Extreme ACR tire and CCM brake life update

[VENOM V]

Now that I've gone through some tires and brake pads, I thought I'd share the life I'm getting out of them.

Kumho V720 ACR tires:
Front: 1-1/2 to 2 track days, depending on the track
Rear: 6 track days

CCM brake pads:
Front: 4 track days
Rear: 8 track days

As for brake fluid, I did a complete dot 4 flush before my first track day, then bled them after six track days which was about 4-1/2 months. Never felt any fade.

Tracks: Laguna Seca, Chuckwalla, Sears Point, Thunderhill

This is going to vary greatly with driving style and experience level, track abrasiveness and track layout, so hopefully others will post their experiences too.

[Junkie]

How much are replacement pads? I've already got a new set of tires waiting on me.

[Arizona Vipers]

Kumho V720 ACR tires:
Front: 1-1/2 to 2 track days, depending on the track
Rear: 6 track days

Have you tried Hoosier's on the stock rims for the hell of it and compared lap times on the same track? The fronts would last longer for sure....



CCM brake pads:
Front: 4 track days
Rear: 8 track days


How much are the pads?



As for brake fluid, I did a complete dot 4 flush before my first track day, then bled them after six track days which was about 4-1/2 months. Never felt any fade.

That's insane! Do you attribute the long periods between brake fluid bleeding to the CCB brakes?

[Bruce H.]

Hey Todd,

I'm wondering if you could extend your front tire life a little by adjusting your corner strategy slightly to reduce the combined load and resulting wear from heavy braking while cornering. I find the Corsa's let you push them well beyond overheating without feeling as greasy as other R-compounds I've run. A little weight transfer with a throttle lift is often enough to get the front to turn-in, and it will also take a lot of trail braking to increase front grip to push the tire even further. The tire just seems to let you over-drive and abuse it something awful before packing it in, but by then you've ruined it and just waiting for the rubber to blister off and end the party. The tire is very confidence inspiring, outstanding for lap times at the expense of tire life, and encourages me to slide the car more than I otherwise would, and I have to remind myself to back it down a bit. I suspect the Kumho may have been designed similarly.

I wonder if getting more of the braking done before turn-in, and less in the corners using brakes or scrubbing, could be done without adversely affecting your lap times too much. Basically a slow in, fast out, later apex strategy to help save the tires. Thoughts?

And did I see you're driving to NVE2 instead of shipping? ACR or Halle?

Bruce

[swexlin]

When you say you bled the brake fluid, you are just bleeding any air out, or are you changing it at that time as well?

[ACR Steve]

bleeding = removing air but does add some fresh fluid
Flushing = full brake fluid change

great write up on the brake consumables. My 1 day at the track saw exactly what you are seeing.

Bruce- I don't trail brake my car after long straights or in most very hard braking corners and have seen the same results. I do however brake very late and transition back to power as soon as possible. With an aero car you have to be carful not to upset the aero functionality by radically changing the attitude of the car especially for the faster turns. I don't think it really makes a difference with front tire wear . Load is load . If you run our cars at 95%+ of what they are capable of then you will eat consumables. The realm that these cars run is as fast as some of our fastest racing sedans in any series. Street tires and pads become a constant consumable.

Faster you go the more you spend, its the price you pay to be the fastest car on track :)

[mjorgensen]

The factory front and rear pads are $850 front and $630 rear retail pricing.

There is 2.7" of difference front to rear diameter on the stock ACR tire setup and the stability, tractions control and ABS programming is all based on this specially for the ACR and CCB. According to the engineers this cannot vary by more than about 10% and still function without possibly upsetting the ABS at least. If you go to the Hoosiers the best you can get with the 345/19 and the 295/19 is a 1.5" difference. I think Dan Cragin said they ran them and it worked though, I don't remember if that car had steel brakes or not though, that could be the difference.







Have you tried Hoosier's on the stock rims for the hell of it and compared lap times on the same track? The fronts would last longer for sure....



How much are the pads?


That's insane! Do you attribute the long periods between brake fluid bleeding to the CCB brakes?

[VENOM V]

Have you tried Hoosier's on the stock rims for the hell of it and compared lap times on the same track? The fronts would last longer for sure....



How much are the pads?


That's insane! Do you attribute the long periods between brake fluid bleeding to the CCB brakes?

