Actual rolling circumference of new tires

Hi everyone,

I'm planning to buy a new set of 195/60 HR 14 summer tires soon.
Since I adjusted my speedometer to minimize the error with my old Conti SportContact tires, I want to buy tires whose actual rolling circumference is as close as possible to that of the old ones.
For explanation: The rolling circumference of new tires may deviate from the standard value (in my case = 1800 mm) by ,5% or -2,5%.

If I happen to get a particularly "small" tire size, my speedometer already shows about 5 km/h too high in the maximum speed range, even with new tires. If the tires are completely worn out, they can even be about 7 km/h too fast.
That's why I didn't bother painstakingly calibrating the speedometer using highway mileage markers, a stopwatch, and adjusting the needle to ensure a maximum error of 2 km/h.

Therefore, my question is: Does anyone know what the actual rolling circumferences of individual brands and tire models are, and can anyone give me specific tips on which tires (like the old ones) tend to be slightly larger than the standard size?
Do you know of any resources that provide more detailed information than just the standard rolling circumference of specific tire sizes?

I actually don't want to buy the SportContact again, because of the quite poor lateral grip, especially on wet roads, on the Golf 3. Although she had bought them used as inexpensive test samples for determining the correct size, they were neither damaged nor excessively old (due to the curing process of the film emulsion).

Hello.

You have to be careful with that calculation!

When the wheel is resting on the ground without any load, you can easily measure its circumference. However, as soon as the wheel is loaded onto the vehicle, it compresses. This means the radius decreases, and consequently, so does the effective circumference. It will be difficult to determine this actual circumference, as it changes due to tire pressure and the vehicle's load. When driving slowly, the air inside the tire is cool, but at 200 km/h on the highway, things look quite different. It's possible that the centrifugal force acting on the wheel also plays a role.

Diesel-Dirk wrote:

But as soon as the wheel is loaded on the vehicle, the wheel compresses. So, the radius becomes smaller, and consequently, the effective circumference also decreases. You will find it difficult to determine this actual circumference, as it changes due to tire pressure and the vehicle's load. When driving slowly, the air in the tire is cold, but at 200 km/h on the highway, it looks completely different. Possibly, the centrifugal force acting on the wheel also plays a role.

It's clear now.
But every tire is exposed to these influences, so on the same vehicle and with the same air pressure, they are also affected to the same extent.
Therefore, manufacturing-related size variations are almost fully reflected in the actual operating conditions and affect the roll circumference.
Therefore, I even believe that differences in the outer diameter of tires mounted on rims can provide quite accurate indications of differences in the actual rolling circumference.

Hi Ulf, there are tables provided by tire manufacturers that specify the dynamic rolling circumference for YOUR tires. I have one from Conti here at work. It is also available upon request from the tire dealer.
Sure. Here's the translation of the text from German to English:

'Gr.W.'

Quote:

There are tables provided by tire manufacturers regarding the dynamic rolling circumference for YOUR tires. It is also available upon request from the tire dealer.

Thank you, but the issue has been resolved.
After sending various emails to different manufacturers (and receiving, as usual, only partially helpful responses), I decided to purchase Pirelli P 6000 tires. According to the manufacturer, they were at least not smaller than the standard size (measured: 1802 mm), and as 185s on my wife's Ibiza, they felt quite good in terms of driving experience.

As a side effect, I got a clue as to why my wife, who drives a similar car with the 90 hp VTG engine, always consumes about 0.5 liters per 100 km more than my AFN: When coasting downhill in neutral, my Golf now gains slightly less speed than with the old tires of the same size, which means the rolling resistance of the P 6000 tires is apparently higher.
Whether it will actually make a difference of half a liter for me remains to be seen, and the next gas station stops will tell.