BMW 320i disc brakes

[blancojp]

Hello All!

There seems to be an inrush of people trying to upgrade their front brakes to the never ending talked about 320I brakes. This conversion is simple however it requires lots of machine shop work and will make it very expensive for some.

Let us evaluate what is required to do this so called bolt on upgrade:

1) You will need to locate two 320I vented rotor calipers - RAYBESTOS Part # RC3912 / RC3913. The calipers loaded can be purchased around $65-75 each.

2) You will also need to locate two Vented rotors - CENTRIC Part # 12034006. These are available for about $50 each however they are hard to find sometimes. Be carefull when purchasing 320I rotors since they try to pass Volvo rotors as a replacement and they will not fit. The correct rotor is 73mm in heigth and the centering hole is 63mm in diameter.

3) You will need to machine the hubs down to 4.955" in diameter. Reason for this is the rotor fits over the hub and the wheel holds the rotor in place. You might also need centering rings since you will create a balancing issue if you are ridding only on your studs.

4) While the machine shop is working on your hubs, have them install 40mm long studs. This is a requirement since the rotors reduce the effective stud length area 7mm.

5) The machine shop will also need to rework the diameter of your rotors. This is a requirement since the caliper heigth on the Opel spindle is reduced 4.5mm therefore the rotor diameter needs to be reduced 5mm.

6) If your rear brakes are well adjusted, you will not need a proportional valve.

You are now ready to install your new brake system. If you happen to damage the rotor a few months down the line, your car will be at a stand still until you can rework a new rotor. On the other hand, you just spent several hundred dollars upgrading your brakes and other than being vented, you have the equivalent braking power of the '75 Opel brake upgrade. I say equivalent but it is actually a little more since the pad area is slightly bigger. You will also have a possible problem with your wheels since these calipers might hit the inner rim on stock rims. Most people use the words "bolt on" and in an Opel it just means someone did the work for you. Just because you bought the parts and you are willing to spend a few hours installing the system, it does not mean that it will go together as planned. If you are keeping the stock wheels on your car, the most you can increase the diameter of your rotors from stock is 10mm.

The best bet with stock wheels:

1) '86 Chevette solid rotors with '84-87 Fiero calipers. The Fiero calipers have the same 3.5" mounting hole spacing but twice the pad area. You will quickly notice a difference with this setup from the first time you press the pedal.

2) '89 Nissan Sentra vented rotors with a 3/8" thick spacer and '75 Opel calipers with the spacer kit. You will have the advantage of the vented rotor and still use Opel parts to complete the install. The pads are also slightly bigger and the overall is just a 10% increase in braking power.

Now here is a tip for upgrading your wheels for less than $20 each:

If you find a early '90s Saturn SL2C in a salvage yard, you will notice it has 14" rims with a 20mm offset, they are the same Opel 10 hole design and even the Opel center cap fits perfectly. Just add trim rings and you now have 14" close to Opel original wheels.

And as always, enjoy your Opel safe and happy!

[heimue]

Originally Posted by blancojp Hello All! ... you have the equivalent braking power of the '75 Opel brake upgrade. I say equivalent but it is actually a little more since the pad area is slightly bigger....

To be precise, a larger pad does NOT increase "braking power", your brakes do not stop any better and your car doesn't stop any faster.
Larger pads, however, have reduced wear (if compared with smaller pads of the same material) because there is more material that has to come off. Larger pads also are "smoother" in bringing the force (and the heat) into the rotors, which on the other hand increases the life span of the rotors and reduce the risk of warpage under hard braking.
The brake force in the rotor calculates by multiplying the force between the brake shoes times the friction coefficient, which is a value that depends on the material matching between the involved surfaces (rotor and pads), the surface conditions (roughness, hardness), and the temperature. Your brake torque calculates by multiplying the brake force times the brake radius, meaning the distance between the spindle centerline and the center of the brake pads (center of the area moment, but that goes pretty deep in physics and math). The area (size) of the brake pads does not have any involvement in these equations, unless we go in the range of very hard and constant braking, when the temperature gets really high and the friction coefficient might stay higher on a larger pad..
But enough with that complicated stuff, let's get back down in the basement, fixin' the freakin' brakes...

Dieter

[blancojp]

Originally Posted by heimue To be precise, a larger pad does NOT increase "braking power", your brakes do not stop any better and your car doesn't stop any faster. Larger pads, however, have reduced wear (if compared with smaller pads of the same material) because there is more material that has to come off. Larger pads also are "smoother" in bringing the force (and the heat) into the rotors, which on the other hand increases the life span of the rotors and reduce the risk of warpage under hard braking. The brake force in the rotor calculates by multiplying the force between the brake shoes times the friction coefficient, which is a value that depends on the material matching between the involved surfaces (rotor and pads), the surface conditions (roughness, hardness), and the temperature. Your brake torque calculates by multiplying the brake force times the brake radius, meaning the distance between the spindle centerline and the center of the brake pads (center of the area moment, but that goes pretty deep in physics and math). The area (size) of the brake pads does not have any involvement in these equations, unless we go in the range of very hard and constant braking, when the temperature gets really high and the friction coefficient might stay higher on a larger pad.. But enough with that complicated stuff, let's get back down in the basement, fixin' the freakin' brakes... Dieter

I know all of this and I took that into consideration when I wrote the article. There are advantages of having a larger pad area and said advantage actually improves the braking performance. The main idea here is to stop the car with a certain level of reliability.