I haven't had a chance to run Hoosiers on the ACR, although they were the only tire I ran on the GTS. To be honest, I'm so happy with these Kumhos that I'm not planning on switching. The rears lasting six track days makes up for the fronts lasting only 1-1/2 to 2 days. Plus, these tires stay soft and grippy all the way to cord! They don't heat cycle out like Hoosiers or anything else I've driven on.

I attribute the long period between brake fluid bleeding in part due to me having the wrong cap for my reservoir and not having anyone to help me. I would have bled them more frequently, but I couldn't at the time. I'll try to keep my bleeds to every 3 months from here on out, as I've picked up the correct reservoir cap.

The 6-piston calipers don't seem to be seeing the same level of heat as previous track cars with iron brakes, I have no discoloration of the red paint so far. CCMs insulate rather than conduct heat into the calipers, so they must be running cooler where the brake fluid resides. And when I did bleed, the fluid looked in good condition and I didn't see any bubbles.

[VENOM V]

Hey Todd,

I'm wondering if you could extend your front tire life a little by adjusting your corner strategy slightly to reduce the combined load and resulting wear from heavy braking while cornering. I find the Corsa's let you push them well beyond overheating without feeling as greasy as other R-compounds I've run. A little weight transfer with a throttle lift is often enough to get the front to turn-in, and it will also take a lot of trail braking to increase front grip to push the tire even further. The tire just seems to let you over-drive and abuse it something awful before packing it in, but by then you've ruined it and just waiting for the rubber to blister off and end the party. The tire is very confidence inspiring, outstanding for lap times at the expense of tire life, and encourages me to slide the car more than I otherwise would, and I have to remind myself to back it down a bit. I suspect the Kumho may have been designed similarly.

I wonder if getting more of the braking done before turn-in, and less in the corners using brakes or scrubbing, could be done without adversely affecting your lap times too much. Basically a slow in, fast out, later apex strategy to help save the tires. Thoughts?

And did I see you're driving to NVE2 instead of shipping? ACR or Halle?

Bruce

Hi Bruce,

Yes I'm familiar with those techniques and I try to trail brake which I think helps. I'm not wearing out the fronts as fast as some other ACR owners that I've tracked with, so I think it's helping. The other thing is to do a warm up lap before going hard, otherwise they may chunk.

I'm bringing the ACR for NOLA baby! We are having the ACR shipped to Texas to party with D'Ann and Wayne, then will join a 100-Viper caravan to New Orleans. It will be shipped from New Orleans back to San Jose after NVE2.

May and I look forward to seeing Deb and you there. :smileys-car-driving

Todd

[VENOM V]

great write up on the brake consumables. My 1 day at the track saw exactly what you are seeing.

Faster you go the more you spend, its the price you pay to be the fastest car on track :)

This is such a true statement. This is real race car territory- high Gs in the corners and under braking = you wear stuff out! Luke is finding that his front Pirelli slicks are wearing out at about the same rate as I am on the Kumhos, which shows the tremendous amount of loading that these tires endure. This car has to dissipate a lot more energy than most anything at the track, and that energy goes into the tires and brakes.

If you wanna play, you gotta pay! Haha

[Bruce H.]

Bruce- I don't trail brake my car after long straights or in most very hard braking corners and have seen the same results. I do however brake very late and transition back to power as soon as possible. With an aero car you have to be carful not to upset the aero functionality by radically changing the attitude of the car especially for the faster turns. I don't think it really makes a difference with front tire wear . Load is load . If you run our cars at 95%+ of what they are capable of then you will eat consumables. The realm that these cars run is as fast as some of our fastest racing sedans in any series. Street tires and pads become a constant consumable.



I seldom trail brake either so maybe I'm ready to step up to an ACR too:) But I disagree with load being load as it applies to tire wear when combining brake and steering forces, and more specifically edge wear and overheating causing the blistering that we see. Braking in a straight line at the limits of grip would distribute heat and wear more or less evenly across the face of the tire. Hard cornering on the limits of grip would apply sheering forces, heat and wear concentrated on the outer portion of the tire face. Applied separately, as you do when either braking or cornering, the available grip is lower and the forces are applied across a pair of tires, as opposed to a much higher available grip and applied forces being more concentrated on a single front tire in the case of trail braking while cornering hard.

