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  #1  
Old 01-01-2013, 08:01 PM
Learning to use the forums
 
Join Date: Dec 2012
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Question speedometer read 10% high

Only had my 94 Ranger a few weeks. Notice that speedometer reads about 10% high at all speeds. The Ford garage told me that since my tires are 215/70-14 instead of the stock 225/70-14 that it could cause this error. Anyone know if this might be the cause?
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1994, 3.0L, 4 speed AT, AC, 2wd, extended cab, green, 204k miles, with heavy fiberglass cap and after market trailer hitch
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  #2  
Old 01-01-2013, 08:03 PM
Scrambles the DeathDealer
 
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Default Re: speedometer read 10% high

Yes
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  #3  
Old 01-01-2013, 08:27 PM
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Default Re: speedometer read 10% high

Even with stock tires, it will read about 2 mph high. I clocked my '98 with a GPS several times to confirm this.
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  #4  
Old 01-01-2013, 08:33 PM
Ford Ranger Driver
 
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Default Re: speedometer read 10% high

I know from this site that some say "All Ford's speedometers register off", but I can't remember if it is faster or slower than the speed it shows. I know that speedometers can't be 100% accurate, so 2 mph doesn't seem bad. I have GPS and I tested my speed once, and it looked right-on.
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  #5  
Old 01-01-2013, 08:37 PM
Tank Diver
 
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Default Re: speedometer read 10% high

Quote:
Originally Posted by fifthranger View Post
I know from this site that some say "All Ford's speedometers register off", but I can't remember if it is faster or slower than the speed it shows. I know that speedometers can't be 100% accurate, so 2 mph doesn't seem bad. I have GPS and I tested my speed once, and it looked right-on.
No argument here. Both trucks read about 2 mph fast. The CR-V was 3 mph fast before I stepped up from the stock 205/70/R15 to 215/75R15 tires. Now it is dead on.

There was a magazine article a few years back covering this. It seems most vehicle manufacturers are allowed a certain percentage of leeway on speedometer accuracy. Most opt to have their speedometers read fast. For legal reasons I think.
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2011 Ranger XLT, 4X4, 4 door Super Cab. 4.0L, 5 Speed M50D-R1HD, 3.73:1, 8.8" open differential, Jason Pace cap
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  #6  
Old 01-01-2013, 08:50 PM
Surrender isn't an option
 
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Default Re: speedometer read 10% high

I know it from a toyota site but it still works for all mfg's
http://www.tacomaworld.com/forum/tir...0r14-225-70r14
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  #7  
Old 01-01-2013, 08:54 PM
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Default Re: speedometer read 10% high

Quote:
Originally Posted by sgtsandman View Post
No argument here. Both trucks read about 2 mph fast. The CR-V was 3 mph fast before I stepped up from the stock 205/70/R15 to 215/75R15 tires. Now it is dead on.

There was a magazine article a few years back covering this. It seems most vehicle manufacturers are allowed a certain percentage of leeway on speedometer accuracy. Most opt to have their speedometers read fast. For legal reasons I think.
I know that odometers can be off also, and evidently it is common knowledge that speedometers can be inaccurate also. But, if that is the case, why do some say, "Ford's are more prone to be off" since manufacturers buy from other companies. So, a Ford speedometer, for example, can be manufactured by any number of suppliers.
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  #8  
Old 01-01-2013, 09:14 PM
Learning to use the forums
 
Join Date: Dec 2012
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Default Re: speedometer read 10% high

wow great web site calculator. But it looks like my tire size difference can only account for about a 2% over-reading on my speedometer. So I must have something else wrong too.
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1994, 3.0L, 4 speed AT, AC, 2wd, extended cab, green, 204k miles, with heavy fiberglass cap and after market trailer hitch
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