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therieldeal
therieldeal Reader
3/26/19 10:48 a.m.

Let’s talk tires! Specifically… who’s run both Hoosier A7’s and the Rival S 1.5 on the same car & can comment on differences? I’m back on the fence trying to decide which I want to run this year. Obviously the Rival is easier to live with as I can just leave them on the car all season. However the A7 has the potential to be significantly faster… how much faster? Driving style-wise, I set the car up loose and tend to “toss” it into turns, to get it to rotate ASAP & get back on the gas (high power fwd). Wondering which tire is going to be more forgiving in this situation… I’m thinking the BFG, as I’ve heard the A7 requires “precision”.

Robbie
Robbie GRM+ Memberand UltimaDork
3/26/19 10:51 a.m.

excellent question! I've been wondering too how close the current "street" race tires are to "DOT" race tires. The next step would be comparing to actual race tires, but I have a feeling for autox there might not be a big difference between the a7 and the best non DOT tire.  

GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
3/26/19 10:52 a.m.

The BFG will be much more forgiving with that kind of driving, R-comp slicks are the least forgiving type of tire to slide on.

therieldeal
therieldeal Reader
3/26/19 10:54 a.m.

I should add that I don't own a trailer or truck, so not having to swap wheels over and over again adds a fair bit of time value for me... time I could be sleeping in a little later, and/or helping my club actually run the event instead of screwing around with my tires.

Patientzero
Patientzero GRM+ Memberand New Reader
3/26/19 11:38 a.m.

I know Terry Fair has done back to back tests with Hoosiers and RE71's on the same car, same track, same day and the results are pretty surprising.  I think around 1 sec faster on the Hoosiers but don't quote me on that.  Check out the Vorshlag forum or Vorshlag on facebook.  He has all the results posted.

 

 

*Edit,  I know you asked about BFG's but given the BFG's and RE71's are near identical I figured this was relevant. 

Dusterbd13-michael
Dusterbd13-michael MegaDork
3/26/19 11:39 a.m.

This thread is relevant to my interest for the challenge car. 

alfadriver
alfadriver GRM+ Memberand MegaDork
3/26/19 11:55 a.m.
Dusterbd13-michael said:

This thread is relevant to my interest for the challenge car. 

realistically, since the tires are not part of the budget, IMHO, the teams should get the best of the best they can get.  In terms of raw time, the A7's will be much, much better.

This is similar to running drag slicks on the drag strip- in both situations, a second matters a lot.

Dusterbd13-michael
Dusterbd13-michael MegaDork
3/26/19 11:59 a.m.

But the changing tires at the event, and the wallet budget come into play for me. Rivals are far cheaper and less hassle, but much like the original post, i don't want to leave too much on the table.

Duke
Duke MegaDork
3/26/19 12:01 p.m.

My question is this:

How much different are new Rival 1.5s / RE-71Rs vs used A7s from JBT?

AngryCorvair
AngryCorvair GRM+ Memberand MegaDork
3/26/19 12:03 p.m.

FWIW MonZora plan is A7 in either 275/315 or 295/335.   kinda depends on whether or not i can get 4 widened sawblades into the budget vs just 2.

Robbie
Robbie GRM+ Memberand UltimaDork
3/26/19 12:08 p.m.

there is the size thing too. A7s come in almost every size. "street" tires not as much. 

KyAllroad (Jeremy)
KyAllroad (Jeremy) UltimaDork
3/26/19 12:13 p.m.

Not precisely an answer to your question but I can tell you that RE-71s VS A6s on the same car on the same day saw a delta of 1.5 seconds on a 40ish second course.  

Generally for most of us “not quite at the very tippy top” of the autocross world the RE-71 is a tic faster than the Rival S is.  The A-7s are faster than A-6s and don’t fall off as badly when they get to 80-100 runs.  

Robbie
Robbie GRM+ Memberand UltimaDork
3/26/19 12:30 p.m.

heres the vorschlag stuff I think:

My testing goals for this day were 3 fold: 1) Test out the new Ohlins R&T coilovers at MSR-C on their 1.7 mile CCW course. 2) Test both the Hoosier A7 and RE-71R street tires, back-to-back. 3) Get some data with oil/trans/diff temps with the newly added Mishimoto oil cooler.



Both sets of tires were pretty "tired" but the data was still valuable, and it would be back-to-back on the same day. I haven't done a street tire vs R-compound tire test like this in a LONG time. The first session would be on the RE-71R 200TW tires, which had 8 weekends of abuse on them now.



Remember, one of the Hoosier A7 tires was already showing a stripe of cord on the outside edge, so this is far from a perfect test. I moved that wheel to the left front, which is the less stressed front tire on this track. Hoping I get a clear lap in the first or second hot lap, so that the tires don't overheat and "fall off".

That's not how it worked out, of course. There were some rolling trains of cars, plus I got stuck behind a few slow pokes, but that's what happens on a nice member Saturday in late November.



I had several buddies out there, including Brian in his GT350, Jerry's last drive in his C6 Z06 (he just got a C7 Z06), and Kevin had his new C7 ZR1 on Michelin slicks.

