is there a way to recalibrate the speedometer for bigger tires??

i have a 97 ob. thanks in advance

Hi funkyfish77 and welcome! Summit racing has some devices to do that for fords and chevy's but I don't know if they have them for Subaru's. These little boxes basically take the signal from the VSS and output it's own signal at some (usually adjustable) percentage of the incoming frequency. Another option might be an aftermarket speedo that is adjustable.

The amount of error in your speedo won't increase that much if you change your tire height.

The amount of error in your speedo won't increase that much if you change your tire height.

 

Yeah it will, ask the cop that gave me an 85 in a 60, my speedo said 55

noone can answer your question until you provide more info. are you getting taller tires for snow tires that are a tiny bit bigger or are you offroading with 35" super swampers? big difference and totally different answers. speedometers are easily a few percent off anyway, so a small deviation in tire height might not matter.

 

there are online tire size calcluators, just type in "tire size calculator" on yahoo and click one. compare tire sizes and see how far off your speedo is off.

85 in a 60, my speedo said 55

a wild guess, but i don't think he's looking for a %50+ increase with 305 80 16's.

Yeah it will, ask the cop that gave me an 85 in a 60, my speedo said 55

From stock, the speedo reads faster than you're actually going. So, unless he's jumping to huge tires, I doubt the change is going to be that substantial.

Originally Posted by Manarius

The amount of error in your speedo won't increase that much if you change your tire height.

 

 

Yeah it will, ask the cop that gave me an 85 in a 60, my speedo said 55

 

How big of tires are you running! There's no way you got 30 mph difference form changing to taller tires. I don't believe that for a second. I changed from I think 28" tires to 31" tires on my truck and the difference is like 5 mph at around 70mph or something like that I can't remember.

How big of tires are you running! There's no way you got 30 mph difference form changing to taller tires. I don't believe that for a second. I changed from I think 28" tires to 31" tires on my truck and the difference is like 5 mph at around 70mph or something like that I can't remember.

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i second that. Even if you do the math you'll find out you had to have a HUGE tire size change, to the point where you need a lift kit.

 

nipper

there are members running lift kits and i don't know what size tires, but they are huge on some of their rigs. upgrading a truck tire from 28 to 30 is no big deal, going from a dinky stock sized subaru wheel to a very large off road truck tire is a much larger jump.

 

but i don't think the original poster is interested in these kinds of mods, he can clarify if i'm wrong.

From stock, the speedo reads faster than you're actually going. So, unless he's jumping to huge tires, I doubt the change is going to be that substantial.

This is totally wrong. Even a small tire change can change your speedo by 10mph.

 

Here is a great web page for changes

 

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

This is totally wrong. Even a small tire change can change your speedo by 10mph.

 

Here is a great web page for changes

 

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

90-94 Legacy stock rim sizes make the speedo read 10% fast. Jumping to 16in rims makes the speedo run ~accurate.

90-94 Legacy stock rim sizes make the speedo read 10% fast. Jumping to 16in rims makes the speedo run ~accurate.

Where is this information from?

I have stock 14inchers on my 91 and I have checked my speedo with my navigation system and the speedo is dead on.

The speedo will be off by the ratio of the circumferences or diameters or radii (since the circumference is a linear relationship to the radius or diameter). So for example if you to 27" diameter tires from 26" diameter tires the ratio is 27/26=103.85%, so if you're speedo says 55mph (and is accurate) then you're actually going about 57mph.

Where is this information from?

I have stock 14inchers on my 91 and I have checked my speedo with my navigation system and the speedo is dead on.

General observation from those of us on the bbs.

 

http://bbs.legacycentral.org/viewtopic.php?t=25626&highlight=speedo+wrong

http://bbs.legacycentral.org/viewtopic.php?t=22740&highlight=speedo

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i second that. Even if you do the math you'll find out you had to have a HUGE tire size change, to the point where you need a lift kit.

 

nipper

 

I do have a lift kit, and going from 175/60R13's to 28" swampers my speedo is way off.

How big of tires are you running! There's no way you got 30 mph difference form changing to taller tires. I don't believe that for a second. I changed from I think 28" tires to 31" tires on my truck and the difference is like 5 mph at around 70mph or something like that I can't remember.

 

Explain why my spedo read 75 when my GPS was saying 97mph?

 

P185/75 to 30x9.5 mudders

Provided the the speedo (75mph) and gps readings (97mph) are accurate, if the new tires are 30" dia the original tires must've been about 23.2" dia?

General observation from those of us on the bbs.

 

http://bbs.legacycentral.org/viewtopic.php?t=25626&highlight=speedo+wrong

http://bbs.legacycentral.org/viewtopic.php?t=22740&highlight=speedo

Cool thanks for the info on this!

Unless you have body work or a tall lift kit, there's no way you'll fit tires that would affect it by more than 5% or so. Even then, when you account for the fact that the stock setup reads too high, it may in fact be more accurate.

 

^^^ 97 OB with 205/75/15 AT's, speedo is accurate. Not much more room in wheel wells for bigger tires if you want to do things like go over bumps, through dips, or turn your steering wheel.

 

Steve

i will probly go with a 27" tire not much big than stock. thanks for all the reply's

i never thought i would get so many reply's on this subject.