Now combine that with the front tire's softer compound, additional sidewall flexing from steering input and smaller overall diameter and I think the driver has to become especially good at managing front tire edge temps. So this is why I think a very advanced and aggressive driver using trail braking and pushing very high slip angles is going to overheat the front tire's outer areas to the point that the tire will blister rather quickly. Tires are definitely quickly consumed the faster you go, but just like in racing you attempt to manage their consumption.

[Bruce H.]

Hi Bruce,

Yes I'm familiar with those techniques and I try to trail brake which I think helps.

I'm bringing the ACR for NOLA baby! We are having the ACR shipped to Texas to party with D'Ann and Wayne, then will join a 100-Viper caravan to New Orleans. It will be shipped from New Orleans back to San Jose after NVE2.

May and I look forward to seeing Deb and you there. :smileys-car-driving

Todd

You can tell from the above that I was thinking your trail braking would make it worse.

That's great about bringing the ACR and doing D'Ann and Wayne's. We'd have like to as well but just too far considering our route down to New Orleans. Looking forward to seeing you both!

Bruce

[ACR Steve]

I am not getting excessive outer tire wear mine is outer middle of tire. I think with all the negative camber ACR's have compared to the TA's it makes a big difference. From the factory on base setting we are double a TA's negative camber.

For the all time fastest production street car on street tires and not gutted down to lighten I don't think the tire wear is excessive. Although we always wants more life out of them

[VENOM V]

You can tell from the above that I was thinking your trail braking would make it worse.

That's great about bringing the ACR and doing D'Ann and Wayne's. We'd have like to as well but just too far considering our route down to New Orleans. Looking forward to seeing you both!

Bruce

I think at this level it gets down to semantics. It's hard to put into words what we are doing as we intuitively give the car the inputs it needs to balance performance and longevity. I was taught to trail brake so lightly that you don't actually feel much deceleration, you are just giving the front tires the weight transfer they need to get them to set. I am not heavy braking in the corner when I do this, just a very light pedal. It's much like lifting during the corner but just a little more weight transfer to the front. Both Erich Heuschele and Chris Winkler were encouraging me to trail brake.

Here's what I focus on to keep these Kumhos happy and put down fast laps, somewhat in order of priority.
1. Focus on nailing tire pressures. I start typically at 24 psi cold, 33 psi hot. More than that isn't good for the tires
2. Consciously ensure that I'm not over-turning the front tires, causing them to push and scrub through the corners
3. On corner exit, try not to over-drive the fronts and scrub them. However with the right line, you can be WOT before most apexes like no other car I've driven
4. Set up the car so it doesn't push. Wing at position 1 (lowest downforce) balances the car, all hood and wheel well vents out, sufficient rake in the car per the ACR manual (4" front frame, 5.5" rear)
5. Don't over-stiffen front damping or it will kill the tires. I run rebound / compression as follows:
front: 5 / 7
rear: 3/ 7

All that said, I think Steve nailed it with this statement:



For the all time fastest production street car on street tires and not gutted down to lighten I don't think the tire wear is excessive. Although we always wants more life out of them

[TA Two Oh]

[QUOTE=ACR Steve;217910]I am not getting excessive outer tire wear mine is outer middle of tire. I think with all the negative camber ACR's have compared to the TA's it makes a big difference. From the factory on base setting we are double a TA's negative camber.

i believe the TA's negative front camber spec is 2.5 and the ACR's is 2.8. In the rear the TA spec is -1.5 to the ACR's -1.7. More negative camber for sure, but not anywhere near double.

[Bruce H.]

Good details of your cornering, Todd, and it certainly sounds like you're doing absolutely everything to manage tire life as you run fast laps. The only thing you're not doing is consciously choosing to lap a little slower. I know from personal experience though that approach only works for a couple of warm up laps....less if I see a P or F car in front of me, lol.

In my case with the Corsa's, avoiding scrubbing off speed after turn-in and overdriving with throttle to turn-out in some of the more challenging corners are the big ones. The car is so balanced, and the tire's limits so high and broad, that it's just very easy to run really abusive slip angles as you slide it through the corners. I can run tidy and consistent 1:34-35's around Mosport with the faster P, F and M guys and still be relatively kind to the tires, but dipping into the 1:31-32's you can feel the cost to front tire life through the steering wheel even though they don't seem to protest. Kumho R's screamed like raped chickens when pushed on my Supra, but hardly a whimper from the Corsa's. I do try to warm them up and cool them down slowly, often from track right out onto the local roads.

