E9 Brake upgrade possibilities??

[Gary Knox]

Did a search for this question, and didn't get anything helpful.

I just purchased a '74 CS with a 3.5 injected engine and 5 speed overdrive transmission (pix below). Drove it about 350 miles home on Friday, and it drove smoothly and well.

But - I'd forgotten the OE braking capability of these cars (had two E9's during the late '70's), and it seems to me I could certainly use some upgrade to the small calipers/rotors on the car (I'm going to 16" wheels soon). I must admit, the two performance cars I've been driving have awesome brakes (Porsche 928 GTS and MB SL55 AMG), so maybe I'm expecting too much from a 41 year old car. The car has all new rotors and nearly new pads (OE, I believe).

Any experiences or references you can give for upgrading the 'whoa' part of driving I'd certainly appreciate.

Cheers-

 

[m73]

http://e9coupe.com/forum/showthread.php?t=8322

Also check ie. motorsports + bimmerdoc.com

I believe there is a wildwood solution if you choose that route.

MF

 

[JFENG]

What aspect of performance was not good enough for you?

Couldn't lock up all four (eg brakes can't generate enough friction to overcome tire grip)?
Pedal pressure too high to a given level of braking (cold pad friction coef too low)?
Was there too much fade (hot pad friction chef too low)?
F/R balance not optimal (front or rear locks up too early)?
Do you just want shorter stopping distances (tires don't provide enough braking grip)?

If you are on old 195/70-14's the tires could be old, the tires could be "minivan" grade rather than high performance grade. And of course the original size is narrower than any 3000lbs modern car, smaller than what you get on a Prius!

I'd suggest you do you your 16" wheel upgrade, get some UHP summer tires, make sure your front shocks and springs are ok. Then assess braking performance again to see where you are dissatisfied.

 

[kasbatts]

I think its the lack of "boost" effect that gets most people.
If you haven't driven a 40 year old car for some time, its a bit of a shock as to how much effort you need to apply to get the coupe to stop compared to newer cars.

Personally, I think its the 1960/70 boosters that are the biggest culprit when compared to newer technology, the rest of the system (calipers, disks, hoses and master cyl) are fine, this stuff hasn't really changed much over the years.

I'm not sure what the LHD cars are like to stop, but the RHD are not nice.

Dont get me wrong, they do stop, but you gota push hard and there is not really any feedback from the pedal, quite wooden feeling, but you get that with 3 master cyl

This is something I am going to look at improving when I do my engine swap I think, maybe swapping to one remote, more modern booster and master cyl and re plumbing the system to a more conventional set up i.e not all the split circuits between wheels and front and back.

 

[Gary Knox]

I guess the part relating to pedal pressure required to get a reasonably rapid deceleration is the part that I 'may have' forgotten! Yes, the 20 and 30 year newer cars I've been driving have a lot more assist, especially the electronic system in the AMG. The tires on this car are nearly new. I'll be putting the recommended ContiSports on the 16"wheels - have both the wheels and tires in hand.

In the Porsche world, there usually have been a fair number of rotor size/caliper changes that can be used to increase braking power and longevity if you are willing to go to larger wheels. I was just hoping there would be later Beamer 'parts' that might be applicable to the E9. Maybe I'm dreaming!!! Please wake me up if I am - I'll just strengthen the right leg.

 

[HB Chris]

Granatrot? Very nice! Get used to the vintage braking system, not up to panic stops that are often needed these days. Otherwise they are fine. And don't forget, it's bimmer not beamer.

 

[JFENG]

I guess the part relating to pedal pressure required to get a reasonably rapid deceleration is the part that I 'may have' forgotten! Yes, the 20 and 30 year newer cars I've been driving have a lot more assist, especially the electronic system in the AMG. The tires on this car are nearly new. I'll be putting the recommended ContiSports on the 16"wheels - have both the wheels and tires in hand.

In the Porsche world, there usually have been a fair number of rotor size/caliper changes that can be used to increase braking power and longevity if you are willing to go to larger wheels. I was just hoping there would be later Beamer 'parts' that might be applicable to the E9. Maybe I'm dreaming!!! Please wake me up if I am - I'll just strengthen the right leg.

My E9 brakes just fine, but my reference is a car designed in 1949 (xk120), another one designed in 1955 (Giulietta), another in 57 (Lotus). Compared to those cars, the E9 is positively modern. No, it won't stand the car up on it's noise like my DD BMW, but then again the DD not only has modern tires/brakes, DSC (and I think it has dynamic brake biasing) ... it also has a very modern suspension design. I wish all my cars could stop like that. But they don't so I just drive each car in a manner in accordance to it's capabilities. That means, no tailgating, moderated closing/passing speeds on the highway, and much earlier anticipation what the idiots around me are going to do.

