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YACT: Brakes - sorta technical

DingDingDao

DingDingDao

Diamond Member
So my brakes are about to buy the farm, so for the fourth time in the life of my car I'm going to replace the rotors and the pads. Since I need to do this anyways, I'm looking to do a upgrade that won't break the bank. I have an Audi A4, by the way.

Option 1: A8 rotor upgrade. This increases the rotor size from 288mm to 312mm, while still using the stock caliper.

Option 2: An aftermarket company is offering a similar upgrade, using a floating 332mm rotor that uses the stock caliper as well. Quality isn't an issue here -- the rotors are manufactured by Zimmerman, a German OEM supplier.

The pros and cons of each option:

Option 1 Pros: Parts are readily available from Audi and OEM suppliers.
Option 1 Cons: The A8 rotor is 20mm smaller in diameter than Option 2.

Option 2 Pros: Larger rotor size increases swept area, reducing fade the most and increasing stopping strength. Also, replacement rotor rings are cheaper than a whole A8 disc.
Option 2 Cons: If the aftermarket company goes under, I'm SOL when I need to replace the rotor rings again.

Prices for both kits are within $50 of each other, so the price isn't that big an issue.

What do you guys think? Also, solid/slotted/cross-drilled or a combo?
 
Yeah, no problem. I have 18" wheels. However, I'm using one of my stock 16" wheels as a spare. The A8 upgrade will fit under the 16" stock wheels, but the 332mm rotor upgrade won't, so if I get a flat in the front, I'd have to switch a rear wheel to the front and use the stock wheel in the rear (which would be a huge PITA to do, especially on the side of the road).
 
Originally posted by: DingDingDao
So my brakes are about to buy the farm, so for the fourth time in the life of my car I'm going to replace the rotors and the pads. Since I need to do this anyways, I'm looking to do a upgrade that won't break the bank. I have an Audi A4, by the way.

Option 1: A8 rotor upgrade. This increases the rotor size from 288mm to 312mm, while still using the stock caliper.

Option 2: An aftermarket company is offering a similar upgrade, using a floating 332mm rotor that uses the stock caliper as well. Quality isn't an issue here -- the rotors are manufactured by Zimmerman, a German OEM supplier.

The pros and cons of each option:

Option 1 Pros: Parts are readily available from Audi and OEM suppliers.
Option 1 Cons: The A8 rotor is 20mm smaller in diameter than Option 2.

Option 2 Pros: Larger rotor size increases swept area, reducing fade the most and increasing stopping strength. Also, replacement rotor rings are cheaper than a whole A8 disc.
Option 2 Cons: If the aftermarket company goes under, I'm SOL when I need to replace the rotor rings again.

Prices for both kits are within $50 of each other, so the price isn't that big an issue.

What do you guys think? Also, solid/slotted/cross-drilled or a combo?
Click to expand...


I'd go with the a8 upgrade, you won't have problems with the ABS sensors ( if you have a FWD). Plus your spare prolly won't fit with the aftermarket kit.

Honestly theres no point in getting uber stopping power if you're not gonna track the car. A8 brakes will do.

EDIT:

actually N/M, all a8s are quattro which means they got ABS sensors pointed at the CV joints. Either way go with the a8 if you 're doing it yourself. Bleeding the brakes is a bitch and theres enough opportunity to fvck up as is. I crushed my rear ABS sensor when changing wheelbearing on my b5 quattro.
 
From what I gather, this uses the stock caliper but uses a bracket to move it out from the hub, correct? Why kind of improvement are you looking for? What is wrong with the regular brakes.
 
I don't see how having larger rotors is going to have a drastic effect. You're still using the same caliper with the same brake pads, so the contact area of the pad and rotor is still the same. You might get marginally better heat disappation, but that's about it. If you want more performance, you'll have to upgrade the caliper as well.
 
Originally posted by: nwfsnake
Don't get drilled for the street, they will just crack. Go for the upgrade that fits the spare.
Click to expand...
Drilled or slotted is lame and only useful for bling factor. As are your 18" wheels, BTW. 😉

If you get the rotors that don't fit the spare, you will just have to do two wheel changes if you get a flat in the front. How often do you get a flat, anyway? I'd go for the best braking.
 
Originally posted by: ItTheCow
I don't see how having larger rotors is going to have a drastic effect. You're still using the same caliper with the same brake pads, so the contact area of the pad and rotor is still the same. You might get marginally better heat disappation, but that's about it. If you want more performance, you'll have to upgrade the caliper as well.
Click to expand...

The increased distance from the hub gives the caliper more leverage. It should make some difference.
 
Originally posted by: mchammer
Originally posted by: ItTheCow
I don't see how having larger rotors is going to have a drastic effect. You're still using the same caliper with the same brake pads, so the contact area of the pad and rotor is still the same. You might get marginally better heat disappation, but that's about it. If you want more performance, you'll have to upgrade the caliper as well.
Click to expand...

The increased distance from the hub gives the caliper more leverage. It should make some difference.
Click to expand...

+ the distance travelled on the outside (per revolution) is greater, which means the area sweap per revolution is more. More SA -> more friction -> more stopping force
 
Unless there is a HUGE performance difference between the two (Which I doubt) I would go with the option that will allow you to use your spare without a problem.
 
very little difference between bigger rotors, calipers are still the same size, they do the braking. virtually no difference between drilled and slotted in street applications.

just get OEM rotors and be done with it.
 