If I were to change to track specific tires like a Hoosier those times would drop 2-3 seconds but the tires wouldn't last that much longer, and I'd have to add the cost and inconvenience of a tow vehicle and trailer. Instead, my Mosport 2016 season plan is to just settle for running 1:34's...wish me luck with that one!

Bruce

[ACR Steve]

ACR is -3.to -3.1

[VENOM V]

Good details of your cornering, Todd, and it certainly sounds like you're doing absolutely everything to manage tire life as you run fast laps. The only thing you're not doing is consciously choosing to lap a little slower. I know from personal experience though that approach only works for a couple of warm up laps....less if I see a P or F car in front of me, lol.

In my case with the Corsa's, avoiding scrubbing off speed after turn-in and overdriving with throttle to turn-out in some of the more challenging corners are the big ones. The car is so balanced, and the tire's limits so high and broad, that it's just very easy to run really abusive slip angles as you slide it through the corners. I can run tidy and consistent 1:34-35's around Mosport with the faster P, F and M guys and still be relatively kind to the tires, but dipping into the 1:31-32's you can feel the cost to front tire life through the steering wheel even though they don't seem to protest. Kumho R's screamed like raped chickens when pushed on my Supra, but hardly a whimper from the Corsa's. I do try to warm them up and cool them down slowly, often from track right out onto the local roads.

If I were to change to track specific tires like a Hoosier those times would drop 2-3 seconds but the tires wouldn't last that much longer, and I'd have to add the cost and inconvenience of a tow vehicle and trailer. Instead, my Mosport 2016 season plan is to just settle for running 1:34's...wish me luck with that one!

Bruce

Haha, I have to admit that I am rarely consciously choosing to lap slower either. I usually run a few laps really hard when the track is clear, then I back off when I'm in traffic.

And your experience with Corsas is exactly the way the ACR's Kumhos are- you can abuse the crap out of them and you won't hear much protest. They take it like the men they are! They fight until their last breath. I will say this- the rear tires stayed grippy to the death and lasted a long time. I ran my best lap times at Thunderhill just before both front and rear tires went nearly to cord. Hoosiers on the other hand get heat cycled out and slow way down after a couple of track days. The Kumho rears lasted 6 days and are still sticky as chewing gum all the way to the outer edge.

[TA Two Oh]

ACR is -3.to -3.1

17178

ACR Steve... where did you find that spec? This is what I've seen... -2.7 to -2.8. And even if it is -3 or -3.1 that's a still long way from double -2.5. Anyway, I'm at -2.5 (front) now and lost the outside edges on my Corsas. I'm going to bump it up a bit to see if it helps. If the correct ACR Spec is -3 I'll try that, assuming my TA will get there.

[Coloviper]

Great thread! Since I don't have a new ACR, all I can add is that last time I checked, real race cars go through a lot of wearable parts to win races. Tires, brakes, rubber parts, fluids, etc. Racing, real endurance racing puts such stress on cars and their parts that the best you can hope for is that the car is designed, built and equipped right so that all you have to replace is a ton of wearable parts, fluids and realign.

The fact you guys are beating the real hell out of these cars on the track and all you are replacing is brake pads and tires is amazing when you think about it. So many other cars you are constantly upgrading this and that because it could not handle it and things broke. Replacing tires and brake pads is nothing really but an expense on the wallet. At least from a risk and safety point, you must feel as safe and secure as a baby in the womb.

[TrackratViper]

My ACR is used 95% of the time on the track. One thing I have noticed about brake pad wear involves the rears. Prior to the last track weekend, the passenger side rears had plenty of pad left. The driver's side outer pad was ok as well. The inner pad on the driver's side was totally gone down to the backing plate! I always run the car in track mode. I think the active handling in that mode is causing the driver's side inner pad to wear much more. Also I noticed some taper in all of the pads. This is similar to what the Corvette guys with CCB are seeing. So the lesson here is make sure you check in the inner pad before every weekend and not just glance out the outers like I did.

