BMW540iFun.com
"Frequently Asked Questions"
(Use the information at your own risk!)
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I recommend asking Jim@Tirerack.com your specific questions.
Q) Is there any objective data on tire performance?
A) There have been some good tire articles from time to time, but the test they run have not been for the 5-Series cars. Click here for the best information I have found for our cars. TireRack provides this data for most level of performance tires.
Q) What is the cost / benefits of bigger wheels?
A) Costs: rougher ride, effectively decreases rear end gear ratio, more power steering pump pressure, more money not only the wheels but also the tires. In addition, if you add weight that will lower your effective horsepower; on an Acura it was observed that horsepower dropped by ten when it went from 16" wheels to 18" wheels.
Benefits: looks great, car may handle better, allows for bigger breaks, may stop faster.
Q) What are "staggered wheels" and what effect do they have on the car?
A) Staggered wheels typically means that the front wheels/tires are an inch or so thinner than the rear wheels/tires and will cause the car to understeer relative to if it had the same wheels/tires sizes all the way around. The reason for the understeer is that the back tires are sticking better than the front. A benefit to having wider wheels/tires in the back is more traction for straight line performance.
Q) What size wheels and tires can I put on my car?
A) For 17" Wheels: A 10" rim with will fit in the rear with a 255/40R tire and it is not expected to rub. If it does, you can roll the fender lips.
A) For 18" Wheels: 255s in the front and 275s in the rears will rub. You will need to roll the fender lips. If you go below 275 in rear you should not have to do any fender modification to have them fit, but they will rub. 285s will rub even if you roll the fender lips.
A) For 19" Wheels: 245s in the front and 275s will rub, you will need to get the fender lips rolled and need to get M5 wheel liners.
Q) Can you explain the numbers/codes on the tires?
A) Click here and here for an explanation provided by TireRack.
Q) How do I get rid of my understeer?
A) The reason we have understeer is that the car makers realized that it is easier to control understeer than oversteer since all it requires is to lift the throttle. Click here for some tips as to how to correct your car for both over and under steer.
Q) What are the benefits of after market wheels?
A) After market wheels are bought for primarily three reasons; 1) aesthetics 2) weight reduction and 3) allows for bigger brakes. The weight reduction varies, in my case, my 17" wheels (M66) weigh 23-24 lbs. The M5 wheels which are 18x8, 18x9.5 weigh approximately 23 lbs and 25 lbs front/rear respectively. AC Schnitzer wheels that are 19" weigh about 23lbs; Dinan 18" wheels weigh approximately 18lbs. So you can get bigger, good looking, and strong wheels without adding and in some cases reducing car weight, but they are very expensive.
Q) Can I put 245 sized tires in front and 255 sized tires in rear?
A) You should not, the tires have different heights and will cause problems with your anti lock brakes and traction control.
Q) What are the speed ratings on tires?
A) Q=100, R=106, S=112, T=118, U=124, H=130, V=149, W=168, Y=186, Z=149+ "Z" designates speed tire.
Q) What is / causes "wheel hop"?
A) Click here for a discussion thread on the subject matter. It is several threads posted at different times and e-mail exchanges.
Q) What is sprung and un-sprung weight and how does it apply to changing the tires or wheels?
A) This is a technical issue, you will need to click here for some threads regarding the subject matter. I would start at the bottom, where someone gave an analogy of the difference of running with light tennis shoes vs. combat boots.
Q) What are Strut bars?
A) Strut tower braces metal braces go across the car and are attached to the front and rear shock towers to reinforce the body and increase overall rigidity of the body. These braces prevent the shock towers from flexing under heavy suspension stresses in order to increase handling and preserve correct suspension angles during hard cornering. Plus, they look cool. Answer was adapted from www.bmwtips.com. These also tend to work only under extreme cornering such as in autocrossing and track events and with other high performance suspension components such as the springs, shocks, and sway bars. One downside is in cases of a side collision, the strut bar could cause damage because it transfers the impact to the opposite side of the car.
Q) What are Sway bars?
