1998 v70 Different Tire Sizes, OK or No?

Post by **MrAl** » 06 May 2015, 14:59

Hi,

I found out today that the back tires on this car are 195 60 R 15 and the front are 195 65 R 15. I had to wonder if that makes a difference with the speed sensor for the car and maybe the brakes too?

That means that the front tires sit up about 4.9 mm more than the back, flat ground to bottom of rim, and of course the rear tires turn a little more often than the front over distance.

Post by **misha** » 06 May 2015, 15:01

Put the higher profile on the back.It will look better...otherwise...no problem.

Post by **erikv11** » 06 May 2015, 16:03

You are correct about the speed sensor but it should be of basically no consequence for brakes or ABS.

The speedometer is set up for the front tires to be 195-60-15, so with those one the front it will be accurate.

The way you have it now, with the taller 195-65-15 on the front, the speedo reads a hair slow. When it says 65, you are actually going 67. The odometer clocks a little slow by the same percentage difference.

http://tire-size-conversion.com/speedom ... libration/ etc.

Post by **misha** » 06 May 2015, 16:09

erikv11 wrote:The speedometer is set up for the front tires to be 195-60-15...

What about mine?It came from the factory with 16" Persus wheels and with 205/50/16 tyres.

Post by **erikv11** » 06 May 2015, 17:43

My guess is the speedos are all set up the same, but I do not know. If you check the online calculators you will see that those tires are almost exactly the same size (diameter is only 4 mm difference, whereas 195-65-15 vs. 195-60-15 is 20 mm difference).

So a 205-50-16 is running at 64.62 mph when the speedo (set up for 195-60-15) says 65.0 mph, I suspect Volvo just said don't worry about the 0.6% difference. For example, the car will have clocked 198,830 when the odometer reads 200,000, this is a tiny difference.

Post by **Ozark Lee** » 06 May 2015, 18:51

I haven't seen a specific trim stated bit if this is a AWD car then the tires must all be the same size, even tread wear differences can mess up the transfer case. On a FWD car I agree with the others, the car doesn't really care.

...Lee

Post by **j-dawg** » 06 May 2015, 21:22

I had a flat last weekend, and the donut spare on the front was setting off the traction control. Not a permanent-damage thing, but annoying.

If you have a limited-slip differential, you will drive it nuts by using two tires of different sizes. LSDs work to reduce the difference between wheel speeds (ie, to limit the slip). Putting a donut spare on a clutch-type LSD will wear it out right quick. I don't think any FWD P80 cars came with LSDs, though.

Post by **MrAl** » 06 May 2015, 22:14

Hello again,

Thanks much for the good replies.

Sorry i forgot to mention this is a FWD and non turbo.
I will have to start including that info in the title with the year and model i guess.

So it sounds like it does not matter to any OBD2 detection sensors if the car is FWD, so that's good. I'd hate to have to mess with getting more tires at this point in time.

Thanks again.