840i Brembo caliper test fitted

[Carlo M3]

Thanks guys, nice write up so far. Good to see someone is experimenting with some new stuff.

Those E46 M3 disc`s look sick... But I don`t think it`s the way to go for most people.

I`m not a technical guy. So don`t be hard on me when I`m wrong.

I think putting a spacer between the hub and the disc can couse too many vibration when not installed right. As mentioned before, I don`t think many people can handle an extra trackwhith off 28mm also. Unless you are already running spacers and e36 offset wheels you can remove the spacers, which proberly get you into caliper clearance problems.

People who can handle the extra 14mm offset need some spacers at the rear aswell, to match the front wheel trackwhith, I think. Otherwise the car gets unbalanced and will oversteer easier in hard corners.



Good luck. Love to hear about the first test drive soon.

[vodomagoo]

look into wilwoods bells and rotors pretty good pricing and tons of options

[mazenz]

this is mildly off topic, but im just trying to wrap my head around this whole e46 rotor stuff. my question is will the e46 m3 rotors fit on otherwise stock e30 brakes? or are they just another way to get the 840 brakes to fit?

[Ian Godney]

Jake , please dont take it that I am trying to put what your doing down in any way , just trying to give my experience I've picked up along the way , as long as the spacers are done right there should be no problems with running spacers behind the discs , but if there not done right , you will get problems .

When a disc is made , both side where the pads touch , and the surface where the disc sits on the hubs must be machined at the same time to make sure the 3 surfaces are all running true with each other , if you machine one side of the disc , then turn the disc around in a lathe , it doesn't matter how much you clock it up , if you then machine it , it will never run exactly the same as the other side of it, if you have the two sides of the discs runnning untrue , then you will get steering wheel wobble , or pad knock off , for those who dont know , pad knock off is when the discs are moving side to side in the calipers by not running true , and this pushes the piston back into the calipers , so when you hit the brakes they dont work properly as the first pump of the pedal is pushing the pistons back out , the second pump makes them work , I have experienced this in rally cars , and when your flying down the straight leaving your braking to the latest time possible , it can become a brown trouser ( pants ) moment !!

The only problem with making a spacer to fit between the disc and hub , is that it would have to be turned around to machine the second side , which is when problems can start , its only got to be a couple of thou out , by the time you fit a big disc on top of it the outside edge of the disc can be running out loads , which will give you problems , you have to be very carefull making them , as long as they are made perfect , then there will be no problems , as mentioned above , the hot discs will be further away from the bearings which does no harm , also take into account that the standard wheel bolts will no longer fit , you will need them the thickness of the spacer longer.

Once Jake emails me the drawing I will make a pair and see how they turn out , if they can be made with no run out I will be able to supply them

Cheers Ian


Mazenz - no the discs wont fit with the standard calipers , the caliper would need bringing out on a bracket as the discs are bigger , but the discs are also thicker so wouldn't fit inside the calipers anyway , you would need to change the calipers as well.

[UweM3]

I might miss something but the 7 and 8 series do have the calipers in front of the strut, the M3 at the rear.
Don't you have to "change" the caliper from LH to RH to keep the staggered pistons in the correct order?
I was looking at these calipers a while ago, but didn't fancy the spacer under disk option for the reasons Ian pointed out.
The custom bell/disk setup is my prefered option.

[Ian Godney]

Uwe , yes you would have to swap them side to side , if you didnt the larger piston would be first , and the bleed nipple would be at the bottom of the caliper

[UweM3]

Ok maybe I haven't explained good enough. I wasn't talking about the caliper physically fitted from LH to RH. That's clear. I have to do this with the sliding E32 calipers I have as well.

I was talking about "switching" the caliper itself. You will have the wrong piston order because you change the direction of the disk when taking the RH caliper to the LH.

The radial mounted like you use can be turned upside down and the bleed nipple swapped with the connector pipe, but I fail to imagine that this can be done for the lug mounted version.
Do you know what I mean?

[Ian Godney]

Ok I see , yes when using the 850 caliper I can see from jakes pictures that they dont have link pipes , so you cannot turn the pipes around with the bleed nipples , so yes , if you go from a leading position ( front of strut ) to a trailing postion ( rear of strut ) then yes the large piston would lead , the only problem you would have with this is that the oads would wear down on a angle as they would dig in more than a smaller piston leading , your pads would need changing more often , but as regards to the way the calipers works , there is no difference in braking performance that I have found

To add , even with lug mounted calipers , as long as you can change the pipes and nipples around you can swap them side to side

Cheers Ian

[Jake]

Great point Uwe! I neglected to catch that. :D The fix would be to keep each caliper on it's appropriate side, but swap the bleed nipples and cross over tube. Very easy swap.