A) Sway bars mount on the bottom of the car and serve to tie the lower ends of the left and right sides of the suspension together. Thick sway bars tend to decrease body lean during cornering and decrease grip at the end of the car that you install them on. For example, if you have a car that has a mild understeer, as most cars do, adding a thicker rear sway bar will cause the rear of the car to lose grip and come around sooner. Thus, the car will now corner flatter and become more neutral. Front sway bars cause cars to push more and rear bars cause cars to oversteer more. The effect is similar to increasing the overall spring rate on that end of the car. Answer was copied from www.bmwtips.com.
Q) Does it help to just put in a stiffer rear sway bar in the rear?
A) Yes, and it is a relatively easy thing to do. If you want a little better handling (less understeer) you may try installing a M5 sway bar and see if that meets your needs before going with a much more expensive route.
Q) What can you tell me about the different suspension manufacturers?
A) Click here for a post that provides the general opinion.
Q) Do you have any information about the different vendors products and what they do to ride heights?
A) Yes, click here for a fantastic ride height survey by Viestsb.
Q) What kind of limited slip differentials can I get for my 5er?
A) I have read about three options 1) the Quaife differential and 2) adapting the M5 differential. An example of how this is done can be found at www.bmwtips.com under "Tips and Tricks" and 3) you can purchase one from Dinan.
The gentleman that installed the M5 rear end conversion considers putting in the Quaife much easier, David Zeckhausen writes "For the Quaife unit, you simply swap out the "pumpkin" with the modified unit. To put an M5 limited slip in your car, you'll need to swap out the drive shaft and half shafts as well. And, of course, the exhaust has to come out to get at the driveshaft. That's not much fun."
Click here for a discussion on comparing the two limited slip system.
Q) What is the difference between a Limited Slip Differential and what comes as OEM ("peg leg")?
A) Click here for a discussion thread on the subject matter.
Q) What are the cost benefits of going from a 2.81 gear to a 3.15?
A) Going from a 2.81 to a 3.15 will reduce gas mileage by 1-3 miles per gallon and reduce your top speed in each gear, but you will pick up more torque. You should reduce your 0-60 time by about .15 seconds and could see a reduction in your 1/4 mile. The reason why the gear change may not reduce your 1/4 mile time is that the gear change will cause you to do an extra shift (3rd to 4th) that is not necessary if you stick with 2.81 gear. Folks believe that it will cut down your 1/4 ET anywhere from .2-.6 seconds.
On E39s the gear swap is fairly straight forward.
Q) How noisy are the aftermarket exhaust systems?
A) Some are noisier that others, the Dinan exhaust sounds good without being overbearing. The Super Sprint mufflers is quieter (I think looks better) but it may not release as much horsepower. Go to BMW TIPS.Com under "Tips and Tricks" for some sample sounds and to get some specifications.
Q) What is a cat and a resonator?
A) A cat is a catalytic converter and they help reduce the emissions. I believe most states require that cars have them. A resonator is designed to contain specific volume of air and has a specific length that is calculated to produce a wave that cancels out a certain frequency of sound. Click here to see photo of an exhaust system. Photo is courtesy of Daniel D. Bauer. If you want to know how this stuff works go to www.howstuffworks.com.
Q) What do the different exhaust systems sound like?
A) Magnaflow 2.5" oval cats, resonator removed and replaced with 2.5" pipe and OEM muffler sounds like this! (Courtesy of Electroman)
A) Super Sprint exhaust without a resonator (3" inch pipe replacement) sounds like this! Click here for another one (compliments of PropellerHead), except it is in video form.
A) This is a video clip of a Remus exhaust without a resonator (3" inch pipe replacement) and high flow cats sounds like this! (Courtesy of Daniel D. Bauer) Click here for some information on Magnaflow/Carsound cats.
A) This is a video clip of a Remus muffler without a resonator but OEM cats, click here. (Courtesy of Saman)
A) Dinan exhaust with Magnaflow cats and Walker Dynomax resonator (bullet muffler) sounds like this! (Courtesy of beyemvey)
A) Dinan exhaust with OEM cats and Walker Dynamax resonator sounds like this! Courtesy of humanoid (www.Dinan540.com).
A) Dinan exhaust with OEM resonator sounds like this. 1st big rev was to about 4K rpm, the next one was about 6K rpm. (mine). This is mine now with the resonator replaced by the Walker Dynomax resonator (bullet muffler). Like the clip before the 1st rev is to about 4K and the next to about 6K, click here. Both of these sound clips were done inside an open garage. This clip is of mine outside the garage. The first sounds are with the microphone beneath the exhaust tips (like before) then I recorded the sound with the microphone on the passenger side about a foot away from the car. The second part of this clip sounds closer to what one would hear.
