DB9 with Nitron NTR shocks results in excessive TC

[mhpcto]

Hi,

I have been working with Nitron in the UK to build up a NTR Race damper kit for the DB9 and finished installation of the kit a couple of weeks ago. Will actually post a more detailed report on the experience and about the dampers once they are fully dialed in.

In any case, I did about 100 miles to let the dampers settle then adjusted the ride height. Spend an additional 300 miles to get reasonable baseline settings for hi/lo compression and rebound. The settings are on the firm side (basically a track-day setup) as I want them to mainly work on the mountain roads (Hwy 9 here in California) and that's working out quite well. In essence, the settings are on the firmer side with -8,-8,-6 of (25,25,16) for rebound hi/lo compression.

I noticed that, as I upped the pace, now the traction control light keeps flashing into and out of every turn taken at speed. Particularly, I get the TC light on the downhill section, entering turns on neutral throttle. Admittedly, the Nitron's allow for higher corner speeds, but not at the traction limit of the tires - I am still below or at the speeds I would carry in the S4s.

I am wondering if there is a way to adjust/re-calibrate the TC system for the stiffer setup?

[mhpcto]

Johnny42 said:

Agree, the TC is stepping in because it's detecting a loss of traction. A tyre is leaving the tarmac. If the road is smooth, it's probably not level around the corners and it's so stiff you're cornering on 3 wheels. Have you tried it on a track? The corners will be more level.

I did a run with TC disabled and my buttock sensor is telling me that TC is overly sensitive as I don't get any undue slides or wiggles. The current settings keep the car quite controlled and level - vast improvement over stock or stock shocks with H&R springs, which I ran for a year.

Going through the same section of road in a BMW 550i with somewhat worn sport suspension (the car has 100K miles on it), it triggers that car's TC as well, but mainly on acceleration out of the turns, which is expected.

In any case, I have run the Nitrons briefly on the softest settings and don't think the spring rate is excessively hard for road use. It's comparable to the rates of the Penske shocks I had on the S4s, which worked very well for daily commuting.

Yes, the TC activating would indicate that the load on at least one of the tires causes it to slip. Considering that this happens on corner entry or mid-corner it would be weight transfer to the outside wheels. Shouldn't the TC account for that and let the inside one slip? That was sort of the gist of my original question (sensitivity adjustments vs turning TC off).

I am sure I can find a setup that minimizes TC kicking in (start by lowering rebound damping) but I really do like the balance with the current settings but don't need to leave tire marks all over the road with TC off.

Having 3-way adjustable coil-overs does introduce a significant level of complexity in trying to make them work. Being fundamentally track dampers, they will always be a tradeoff for commuting on a combination of city, freeway and mountain roads. Perfectly willing to live with that.

And to make it clear, I am just a regular Nitron customer, having chosen them over Penske because they were willing to work on putting together a coil-over combination that works on the DB9. Due to the geometry, this meant piggy-back reservoirs at the front and remote ones at the rear.

[mhpcto]

rhinochopig said:

Track dampers for use on the road is the problem. They often get specced with too high a spring-rate for road - even smooth road use. They also typically reduce wheel travel and can affect the roll centre of the car without appropriate compensation as they usually result in a lower the ride height.

The myriad damping options also make it easy to get wrong - at one end a floaty feel at the other the damper 'packing' down.

IME they'll make you slower during road use as the car will be so stiff that the transient between grip and slip is very fast making, it intimidating to drive.

Have a look at the following vid - it's in German - but you can see the difference between road and race spec dampers and the affects they have on handling.

https://www.youtube.com/watch?v=r7H4LcJLgKQ

I can't help you specific settings for an Aston but having used Nitrons in the past they are a good damper so you can probably find a setting that will work. My advice would be to get it as close to the stock road setting as possible and then work from there ironing out the specific issues you have with the standard car.

If it doesn't work out with the Nitrons give these chaps a call http://www.exe-tc.co.uk . I've used them in the past and they are superb. God knows how many WRC championships to their name certainly means they know their onions. And there is no faster vehicle down a smooth or bumpy road than a WRC car.

That said if you live in the US, why not use a US manufacturer as it will make dev far easier and cheaper.

All true. I have a bit of experience with race dampers, having run Penske Race coil-overs in the Esprit S4s and a Corrado for both track days and commuting. I have always found a setting that suits my driving style and gives me the feedback I want. My question was specific to the sensitivity of the TC system as the difference between stock+H&R (which are a bit stiffer than stock but the damper/H&R combo is woefully underdamped - not enough rebound - and makes the car pogo quite a bit) is very noticeable while being faster, more stable and more controlled through the turns at the same time.

I chose Nitron because they have a product for the Vantage, which I thought would serve as a baseline for the DB9 setup while Penske would have had to start from scratch. Anyway, Nitron now has a US subsidiary.

[mhpcto]

divetheworld said:

So your response is the OEM TC must be at fault?

Nope - just that it's overly sensitive and that, for a stiffer setup, it would be nice to be able to adjust that. Which was the question I was asking.

[mhpcto]

mikey k said:

I've found the Aston TC on both mine to be overly sensitive (even on stock sports pack)
The S had three stage and the middle setting (track) was a lot better
Don't think the DB9 has that though?

That's what I was implying in my original post. I was hoping that someone may have found/figured a way to 'tune' that sensitivity.

The DB9 TC is actually pretty damn awful - at least in my '05 - under acceleration, cutting power too abruptly.

Anyway, I will soften the setup a bit, dialing out some rebound to see if that makes a substantial difference. It's actually not a driveability issue, it's just the TC indicator flashing like a strobe light :-)