 

As you will see in the video below, some knucklehead pulled right out of the pit lane onto the track, right in front of me on my first flying hot lap. That was the best shot at a good lap time on these tires. Gone. I also got blocked again on laps 2, 3, 5 and 6 (two of those shown above), and had a hair raising 3 wide pass on Lap 3 (the 86 driver talked to me after - he knew I was passing but the NSX pulled over on him!) I had to stick with hot lap 4, my only lap clear of traffic. Lap 4 on an A7 is usually not at all what you look for...



Lap times on Hoosier A7s (not showing the out lap or cool down laps)
Lap 1: 1:24.921 (traffic)
Lap 2: 1:29.021 (traffic)
Lap 3: 1:22.441 (traffic)
Lap 4: 1:21.138 
Lap 5: 1:21.507 (traffic)
Lap 6: 1:22.308 (traffic)

The AiM Solo was showing predictive times as quick as a 1:20.5, but all I ended up with only a 1:21.138. That's still a solid 8 tenths faster than this car has ever run here on RE-71R tires, and fully 3 laps past when these tires have their best performance (lap 1).



After 8 total laps in this session, both front tires were now showing cords. The worst one was showing cords on the inside and outside shoulders. This tire had been flipped inside out between the COTA and NOLA weekends - the majority of the wear is from the outside shoulder, even with -4° of front camber. The tread layer was actually peeling smooth off on the outer two inches, so these tires were officially D-U-N!



The temps on the fluids looks within spec (pic above shot right as I came into paddock), but only just in spec for the trans and diff. We have some ideas on how to combat high diff temps that we will address very soon. Engine oil looks perfect, and I rattle off all of the temps at the end of the Hoosier test video.

 

Not having our enclosed trailer meant I had to throw a bunch of tools and such in the back of the pickup. Brought a new battery jump box / air compressor to set pressures (#500psi) and a crappy jack that will never go to the track with us again. Pulled the four wheels and tires off and took them to Doghouse Performance for a tire swap to the RE-71R streets. That took about an hour while we sat out a session and let everything cool down.

 

Made it back out in the last session of the day, 4:30 pm, but luckily the temps were still cool and the partial clouds were keeping the track from cooking on this 70°F day. It was less crowded out there, but this set of tires had been sitting in the shop for a couple of months and took a couple of laps to scrub them back in and get the tires up to temp.



I edited the video down a good bit, but in this session I got stuck behind some slow Miatas, a new NSX, and two Porsches. Somehow I managed 3 laps in a row without traffic.

Lap times on RE-71Rs (not showing the out lap or cool down laps)
Lap 1: 1:28.748 (cold tires + caught a slow Miata)
Lap 2: 1:23.065 (still cold tires)
Lap 3: 1:22.126 (nearly matched the best lap these tires have ever done - when new)
Lap 4: 1:22.440 (made a big mistake in big bend - almost had a 1:21.1)
Lap 5: 1:26.188 (passed a new NSX + caught slow Porsche)
Lap 6: 1:24.050 (lapped slow Miata + caught slow Porsche)

On lap 3 everything mostly worked, and got that 1:22.126. That is less than 2 tenths off my best lap ever on these tires, 8 months earlier. So the stories of RE-71Rs wearing out or falling off might be greatly exaggerated. We used these RE-71Rs at yet another event after this!



The difference in grip from A7s to RE-71Rs was painfully apparent, and there is one full second difference in lap times (see log of best laps for each tire, above) but I fear that the lap time differences don't show a fair representation of that.

With the laps on the A7s I was considerably restricted by traffic. There was some "potential improvement" I didn't reach on the street tires, too. On my best RE-71R lap the AiM showed a 1:21.5 predicted time, and on Lap 4 it showed a 1:21.1 pred, but I screwed up something on both laps. Either time would have a marked improvement over the 1:21.9 previous best lap on these same tires. Oh well, I'm a bit of a hack driver and can't always match what the computer says is possible (that 1:21.9 lap was matching predicative, so it was a better driven lap).



The small changes made since that March NASA TT event - mostly brakes - are what makes the difference. The Whiteline and Ohlins coilovers are using about the same spring rates (which both produce more roll than I like on Hoosiers - see the 3 phases of Big Bend, above), but some of that potential lap time improvement from March to December would be firmer spring rates & damping of the Ohlins setup. I still need to get a lap on the RE-71Rs here on the MCS RR2s...

 

from here: http://www.vorshlag.com/forums/showthread.php?t=8324&page=3

Bottom line is the a7's were 1 second faster on an 81 second track, but also had a few strikes against them and Terry thinks the gap is bigger than the lap times show. 

Robbie
Robbie GRM+ Memberand UltimaDork
3/26/19 12:35 p.m.
Patientzero said:

I know Terry Fair has done back to back tests with Hoosiers and RE71's on the same car, same track, same day and the results are pretty surprising.  I think around 1 sec faster on the Hoosiers but don't quote me on that.  Check out the Vorshlag forum or Vorshlag on facebook.  He has all the results posted.

 

 

*Edit,  I know you asked about BFG's but given the BFG's and RE71's are near identical I figured this was relevant. 

ps thanks for the tip! I don't get over there as much as I should - Terry does great documentation of his exploits. 

