7
AutoX Beginner
- Thread starter uvasteven
- Start date
aroundomaha
Ready to race!
- Location
- Nebraska
Amen to that! I added an H&R 26mm RSB even though tires would have made more sense. But it was already October and past season for Summer tires. I've enjoyed the RSB every day and have zero regrets, especially since I don't have an LSD.
An electric tire pump, pressure gauge, 2 gallon garden sprayer (especially if non-PP) to cool the front tires, a hat, sun screen, bug spray, small ice chest with cold drinks and food.
Give details on car stepup and tires so we can give you some starting points for tire pressures.
Totally stock 2019 so I have the performance pack. Stock all seasons.
You'll want about 38 psi front and 44 rear to start on a completely stock car. Probably don't need the sprayer on a set of AS with PP.
If you need more rotation, increase rear pressure. If too loose, decrease. Go in 1 psi increments when you make a change. You'll need to maintain pressures between runs. Be sure to reset your pressures at home once tires cool later in the evening, so you don't end up with low pressures driving around on the street.
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"38 psi front and 44 rear"... is that cold or hot pressures? I ran 38/42 cold on some iffy all-seasons, I had trouble recovering grip when I started to slide. (That's more due to the iffy all-seasons.)
Normally, 37 PSI cold will heat up to well over 38 PSI hot. Should I reduce my front tire pressures to 38 hot, and later increase back to 37 cold?
If so... the autocross tire pressure in front is lower than the recommended pressure for daily driving? I've checked my sidewalls, the rollover appears to be about right.
Normally, 37 PSI cold will heat up to well over 38 PSI hot. Should I reduce my front tire pressures to 38 hot, and later increase back to 37 cold?
If so... the autocross tire pressure in front is lower than the recommended pressure for daily driving? I've checked my sidewalls, the rollover appears to be about right.
In autocross, you bleed down to the correct pressure between runs, so it's both the hot and cold pressure. If you're only getting 1 psi gain, you live somewhere cold or you're still pretty new to autocross. I see a couple psi gain each run until tire get fully up to temp. I'm in Florida, so we get huge pressure gains.
I only autocrossed once on the stock Hancook AS's and I also had the Bridgestone AS's on my 19, so my recommendations for AS tire is based on the Kooks,on a stock car, you'd need more pressure for the Stone AS's, because they have a softer sidewall.
I run 32 psi front, 33 psi rear if temps are cool or track is dirty, 32 psi front, 36 psi rear if it's hot or there's a lot of grip. Also, the number of heat cycles on the tires matter. Once I get 6 or so heat cycles in the tires, they tend loss a little grip and the car gets slightly loose, which I compensate by reducing the rear split. That's on 245/40 17 RE71R's, if you run even a different 2OO TW, you'll need to adjust to the tire, conditions, and number of heat cycles. SUR4G's take 2 full heat cycles before they have decent grip, the car will be loose, then the third event, bam, massive understeer. They also take longer to heat up, so they'll be loose first couple of runs, then, tighten up. All of this is based on an old asphalt surface and higher grip asphalt or concrete will be different.
Tire pressures aren't a static set and forget, one size fits all kind of thing.
Wow, very low pressures compared to the mfg. suggestion, but the RE71R's are very stiff compared to a street tire, so maybe that has some effect? Plus, these are 17", vs the stock 18" that I run. So, start with 38/44 cold, then bleed down to that same pressure as the day goes on? I have no idea what the hot temps are yet, I've never checked after the racing starts. These tires are about done, I'm not sure if I feel like wearing down the last bit of rubber on one more event, or replacing them with Michelin PS 4S's. (Still street tires, not track day tires, but they should be a huge step up from the all-seasons, in feel and performance.) Our pavement is old, with some dirt and gravel, and some holes and bumps that can upset the grip. No points this year, so every run is just for fun (and learning), not for glory and points. I play for fun, anyhow. I was still 3rd in class last year (but not a "close 3rd", so the new tires and working on my driving skill are my next steps).