I get calls all of the time with the so called "bolt on" scenario, and the object is to show what "bolt on" actually means when it comes to this type of upgrade.

[garrymc]

Originally Posted by blancojp Now here is a tip for upgrading your wheels for less than $20 each: If you find a early '90s Saturn SL2C in a salvage yard, you will notice it has 14" rims with a 20mm offset, they are the same Opel 10 hole design and even the Opel center cap fits perfectly. Just add trim rings and you now have 14" close to Opel original wheels. And as always, enjoy your Opel safe and happy!

Thanks, I did not know this.

[broszzy]

Does any one know any thing about the rear end from the BMW 320I? How strong they are? Are possies available for them? I was looking one over today and it looks like it would be fairly easy to narrow for a GT

Pat

[BQS4]

Originally Posted by broszzy Does any one know any thing about the rear end from the BMW 320I? How strong they are? Are possies available for them? I was looking one over today and it looks like it would be fairly easy to narrow for a GT Pat

Some one on the site has already done this, and it wasn't that easy
http://www.opelgt.com/forums/perform...art-1-a-3.html

[hrcollinsjr]

Originally Posted by broszzy Does any one know any thing about the rear end from the BMW 320I?

A little, I have one.

Are possies available for them? I was looking one over today and it looks like it would be fairly easy to narrow for a GT Pat

Yep, I know where one 4.11 limited slip unit is, my driveway. A BMW guy told me that the Cabriolets came with them. IIRC mine came out from under a sedan. Nice upgrade with discs and rear sway bar for my 3 series car.

Harold

[broszzy]

Originally Posted by hrcollinsjr A little, I have one. Yep, I know where one 4.11 limited slip unit is, my driveway. A BMW guy told me that the Cabriolets came with them. IIRC mine came out from under a sedan. Nice upgrade with discs and rear sway bar for my 3 series car. Harold

Thanks Harold

[CaliManta]

Hi!
I'm new to the forum and new to opels as well. I recently aquired a '73 Manta. As my teenage daughter and son will both be driving it on occaision (neither are particularly agressive drivers, but safety is always a concern) I would like to upgrade the brakes. It looks like the driver's side caliper needs to be replaced anyway an I know where I can get one for $60. What I would like to do is get a simple upgrade; the most improvement in stopping power for the least amount of $, with parts that are not too hard to find when it comes time to do the first brake job. I saw on some of the previous threads about a "poor man's vented brake upgrade." Also something about Geo Metro brakes for 120$. Can anyone give me some specifics about a true "bolt on" upgrade? Thanks for your help.

[Lindsay]

Originally Posted by CaliManta Hi! I'm new to the forum and new to opels as well. I recently aquired a '73 Manta. As my teenage daughter and son will both be driving it on occaision (neither are particularly agressive drivers, but safety is always a concern) I would like to upgrade the brakes. It looks like the driver's side caliper needs to be replaced anyway an I know where I can get one for $60. What I would like to do is get a simple upgrade; the most improvement in stopping power for the least amount of $, with parts that are not too hard to find when it comes time to do the first brake job. I saw on some of the previous threads about a "poor man's vented brake upgrade." Also something about Geo Metro brakes for 120$. Can anyone give me some specifics about a true "bolt on" upgrade? Thanks for your help.

Stock brakes in "mechanical working order" are very good. I haven't found a simple brake upgrade (other than steel braided hoses to replace rubber hoses), but somebody can prove me incorrect. Used to be able to shop at AutoZone or Krageon for OPEL parts, but the inventory is now more limited. Opel GT Source is an excellent parts supplier.

[blancojp]

Originally Posted by CaliManta Hi! I'm new to the forum and new to opels as well. I recently aquired a '73 Manta. As my teenage daughter and son will both be driving it on occaision (neither are particularly agressive drivers, but safety is always a concern) I would like to upgrade the brakes. It looks like the driver's side caliper needs to be replaced anyway an I know where I can get one for $60. What I would like to do is get a simple upgrade; the most improvement in stopping power for the least amount of $, with parts that are not too hard to find when it comes time to do the first brake job. I saw on some of the previous threads about a "poor man's vented brake upgrade." Also something about Geo Metro brakes for 120$. Can anyone give me some specifics about a true "bolt on" upgrade? Thanks for your help.

