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Discussion Starter · #1 ·
well guys i found one of 3 very helpful tire size calculators....im sure it has been posted before but here goes again for people like me looking to go bigger and see what changes will be made to the ride specs.....

I posted another one a while ago and tells you what gears to recalibrate when changing tires but that was a lil while ago...

enjoy

http://www.1010tires.com/TireSizeCalculator.asp?action=submit
 

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Original owner, 1983 P'up LS (diesel)
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And once you find how much speedometer correction you need, how do you correct it? If it's a mechanical, cable-driven speedometer, this is what you need:

I bought mine from PACTRANS (an eBay seller) because they happened to have the correct ratio listed. This is listed for GM transmissions, but it fit my P'up perfectly. But if they don't have what you need, they will gladly make one for you...
We do make customs ratios for customers. The + 5% is $72.00 plus shipping and handling. Know their is a 4-6 week wait since it has to be customly made. If you have any other questions please don't hesitate to contact us again.
PATC

- patctrans
They were a pleasure to do business with. Hope that helps someone.

Jack
 

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Hey Jack, that's pretty cool!

I have a word problem for you guys on this topic.

My Rodeo had 4:10 gears, 245-70-16 tires from the factory.

Larger tires (31") with the factory gears had my speedo off about 5 mph too slow.

I then switched to 4:56 gears and still larger tires (32") and my speedo was 5 mph too fast.

The factory speedo gear was 17 teeth so I switched it. I tied a 16 and 20 tooth gear. When I put in a 16 tooth and it was 10mp too fast. The 20 tooth gear put me back to 5 mph too slow again. I'm thinking an 18 or 19 tooth gear will do the trick but maybe this device will be better?
 

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You lost me, too many words. Break it down to pure math. Speedometers are not off in mph, they're off in %ages. The mph of error varies across the range of speed.

I'll take a look at this after my brain has rested, and I'll see if I can calculate what % yoiu need to adjust.

Edit: Rather than a series of math problems to get to where you are now, let's just start where you are now. Do you have a GPS nav device? Choose the speed you want to calibrate at. Speedometers don't have all the numbers positioned consistently, so it can be dead-on at one speed, yet off at another speed. For that reason, it might be best to calibrate against your odometer, but usually it's not far enough off to matter.

In my P'up, it's reading about 38 when the GPS is on 40. But at 75, it's now perfect per the GPS. Who knows, at 100, it would probably read 85 (because it only goes to 85 :lol:), but I digress.

If you want it right at say, 60, then drive 60 per the GPS. Record what your speedometer says, and calculate the % of speedometer increase or decrease you want to achieve. Then order that ratio.

Jack
 

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Very cool.

I am running 265/70R16 on my stock rims. Is brake failure a real issue? 1010 tires pops up there warning.
 

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Discussion Starter · #9 ·
turtleguy12 said:
Very cool.

I am running 265/70R16 on my stock rims. Is brake failure a real issue? 1010 tires pops up there warning.
Its prob just a generic warning....if there was an aftermarket oversized bake kit id own one just to be safe...but i dont think youll have issue,...

you can always get slotted rotors and some ebc green pads along with some stainless brake lines to try to get the most of your setup....is it necessary?...prob not.....
 

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Crash said:
turtleguy12 said:
Very cool.

I am running 265/70R16 on my stock rims. Is brake failure a real issue? 1010 tires pops up there warning.
Its prob just a generic warning....if there was an aftermarket oversized bake kit id own one just to be safe...but i dont think youll have issue,...

you can always get slotted rotors and some ebc green pads along with some stainless brake lines to try to get the most of your setup....is it necessary?...prob not.....
You forgot the brake fluid....
 
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