I'd keep the fronts are 38psi unless you're seeing excessive role over on the side walls, then increase a little if necessary. If you do, then increase the rear to maintain the same split if the car is handling well. You increase the split to get more rotation, decrease if car is a little loose. PS4S are a fantastic street tire, but they do not like to be heat cycled. If you daily them and do one event a month, by 8 months in, you'll be at half tread depth, but they'll be heat cycled out and completely useless. You'd honestly be better off with something like the Indy 500. They're cheap and don't seem to heat cycle out like the PS4S, but you will give up some grip when new in comparison. If you're new to autocross, it won't make a difference though, you're the limiting factor at this point, not your tires. End of last year a young guy showed up with a FiST on worn out AS's. He asked me to ride with him and I gave him some pointers, but I asked if I could take a run in his car. I was 3 seconds faster than him and those tires were absolute toast. No tire is going to give you 3 seconds.
And you're exactly right about my pressures for the RE71R's. The 17 in size and stiff sidewalls allow for lower pressures. I ran 26 psi with them in the Miata.
I just re-read the test of the Indy 500s at Tire Rack:
https://www.tirerack.com/tires/tests/testDisplay.jsp?ttid=235
"The stiffest ride of the group and some mild and unobtrusive tread noise round out the Firestone's on-road performance." It came in 3rd place overall, "Still a good tire, but the competition has caught up."
I'm wondering how a manufacturer like Michelin could make such a great tire, used on so many high performance cars that are tested to the limits by the car magazines, and not have those tires hold up to the (relatively modest) heat generated by autocross? I've never heard the magazines declaring that the Michelins on their Porsche or BMW or etc somehow lost grip partway through the evaluation period.
But, you are right, the Firestones are $200 cheaper a set.
But, in Car and Driver's 2017 test of "Five sticky summer tires", the PS 4S came out on top, a perfect 40 on the autocross test, perfect 10 on steering feel, and no mention that the heat affected these any more than any other tire.
https://www.caranddriver.com/features/a15092360/2017-performance-summer-tire-test-feature/
I'm tempted to spend the extra money on the top-scoring Michelin 4S, and trust that the engineers have the knowledge to engineer their top tire to deal with heat. If I decide to run it hard on a race course all day, then maybe I'll think of a getting a set of track-day tires. Right now, I'm looking forward to getting rid of the all-seasons and seeing what a true high performance tire is like.
https://www.tirerack.com/tires/tests/testDisplay.jsp?ttid=235
"The stiffest ride of the group and some mild and unobtrusive tread noise round out the Firestone's on-road performance." It came in 3rd place overall, "Still a good tire, but the competition has caught up."
I'm wondering how a manufacturer like Michelin could make such a great tire, used on so many high performance cars that are tested to the limits by the car magazines, and not have those tires hold up to the (relatively modest) heat generated by autocross? I've never heard the magazines declaring that the Michelins on their Porsche or BMW or etc somehow lost grip partway through the evaluation period.
But, you are right, the Firestones are $200 cheaper a set.
But, in Car and Driver's 2017 test of "Five sticky summer tires", the PS 4S came out on top, a perfect 40 on the autocross test, perfect 10 on steering feel, and no mention that the heat affected these any more than any other tire.
https://www.caranddriver.com/features/a15092360/2017-performance-summer-tire-test-feature/
I'm tempted to spend the extra money on the top-scoring Michelin 4S, and trust that the engineers have the knowledge to engineer their top tire to deal with heat. If I decide to run it hard on a race course all day, then maybe I'll think of a getting a set of track-day tires. Right now, I'm looking forward to getting rid of the all-seasons and seeing what a true high performance tire is like.
If you're only getting modest heat in your tires at autocross, you aren't trying hard enough. But seriously, any tire has a limit where they overheat and get greasy or start chunking off.
