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NickD
NickD UltimaDork
7/6/20 3:36 p.m.

A few weeks ago, a gentleman named Mario, who I frequently race with at Pineview Run and handles the rules and classing for Pineview's Challenge Cup time trial series, asked me if I would want to come up and turn a few laps for a day for free to help him with tire testing and data acquisition. Mario loves testing and data acquisition, and was looking to make some changes to Challenge Cup classing to level the playing field a little. The catch: I wouldn't be driving Barbatos, my 250whp supercharged Miata. Oh no, I'd be driving Chuck.

Enter Chuck. Its a 2010 Toyota Yaris 3-door hatch with a 5-speed manual that I picked up this spring. It has 135k miles on it and is pretty original underneath. That means stock springs, struts that don't look like they've ever been replaced, original bushings, unknown brake pads and shoes and an alignment that I haven't checked. The only mods are a TRD rear sway bar and a set of 15x7 Advanti Storms with 205/50R15 Continental ExtremeContactSport. I bought the car to be a fun DD and occasionally autocross if the weather was bad, but never have, so I'd never driven the car in anger.

So, I loaded up my jack, tire spray and electric impact gun and made the hour drive to Pineview and got there at 10:30. They were having a Challenge Cup event that morning, but it was supposed to be done at 11:15, so I figured I'd show up, catch the last couple minutes, and BS with some people. Well, there was a bit of a pall hanging over the track that morning. An Audi TT had had an off and was pretty badly damaged, then an LS-swapped Hyundai Genesis destroyed the rear differential and had to be towed off, and the track transponders were weirdly going to sleep randomly, so there was a bit of a delay before we got down to business.

The plan was to leave the Continental on, I would go turn a few laps, then Mario would turn some laps. Then we would swap over to some TR Motorsports 15x7s shod in Toyo RRs. We had hoped to also test Bridgestone RE71Rs, but couldn't find anyone to lend us a set in Yaris sizing. The goal was to see if B-Spec cars like Fits and Yaris and Mazda2s could be competitive in C4 (the lowest Challenge Cup class, it is calculated by weight divided by HP divided by a point value assigned to different tire types) or if they needed an allotment for better tires to get them in the fight. We had both a track transponder on it and an AIM Solo to make sure we got lap times.

So, first out was on the 340tw Continentals. My Miata typically turns 1:17s on this track, although it has the potential to be into the 1:15s or 1:16s, if not faster, so my guess for the Yaris was 1:25s. I went out and was thoroughly enjoying myself on track, as its a bit like driving a stock Miata. It's a bit roly-poly and slow but happy, like a puppy. Despite bing unknown pads and shoes on tiny rotors and drums, the brakes never really seemed to fade either. The tires had plenty of grip, although there was a lot of squealing going on underneath. The only major downsides were the lack of an LSD (come out of a few corners and I could feel the inner tire wheelhopping like made) and a serious buzzkill traction control. I'd come barreling into the first turn, a big downhill 180, and go to get on the throttle hard halfway through the corner and the TCS light would flash accusingly, it'd start beeping at me and then cut the throttle for a solid second or more.

My first lap out was a 1:25, about what I expected, but as I glanced at the AIMSolo out of the corner of my eye, I glanced a 1:23, then another 1:23, then a 1:22 and another 1:23. I didn't want to flog my DD to death, so I came in and began spraying down the tires and radiator and told Mario about the 1:22, which we confirmed with track timing. Both of us were pretty elated, as it was much better than what we expected and only about a second off the frontrunners in C4. He jumped in and went out and turned some laps but could only get a 1:25 out of it.

With visions of 1:20s in our head, we jacked the car up and swapped on a set of well-loved 40tw Toyo RRs on TRM wheels.

I went out first with them and they felt pretty grippy, although I was still getting some wheelspin if I tried too hard out of the corner. First lap was a 1:26, followed by a 1:25, then another 1:25, then another 1:25, then another 1:25. What? How? I would make up a few tenths of a second here and there, but no indication that it was even going to match that 1:22, let alone beat it. Defeated I pulled in, and started spraying the tires. Mario was a little baffled at it going slower, so he went out and got a 1:24 for his effort. 

So at the end of the day, we were really left scratching our heads. I went fast on the Contis, then slowed down on the Toyos. He went slower on the Contis and faster on the Toyos, but still not as fast as my best on the Contis. 

A round of bench-racing ensued with everyone present and we really just couldn't come up with a solid answer. Did the extra grip cause too much rolling resistance for the engine? Were the Toyos heat-cycled to death? There was doubts about that, because they had done a similar test on a Miata a week or two earlier with that very set of Toyos and they outran the Contis then. Was the traction control just not letting us take full advantage of the Toyo's grip? It was baffling. We hope to get a few more types of tires together and try it again in the near future.

WonkoTheSane (Forum Supporter)
WonkoTheSane (Forum Supporter) SuperDork
7/6/20 3:45 p.m.

