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Thread: More durable/affordable tire option?

  1. #61
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    Quote Originally Posted by michaelmosty View Post
    I am very well aware of the heat cycling out issue. To me, that is just a question all of us have different answers to. How much do you want to spend? I have raced either every event or every event -1 in all my 13 years of racing. I have never used more than 3 sets of tires / season.

    To keep racing as cost effective as possible for me I choose the events I want stickers vs the events I don't have the ability to. I raced MSRH with the same tires I ran Nationals. My plan is to use those tires for inverts at MSRC and then put stickers on for qual and Toyo races. I will then finish MSRC with 4 heat cycles on the stickers and then use them for COTA.

    Do I think I am losing time vs bringing stickers to every event? Absolutely. Is it worth it to me to bring stickers to each event? Absolutely not?
    All of us have different personal preferences for what we are able to spend for racing.
    Quote Originally Posted by michaelmosty View Post
    I agree Richard but this same tire situation is going to be present with any other race group that runs a race tire. It doesn't matter if you are CMC, AI, SM, GTS, etc, whoever shows up with stickers at every event is going to have an advantage.

    Is it because CMC is more of a budget series? Heck, I am on a tight racing budget and couldn't even bring rain tires to Nationals when the forecast called for rain all event.
    I totally understand where everyone is coming from on a budget stand point.
    My aim for starting this thread was totally centered on budget. I wanted to start the discussion about 200 TW street tires because I think if we can have as much fun as we do and lower the cost per event we all win. The endurance racing series that are gaining popularity that run them have something very right in their formula, those events are serious fun and tires are way less of a factor. I think the alure of low cost is something that keeps people showing up and sticking around in those series.

    I agree with the sentiments that we don't want the tires to be the deciding factor in everyone's season. Part of racing is car management, I understand that -- but none of us are going to run Daytona and the cars tend to create enough reliability opportunities that taking new tires out of the performance equation that is CMC would be a net benefit to the whole group (in my opinion).

    Quote Originally Posted by ShadowBolt View Post
    Michael and Kevin using older tires for non Toyo races is fine but like Richard I want to run as fast as possible in every race. Since I only run two races per weekend one of those will not be a Toyo race. I do not want to run tires that are even half a second slower per lap. Different strokes for different folks. I would like a tire that is slower and would not change from new to corded. I just don't know if there is such a thing.

    JJ
    Quote Originally Posted by Supercharged111 View Post
    Maybe pre cycled out tires are the answer here.
    They just turn to such unpredictable junk. I'll take a slower predictable street tire all day over a 15hc RR rock.

    Quote Originally Posted by ShadowBolt View Post
    What is the difference in the RT615K and the RT615K+?

    JJ
    New compound -- better for track driving. Like i said previously, the 615k+ is the Spec Vette tire choice and those guys spoke positively about them. How that is not a direct comparison has been highlighted elsewhere in this thread, but is a good data point from a standpoint of 'are these tires total junk or are they a possilbe option?'
    Daniel Records
    CMC # 34

  2. #62
    Soooooo lots of options but they all boil down to two options. Run 615+ or stay with the current format. I think everyone understands the facts at this point. Someone have a email distribution list for the Texas group? Happy to put together a survey monkey and send it out.

    If we want to wait on that for now we just need 5 to agree to be guinee pigs at Cresson. And then we can all review data. I would say that a part of that agreement would be to run the 615+s in every session to maximize the groups ability to look at time degradation during heat cycles.

    since I will not be driving I am happy to record subjective opinions on handling after each session from each driver and document it in one excel file so that it can be charted. Then we can pull the objective data, times both average and best, to see how they align with each other. That is about as complete as I can think of it.

    The combination of objective data combined with subjective opinions that are tracked throughout the weekend should provide really good feedback. We can do a survey monkey after that.
    Last edited by liquidroam; 02-12-2019 at 02:12 PM.

  3. #63
    Call me Opportunistic but all you CMC guys running the non spec tire are welcome to increase the AI car count by running with us. 9 entries would be nice for Toyo bucks

  4. #64
    Senior Member Carroll Shelby RichardP's Avatar
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    With a thought of changing from the spec tire, I thought I would put down some of my thoughts on the current RR’s. First, some relevant tire parameters:

    Life – I’ve found the current RR’s have a pretty long life. I regularly run tires that are on their fourth event (‘cause I get them for free). Josh has run sets well into their fifth event multiple times before they completely give up or cord out. In order to get them to last that long, you can’t flat spot them when they are fresh and you have to have reasonably good camber and balance. You also need to flip them on the rim, preferably after every event. Still, that’s a lot of laps for a race tire.

