840i Brembo caliper test fitted

[UK215M3]

Uwe, does Ian not mean, (as the 850 has 'leading' calipers) as an example; the offside becomes the nearside, as the change from front monunted caliper to a rear mounted caliper would then mean the smaller piston changes from being at the top to being at the bottom ???

[Ian Godney]

I dont really know how I can explain it any more than the last reply , if you go from laeding to trailing , but swap the caliper from the LH side to the RH side , the pistons will be the wrong way round , to keep the small piston first you have to keep the caliper on the same side but swap the nipples and pipes over

[UweM3]

Ian, I have looked at the pictures again and know now what you mean. I didn't realise that the mounting lugs are "mirrored", I thought they are offset.
So you turn the caliper horizontally as well. That will get the correct piston up but as you mentioned already the brake pipe will come from the wrong angle.
It would need some long term testing to see if the pads really wear that much with the wrong piston up.

[Jake]

Hi guys. I managed to steal this computer for 10 minutes. Trip is going well, I should be back Saturday.

When I get home I'll swap the cross over tube and bleed nipples and take some pictures. Also, Brian has voluteered to try out the E46 M3 disc set up so we'll get that in the works too. Ian should have all my parts by now.

I hope all is well. Miss ya!

Jake Larsen

[m ben]

tho this is not really very exciting, the red calipers w/ "BMW" on them are not the E31 Brembos, rather they're E32 750 ATE 4-pots. they take a similar 324x30mm rotor to the E31 Brembos, but they're much heavier. they're pretty rare as they only applied to late production German-market E32 750's.

as has been noted earlier here the Brembos are pretty light at 3.26 kg each. the E32 ATE's are heavier by a long shot at 6.1kg each. the mongo N'ring (and euro 850CSi) 4-pots are even heavier at 6.7kg. they of course run 345x32mm rotors, but that seems like serious overkill for a lighter car like an E30. as an additional random aside, there is a 4-pot Brembo which was used on 6-cylinder E38's (and thus not in the US) which is nearly identical to the E31's but has a slightly wider (it's less than 1/2") mounting spacing, making it not very useful for anything as making an adaptor bracket would involve overlapping holes which wont' work. it's not noted as Brembo in the ETK like the E31's are, but says Brembo on the back of it.

the E28 guys have been all over the E31 Brembos for at least a year or so. there was a GB for new calipers a while back thru a member in Germany who got them for around $650/pair, but that was back in the days of a mildly strong dollar, so not gonna happen again.

I'll worry about brakes when I get all the other junk done on my car, like getting the motor hooked up. or the firewall repaired. etc, etc, etc.


Ben
waaaay too many projects

[Jake]

Ok I’m back. :D

First thing was to actually try to swap the crossover tube and the bleed nipples to see if it was possible, and it was.




My concern now is by doing this I’ll lose the protector boss which is cast into only one end of the caliper. Here are some pictures:




All the calipers I’ve looked at incorporate some sort of protection boss for this crossover, so needless to say I’m a bit hesitant to go this route. What are your thoughts?

The next problem is the brake line connection port. As you can see in this picture it is pointing down.



Anybody know if I can use a banjo style brake line connection without modifying the caliper? It seems like this would the best fix for this. Here is an example of what I’m talking about (note: this is not the same style caliper, this is for reference only)





The brake line connection port isn’t a big deal to me but I’m not too happy about the lack of protection for the crossover tube. Both of these problems can be overcome by just swapping the calipers from left to right and vice versa, but then we have the issue of the differential piston design configured in the wrong direction. Unfortunately, this is not a compromise I want to live with either.

So… let’s talk about that protection boss. Is it really there to protect the crossover tube or is it merely there to locate it? This could be a deal buster for me.

Cheers,
Jake Larsen

[Ian Godney]

Jake , if the pipe needed protecting then it would all need to be covered , I think they are there to locate to pipe , it would take something serious when driving for it to get damaged , Honestly I dont see it being a problem , also the inlet , I picked up on it pointing down further up the thread , I dont see that being a problem either , as you say just use a banjo fitting ,

If you run a caliper with the piston sizes the wrong way around , it wont loose any performance , all it will do is wear the pads down on a taper , its no big deal but you would need to change the pads earlier when they wear ,

Cheers Ian

[mrsha007]

i say we go with the pistons the right way and swap the other parts,

so let me see if i got this straight for everyone. for this kit we need the following:

840 calipers - 2
e46 m3 floting rotors - 2
rotor spacers - 2
custom hats - 2

questions able things, these are the issues keeping me from jumping on this deal, and im sure many people have the same concerns:

do we NEED banjo fittings?
is someone gonna do a test fit and run?
can we just leave the rear brakes alone? (im guessing sure why not)
23mm or 25mm MC is good enough? ( im guessing if its good for AP, its good for our home kit.)

and i think the number one questions is this:
how do we figure out what offset we need to get the custom hats in, especially if we run a non e30 aftermarket wheel.

anyway, i think it is cool how we are doing a full R&D for a BBK for a 15 yearold car with all these diffrent people from around the world.

