This site illustrates the tire pretty well, just not our size:
www.tiresdirect.net/TOYO_Proxes_R1R_195_50R15_82V_P4715C885.cfm

I spoke with Debbie from Toyo today, 888 444 8696 she said the tire does not come in 225x50x15 but does come in 225x45x15 and there is a good supply available, but I would have to call my local Toyo guy. I left Bryan Shakelford a message and haven't heard back on price and his availability.

This site is from NASA's forum from a couple of years ago, drivers have experimented and compared 888's, ra1's with the R1R's, note that most of the cars are higher h/p and more weight than our cars which may not make the results totally accurate for us.
www.nasaforums.com/viewtopic.php?f=2&t=26249&start=10

Part1
The Toyo Proxes R1R really blurs the line between street and race tire. Despite its sticky rubber compound, the Toyo R1R is actually quite streetable, much like the company’s true R-compound tires.
That engineering really shines when you ask an R1R-equipped car to corner. “Awesome grip is the Toyo’s strong point,” Andy explained. “You feel like you are literally glued to the ground.” Impressive for a tire that can be found online for just $124 apiece.
Unfortunately, the Toyo was a bit hard to control at the limit due to its abrupt breakaway manners. Andy noted that pushing the tire over the edge resulted in “a heavy staccato chatter that is hard to modulate due to a lack of feel.”
The Toyo also exhibited the slowest turn-in response, requiring a total reset of driving technique and timing to make use of all that grip. It helped to give the car more lead time in the slalom, but the tire still took too long to react. That hurt the Toyo’s times, which were solidly in third place.
Toyo does offer something that the others don’t, however: a wide variety of 15-inch sizes. In addition to the 205/50R15 size that we tested, the Proxes R1R is also available in 195/50R15, 195/55R15 and 225/45R15.
That 225/45R15 is a great, fat tire that works well on a 15x7.5-inch wheel. Another option is the 205/45R16; it’s about two tenths of an inch taller than the 205/50R15 and 225/45R15, but offers more precise transitional response thanks to its short sidewalls. (By the way, we’ll be testing these various options in an upcoming issue of GRM.)
Conclusion: Leech-like grip, but also just as squirmy at the limit.

Part2
To put it simply, the 225/45R15 Toyo Proxes R1R is big and fat. Tires with wider footprints typically perform well in long, sweeping turns but struggle to keep up in transitional slaloms. The bigger Toyo isn’t a typical tire, however.
Thanks to awesome grip and response, it set fast segment times in our slalom. Unfortunately, sustained cornering was the Toyo’s downfall: The tire tended to overheat and fall off near the ends of long corners, limiting how much power we could put down when coming out of a curve.
During this test session, the Toyo nearly matched the Bridgestone’s times. The tire’s additional width seemed to make little, if any, difference in its final ranking.