Tire falls off cliff

[Fabman]

Yes I was just thinking I might steal a cylinder from work and see how that does. I have about 6 big ones sitting at home in case we had Covid during the peak and hospitals were maxed out.

Medical grade everything is super pure.

 

[ajaquilante]

Everyone's setups are different. Some cars can make the A7's work, some can't, Some cars have a hard time getting the R7 up to temp, while others must use them. Shocks, springs, driving style, swaybars, camber, bushings, track, temperature, age of surface, etc...So many variables play into it. Racing is a sum of experiences. What works for one, doesn't always work for someone else. If you are burning up A7's, run the R7. Before the '18 Runoffs, I ran a Spec Mustang on a testday at Sonoma, the R7's were only a few tenths slower than the A7's on that car because of the suspension parts required. It beat the piss out of the A7 and had overworked the tire before you finished the lap, meanwhile my (at that time GT2) Mustang took 1.5 laps to get the tires up to temp for the ultimate lap on A7's for qualifying.

Another example, T2 cars at Homestead a few years ago(Rob's favorite car and track combination) a customer car with a set of JRZ shocks would destroy the tires vs a customer car on Penskes being much kinder to the tires while going faster.

Are A7's a wise choice for HPDE in 100 degree weather, no. Do I race on them in the summer at NJMP in 100 degree temps, yes. Are they shredded after a race, depends how you drive. Would R7's be a better choice to be able to use them in multiple races, depends how competitive you want to be in another of those races. I posted a picture last year about destroying a tire because I was trying to collect data, so I wasn't kind to it. The next day the tires were fine after a couple setup tweaks and driving like normal.

I jokingly refer to the tire testing scene in Days of Thunder quite often, but its the truth... You only have 4 points that the car is in contact with the track by which all movements are applied through, you need to manage them well.

 

[bob]

Well, at some threshold ..say 220 degrees, the water in the right rear tire is heating up at a faster rate (trying to turn to steam, which under pressure, This causes a massive increase in pressure,

In any case 15% is my spec for humidity in tires, I will not run more than that.
For this reason I work through a proprietary method of removing water from the tire.

Are implying liquid water in the tire at standard temperature and pressure to start and that boiling off at temp radically increasing pressure? If all you have is humidity in the tire that should follow a standard curve as temps and pressures rise so nothing radical. Liquid water gets in tires at room temp when tires are mounted with soapy water as lubricant.

I mount and balance myself and my tire machine is an old air driven Hunter TC325. I mount with hairspray not soapy water like the hoo hoo guys do at the track. My tires do not spin on the wheel but they can and do sometimes when hoo hoo mounts my tires when I am traveling. Hairspray is magic! First it acts as a lubricant when wet to get the tire on the wheel. Then it acts as a glue when it drys to prevent the tire from spinning on the wheel. I will dismount with soapy water but then clean and dry my wheel. I will seat the bead with shop air. There isn't much water from mounting with filtered shop air. That said I have tried in the past to mount with hair spray and seat the bead with anhydrous nitrogen from a large D cylinder like we bring to the track. I just did not see any difference and it is expensive to exclusively use nitrogen. Maybe I'll have to revisit this issue. You need a way to remove water if the tire monkeys are slathering the tire with soapy water to mount. But you don't need to remove water from the tire if you never get water in the tire.

 

[bob]

I think this is the key. The A7 is fast, but I think needs a smooth, delicate driving style to last a race session without completely overheating.

I'm not smooth with it on the S550 because when I start to lean on the car I go into saw the wheel mode and that just makes matter worse. A driving coach for one of my friends came over to my garage and asked me if my tires were grossly over inflated because he was watching me understeer on corner entry and oversteer on corner exit at every turn. At this point my car is back in Cali and home on the lift. I'm resetting rideheight, corner weights and ensuring alignment then go testing before I race again. I have to get some data.

 

[JDee]

I'm not smooth with it on the S550 because when I start to lean on the car I go into saw the wheel mode and that just makes matter worse. A driving coach for one of my friends came over to my garage and asked me if my tires were grossly over inflated because he was watching me understeer on corner entry and oversteer on corner exit at every turn. At this point my car is back in Cali and home on the lift. I'm resetting rideheight, corner weights and ensuring alignment then go testing before I race again. I have to get some data.

Ever consider getting a known hot shoe (aka damn good racer, not a driver coach) to take your car out for a few laps and get some feedback from them? Might learn a lot from a proven pro. Let him try it your way, then see what changes he might suggest, and let him try it again with those changes. Might cost you some $$ for the advice, but might be the best money you ever spent, especially if you have data recording going on.

 

[blacksheep-1]

Are implying liquid water in the tire at standard temperature and pressure to start and that boiling off at temp radically increasing pressure? If all you have is humidity in the tire that should follow a standard curve as temps and pressures rise so nothing radical. Liquid water gets in tires at room temp when tires are mounted with soapy water as lubricant.