Cheers,
Jake Larsen

[Jake]

Originally posted by Ian Godney
Jake , please dont take it that I am trying to put what your doing down in any way , just trying to give my experience I've picked up along the way , as long as the spacers are done right there should be no problems with running spacers behind the discs , but if there not done right , you will get problems.

Hi Ian. No worries my friend. We really are on the same page here. I'm concerned about vibe problems as well. The only way to test out the theory is to put it into practice and see what happens. Apparently this set up has been used for some time in Germany. Dave (UK215M3) said there is/was a guy selling these in kit form over German Ebay.

BTW, I just took delivery of the spacer (Thanks Dave!). Here are some pictures of the full assembly.











Here are some more measurements:

- Disc outboard mounting face to caliper outboard face:
1.525”

- Lateral disc clearance from caliper at closest point:
0.102” (same on both sides)

- Caliper mounting ears spacing, bolt center to bolt center:
4.803”

HTH,
Jake Larsen

P.S. Ian, I’ll be calling you in a minute. I have one disc, hub, spacer assembly packed up and ready to send you.

P.S.S. Dave (UK215M3), thanks for getting the spacers in the mail so fast mate. They really do look superb! I’d like to see if we can close up the disc to spacer tolerance a bit but other than that I’m very impressed. Thanks again. You’re my hero!! :D

[JEDM3]

Only one problem. How long until we see it actually installed on a operable car??:D
Jake, have you figured out wheel backspacing and min. diameter? I assume 17" min but wonder about wheel fitment.
Looks awesome, nice to see the cooperation among various parties on this project.
Regards,
John

[Jake]

Ok ok.... You gotta point John. LOL :D It will be a while before my M3 is back on the road. I wish the practical portion of this experiment could be accomplished sooner. All I can say is I'm pushing VERY hard to get there. I've been properly motivated, and I have the resources to see it through, it's just a matter of time. Work isn't helping much; they've got me going a few places this summer which will seriously cut into my time in the garage. But I'm obsessed more than ever and believe me, every waking minute is a one more minute of progress.

Ian, the package is shipped. They said it could be there Monday but no later than Wednesday. You'll find a new hub, spacer, and E46 M3 disc ready to go.

Cheers,
Jake Larsen

[Ian Godney]

ok no problem , give me a ring end of next week for an update if your not near a computor

[Jake]

Originally posted by Jake
P.S. Sorry Sleepyfox, I must have missed your post earlier. I measured the pistons for you and came up with approximately 1.432” for the lag piston and 1.586” for the lead.

Sorry, swap this around. The lead piston will be the smaller of the two, assuming we swap the bleeder nipples and cross over tube.

Cheers,
Jake Larsen

[UK215M3]

Jake, further to our discussion regards brake balance front to rear. Here's some details that show this set up would/ should need to increase rear braking to restore the factory balance. Ian, being the GURU on these please chip in if i'm talking Bo@@*ks.

If we assume that the tires are of good quality at all times. By increasing the power of the front brakes we can disturb the front/ rear balance and actually INCREASE stopping distances (even though feel will be vastly improved), as what we have effectivly have done is DECREASE the rear braking power ( as the weight of the car always stays the same).

Take a look at these factory set ups and you can see the rear e30 M3 set-up will be underpowered.

CAR - FRONT/REAR - DISC SIZE - PISTON SIZE

e30 m3 - F - 280x25 - 54mm
e30 m3 - R - 282x12 - 38mm

850 - F - 324x30 - 44mm/40mm (? 40mm/ 36mm) (59.9 on the single piston version)
850 - R - 324x20 - 39.9mm

e46 M3 - F - 325x28 - ?????mm
e46 M3 - R - 328x20 - ?????mm

e36 M3 - F - 315x28 - 59.9mm
e36 M3 - R - 312x20 - 39.9mm

Z3M - F - 315x28 - 59.9mm
Z3M - R - 312x20 - 39.9mm

e34 540i - F - 302x28 - 59.9mm
e34 540i - R - 300x20 - 39.9mm

e34 M5 - F - 315x28 - 59.9mm
e34 M5 - R - 300x20 - 39.9mm


PROPOSED SET-UP
850 - F - 324x30 - 44mm/40mm (? 40mm/ 36mm)
e30 m3 - R - 282x12 - 38mm


I would think the rear disc should come up in size AND fittment of a 39.9mm caliper would help retore the lost balance. it's worth noting that front and rear disc sizes are almost equal in all these examples.

I'm currently looking into this with Jake's un-relenting help.

If we assume a basic car weight of +/- 2700lbs (road spec) and a weight distribution of 52/48 that means +/- 700lbs static weight on a front wheel (?).

Ian, (Gustave ?) do you have any algorithims to help work this out, with this information?