A) This is a video clip compliments of humanoid (www.Dinan540.com). It contains the following: 1) Remus exhaust, resonator removed, 2) custom quad exhaust, resonator removed, 3) Dinan exhaust, Dynamax Racing resonator, 4) Quad Remus exhaust, resonator removed (I really love this one). Click here.
A) This a video clip of the Quad Exhaust Hamman DTM. You can see the car and exhaust lay out by clicking here. To hear and see this set up click here. (Courtesy of Saman)
A) Click here for a video clip of Smooth6 dyno run he has Dinan M5 Muffler, Magnaflow Hi-flo Cats, Magnaflow 6" Round Resonator, Custom 2.75" SS Piping
I also know of people who have tried to take the resonator off with a Dinan muffler and have felt that it is too loud and have put the resonator back on.
Q) Do front spoiler add any value other than aesthetic?
A) Representatives from Hartage and Hamann both told me that there spoiler provided aero performance but could or would not provide any objective information. Both said that the front spoilers did not provide additional down force.
Q) Why should I consider putting on "big brakes"?
A) Mr. Dave Zeckhausen of Zeckhausen Racing has an answer.
Q) What is the best braking system that I can buy?
A) Most are partial to a Brembo braking system. In September 2002 "Car and Driver" had an excellent article called "Shedding Light on Fading Brakes" where they did some brake tests on a Subaru WRX. The Brembo F50 system had the best results with StopTech a close second. Zeckhausen Racing has some Stop Tech test data.
Q) Will after market brake systems fit in my wheels?
A) Depends on your wheels. It seems that the after market brake systems generally fit in 18" or larger wheels. Some systems do fit in 17" wheels, but you will need to ask. The M5 brakes for example will fit in a M66 style wheel like I have. To change to M5 brakes will require you not only to get the brakes, but you will also need to get the rotors which are directional (ours are not). The M5 brakes are bigger there measurements are 345MM x 32MM versus our which are 324MM x 30MM.
Dave Zeckhausen has installed Brembo big brakes on M66 wheels but it took some special work.
Q) What is the deal with "crossed drilled" and "slotted" rotors?
A) They are purely cosmetic and they diminishes the rotors durability and cooling capacity.
Q) Should I upgrade my brakes or brake pads?
A) Depends on what you are trying to accomplish, if you have experience brake fade often or plan to run your car on a road coarse, you may want to upgrade your brakes. If you want more stopping power in day to day driving, then replacing your brake pads may be the answer and save you lots of money.
Q) What about the brake fluid?
A) If you are going to do track events you may consider switching brake fluid to one that has a higher boiling point and consequently won't get "spongy". The following brake fluids have been recommended: EXP 600 Plus and Motul 600.
Q) Is the OEM brake pad the best?
A) Best way to answer that question is to read the write up below which is published at BMW Tips.Com. I felt like I need to edit some of the language.
My experiences with the different brake pads!
(archive link: http://www.bimmer.org/5series/messages/archive/msgsy2001w34/14291.html)
Posted by Saman on August 25, 2001 at 08:22:55:
For the past two years or so, I've been in search of the perfect break pads,ie. no noise, no warping of my rotors, good grip, and very important dustless. Here is what I've tried.
1)OEM pads: We all know, they are rotor friendly, ok grip, but dust like crazy. This is why we all try to upgrade.
2) Mintex C-pads: Grip better than oem, dust was reduced about 50%, but warped my rotors in 3 months. And minimal noise. Another enthusiats wrote that he had warping & noise problems with his Mintex red-box pads.
3) PBR/AXXIX Delux pads: Put these on my brother's 325.Very rotor friendly, no noise, dust was the best about %75 reduced. Grip was about oem's level. I would like to add a note on this pad. They now make the Deluxe "Plus" Pad that provides greater fade resistance and dust less than OEM and are generally thought to be the best pads for the M5, 540i, 530i and X5. You can purchase these through Zeckhausen Racing, ask for Dave who has been a wealth of information.