Yes, although, because of the increase in pressure it won't "boil off" because the pressure will increase the boiling point, but it is inconsistent at best because, due to the tire temps fluctuating, the pressure is all over the place, also, the techs at the track don't use water to mount tires either. Keep in mind, when you mount a tire in 90% humidity weather, you have a base volume in that tire of 90% humidity air, regardless of what you put in it from the compressor.

 

[bob]

Yes, although, because of the increase in pressure it won't "boil off" because the pressure will increase the boiling point, but it is inconsistent at best because, due to the tire temps fluctuating, the pressure is all over the place, also, the techs at the track don't use water to mount tires either. Keep in mind, when you mount a tire in 90% humidity weather, you have a base volume in that tire of 90% humidity air, regardless of what you put in it from the compressor.

That all makes sense. This makes a great case for A/C for the tire guys because A/C pull humidity out of the air.

 

[Bree789]

OK, Bob, Chris and Mad Hatter, here's the red meat.

Let's say you have a car, running on a (mostly) left turn road course, so the right sides are going to get hotter. Your tires are saying from between 180 to 230 on the pyrometer, it's a hot day (90 plus). So the car goes loose, but when you come into the pits the tires are all in their target pressures plus or minus .5psi.
You make a bunch of changes, the car starts tight, goes loose, so you head down the adjustment rabbit hole time and time again..
But what is really going on?
Well, at some threshold ..say 220 degrees, the water in the right rear tire is heating up at a faster rate (trying to turn to steam, which under pressure, it won't actually do) than the surrounding air, or nitrogen, whatever you happen to be using. This causes a massive increase in pressure, causing the car to go loose but... as the tire goes under 220 on the cool down lap and the drive through pit lane, the temperature goes down, with resulting pressure, and all is apparently normal in tire world. Leading you to make a bunch of unnecessary changes in what is, in reality, a great handling car.
Have I seen this? well sort of, I'm not sure anyone has actually seen it, but I'd bet a bunch of people have actually experienced it, and not known about it, and believe me, I have experienced it in the worst way at the worst time.
In any case 15% is my spec for humidity in tires, I will not run more than that.
For this reason I work through a proprietary method of removing water from the tire. There are several ways to do that for the local guy, the easiest and simplest is to just use several water filters in a row on your compressor when inflating the tires, that should be a decent way to control water coming out of the compressor. Along those lines, nitrogen is also pretty predictive when it come to expansion, but.. that doesn't guarantee that the nitrogen is not bad either, because people who half ass stuff are worldwide. So it pays to sample your tanks when you replace them. With regards to "dehumidified air" I've heard of it, supposedly seen example of it... and it is not below my spec.
So, with regard to the OP, there are a number of reasons that you may have experienced these issues, I will still put my money on an A7 in almost every application, but details count, and this is just another detail than can have extensive, and across the board results in your pressure management.
At Daytona last year the track and temp was hotter than usual, several teams had tires blown off their cars in the banking, I would put money that those tires had water in them.

Hello sir, I am very interested in implementing this 'dry air' practice at the track. In my most recent HPDE event I had severe to mild understeering issues. I chatted with a few TMO members and at the moment, boiled the possibilities down to worn out components such as tires and LSD clutches; however, thinking about the physics behind the negative effects of high %RT inside the tires, this argument makes a whole lot of sense to me. Regulating the humidity inside the tires to <15% also seems very straight-forward to achieve (i.e. buy a quality drier filter system for my compressor and take a tank of that compressed air to the track to adjust psi on site); This will also allow me to target setup from a more 'tabula rasa' approach. I also just purchased a longacre psi gauge (the one with .2psi definition) per your comments on another thread.

The only thing that still baffles me is: how do I determine the ideal hot pressure settings for my particular situation?

Usually I just go by avoiding sidewall wear and driver feel, but I don't know how those two intermingle with alignment settings (such as camber and toe). At the moment, my only tire instruments are a tire pyrometer, a good tire pressure gauge and chalk. With regard to the pyrometer, I believe that up to a ~40F spread around 200F is acceptable, depending slightly on tire, of course. I have yet to use all three, so all I've done till this point during past events is to use my eyes to make adjustments.

 

[TorqueAholic]

I think this is the key. The A7 is fast, but I think needs a smooth, delicate driving style to last a race session without completely overheating. As someone else said above, the A7 race strategy is to pull a gap on the field in the first several laps, then try to hold on as it gets greasy. Use the grip of the A7 over the R7 to maintain momentum mid-corner for a higher apex speed, but don't overdrive the braking zone and turn-in, and be gentle rolling in the throttle on exit. Try using less trail-braking on entry, which means you may have to back up your braking a bit.

