|
|
|
06-05-2014, 04:06 PM | #67 | |
Second Lieutenant
40
Rep 257
Posts |
Quote:
|
|
Appreciate
0
|
06-05-2014, 06:16 PM | #68 |
Enlisted Member
6
Rep 40
Posts |
Alright so another track day done, so for whatever reason it took quite a while to boil my brake fluid yesterday 15-20min of hard fast lapping instead of the normal 5 laps. Which makes me think this might be a vapour lock issue as it’s the only thing that’s changed since last time out on track.
The ambient temps were around the same 20C as other events. I also realize that I’m one of the few running BFG R1’s which are pretty much a full racing slick which means I’d put more temp into my brakes compared to everyone else that run just a performance street tire on track. I did however experience the HP+ pad fade that I’ve heard so much about but it happened well after my fluid had boiled. I’ll be moving to at DTC 70 sometime in the near future. So assuming that HP+’s start to fade at a consistent temp no matter what car they’re on why is my brake fluid boiling before pad fade while it seems everyone else run into pad fade before they boil they’re brake fluid? I’m considering taken the car to a BMW Dealership as I’ve heard they’re the only ones that are able to activate the stability control valves to force any air that might be trapped in the stability control system. Also since I bought the car used I’m unsure what the past owner may have done to the brake system. I’d really appreciate if another 135i owner would go out to their car pump the brake pedal a few times till its rock hard and then just see if the pedal slowly sinks? I’m unsure if this is normal or if my car has an issue, thanks in advance it should only take you a few minutes and would save me a lot of time pondering. |
Appreciate
0
|
06-05-2014, 07:11 PM | #69 |
Second Lieutenant
40
Rep 257
Posts |
Nate. I tried the brakes for you and it goes firm and stays firm and doesn't sink. If I release it the pedal is nice and firm and feels normal. Hope that helps
|
Appreciate
0
|
06-05-2014, 08:08 PM | #70 | |
Captain
1497
Rep 791
Posts |
Quote:
Your brake fluid can't boil before your pads fade, because when your fluid "boils" (fluid fade) the pedal goes to the floor with no pressure going to the pads and so no friction (or further heat) being generated. What exactly do you mean when you say your fluid is boiling? If you have air in your hydraulics, the pedal will be soft all the time, so that isn't likely your problem. HP+ are barely adequate for lapping with a street tire and completely inadequate for lapping with an R-compound tire. Opinions differ widely on the fluid front, but my experience has led me to using Castrol SRF and nothing else, flushing it once a year. It seems expensive but isn't if you can avoid multiple flushes. In my experience, once a fluid is overheated, it is never right again and should be flushed. It will recover once it cools, but not completely. How much effort do you expend in cooling your brakes after a lapping session. If you come in and park with your pads stinking hot (literally) and just park, you are abusing your fluid. If you really are overheating your fluid every lapping day, you should be flushing it after every lapping day. If your pedal is getting a bit soft or the travel is getting a bit long but not going to the floor, there are other (than fluid fade) possible explanations, including pad knockback and thermal deformation of your shims (if you are using them). Shims may help with thermal isolation but they don't help when it comes to a firm pedal. What track are you at? Is it particularly hard on brakes? When you don't have brakes that can take anything you can throw at them (and you don't) you have to manage them as a limited resource. Examples: - limit the number of hot laps - alternate hard laps with cool-off (minimal braking) laps - brake earlier - brake less - don't make every lapping day an experiment to find out how quickly you can fade your pads/fluid |
|
Appreciate
1
|
06-05-2014, 11:12 PM | #71 | |
Major
165
Rep 1,409
Posts |
Quote:
Fixed that this evening, while I was in there to remove the glazing on my XP10 pads and check the state of my pistons and dust boots. Clunking sound is now gone, thanks to you!
