Planet-9 Porsche Forum banner

1 - 16 of 16 Posts

·
Registered
Joined
·
43 Posts
Discussion Starter #1
I've been autocrossing my 981 since 2014.
I added the GT3 LCAs this fall with camber at -2.8F, -2.5R. At the next autocross, a pyrometer showed even temps across the tire width - yeah! Unfortunately my RE71-Rs had no more traction after almost two years of AX (about the same thing happened with Sport Cup 2's).

I'd like to give Hoosier A7's a shot next year (and go to -3 camber). I have no trailer or means to haul my AX wheels to our site, which is 110 highway miles away. Rain/wet is extremely unlikely but I'm concerned that the street driving will use up/heat cycle out the A7's very quickly.

Does anybody have experience/knowledge of the impact of street driving on A7s?
 

·
Registered
Joined
·
237 Posts
Aren't A7s R-comps? As in, don't drive them on the street? 40 treadwear might be awesome for a 1-mile AX but I could see your 200-mile roundtrip finishing them off in one shot.

For about $2k, you can get a hitch that goes behind the license plate and a tire trailer - would be a good investment if you want to run non-street tires.

Tom
 

·
Registered
Joined
·
43 Posts
Discussion Starter #3
Thanks. I know a couple of people who drive Hoosiers to the event, though shorter street distance than I have. Others use a trailer, which just isn't an option for me.

I have looked at the hitch/trailer approach. A serious issue with that is I do course design & setup so I need to start work at 6:45, leaving home at 4:30. I'm not too excited about leaving home 45 minutes earlier so I can change wheels onsite.
 

·
Registered
Joined
·
51 Posts
Does anybody have experience/knowledge of the impact of street driving on A7s?
No experience with those tires, but for $20 a day you can rent a Uhaul pickup and for another $20 a flat bed trailer. I don't know how often you AX but that might be an option to consider.
 

·
Registered
Joined
·
43 Posts
Discussion Starter #5
Thanks. I may give that a shot. Because of the mileage and probable need for 2 days it would be more $ but could still actually save money.
 

·
Registered
Joined
·
43 Posts
Discussion Starter #6
No experience with those tires, but for $20 a day you can rent a Uhaul pickup and for another $20 a flat bed trailer. I don't know how often you AX but that might be an option to consider.
I just checked Uhaul online. Since I would have to do 2 days and 240 miles, the pickup alone would cost $190. It wasn't clear if they'd let you tow the auto transport with their pickup, they just listed other trailers.
 

·
Registered
Joined
·
939 Posts
Maybe a new bigger footprint RE71R's are in your future. So, Hoosiers are 3 seconds faster, but its a hassle to get your car there with Hoosiers on. Run reduced tire pressure with your camber to almost getting some tire roll by measurement of the triangles on the side wall down to 28 psi. You may gain a few 1/10's of second, still not in Hoosier territory though. I plan on upgrading this spring to Hoosiers, but my track is 30 miles away.
 

·
Registered
Joined
·
583 Posts
A couple of problems running R7s on the street.

They are really only good for 5-6 heat cycles with max grip and then they fall off a pretty steep cliff and quickly turn to stone. By 15 HC they are comparable to a nice All season tire with a 500 TW rating- 3-5 seconds slower depending on your course. You probably don't want to use up 2 of your golden HC commuting to the track because they will be finished in one day. $1600 per day for AX adds up fast.

The other big problem is that they are like double sided tape and pick up all manner of nails, screws, broken glass, and debris that will cut down your tires and render them useless. We need a plan "B".

For AX the RE-71r is hard to beat because you can drive them to the track, they come to full grip quickly, and are street capable even in rain. If you want to explore a different tire I can recommend the Nitto NT-01. Similar lap times to the RE-71 and good to the last cord so they do last longer. They need a bit more heat to come to full grip but a very easy tire to drive fast.

For legit use of the R7, the only realistic way is to trailer in and mount them just before timed runs, Then dismount them, bag them up, and store them in a controlled temp garage. Very finicky tire but very quick for 5-6 HC.
 

·
Registered
Joined
·
51 Posts
I just checked Uhaul online. Since I would have to do 2 days and 240 miles, the pickup alone would cost $190. It wasn't clear if they'd let you tow the auto transport with their pickup, they just listed other trailers.
Wow, i thought they had unlimited mileage.... yeah that won't work... sorry for the mis-information.
 

·
Registered
Joined
·
43 Posts
Discussion Starter #10
Thanks - good and sad info. The controlled temp storage is a big issue because my Northern California garage gets pretty hot in the summer, particularly after putting a couple of hot cars in it. They would probably fit in the dining room ...:hilarious:

Would a day of AX (40 second runs, 4 AM, 4 PM) be considered a heat cycle?

A new set of RE-71R's is the backup plan, but I'm getting older and not faster so would really like to experience the R7 grip and times. I'll have to explore transport options some more or do the Boxster hitch/trailer thing. Somebody else can do course setup while I change wheels.
 

·
Registered
Joined
·
221 Posts
I'm not sure I agree with everything here. I run A7s (not R7s) for autocross and drive my car to and from the events on the Hoosiers. Granted, it's about 20 minutes away as opposed to 110 miles. I once calculated the mileage you get from a set of A7s and it's significantly less than 100 miles. But, those are some pretty rough miles. I don't believe street driving impacts wear all that much, but it would depend on a number of variables (speed, temperature, driving style). I don't believe you are eating up any heat cycles driving the car on the street. The tires aren't getting to the target operating temp from a relaxed drive to the event.

