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| 2012 Boss 302 on square 305/30/19 RE-71R's at AMP - Graham MacNeil © |
For better or for worse, I have heard and read so much about RE-71R's. Everyone swears by the grip but complains about the wear. Generally speaking, the pros are:
1. They grip as well or better than most R comps.
2. They don't wear as quickly as R comps if driven occasionally on the street.
3. They work better in the rain than R comps.
The cons were limited to overheating quickly when used on track (being an autocross tire) and wearing too fast on heavy cars like mine.
In the popular 200 TW category, they are faster than the popular Hankook RS-4's and BFGoodrich Rival S's according to published Tire Rack Tests. According to plenty of reviews, they are also faster than well established R comps like R888R's (which don't seem to work too well on heavy cars anyway) and the venerable NT01's. But I was still hesitant for a while until I talked to a tire tech support gentleman at Tire Rack who has gone faster on RE-71R's than NT01s. In a Mustang (his own, not a published test). That was all I needed to hear. The consensus was that if it isn't a near-slick or better, it's probably slower, at least for a few laps until the 71R's overheated.
The pros far outweighed the cons for me. I told myself I needed them for Time Attack this year so I only needed to push them for a few hot laps then I can dial back to 7 or 8/10ths for HPDE and lapping sessions, possibly making them last much longer. But I still get basically best-in-class grip for Time Attack to be competitive. I also drive the car on the street, something RE-71R's are good at for the level of grip they have. I ordered a set of four 305/30/19's to go on the new APEX EC-7 19x11" wheels. You can read about my new setup and what's needed to fit here.
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| Four 305/30/19 Bridgestone Potenza RE-71R tires on Apex EC-7 19x11" ET52 Wheels |
After a few weeks (had to wait for a full set of 305/30/19s, who would've thought they don't stock those!), they were on the car... now, it's worth noting that I had HUGE expectations for those tires. Looking at them in person made things worse because they looked huge. They measured over 4 ft stacked up. At almost exactly 124 cm (1,240 mm), that puts section width at almost exactly 310 when mounted on an 11" wheel.
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| Stacked RE-71R's measuring over 4 ft, nearly 124 cm |
When mounted on the car, they poked out a little up front and were basically flush with the rear. That bit of poke up front really worried at first, mainly because I thought they would rub and also because of Time Attack (TA) class limitations on poke beyond stock fender width. Thankfully, it was under the 1/2" allowed so that wasn't a problem and the first shakedown at the track confirmed no rubbing. I was ecstatic.
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| 2012 Boss 302 on square 305/30/19 RE-71R's at Atlantic Motorsport Park |
So what are they like on track?
High expectations very often result in disappointment... but not this time. First time out on track was with the BMW Club Atlantic Advanced Driver Training (HPDE) in June (last month). With no timing, I could not objectively confirm how much better they were, but they felt fantastic. The car had loads and loads of front end grip, to the point where the car started feeling tail happy. Part of the reason, no doubt, is the result of a 2"+ wider front track due to 1" spacers on each side to make the wheels and tires fit, and the wider wheels. I'm used to trail braking into almost every corner on track. Driving exactly the same way, I found the back end starting to come out into a few corners on track. Someone behind me even said "I see what you mean by being tail happy!" after one session. But overall limits were also significantly higher and it was very progressive and controllable.
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| Cayman GT4, BMW Z4 M Coupe, Boss 302 at AMP with BMW Club Atlantic |
One regular at the BMW Club drives a modified Porsche 911 (996); it has coil overs, anti roll bars, brakes, and R comps and a proper driver mod. Before this, I couldn't keep up with him driving as fast as appropriate for an HPDE event (or if we're both flat out at other events). This time, I was able to keep up with him while warming up tires and waiting for oil temp to get up. I even ended up getting by later. All of this without pushing hard. Limits were just significantly higher. I was trying to incrementally add speed in each corner each lap up until 7-8/10ths. I knew I was going much quicker than before, yet I wasn't breaking a sweat to do that.
To put it into perspective, when I switched from Pilot Super Sports to try Firestone's Indy 500 tires (link of review here), I could feel that the car has less grip but I couldn't discern a significant difference in pace. I felt like they would be less than 1 sec slower and they ended up almost exactly 1 sec slower than my best lap on fresh PSS tires and less than that compared to worn out PSS's. This time, pace felt much, much quicker... more on that in a bit.