    Durability: Dan got a puncture at the last event but I think that’s the only time I remember having an issue. Also, there is a potential issue with the tread seam coming apart. We run the tires in the recommended direction at the first event and then ignore the direction for the rest of the tire’s life. Our team has only had an issue with the seam on one tire when it was new and that came with a serious vibration. Seems to be a pretty tough tire to me.

    Endurance: How hard can you push the tire in a session before the grip goes off? The biggest complaint about the 888 was that if you pushed it at all, it would get greasy and grip would vaporize. It was no fun to drive and almost prohibited on track battles. It was horrible for racing. In this respect, I think the RR’s are pretty amazing. You can abuse and over drive these tires and, for the most part, they seem to keep holding their grip. I think abusing these tires hurts their effective life but they hang in there. I think this is a critical parameter to an exciting race tire.

    Looking at that stuff, it seems like a great tire. I actually think it is. If someone was handing out fresh tires every race day, I think this would be a spectacular spec race tire. But, tires aren’t being given out and there are a couple of other critical parameters that make these tires not so good for a class that needs to run a set of tires in multiple events to make the budget work. In a class that is supposed to give each competitor equal grip from a spec tire, this tire has more variability than any other performance parameter.


    Heat cycling: This is a common term for the performance of the tire falling off after a certain number of track sessions. I see numbers all over the map of how many heat cycles people think these tires are good for. I’ve come to the conclusion that the term “heat cycles” probably isn’t the best terminology for these tires. It’s not that heat cycles don’t apply to these tires, it’s just that heat cycles aren’t all created equal. I think it’s more that the tire is capable of a certain amount of time at temperature. The higher the temperature, the less time you have. The number of effective heat cycles you get depends on how much abuse the tire sees. These tires tolerate over driving pretty well but it comes at the expense of reduced effective performance life.

    So why does the performance of the tire drop after use? Tire construction, materials, chemistry, and processing is very complicated and generally considered complete voodoo even by tire engineers. In the past, it’s been said that race tires effectively come as partially cured rubber. Further heating and distortion of the tire finishes up the curing process and the tire becomes harder. There is some thought that Toyo could process the tires differently and deliver them fully cured. In theory, this would lower their initial performance but make them more stable over their life. I’m not sure if that’s true but I sure would like to see it. I believe Toyo’s incentive to do that is low…

    Handling: I think this is one of the most fascinating aspects of this tire. I have heard so many times that popping on a fresh set of RR’s will cure all of the car’s handling issues. People love how these tires handle when they are new and hate how they handle when they are all used up. Changing the overall amount of grip can have a small effect on handling balance but it shouldn’t dramatically change the handling.

    I believe what is changing is the effective shape of the slip angle graph. The slip angle graph for this tire seems to have a pretty flat and wide peak on fresh RR’s. This wide peak allows good grip over a variety of slip angles and masks subtle balance issues and handling deficiencies. As more time/abuse is put into the tire, not only does the peak grip level dip down a bit, but the peak becomes sharper. This sharp fall off of grip past the peak quits masking issues and requires the driver to sense much more subtle inputs to keep the car near the peak grip level. The car is just flat harder to drive. The drop in performance depends not only on the condition of the tire but also the base handling of the car and the ability of the driver to deal with the sharper peak. If anyone has any further insights to expand or contradict this thought, I’d love to dig into it deeper.