IMHO, maybe a BBK is the right way to go. But pick one that doesn't upset the F/R brake bias ... or put in a bias adjuster. Cool accessory that's sure to generate interesting conversation ("what's that red handle next to the parking brake?"). If nothing else, you'll be able to optimize for dry/wet/snow conditions and have some direct control over what your car does under heavy braking into a corner. Might make you faster in an autocross as the E9 understeers a bit and sometimes needs some help rotating.

I'm sure someone mechanically experienced will chime in with some options based on parts from newer BMW's. Maybe E24/E28 parts fit??

John

 

[Arde]

My brakes are great now that Don replaced booster, master cylinder, and front calipers. Only limitation is no ABS, else it brakes better than any new car.

 

[Gary Knox]

Thanks guys, I recognize I may be looking for the holy grail!!

Regarding Bimmer/Beamer - technically, I think it should be Baymer!!!
That relates to the pronunciation 'auf Deutsche' of the letters BMW, which are pronounced Bay Em Vay - at least when I used to call on the company with the four round cylinder towers in Munchen.

Skol, Cheers, etc.

 

[JFENG]

Thanks guys, I recognize I may be looking for the holy grail!!

Regarding Bimmer/Beamer - technically, I think it should be Baymer!!!
That relates to the pronunciation 'auf Deutsche' of the letters BMW, which are pronounced Bay Em Vay - at least when I used to call on the company with the four round cylinder towers in Munchen.

Skol, Cheers, etc.

Suggest you talk to your local E9 experts. They'll have the most knowledge and experience to help you make your car brake like you wish.

The only guy I know of down in your area is Mike Yaskin, Bavarian Specialties over in King of Prussia. Mike has been around for a long time. I've never used him personally, but I've heard he's a good guy.

Call him and spend an hours worth of his labor to have him go over the car. Then discuss your needs with him.

John

 

[Ohmess]

To me, nothing engenders confidence while driving like being able to stop extremely quickly. When I was modifying my e39, I focused intently on parts that would improve my ability to quickly stop a powerful heavy vehicle, and ended up with the following:

M5 calipers, Pagid pads, Turner stainless steel brake lines, BMW European floating rotors, M5 brake ducts, ATE's best brake fluid, H&R sport springs, Bilstein heavy duty shocks, HRE (significantly lighter than stock) wheels and Michelin Super Sports.

I love the confidence that derives from knowing I can stop extremely quickly. Given the flex in the e9 chassis, some accommodation will have to be made, but I'm interested in what others have done to improving the braking performance on our cars.

 

[Stan]

I think Murray Fowler said that the 3.0 stock 4 wheel disc brakes are more than adequate.

 

[rsporsche]

this is worth a discussion with Mario Langsten. last time i discussed this issue with him, he recommended replacing all bushings in the suspension and subframes with new urethane bushings and tightening everything up. as i remember, he thought that with this and replacing old brake hoses with stainless, rebuilt calipers, etc ... that the stock brakes were sufficient.

 

[JFENG]

I think Murray Fowler said that the 3.0 stock 4 wheel disc brakes are more than adequate.

What I think Murray meant was, if you can lock up all 4 tires (with proper braking technique) then your brakes are more than adequate and you're limitation is tire grip. If you are running stock size tires and you can't lock all of them up then your brakes need fixing. If some tires lock up before others, then something's broken or not adjusted correctly.

Stan, IMHO many people don't test their brakes the right way. You don't test this by going out and just stomping on the brakes at 80mph. Too abrupt an application will break the fronts loose prematurely, e.g. before weight transfer gives the front tires their max grip. Roll into the brakes like over 1/3 sec so your street suspension has time to compress, then see if any corner locks up. If none lock up, more powerful brakes could help you stop faster.

Assuming you can lock up all four when braking correctly, the weak point is the tires. Get the widest, lowest profile, stickiest tires you can fit under the fenders (roll the lips, add negative camber). Lots of choices in a 225/50-16, less so in a 205/55-16. So see if your shop can play with spacers and camber to get the 225 to fit up front (or even a 235 on a 17" wheel from an E39?). Nothing wrong with running DOT street legal race tires on the street. It's not like anyone's driving 10kmiles a year in their E9, right? A set of R888's would do the trick, or Yoko AD08's if you drive in the wet. I like the Conti DW's on my DD because they last a little longer than the really sticky stuff.

What I'm hearing is that the OP wants more friction for a given amount of pedal pressure. Not necessarily more deceleration capability.

 

[kasbatts]

To be fair, the stock e9 system isn't too bad considering the age of the car.

