205 vs 225 vs 245 on a Miata

This blog post is going to sound like a pissy rant. Fuck it, I’m due one.

Social media has created a dangerous situation where opinion is more important than fact. It’s almost like whoever yells the loudest and most often wins. And this brings me to a tired topic on Trackable Miatas. What’s faster, a 205, 225, or 245?

It’s a circular topic. At some point someone will chime in that it depends on power. Someone else will say you have to put a 205 on a 8″. That only lasts until someone says 205 is better on a 9″. Then another will say that 205s are proven to be faster than 225s or 245s on California tracks. As if tracks are different there? I’ve raced at Laguna Seca, Willow Springs, Thunderhill, and Sears Pt and they are no different than WGI, PittRace, NJMP or other east coast tracks I’ve raced at.

Next someone who is sick of being tread on will say, where’s the data? And all those people fall back on “it’s a proven fact,” without showing any. Honestly, I had to leave Trackable Miatas for a while because it’s the same people shouting the same nonsense without a shred of data to back it up.

It really is a bunch of hooey, and I’m just getting in a groove. First off, the notion that 205 tires are faster is flawed by the very fact that 205 tires aren’t all the same width. A 195 RS4 is wider than a 205 RE71R. A 205 Hoosier is wider than a 225 NT01. What 205 tire are you talking about? And then there’s the whole wheel width variable, as if offset, weight, tire pressure etc, weren’t factors to consider. And then some tracks are high speed and some are more about cornering.

I really have to question if any of the people that claim 205s are faster have done back-to-back testing using the same compound tires of different widths? Have they swapped wheel widths (same weight, same offset) on the same tire? If they have, they aren’t sharing the data.

Well, I can understand that, I haven’t either. But I’ll open the door just a tiny bit and shed some light on this.

Last Memorial Day four of us got together in Miatas and tested tires. Me, Alec Fitzgerald, Alyssa Merrill and Davey Thai got together in four Miatas and tested 10 sets of tires. We divided up the tires so that there would be some crossover.

  • Alyssa tested Hoosier A7s and R7s in 205, Maxxis RC1s in 245 and Hankook Z214 C51 in 2o5
  • I tested 225 RS4s on 8″ and 9″, and 245s on 9″, RE71Rs, and both Hoosiers
  • Alec tested RC1s, Z214, R7, and 245 RS4s.
  • Davey tested 205 Conti ECS, VR1, RE71R, 225 RS4s on 8″

We did this as scientifically as we could, recording air, track and tire temperatures, set optimal pressures, and ran multiple redundant sessions to gather data. I’m not going to share the lap times and data with you because information like that isn’t free. But I’ll give you this chart: same driver, same corner over 200′ of distance at 20′ intervals, two runs averaged, 225 RS4 on 8″ and 9″, 245 on 9″, and some other tires mixed in.

Average cornering Gs over 200′ of a corner.

6 thoughts on “205 vs 225 vs 245 on a Miata”

  1. What was the verdict?

    Från: Occam’s Racer
    Skickat: den 26 mars 2021 21:54
    Till: Torbjörn Linderson
    Ämne: [New post] 205 vs 225 vs 245 on a Miata

    occamsracers posted: ” This blog post is going to sound like a pissy rant. Fuck it, I’m due one. Social media has created a dangerous situation where opinion is more important than fact. It’s almost like whoever yells the loudest and most often wins. And this brings me to “

    Like

  2. This is great, thank you. Measurement always wins.

    It’s also something that seems to be misunderstood with two groups talking over each other. I’m always astonished when the conversations get mixed without people realizing it. “What tire is fastest on this wheel I already have?” is a very different question than “What wheel is fastest for the tire that my class allows?”

    Like

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