    On a practical application of this knowledge, we’ve found driving through a handling imbalance is a bad idea with these tires. One event at Cresson had Dan with a bit of understeer early in the weekend. He thought it was tolerable and didn’t want me to change anything. A couple of sessions later, he had abused the front tires enough that the front tires were signing off and the understeer was now magnified to intolerable levels. We made changes every session that should have made the car an oversteering pig with no success. I didn’t catch a clue to what was happening until we got back to the shop and looked at the differential tire wear front to rear. Now I hammer on balance with Dan early in the weekend and we often end up changing rear springs or sway bars during the event to keep on top of it. When the engine runs, anyway…


    Richard P.
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  5. #65
    Quote Originally Posted by RichardP View Post
    With a thought of changing from the spec tire, I thought I would put down some of my thoughts on the current RR’s. First, some relevant tire parameters:

    Life – I’ve found the current RR’s have a pretty long life. I regularly run tires that are on their fourth event (‘cause I get them for free). Josh has run sets well into their fifth event multiple times before they completely give up or cord out. In order to get them to last that long, you can’t flat spot them when they are fresh and you have to have reasonably good camber and balance. You also need to flip them on the rim, preferably after every event. Still, that’s a lot of laps for a race tire.

    Durability: Dan got a puncture at the last event but I think that’s the only time I remember having an issue. Also, there is a potential issue with the tread seam coming apart. We run the tires in the recommended direction at the first event and then ignore the direction for the rest of the tire’s life. Our team has only had an issue with the seam on one tire when it was new and that came with a serious vibration. Seems to be a pretty tough tire to me.

    Endurance: How hard can you push the tire in a session before the grip goes off? The biggest complaint about the 888 was that if you pushed it at all, it would get greasy and grip would vaporize. It was no fun to drive and almost prohibited on track battles. It was horrible for racing. In this respect, I think the RR’s are pretty amazing. You can abuse and over drive these tires and, for the most part, they seem to keep holding their grip. I think abusing these tires hurts their effective life but they hang in there. I think this is a critical parameter to an exciting race tire.

    Looking at that stuff, it seems like a great tire. I actually think it is. If someone was handing out fresh tires every race day, I think this would be a spectacular spec race tire. But, tires aren’t being given out and there are a couple of other critical parameters that make these tires not so good for a class that needs to run a set of tires in multiple events to make the budget work. In a class that is supposed to give each competitor equal grip from a spec tire, this tire has more variability than any other performance parameter.


    Heat cycling: This is a common term for the performance of the tire falling off after a certain number of track sessions. I see numbers all over the map of how many heat cycles people think these tires are good for. I’ve come to the conclusion that the term “heat cycles” probably isn’t the best terminology for these tires. It’s not that heat cycles don’t apply to these tires, it’s just that heat cycles aren’t all created equal. I think it’s more that the tire is capable of a certain amount of time at temperature. The higher the temperature, the less time you have. The number of effective heat cycles you get depends on how much abuse the tire sees. These tires tolerate over driving pretty well but it comes at the expense of reduced effective performance life.

    So why does the performance of the tire drop after use? Tire construction, materials, chemistry, and processing is very complicated and generally considered complete voodoo even by tire engineers. In the past, it’s been said that race tires effectively come as partially cured rubber. Further heating and distortion of the tire finishes up the curing process and the tire becomes harder. There is some thought that Toyo could process the tires differently and deliver them fully cured. In theory, this would lower their initial performance but make them more stable over their life. I’m not sure if that’s true but I sure would like to see it. I believe Toyo’s incentive to do that is low…

    Handling: I think this is one of the most fascinating aspects of this tire. I have heard so many times that popping on a fresh set of RR’s will cure all of the car’s handling issues. People love how these tires handle when they are new and hate how they handle when they are all used up. Changing the overall amount of grip can have a small effect on handling balance but it shouldn’t dramatically change the handling.

    I believe what is changing is the effective shape of the slip angle graph. The slip angle graph for this tire seems to have a pretty flat and wide peak on fresh RR’s. This wide peak allows good grip over a variety of slip angles and masks subtle balance issues and handling deficiencies. As more time/abuse is put into the tire, not only does the peak grip level dip down a bit, but the peak becomes sharper. This sharp fall off of grip past the peak quits masking issues and requires the driver to sense much more subtle inputs to keep the car near the peak grip level. The car is just flat harder to drive. The drop in performance depends not only on the condition of the tire but also the base handling of the car and the ability of the driver to deal with the sharper peak. If anyone has any further insights to expand or contradict this thought, I’d love to dig into it deeper.