[VENOM V]

My ACR is used 95% of the time on the track. One thing I have noticed about brake pad wear involves the rears. Prior to the last track weekend, the passenger side rears had plenty of pad left. The driver's side outer pad was ok as well. The inner pad on the driver's side was totally gone down to the backing plate! I always run the car in track mode. I think the active handling in that mode is causing the driver's side inner pad to wear much more. Also I noticed some taper in all of the pads. This is similar to what the Corvette guys with CCB are seeing. So the lesson here is make sure you check in the inner pad before every weekend and not just glance out the outers like I did.

Yes this mirrors my experience. Inside pads wear more rapidly than outside, in my case by about 1mm. I too will begin inspecting inner pads every tire rotation half way through each day.

I started out running in track mode but now run full off like every other track car I've driven. Rear pad wear seems to be a lot less now. For an advanced driver that is comfortable without stability control, the ACR is the easiest most predictable car at the limit that I've ever tracked. I feel confident in not needing the nannies.

[VENOM V]

17178

ACR Steve... where did you find that spec? This is what I've seen... -2.7 to -2.8. And even if it is -3 or -3.1 that's a still long way from double -2.5. Anyway, I'm at -2.5 (front) now and lost the outside edges on my Corsas. I'm going to bump it up a bit to see if it helps. If the correct ACR Spec is -3 I'll try that, assuming my TA will get there.

I suspect Steve was thinking about the GTS and SRT front camber, which is about half of the ACR's. The SRT engineers that I've talked to encouraged me to go with -3 degrees front camber, and it is working well for me. I may back down to -2.8 degrees next alignment to see if I can get a little more life out the front tires. For your TA, increasing front camber to -2.7 or -2.8 degrees would be beneficial for track performance, I believe. I ran my GTS at that and it handled fantastic.

[VENOM V]

Great thread! Since I don't have a new ACR, all I can add is that last time I checked, real race cars go through a lot of wearable parts to win races. Tires, brakes, rubber parts, fluids, etc. Racing, real endurance racing puts such stress on cars and their parts that the best you can hope for is that the car is designed, built and equipped right so that all you have to replace is a ton of wearable parts, fluids and realign.

The fact you guys are beating the real hell out of these cars on the track and all you are replacing is brake pads and tires is amazing when you think about it. So many other cars you are constantly upgrading this and that because it could not handle it and things broke. Replacing tires and brake pads is nothing really but an expense on the wallet. At least from a risk and safety point, you must feel as safe and secure as a baby in the womb.

Amen brother, the ACR for me has shown to be robust on the track, no issues with anything really except a misfire limp mode which was resolved with a software update. The 2013 GTS was as well, I tracked it for three years and the only thing that needed replacement was an 02 sensor, covered under warranty :dude3:

[Viperawi]

Great read and inputs guys.

It is now a clear message that every ACR owner is sharing that the car is amazingly fast on track ! but it is as important to know the running cost behind it, so thanks again.
I'm starting to love these Kumhos specially when compared to Hoosier by end users like you guys, and wish that someday soon it will be available for other Gen v vipers.

I can add my experience with the Corsa's that they were grippy and overall performed excellent but rather will let go faster than I hoped, at least the fronts will. My front Corsa's will last 2-3 track days max before the rubber will start to chip off. The rears however showed that they can survive for at least 6 track days with no characteristic changes. This is according to my driving style so others may vary, GTS model with factory alignment.

With your cornering and tail braking experience hopefully I can learn something here and do better with the tires.

Thanks again !

[Bruce H.]

The fact you guys are beating the real hell out of these cars on the track and all you are replacing is brake pads and tires is amazing when you think about it.
Not sure how you really meant this, and to clarify for those who don't track, I track my TA and am definitely not beating the hell or even being hard on it. It's just accelerating, shifting within stock redline, braking and cornering. The Viper is specifically built with this use in mind, given proper maintenance. I haven't even seen high temps in hot weather. Car is bullet-proof.


So many other cars you are constantly upgrading this and that because it could not handle it and things broke.
Good examples of beating the hell out of a car. And that unfortunately includes many cars billed as track capable, and that can run an amazing hero lap for marketing purposes, and then dies!

[ACR Steve]

I don't remember were I read stock -3 to -3.1 for the ACR but when I had my track alignment done. My car from the factory had -.3 upfront.

I left that camber alone and played with other stuff.