Brakes - upgrading question
Discussion
I have a question for people a little more mechanically minded than myself. I've done a few track days now (about 8), all in road cars (172, Z4, currently m135i) and really love it. However I notice after a 20-25min session on track the brake pedal takes more and more movement before the brakes engage, am I right in thinking this is the fluid getting very hot and expanding the rubber brake hoses?
It gets a bit disconcerting when on track and I end up going slower throughout the day and being more gentle on the brakes. Also it takes a fair while to return to normal when leaving the track (30-60mins).
If this is the problem, I'm concerned that changing to braided lines would then lead to the pads/disks fading as they'd be taking more strain. I'm keen to avoid chasing one upgrade after the next and if this is the case I'll probably just leave it as it is and just to the half day track days in future.
Any advice/thoughts welcomed
It gets a bit disconcerting when on track and I end up going slower throughout the day and being more gentle on the brakes. Also it takes a fair while to return to normal when leaving the track (30-60mins).
If this is the problem, I'm concerned that changing to braided lines would then lead to the pads/disks fading as they'd be taking more strain. I'm keen to avoid chasing one upgrade after the next and if this is the case I'll probably just leave it as it is and just to the half day track days in future.
Any advice/thoughts welcomed
The way I see it is you have three options.
The easiest would be to do less laps at a time.
Another alternative would be to upgrade your brake fluid to something like Motul RBF 600 and try that.
I've tracked a wide variety of cars with just the brake fluid upgraded and so long as you don't do endurance sessions, its usually fine.
The final option would be to go out with an instructor to see if you are over braking.
The easiest would be to do less laps at a time.
Another alternative would be to upgrade your brake fluid to something like Motul RBF 600 and try that.
I've tracked a wide variety of cars with just the brake fluid upgraded and so long as you don't do endurance sessions, its usually fine.
The final option would be to go out with an instructor to see if you are over braking.
So it's likely to be the actual fluid (oem stuff atm) rather than the lines expanding then?
With the track time I usually end up doing less and less time per stint throughout the day as the brakes overheat faster. I have had a couple of tuition sessions and I got the impression I could be braking later/going faster but as it's my daily as well I'd say I was only at 9 tenths most of the time..
With the track time I usually end up doing less and less time per stint throughout the day as the brakes overheat faster. I have had a couple of tuition sessions and I got the impression I could be braking later/going faster but as it's my daily as well I'd say I was only at 9 tenths most of the time..
Yes, your fluid is boiling but its the air in the bubbles that's compressing, not your flexible hoses expanding. You could replace the hoses - a set of Goodrich braided hoses aren't very expensive - but TBH you're far better off improving the cooling and the fluid before doing that. Check underneath to see if you've lost any ducts that are supposed to be there and if the car doesn't have any, considering adding some. Swap the fluid for decent race fluid like Performance Friction, AP Racing, ATE Super Blue, or if you're loaded Castrol SRF.
Chris.
Chris.
Ah ok thanks for pointing that out - saved me a few quid on the hoses I'll get the fluid swapped before I next go out then and see how that affects it
RE: cooling, the car is totally standard (and only a few months old) - this may be a daft question but do you mean cooling around the wheels, or under the bonnet where the fluid reservoir is, or both?
I'll get the fluid swapped before I next go out then and see how that affects it RE: cooling, the car is totally standard (and only a few months old) - this may be a daft question but do you mean cooling around the wheels, or under the bonnet where the fluid reservoir is, or both?
Phateuk said:
RE: cooling, the car is totally standard (and only a few months old) - this may be a daft question but do you mean cooling around the wheels, or under the bonnet where the fluid reservoir is, or both?
I think the suggestion refers to brake cooling and whether or not the car has any oe fitting cooling ducts and if not, the possibility of fitting some aftermarket ones. Exactly - your car was not designed for all this extra heavy braking you're doing on track. You're basically putting more and more heat into the discs and pads and there's no way to remove it before you're into the next corner where you're adding a load more. Eventually you'll wreck the seals in the callipers too, so its important to improving the cooling if you can. Both discs and pads get hot so you need a way to deflect cool air onto both.
Having been there & done that, I would say all of the above.
I have an e36 328 & have done lots of brake upgrades to mine including bigger discs & AP 4/2 pot calipers fitted.
You NEED racing brake fluid (I use ATE super blue & change it every year) braided hoses, and also additional cooling to the general disc/caliper area & regularly do 40+ minute sessions at Cadweel amongst other with no evidence of fade/overheating.
I have an e36 328 & have done lots of brake upgrades to mine including bigger discs & AP 4/2 pot calipers fitted.
You NEED racing brake fluid (I use ATE super blue & change it every year) braided hoses, and also additional cooling to the general disc/caliper area & regularly do 40+ minute sessions at Cadweel amongst other with no evidence of fade/overheating.