4) EBC green stuff: I f*&%ing hate this pad. After installing new rotors and this pad, the dust was just a tad bit less than oem (10-20%), was noisy as hell, and warped my rotors in 2 months. Piece of Sxxt.
5)I just replace my front rotors with Balo rotors, from Germany. I have heard they are very strong and do not warp. And a set of porterfield brakes rs4. It has only been about a week. There is some squeeking, the grip is quite good, but it is not as dustless as I thought it would be for a set of $169 pads. With oem after two days of driving you notice visible dust, with this about 4 days. So maybe about 50% less, not as good as the PBR delux pads.
Conclusion: I wish they made the PBR delux pads for the E39 front, they make it for the rear as of now. They are great pads, unless you are on the track. Stay the hxll away from EBC. Now, some people have said they have tried the Red stuff from EBC and it is good, but I don't know. Mintex is not that great either. Porterfield is ok, but I don't know long term what it will do to my Balo rotors. I hope this helps everybody that is always asking this question. If you have any experience with any other pads, please add info. Thanks.
Q) Should I turn my brake rotors if they feel warped?
A) Please click here for an expert opinion.
Q) What does a short shifter do for me and which one should I get?
A) It shortens the distance (throws) between gear allowing one to get back on the throttle quicker. These shifters tend to work better with a heavier shift knob, but it is not necessary. Here is the UCC and Whalen set ups. I have the UUC and am using it with the OEM knob and I am glad I got it. The shifter feels like one should on a sport model. I just could not stand those long OEM throws.
As far as which one to get, here is a post which I believe captures most peoples opinion:
| Posted by:
Daniel D. Bauer on 2002-12-13
at 17:35:01 (Roadfly member #26750; Roadfly Inner Circle member since 2002-10-29) |
In terms of aggressiveness (where "aggressive" means short throw and notchy), they rank as follows:
1. Rogue is slightly shorter throw than stock, and comes very close to maintaining the feel of the stock shifter.
2. UUC is slightly shorter, slighly more notchy, and slightly noisier.
3. B&M (which nobody else seems to have) is the most expensive, the shortest of all three shifters, and the notchiest by far. Notchiness was greatly reduced with the use of a heavy shift knob.
Don't get the WSR, I think it is a waste of money. Weight should be on top of shifter, not underneath. Spend the equivalent amount of money on a nice shift knob (Whalen Shift Machine is my favorite).
I've had both the Rogue shifters and now the B&M. Both are great. Just depends what you want.
Q) What does the "UUC Clutch Stop" do?
A) It replaces the OEM clutch stop and it keeps the clutch pedal from going all the way down to the floor which can reduce the amount of time it takes one to shift which makes your performance times better. On our cars you have to trick a safety system in that the cars are built not to start unless the clutch pedal is all the way down. Caution, it is a safety system. I have a write up on that subject and some additional information that can be found on my "Mod Experiences" link.
Q) What is the CDV and should I remove it?
Q) What is the difference between a super charger and a turbo charger?
A) Please click here for a short summary.
Q) What is the difference between the Dinan SC and ESS SC?
A) Click here for a write up courtesy of ViestSB. Click here to get to his DIY site.
Q) Is it possible to safely put NOS into the 540i?
A) Yes, click here for some informational threads and click on these to see some pictures...NOS1, NOS2, NOS3. Click here for a link to some technical information.
Q) What is Carbon Fiber and how can it be used on our 5ers.
A) Click here for some great information.
Q) Do you have some information about fluid levels?
A) Yes, this information is provided by kowached. He also provided this information.
Q) Will putting higher octane gas in the tank make the car go faster?
A) Motor Trend did a study in 2001 and the summary conclusion is that it will not. Only a car designed to take advantage of the higher octane will. Their results were based on dyno tests.
Q) Are there handling stats that I can use to compare against other cars?
A) Here are some misc stats that I have picked up to give you an idea of how these cars perform.
600 ft slalom: range from 63.2 (non-sport) to mph to 67.0 (sport)
Skidpad: .78 g to .85g
Braking: 60-0, 128 ft (non-sport); 121 ft (sport); 70-0 161 ft.
Q) What is curb rash?
A) Curb rash is when you rub your wheels against a curb or something else and it becomes damaged (rough and discolored). Click here for a method of fixing it yourself.
Q) What do the VIN represent?
A) Click here for a link and this is a code guide.
