Hey,

I am currently runnin a set of P185/75 R14's
If I throw on a set of P185/60 R14's, will that change of 15 millimters in sidewall height throw my speedometer / odometer readings way off? If it does, it will icreace everything rite?

Thnx

That number is the aspect ratio (height to width), i.e. 60% of 185 and 75% of 185 which calculates out to a change of 28 mm in height.

I would NOT do this. In fact, in my country it wouldn't be legal, as it deviates by more than 5% from the manuf. standard.

Your present 185/75/14 tires have a circumference of 1989 mm. Compared to the 1814 mm of the 185/60/14 tires, there is a -8.8% difference. So when your speedometer reads 70 mph, you will actually be travelling at 63.9 mph (assuming that your speedo is accurate).

A 60 profile tire on a 14" rim would have to be 225 mm wide to match the circumference of your present tires. Tires this fat will not fit in the 240's wheel wells.

Source: The Wheel and Tyre Bible (excellent calculator, scroll down): http://www.chris-longhurst.com/carbibles/tyre_bible.html

Erling.
--
My 240 Page

hrm
ok thnx...
i am not really concerned with my speedo being off cause half the time it never works lol
but if i wanted to shove a wider tire on, that means i need a wider rim rite?
IE = going to a 195 would that fit in a wheel well and stock rim? thnx again

I have run 205/70-14 on the rears for years. Never a rubbing problem. Speedo is a little off. Haven't tried them on the fronts. I pulled them from a non-op 240 because my 1986 was losing ground clearance in back - next fix must be new bushings.

Check the sticker on the rear edge of the RF door to see what the factory size is. A 185/80 (a 185/nothing-R14) is close to a 195/75-R14 is close to a 205/70-R14.

Use that tire calculater and put in your stock tire size. Then you can determine what other sizes can work. I think that the 205/70 is the widest aspect ratio that will safely clear the wheel wells. Next up would be a 215/65 and then a 225/55. I would not try those two.

Regards,

Bob

;>)

that depends on your rim. you won't need a wider rim most likely. the stock rims (at least on my 740) can take at least a 195 and i hear you might even be able to do 215 with a little bit of rubbing.
--
Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

There's a great tire size calculator online here:
Tire Diameter Calculator
http://www.miata.net/garage/tirecalc.html

It will tell you how much your speedometer will be off.

By the way, 240 sedans are supposed to have a 185/70R14, and the wagons came with 185R14 which is an "80" series tire. A 195/75R14 is often substituted on the wagons, although you can find 185R14 tires from a few manufacturers still.
--
Rob Bareiss, New London CT ::: '86 244DL- 215K, 87 244DL- 230K, 88 744GLE- 198K, 91 244 180K

Compared to the 185/70 standard tire mentioned by Aye Roll, your current 185/75's are 3% greater in diameter (therefore, circumference), so if the car speedometer was perfectly accurate with the factory tires, you are now reading 3% below actual speed and distance....no big deal. The 185/60's are much smaller and would have your speedo reading about 6% high to actual (ie: 9% different than the 185/75's as Erling said). If you are happy with the speedo accuracy and engine RPM's on the highway with your current tires, you can use 195/70-14 with only a tiny change in rolling diameter.

As useful as those tire size calculators are, if you go to tirerack.com and start looking at mfgr's specs, you'll find a difference in the turns-per-mile specification for tires of the "same" size from different mfgr's. (Example: for 185/65-15 size, Conti's = 865 tpm, Yoko's = 848, a 2% difference).

Less technically, I think your 240 would look a bit odd with those little tires.
--
Bob (81-244GL B21F, 83-244DL B23F, 94-940Sedan B230F)