On the other hand, if you like your driving style, maybe the R7 is the Hoosier tire for you on a Mustang. Yes, the peak grip is less than the A7, but you may turn faster average laps over a session because it isn't overheating and falling off as much.

Agreed, my experience was that actually both the A7 and the R7 were not very tolerant of over-driving, especially on hot days. The R7 less so but I don't recall getting much more than 1 lap of over-driving. Honestly, the overly aggressive laps were rarely the fast ones anyway.

 

[Bill Pemberton]

Having run both A7s and R7s during a race, I would recommend the R7s to most folks going forward as the price increase with Hoosier over the past two years has been substantial and the R7s definitely last longer. Like TorqueAholic neither tire enjoys hot weather and that was one reason I went with BFG gforce R1Ss for a few years, as they did not warm up as quick, but in a 30-35 minute race they stayed more consistent. They were also cheaper and lasted longer, but onward and upward as BFG decided to bail on them again and they are not available in wider sizes. The way things are going with NASA many drivers will be switching to Toyo RRs because they get such a huge benefit on both weight and HP, and again they last longer.

Don't get me wrong, I still think Hoosier is the " King of the Hill " but costs, certain race Series , and their short track life is likely to eat into their Sales. That said , depending on what you plan on running, for instance Time Trials, the A7 or R7 may be
your choice for 2-5 quick laps and challenging for the win.

Living in the Midwest Hoosiers do not like it really hot, but watch out if it is cool, they dominate when the climate is pleasant.

 

[blacksheep-1]

Well, Im a die hard A7 guy but for track days, I would pick out a tire that has some consistency over it's Hopefully) long life cycle, regardless of how well it actually stuck to the track. If you are competeing w2w, or time trialing, the A7 is, IMO the answer 90% of the time.

 

[blacksheep-1]

Hello sir, I am very interested in implementing this 'dry air' practice at the track. In my most recent HPDE event I had severe to mild understeering issues. I chatted with a few TMO members and at the moment, boiled the possibilities down to worn out components such as tires and LSD clutches; however, thinking about the physics behind the negative effects of high %RT inside the tires, this argument makes a whole lot of sense to me. Regulating the humidity inside the tires to <15% also seems very straight-forward to achieve (i.e. buy a quality drier filter system for my compressor and take a tank of that compressed air to the track to adjust psi on site); This will also allow me to target setup from a more 'tabula rasa' approach. I also just purchased a longacre psi gauge (the one with .2psi definition) per your comments on another thread.

The only thing that still baffles me is: how do I determine the ideal hot pressure settings for my particular situation?

Usually I just go by avoiding sidewall wear and driver feel, but I don't know how those two intermingle with alignment settings (such as camber and toe). At the moment, my only tire instruments are a tire pyrometer, a good tire pressure gauge and chalk. With regard to the pyrometer, I believe that up to a ~40F spread around 200F is acceptable, depending slightly on tire, of course. I have yet to use all three, so all I've done till this point during past events is to use my eyes to make adjustments.

Im just an old school southern redneck stock car guy so I don't know who Tabula Rasa is, but I'd like to meet him.. 40 degrees across the tread is not uncommon, also, unless you are really pushing the car with tire temps over about 190, the humidity may never come into play. Instead of rehashing everything again, Im going to post several links that I think will help you.

Tire pressure

How much does tire pressure affect the way a car steers?Right now I am running 265 front/ 295 rear tires ( Pilot Super Sports ) the car has a tendency to push through corners. Right now I am comfortable with that because I am still learning.My last HPDE event, my instructor told me to keep...

trackmustangsonline.com

Recommendations for cold and hot tire pressures Goodyear Eagle F1 Supercar 3R

I will be running the 3R's for the first time on my GT350R. What cold and hot pressures are folks using?

trackmustangsonline.com

tire pressure mapping

I was asked on a FB page to explain how I do this so I'm sending them here. It's quite cumbersome to explain on FB. I have been fortunate enough to work with some very talented people over the years who have brought me along. They NEVER gave me the whole answer but expected me to figure it out...

trackmustangsonline.com

driver comparisons vs tire pressure

I had an opportunity this weekend to run tires for several drivers, not getting into who, what and when, and if you know, please don't post them, ( thanks ahead of time) but it was pretty interesting to see the results of their driving styles. Generally, the higher the tire pressures, the harder...

trackmustangsonline.com

 

[Bill Pemberton]

Don't believe Blacksheep is just an old Florida Redneck Stock Car guy as he has worked on some of the best Sports Car teams in SCCA, IMSA, etc. in the US. He actually downplays himself ( hell, he is almost modest at times, ha ) but working on MegaDollar Mercedes IMSA GT3/GT4 beasts , GTD Aston Martins, Michelin Challenge Mustangs, SCCA National Champion Mustangs, Corvettes, etc. let you know he be knowing his stuff -----------rumor is folks don't hire Tire Gurus who are just good ole boys, they have to also be Guru Old Boys!!