There is no actual true "bolt on" scenario for brakes unless you use the actual Opel parts. If you plan to use stock rims then you are pretty much guided towards a stock setup.

I am in the process of building a vented front brake system that can be used with the stock 13" wheels. I will post all of the details and will also have a few kits for sale.

[Anonymous D]

IMO, this sort of approach should be clearly labelled as experimental, as it affects the most critical safety system on an Opel, which is the brake circuit.

One example, is need for further discussion of individual modifications like the installation of longer studs, which can shear off under stress if the (popularly-sized) 15" or larger wheels are installed. Some who have been in the Opel world for some time can also recall the potentially disastrous advice that was freely promoted years ago by the OANA, that advocated grafting on rear disk brakes from an Isuzu -- which weren't spaced properly to assure safe long-term use, and which weren't preceded with a clear warning statement. Another concern, is that lower component price seems to be driving consideration of brake system alteration, which in my opinion is the entirely wrong motivation.

Consider the rewards versus the risks.

Installing non-Opel brake parts can save a hundred dollars or more, here and there. What is being risked is safety, in terms of possible damage to the car, and potential harm to the driver and passengers (as well as to others on or near a road). Is stating a procedure for non-standard brake modification (with parts that haven't been tested long-term, as have the '75 parts upgrades) truly a cost-effective approach (considering the potential downside, including risks to the health of someone's children)? Is it responsible for an Opel owner to alter their car based on someone else's advice, if it isn't backed up with long-term test results, a manufacturer's warranty, or a liability policy?

[opelwasp]

Any custom built car has its inherant risks. I one chooses to modify their car they choose to accept these risks. There are hundreds of thousands of cars that have been modified since cars have been invented. Most of them void any warrenty or liability claim against the manufacturer. If one wants to be perfectly safe then they shouldn't modify their car in any way and drive an ultra safe Volvo. Or not drive at all. But for me I love to mod, so keep the ideas coming.

[SantaClaw]

An easy, but more expensive route is Pink opel tuning in Germany...


Pink Opel Power Tuning

Old web page, but the brakes on offer are awesome..

[blancojp]

Originally Posted by Anonymous D IMO, this sort of approach should be clearly labelled as experimental, as it affects the most critical safety system on an Opel, which is the brake circuit. One example, is need for further discussion of individual modifications like the installation of longer studs, which can shear off under stress if the (popularly-sized) 15" or larger wheels are installed. Some who have been in the Opel world for some time can also recall the potentially disastrous advice that was freely promoted years ago by the OANA, that advocated grafting on rear disk brakes from an Isuzu -- which weren't spaced properly to assure safe long-term use, and which weren't preceded with a clear warning statement. Another concern, is that lower component price seems to be driving consideration of brake system alteration, which in my opinion is the entirely wrong motivation. Consider the rewards versus the risks. Installing non-Opel brake parts can save a hundred dollars or more, here and there. What is being risked is safety, in terms of possible damage to the car, and potential harm to the driver and passengers (as well as to others on or near a road). Is stating a procedure for non-standard brake modification (with parts that haven't been tested long-term, as have the '75 parts upgrades) truly a cost-effective approach (considering the potential downside, including risks to the health of someone's children)? Is it responsible for an Opel owner to alter their car based on someone else's advice, if it isn't backed up with long-term test results, a manufacturer's warranty, or a liability policy?

This is somewhat becomming your standard statement, since several copies of the same are throughout this forum.

I don't know about you but I build cars for a living, cars that people drive quite hard. I spent 25 years working for a company designing hydraulics systems; with the sole purpose of stopping heavy loads. If the complete brake parts were home made, then there would be a safety concern however most modifications involve drilling a few holes and using very well tested parts.

Modifications to a vehicle based on other people's experience is what the club concept is all about. You have people here that modify engines radically, others add suspension components from other vehicles and so on. But if all club members were to follow your expressed example, all Opels out there would be completely stock without any modifications or improvements.

Experimentation and custom work is what makes a classic vehicle stand out from the rest.

[opelnut10]

The most bang for the buck is the 75 brakes with good hoses and good brake pads. You cannot use the earlier wheels as you will run into clearance issues with the 75 calipers. BMW or the above mentioned Saturn wheels are a buyable upgrade. You are always going to have someone with the "Chicken Little" attitude (the sky is falling, the sky is falling) but I don't think anyone would modify as brake system without testing it in a safe enviorment before just going out on the road in traffic or sending their children out driving without making sure that the brakes are at least up to the standards of the 35 year old stock system. JM2CW

[clayfive]

Blanojp,Opelwasp: Hear, Hear! I'd have to say the most critical safety system is the one behind the wheel.

[Redskinsjbs]

Originally Posted by clayfive Blanojp,Opelwasp: Hear, Hear! I'd have to say the most critical safety system is the one behind the wheel.

Uh-oh, I'm not very sure about this one in my car!!!

[vikesman101]

Sticker on my snowmobile.... "Brakes are for sissy's"