Baikal Bimmer
Well-Known Member
How hard would you have press to lockup with stock vs wilwoods?
Brake Upgrades
- Thread starter Baikal Bimmer
- Start date
Bearmw
Well-Known Member
Since many brake issues relate to excess heat buildup the simplest remedies involve ducting cool air to the rotors followed by more massive and often heavier rotors. Do you have functional brake ducts?
It’s about overheating the pad compound and the boiling the fluid.
Track use is totally different that street driving. Try threshold braking from 100mph to 60 three times a minute, and do this for 20 minutes straight.
That is a lot of heat to dissipate. If you look at pad friction be temp, once you pass the max working temp the friction coefficient falls off. So, it’s not if the stock brakes are good enough after 10 back to back stops, but after 40 or 50 back to back applications.
John
My personal issue with brake ducting is it’s not friendly for street use, IMHO. I had them on one of my old cars, and they funneled all sorts of crap into the rotors ... water and bbeing the biggest concern.
But yes you are right that this can greatly reduce the issue.
Does anyone make a E9 brake backing plate for cooling ducts? Think of an old fashioned metal coffee can with a slot in the side. That slot fits over the brake rotor, and one end of the can connects to the brake duct/hose
But yes you are right that this can greatly reduce the issue.
Does anyone make a E9 brake backing plate for cooling ducts? Think of an old fashioned metal coffee can with a slot in the side. That slot fits over the brake rotor, and one end of the can connects to the brake duct/hose
Baikal Bimmer
Well-Known Member
Yes our front spoiler does have air ducts. So do we agree that for more race/track related applications the stock brakes are inadequate? I was under the impression that their adequacy was in terms of ‘in 1972 they were adequate’ not 2020
I did a a few CCA track days back when our cars were relatively newish. The stock brakes did fade, so I switched to a Ferodo Metallic pad, and it helped a lot. But then my brakes were terrible in the cold, almost non-existent below 30F and squealed.
So. I’d say 40 years ago the E9 brakes were inadequate for track days.
Today, both tires and brake pads have improved a lot, but I don’t know if one has outpaced the other.
How fast and aggressive are you on track, and which tracks. Are you planning to drive?
John.
Baikal Bimmer
Well-Known Member
We would definitely put the car though it’s paces. For tracks it would probably be Laguna Seca and then willow springs. Also plan on doing auto cross.
As far as the stock system goes, the master cylinder and booster have been rebuilt, all the lines changes, and the rubber changed to stainless. I was just wondering if before I put money into old brakes (get rebuilt) if I should just upgrade to wilwood.
For autocross I’ll guess stock brakes are ok, but I don’t know the type of courses CCA lays out in CA.
For tracks, you might first try a high temp street pad compound as a way to judge the size of the performance gap which needs to be addressed.
If you only have minor fading, some simple ducts with stock backing plates might be all you need.
If you do upgrade just the front, you can calculate the brake bias change relative to the stock system as long as you have a little data on the pads and calipers. This and a day some brake testing (with warmed up tires), will give you a quick idea of whether or not you need to replace the existing rear brake proportioning valve with an adjustable.
The other advantage of installing an adjuster is the ability to compensate for a wet or cold track (tolerates higher rear bias, eg less front bias). But I’d you are at an event where the track conditions are changing while you drive, you’ll want the bias control inside the cockpit and at hand.
I was at an event recently where this was fairly important. One guy forgot to take out rear bias as the track started to dry and ended up spinning when the rear broke away sooner than he expected. Fortunately, it was just a light kiss on the barrier, but unfortunately it went down the entire side of the car :-o
For tracks, you might first try a high temp street pad compound as a way to judge the size of the performance gap which needs to be addressed.
If you only have minor fading, some simple ducts with stock backing plates might be all you need.
If you do upgrade just the front, you can calculate the brake bias change relative to the stock system as long as you have a little data on the pads and calipers. This and a day some brake testing (with warmed up tires), will give you a quick idea of whether or not you need to replace the existing rear brake proportioning valve with an adjustable.
The other advantage of installing an adjuster is the ability to compensate for a wet or cold track (tolerates higher rear bias, eg less front bias). But I’d you are at an event where the track conditions are changing while you drive, you’ll want the bias control inside the cockpit and at hand.
I was at an event recently where this was fairly important. One guy forgot to take out rear bias as the track started to dry and ended up spinning when the rear broke away sooner than he expected. Fortunately, it was just a light kiss on the barrier, but unfortunately it went down the entire side of the car :-o
Baikal Bimmer
Well-Known Member
Hope the car is back at !
Baikal Bimmer
Well-Known Member
What abou the ap calipers on wilwood discs, is that better again?
The AP calipers become a wheel problem
Call me tomorrow if you want insight.
daddywad
Well-Known Member
My Wilwood setup works fine, as its a RHD car I needed to modify the plumbing as the Wilwood front
calipers only have one inlet not two like the CSL
Baikal Bimmer
Well-Known Member
Do they act like a wheel spacer, as in does their fitment push the wheel towards the wheel arches, or is there no change?
Baikal Bimmer
Well-Known Member
Wilwood says it requires 16 inch wheels, we have 17s on our car. Theoretically it follows that we can fit something larger than the 300mm wilwoods. What about e24 big brake kits? Would those work?
you'll have dual circuit brakes with the single-line MC. I would think you can just cap off one line from the MC.
Baikal Bimmer
Well-Known Member
I have heard that some e24s had 280mm rotors as opposed to 272 on e9’s, would this increase result in any tangible or useful increase in stopping ability?
I think you should finish the build w stock brakes the track it to find out what you need. Then, once you have some track time you can make some targeted improvements. You may find you don’t really need 6-pot AP forged alloy brake calipers and carbon ceramic discs.
In vintage racing you just learn to deal with whatever brake performance you have. In my case I have sucky brakes so I brake earlier, and resign myself to slowing less than I’d prefer before each corner.
I enjoy the challenge of adapting to the car’s limits, and not the other way around.
John
In vintage racing you just learn to deal with whatever brake performance you have. In my case I have sucky brakes so I brake earlier, and resign myself to slowing less than I’d prefer before each corner.
I enjoy the challenge of adapting to the car’s limits, and not the other way around.
John
I would suggest that the tires (size/compound) could be much more of the limiting factor than the brakes as to how hard and how soon you can brake on the track. It also depends on how often and how serious you want to be on the track. Pads are easy to swap on track days as a first step if you feel a need for an upgrade. I've tracked a stock E39 528i at Thunder Hill with stock brakes and street pads and had plenty of fun (for me).