    On a practical application of this knowledge, we’ve found driving through a handling imbalance is a bad idea with these tires. One event at Cresson had Dan with a bit of understeer early in the weekend. He thought it was tolerable and didn’t want me to change anything. A couple of sessions later, he had abused the front tires enough that the front tires were signing off and the understeer was now magnified to intolerable levels. We made changes every session that should have made the car an oversteering pig with no success. I didn’t catch a clue to what was happening until we got back to the shop and looked at the differential tire wear front to rear. Now I hammer on balance with Dan early in the weekend and we often end up changing rear springs or sway bars during the event to keep on top of it. When the engine runs, anyway…


    Richard P.

    Sooooooooo that is a yes, you are volunteering Dan to run the 615s? but seriously..... Dan?

  6. #66
    Nvm... that was a waist of my post, just saw the list on the roll call thread

  7. #67
    Senior Member Rookie 39PitCrew's Avatar
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    Quote Originally Posted by RichardP View Post

    Handling: I think this is one of the most fascinating aspects of this tire. I have heard so many times that popping on a fresh set of RR’s will cure all of the car’s handling issues. People love how these tires handle when they are new and hate how they handle when they are all used up. Changing the overall amount of grip can have a small effect on handling balance but it shouldn’t dramatically change the handling.

    I believe what is changing is the effective shape of the slip angle graph. The slip angle graph for this tire seems to have a pretty flat and wide peak on fresh RR’s. This wide peak allows good grip over a variety of slip angles and masks subtle balance issues and handling deficiencies. As more time/abuse is put into the tire, not only does the peak grip level dip down a bit, but the peak becomes sharper. This sharp fall off of grip past the peak quits masking issues and requires the driver to sense much more subtle inputs to keep the car near the peak grip level. The car is just flat harder to drive. The drop in performance depends not only on the condition of the tire but also the base handling of the car and the ability of the driver to deal with the sharper peak. If anyone has any further insights to expand or contradict this thought, I’d love to dig into it deeper.


    On a practical application of this knowledge, we’ve found driving through a handling imbalance is a bad idea with these tires. One event at Cresson had Dan with a bit of understeer early in the weekend. He thought it was tolerable and didn’t want me to change anything. A couple of sessions later, he had abused the front tires enough that the front tires were signing off and the understeer was now magnified to intolerable levels. We made changes every session that should have made the car an oversteering pig with no success. I didn’t catch a clue to what was happening until we got back to the shop and looked at the differential tire wear front to rear. Now I hammer on balance with Dan early in the weekend and we often end up changing rear springs or sway bars during the event to keep on top of it. When the engine runs, anyway…


    Richard P.
    Richard, I'm not any sort of expert on any of this but the mechanic in me thinks what you say makes a lot of sense.
    As I've read a couple of the tire threads here, I'm left to wonder about some things.

    If I understand the issue: consistent performance over many driving cycles; where "many" is some arbitrary number, say 20.
    The secondary issue: amortizing $$$$ spent across the # of driving cycles before the tire tread thickness reaches gone/cords
    or the tire becomes substantially uncompetitive or dangerously unpredictable for door-to-door competition.

    It seems to me that some of the discussion is adding in a performance component, that is, how "sticky" the tire is during it's usable life.
    I think the primary goal of the discussion is two-fold - keep performance fair and keep the consumables budget reasonable.
    So the dilemma is: the softer (stickier?) the tire, the faster it wears ($$$) but you get better (lower) lap times. But, a
    soft tire also has a much smaller sweet spot related to it's maximum performance over a certain number of driving cycles.
    A tire that has a harder compound will wear longer. But the trade off is that maximum acceleration, braking and cornering forces
    are reduced by some amount. (And I get it, we're talking about race cars so it's hard to say higher performance is a bad thing.)

    So, if the choice is made to use a harder compound tire, does it follow that the car's set up and the driver's racecraft must be better
    to achieve the same performance (ie. lower lap times) that comes with a softer compound tire?
    And a possible corollary: the more grip a tire has, the more wear/abuse the car's mechanical parts take.
    So, more heat/wear in the brakes, diff and trans loads are higher, more heat and higher loads on wheel bearings, more chassis torsional forces, etc., etc. - right?
    And based on threads here on the forum and many random discussions at the track over the years - car set up is hard. Well, mechanically
    it's easy, dialing it it for optimal track performance is hard. Even NASCAR and F1 teams who have really smart people and spend millions of dollars
    to figure that stuff out don't get it right every time.