__________________
2011 X3 35i with M pack + 2011 135i w/6SPMT | 255 square tire setup | Quaife 3.46 LSD | Diff lock down bracket | Bilstein B8+Swift SpecR springs+H&R FSB | CDV delete | BMS Oil Tstat bypass | ER FMIC & CP | N54Tuning DP | GC Street Camber Plates | M3 FCA +guide rods+RSFB's+Tranny mounts | Manzo toe arms | Cobb Stg2 agressive tune | Hawk DTC70 brake pads | RB SS brake pistons | Goodridge SS brake lines | Custom brake cooling ducts
|
|
Appreciate
0
|
06-05-2014, 11:14 PM | #72 |
Major
165
Rep 1,409
Posts |
Thanks for this!
__________________
2011 X3 35i with M pack + 2011 135i w/6SPMT | 255 square tire setup | Quaife 3.46 LSD | Diff lock down bracket | Bilstein B8+Swift SpecR springs+H&R FSB | CDV delete | BMS Oil Tstat bypass | ER FMIC & CP | N54Tuning DP | GC Street Camber Plates | M3 FCA +guide rods+RSFB's+Tranny mounts | Manzo toe arms | Cobb Stg2 agressive tune | Hawk DTC70 brake pads | RB SS brake pistons | Goodridge SS brake lines | Custom brake cooling ducts
|
Appreciate
0
|
06-06-2014, 01:02 AM | #73 | |||||||
Enlisted Member
6
Rep 40
Posts |
Quote:
Quote:
Quote:
Quote:
I’m flushing my brake fluid at every track event using Motul RBF 660 which allows me to run significantly longer before running into my brake issues when compared to ATE Super Blue, since moving to a fluid with a much higher boiling point significantly helped my brake issue I assumed it's vapour lock caused by overheating and boiling my brake fluid. Quote:
Quote:
Should i be running the stock steel backing plates along with the titanium shims? As right not i’m only using the titanium shims. Quote:
I’m currently trying to resolve the issue so that I’m able to push harder and enjoy more track time without having to run cool off laps every few laps. |
|||||||
Appreciate
0
|
06-06-2014, 05:36 AM | #74 | |
Captain
1497
Rep 791
Posts |
Quote:
Titanium shims are good for the fluid in that the insulate the caliper a bit, but they are bad for the pad because the pad loses some ability to dissipate heat. Running the stock shim as well is a good idea because it eliminates the rattle because it wraps around the ends of the pad to take up the end clearance. That said, true race pads get hotter and expand more so may need additional clearance. For that reason I use custom made stainless shims that only wrap around the thrust end of the pad. Stock shims should be ok on HP+ though. Some knockback may be a result of the pads rattling about. I would say it is worth trying the stock shims in addition to the titanium ones. Don't use any brake compound between the shims and the pads though. It just makes a mess at the temperatures you are running. I would love to know how pads distort due to thermal stresses. Any temperature differential across the thickness will introduce a bending tendency, which will knock your pistons back. It may actually be worth trying running without the titanium shim to see if it helps in this regard. I assume you are bleeding your brakes the conventional way (pumping the pedal)? Much (maybe all) of the air you see when you bleed may actually be air being drawn in around the bleeder screw threads. Try pulling the bleeder screws out and putting some anti-seize on the threads to act as a sealant. Even better if you are bleeding your brakes often is to use a speed bleeder screw. These have a fairly long lasting sealant on the threads and have a check valve built into them. You don't need to close the bleeder screw between pumps which also means you can do the bleeding by yourself. Another trick is to use a short length of rubber hose (e.g. fuel line) pushed on the end of some clear pvc tubing as a bleeder hose. The rubber hose is more resilient and it seals better on the bleeder screw. If your bleeder bottle is below the caliper, once the line is full the suction created by the siphon effect will draw air into the bleed line if there is any possible air leak around the screw threads. You can also reduce this by keeping the bleeder bottle above caliper height. When you are pumping the brakes to bleed, do it slowly and release the pedal slowly to reduce fluid turbulence and to reduce any suction forces in the fluid. Fluid boiling produces fluid vapour, not air, and when the fluid cools the vapour should condense. The only place air can truly come from is by being drawn in past the piston seals, which is unlikely. Often what people think is air in the system actually comes from the reason noted above. Fluid that has been cooked does become more compressible though, which is presumably due to some kind of chemical decomposition in the fluid. If you are seeing the fluid that you are bleeding being discoloured in some way, it definitely points to some kind of decomposition. For a track bleeding you don't need to flush the whole system. You just need to get the old fluid out of the calipers. Maybe 4 pumps on each of the rear calipers just because, then half a bottle of fluid out of each of the front calipers. Because the fluid in the caliper is replaced by progressive dilution, you need to bleed out several times the volume contained in the caliper to fill it with mostly fresh fluid. I hope this is of some assistance. |
