My BMW 335i

[PranK]

Curious if any of you know why my brakes might have been pulsing after a few hot(ish) laps ?

[Kinkstaah]

I'd just guess at the usual suspects really. There's not that much to a braking system movement wise and everything has to be right or you get shudder or what feels like warping. In my case we were talking the wheel moving 100mm in every direction 5 times a second (it was ROUGH), like driving over train tracks continuously or something.

I used to get gnarly shudder when pads got warm, and it turns out the actual pad was the wrong (yet also compatible?) size. This probably isn't your issue, and another issue should feel something through the pedal, - fade if the pads are way too hot, or a spongy pedal if your fluid has got way too hot etc.

Also because BMW it could be weird BMW abs shit

[GTSBoy]

If the pads are just street pads (ie, stocko BMW offering) then the shuddering is most likely to just be uneven pad material (ie binder) deposition onto the rotor.

If it does it next time you're out, use some 240-300 grit paper on both faces of the rotors. Just fold it over, hand hold it and spin the rotor by the wheel studs. Then go back out and see if it feels different (ie better) than it did immediately before.

And then upgrade pads to something tougher perhaps.

Also to reconsider how you treat the brakes on your warmup, while lapping and on your cool down. I'm not sure of the best advice here, but maybe something about what you are doing is the cause. Going too hard without a decent warmup? Leaving the foot on the brake when stationary while they are hot (ie after you spin off!!! :D), or not using the brakes at all during the cool down, or only at the very end of the cool down. Or any of the combinations, variations and other imaginable sins that are possible.

Maybe you need some cheapo brake ducting added for the track to keep temperatures under control. If you can get some temperature paint or crayons, you could check to see how hot the brakes are actually getting and if that looks acceptable or scary.

[joshuaho96]

On 9/1/2024 at 5:34 PM, PranK said:

Curious if any of you know why my brakes might have been pulsing after a few hot(ish) laps ?

Unless it's a proper track pad you're probably getting uneven pad deposits.

[PranK]

Thanks guys.

I'm using EBC Red Stuff, never tried them before. They're not a "track pad" as such just a more extreme street pad. I had Bendix Ultimate's on the 330i and never had any fade or rough braking, despite the reputation.

First few laps were always a little soft, so I wasn't hitting them hard immediately, but the problem did get worse with use, so I'm assuming (same as you guys) that it's heat triggered. The rotors are almost new DBA slotted (same as the 330). 

Would I see deposits on the rotors from the pads? 

I'll be irritated if it was the pads, I ummed and ahhed for ages before picking the Red Stuff and they weren't cheap. 

The car has brake ducts already as standard from next to the fog lights. It doesn't direct directly, close range at the rotor but more generally in its direction. 

I hate when stuff feels off at the track and you know you can realistically only test it again next time you go!

At least this time I had no boost issues like last time, repaired turbo's seems to have sorted that.

[joshuaho96]

8 minutes ago, PranK said:

Thanks guys.

I'm using EBC Red Stuff, never tried them before. They're not a "track pad" as such just a more extreme street pad. I had Bendix Ultimate's on the 330i and never had any fade or rough braking, despite the reputation.

First few laps were always a little soft, so I wasn't hitting them hard immediately, but the problem did get worse with use, so I'm assuming (same as you guys) that it's heat triggered. The rotors are almost new DBA slotted (same as the 330). 

Would I see deposits on the rotors from the pads? 

I'll be irritated if it was the pads, I ummed and ahhed for ages before picking the Red Stuff and they weren't cheap. 

The car has brake ducts already as standard from next to the fog lights. It doesn't direct directly, close range at the rotor but more generally in its direction. 

I hate when stuff feels off at the track and you know you can realistically only test it again next time you go!

At least this time I had no boost issues like last time, repaired turbo's seems to have sorted that.

EBC red stuff is only rated up to 500C. IMO a hybrid track/street pad is something like the Project Mu HC+ which is up to 800C. PFC 11 is rated up to something like 1100C and sure acts like it. Absolutely awful for street use but if you want to find the limits of stock brakes those are probably the pads to do it with.

[GTSBoy]

Yeah....I was convinced many years ago, by others that had a lot of varied use of them, that EBC Red/Yellow/Rainbow all have their problems. So I've never run them, so I can't speak of my own experience. But I would clearly try almost anything else before I could be convinced to try EBC!

28 minutes ago, PranK said:

Would I see deposits on the rotors from the pads? 

Nah. It's too thin to be visible or even really feelable. You might feel it grabbing a bit with the sandpaper at first, and ideally it will start to grab less as it comes off after a few spins. But I wouldn't even count on that.

Bendix Ultimates should never be slagged on. They are actually a really good pad. They work well on the street and they hold up to some abuse. Obviously they are not a track pad for hammering on, but your own experience shows that they aren't terrible. I used them for years and only changed to Intimas (in steps) because I was working on a bias problem and wanted more pad at the front.