    Thoughts anyone?
    Scott
    Last edited by 39PitCrew; 02-13-2019 at 11:29 AM.
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  8. #68
    Senior Member Carroll Shelby
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    I didn’t even consider the lower wear and tear with a 200tw tire, longer hub and brake life, #winning!
    Tyler Gardner
    CMC #13 2015-2017
    SM #013 2018
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  9. #69
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    Quote Originally Posted by mach1 View Post
    I didn’t even consider the lower wear and tear with a 200tw tire, longer hub and brake life, #winning!
    Truth! We'll see how different the laptimes really are
    Daniel Records
    CMC # 34

  10. #70
    Senior Member Carroll Shelby RichardP's Avatar
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    Tire test setup:

    It’s important that if we do a tire test, we pay special attention to a wide variety of parameters to make sure the full package is suitable. We don’t need a different tire, we need a better tire. We also need to agree on the definition of “better” in this context.

    First, per the rules, if a race car isn’t on Toyo tires, it isn’t “racing” in CMC (or AI). Without Toyo’s, no CMC season points are accrued, no Toyo bucks are earned. Also, if a legal CMC car is fighting for position with a non-legal CMC car, technically that could be considered out of class racing.

    There are a couple of different ways to run this. If you have a non-legal car, you can “fun run” in your normal class. I think a better option is for the tire test folks to run AIX. That keeps things a bit separate and the “winner” of the tire test potentially gets a plastic trophy, some winner stickers, and a season championship! I’m happy to supply AIX stickers to any tire testers for this test. When we had both CMC and CMC2 racing together, I pushed for decals on the windshield and back glass so competitors could easily tell who they were racing for position with and who they weren’t. I think something like that would be good for this.

    As I posted earlier, there are a number of relevant parameters we would be testing for. How does the tire feel, how well does it stand to abuse, if you overheat it does it come back after easing up for a lap or is it dead for the rest of the session, etc.??? These are pretty easy to test for in just a few sessions. In my opinion, we can only really tell what we want to about the tire under full race conditions with cars fighting for position.

    The much bigger question is how much do the tires degrade with heat cycles? If all of the tire testers start and run the whole weekend on fresh tires, we learn exactly zero on this aspect. Ideally, this test needs to span multiple weekends and possibly multiple sets of tires. In order to figure anything out, we need to have a guy on stickers battling a guy who has at least one full weekend of abuse on his tires. We could have some testers start the weekend on fresh tires and have others wait until Sunday to put the stickers on. Josh is running a Houston DE the first weekend in March and could do his best to wear the test tires out before our race weekend. The more testers the better if we hope to get any real findings.

    Getting useful data from a test like this is pretty tough. Initially, we have to figure out what these tires want and get them to work with our cars. What tire pressures do they want? Do they do better or worse with our camber settings? Do they work better with stiffer or softer sprung cars? Slapping on a different style of tire and judging them after a session or two without tuning is very useful. Also, some drivers adapt to changes quicker than others.

    The other question is what specific data are we going to be looking at? Certainly lap times are key. Comparison of test tire lap times to Toyo tire lap times is certainly interesting but not really relevant to our test. We need to be looking to differences between tire test competitors. We need to pay special attention to lap time degradation between test subjects, especially those that are on tires with differing heat cycles.

    One of the hardest parts of these types of tests is the other variables that are hard to control. Weather, traffic, car setups, etc. are all a big deal but not as significant as the difference between drivers. One example of things we can try to mitigate would be to have competitors swap tires between sessions. Have Josh start the race weekend on heat cycled tires while someone else starts on stickers. After a couple of sessions to set a baseline, have the two swap tires and see the relative change. This could help answer if the difference between cars is the driver or tire wear.

    One other thing that would help with testing. The test drivers actually need to race each other. Starting on pole for the invert because you had a problem in the first race and trying to run away with it is something that I might want to do (OK, have done) but it isn’t helpful for our testing. Traffic, cautions, or other situations might lead to some of the test drivers having to wait up for the other testers.

    On a personal preference note, I would prefer to suspend any tire testing for the Hallett event. The racing there is too much fun (sacred even) to split up the group. I’d love to see everyone on a fresh set of Toyo’s for this spectacular, multi-region event.

    Richard P.

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