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Old 11-24-2014, 11:09 AM   #61
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Quote:
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For a track car, what's the approximate hp break where the extra inertia and rotating mass of the 10" wheel with wider tire makes sense? Compare 9" UL with 225 RC1 vs 10" UL and 245. Consider a track like Buttonwillow or Laguna seca on a 2000# car.
Miata specific:
For autocross, always the widest you can fit.
For track, 225's are faster on slow, tight tracks. Needs about 140whp to be faster on all tracks.
245's want 170whp-ish before they are significantly faster than 225's. Get into the 200's and the 245's are much faster.

So it's clear, inertia from tire wheel mass are never a measurable factor. It's drag from tire scrub only when cornering that makes the difference. Ever notice have even at WOT, a stock engined Miata has a hard time gaining speed in fast sweepers?
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Old 11-24-2014, 12:53 PM   #62
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Ever notice have even at WOT, a stock engined Miata has a hard time gaining speed in fast sweepers?
Gaining speed? I use steering wheel angle instead of braking. LOL.

BTW, I'm not seeing the 245s over on the website yet.
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Old 11-24-2014, 01:29 PM   #63
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They are listed out of order at the bottom of the drop down list of sizes. Just ordered mine, can't wait. Looks like there is going to be some rubbing on the inner fender wells or sway bar on the turn in tire if you turn to sharp because my 9 " wheels with 225's almost rub.
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Old 11-24-2014, 06:26 PM   #64
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Yep the 245 is now for sale. I have ordered a set as well for my ST2 LS1 Miata. I need more wheels.

And FWIW I have large flares so don't plan on using me as a fitment check data point.
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Old 11-24-2014, 06:30 PM   #65
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Guess I didn't look hard enough. Just ordered a set of 225s, about right for my 140rwhp car.

John, I was bummed by what happened to your car at MSR-C. Hope to see it out again soon.
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Old 11-24-2014, 07:21 PM   #66
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Thanks, no worries it is already on the mend. I just need to do some rewiring and it will be back to normal.
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Old 11-28-2014, 05:00 AM   #67
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Quote:
Originally Posted by emilio700 View Post
Miata specific:
For autocross, always the widest you can fit.
For track, 225's are faster on slow, tight tracks. Needs about 140whp to be faster on all tracks.
245's want 170whp-ish before they are significantly faster than 225's. Get into the 200's and the 245's are much faster.

So it's clear, inertia from tire wheel mass are never a measurable factor. It's drag from tire scrub only when cornering that makes the difference. Ever notice have even at WOT, a stock engined Miata has a hard time gaining speed in fast sweepers?
Great, thanks for the info. Since10s are so sparse at the moment, may we contrast 225s on 9s vs 245s on 9s now? :-)

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They are listed out of order at the bottom of the drop down list of sizes. Just ordered mine, can't wait. Looks like there is going to be some rubbing on the inner fender wells or sway bar on the turn in tire if you turn to sharp because my 9 " wheels with 225's almost rub.
I use a small spacer with the 9" 225s on my NB now for more steering input with out all the scuffing.

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Originally Posted by ZX-Tex View Post
Yep the 245 is now for sale. I have ordered a set as well for my ST2 LS1 Miata. I need more wheels.

And FWIW I have large flares so don't plan on using me as a fitment check data point.
Yup, my set shipped Tuesday.
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Old 11-28-2014, 06:17 AM   #68
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Strange question, but so are all of mine in one way or another;

225 RC1 vs 205 NT01 (or other decent non-purple Rcomps) on 9" on tighter tracks with about 170whp?
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Old 11-28-2014, 11:08 AM   #69
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Just placed an order for some 245's, I cant wait!
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Old 11-28-2014, 11:57 AM   #70
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Originally Posted by NiklasFalk View Post
Strange question, but so are all of mine in one way or another;

225 RC1 vs 205 NT01 (or other decent non-purple Rcomps) on 9" on tighter tracks with about 170whp?
I don't see how the 205/9 combo would be faster. 225 on 9 is perfect, and the RC-1s are at least equal in performance, so I vote add the width.
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Old 12-07-2014, 11:36 AM   #71
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Traded in my 225/45R15 BFG Rivals for 225/45R15 RC-1s. This is my first experience with an R-Comp tire. Me likey! Super easy to drive and I went 2.6 seconds per lap quicker on the MSR-Cresson 1.7CW. For perspective, my laptime was significantly faster than the other Miatas in the Advanced run group and about the same as the guys in Z06s and 911GT3s.

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Old 12-07-2014, 01:03 PM   #72
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Following the Thunderhill 25 hours this weekend. About 3hrs to go and an E46 BMW is leading E1 on Maxxis RC-1's.
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Old 12-07-2014, 01:20 PM   #73
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LOL. After all the bad-mouthing that BMW guys in particular have lobbed at the RC-1. That would really be funny. I'd be curious how often they had to change tires vs. the other makes.
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Old 12-09-2014, 03:08 PM   #74
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Guys, gave my perceptions of the RC1 to Jeffbucc. I think what I'm feeling with the tire is in large part related to sidewall stiffness. Would appreciate a correction if I'm all wet here.

