So after a crazy few weeks here, I've finally managed to make it back to the track, with a full days testing at the local outdoor track, in low-med traction.
It's pretty warm out here at the mo as well, creeping up into the high 20's, so 36's were order of the day.
Had a big list of stuff to try out, and pretty much got all of it done... so here we go!
Started out with the setting's in the first file, which is where I ended up last time at Cotswolds, and is based off of Steen's GC setting. To be quite honest, at that time, the car was poo. Really didn't work well in the low traction levels, very difficult to drive, not stable, and lacking steering... so basically all the things you don't want!
Anyway, general plan of action was to get the baseline with that setting, and then work through a program of roll centres, roll bars, springs settings, IAS, and then upper link positions.
First run was as expected really, car felt really hard to drive... skating across the surface (which could be expected as others were sliding around a bit too), no bite, and if even only slightly over-cooked into the corner, rear would just step out... felt more like driving a drift car than a TC.
First change was to switch back to the symmetric damping, and this was a marked improvement, car biting into the surface better, and a more reactive feel. Still the balance was off, but at least could predict it better. Still not overly happy, but an improvement... I think Sym will be staying on my car for the foreseeable future.
Next change was the bigger one I'd been planning... completely altering the roll centre on the car, lowering the rear a huge chunk, and raising the front a little. Rear end, removed the 0.5mm spacers from underneath the lower arms, putting 4.5mm under the rear inner link, and 3mm under the outer. On the front, just raised the outer link 0.5mm to 2.5mm. The intention was to create a similar roll-centre balance to other cars on the market, with a higher front than rear.
At the same time, I also hardened the front damper 1mm (matching the rear, and as on most other chassis), although kept the spring the same, and switched to an LTC-R shell. A pretty big amount of changes, but I decided not to muck around..
Anyway, on track, big step forward. Could actually push harder into the turns, without the rear stepping out, which certainly wasn't the case before, even using the Speed6 shell. The LTC also helps with the steering issue, much much better in the high-speed sweepers, with barely a lift needed now, compared to before's full backing down of the throttle. Laptime improved by well over a second (long 24s lap though), so that was a big positive! Car did slide around a little if I got really aggressive, almost carrying too much steering.
Next run, moved the front spring 1mm harder, and changed the rear diff oil to Losi90 from 80. Both changes helped to make the car more stable into the turns, and take away some of the steering, although there was still a slight slide possible. Diff change also helped to gain some on power steering.
IAS was next up on the list. I'd pre-prepared the IAS for a quick swap whilst at home previously, even going as far to program another model memory in the handset. From previous experience, the IAS seems to give more steering, but at the expense of corner speed... and I have to say, this time round, I didn't get on with it at all. The steering feeling was very strange and non-linear. Lots of initial, but then stopping the car in the middle of the corner, which made it very hard to be smooth through the whole turn. Back in the pits, came straight off and back to the original steering! Maybe it'll work for small tight and twisty, but for a big flowing track, it's a no-no IMO.
Final run on the Sorex's, I went back to trying out the front reactive castor again (1.5mm F, 2.5mm R), and raising the rear link even further to 5mm under the joint. This again was another step forward, car gaining a bit more in the middle of the turns, but still stable.
With that run done, it was time to change the tyres, as the temp had got too hot, with the 32's losing rear traction towards the end of the run. So I popped on some Team Powers 36's, as these were a) available and b) being used for Reedy, so figure it's maybe something that can help out there..
The setting's themselves seemed to work really nicely, and the car gripping better than the (admittedly a bit knackered) 32's.. also stayed alive the whole run, although with a bit more of an understeer tendency than the Sorex's, losing a bit of on-power steering.
Talking with some of the other racers there, one suggested to try making the car a little softer to get it to roll more, as he commented that is had looked like it wasn't rolling enough. So for the next run, dropped the roll bars down a grade F&R (to 1.1F, 1.0R). On track, it felt ok, corner speed dropped, and the car started doing funny "wiggles" in some sections of the track, like it was lacking roll control, and making it hard to be consistent lap after lap. Suffice to say, the harder bars went straight back on for the next run, and the wiggle was gone.
To try and get the steering back, I adjusted the upper link shims for the next run, removing 1mm from under the rear links (to 4mm), and adding 1mm under the front (2.5/3.5). Now the balance was really good, back to being able to pick and chose the lines on exit, without feeling like the car was wanting to push to the outside. End of straight sweeper was also a good improvement. Quite happy with that setting, maybe could gain a little more initial going back to the softer front spring, but I really wanted to try upper front arm sweep before the day was out...
So, first test was to make the rear front upper link longer (so using middle hole on the front mount, and inner top deck hole on the rear). This change had an interesting feel on track, with it seemingly making the front roll more in the corner. It did feel like a bit of a gain in the middle as well, but not to the same extent as, say, reactive castor. For the last run of the day, I set up the sweep the other way round, with the rear link in the middle hole, and the front one in from full out... I was expecting the change to make the car feel more reactive on the front, but unfortunately an ESC issue stopped play, so I didn't get a chance to try it... and that was day over!
Still, pretty happy with the progress made. I got myself down to a 22.8 best time for the day, whilst the fastest at the track was a 22.0.. not great, but the fastest time was set on better tyres (Ride36) and by a driver who has spent many hours with a well sorted Yokomo, so given the setting was lacking a lot in the morning (24's!!), it was a productive step foward.
- Symmetric better in lower traction, gives car more feel, not floaty
- IAS binds car up mid corner, no linear steering feel, difficult to "flow"
- Lower rear roll-centre made car much more stable, able to push hard in turns, and use LTC-R for high speed
- Harder diff-oil worked well for stability in, steering out (duh!)
- Still don't like the feel of the car without roll bars, vague, inconsistent.
- Reactive castor felt good for mid-corner apex holding
- More steering needed on entry over finishing settings, more time, try softer front spring again