Temperature & Pressure
Pressure wise, I started at 30 cold, street driving pressure. I knew I would have to let air out after the first session, but I didn't realize how much. Pressure jumped to 39 psi after about 15-20 mins. I aired it down to 34 psi and it went back up to 37 psi. I dropped it to 32 psi and it went up to 34 psi and it stayed there. 34 psi seemed to work well. I tried 32 psi later in the day but that felt a bit soft and I could feel a slight delay in responses. 37 psi got greasy sooner than I would have liked. 34 psi seems to be the sweet spot.
Running 34 psi and -2.3 deg camber up front, temperature across the tread was fairly consistent, ranging from 147 deg F to 149 deg F to 152 deg F from inside to middle to outer tread/shoulder (64 deg C, 65 deg C, 67 deg C)
What are they like in the wet?
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| Boss 302 in the wet at AMP for Time Attack 2019 Event #1 - Kevin Doubleday © |
Just 3 weeks after the BMW Club HPDE, it was (tire) judgement day. First time attack of the season, first time attack for me in about 3 years, and first timed session in the car on tires with good grip. But the morning was rainy... To say I was disappointed would have been a massive understatement. Worse yet, the playful tail happy character a few weeks prior turned into a very loose car that threatened to bite in every single corner. This was made much worse by temperatures.
Here's a tip: RE-71R's do NOT work in the cold. They need heat to work, much like a proper R comp or a race tire. You'll hear people complain about these tires not liking heat which could give the impression that they work cold but that's far from true. It just means they have a narrow temperature window where they work well. Cold, they're hard and slippery. Hot, they're greasy and slippery. Temperature readings in the wet across the tread were 86 deg F, 88 deg F, and 90 deg F from inside to outer tread (30 deg C, 31 deg C, and 32 deg C), all less than half the readings from the previous weekend at the track. Every time I went to the go fast pedal to add speed, the back end came out. Driving "slow", there was no heat in the tires. They didn't hydroplane or anything, they just couldn't grip. I bet you they'd perform better with tire warmers or on a less neutral setup that could build speed instead of going sideways. But in the rain, without temperature, they just don't work on this car.
Lap Times
I ran 1:23's and 1:24's all morning at the time attack in the rain, with one particularly wet session and a bit of a downpour that had a best of 1:28. I was about to give up on finding out what the tires can do that day, but the rain started to let up over lunch and some patches of asphalt started dry. I had my hopes high and was waiting for a dry session like a kid waiting for Santa on Christmas Eve...
The track never dried completely, but the racing line was mostly dry. It was still overcast with temperatures hovering around 59 deg F according to the dash read out so asphalt never warmed up. But it was dry enough to build speed. I got some heat in the tires and started seeing results.
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| Track Addict Time Attack Session Screenshot |
The first "dry" session, I quickly started shaving seconds and settled into running 1:18's. I think the car could run 1:18's all day in the dry without breaking a sweat. Once I felt comfortable that the fast line has dried, I pushed for one lap and got a best of 1:17.10. A whopping 3.3 seconds quicker than my previous best. If you've read my Pilot Super Sport and Firestone Indy 500 comparison from last summer, you know that I ran bests of 1:20.4 on the Michelin's and 1:21.4 on the Firestone's.
Keep in mind, in both cases, those times were in warmer day weather with more grip. Cool temps are good for power, not so much grip, especially when you consider this is Canada so "cool" isn't 70-80 deg F, it's 50-60 deg F. As mentioned earlier, dash temps were around 59 deg F. Most high performance summer tires are not recommended below 7 deg C or 45 deg F. The original (crappy) Pirelli P Zero that came with the car drove like hockey pucks below 50 deg F. Here I was, running a tire that - for all intents and purposes - performs and acts like an R comp, in temperatures barely warmer than minimum recommended temperatures for a street summer tire. This, however, probably helped by preventing the often complained about RE-71R overheating issue on track with heavy cars. As you can see, I ran my best lap time on Lap 11.
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| 2012 Boss 302 at Atlantic Motorsport Park in Turn 3 - Kevin Doubleday © |
The second (and last) dry session, was much shorter. I just wanted to see if I could repeat the time. I couldn't quite hit a 1:17.1, but - aside from traffic the first few laps - I did a low 1:18 and a few 17's, with a best of 1:17.57. So yes, 17's are repeatable. My goal had been to run 1:18's with a "nice to have" being 1:17's because I figured they should be 2 seconds quicker. After running a 1:17.1 on my first time out in the dry without ideal conditions, I am now targeting 1:16's by the end of the season, with a 1:15.9x as a "nice to have". The 1:15 may be a tall order, but I have no doubt I can find a few tenths to get comfortably into the 1:16's.