|
Appreciate
1
|
06-08-2014, 08:23 AM | #76 | ||
Lieutenant
170
Rep 403
Posts |
Quote:
The shop I take the car to is very reputable (they even race their own 135i) and I trust their work. The wheel bearings are good, the brakes were bled a few times with Endless RF-650 fluid, etc... They said it's the classic symptom of knockback, but I'm struggling to believe that I could get hints of that at 35-40 mph surburban driving. It should be noted that on test drives, they don't see (or more accurately feel) this issue. These are good & experienced guys. But I swear that minor variability is still there for me. My Land Rover LR3 and VW Passat have more consistent brake feel around town, and I don't recall the variability with the 135i OEM setup. And then you said... Quote:
Thanks. Karl.
__________________
Stock – 997.2 C2S Coupé • Carrara White / Cocoa • Adaptive Sports Seats • PDK w/SC • PSE
Mods – Front 996-GT2 and Rear 997-Turbo Brake Ducts • 3rd (center) Coolant Radiator • 10mm/15mm Spacers Last edited by wjk_glynn; 06-08-2014 at 09:07 AM.. |
||
Appreciate
0
|
06-08-2014, 12:52 PM | #77 |
Enlisted Member
6
Rep 40
Posts |
It’s a pretty easy test to perform, with the car on but stationary repeatedly push the brake pedal if it slowly sinks further and further towards the floor my understanding is it’s the master cylinder. I can’t quite get it to the floor but it’s certainly sinking and not returning to the usual height. I imagine once everything is really hot and in a demanding brake environment it’s much worse, whether that’s on track or in stop and go traffic. Fluid starts leaking around the piston in the master cylinders instead of applying pressure to the calipers.
I’ve yet to replace the master cylinder it’s only $300 from ECS Tuning but I’m unsure if I’ll have BMW install or attempt to do it myself. I’ll call them Monday and see what they’re asking. My car is a 2009 135i with 191 000KM mostly highway. But I have tracked it 15+ events in the last 18 months. I just didn’t think a car that’s this relatively new would have such issues yet. I’ll update the thread once it’s replaced. |
Appreciate
0
|
06-08-2014, 01:16 PM | #78 | |
Captain
1497
Rep 791
Posts |
Quote:
I suspect your diagnosis is wrong. Heat won't make its way to the master cylinder so it has no effect on the master cylinder operation. You should press and hold the brake pedal once, using the maximum brake pressure that you normally need to apply (not using all your weight). If the pedal slowly sinks over say 15 seconds, without increasing the applied brake pressure, you may be right. A sinking pedal is different from a long pedal. A sinking pedal points to internal bypass around the master cylinder seal, or an external leak. A long pedal points to increased clearances (e.g. due to knockback or thermal expansion effects) that must be taken up with fluid volume before the pedal gets hard. I see some variability in my pedal at the track. Ideally there wouldn't be any, but what you are seeing may be "normal" and you may just be gun shy because of your earlier brake problems. The dealer should be able to objectively diagnose the master cylinder, but don't be surprised if they say it is ok. |
|
Appreciate
0
|
06-08-2014, 02:00 PM | #79 |
Enlisted Member
6
Rep 40
Posts |
it's a possibility I may be wrong, hopefully i'll know within the next couple of weeks. The issue is slight but it defiently sinks not long but sinks, it's why pumping the pedal works on track. i'm unsure what BMW will say but at the end of the day i have a few options spend the $300 and install it myself I've done it in the past with ford vehicles with DSC. I'm aware technically you're supposed to bleed the system opening all the control valves but usually isn't necessary with no noticeable air in the system. failing which i could always take the car to BMW and ask them to bleed the system. As of now I'm hoping BMW will recognize the issue and be happy to do the work.
