct, seeing less revolutions so reduced miles on the odometer - see what the odo does between mile markers on Hwy 44 (550). I was ticketed in my old 71 Blazer outside Bloomfield because I speeding despite my odometer reading

Bloomfield, New Mexico? lol With your name sounds like you've been in the area, now in Montana? Anyways, so reduced miles on the odometer=more miles traveled than what it is reading? A fella on the other thread said this:

LESS.
That is, with a "slow" speedometer, your odometer will also count more slowly. Good news is if your tires have a warranty, you're getting better warranty coverage.
Three possibilities:
1] At a speedo shop run on the dynomometer and clock your indicated speed against your revolutions of their rollers and get a graph to post on your dash. So you know that, let's say, 47 indicated is really 55 actual MPH. Callibrations from 10 thru 90 on the top scale, and actual reading numbers on the lower scale.
2] With the above knowledge, some shops can build a compensator box [they're about 1" x 2"x 3"] that goes between your speedo cable and the transmission. Borg-Warner used to make them. With this gizmo, you're cured. Your ODO will read good. [Within 1 - 2.5%, or so]. I happenned to get lucky, once. I had an old comp box - came with a junkyard SM465. It read all wrong, but I kept it anyway. Some years later when I switched from R8x17.5LTs to R235/85-16LTs, I tried it on for laffs. I was amazed, when it matched my GPS speeds within 2-3 MPH. So if you find the little box keep it. A speedo shop can change the internal gears or you.
3] Get a GPS, set it on MPH, and read that when driving. No odometer support however, but it's way accurate.
You could also get a helper to record your speeds, matching indicated marks with actual GPS readings, and make up your own calibration curve chart -- without going to a speedo shop -- like I had to do in the '80s.
Good luck.
Hope this helps.

[DeadheadNM]

Yep - grew up in New Mexico now in Montana. Well, in ABQ at the moment - just finished some red chile chicken enchiladas for lunch with a Marble IPA

[jordanblea]

Originally Posted by DeadheadNM

Yep - grew up in New Mexico now in Montana. Well, in ABQ at the moment - just finished some red chile chicken enchiladas for lunch with a Marble IPA

My pop lives up in Couer D' Alene, ID, been to Kalispell before. They used to do an awesome soft ball tournament that they'd go to, nice pretty town. We just opened up a new BBQ restaurant in Bloomfield right where 550 T's into Bloomfield, stop in and say hey if you're driving home. It's a long drive all the way to Montana, done it several times lol. Anyways I tend to agree with you on the mpg's, if it's reading slow it'll tick slow as well, I'd like to think anyways.

[DeadheadNM]

Hey Thanks! I'll look for the restaurant next time I'm passing through (flying home this time) as BBQ is a love of mine. Good luck with the restaurant! Pete

[jordanblea]

Originally Posted by DeadheadNM

Hey Thanks! I'll look for the restaurant next time I'm passing through (flying home this time) as BBQ is a love of mine. Good luck with the restaurant! Pete

That other guy replied back, and I misunderstood what he meant by "LESS" lol, he meant less ticking on the ododmeter, not mpgs.

serioustexasbbq.com is the shop, just opened last year here in Bloomfield. We started in Durango and this is now our 6th location.

Thanks for your help, safe travels!!

Jordan

[Chulisohombre]

When I Stepped up to 3/4 ton axles I found 4.10 geared 1 ton rear and regeard my front to Match from 3.73. Now it is Fairly Close to stock. Not the cheapest option but I was breaking the axles To Often to Leave them 1/2 ton. Only cost Me 300 bucks in junkyard parts and then I added disk Brakes For another 300.

[AHowe88]

For what is worth you can correct it with something like this:
http://www.ecklerstrucks.com/chevy-t...1955-1972.html

That is a custom one, but you can get preset % adjustments.

[jordanblea]

Originally Posted by AHowe88

For what is worth you can correct it with something like this:
http://www.ecklerstrucks.com/chevy-t...1955-1972.html

That is a custom one, but you can get preset % adjustments.

Sweet, I wonder if its only for when its re-geared, or if it takes into account tire size as well?

[jordanblea]

I called the site he said it works for larger tires too.

[rwhite692]

Slightly off topic but if you need a quick way to calibrate / check the accuracy of your truck's speedo, you can download a free app for your smartphone which utilizes the phone's GPS (just search "speedometer") - it is dead nuts accurate (I have checked it vs. two of my daily driver cars).