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Rs-4 vs ???


Indysupra
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Just now, LuckyKid said:

From our race notes at Road America:  Tested StarSpec II 225/45-16 and was 0.5 seconds slower per lap versus 245/40-15 RS4.

You guys drive that consistently? Sheesh.. my times fluctuate by more than that on back to back laps without traffic, no way I could discern (with any confidence) a difference of 0.5 seconds between tires on separate runs.

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13 minutes ago, enginerd said:

You guys drive that consistently? Sheesh.. my times fluctuate by more than that on back to back laps without traffic, no way I could discern (with any confidence) a difference of 0.5 seconds between tires on separate runs.

Just analyzing single lap times after the fact is tough, but at our home track, with data in the car we can tell pretty easily.  That was from a 2018 test, which devolved into a test-day for us and we wanted to collect that data.  What is interesting is that tire was VERY VERY good on the brakes vs. the RS4.  Without that it would likely be over a second slower.

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7 minutes ago, karman1970 said:

 

So the narrower, taller, heavier tire on a bigger wheel is slower?  Good to know. <green font>

It's just copied from our raw test notes.  Feel free to share your tire test notes as well.  We're trying to help here, right?

Edited by LuckyKid
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47 minutes ago, Indysupra said:

Thanks for the info. I have not heard much about the nt05. Anyone with experience with that tire? Still amazed that no one has been able to make a tire that matches the kumho. 

The RE-71R is a better tire, but it wears faster.  They also don't make a 245/40-15.  We'd have to go 18" to get it on the Miata. 

 

We've actually purchased a set of 285/30-18s RS4s just to test on the miata, but with the new fender rule, and the need to create custom spacers with hardware(adapters), its on hold now.  We likely will try to setup a test day at Road America mid-season to do that and some aero testing.  The idea is that we test the much larger tire apples to apples, then we can decide if the faster RE-71 compound would translate to faster, while also limiting wear.  

 

What size tire are you looking for?  The RS4s are going to be back in stock soon.

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2 hours ago, LuckyKid said:

The RE-71R is a better tire, but it wears faster.  They also don't make a 245/40-15.  We'd have to go 18" to get it on the Miata.  

Agree - RE-71R are faster by about 0.5 sec lap-on-lap on moderate temps at Sonoma for us over the RS-4, but they start going away pretty quickly compared to the RS-4.  We run 245-40-17 front and 255-35-17 rear (RS-4) and 245-40-17 all around when we run the RE-71R, so this is a bit of a flawed test.  However, have often considered if we were in a competition near the end we change to the RE-71R at the last stop to gain the 0.5 sec (or so) just for the last hour or two.  Never have done that, though.  More of a "what if" exercise.  

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