|
Appreciate
0
|
06-08-2014, 02:07 PM | #80 |
Enlisted Member
6
Rep 40
Posts |
also while on track everything in the engine bay is much hotter than on the street but do think having to to brake hard again and again in short succession is causing the issue.
|
Appreciate
0
|
06-12-2014, 05:10 PM | #81 |
Second Lieutenant
40
Rep 257
Posts |
I thought I would give everyone an update on the brakes and my last track day. The Carbotech XP 12s held up fine up front. I felt I was just as hard on the brakes as the previous week. XP 10s in the rear of course no problem. I had no brake fade or boiling fluid problems. Overall a good track day, although I was a bit under the weather the whole day, so I wasn't at my best. Still a fun day, I was a bit slower then the prior week. I attribute that to the way I felt and the number of cars in our run group. There were about double the amount of cars as the previous week. So on almost all the laps I was being passed or passing someone. Plus we had 3 Black Flags that brought everyone in out of the 5 sessions that I did.
|
Appreciate
0
|
06-12-2014, 05:24 PM | #82 | |
Major
165
Rep 1,409
Posts |
Quote:
Thought I would ask, do you drive with DSC OFF (TIMYOYO mode) on the track, and do you think DSC might be using your brakes in addition to your input, therefore overheating more rapidly? Just thought about this today, from feedback from guys at the track. Might have to try turning DSC off next time, once my car and tires are warmed up, to see if my brakes last longer and my lap time is reduced ...
__________________
2011 X3 35i with M pack + 2011 135i w/6SPMT | 255 square tire setup | Quaife 3.46 LSD | Diff lock down bracket | Bilstein B8+Swift SpecR springs+H&R FSB | CDV delete | BMS Oil Tstat bypass | ER FMIC & CP | N54Tuning DP | GC Street Camber Plates | M3 FCA +guide rods+RSFB's+Tranny mounts | Manzo toe arms | Cobb Stg2 agressive tune | Hawk DTC70 brake pads | RB SS brake pistons | Goodridge SS brake lines | Custom brake cooling ducts
|
|
Appreciate
0
|
06-12-2014, 10:50 PM | #83 | |
Second Lieutenant
40
Rep 257
Posts |
Quote:
|
|
Appreciate
0
|
07-11-2014, 08:06 PM | #84 |
Enlisted Member
0
Rep 36
Posts |
How about for the street?
Well, I just had a late reaction to a red light at a decent clip and notice my brakes felt less impressive then they use to be. I'm looking into replacements. I don't track my car and all I know is the OEMs were pretty damn good. Questions...
Do y'all recommend "turning" the rotors at 66k miles or just getting new ones? I don't want slotted or drilled, but I do like the looks of the black painted centers, because mine are all corroded . As for pads, I only ask for them to be at least as good as new, or better but with less dust. The OEMs are good for exactly 2 hours of driving before the wheels are covered. Suggestions? |
Appreciate
0
|
07-26-2014, 02:11 PM | #85 |
Enlisted Member
6
Rep 40
Posts |
finally had some good track time and it was master cylinder failure that caused my braking issues. i replaced the master cylinder by myself and now have a nice firm pedal while on track. the car had 195 000KM on it when the master cylinder started to fail. If anyone has any questions feel free.
|
Appreciate
0
|
05-18-2016, 08:32 AM | #86 | |
Major
429
Rep 957
Posts |
Quote:
Only way to get a consistent feel would be to code this off and then see how they feel. The car also performs its own brake fade compensation. Brake pressure is increased as the car estimates brake temperatures. Code that off too to get a more consistent pedal feel. |
|
Appreciate
0
|
Post Reply |
Bookmarks |
|
|