You might consider a budget friendly track pad like the Intimas. I have the SRs on my car, which is 100% street. The car, not the pad. The pad is the Street-Race (hence the SR). The street ones are SS. They have somewhat recently released the RR, which is an 800°C pad, needing to get up to 300°C to work best, although not terrible even when cold. Peak mu is at 500°C, which is where you might be killing the EBCs.

The SRs are a 600°C pad. Might be good enough.

I must say though that I have slotted rotors with the SRs, and I have a pulsey pedal at the moment. I am thinking that it's my fault for sitting with foot on brake sometimes after a stop. It is driven 100% in traffic, after all. The point I ma making is that slotted rotors are supposed to help clean the pads....but they really can't do much to help clean themselves! If you can deposit muck onto a smooth rotor, I'm pretty sure you can do it on a slotted one.

[PranK]

1 hour ago, joshuaho96 said:

EBC red stuff is only rated up to 500C. IMO a hybrid track/street pad is something like the Project Mu HC+ which is up to 800C. PFC 11 is rated up to something like 1100C and sure acts like it. Absolutely awful for street use but if you want to find the limits of stock brakes those are probably the pads to do it with.

Yeah ok. I think given the experience I had with the non-track Ultimates I was kinda hoping the non-track Red Stuff would be as good. I'll definitely change the pads before my next day out. Thanks for the info.

1 hour ago, GTSBoy said:

Yeah....I was convinced many years ago, by others that had a lot of varied use of them, that EBC Red/Yellow/Rainbow all have their problems. So I've never run them, so I can't speak of my own experience. But I would clearly try almost anything else before I could be convinced to try EBC!

Nah. It's too thin to be visible or even really feelable. You might feel it grabbing a bit with the sandpaper at first, and ideally it will start to grab less as it comes off after a few spins. But I wouldn't even count on that.

Ok cool, so a few months of daily'ing should clean the rotors off sufficiently for the next day out?

1 hour ago, GTSBoy said:

Bendix Ultimates should never be slagged on. They are actually a really good pad. They work well on the street and they hold up to some abuse. Obviously they are not a track pad for hammering on, but your own experience shows that they aren't terrible. I used them for years and only changed to Intimas (in steps) because I was working on a bias problem and wanted more pad at the front.

I was stunned at the braking I had in the 330. It wasn't as fast as the 335 but I was able to really push it and brake late. Never had a problem. Not a light car but as I said, not a heap of power either.

1 hour ago, GTSBoy said:

You might consider a budget friendly track pad like the Intimas. I have the SRs on my car, which is 100% street. The car, not the pad. The pad is the Street-Race (hence the SR). The street ones are SS. They have somewhat recently released the RR, which is an 800°C pad, needing to get up to 300°C to work best, although not terrible even when cold. Peak mu is at 500°C, which is where you might be killing the EBCs.

Yeah, this aligns with Joshua's comments above. 

1 hour ago, GTSBoy said:

The SRs are a 600°C pad. Might be good enough.

I must say though that I have slotted rotors with the SRs, and I have a pulsey pedal at the moment. I am thinking that it's my fault for sitting with foot on brake sometimes after a stop. It is driven 100% in traffic, after all. The point I ma making is that slotted rotors are supposed to help clean the pads....but they really can't do much to help clean themselves! If you can deposit muck onto a smooth rotor, I'm pretty sure you can do it on a slotted one.

I gotta sit on the brake when stopped. I guess I could hand brake it at lights etc.

Ok, so I'll look at Intima's and Project Mu. The Red Stuff were pretty expensive from memory, bummer. I had considered track and street pad swapping but I'm not too keen on this if the rotor's start getting a little lip, or specific wearing. 🤷‍♂️

Love your work as always. Thanks for the help.

[PranK]

Well, that was quick. Intima only available for the big boy M cars.

[Kinkstaah]

You can always use the Red's for street use, to get them consumed.

Mate of mine loves Red Stuffs, claims he has no fade, but has only done a few track days in his BMW.

Oh, his BMW is a 1000kg E21 with about 200kw. :p

For Skylines, I've always thought that the MINIMUM for track adventuring was orange, or significantly higher. But I am a noob and brake way too hard and have melted nearly every pad in like 1-2 laps.

You may need a more abrasive track pad to wear down brake pad deposits, so if you do get track pads, run them on the street for a little bit of time to clean up your rotors, then put your road pads on and bed them in. Sounds silly, but does work.

[PranK]

13 hours ago, Kinkstaah said:

You can always use the Red's for street use, to get them consumed.

Mate of mine loves Red Stuffs, claims he has no fade, but has only done a few track days in his BMW.

Oh, his BMW is a 1000kg E21 with about 200kw. 😛

For Skylines, I've always thought that the MINIMUM for track adventuring was orange, or significantly higher. But I am a noob and brake way too hard and have melted nearly every pad in like 1-2 laps.