[Jake]

It’s been an interesting morning. I just figured out that my math has been horribly wrong throughout this entire adventure. I’m not really sure where I screwed up but here are some corrected measurements:

Hub mounting surface to outboard face of caliper: 2.296” *not* 1.525”
E46 M3 disc spacer: 0.496” (12.598mm) *not* 0.551” (14mm)

I’m very sorry for the confusion as this is quite a fundamental detail of this discussion. Let’s try this again….

Your humble servant :D
Jake Larsen

[Jake]

I think some are getting this offset and back spacing a bit confused. I'm not sure if this is correct, but when I refer to offset, I'm referring to lateral placement of the entire wheel on the strut, regardless of caliper clearance. When talking about back spacing, I'm referring to the distance between the back of the wheel spokes and the wheel mounting surface.

"Net back spacing" is the result of the *wheel* back spacing combined with the thickness of the disc mounting area, plus whatever spacer is required to correct offset. So take the wheel back spacing, add your required spacer (if you need one, in front of and/or behind the disc) and the thickness of your disc mounting surface, and that is your net back spacing from the hub mounting surface.

As mentioned earlier, these calipers take up 2.296” of space from the hub mounting surface to the outboard face of the caliper. You’ll need to figure in some reserve clearance between the caliper and the back of the wheel spokes too; 5mm (approx 0.2”) should be sufficient. So add up your wheel back spacing, spacer set up, and the thickness of your disc mounting surface. If you come up with at least 2.298”, you’re golden. The only trick here is to be sure you measure the wheel back spacing in the correct spot. This caliper requires the 2.298” spec measured at approximately 6.325” out from the center of the wheel. For reference, this is the *wheel* back spacing I measured on the E39 17X8 style 5 and E30 M3 16x7.5 wheels:

E39 style 5 = 0.6365”
E30 M3 16’s = 0.9045”

This is the distance from the wheel mounting surface to the back of the spokes measured at approximately 6.325” out from center. Now add the thickness of the E46 M3 disc mounting surface (0.284”) and the required 0.496” (12.5984mm) spacer behind it, and you come up with 1.4165” and 1.6845” respectfully.

Considering this, the E39 wheel will need an additional 0.8815” (22.39mm) spacer in front of the disc to fit over the E31 caliper giving a 2.298” net back spacing from the hub mounting surface to the back of the wheel spokes. The 16x7.5 E30 M3 wheel will need a 0.6135” (15.58mm) spacer get this same clearance. Of course this will result in poor overall offset (wheel sticking out too far) with these wheels.

Something to keep in mind, spacers combined with E36 fitment wheels will do two things; not only does it correct the offset, but it creates more back spacing, or spoke/caliper clearance. One example is when I ran E36 M3 wheels on my E30 M3 using an 18mm spacer to correct offset. If I were to use this caliper with the E46 M3 disc and the required 0.496” spacer behind it, I would then only need a 0.219” (5.56mm) spacer in front of the disc to put the offset back where it was with the old stock brakes and 18mm spacer set up. Hope this makes sense. However, this still doesn’t mean I would have had the spoke clearance I needed because spoke design still needs to be accounted for. If those wheels hadn’t been stolen, I could have measured the wheel back spacing myself and included the results.

When considering a BBK, keep in mind that all 4 pot calipers require more wheel back spacing because they are wider than fist type sliding calipers, this is unavoidable. You are simply not going to be able to fit stock E30 M3 wheels or most factory 5 series wheels with any 4 pot caliper, they don't have enough wheel back spacing.

Take care,
Jake Larsen

[Jake]

Originally posted by Ian Godney
Jake , if the pipe needed protecting then it would all need to be covered , I think they are there to locate to pipe , it would take something serious when driving for it to get damaged , Honestly I dont see it being a problem

Ian,

Thanks for your input my friend. It’s a bit more comforting hearing it come from you. So it’s a non-issue for the most part.

Originally posted by Ian Godney
also the inlet , I picked up on it pointing down further up the thread , I dont see that being a problem either , as you say just use a banjo fitting

I was hoping it would be as easy as this. :D

Originally posted by Ian Godney
If you run a caliper with the piston sizes the wrong way around , it wont loose any performance , all it will do is wear the pads down on a taper , its no big deal but you would need to change the pads earlier when they wear ,

Cheers Ian

This makes perfect sense to me but I’d really like to avoid it if possible. Running costs would be affected negatively otherwise, and one of the goals with this set up was to reduce them. But I can certainly see how this wouldn’t really affect performance, at least initially.

Originally posted by mrsha007
so let me see if i got this straight for everyone. for this kit we need the following:

840 calipers - 2
e46 m3 floting rotors - 2
rotor spacers - 2
custom hats - 2

Close bro. You don’t need rotor spacers *and* custom hats, they’re for different set ups. You need the rotor spacers if you decide to go with the E46 M3 discs. If this isn’t the route you want to take, then you’re looking at custom hats (bells) and an aftermarket disc of your choice (AP, Wilwood, Ian’s, etc) to bolt to them. Then we need to add the brake line solution of your choice, pads, and mounting hardware.

