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E39 M5 and E52 Z8 Discussion 1998-2003 Advertiser's Forum

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post #51 of 64 Old 15th May 2013, 02:13 PM
JimBeemer
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Originally Posted by Essixtytwo View Post
*Cough* mid 40's is NOT old! *cough*
Age is a state of mind, however, the older you get the more bad health habits and family genetics tend to catch up with you. I've tracked my M5 at Gateway in IL and at my age I realize my reactions are not going to be what they were at 25 or 40 before I get out on the track. I agree with your observations. Although I love the PS2s they can get chewed up fast at the track. I also learned that lesson the hard way and went through a set in 5000 miles after two sessions at Gateway. The brakes are the weak point on the M5 because they have to stop a lot of mass and my old M5 had the Brembro's on it that I loved. There's an old post about the Ring Taxi E39 M5s being relatively stock except for upgraded brakes. You had fun, did no significant damage to yourself or the car, and learned how the M5 performs at its limits. I agree with the advantages of keeping the DSC on for the first few track days. The Z06 has a great setting called "competition mode" on the traction control that is a cross between no traction control and full traction control that is great at the track. But even with the DSC on the rules of physics apply and if you push too hard, Newton's laws of motion will apply. It's always amazed me how people on the track think traction control can save them from poor decision making! Glad you enjoyed your M5 the way it was meant to be enjoyed!

Jim
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post #52 of 64 Old 15th May 2013, 02:51 PM Thread Starter
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Originally Posted by gsfent View Post
I will disagree with this point.

Given the nature of the car (4000#), and the relative track skill level of the driver (no slight intended), I would go with Motul 600. Much higher dry boiling point. Better margin for safety. A little more $$$, but a lot less $$$ than hitting the Armco when you run out of pedal!

Regards,
Jerry
No slight taken. Facts are facts.
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post #53 of 64 Old 15th May 2013, 02:55 PM
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Originally Posted by bimmerule View Post
Last I checked, Castrol SRF costs ~10X that of ATE brake fluid. Some clubs mandate fresh fluid every 6 months even though SRF is good for > a year.

I'd seriously consider flushing the whole system, not just caliper bleeds, since it was OP's first time bleeding the brakes, it's possible air was introduced in the system.


and how do they know the age of the fluid? do they write on it?
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post #54 of 64 Old 15th May 2013, 03:16 PM Thread Starter
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Originally Posted by kris993tt View Post
Greetings from sunny Malaysia . Firstly, what a great car, the perfect M5 imho. I track and race regularly out here and thought I'd throw in some input. Firstly great advice from all here especially Apex 153 with this :-

1) Any upgrade will QUICKLY reveal limits elsewhere: Sticky tires put a lot more stress on your clutch and suspension.
2) Virtually none of the money spent on upgrades will be recouped. In the case of our cars, track upgrades will likely hurt us.
3) There's a very fine line between a track improvement and a street nuisance: I just removed my Pagid pads, due to excessive noise (even by my standards).


It's a long slippery slope and I went down it with my 993tt. Mods here, tweaks there to the point that she's a blast to drive on short runs and awesome on track days but just too hard core to go out for a long drive. Long and the short of it, you go down that road and you'll start to progressively get a better and better track machine to the detriment of her civility. You pays yer money, yer makes yer choice .

Having said that, there's somethings you could do.....

Switch out that brake fluid. I run Castrol SRF as I have noted that they don't get 'killed' that easily. Have run everything from ATE to Motuls and the SRF just beats them hands down. They don't boil that readily (very high wet boiling point which is the main criteria. Brake fluid being hygroscopic, they suck moisture out of the air like..... ) You don't have to flush them out or even bleed them that frequently for that reason. As others have pointed out, your brake fluid probably has boiled in the calipers where all the action takes place. Your DSC would have been partly to blame. When you mash the throttle coming out of turns the DSC will start to apply the brakes on selected wheels to stabilise the car. It will curb engine power somewhat as well but imagine left foot braking in a corner while keeping your foot on the throttle....

Brake ducts, plates anything you can do to divert cooling air to the front discs that do most of the work. You'll have better brakes on track days, the pads and rotors will also last longer.

Tire pressure and tire temps.

Pressure :-Try and have nitrogen in your tires. That's just a fancy tag for dessicated air. The moisture in the air is what mainly causes pressure to rise with temp and your tire temps will rise when you track. Some tires shops will offer that. You haven't mentioned what pressures you were running. Baseline tire pressures for your car (and this just a guess, if someone knows the actual numbers please chip in) 2.5 bar or around 35 psi. This should be measured when the tyres are hot (after at least 5 laps). If you started with those numbers when cold, your tire pressures could have spiked to as high as 3+ bar.