We have 4 pot calipers with vented rotors up front, and disks on the rear (solid or vented, doesn't really matter as the back only does a small part of the required braking, the front is the business end)
While the rotors and pad area are't as big as more modern cars we have to remember the coupe is quite light in comparison with more modern cars, so it pretty much all evens out for these cars in everyday street use; used on a track or competitive environment would be a different story where bigger is pretty much best.

Again I go back to my original comment that I feel the biggest culprit is the 1960's design boosters, these just don't give the feel that the newer boosters give and as such make the whole system a little "wooden" feeling.
The modern boosters are a very different beast on the inside compared to what we have.

Dont get me wrong, E9 with a standard brake system, good tyres and suspension in top condition will stop very well; you will just need to push harder, and it just wont feel like a modern car doing it!

You either have to live with it and remember the car is 40 years old, or change it all to something a bit more in line with modern technology.

 

[Stan]

on the way to the Vintage, some clown cut in front of me and the standard coupe brakes worked very well. A poof of white smoke from all four corners and a squeal of rubber left more of my Michelins on the pavement than I wore off in the preceding year!

Tire adhesion not brakes were the limiting factor on how quickly the car came to a stop

 

[Ohmess]

What I think Murray meant was, if you can lock up all 4 tires (with proper braking technique) then your brakes are more than adequate and you're limitation is tire grip. If you are running stock size tires and you can't lock all of them up then your brakes need fixing. If some tires lock up before others, then something's broken or not adjusted correctly.

Stan, IMHO many people don't test their brakes the right way. You don't test this by going out and just stomping on the brakes at 80mph. Too abrupt an application will break the fronts loose prematurely, e.g. before weight transfer gives the front tires their max grip. Roll into the brakes like over 1/3 sec so your street suspension has time to compress, then see if any corner locks up. If none lock up, more powerful brakes could help you stop faster.

Assuming you can lock up all four when braking correctly, the weak point is the tires. Get the widest, lowest profile, stickiest tires you can fit under the fenders (roll the lips, add negative camber). Lots of choices in a 225/50-16, less so in a 205/55-16. So see if your shop can play with spacers and camber to get the 225 to fit up front (or even a 235 on a 17" wheel from an E39?). Nothing wrong with running DOT street legal race tires on the street. It's not like anyone's driving 10kmiles a year in their E9, right? A set of R888's would do the trick, or Yoko AD08's if you drive in the wet. I like the Conti DW's on my DD because they last a little longer than the really sticky stuff.

What I'm hearing is that the OP wants more friction for a given amount of pedal pressure. Not necessarily more deceleration capability.

Excellent post. A lighter wheel/tire combination also improves braking because a mass with a lower moment of intertia will slow more rapidly in response to braking forces.

 

[JFENG]

Excellent post. A lighter wheel/tire combination also improves braking because a mass with a lower moment of intertia will slow more rapidly in response to braking forces.

Right, BBS RS are better in this regard than the pretty 16" Alpinas. The Style 5's from e39's are also very light, and relatively cheap. Semi race tires better than tires optimized for 60kmile tread life

 

[TodB]

One of the things that some of use are guilty of is trying to modify our coupes such that they maintain the timeless styling that we like but have the performance of a modern car.

You can only get so much out of a M30 motor (ask me how I know) though turbocharging certainly can bridge the gap. Handlingwise, you are starting out handicapped with the coupe platform so get used to the fact a Camry can probably out handle you. Same goes for brakes. Coupe brakes are actually pretty good if they are in good condition. Some improvements can be had with better lines, fluid and pads but I think the observation about the booster is dead on - 1960s booster technology is not what it is now especially with regard to required pedal effort or feel. You are going to have to apply a lot more pressure on the middle pedal than you are used to. Just be careful getting back into your daily driver and not face planting the windshield during your first stop!

 

[Gary Knox]

All your comments have been wonderful, and I'm sure 'spot on'.

I DO agree with Ohmess, however. Great confidence in the braking power of the car you are driving is wonderful to have. After retiring, I started using the Porsche Club of America 'Drivers Education' program to improve my skills and generate adrenaline. This consists of a carefully managed progression in driving on most of the road race tracks throughout the US and Canada from novice to instructor through about 6 stages (BMWCCA has a similar program).

I was driving a Porsche 928 S4, which has phenomenal brakes for the weight of the car (~3700 lbs). Essentially all of the instructors I had through my progression as well as the guest instructors I asked to ride with me were always MOST impressed with the braking capability of the car. This DE program concentrates on using the brake and accelerator as rheostats. I guess I'll just have to start regarding the middle pedal as a rheostat that needs a lot of turning if you want to slow down quickly!!

THANKS again for all the input, and I will appreciate any further comments as well.

Cheers,