GR86 Finished

Champiro of the World – David’s GR86

If you’ve got a full wallet and you’re looking for a good time, check out “86 Cup.” Admittedly, 100% of my knowledge about it is from David, who approached me to help change his worn GT Radial Champiro SX2 tires with a brand new set. Still, I’ll “telephone” this knowledge over to you, and if it sounds enticing, you can check it out for yourself.

I’m told that 86 Cup is a one-make time attack league hosted by the tire manufacturer known as GT Radial. One of the key motivational factors is that if you win races while using their tire, they’ll give you prizes right away. So you, Mr. John or Jane Doe can purchase a brand new Toyota GR86 or Subaru BRZ and start winning prizes for racing your completely stock car against other completely stock cars. And the best part is that you don’t need to be sponsored to earn “free stuff” — you just need to be fast. Arguably, winning races MIGHT be easier than scoring a sponsorship these days, unless you’ve got a large social media following in your pocket.

New SX2 Mounted

On your path to becoming a pro racer, you might imagine that the smart idea is to use the widest possible tire to… you know… turn faster. However, there are limits to every good thing. The OEM Toyota 18″ GR86 wheel is an 18×7.5 with a 215/40/18 tire mounted to it. Pushing the tire size on that wheel to a 225 is probably fine, but when he sized-up to a 235, David saw odd things start to happen. Though it’s hard to notice in the photos, on this Champiro SX2 tire, the flat sidewall started to curve outward in an awkward way.

SX2 Bulge

With that excess width, there was a bit too much sidewall flex, and a sad situation would emerge. To fix excessive flex and cure the tire from rolling onto its sidewall while cornering, you might try to raise tire pressure. But the contact patch eventually starts to become smaller as the center part of the tire begins to bulge out. So, you might lower the tire pressure to regain the contact patch, but so too would return the sidewall flex.

Unfortunately, for this SX2 (not the SX2 RS), the only offerings for 18″ are 235 and 265-width. But hey, it’s a great excuse to upgrade wheels 😉

Unexpectedly, the SX2 is offered in different UTQG ratings, depending on the size. GT Radial’s website shows that the 235/40/18 that David is using should be a 200-treadwear tire. But the label on the tires he brought to me had “Treadwear 260” written on them. I have a feeling that one of these is the old rating and the other is the new one, but which-is-which is anyone’s guess. To add further confusion, I’m stumped as to why GT Radial split the SX2 into 2 tires, the SX2 and SX2RS — because both of these look basically the same, and both have choices with 200 UTQG. I assume that good, clear reasons exist for these design / marketing choices, although they’re not immediately obvious. Tire manufacturers sure work in mysterious ways.

About the Author


Hi, I'm Michael, and I'm the main guy behind Goodnight Tire Service. I'm the writer of this article and the person that helps people with their tires. If you're looking for help with your tires, consider taking advantage of my after-hours services, and send me a message. My contact info is at the top of the page.

2 thoughts on “Champiro of the World – David’s GR86

  1. The 18” SX2 is no longer manufactured. David is buying old stock. The RS is much much faster and is actually manufactured in the USA.

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