Patientzero
Patientzero GRM+ Memberand New Reader
3/26/19 12:38 p.m.

I *think* he has since done another test with new tires.

 

Either way 1, possibly 2 seconds on a 81 second track.  Cut that in half for an AutoX course and I think you have a pretty fair comparison.  Is 1 second worth driving to the track and not changing tires?

Robbie
Robbie GRM+ Memberand UltimaDork
3/26/19 12:56 p.m.

the 'streetyness' of the re71 also intrigues me as to if it is a better drag tire than an a7. I know most anything is a better drag tire than an a7, so there's a chance. 

But I do think there is a real difference between track driving and autox that place slightly different needs on a tire. Still, this is great info for my mental database. 

codrus
codrus GRM+ Memberand UltraDork
3/26/19 1:02 p.m.
Patientzero said:

I *think* he has since done another test with new tires.

 

Either way 1, possibly 2 seconds on a 81 second track.  Cut that in half for an AutoX course and I think you have a pretty fair comparison.  Is 1 second worth driving to the track and not changing tires?

IME, it's more than a 1 second gain on a 40 second course.  I think part of that is because autox you're starting with cold tires, vs doing 4-5 laps in a row like the test above, and the Hoosiers heat up faster.

 

 

pinchvalve
pinchvalve GRM+ Memberand MegaDork
3/26/19 1:31 p.m.

I tried to read the article, but I ended up just staring the pictures of the awesome Mustang. 

z31maniac
z31maniac MegaDork
3/26/19 2:10 p.m.

If you aren't trying to win your class, I don't see the point in using more expensive, less durable tires that make your day of fun more a PITA.

therieldeal
therieldeal Reader
3/26/19 2:31 p.m.

Thanks for all of the responses and chasing down the Vorshlag article as well!

I’d forgotten about the drastic difference in size-for-size width.  My car runs ~23” miata-sized tires so I’d be looking at the 245/40R15 Rival in the front… which as it turns out, is only as wide as the 225/45R15 Hoosier. 

With the A7 I could step up to a “245” and “275” if I wanted to, in fact I have a set of worn-out 275’s in my basement that I got for almost-free for test-fitting purposes.

Hmmmmm.

Pete Gossett
Pete Gossett GRM+ Memberand MegaDork
3/26/19 2:34 p.m.
AngryCorvair said:

FWIW MonZora plan is A7 in either 275/315 or 295/335.   kinda depends on whether or not i can get 4 widened sawblades into the budget vs just 2.

C5 wagon wheels are almost free, do you just want the sawblades for aesthetics?

AngryCorvair
AngryCorvair GRM+ Memberand MegaDork
3/26/19 2:53 p.m.
Pete Gossett said:
AngryCorvair said:

FWIW MonZora plan is A7 in either 275/315 or 295/335.   kinda depends on whether or not i can get 4 widened sawblades into the budget vs just 2.

C5 wagon wheels are almost free, do you just want the sawblades for aesthetics?

i dig sawblades, and i hate C5 wagon wheels.   i have a square 9.5" set, which is pretty pinchy for 315s but a local C4 guy has run the 315 A7 on 9.5" rim and said the stopwatch tells him they're a couple percent sub-optimal.  for challenge, i think a couple percent is OK for the price.

docwyte
docwyte UltraDork
3/26/19 3:16 p.m.

The A7's are WAY faster.  They're also totally unacceptable for use to drive to/from events.

dr_strangeland
dr_strangeland New Reader
3/28/19 11:28 p.m.

I ran the A7 and the Rival S 1.5 on my hillclimb/autox car last season. Identical tire size (245/40/15) and exactly the same wheels (Advanti Storm S1 15x9).

They aren't really in the same league. It's true that the Rival is very fast, and if you can't get heat in the tires or it's greasy or cold, then the 200tw may be able to outperform the slick. It's also true that a fast driver on a 200tw can beat a relatively competetent driver on the Hoosier. But on my car, back to back, they are easier to drive at the limit and just plain faster. Worth several seconds on a hill course and a second or so on an autocross course.

I use the Rivals on the street, though, and I would consider using them for a car that only sees street use. They are quiet, wet performance is outstanding, and they tolerate cold very well.

Yes, swapping tires sucks, but I'll do it for fast time of the day. If it's cold I don't bother. Maybe run the RE71R on the transit and at the event.

dr_strangeland
dr_strangeland New Reader
3/28/19 11:36 p.m.
therieldeal said:

Thanks for all of the responses and chasing down the Vorshlag article as well!

I’d forgotten about the drastic difference in size-for-size width.  My car runs ~23” miata-sized tires so I’d be looking at the 245/40R15 Rival in the front… which as it turns out, is only as wide as the 225/45R15 Hoosier.

 

I'm not sure this is entirely accurate. I have the 245 A7 and 245 Rival mounted on the same wheel and if there's a difference, it's very minor. I could take a picture of the two next to each other the next time I swap wheels - probably Sunday.

I would say there's much more difference in compound and in tread void. Also, the Hoosiers are noticeably lighter.

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