If you're curious about how those numbers compare and you're trying to gauge, the fastest a production based chassis has gone is 1:10.x. The track record for a closed wheel car was just broken this year in a very well driven and built pro-stock car converted to run road courses with a time of 1:08.7.
And although it's a bit of a hollow victory, this seems to be the fastest any Boss 302 has gone, or any Mustang on factory suspension in general and any car at all in CASC TA-GT1 class at our track (Canadian Automobile Sports Club Time Attack-GT1 class). Needless to say, I was very happy with the result. The quickest Boss 302 before was a ‘12 with Steeda suspension, bolt ons/tune that did a 1:17.98 on 275/35/18 NT01’s a few years ago.
Wear...
Like I said earlier, high expectations very often result in disappointment. Thankfully, I had very low expectations for wear, based on the 71R's track record of being a very fast wearing tire. So I was pleasantly surprised when I didn't burn them in a couple of days. There hasn't been that much time on them yet. Here's a summary:
1. 5.5 sessions at the BMW Club Atlantic Advanced Driver Training (HPDE)
2. One Qualifying (15-20 mins) and 2 short Time Attack Sessions (warm up lap, 3 hot laps, and 1 cool down) in the rain.
3. Two Time Attack Sessions (each about 15 mins) in the dry.
4. Three approx. 20 min lapping Sessions with Atlantic Formula Racing Association (AFRA), also in the rain.
Here what the worst looking tire looks like (our track is hard on left side, hardest on driver's front):
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| RE-71R Driver Front Wear on 2012 Boss 302 |
More shoulder wear than I'd have liked to see, but likely as good as I can get on stock suspension since camber plates are maxed out with the stock struts. Not bad at all otherwise, though. Plenty of tread left otherwise. I might try to pump pressure up a little outside to save the shoulders and dial pace back a bit to avoid the tires getting too greasy. Other tires didn't look as bad. Passenger side tires looked nearly brand new.
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| RE-71R Passenger Front Wear on 2012 Boss 302 |
Too Long, Didn't Read (TL;DR)
I had very high expectations for grip compared to my last two tires, Michelin PSS and Firestone Indy 500's and I wasn't disappointed. Best lap time on the very first dry timed session was 1:17.1, 3.3 and 4.3 seconds better than Pilot Super Sports and Firestone Indy 500's, respectively. That was on a cool day with air temperatures around 59 deg F so they should have even more grip on a warmer day, although at the expense of power. Tires seemed to like 34 psi hot pressure best, with responses being a little dulled at 32 psi and tires getting greasier than I'd like at 37 psi. I am confident that there is more time left in it the car and aiming for a 1:16.x by the end of the season, which would make them up to 4 seconds faster than Pilot Super Sports on a 1.6 mile track.
With -2.3 deg camber up front and 34 psi and measured on a warmer HPDE day, temperature across the tread was fairly even ranging from 147 deg F to 149 deg F to 152 deg F from inside to middle to outer tread/shoulder (64 deg C, 65 deg C, 67 deg C)
If you go to square 305/30/19's on an S197 Mustang, which require 1" spacers up front, and don't change anything else in the suspension, the car will be noticeably more neutral/loose, even if you had a square wheel and tire setup before. This is likely very much a result of the 2"+ wider track due to the spacers and wider wheels.
Their reputation as fast wearing is not unfounded, although they seem to be wearing well compared to what I expected. If you don't see frequent track temperatures above 80 deg F, I suspect they'll last longer than most reviews in hotter US weather indicate.
They absolutely need heat to work. Those tires do not work in the cold. My best in the wet was a 1:23.4, which was very sketchy and more than 6 seconds slower than dry. They are not confidence inspiring at all without heat in them, especially in the wet.
Overall, I'm very happy with the tires and would highly recommend them for a Time Attack/Time Trial setup. I'd be hesitant for a purely HPDE car, but will confirm later after I see how much life I can get out of them.
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How is the treadwear for easy street/highway driving? I’ve got tracks 150 miles away and don’t want to change wheels at the track. Would like to drive there with them on.
ReplyDeleteI wouldn't worry about street miles at all for a car that sees regular track time. They were well enough on the street that it will never be an issue compared to track wear.
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