My MC is new but my pedal still feels like @$$.
squishy? or hard?
Any remotely modern car with disc brakes is going to be traction limited when it comes to stopping distance, so yes, if you want to increase braking G-forces and decrease stopping distance – buy better tires.
However, improved stopping distance is not the real benefit of a braking upgrade unless there is unfavorable bias that the upgrade corrects which would maximize available traction from all 4 tires. True brake upgrades have the ability to absorb and dissipate more thermal energy by way of increased thermal capacity from increased rotor mass, and often improved rotor cooling due to an improved rotor vein design and/or a thicker rotor.
Recall that the Volvo “upgrade” started in the days when 323i calipers were very expensive, long before the days of Rock Auto selling $30 Centric remans. I recall seeing caliper prices in the $300 range, while the volve calipers could be had for around $60 at that time (I did this modification around 2002/03).
That said, is the Volvo caliper modification an upgrade? Compared to the stock 320i solid disc brakes – absolutely – but only because it allows you to run vented rotors. Is it an upgrade over 323i brakes? I would say that depends, but if you’re only upgrading the front – probably not. It’s not a serious performance brake system. You’re still running a little 255mm front rotor which will quickly heat soak in any high performance driving situation.
The Volvo caliper has a 7 sq in surface area, compared to 5.6 sq in for the stock e21 caliper. This will result in a softer pedal (unless the master cylinder is also upgraded), along with increased front bias. Here is the bias change comparing the stock 323i brakes to the Volvo front caliper, as well as the Volvo caliper running the 276mm mini rotor:
Rotor Size Front Bias Brake Tq increase Rotor Size Rear Bias 323i stock 255 65.9% 0.0% 258 34.1% Volvo fr/323i rr 255 70.8% 25.3% 258 29.2% Volvo-mini fr /323i rr 255 72.8% 38.2% 258 27.2%
As you can see, the front bias increases significantly just from this modification. While you do get the benefit of a vented rotor, you’re not likely fully utilizing available rear tire traction. This means that stopping distance will likely suffer, and you may induce increased dive when braking (which is also a function of suspension geometry and many other factors).
Cliffs notes:
Is the Volvo setup better than stock 320i solid disc brakes? In terms of rotor cooling, yes. In terms of bias and vehicle balance, no.
Is the Volvo setup better than stock 323i? In light of readily available cheap 323i calipers, no.
Is the Volvo/Mini 276mm kit an upgrade? Only if you can also upgrade the rear setup to restore proper bias. I’m on the lookout for a vented rear disc option to keep overall bias as close to the stock 66/34% range. This likely means a ~280mm rotor with a caliper piston of at least 35 to 36mm.
- - - Updated - - -
I ran this setup for years with a stock master and 323i rear discs. the pedal feel will be softer than stock without a master upgrade. If you're still running drums and the stock proportioning valve that could be a significant factor. Make sure the drums are properly adjusted and you're fully bled.
The pedal is super soft and stopping power is poor. I am still running rear drums, but I do have a Wilwood valve installed. Maybe adjusting the valve will help. I'll play with it tomorrow and if I can't figure it out I'll probably just get a pair of '77 calipers.
Just FYI, I had similar issues with ine after installing the volvo calipers. The issue turned out to be that I had no idea how to bleed these new calipers, being that each caliper has 3 bleed screws. I took it to my mechanic, and he was able to bleed the brakes properly. After that, the pedal was very stiff, and the brakes lock the tires up easily.
yeah, sounds like a bleeding problem to me. Stopping power shouldn't be poor, the results should be the opposite.
Merry Christmas Brothers.
Josh helped me modify my Hartge/volvo calipers. They felt stronger than the stock e21 323i, as everyone said, you most likely have air in the brake lines that could do it
1) Rebleed brakes
2) Replace MC
3) Check Brake line connections.
"..Horsepower is a measure of work done over time, or the rate at which work is done."
http://www.cardomain.com/ride/579694/1
Brian, have you tried using a power bleeder?
Yea I'm going to hit them with a power bleeder tomorrow morning, I'll let you guys know how it goes, hopefully it's just a bleeding issue.
when I replaced all my lines a couple months ago it took two bleed sessions with a power bleeder to get all the air out. good luck man
Yes power bleeder is awesome and you do need to bleed all three in order to remove all the air from the line. I like to reverse bleed it's easier to push the air up than it is to force it down. Just get a large syringe and back fill the system threw the bleeder screw. You will see all the air come up threw the MC.
I replaced pretty much every component in the entire system including the BMC, CMC, clutch slave, hard lines, soft lines, front calipers and rear wheel cylinders. I'm bleeding the system in that order.
I did a M20 swap last year and changed the reservoir while I was there, then I bleed and bleed and bleed and couldn't get a drop a drop of fluid. a mechanic friend walked over and asked, "did you drill out the tap"? doh!