I'm fairly happy to do 20 min sessions if it can last doing that on/off for a day. I appreciate that when you have a separate car it's easier to do lots of track focused upgrades. I think after this car I may try having a cheaper daily and a track only car again that I can upgrade as required.
I'll definitely swap out the fluid for some racing stuff before next time and report back how that goes. Really appreciate the advice/knowledge guys
I'll definitely swap out the fluid for some racing stuff before next time and report back how that goes. Really appreciate the advice/knowledge guys
It's a heavy (and powerful) car - going to put a lot of heat into the brakes. High boiling point fluid should help a bit.
After that, cooling - which in my experience makes a lot of difference. Any cooling should be aimed into the centre of the discs as a first try. Once you've done that then the options start getting expensive
Only other thing - short & hard braking should give you more time to cool brakes on a lap than longer more progressive braking.
After that, cooling - which in my experience makes a lot of difference. Any cooling should be aimed into the centre of the discs as a first try. Once you've done that then the options start getting expensive
Only other thing - short & hard braking should give you more time to cool brakes on a lap than longer more progressive braking.
I'm surprised people are mentioning ducting before a change of brake pad to something that is designed for track work.This would be my suggestion...
I'm not sure whats available for the m135i but I'd suggest looking at the more expensive end of the Pagid, Performance Friction or Carbone Lorraine range that can cope with high temperatures. In my experience these kind of pads are just as good on the daily run and make all the difference in making sure you can still brake at the end of the straight.
Oh and do the fluid first. That's definitely step 1.
I'm not sure whats available for the m135i but I'd suggest looking at the more expensive end of the Pagid, Performance Friction or Carbone Lorraine range that can cope with high temperatures. In my experience these kind of pads are just as good on the daily run and make all the difference in making sure you can still brake at the end of the straight.
Oh and do the fluid first. That's definitely step 1.
Am I right in thinking "fade" is when the brakes engage as normal but the pads/disk are so hot they no longer provide the usual amount of friction and effectively not much happens in terms of slowing down? The solution to this would be more track focused pads?
I've never reached this stage with any of my cars as I've always had to leave the track for a cooling off due to the brake pedal going very long as mentioned in the OP.
I've never reached this stage with any of my cars as I've always had to leave the track for a cooling off due to the brake pedal going very long as mentioned in the OP.
Phateuk said:
Am I right in thinking "fade" is when the brakes engage as normal but the pads/disk are so hot they no longer provide the usual amount of friction and effectively not much happens in terms of slowing down? The solution to this would be more track focused pads?
I've never reached this stage with any of my cars as I've always had to leave the track for a cooling off due to the brake pedal going very long as mentioned in the OP.
Absolutely. Given that you mentioned in your first post that a 'soft' pedal was the issue and not brake fade, most recommendations have centered around cooling and reducing fluid temperature, and not problems relating to fade.I've never reached this stage with any of my cars as I've always had to leave the track for a cooling off due to the brake pedal going very long as mentioned in the OP.
One thing is for sure, 20-25 minute sessions are too long for a factory tin top. I bet you'd be better off taking shorter, more focussed sessions and spending your cost savings on some tuition. Pretty much everybody brakes too early and ends up braking using low effort for a long time rather than braking late using maximum effort as you should.
BritishRacinGrin said:
One thing is for sure, 20-25 minute sessions are too long for a factory tin top. I bet you'd be better off taking shorter, more focussed sessions and spending your cost savings on some tuition. Pretty much everybody brakes too early and ends up braking using low effort for a long time rather than braking late using maximum effort as you should.
I'll go for 15min at a time next time then see how that goes. As for breaking I did used to do that before getting tuition, it goes against my mechanical sympathy mind but I now try to brake hard for a short period rather than like you say softer for longer like you would on road noemal . driving
Cooling
And I'm not suggesting green stuff pads here but properly good quality pads that wont leave you much change from £500 a set.
spyderman8 said:
Quite simply because better brakes will make the heat problems even worse.
But the better pads and fluid will be able to cope with the heat that can be generated by a road car even in the middle of summer on long stints, which makes the ducting pointless.And I'm not suggesting green stuff pads here but properly good quality pads that wont leave you much change from £500 a set.
edh said:
Ducting is a damn site cheaper than pads so well worth doing first. Even with track pads I'd be inclined to stick some cooling in. Pads are "sexier" though. Surprised no one has said "buy some AP's"
I'm surprised anybody is suggesting things other than race fluid to start with. This is presumably still a road car so the pads will need to remain good for road use also, and ducting is harder work than paying a mechanic £40 to change the fluid to something much better than whatever "long life 5.1" fluid BMW have probably stuck in it.Gassing Station | Track Days | Top of Page | What's New | My Stuff