Does that have stability control or just traction control?

If it has stability control, my vote is that the the stickier tires (presumably the Toyos?) were generating to much suspension travel and causing the stabiltity control to tone it down until the car came under control which takes half a second longer than traction control needs to tone down wheel slip.  The Contis couldn't put that much load into the suspension so you were only fighting the traction control on your application of throttle with the open diff.

WonkoTheSane (Forum Supporter)
WonkoTheSane (Forum Supporter) SuperDork
7/6/20 3:46 p.m.

Oh, and that sounds like a boatload of fun regardless.. I really enjoyed flogging rental yarises when I was travelling for work.  They're fun!

djsilver (Forum Supporter)
djsilver (Forum Supporter) Reader
7/6/20 3:52 p.m.

The old adage "loose is fast" applies.  The Yaris is a low horsepower car and the stickier tires slowed it down by not letting it slide around and still go fast.  Trying to turn it on the Toyo's just acted like putting on the brakes.

NickD
NickD UltimaDork
7/6/20 3:55 p.m.

In reply to WonkoTheSane (Forum Supporter) :

2010 they got both ABS and Stability Control. I'm guessing when I was getting it beeping at me was when Stability Control was kicking in (which is usually when it'd cut power) and when the light was just flashing was traction control. And yes, it was absolutely hilarious, while being shockingly competent. It never fried the brakes or puked coolant or threw a Check Engine Light. 

dps214
dps214 HalfDork
7/6/20 4:10 p.m.

I'd guess stability control is the culprit. Giving the car more grip than the stability system thinks it's able to generate is an easy way to make it freak out.

KyAllroad (Jeremy) (Forum Supporter)
KyAllroad (Jeremy) (Forum Supporter) UltimaDork
7/6/20 5:31 p.m.

So there is no magic button/cheat code/fuse-to-pull that turns off the electronic nannies?

WonkoTheSane (Forum Supporter)
WonkoTheSane (Forum Supporter) SuperDork
7/6/20 5:35 p.m.
KyAllroad (Jeremy) (Forum Supporter) said:

So there is no magic button/cheat code/fuse-to-pull that turns off the electronic nannies?

There should be... But be careful, if those things use an adjustable brake bias via the abs pump, disabling it may result in bad braking.. I ran into that on my 99 Porsche :). Do a threshold brake test in a safe place if you go down that route!

Tom1200
Tom1200 Dork
7/6/20 6:05 p.m.

What size were the Toyos, the same or slightly bigger? Were the wheel and tire combo for the Toyos heavier?

The Toyos were likely spent but if you have a lot of tight turns the gains for wider tires will be offset by having to drag around more tire.

spandak
spandak HalfDork
7/6/20 7:05 p.m.

Probably not it but I have the same Contis and they are pretty light I think. This is more of an impression but the 17s with the Contis were SIGNIFICANTLY lighter than 18s with Falkens. 
Like half if my arms can be trusted. 

ShinnyGroove (Forum Supporter)
ShinnyGroove (Forum Supporter) Reader
7/6/20 8:05 p.m.

The Conti ECS are a surprisingly good tire on the track.  On my Miata they were only a second or two off of RE-71's. Anyway, my guess is that you were undersprung for the RR's, sitting on the bump stops in the turns and unsettling the car. 

adam525i (Forum Supporter)
adam525i (Forum Supporter) HalfDork
7/6/20 8:14 p.m.

You had an Aim Solo on board, what did the data say? Where were you losing the time? The corners, on the brakes, on the straights or everywhere?

Robbie (Forum Supporter)
Robbie (Forum Supporter) MegaDork
7/6/20 8:41 p.m.

Did you go back to the contis afterward? Was the track cooling or heating?

Vigo (Forum Supporter)
Vigo (Forum Supporter) MegaDork
7/6/20 9:32 p.m.

Yes, the beeping sounds very reminiscent of the sound my Prius used to make when i got into stability control. angel

Now I have an Echo with no nannies whatsoever. It is half the car, but probably better for things like this. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
7/6/20 11:01 p.m.

Could the grippier tires be overpowering the chassis, causing the suspension to bottom out and understeer more?

NickD
NickD UltimaDork
7/7/20 5:18 a.m.
WonkoTheSane (Forum Supporter) said:
KyAllroad (Jeremy) (Forum Supporter) said:

So there is no magic button/cheat code/fuse-to-pull that turns off the electronic nannies?

There should be... But be careful, if those things use an adjustable brake bias via the abs pump, disabling it may result in bad braking.. I ran into that on my 99 Porsche :). Do a threshold brake test in a safe place if you go down that route!