Tom D
77 e21 - m42
88 e30m3
04 330 dinan3
84 r1000rt
02 r1150rs
all of them gray
14 f800gsa - red headed stepchild!
Always had trouble bleeding all the air out, until I started pressurizing the reservoir. Then it seemed to work easy.
Where on the reservoir might I tap it, and how do you keep that pressurized against fluid exiting and air entering?
- - - Updated - - -
Thanks for chiming in, Josh, and thank you for the original instructional with pictures to help me and others.
Your posts and replies typically present appropriate technical documentation, along with clear explanations, which helps guide some of us who are inexperienced or less mechanically inclined. The possible counterpoints and their rebuttals makes me wonder if you're going to law school at night though haha
But really, the clarity and objectiveness you often bring is welcome in all discussion.
But enough fluff--what's going on with the tabular data?
- Our e21 wasn't even included in any one of the three test examples...
- REVISED IN LIGHT OF FORUM MEMBERS' EXPLANATIONS For the calculations, with my concerns regarding: Volvo compared to 320 but the data doesn't even include the 320! Then Volvo compares to 323, yet the table shows Volvo paired with the 323?
Hopefully you could still offer your experience, withstanding my rants, as to whether the stock proportioning valve will work well enough to go alongside a new e12 master cylinder with Girlings..Thanks!
Last edited by Allenwilson33; 12-19-2015 at 06:11 PM.
allan,
the brake calipers for the 323 and 320 are for all intensive purposes exactly the same, but the reason josh excluded the 320 is because the whole objective of this exercise to to gain the advantage of vented rotors and thus better brake cooling. since the 323 came with vented rotors and the 320 did not, the 323 was his base for comparison. however, since the 1977 320 also came with vented rotors it could be included alongside the 323 as the base to compare.
the bias is a mathematical equation of fluid displacement. the master brake cylinder can only displace so much fluid with a single pump. how much of that fluid goes to the rear is regulated by a hydro biasing valve and the rest goes to the front. when changing to a volvo front caliper with it's larger piston, the bias of the fluid being sent from the master cylinder now becomes greater as a ratio to the front and less to the rear. this can be computed mathematically, but its probably just as easy to actually measure it by cracking the bleed valves and pushing the brake peddle.
now the brake torque i would have to think about. as you know torque is the amount of work or twisting force done around a central axis. one way to increase torque without increasing the effort (pushing the brake peddle/master cylinder fluid displacement) is by increasing the lever, but since the rotors are the same diameter and therefore all have the same size lever this is not the case. so that would mean that the increased brake torque is the sum of the lever times the bias. this would also mean that if the brake torque increases alongside the front's increase bias then the rear brake's torque would decrease along with it's decrease bias.
Last edited by Tom D; 12-19-2015 at 01:48 PM.
Tom D
77 e21 - m42
88 e30m3
04 330 dinan3
84 r1000rt
02 r1150rs
all of them gray
14 f800gsa - red headed stepchild!
I checked some of it, so I can say you can be confident in it.
I can tell you the 5.6 square inches is correct as a calculation. It comes from two times the cross sectional area, of a 48 mm piston, which is common for ate front calipers, used by bmw, porsche, and alfa romeo. The clamping force of a caliper is the fluid pressure times the piston cross section area. So calculate the 48mm piston area, and double it for two front calipers, and convert to inches you get 5.6 square inches.. So it seems, so far as i am concerned you can have confidence in the numbers. I don't think I'd call it a huge increase in front bias though.
Alright, thanks Tom D and Okiflats for bringing me up to speed on the pre-req'd. knowledgebase.
But let me verify I'm getting this right: Front Girling calipers on 255mm vented/slotted Brembo rotors and REAR Drums would produce 70/30 bias, but the calculation would remain the same if rear 258mm discs were used in place of drums, right? Or does my use of rear drums skew the calculation? I'm inclined to guess that a given proportioning valve would be able to keep the 70/30 bias consistent, regardless of whether discs or drums are being used in the rear, no?
So it follows that we must ask ourselves, what the desired bias should be for our e21? I'm presuming some of you can merely reveal a good benchmark bias for me to aim for.)
And do we have approximate calculations for the three test example setups, if we run them through 24mm big bore? (I will attempt to work it out if the formula if the formula is not too complex.)
More to the point, can I use my factory proportioning valve to route Front Girling calipers through e12 24m big bore and rear drums?
Thanks!
Thanks. I'm not in law school, but I did sleep at a Holiday Inn express last night. I'm also the R&D manager at ECS. We design many high performance parts for German cars, big brake kits being one of them.
I didn't include 320i/drum brake calculations for several reasons: 1) I do not have access to drum brake parts to gather the necessary measurements to accurately calculate brake torque. and 2) even if I did, calculating brake torque of a drum brake system is far more complicated than disc brakes due to the lever action of the actuation system off the shoe pivot combined with the unequal friction distribution for each shoe due to the direction of drum rotation (see here: http://www.roymech.co.uk/Useful_Tabl...um_Brakes.html)
That said, I expect that both the drum brakes and 323i rear disc brakes will result in very similar brake torque, assuming the drums are in proper working condition and adjusted correctly. The front calipers and rotors will result in identical brake torque, with the only difference being the thickness of the rotor and caliper.
