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(Speedo check)64 Seconds at 60 MPH

B

boise49ers

NAXJA Forum User
Location
Boise,Idaho
That is what time I turned in one mile at 60 mph. I'm not sure what that calculates too. How many teeth difference do I get to get right on ? 34 to 36 maybe ? Any help would be great.
 
64 seconds/mile = 56.25 mph. Is it off far enough to worry about at that point? What gear do you have in there right now?
 
A 34 tooth. I've been to go Jeeps site and it doesn't calulate even close. It would have me with a 39 tooth and that is 5 teeth off. I'm thinking a 36 tooth.
 
did you measure this using your spedo if so most spedo's are off a little even from the factory so don't coun't on it to be exact. i don't know if gps is even that acurate. and futher more the more websights you check the more (diferent) answers you will get. i guess gps is the best way to measure speed so borrow one from a friend adn check it that way.

as i side note i know for me personally i can't keep my rig at 60 on the button for 1 mile if your off by a mph or so up or down it will throw off your measure.
 
bj-666 said:
did you measure this using your spedo if so most spedo's are off a little even from the factory so don't coun't on it to be exact. i don't know if gps is even that acurate. and futher more the more websights you check the more (diferent) answers you will get. i guess gps is the best way to measure speed so borrow one from a friend adn check it that way.

as i side note i know for me personally i can't keep my rig at 60 on the button for 1 mile if your off by a mph or so up or down it will throw off your measure.
Click to expand...
well, since he's trying to adjust the speedo to be more accurate, using the speedo at 60mph indicated sure seems to make sense. If it was accurate you'd cover the mile in 60 seconds but since it took 64 seconds you know it's off. Barring the use of GPS, how else would you recommend measuring the (in)accuracy of the speedo??
 
Well I paid for a 39 tooth gear before I put on the 33" tires. They put me closer then 5 teeth I know that much. I already paid for a gear so I'm thinking I will just get a 2 tooth difference. Maybe even a one tooth if they have a 35. Less then 4 mph at 60 1 tooth should do it I figure. See I'm one of those impatient guys who jumps the gun 7 out of 10 times on most everything. Genetic's I can't help it. I'm also a bit anal so yes the 4 miles per hour at 60 does bother me. All you can say is thank goodness your not me eh ?
Thanks for your Help though fella's
 
jsut a quick thought... Are you using a mile larker to calcualte your mile, or your odometer? If I had to guess, if most xj's speedos are off a bit then the odometer is too... Just food for thought.
 
Charts are never the same as it depends on the brand, tread, psi and wear of each tyre. I have seen 3/4" difference between different branded tyre in true height even though both had the same size on the side wall. That is why is state that mine is based where possible on BFG tyres!
Now the eaiser for you is to work on percentage. You are reading 6.66% slower and there is a 3% difference per tooth so buy a gear with two less teeth than you have in there now. I do hope you did it with a cruise control on a nice straight flat road for 5-10 miles straight though as just one mile leaves too many varibles.
 
You know what after all this and being even farther out on the charts and closer on the actual speedometer then I expected, I think I will just get my money back on the speedo and call it good. I seen why you said what you did Yuccaman. Ain't worth the aggravation. I'm already tired of it and I just got my tires yesterday. Hey Yucca I seen you were up in Boise. I went to HP and made a little cash trying out a new Fax/printer a couple weeks ago. If you eevr come up this way again shoot me a PM.
See yuh

Thanks for your input though everyone.
 
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You're talking about a 6.67% difference, and the speedo reads slower than your actual speed. To make the speedo read faster, you need LESS teeth on the gear, not more. Get a 32-tooth gear and you should be right on the money.
 
Last edited:
Eagle said:
You're talking about a 6.67% difference, and the speedo reads slower than your actual speed. To make the speedo read faster, you need LESS teeth on the gear, not more. Get a 32-tooth gear and you should be right on the money.
Click to expand...

You're all wrong, He needs bigger tires!!! :D
 
Another way to check is start driving at a mile marker and drive 10 miles or so to get a good average and then look at you odometer and calculate the percent off that it reads from what you know you drove on the road based on the mile markers. You can use that percent difference to figure out how many teeth you need on your gear to be correct (like gojeep was saying) and that way it doesn't matter how fast your driving as long as you start and stop the measurement at the mile markers.
 
Yeah I did figuring after I talked to my local Jeep expert and figure out 32 would put me right on the money. I ordered it and pick it up Monday. Thanks
 
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