I average about 12 events on a set of tires before they're shot. I don't drive fast, nor do I try to dig in on the corners when I'm heading to events. I'm not advocating for you driving on your Hoosiers, I'm just simply sharing my experience. If I had the option to trailer my tires or have them shuttled, I absolutely would.
 

·
Registered
Joined
·
379 Posts
I've put a lot of street miles on R6s and on the Conti slicks and can tell you they wear just fine. They aren't getting hot enough to be sticky on the street and your aren't heat cycling them driving to and from events. The downside is they are fragile compared to normal street tires so the possibility of getting a flat from road debris, etc.. is much higher. YMMV (literally).
 

·
Registered
Joined
·
43 Posts
Discussion Starter #13
I'm not sure I agree with everything here. I run A7s (not R7s) for autocross and drive my car to and from the events on the Hoosiers. Granted, it's about 20 minutes away as opposed to 110 miles. I once calculated the mileage you get from a set of A7s and it's significantly less than 100 miles. But, those are some pretty rough miles. I don't believe street driving impacts wear all that much, but it would depend on a number of variables (speed, temperature, driving style). I don't believe you are eating up any heat cycles driving the car on the street. The tires aren't getting to the target operating temp from a relaxed drive to the event.

I average about 12 events on a set of tires before they're shot. I don't drive fast, nor do I try to dig in on the corners when I'm heading to events. I'm not advocating for you driving on your Hoosiers, I'm just simply sharing my experience. If I had the option to trailer my tires or have them shuttled, I absolutely would.
I'm certainly planning A7s, I think that cajundaddy was just talking about his track experience with R7s. I have a friend who trailers his GT3 and has 15 events on his current set. He also brought up the fact that changing wheels at the event might take some of the fun out of the event. I think that I'll buy a set next spring and drive to events. Depending on how that works out I might invest in the hitch/tire trailer. I'll report back just in case anybody's interested.

Thanks all.
 

·
Registered
Joined
·
583 Posts
Yes, my experience was with R6 and V710 tires in the past. I have not run the A7 and it might be a better choice for AX with occasional street driving. I did lose a few tires to road debris which killed the weekend event for me and I am a perennial tight wad and HATE running expensive racing rubber unless points are involved. Gotta have that $50 Championship series trophy you know...
 

·
Registered
Joined
·
939 Posts
Maybe we should start a Hoosier thread to address the drive to the site and home for those using A7's. We can address suspensions issues, wheels size, footprint width vs wheel width etc. I think that would be fun as threads like this one gets diluted by members who want to share, but have no idea about the whole setup necessary to running these tires.
 

·
Registered
Joined
·
939 Posts
So, I did buy a set of A7's and drove them to Packwood for a PCA weekend event, about 60 miles each way. The drive to Packwood on Friday was a non event with the Hoosiers, like driving RE71R's but not as noisy. The weather on Sat was a fine mist most of the morning session, which was my group. Even with the mist, tires performed better than RE71R's. So far, they are worth the expense. The setup was 29 lbs PSI cold, #6 settings from stiff on the Ohlins and #8 in the rear. After the 3rd run, stiffened the f shocks to #3 from stiff and left the rear at 8 found out that this difference in shock stiffness caused my nose to lift or rear to squat. On Sunday, clear skies, 80 degrees, left f at 3 and rear to 4. This was slightly too stiff for the bumpy course even with Hoosiers. Thinking that the best combo would have been 5 f and 7 r. recorded in notebook for next year. Mostly neutral balance, throttle steer in 180 degree corner. A little more tire roll in f than the rear on outside shoulders even with -2.7 camber f, not much roll on the rear with -2.5 camber. I could have used more mid range HP as I found my foot planted wishing for faster engine/torque response with these tires.

After my drive home, I used a steel brush/scrapper to remove the small rocks that were embedded in the soft rubber. I asked about heat cycles when using Hoosiers as travel tires, older guy who has used them for years, said not to worry if you keep your speed and mileage down. My next event is about 30 miles away in Sept. Hopefully no rain. I have my RE71R's or a new set of Michelin PS4's ready to go as rain tires.

Quote from Hoosier A7 tire care and safety guideline re air pressures for autocross, rear engine, independent rear suspension cars, extreme care should be taken when tuning at reduced pressure.
When tuning at reduced pressures use the following formula to determine the minimum safe pressure: Divide the total vehicle weight, including fuel and driver, by 100 to arrive at the minimum safe pressure. Example: Your car weighs 2750 lbs. as raced.
The minimum safe (cold) pressure is 27.5 p, So, my next outing will be Bremerton and cold pressures will be 33 to start and 35 to run.

Pic's 1&2 are Titan 7 TS-5/Hoosier A7's; Pic 3&4 are Signature SV-104/RE71R's; Pic 5 OEM/Michelin PS4's all tires are 255/35/18 F and 275/35/18r. Titan7 TS-5 are 9 in f and 10 in r Forged monoblock 17.1 lb f and 18.5 lb r. Signature Sv104 are 9 in f and 10 in r Forged monoblock 18 lbs f, and 19 lbs r.

DSC_0016.jpg DSC_0012.jpg DSC_0056.jpg fullsizeoutput_2dfb.jpg DSC_0009.jpg
 
1 - 16 of 16 Posts
Top