BS1 is the tire guru of TMO and though he will defer to others on occasion concerning street DOT Comp. rubber , he is the guy on this site who gets paid to rotate rubber!

 

[Mad Hatter]

Had to look it up...

Tabula rasa is the theory that individuals are born without built-in mental content, and therefore all knowledge comes from experience or perception....

I have to agree with Bill. Am sure the A7 is the faster choice, but they are lasting us way fewer cycles then the R7. Have brought several sets of A7's down for other cars and they have been lasting about half as long as a R7. I have been getting pretty close to 8 track days out of my R7 tires.

 

[Bill Pemberton]

No real argument here, Mad and I just don't have the bucks to purchase rubber as often as the folks Blacksheep is often there to support, but after saying that , if you have the bucks, are super competitive , etc. A7s are money.
With Mad, I, and others A7s may be money, but we are hammering our Credit Cards and we go with an R7 since it makes more cents - and sense!!

 

[Bree789]

Im just an old school southern redneck stock car guy so I don't know who Tabula Rasa is, but I'd like to meet him.. 40 degrees across the tread is not uncommon, also, unless you are really pushing the car with tire temps over about 190, the humidity may never come into play. Instead of rehashing everything again, Im going to post several links that I think will help you.

Tire pressure

How much does tire pressure affect the way a car steers?Right now I am running 265 front/ 295 rear tires ( Pilot Super Sports ) the car has a tendency to push through corners. Right now I am comfortable with that because I am still learning.My last HPDE event, my instructor told me to keep...

trackmustangsonline.com

Recommendations for cold and hot tire pressures Goodyear Eagle F1 Supercar 3R

I will be running the 3R's for the first time on my GT350R. What cold and hot pressures are folks using?

trackmustangsonline.com

tire pressure mapping

I was asked on a FB page to explain how I do this so I'm sending them here. It's quite cumbersome to explain on FB. I have been fortunate enough to work with some very talented people over the years who have brought me along. They NEVER gave me the whole answer but expected me to figure it out...

trackmustangsonline.com

driver comparisons vs tire pressure

I had an opportunity this weekend to run tires for several drivers, not getting into who, what and when, and if you know, please don't post them, ( thanks ahead of time) but it was pretty interesting to see the results of their driving styles. Generally, the higher the tire pressures, the harder...

trackmustangsonline.com

Excellent! Thank you for the informative references. I shall study this when I get home today. I am relatively new to the track world so beggining with a solid foundation definitely is a great way to start for me. Hahaha...I did not want to get too philosophical but tabula rasa means clean slate. It's an interesting phrase used to express a new beginning.

 

[blacksheep-1]

I think he has a sister named Tabitha Rasa

 

[Fabman]

I have raced and qualified on both.
Being an old stock car guy myself I know how to take care of my tires on track, so I'm not unduly rough on them.
What I have found in my experience is that the A7 is much faster out of the gate but slows down more quickly. I get my fastest laps in the first 2 or 3 laps. After that they stay about the same for a bit and start start to decline and I spend most of the race under driving the car to keep the tires underneath me.
The R7's start out slower but the lap times are more consistent and I feel like I can push the car harder so I end up going faster for a longer period of time.
Now some of that might be stupid me worrying too much about wear and maybe I should just drive the crap out of them and not care, but the price tag has me a little too gunshy to try. As soon as they start feeling greasy my instinct is to back it down a bit and save the tires. In the scca season finale' at Thunderhill I ran my best times on the A7 but after about 4 laps the lap times started to vary. The next day I ran the R7's and while my best time was 2 seconds slower, I ran the whole race within 1 second and the average lap time was 3 seconds faster. More testing this year and we'll see what happens.

 

[blacksheep-1]

Paving tracks once in awhile helps, there's an old saying, " old track, new tires, new track, old tires" you get a lot more mileage out of older rubber at newer tracks. Indy and Barber, really aren't that horrible on tires, Sebring and Sears Point on the other hand... let's not even discuss Homestead.
I'm kind of a fan of spec tires, to a point. I ran open tires in karts across the southeast and the Caribbean back in day, I ran Dunlops exclusively, but I kept a set of Bridgestones in the trailer just because.. on some days, you weren't gonna beat a Bridgestone. The problem with spec tires is that everyone wants to run hard compounds for longevity, but that doesn't always work. At indy, Conti actually made the tire stickier to prevent blistering. ( new track..etc). At Daytona the GT cars had 2 compounds available, but there were so many caveats placed on them by Michelin that I'm not sure it mattered much, plus they could read your telemetry, which kind of sucks.
The old Contis ( Hoosier) was a pretty good dependable tire, so is the Michelin but at a much higher cost, but it is also quicker IMO.

 

[Fabman]