Personally, I would always go for cheap daily tires (Sumitomo HTR AS P02 "ultra high performance all season" are my preference) and get top-tier tires for autocross and track. Any kind of a "comporomise" 240-320tw tire for all purposes is just a waste, IMO; it's a waste of money using tires you daily on for competition when you wear them out faster than you otherwise would just on the street, and it's a waste of competitiveness and FUN using lesser tires for competition.
It's a modest investment to get a 2nd set of wheels, but I would highly recommend doing so and at least getting used take-off top-tier tires for autocross/track if you don't want to immediately go for new tires.
This. I use Falken FK510's on the street, RE71R'S for autocross.
If you're going to autocross your street tire, the other tires on the Falken's class don't have the side wall stiffness you need for a FWD autocross car.
And I'm speaking from experience with the Michelins. They're great new, they'll heat cycle out at half tread depth. Autocross crossing a fwd car puts a lot of heat into the tires. I melted the center caps of the Konig Runlites I used for GS. You get as much heat into the tires from the brakes as you from the track.
The Indy's are better than you are right now, have the sidewall stiffness you need, will work well on a fwd car, and are cheap. They're a great tire for your first year. Take what you save over the PS4S and buy yourself a 26mm H&R rear swaybar and some Moog endlinks. You'll thank me later. After your rookie year, if you still are autocrossing, then it's time to get a street tire that's great in the rain and a dedicated set of wheels and 200tw tires, a jack, electric impact, torque wrench and use your 200tw for dry events and you street tires for wet events.
I've been autcrossing for 35 years, what I'm telling you what you need to know as a beginner. If you want to do the Michelins, it's not a bad choice, they're a fantastic tire, they just aren't going to make you any faster and they're expensive and you'll kill them with heat. Sometimes you just need to learn things for yourself. If that's the case, go for it. Tire Rack will appreciate the business, but remember, they test with a RWD car and it's a single day test, not 6 or 7 heat cycles. I can't begin to tell you how bad the Michelins were once they heat cycled out, and that was on a 2400 lbs rwd car. It was understeer on corner entry, oversteer on the way out after 7 events. I'm an experience autocrosser and live in Florida, so it's probably worst case for tire heat, but again, you won't be any faster with PS4S than you will be with Indy's for the first year.
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I live in the snow belt, so my spare wheels go for a good set of snow tires. I am currently on the Sumitomo HTR AS P02 tires, a decent, cheap all-season. But, even the best all-season tires (Contis, at least from the standpoint of wet/snow safety) are not up to the same level as an average top-tier summer tire. Also, the summer temperatures and track temperatures in Cleveland aren't the same as in Florida, so that may (or may not) help with the heat issue.
That's an interesting idea to take the money saved with the Indys and spend it on a sway bar. I find the H&R bar is much more money than the Eibach, which is only slightly slimmer (but hollow?) I know the H&R is popular, but I've never seen a direct comparison. The Moog end links are "because you have it all apart anyway, and they will last" I'm assuming, not because they would help with the handling directly.
Going with cheap everyday tires to maximize my autocross tires... I'm not sure that would work *for me*. My car is a daily driver that I autocross, not an autocross car that I drive daily, if you get my meaning. That is... the autocross part isn't as important to me, it's just fun. It may be different for you, of course, that's fine. But, I'd rather have the steering precision and handling of the Michelins every day, and give up bit of time on the autocross (vs. the track-day-focused RE71R's).
That's an interesting idea to take the money saved with the Indys and spend it on a sway bar. I find the H&R bar is much more money than the Eibach, which is only slightly slimmer (but hollow?) I know the H&R is popular, but I've never seen a direct comparison. The Moog end links are "because you have it all apart anyway, and they will last" I'm assuming, not because they would help with the handling directly.
Going with cheap everyday tires to maximize my autocross tires... I'm not sure that would work *for me*. My car is a daily driver that I autocross, not an autocross car that I drive daily, if you get my meaning. That is... the autocross part isn't as important to me, it's just fun. It may be different for you, of course, that's fine. But, I'd rather have the steering precision and handling of the Michelins every day, and give up bit of time on the autocross (vs. the track-day-focused RE71R's).