Temp :- I'm assuming you don't have a temp gauge. Invest in one, a contact type with a probe you can stick into your tire. Take tire temp readings across the full width of your tires (all four of them) Outside (about an inch in from the sidewall), center and the inside. Do this after you have done at least 5 hard laps then take them immediately along pit lane if possible (but in a safe position). The quicker you take them the more accurate your readings. Get someone to record them as you're taking the temps. The temps will tell you a lot about not just your pressures but your suspension and alignment settings. Some info here ELEPHANT RACING Tech Topic, Tire Temp

One final note on the DSC, would your track day/club allow you to run just DTC which is a subset of the DSC? It's not as aggressive as DSC, will allow you more leeway and I think might throw less fault codes when you track her as DTC doesn't interfere with the engine (if I'm not mistaken).

Good luck and enjoy your ride!



Kris

Kris

Thanks for all the great information. I appreciate you taking the time to reply.

Regarding tire pressure. This is another area I didn't get right. The paperwork from the track had some vague suggestion about having your tire pressure at least 5 lbs over the max cold pressure - or something like that. Well I normally run about 40 in the front and 35 in the rear when trundling around town - trying to combat outer edge wear in the fronts and center wear in the rears. The door jam sticker is also rather confusing to me and indicates a max pressure of 46 psi! So five over that would be 51!?!? Seems really high. I ended up setting the pressure at 45 all around. After the first session the pressure had risen to 51, so I bled it back down to 45 while the tires were hot at the suggestion of my instructor. Thoughts on this?

You are right that I do not have a temperature gauge. Sounds pretty hard core.

Here's a dumb question maybe: How do you set the e39 DSC to DTC? I thought it was just on or off.

And one more question: I'm sure this has been covered ad nauseum in other posts, but does opening the brake ducts have any downside for daily drivers? Why did BMW close them in the first place even though the duct work is in there? Seems dumb!
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post #55 of 64 Old 15th May 2013, 06:40 PM
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I agree on the Miata as choice. Regarding your very first track day - take it easy! My first was with a 911 on all seasons, and running anything past 7/10th didn't make sense for me. I guess if I had unlimited funds, sure, drive it like you stole it. But there is a lot to learn to drive fast and save your tires and brakes, etc. As much as these cars are built for performance and can be raced, some things just have to be replaced and upgraded beforehand for maximum speed: pads, brake fluids, tires. So if the goal is to have fun with your DD, you can get away with it by learning how to drive fast and conserve your resources. If the goal is to win, you'll still have to learn how to drive fast, but you'll be upgrading a lot of components!
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post #56 of 64 Old 15th May 2013, 08:29 PM
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Quote:
Originally Posted by kris993tt View Post
Greetings from sunny Malaysia . Firstly, what a great car, the perfect M5 imho. I track and race regularly out here and thought I'd throw in some input. Firstly great advice from all here especially Apex 153 with this :-

1) Any upgrade will QUICKLY reveal limits elsewhere: Sticky tires put a lot more stress on your clutch and suspension.
2) Virtually none of the money spent on upgrades will be recouped. In the case of our cars, track upgrades will likely hurt us.
3) There's a very fine line between a track improvement and a street nuisance: I just removed my Pagid pads, due to excessive noise (even by my standards).


It's a long slippery slope and I went down it with my 993tt. Mods here, tweaks there to the point that she's a blast to drive on short runs and awesome on track days but just too hard core to go out for a long drive. Long and the short of it, you go down that road and you'll start to progressively get a better and better track machine to the detriment of her civility. You pays yer money, yer makes yer choice .

Having said that, there's somethings you could do.....

Switch out that brake fluid. I run Castrol SRF as I have noted that they don't get 'killed' that easily. Have run everything from ATE to Motuls and the SRF just beats them hands down. They don't boil that readily (very high wet boiling point which is the main criteria. Brake fluid being hygroscopic, they suck moisture out of the air like..... ) You don't have to flush them out or even bleed them that frequently for that reason. As others have pointed out, your brake fluid probably has boiled in the calipers where all the action takes place. Your DSC would have been partly to blame. When you mash the throttle coming out of turns the DSC will start to apply the brakes on selected wheels to stabilise the car. It will curb engine power somewhat as well but imagine left foot braking in a corner while keeping your foot on the throttle....

Brake ducts, plates anything you can do to divert cooling air to the front discs that do most of the work. You'll have better brakes on track days, the pads and rotors will also last longer.

Tire pressure and tire temps.

