The “fast tyre” was not fast

Change tyres, drive the same circuit. That is all it is, but it becomes awkward once you write it down. What you feel and what the clock says do not agree.

The ranking by feel

Ranked by controllability and grip feel, the order was clear.

• Yokohama ADVAN A048 MH — the easiest to read. The limit of grip comes through to your hands
• Pirelli P-ZERO CORSA — the behaviour is readable. It can be driven like a radial, and in a word it is easy to drift
• Michelin Pilot Sport Cup — thin on grip feel. On rails, with nothing to grab hold of

It should have been fast in that order.

The ranking by the clock

The bests that remain from SUGO, listed by generation of surface.

The A048 went on in October. Air temperature was around 15℃, better conditions than August. Even so it was about 1.5 seconds slower. Nothing on the car itself had been changed.

The hypothesis I formed

According to the tyre shop, SUGO and Fuji Speedway are among the highest-friction surfaces in Japan. That is why tyres wear so heavily, and in fact the A048 MH was used up in about five hours of actual running out of a ten-hour allocation.

The European circuits — Misano, Paul Ricard — felt low-friction and flat when I drove them.

Perhaps Michelin is faster on high-friction circuits (Motegi, Fuji Speedway, SUGO, Suzuka) and the A048 is faster on low-friction ones.

This is a hypothesis and it has not been tested. Swapping two sets of wheels on the same day at the same temperature to compare them was not something I could do alone.

There is a counter-argument

I have been told that the result would very likely change with the M compound rather than MH. That is reasonable, but I do not know how long the M lasts. If the A048 MH gives five hours, the M would be shorter. It becomes a trade-off against economics, and it has stayed on the list as homework.

Another case where the record and the memory did not match

When I moved from the P-ZERO CORSA to the Pilot Sport Cup, I remembered it as “much faster”. The log says 1:40.840 → 1:40.458. That is 0.4 seconds. Almost no difference.

What felt faster was probably not the time but the way I was driving. On the old surface the PS Cup was unmanageable once oversteer appeared, and I spun often. After the new surface, I could control deliberate oversteer as well.

The tyres I used

In the first half of the 2000s there were almost no S-tyre options in 205/50/17, and there were periods when economics left me no choice but a radial.