Tire circumference varies per Compound & Type

[SCClockDr]

For the Lotus Elise 111R '04 using Praiano63's Tune with the power limiter set at 94% to get PP to comply with 500 & using a Final of 3.000 to slow things down a bit for data logging purposes, I purchased every legal tire for the SSXR track and observed these top speeds (at RedLine) for the below tires on the stock rims.

• CH - 285 KMH
• CM - 286 KMH
• CS - 287 KMH
• SH - 288 KMH
• SM - 290 KMH
• SS - 297 KMH
• RH - 297 KMH
• RM - 297 KMH
• RS - 297 KMH
• RI - 297 KMH
• WET- 297 KMH

So the Comforts & Sports tires appear to have varying Circumferences per compound & the Racing tires appear to be identical for all compounds just different from the others.

This could well speak to some of our performance experiences with Racing Tires on some models.

I've seen posts querying this possibility this is to confirm those suspicions. I intend to test additional vehicles to prove what I am observing with the Lotus.

EDIT:
These differences for the comfort & sports tires may be due at least in part to growth due to speed like dragster drive slicks. While the Racing tires look more consistent and uniform indicating the difference is by design (greater diameter).

 

[Motor City Hami]

I think you are giving PD too much credit. My hypothesis would be more along the lines of PD programming a lap time multiplier to each tire compound. This lap time multiplier would not be smart enough to know when your car is traveling in a straight line. So even traveling in a straight line, the computer assumes that more grip = more speed.

As for the race tire issue, looking at your numbers, I would think that someone entered incorrect multipliers into the system. Comparing your numbers I would expect the distribution to be more like this:

• CH - 285 KMH
• CM - 286 KMH +0.3%
• CS - 287 KMH +0.3%
• SH - 288 KMH +0.3%
• SM - 290 KMH +0.7%
• SS - 297 KMH +2.4%
• RH - 298 KMH +0.3%
• RM - 300 KMH +0.7%
• RS - 307 KMH +2.4%