Pressure :-Try and have nitrogen in your tires. That's just a fancy tag for dessicated air. The moisture in the air is what mainly causes pressure to rise with temp and your tire temps will rise when you track. Some tires shops will offer that. You haven't mentioned what pressures you were running. Baseline tire pressures for your car (and this just a guess, if someone knows the actual numbers please chip in) 2.5 bar or around 35 psi. This should be measured when the tyres are hot (after at least 5 laps). If you started with those numbers when cold, your tire pressures could have spiked to as high as 3+ bar.

Temp :- I'm assuming you don't have a temp gauge. Invest in one, a contact type with a probe you can stick into your tire. Take tire temp readings across the full width of your tires (all four of them) Outside (about an inch in from the sidewall), center and the inside. Do this after you have done at least 5 hard laps then take them immediately along pit lane if possible (but in a safe position). The quicker you take them the more accurate your readings. Get someone to record them as you're taking the temps. The temps will tell you a lot about not just your pressures but your suspension and alignment settings. Some info here ELEPHANT RACING Tech Topic, Tire Temp

One final note on the DSC, would your track day/club allow you to run just DTC which is a subset of the DSC? It's not as aggressive as DSC, will allow you more leeway and I think might throw less fault codes when you track her as DTC doesn't interfere with the engine (if I'm not mistaken).

Good luck and enjoy your ride!



Kris
Some good info, but I disagree on a few things. Remember, just my opinion.

1. Boiling Point. Dry is important, not wet. If you are concerned about wet boiling point, you are not changing your brake fluid often enough. Since these brake fluids are hygroscopic, they will absorb moisture out of the air. But during a weekend of driving, there is no practical absorption. So if you put in fresh fluid before your track day, wet boiling point is virtually irrelevant.

To that end, SFR is slightly better than Motul because it is not as hygroscopic, but they have similar dry boiling points. If you are racing, the additional cost is worth it. In the HPDE world, I suggest it is not. If you are boiling the Motul 600, there is an issue with your choice of pads, lack of air to the brakes, or driving style. Most novice drivers spend way too much time on the brakes, causing additional heat. As Stig Blomqvuist observed (great Saab rally driver), "brakes only slow you down"!

2. Tire Pressure/Temps. Depends a lot on which tire and suspension setup as noted above. You also need to consider which corner gets the most abuse/wear. Since most tracks run clockwise, most of the stress is on the left front. That is the tire that needs the most attention. I suggest on heavy cars like ours, you are look for 38-40 or 41 psi hot. The best way to measure is to use a tire pyrometer as noted above; the "down and dirty" way is to chalk the sidewalls to see how far the tire "rolls over" in a turn. If you are driving hard, that will tell you if you are under or over inflated depending on how much rollover there is on the tire. Expect 5-8 psi growth in pressure, depending on driving style as well as ambient temperature.

For starters, on a clockwise track, I will setup my right front and left rear about the same, 1-2 psi below LF, and RR another 1-2 psi below LR/RF. Measure in pit lane is best, since even on the cool down lap you are losing a slight amount of pressure. The longer you wait (going into the pits) the less accurate the "hot" measurement is. On the M5, I would start the LF around 34-35 psi.

BTW, I don't believe in nitrogen. It does make the tire pressure ever so slightly more stable, but ignoring most tracks and weekend warriors don't keep nitrogen with them, and tire pressures within 1/2 psi won't be noticeble, a waste of effort. No harm, just no real benefit.

3. I don't believe we have DTC. DSC uses brakes and/or cutting the engine, I just don't remember which goes first ( I think brakes). Spinning rear tires can be helped by more judicious use of applying power out of a turn (we do have some limited slip). If you take the diff apart, you can increase both the static and dynamic lockup. It is the dynamic that will really help prevent wheelspin, but if it is apart..........


Regards,
Jerry

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post #57 of 64 Old 16th May 2013, 04:02 AM
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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.


cheers ,
Kris
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post #58 of 64 Old 16th May 2013, 02:37 PM Thread Starter
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Thanks again Kris. Enough information here to keep me totally non-productive all day!

Now, if only I knew how to check the tire pressure . . .
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post #59 of 64 Old 16th May 2013, 02:47 PM
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The E39 only has two settings for DSC. On or off.

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post #60 of 64 Old 17th May 2013, 02:44 AM
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You're welcome Crawford
Productive? When there's so much fun to be had out there ?

I use this to check my tire pressures. Digital Tire Inflators - PCL

In back to back tests with dial type gauges I found discrepancies of as much as 3-5 psi between them . This is really accurate and doubles up as a tire inflator if you have an airline connected to it. Makes the task so much easier!

cheers,
Kris
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