Rim Question

[rancheeto]

i just put 175/65/14's on mine and had a little rubbing, but my wheels were 6" wide. a few spacers took care of that problem. i recently drove from the florida panhandle to southern illinois and got pulled over for doing 83 in a 65. i swear though that my speedometer said 70-75 mph. the cop didnt even give me a chance, just a ticket. so checking your speed with someone else might be a good idea before goin too far on bigger tires.

[MONSOON]

According to this tire calculator.

http://www.miata.net/garage/tirecalc.html

I used 165/70R12 as the stock tire.

With the tires youre using, your speedometer is reading fast compared to what youre actually doing.

[rancheeto]

According to this tire calculator.

http://www.miata.net/garage/tirecalc.html

I used 165/70R12 as the stock tire.

With the tires youre using, your speedometer is reading fast compared to what youre actually doing.

so your sayin that if my speedometer is reading 65, i am actually going slower

[MONSOON]

According to that and a couple other tire calculators out there yes.

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

According to this one. If your speedometer says 60 youre actually doing 55

[econoaddict]

going from a 155r12 to the 175/65r14 should make your speedo read approx 3.5-4 miles an hour SLOWER than you are actually traveling.

Taller than stock = speedo reading lower than actual speed.
Shorter than stock = speedo reading faster than actual speed.

[kyle13]

ok, thanks for all the help.

[rancheeto]

weird

[Safety Guy]

Econoaddict is right. Taller tires will read a slower speed than you are actually driving.

Here is a short list in approximate order of height:

195/45-14 the Proxes tire in this size is considered the standard for high performance on 14" rims and is slightly shorter than stock.

These are stock heights, the first two being factory supplied:
165/70-12
145/80-12
175/60-13

155/80-12 slightly taller, but a standard replacement until they all disappear!

165/70-13 about 4 percent difference (add 4% to get your actual speed or mileage)

185/60-13 I think this size is slightly taller than the one before. Should work well.

145/80-13 This would be an excellent size for fuel economy with lightweight 13" wheels due to the thin profile for lower friction.

These two are about 7.4 percent different (add at least 7 percent). These sizes are the smallest now widely available:
155/80-13
175/70-13

185/60-14 this stock Miata height is quite tall for a Festiva, but some report it works for them on unlowered cars.

Is someone requests it, I can copy my ride height chart and post it. It gives you mathematically correct (may be slightly different in reality) ride heights for many tire sizes.

Karl

[MONSOON]

That would be awesome! Because I often wonder what would be OK replacements for say the 195/45-14 which is almost dead on for the 12s. I personally dont mind if the speedo is off a little bit as long as I know what that little bit will be.

[econoaddict]

Handy link for comparing tire measurements.

http://www.miata.net/garage/tirecalc.html

[MONSOON]

Yaeh Id forgotten about that one.

[Safety Guy]

I'll try to remember to find and post my little chart in the morning.

However, within wheel diameter size, here is how you figure height out:

145/80-12

145mm
times
80 percent, or,

145 X .80 = 116.0mm tall sidewall.

Compare this with the other stock size, 165/70-12:

165mm
times
70 percent, or,

165 X .80 = 115.5mm tall sidewall.

So both stock tires are (theoretically) within half a millimeter of each other in height.

To compare these with 13" tire sizes, you'd have to add the wheel radius (not diameter, since we're figuring only one half of the round thingy) to the tire sidewall height.

12" wheels = 6" radius, or 152.4mm (15.24cm).

13" wheels = 6.5" radius, or 165.1mm (16.51cm).

14" wheels = 7" radius, or 177.8mm (17.78cm).

Now go figure!!

For easier tire heights, sometimes tire manufacturer and sales websites list those in charts along with other technical data like speed and heat ratings, weight, etc.

Karl

[Safety Guy]

Okay, let's see if this copies from my documents:

FESTIVA TIRE HEIGHT COMPARISON CHART

TIRE SIZE OD (mm) + or – stock height (mm)

175/50-13 505* -17
165/55-13 512 -12
195/45-14 531* -3
165/70-12 536* --
145/80-12--------------537* -------------FESTIVA STOCK HEIGHT---------------
175/60-13 540 +2
165/65-13 544 +4
185/45-15 547 +5
155/70-13 548 +5
195/50-14 551* +7
185/60-13 552 +7
155/80-12 553 +8
195/45-15 557 +10
185/55-14 560 +12
165/70-13 562 ( ASPIRE STOCK HEIGHT) +13
145/80-13 562 +13
195/60-13 564* +14
175/60-14 566 +15
165/65-14 570 +17
175/70-13 576 +20
195/50-15 577 +21
155/80-13 578 +21
185/60-14 578 +21
175/65-14 584 +24
185/55-15 585 +24
165/80-13 594 +29
195/55-15 595 +30


Looks like it did!

If anyone finds any mistakes, please let us know!

Karl

[Cowboy]

I bought a 90 Festy with OZ Rims and 195/50/15 Tires
They have spacers behind the wheels,but scrape the front fenders when entering a parking lot or going over a speed bump.... as inside a trailer park. ( I deliver food with this Festy )
I would like to put 13 inch or maybe 14 inch rims on it...
The 12in tires are hard to find not to mention the rims...
Can you help ???
Thanks !!!!
I am in Toledo OH area...
Eric

[MONSOON]

All youve got to do is a little reading and you'll find the answer. Try the sticky its got a ton of info.
Oh and BTW.