ETS Setup Journey and tire working hypothesis

his past weekend saw us kick off the new ETS season.

I was one of the few people who didn't go there for testing beforehand and with the weather cutting short our practice runs I really had to nail all my tests and changes to be competitive. But who doesn't love a challenge right?

I started the race off with the base setup I posted except I was using a 2.4-2.7 spring in the front in run 1 on a partially damp and challenging track.

The white lines were lava as it turned out but the balance by itself was already rather good.

I then went to a 2.5-2.8 front spring to retain a little more steering, or much rather the ability to re-adjust the racing line even mid corner. I generally don't like a "blunt" front-end but prefer to be able to real-time tailor the racing line.

The second run on a much-improved track felt good. Great steering (fidelity) and therefore quite easy to get apexes right. The snap oversteer / entirely unprovoked spin outs from round 1 were still persistent but reduced. At this point however I figured that this was the thing I needed to fix to get a car that can do full attack qualifiers, because even when driving very cautiously, the car would do a turn 3 times fine and then on the 4th occasion just misbehave.

Tire working hypothesis: I have been going on and on about tire temp balance between front and rear in my past reports. At this ETS it became abundantly clear that the tires are somewhere in-between the old tires and the new go-kart rubber style modified tires. Important to know here is that while the first have a wider window of ‘workable performance' their peak grip when at optimal temperature is lower. The latter wears in layers, when at optimal temperature and has immense grip, but when cold it's an absolute bitch. This is due to the nature of the compound. One scrubs off (less temp sensitive), one sheds off (when active = warm). In modified you can heat up the tire with throttle and brake no problem. In stock however the only tool you can utilise is scrub angle. Easily done at the front (steering lock), very very hard to do in the rear > the front tires will reach their active temp at about the apex which leads to a sudden jump in traction, while the rears are still cold and inactive > this leads to said sudden snap oversteer. The white lines heat up the tire faster when hit, therefore amplifying that behaviour.

Quick-fix: focus on tire temperature balance throughout the run so that you can keep the rears warm enough and the fronts cool enough to maintain a driveable handling.

Long term fix: Sort out the tires.

With this in mind, I shall continue.

It became clear that especially the first few laps are super-fast but so so tricky and while the harder front spring gave me the front end I wanted, the rear was still lacking to maintain traction.

I tested many things to shift the balance towards more predictability while not taking sharpness out of the steering response.

1.1mm front swaybar: Easier to drive but lost front-end fidelity without really giving enough back to the rear.

PSS only in the rear: Reduced rear roll, gave a little more stability, but didn't improve predictability.

2.0deg rear camber: Up from 1.5. Good improvement, as the tire wear pattern showed a lack of utilisation of the inner tire surface.

2.9 rear spring: good step, because it puts more load and therefore temperature into the rear tire.

3.5mm rear toe-gain: Good step, because it gave a little more apex traction. Still slightly tricky to drive though.

Move the rear shocks out from 2mm to 3mm: Same as in testing. Sacrifice a little bit of steering for gaining trust.

2 screws in rear topdeck: Probably the single biggest thing to counter the snap oversteer. Lost a tiny bit of mid corner rotation, but that was never lacking in the first place.

375/400 shock oil: Big improvement in combination with 2 screws in the rear topdeck mostly because it shifted the tire temp balance again. The harder rear shock oil will heat up the tire during load transfer going into the turn and therefore got it closer to active temp.

3.0 rear spring: The mod guys used that, and so did I in 3 of 4 qualifiers. Heats up the rear tires quicker which helps but reduces slow speed steering. Steering fidelity got reduced which made nailing the end of straight chicane much harder.

Active rear shock mount: Must-use with 3.0 springs as it gives great steering toward the apex and allows the car to transfer the weight more easily, especially helpful on a bumpy track.

Kick-up: I went from 2.0/2.0 to 2.0/1.5 for one run. While it gave a bit more on-power stability, I felt like I was sacrificing too much for the benefit, so I went back to 2.0/2.0 initially. In the end I used 2.0 / 1.75 which was spot on as it is just enough kick-up to square up the rear, but not so much that you loose steering.

Twister vs. Wolverine Wing: I was sure that switching from a Speciale to a Wolverine would not make anything better I was currently working on, so I fine tuned the Speciale. On used tires I quite liked the Wolverine (0.5) wing, as it gives the car a bit more flow. On new tires, the standard Twister wing is great. I have not tried the Speciale wing because not enough time, but I would wager that it'd be rather good.

TL/DR: Twister wing = save; Wolverine wing = flowy.

Batteries: I have been using NOSRAM ULCG 5100 packs with a 25g weight plate and 6100 packs in practice. This way, you can change the battery type without changing the car's balance. As written in my previous reports, the 5100 is almost good enough for 5mins. I was told by those who practiced at this track, that the last 3 laps drop off though, so for qualifying and finals I went for 6100s. But as a 6100 is the same as a 5100 + 25g, my car always felt great.

3.5deg toe-in: I was hesitant at first, because there was a lot of talk about straightline speed etc. but going up to 3.5 static really helped with creating enough energy input into the rear tires.

Down to 3.0mm toe-gain: When I went up with static toe-in I found the car to feel slightly off. Reducing toe-gain to 3.0 freed it up again and made the roll feeling natural. I generally always look at the bumpsteer and toe-gain link angle in context – so is to say, it needs to match the rollcenter / wishbone lines somehow. This really impacts the cars natural feel.

Back to 2.9 rear spring: For the finals I reverted back to the 2.9 rear spring as the toe-in increase would give the tire the energy input otherwise lost with the softer spring. This proved to be the right choice, as it turned steering fidelity all the way up and it was so easy to get the lines right and even readjust them underway.

Probably had one of the best cars in the field.

TL/DR: the final setup produces a pretty even tire wear pattern while providing all the steering you need and then some. Easy to place, very reliable in repeat performance and it works with both new and used tires. Alex Stocker used pretty much the same setup in 40+ with great success.

I'm happy that I got back in shape, managing to do a no warm-up ‘hot start' in qualifying on new tires and no fuck it up. Used to be my parade discipline and I am happy to be able to still do it.

We shall see how the tire situation unfolds until the next ETS. Until then, this setup should provide a pretty decent starting point (also works with other tires).