There is no button. We considered pulling the fuse, but it was really hot out and we didn't feel like messing with it.

sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
7/7/20 5:32 a.m.

if you've got AIM solo data, I (or you) can suck it into TrackAttack to compare the traces

NickD
NickD UltimaDork
7/7/20 6:54 a.m.
sleepyhead the buffalo said:

if you've got AIM solo data, I (or you) can suck it into TrackAttack to compare the traces

It was Mario's AIM Solo. I'm sure he'll probably do an in-depth analysis and write an entry on his blog on it and then all will be revealed. I just thought it was a really funny/weird day of testing that I wanted to recount

NickD
NickD UltimaDork
7/7/20 7:08 a.m.
Tom1200 said:

What size were the Toyos, the same or slightly bigger? Were the wheel and tire combo for the Toyos heavier?

The Toyos were likely spent but if you have a lot of tight turns the gains for wider tires will be offset by having to drag around more tire.

The Toyos were the same size, 305/50R15. Tire Racks says 20lbs per tire for the Toyo and 19lbs per tire for the Contis, plus the TR Motorsports C1M wheels are 13.6lbs to the 10.8lbs of my Advantis. So that's 16lbs of unsprung weight. That was definitely not helping the cause. Although they had run that same set of Toyos on those wheels against a Miata on Conti ECS (no clue what wheel they were using though) and it had gone noticeably faster on the Toyos.

WonkoTheSane (Forum Supporter)
WonkoTheSane (Forum Supporter) SuperDork
7/7/20 7:48 a.m.
NickD said:
WonkoTheSane (Forum Supporter) said:
KyAllroad (Jeremy) (Forum Supporter) said:

So there is no magic button/cheat code/fuse-to-pull that turns off the electronic nannies?

There should be... But be careful, if those things use an adjustable brake bias via the abs pump, disabling it may result in bad braking.. I ran into that on my 99 Porsche :). Do a threshold brake test in a safe place if you go down that route!

There is no button. We considered pulling the fuse, but it was really hot out and we didn't feel like messing with it.

Right on.   Just to be clear, when I was referencing my Porsche, I also meant pulling the fuse.  If there's a button to disable it, it won't screw up your brake bias.  The Porsche had a button to turn it "off," but it really just meant "suck slightly less."

Tom1200
Tom1200 Dork
7/7/20 10:36 a.m.

About a decade ago a buddy helped me with Friday testing on the Datsun; we bolted on some Hoosier vintage race tires. Fresh tires are worth about 2 seconds a lap but we picked up 6 seconds. Totally blown away I sat down and started writing down all the differences with the tire; 12lbs of unsprung weight, lower gearing / shorter tire meant not only did the car ride an inch lower the motor was pulling more revs (being in the meat of the powerband = 10hp) and 4 fewer shifts per lap. 

If you told someone that lowering a car 1 inch (shorter tire), adding 10hp, making 4 fewer shifts and losing 12lbs of unsprung weight would equal 4 seconds on a 3.4 mile course they probably say you were full of it.

I've got some comparative lap times built up from various changes; I know that 10hp is good for 1-1.2 seconds and the 4 fewer shifts are worth about .4-.5 seconds. If I go with the every pound of unsprung weight = 10lbs, then the 12lbs = 120lbs and losing 120lbs on the car is worth approximately .75-1 second per lap.  All that adds up to 2.5-2.7 per lap leaving me to the highly speculative conclusion that lowering the car 1" is worth the remaining 1.3-1.5 seconds per lap. 

Nick I could envision 16lbs of unsprung weight being worth a second on a Yaris. That leaves another 2 seconds unexplained. My guess is still the Toyos were not at their best. As for you being faster on the Contis, I right that down to familiarity with the set up. It will be interesting to see what the data says.

APEowner
APEowner Dork
7/7/20 11:23 a.m.

I suspect that the reason you slowed down on the RRs while Mario sped up is that the RRs don't like a lot of slip angle and Mario, in a borrowed car that the owner needed to drive home wasn't sliding as much as you were. 

NickD
NickD UltimaDork
7/7/20 11:32 a.m.
Tom1200 said:

 As for you being faster on the Contis, I right that down to familiarity with the set up. It will be interesting to see what the data says.

I wouldn't really say I was familiar with that setup. I've never raced, autocrossed or really hooned the car at all. I will say probably some of it came down to him not wanting to crash out sonmeone's car. I also wonder if some of it had something to do with the fact that during my Continental-shod laps, I had a Spec Miata crawling up my ass who was supposed to be going slow scrubbing in tires but was in actuality hauling ass (he would actually end up getting black-flagged after he passed me and another car with a newbie in it, as it was supposed to be a non-passing session)

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
7/7/20 11:37 a.m.
APEowner said:

I suspect that the reason you slowed down on the RRs while Mario sped up is that the RRs don't like a lot of slip angle and Mario, in a borrowed car that the owner needed to drive home wasn't sliding as much as you were. 

Hmmmm.....

iceracer
iceracer MegaDork
7/7/20 11:43 a.m.

With more grip it was just picking up it's inside rear wheel.

Before stability control this was not a problem.

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