You may need a more abrasive track pad to wear down brake pad deposits, so if you do get track pads, run them on the street for a little bit of time to clean up your rotors, then put your road pads on and bed them in. Sounds silly, but does work.

I'm a little irritated because I could have just gotten the Blue which is their new pad for street & track use. 

Damn, that E21 would be a hoot! 

I'm not sure I'll get back to the track for a few months so I'll leave these on and clean my rotors with them 🤣

[PranK]

So I got a reply from the oil pressure sensor guys.

Quote

Hey there, that depends on oil temp and rpm. Attached are our default warning and critical thresholds. Typical rule of thumb is 10 psi per 1000 rpm.

So at 150C oil temp and 4500RPM, the warning is 47.9 and the critical is 42.1.

The warning is not much above the critical which concerns me. When viewing the data dump from the log I can't see it going below 50psi when on the track but stupid me didn't log RPM's so its not totally useful.

[joshuaho96]

52 minutes ago, PranK said:

So I got a reply from the oil pressure sensor guys.

So at 150C oil temp and 4500RPM, the warning is 47.9 and the critical is 42.1.

The warning is not much above the critical which concerns me. When viewing the data dump from the log I can't see it going below 50psi when on the track but stupid me didn't log RPM's so its not totally useful.

That's the general rule, but you probably don't want to see any dips at all in oil pressure all things considered.

[PranK]

1 hour ago, joshuaho96 said:

That's the general rule, but you probably don't want to see any dips at all in oil pressure all things considered.

Yep, 100%! Even if for nothing else, just for my own personal anxiety. 😬

[PranK]

So I got some fresh Kuhmo 275's on the back to replace the crap that came on this set of wheels and put them on with the front street'ers too. But man I was getting crazy rubbage on the rear passenger side which is odd as the previous crap was 275 also and was on there before I added my extra camber. The semi's are also a *fat* 265 and had no rubbing.

I noticed that the camber left and right was pretty different. Very little on the passenger side. My magnetic camber tester on uneven ground showed roughly -1.75 on drivers side and less than -.5 on the passenger side.

 

It would have been like this on the track day. :(

I adjusted the passenger arms to be as close to the drivers as I could get by eye. I then used my new fender roller to make some extra space but holy crap the folds on the guards are made from battleship steel! I couldn't get much rolled at all, they were so strong.

My alignment is now off with a 30 degree turn in my steering wheel. I'll find a new alignment joint I think. Not only did the last place think my speed sensor cable zip tied to the camber arm was a brake line, they didn't zip tie them back after they aligned it which was pretty poor. Happy I noticed and did it before the track. Looks like they couldn't match left and right either.

 

Gave the old girl a bath and I'm always so happy with how she polishes up. 

[Kinkstaah]

Just keep in mind (maybe too late now) that before you go crazy, most driveways aren't flat. This _can_ affect your dynamic camber and heights too.

It is kinda funny but getting people to really align stuff right can be problematic for people with OCD. Consider a motorsport place if there's any around, and also consider you may have 'dynamically' altered your own camber after a visit to the track, which can happen too.

 

 

[GTSBoy]

I use the flattest and most level piece of concrete I have. And then I shim the tyres on the low side of that with sheets of plywood to level the car. The right amount is easily found with a 2m straight edge and a level or digital angle finder. I use both the spirit level and the same digital angle finder I use to measure the camber. Gives a zero check on the angle finder right at the start.

[PranK]

Thanks guys, I wasn't trying to dial in any kind of accurate alignment, I was just trying to stop my guard from shaving my tyre.

1 hour ago, Kinkstaah said:

It is kinda funny but getting people to really align stuff right can be problematic for people with OCD. Consider a motorsport place if there's any around, and also consider you may have 'dynamically' altered your own camber after a visit to the track, which can happen too.

Can't tell you how often I visually compare each side of my car. Few motorsport joints in Brookvale, I'll head down there.

[Kinkstaah]

I speak from experience, because my driveway is DEFINITELY not flat, and all 4 corners of the car sit completely independently from one another. It's bad enough it makes me guess everything, fender flares being the most common example, every single tyre sits different in the guard.

I've learned to just go OH WELL and pretend not to see it and assuming it's fine. That said, unless you see your car on the alignment machine to soothe your brain you may forever also suffer this pain lol

[The Bogan]

36 minutes ago, PranK said:

Thanks guys, I wasn't trying to dial in any kind of accurate alignment, I was just trying to stop my guard from shaving my tyre.

Can't tell you how often I visually compare each side of my car. Few motorsport joints in Brookvale, I'll head down there.

Should I bring up corner weighing your car where wheel gap means nothing

I borrowed some scales from work one day to try and play with it, I even loaded up the drivers seat with 80kg, IIRC no fender gap was the same after trying to balance the weight over the front and rear

In the end my head hurt and I just used a tape measure to even up my once "corner weighted" car 🤪