Brake upgrades...help please

Post Wed Oct 24, 2012 9:12 pm

I have an M40 turd coupe 1990 and as you know the front brakes and callipers can often give rubbish performance by today's standards.

I have 15" BBS's and was wondering could I use brake callipers/discs from a 325i as they hold vented discs with the upgrade of a steel braided lines, and still run it off the current cylinder and servo?

Its just I have new tyres and wanted to improve the braking performance as I do motorway miles.

So basically 325i brake setup would it make a difference?

Any help would be appreciated!

Post Thu Oct 25, 2012 11:35 am

Yep you can fit the vented front 325i stuff with no issues, that'll help with resistance to brake fade (but you don't get extra braking torque). As far as I know the 325i caliper and master cyl areas are the same as the base models.

Might be worth trying to get the 325i rears as well although that's more work. (worth checking the bias valves are the same if you change from rear drums to rear 325i discs)

Hope that helps!

Post Thu Oct 25, 2012 3:30 pm

keri-WMS wrote:Yep you can fit the vented front 325i stuff with no issues, that'll help with resistance to brake fade (but you don't get extra braking torque). As far as I know the 325i caliper and master cyl areas are the same as the base models.

Might be worth trying to get the 325i rears as well although that's more work. (worth checking the bias valves are the same if you change from rear drums to rear 325i discs)

Hope that helps!

Hey, yeah man that makes more sense and yeah it does help, would it not produce slightly better torque if its a 325i setup on the front, as in an improvement at least?

To be honest I was looking into the WMS setup, but will do that once I have an M50

And yeah Im going to be fishing for a "rear disc trailing arm" setup soon aswell, start preparing for the do-able things now because im guessing 325i stuff at the front and back would be better than the standard non vented discs and drums..

Post Thu Oct 25, 2012 3:33 pm

As far as I know the vented and non-vented front discs are the same diameter, have the same diameter pistons in the calipers and take the same pads (99% sure?).

In which case the torque for a given foot pressure is exactly the same. The difference is they are that bit less likely to overheat!

Post Thu Oct 25, 2012 3:37 pm

Fair enough, yeah the diameter is the same, the width is different, from being:

12mm Non-Vented
22mm Vented

280mm in diameter

Just may buy a rebuild kit for the callipers and should be better than what I have now lol

Post Thu Oct 25, 2012 4:01 pm

260mm not 280mm!

Post Thu Oct 25, 2012 4:03 pm

yeah lol sorry...long day at uni haha.

Post Thu Oct 25, 2012 6:33 pm

Tanveer wrote:I have an M40 turd coupe 1990 and as you know the front brakes and callipers can often give rubbish performance by today's standards.

I think you may be mistaking braking performance with pedal pressure. The two are completely different things - for example, I once had the experience of driving a few laps of a circuit in a single seat race car. The brakes on that thing had incredible performance, but the pedal pressure required was around 80kg - enough to push me up and out of the cockpit if I wasn't belted in.
The E30 was designed at a time when men were men, and the pedal pressure chosen accordingly. If the designers so wanted, they could have designed the brakes so that one finger pushing on the pedal would be sufficient.

Post Thu Oct 25, 2012 7:28 pm

keri-WMS wrote:As far as I know the vented and non-vented front discs are the same diameter, have the same diameter pistons in the calipers and take the same pads (99% sure?).

In which case the torque for a given foot pressure is exactly the same. The difference is they are that bit less likely to overheat!

This is correct, I found out the hard way on an E30 I bought that had a caliper swapped by a previous owner, it had solid discs and one vented caliper/carrier on the drivers side, I was driving up to a junction and pressed the brake pedal, a pad shot out and the pedal hit the floor

luckily there was nothing coming and I coasted left without causing an accident!

Post Thu Oct 25, 2012 7:33 pm

Okay from what you guys are saying then would it be better to at least do it so there are vented discs as opposed to the solid ones I have?

And just rebuild them with new seals etc...

Post Thu Oct 25, 2012 8:39 pm

Basically, you can throw money at vented brakes from a 325 or whatever if you want, but the brakes themselves aren't going to be better. They'll be less prone to overheating, but they won't stop you quicker.

A 6 cylinder boat anchor is a lot heavier, which requires a lot more braking force, which creates more heat. Hence vented discs. Have you ever had brake fade? If not do you see a need to convert. It appears more desirable, but not nessacery. Same as rear disk conversions.

Post Thu Oct 25, 2012 8:56 pm

Okay that sounds that it makes sense then, just thought it would help. Apart from good tyres anything else that I could use or upgrade to increase the stopping power, not buy a lot but and at least make them better...

From this I was thinking of buying a rebuild kit and re-do the seals etc with-in the calliper?

Post Thu Oct 25, 2012 9:02 pm

Fast road pads - EBC green etc.

Post Fri Oct 26, 2012 12:05 am

suedenim wrote:Fast road pads - EBC green etc.

Sorry, thats utter b0110cks. Those things need to be at a much higher temperature before they start to work better than a standard set of pads.
If Tanveer drives a lot of motorway miles and does a number of miles between brake applications, he'll need them to work from a very LOW tremperature (after all, you dont drive up the motorway, braking every 5 seconds.... or at least you shouldnt need to.)

Service your calipers, fit new standard discs and pads and maybe some fresh flexi lines to improve the pedal feel and you'll notice the improvement and increased confidence in the brakes.

p.s. painting the calipers red doesnt make them go or stop faster

Post Fri Oct 26, 2012 12:40 am

Greens are (last time we tried them) not good from cold. In fact Reds appear to be better from cold and they are the next step up!

Lets get to what's needed/wanted:

- Less wheel locking during emergency stops = get better tyres (wider helps normally too).
- Less brake fade where the pedal stays hard = get higher temp pads and/or vented discs.
- Les brake fade where the pedal sinks = replace your brake fluid with some nice new dot 4.0 or 5.1.
- Less "stickey/crap/lopsided brakes" = rebuild your calipers if they are sticking, free up the pads etc.
- Less pedal effort = larger servo, faff with smaller m-cyl (bad idea) or proper brake upgrade with larger discs.

Which one(s) fits?

Post Fri Oct 26, 2012 3:28 am

Yes! Thanks Scott and Keri thats pretty much the decision I was going for, and hoping it would work out better.

Basically I might just get a 325i setup at the front, and..if I can get the Steel Braided hoses...If not, replace the current ones, and rebuild the 325i Calipers and stick em on with new pads and discs the next time I give the brakes a service.

Kinda the page I was leaning to if you know what I mean.

Thanks for the help guys, any other info please do share.

Post Fri Oct 26, 2012 9:11 am

SCOTT325SE wrote:
suedenim wrote:Fast road pads - EBC green etc.
Sorry, thats utter b0110cks. Those things need to be at a much higher temperature before they start to work better than a standard set of pads.
p.s. painting the calipers red doesnt make them go or stop faster

My apologies for misleading the OP, I thought they were just a quality OEM spec