You're welcome Crawford
Tire pressures are directly linked to your contact patch and tire temps which is why I advised investing in a tire temp gauge. Here's the one that I have Intercomp Deluxe Pyrometer - JEGS
The link that I sent earlier from the elephant racing site tells you what's happening from the different readings. Getting the tire temps even across the tread with the right pressures and alignment settings will be the single biggest thing you could do to the drivability and response of your car on track and save your tires to boot as under or over inflating them will lead to increased/uneven wear
The pressure I offered as a baseline , 35 psi, was just a rough guess. 41 as advised by Jerry might be a good start as well and you should be able to tell if the car grips or handles better with either of these 2 settings. Note these are all 'hot' pressures as there are too many variables to contend with starting from cold. The tire temp/pyrometer though will allow you to drill down to the best setting. The owners manuals/door jamb stickers are a cause for confusion to me as well
. It says 46 psi cold on my Porsche which my dentist loves as it knocks out all my fillings
but these days I run with 35 frt and 38 rear.
Running different tire pressures across an axle? That would lead to inconsistent handling imho. Unless you're running an oval... Even a clockwise track will have both left and right turns and the car has to handle consistently through both. Having the same 'hot' pressures all round (staggered maybe to allow for front/rear weight bias) will allow this. Once you have your hot pressures set, the tires across an axle will react in an identical manner in terms of maintaining the contact patch which is what you want.
On Nitrogen/Dessicated air, if it's easily available, fill up on it. This all adds up to consistency in tire temps and the performance and handling of your tires and ultimately your car. Deflate your tyres then reinflate with the nitrogen. You dont have to do this at the track and in fact run your tires with nitrogen all year round as I do. If it's not easily available, one thing you could do before inflating at any source is stick an old tyre valve (or a pen if you know what you're doing) into the valve of the inflator (making sure it's discharge is pointing away from you and somewhere safe). If a stream of vapour comes out or worse actual water droplets wait a couple of seconds. If it doesn't clear DON'T inflate there. Move on. It's water vapour from poorly filtered systems in the air line and it's that component that leads to spikes in tire pressures. Having clean dry air in your tires does make a difference and is worth the effort
On brake fluids, the general consensus (especially for track guys) is that the wet boiling point is the main criteria. A discussion here on this topic Brake fluid question - dry vs wet boiling point - Rennlist Discussion Forums
As Jerry has stated though, if you flush out your brake fluid before a track session, then you're probably fine with alternatives but if not... I only flush out my system once a year after almost daily driving and at least 1 track day a month
And some admittedly anecdotal evidence, I run a 490 Hp 993 TT at the track
. She weighs in at around 1560 kgs (3430 lbs). Stock brakes (Porsche big reds) but running on Pagid RS Yellows (squeaky bloody things). Driving her hard will result in the pedal going to the floor within 5 laps of Sepang circuit Sepang International Circuit - Wikipedia, the free encyclopedia
. Switched to SRF and no problems. They are expensive unfortunately but if you deck that against the cost of brake upgrades like larger rotors and bigger pads (with consequential increase in periodic replacement costs) they don't look so bad.
You could be right about the DTC Jerry. I don't have an E39, only the E53 and E63. With them, I have the option to turn DSC off and run just DTC. Not sure if you can do it with the E39 but if you can, some explanation on the differences here Dynamic Stability Control: Explained | BimmerFile
Excerpt here :-
DSC is ON by default, there is no need to press any buttons on start up. DSC uses a series of sensors to detect wheel spin, yaw rate of the car and other properties. Using sensors and other electronics it can apply the brakes as needed, cut engine power and with Active Steering it can make small steering corrections to better keep the car under control.....
In some models, DTC (Dynamic Traction control) is a sub-function of DSC. It is activated by briefly pressing the DTC button. A light will light up in instrument cluster indicating this function has been activated. DTC will allow the wheels to spin, increases the angle at which the system will begin to apply the brakes (eliminates the yaw rate sensors) and does NOT cut the engine power....
Didn't know there were brake ducts in the E39 that were sealed off but this isn't unusual. Manufacturers have to have certain features in their cars for homologation Homologation (motorsport) - Wikipedia, the free encyclopedia
to allow that part in their competition efforts like touring/saloon car racing. They don't carry through with full functionality for whatever reason (Venus crossing Mars maybe
) but the part has to be there to comply.