Originally posted by mrsha007
do we NEED banjo fittings?

I think this would be the best solution, but there are others. You may be able to find a 90 degree elbow allowing you to use your stock spec brake lines but I’m not sure yet. Personally, I think it would be best to have new brake lines made up with a banjo fitting for the caliper end.

Originally posted by mrsha007
is someone gonna do a test fit and run?

As soon as I have everything together we should be able to do a test fit/run. Brian has already offered to come up here and let me test fit and try them out. Realistically, this could happen within a month with all things considered. The only hard part I foresee is locating wheels to borrow. I'd need them soon so I can measure up the necessary back spacing and offset with spoke design taken into account and order custom spacers if required.

Originally posted by mrsha007
can we just leave the rear brakes alone? (im guessing sure why not)

Certainly; although I assume an adjustable proportioning valve may be needed to properly dial in balance. You could even possibly achieve good results playing around with different pad compounds.

[QUOTE]Originally posted by mrsha007
[B]23mm or 25mm MC is good enough? ( im guessing if its good for AP, its good for our home kit.)

This will probably be down to personal preference. For sure either will work though. Either way, we'll certainly see when we test them out on Brian's M3.

Brian, are you still running with the stock MC?

Originally posted by mrsha007
and i think the number one questions is this:
how do we figure out what offset we need to get the custom hats in, especially if we run a non e30 aftermarket wheel.

I think the easiest way to figure this out is to ask others who have the standard Brembo BBK already installed. What ever wheel they use should be compatible with this set up as well.

The only sure way to figure this out is to measure up your wheel back spacing and compare it to what's required. It's just too dependant on spoke design to say for sure X offset with X back spacing works with all wheels and these brakes.

Originally posted by mrsha007
anyway, i think it is cool how we are doing a full R&D for a BBK for a 15 yearold car with all these diffrent people from around the world.

I'm having a blast!

Take care,
Jake Larsen

[Jake]

Development update:

I'm about to order the first round of one-off's from Ian (see the GB post). Here's my current line of thinking...

Most likely, the best way to ensure caliper clearance across the range is to use E36 wheels and a spacer to put the net offset where you want it. With the custom bell/disc approach, if you’re already using E36 wheels and a spacer, you can just order these and your offset will be unchanged (while still using those wheels with your current spacer).

However, I’m going to make a change to the E46 M3 disc and spacer/adapter assembly to include an outer spacer. It will be made to work in conjunction with the inner spacer/adapter’s hub lip it to give a total of 20mm *hub centric* spacing. With inner and outer spacers combined with the E46 M3 disc the goal is to end up with unchanged offset when running E36 17x8 wheels as this is probably the most common size used.

Thoughts?

Take care,
Jake Larsen

[Eric]

I was just thinking about this the other day...

A friend of mine had a "dinan" E34 M5 it had all sorts of Dinan crap on it, including their best brake setup. I don't remember what rotors he was using, but I remember that he had a set of 4 pot calipers with BMW stamped on the face.

Sine dinan is the master of using BMW parts and calling them his own, my guess is that these were either E34 M5 nurinburg brakes, or E31 4-pots.

now thinking back, what trips me out about this is that he was running the stock E34 M5 wheels, which have a pretty low caliper clearence correct? hmmm.

[Jake]

:D Yeah, I'm with ya on the "Dinan" mods. LOL

If they were black and had "BMW" in big white letters, they were probably early E31 calipers. The E34 M5 Nurburgring brake package used ATE calipers IIRC. The calipers are cast iron and weigh a ton. That set up uses huge 345mm discs!

As for caliper clearance, have a look at the 5/7/8 series set ups, particularly the discs; they already have big time clearance from the factory. In fact, the wheel mounting surface of the disc almost protrudes further outboard than the caliper itself. Going to dual sided calipers (4/6 pot) on any of these is a no-brainer. So yes, there is plenty of room to fit these to the E34 without having to screw around with anything else.

This whole thing with trying to fit E31 calipers to my E30 M3 came from the fact that I had a set I was installing on my E34 and thought "what the hell, wonder if they'll fit the M3?" Believe it or not I had no intensions to see this experiment through to the end. I have a ton of new stuff for my stock E30 M3 brakes but I couldn’t help it, I got sucked in. :D

As for my E34, they are a 100% direct bolt on mod. I'm running E31 discs with these calipers making it one of the easiest solutions out there.

Good fun so far. :rastajake
Jake Larsen

[Eric]

Originally posted by Jake
:As for my E34, they are a 100% direct bolt on mod. I'm running E31 discs with these calipers making it one of the easiest solutions out there.

Good fun so far. :rastajake
Jake Larsen

so do you have two sets of calipers or are the ones that your doing all the test fitting on the E30 M3, going to go on the E34?