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Rick mind highlighting the RC1 difference in regards to your Rivals? I flat-spotted mine somehow I decided to order some RC1s since the price point was pretty damn close to what I paid for Rivals.

How cold was the track, how'd they hold the heat, how'd they do cold, tire pressure etc etc.

You don't have to answer all those, but just getting a good datum point before next weekends autocross.
"Don't have to answer all those" . . . LOL. You know me too well.

What I found was pretty well summed up by Andy Hollis here:

https://grassrootsmotorsports.com/ar...re-track-days/

The only part that was different for me was Andy's comment about the tire being "edgier." I found the opposite vis-a-vis the Rival. I thought it was easier to drive/rotate. When pushed too far on the wrong side of the slip-angle/grip curve, it was easier to recover.

The tread compound used on the Maxxis seems really similar to that used on the Rival and RS-3. Seems to generate the same to a bit more peak grip (in the neighborhood of 1.2 to 1.3Gs on Honey Badger). The usable grip peak also seems to cover a broad range of slip angles, making for a forgiving tire. Not "peaky."

The difference from the EP street tires is that the sidewalls are much stiffer. That gives the following benefits:

1. The grip gets generated at a lower "perceived" slip angle. The slip angle at the tire contact patch is likely similar, but the lack of sidewall flex means that the slip angle being perceived by the driver is less. Maybe this is what Andy meant by "edgier."

2. Perceived slip angle vs. grip is extremely linear on both sides of the curve. Again, the minimized sidewall flex makes things more direct for the driver.

I really liked it. R-comps are often not recommended for new drivers because of the "peakiness" of the compounds, which makes learning how to drive at the edge and rotate the car a more difficult task. But the compound here isn't like that -- I think it's a great learning tire. The compound is also durable. The flip side, of course, is that it's not super-sticky like a Hoosier or top-level Toyo. Nonetheless, I was a lot faster on it compared to Rivals:

1995 Miata MSR-C 1.7CW (1_27.119) vs. 1995 Miata MSR-Cresson 1.7CW (1_29.734) by VJ 1995 Miata MSR-C 1.7CW Comparison (RC-1s vs. Rivals) | YouTube Doubler | Mashup Helper

As for coming up to temperature, it seemed to generate grip from the start of a session at least as well as a Rival (50-60F air temperatures). Got about 7psi increase on most loaded tire during a session. Seems to like about 2psi more than the Rival for best times (I was using 36psi after experimenting for 7 heat cycles).

TL;DR: Similar to a bit more grip than top EP street tires. Broad peak. More linear and easier to drive because of stiff sidewall. Durable. Great learning, practice and Enduro tire.
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Old 12-09-2014, 06:07 PM   #75
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"Similar to a bit more grip than top EP street tires" seems to be a very reserved comment considering a 2.6s improvement over the Rival.

-Ryan
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Old 12-09-2014, 06:42 PM   #76
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Quote:
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"Similar to a bit more grip than top EP street tires" seems to be a very reserved comment considering a 2.6s improvement over the Rival.

-Ryan
That number is about right actually. It's not just peak lateral grip but many other aspects of a tire performance envelope. Steering responsiveness, linearity, optimum slip angle, braking, braking feedback, etc.

These modern crop of EHP's don;t stop nearly as well as even the hardest compound race tire, for example. In our testing, Rivals were within .1g of the same size RC-1, sometime matching steady state. It depends on the radius of the turn, pavement temps and a few other variables.
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Old 12-09-2014, 06:47 PM   #77
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Yeah.

It's tough for me to make a confident laptime comparison though. We're talking ragged out Rivals vs. almost-new RC1s. I'm getting faster as a driver too. So, it's hard for me to attribute the 2.6s to just tires. I'm kind of going off what Andy said in that regard.

But I know what I felt. They felt much better, easier to drive. They rotate beautifully.

Emilio, I noticed the difference in braking. I could use a lot more brake with the RC1s without lockup. I'm at a loss. Why is that?
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Old 12-09-2014, 08:48 PM   #78
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Emilio, I noticed the difference in braking. I could use a lot more brake with the RC1s without lockup. I'm at a loss. Why is that?
Because race tire. Higher void-tread ratio (more contact patch), casing more optimized for grip with zero consideration for puncture resistance or comfort.
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Old 12-09-2014, 08:54 PM   #79
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Hmmmm . . . . Back to stiffness again. I see a pattern.
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Old 12-10-2014, 11:30 AM   #80
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I've been thinking of upgrading to RC-1's from my rivals on this next round of tires. Anyone have any thoughts on street driving RC-1's to and from the track on socal fwy's? Thoughts on wear from street miles and or risk associated with the less puncture resistant carcass on the street?

I'm thinking I should be ok... on the other hand, it might be a stupid idea just for a few ticks of the stopwatch.. Prob time to build a tire trailer or just sack up and start trailering my car i guess.
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