Originally posted by: huesmann
Originally posted by: nwfsnake
Don't get drilled for the street, they will just crack. Go for the upgrade that fits the spare.
Click to expand...
Drilled or slotted is lame and only useful for bling factor. As are your 18" wheels, BTW. 😉

If you get the rotors that don't fit the spare, you will just have to do two wheel changes if you get a flat in the front. How often do you get a flat, anyway? I'd go for the best braking.
Click to expand...

How are my 18" wheels only useful for bling?

a) Going to 18" from stock 16" increases the stiffness of the sidewall (due to the low profile of the tires). This reduces roll, improving cornering.

b) The stock 16" wheel for my A4 weighs 20.6 lb. I have 18" x 8" SSR Competition wheels, which (due to semi-solid forging) weigh only 15.0 lb. This reduces the unsprung weight on the car by 5.6 lb per corner, 22.4 lb for the car, and due to the fact that it's unsprung weight translates to a savings of 89.6 lb total. Reduction of overall weight improves every characteristic on the car, including acceleration, cornering, braking, etc.

So explain to me again how my 18s are for bling only? 😛
 
Originally posted by: mrchan
very little difference between bigger rotors, calipers are still the same size, they do the braking. virtually no difference between drilled and slotted in street applications.

just get OEM rotors and be done with it.
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That is not true at all. when I warped and blued the stockers I had on my Ram the first time, I upgraded to a 353mm rotor and did not blue them again. But I wanted more stopping power, so next time I went with dimpled and slotted 353mm rotors. Holy crap did my stopping distance change; even more dramatic on subsiquent stops. Total night and day difference. Granted I never measured my stopping distance either before or after, but I would guess that I went from 60-0 in 180 ft before, and about 140 after and it stayed at 140 even when doing it repeatedly. Minimal brake fade on a 8000 truck.
 
Swept area is not increased by either option, as you're using the same calipers with the same pads. There is still some increased stopping power due to the larger diameter of the rotor, but that has to do with how principles of leverage apply to braking.
 
Personally, my take is to go with the second option mainly because of the (correct me if it doesn't) reduced unsprung weight of the 2 piece rotor setup. Reducing the unsprung weight is better for performance driving (yeah yeah it's a generalization) and helps the suspension do it's job better as well.

I'm going to go out on a limb and say that even if there is no increase in mass or even a slight decrease in total unsprung mass, the fact that it's further out from the center of the hub will probably cancel out any power benefit.

Nebor's right about a non-increase of swept area but rather an increase in brake torque from a different placement of the caliper itself... actually it would apply in both cases. Since it's in the front, you probably won't have an issue with a change in the brake bias... then again, some people do encounter too much front bias causing the fronts to lock way before the rears do, but that's safer than the rears locking first anywho.

Personally, I like slotted rotors mainly for looks (slotted usually come plated while solids do not) and I still don't trust crossdrilled since I've seen many cars with them have cracking.
 
Floating rotor? Wtf, i have floating calipers on my car but thats the first time i've heard of a floating rotor.
Stick with solid rotors, x-drilled and slotted are just for show.
 
I'm thinking about the same thing on my father's C5 A6, it currently has the 288mm rotor setup.

I want the either continue with 288mm rotors and HAWK HPS pads all around, or upgrade the front with the 312mm rotors and the TT front brake caliper carrier brackets. Cheapest place i've found this setup, rotors and brackets is http://www.purems.com its $350 for a pair of solid rotors (ATE or zimmers) and the brackets.

Cheapest place to get hawk HPS pads i've found is http://www.performancepeddler.com/default.asp though i'd use hawk's website for correct part numbers. I believe the B5 A4 takes HB269F.763 for front, and HB364F.642 for rear.

New 288mm solid rotors would only be about $40 ea. I'm debating if this small upgrade is worth it; if i could find the TT brackets used at pick-n-pull for under $100 for the pair, i'd do it in a heartbeat; those brackets cost quite a bit.
 
Originally posted by: Nebor
Swept area is not increased by either option, as you're using the same calipers with the same pads. There is still some increased stopping power due to the larger diameter of the rotor, but that has to do with how principles of leverage apply to braking.
Click to expand...

Swept area is increased, due to greater circumference.

Of course, if the A4 pads leave a significant portion of the braking surface unswept near the center, it's a kind of half-assed upgrade. (I'm not saying that it is, I'm just saying that it could be, depending on the difference in dimensions of the A4 vs. the A8 pads.)
 
Originally posted by: Thegonagle
Originally posted by: Nebor
Swept area is not increased by either option, as you're using the same calipers with the same pads. There is still some increased stopping power due to the larger diameter of the rotor, but that has to do with how principles of leverage apply to braking.
Click to expand...

Swept area is increased, due to greater circumference.

Of course, if the A4 pads leave a significant portion of the braking surface unswept near the center, it's a kind of half-assed upgrade. (I'm not saying that it is, I'm just saying that it could be, depending on the difference in dimensions of the A4 vs. the A8 pads.)
Click to expand...

The pads for the 288mm rotors are the same dimensions as the pads for the 312mm rotors, as far as my searching has shown.

There are variations for pads in the rear, you can get them in 15mm thickness or regular thickness, which is about twice as thick.
 
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