jrhone

My Volvo BBK upgrade impressions.....

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I just did the Volvo BBK upgrade on my 76. I got the calipers from a board member that had a fresh rebuild and powder coating, new pads and I added new slotted and drilled rotors. When I installed them, I didnt bleed the rear brakes. So the pedal feel was a bit mushy. Today I bled them all around and WOW what a difference. Firm pedal feel, VERY good brake response and if I jump on the brakes, they will lock up...I am very pleased and would easily recommend the upgrade to anyone in need of replacing pads and rotors. Especially if you get a good deal on the Volvo Girling calipers which are basically a bolt on for a standard 2002. Now I will do the rears with 320 drums. My rears are pretty bad, so I know this will improve the braking even more!

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Which master cylinder do you have? Which rear cylinder? I've always liked the volvo calipers over the 528 because the pistons are smaller.. This give a little more hydraulic leverage over the front brakes.

I'm guessing you can lock up the front, but not the back.

I've never quite gotten the balance right...

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remember... a vast majority of the change you felt is from new pads and properly adjusted brake system....not from the vented rotors or calipers.

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I would say the biggest change is going from brakes that have 34mm pistons to those that are 38mm. Much more leverage over the brakes.

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i did a similar upgrade to mine i went with tii struts and e28 5 series calipers, tii master, and tii vacuum booster. i also did e21 250mm drums in the rear. be carefull with the park brake cables you might need to trim 5-10mm out of the park brake cable conduit because when you step up from a 230mm drum to a 250mm the park brake cables are not long enough. iv bin told that 2002 turbo park brake cables are the answer to this condition but they wear to expensive and hard to cum by so i didnt buy them. that upgrade you did can be done for extreimly cheep. all you would have to is go to pick a part find a 240 body style volvo and a e21 bimmer and your set all the parts can be harvested from those 2 vehicles.

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Which master cylinder do you have? Which rear cylinder? I've always liked the volvo calipers over the 528 because the pistons are smaller.. This give a little more hydraulic leverage over the front brakes.

I'm guessing you can lock up the front, but not the back.

I've never quite gotten the balance right...

I am stock in the rear and using the stock M/C as well...

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remember... a vast majority of the change you felt is from new pads and properly adjusted brake system....not from the vented rotors or calipers.

Really? Its not the fact he doubled the friction surface of his front calipers?

There also seems to be a lot of confusion about hydraulic leverage. A larger M/C will give you less leverage at the pedal which means the pedal feels harder, moves less (throw), and requires more driver effort for a given hyd. pressure at the caliper. The opposite is also true. A larger caliper piston will give more leverage at the pedal which means the pedal feels softer, moves further, and requires less driver effort for a given hyd. pressure at the caliper.The opposite is also true. The goal is to create a setup that allows good modulation at the threshold of lockup. Locking up the brakes in a car is easy, slowing the car at the maximum rate possible takes a little more work.

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According to EBC The tii pad is 89mm x 70mm. The standard 2002 is 76x58.

So the additional pad surface area is 41% more. That is pretty significant..

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The vovlo pad is even a little bigger than Tii if i remember correctly. When i put volvo calipers and 320 drums on my '72 the car was down for about a month and i remember not being overwhelmed by the amazing new braking power. It was 6 months later when i visited my brother and drove his '72 with stock brakes in great condition back to back with mine did i realize the difference. Night and day.

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I have the 320i drums and volvo fronts. The rears lock up way before the fronts, stock MC non-tii. It's definitely the system re-fresh that you're feeling, but if you drive hard on some windy roads for a while you'll notice less fade. should have seen the look on my friends face when the stock brakes started smoking bad, me "hmm, brakes don't seem to be working too well" stop the car and smoke starts pouring out of all wheels, he thought the car was on fire.

As for pad area, friction coef is constant so pad size is irrelevant in terms of braking force, larger pads = slightly longer life. However you also have a larger portion of the rotor being heated(although less heat per square inch since the pressure on the rotor will be less with larger pads) so cooling will be affected. Theory is good, data is better, rarely does theory end up 100% correct with all the variables in the real world.

Meh, for a street drive car it's a fine upgrade. I like mine, wish I had a bias adjuster so I could go a little harder on the brakes before the rear wheels locked up. You definitely DO NOT want the fronts to lock up first, that's dangerous since you'll lose steering when they do. Everyone has their own opinions, since you're not racing and it didn't make the car any less safe or noticeably increase unsprung weight, why worry? my $.02.

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Manimal, you beat me to the area/braking force answer.

What size rear cylinders are you running? And which shoes?

I only had rear lock problems with the 22mm cylinders with carbotec green compound

from Ireland. The 19's were fine. But that was with Hawk Blues in front.

Pad/shoe material WILL make a big difference in stopping force.

t

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I'm not sure what I've got in the rear, probably stock '02 cylinder with generic replacement pads. I didn't check for a name the last time I pulled the drums off but nothing stood out either. It works decently for my use, no more fading, just the early locking problem.

Also consider, pad material will affect rotor life. Completely different vehicle, and extreme example, but my roommate upgraded the brakes on his van(rotors/calipers/pads/master cyl) to eliminate fade when moving 15 people and towing 15,000+ over mountain passes(the van is insane, I'll get a pic in a few days once it's loaded up) and he goes through a set of front rotors every year. At least they're not cracking anymore, just wearing out.

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I like mine, wish I had a bias adjuster so I could go a little harder on the brakes before the rear wheels locked up. You definitely DO NOT want the fronts to lock up first, that's dangerous since you'll lose steering when they do.

That's backwards, you want the front to lock first so it slides in a straight line rather than swapping ends.

I love it when the car spins around when I make a panic stop and got on the brakes just a little to much, LOL.

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I forgot about the physic involved.. Your right pad area doesn't matter. What does matter is the radius of the disc. The longer radius is a torque arm over the wheel.

To quote stoptech (and not only because my buddy has been working for them since we were in the UCLA Mechanical engineering program together)

an excerpt from

http://stoptech.com/tech_info/The%20Physics%20of%20Braking%20Systems.pdf

and

http://stoptech.com/tech_info/formulas%20_vehicle_braking_dynamics.pdf

1. Torque created by the caliper on the rotor (at the wheel) = TW

TW = PS x AP x μ x 2 x RE

PS = Pressure of system; AP = Total Area of pistons in one half of caliper (one side of

opposed type or active (piston) side of sliding or floater type); μ = Friction Coefficient; x 2, since

there are two sides of the rotor that the pads are exerting force against;

RE = Effective Radius of clamping force.

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That's backwards, you want the front to lock first so it slides in a straight line rather than swapping ends.

I love it when the car spins around when I make a panic stop and got on the brakes just a little to much, LOL.

Lulz, yeah that's true. To note, after thinking about it, you do lose a bit of braking if the rears lock first since your fronts do 65-70% of the braking and you won't be able to maximize that if the rears lock first. Though on my street car I'd still rather have my rears lock up just before hand, I'm much more comfortable with over-steer than understeer. Anything autoX or track absolutely have the fronts lock first. See, no one's perfect ;)

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