Brake torque is a function of the clamp force x pad effectiveness (which is the coefficient of friction of the pads) x the effective radius (which is the radius at which the clamp force of the caliper acts - the distance from the center of the hub to the center of the caliper piston). Clamp force is simply line pressure x caliper piston surface area (F=P*A). It is possible to get a quick and dirty approximation of brake torque without taking in to account pad surface area or actual pad coefficient of friction. As pad surface area increases, the psi between pad and rotor goes down and the thus the friction is also reduced, so total force stays close to the same regardless of pad size. Of course, a larger pad will offer improved pad wear and perhaps better heat dissipation in to the rotor for this purpose it can be ignored. The primary factor is piston size and the location of the piston.
Brake bias is simply the ratio of front to rear brake torque. Increasing front brake torque will have no effect on rear brake torque, however it will affect bias.
The chart shows the difference between stock 323i, to volvo caliper/323i front rotor combined with 323i rear, and volvo caliper/276mm mini front rotor combined with 323i rear.
Think of it more as a transfer of pressure than fluid displacement. Actual fluid displaced is very small since piston travel very little. It is a mathematical relationship of master cylinder piston size to caliper piston size. You also have to take in to account dual sized masters in many applications. When it is unclear what's going on with the hydraulic system (either due to unknown front/rear master size, or proportioning valve, or in modern cars electronic control with abs pumps) it is possible to thread a hydraulic pressure gage in to the bleeder screw and measure line pressure front and rear. You still need to calculate brake torque from that, and then look at front to rear bias.
I would assume the bias is the same as the 323i - 66/34. Most BMW's are usually in this range, though some other euro's I've worked with are closer to the 70/30 range. Some more modern BMW's are in the 60/40 range, likely indicating that they have far less weight transfer due to lower center of gravity and improved suspension geometry. As for determining the perfect bias, it is going to depend on the car. If you lower the car you will change the amount of weight transfer when braking. Other modifications may result in changes in front to rear weight distribution which is also a factor. That said, most manufacturers usually set bias higher in the front to ensure the rear wheels don't lock up before the fronts to improve the stability of the car when braking at the limit of traction. Increasing rear bias slightly will often result in reduced stopping distance as you will utilize all available rear tire traction. However, going too far can make the car unstable at the limit. Once a tire locks up the dynamic coefficient of friction is much lower than static, so if you lock up the rears first the back end can slide out resulting in uncontrollable oversteer, particularly in a turn.
Last edited by jrcook320; 12-19-2015 at 07:28 PM.
Yes. I have also heard that you can use the ALFA Romeo front calipers on the front of the e21. People have also used the Ford Falcon from Down Under for a massive caliper swap that is bolt on!
Big shout out to Josh - for the write up of this upgrade and for tweaking my front calipers by drilling them out to get them to sit just right.
I can tell you guys, I have not driven my car for years. But..these things griped very well, with the green brake pads, and 323i master cylinder, and stainless steel brake lines which are t connected to the Hartge/Volvo Brakes. Its a good upgrade for a street car.
For the track you want those large calipers that are from Down under, or the massive brake's wildwood kit.
"..Horsepower is a measure of work done over time, or the rate at which work is done."
http://www.cardomain.com/ride/579694/1
I bled some more air bubbles out of the passenger side caliper today. Still doesn't feel quite right but much better. I need the exhaust to be done before I can road test it any more, it's just too loud with the open header.
When using an e12 master cylinder, is there a better choice between the following brake line routing setups?
1) Running all five brake lines: four lines to the front (two for each caliper) and one for the rear
2) Running three lines (running two up front, one for the rear, and plugging two of the ports)?
How do you like the ECS merge with Turner?
The blog post I read a few months back seemed to indicate that their R&D department would remain autonomous. But if I guessed wrong, then I'm presuming you, Josh, have the keys to Conforti's magic box?!?
Reviving this thread to revisit this table. A couple questions:
- Does the 323i have a proportioning valve like the 320 and is a proportioning valve considered in the above calculations?
- I saw Josh (OP) used an aftermarket adjustable valve, was he running E30 rear calipers at this time or drums & trying to achieve original balance?
- Has anyone calculated how much rear bias is added when replacing 323i rear calipers with E30 calipers? I can see this gaining some popularity considering relatively inexpensive parts and more readily available aftermarket pad compounds.
Last edited by sonomaGTLN2; 06-28-2021 at 11:12 PM.
.: M42 Swap Thread M42 Turbo Build Thread E85 Conversion :.
My YouTube Channel: https://youtube.com/c/AdamPE21
Bookmarks