How are you cooling your brakes?

#21

If your plate creates a pocket of air near the center of the rotor like ours does you have a relative mass of slower moving air (higher pressure) v/s the outside of the vanes and wheel which has higher speed turbulent air (lower pressure) and air is drawn through the system. The vanes themselves are then somewhat less important.

I actually duct my air through the radiator. This gives the pads some heat all the time since I don’t need a ton of cooling, just some. With proper pads my rotor wear is very good, actually excellent compared to those in the thread. What I’m doing is just knocking out the very high upper temps you see after a long brake zone. I got 8-10 weekends out of my last set of rotors. I changed them because they were wintered outside and had some cracks, they are now spares.

Since I’ve added some weight to the car and the brake life is obviously taking a steep turn downhill, but at 4 weekends right now on the current brakes they are about half worn.

Does it work… Well when I have an off the tubes are always filled with sand or clay or dust so I know they are drawing a good amount of air through and into the rotor.

#22

Internet hiccup killed my well thought-out response. Second effort will be briefer. Do I hear halleluah?

Am hesitant to disagree because unlike me, you know what you are talking about.

I didn’t understand “pocket of air”.

I don’t agree that your design directs air towards the hub. It, the bottom one pictured on first page, seems to me like it directs air at the vanes at the outside perimeter of the rotor.

If you are saying that straight vanes will tend to draw air in from the hub area and expell it from the rotor perimeter, then I agree. But is that what you said? Helical vanes would do it better tho, and they’d be no harder to cast. Well, shit, now that I think about it, the low pressure zone created by the straght vane churning could conceivably move more air then the less turbulent pumping action of helical vanes. Sigh. You never know what product features came from the Engineering dept, and what came from Marketing.

#23

Our plate for the E30 is very small diameter, it’s no bigger than the inside diameter of the friction surface. Due to the spacing needed to affix it, it creates a small pocket in the hub area that wraps around and fits closely to the caliper.

A large portion of what is done with the vanes on some cars is aerodynamic too. There hasn’t been a car that won the Daytona 500 without Performance Friction rotors for many years now. Most of the race rotors do have curved vanes much like M did on thier rotors. I think some of it has to do with how the vanes affect the expansion of the rotor with heat too.

At $60 bucks a set I wouldn’t worry about it too much. You don’t and will never have the option of a good race quality rotor with these cars (either with proper vanes or proper metalurgy). Just make a few improvements that will help you keep the brakes from fading and make them last a few races longer.

#24

To make brakes last longer we could always all opt to drive 318’s! :stuck_out_tongue:

Sasha

#25

robweenerpi wrote:

[quote]Our plate for the E30 is very small diameter, it’s no bigger than the inside diameter of the friction surface. Due to the spacing needed to affix it, it creates a small pocket in the hub area that wraps around and fits closely to the caliper.

[/quote]

I saw some backing plates the other day that were larger then the rotor dia. They looked to me like they would push air into the vanes at the rotor’s outer perimeter. At the time that seemed to make sense, but now that I understand rotor cooling better (thanks to everyone’s patience), that design doesn’t make sense to me.

I thought that those backing plates were BimmerWorld’s. But if you say that your backing plates are no bigger then the inside dia of the friction surface, then they weren’t yours.

For those that may find this thread later…Rob’s point that the Bimmerworld backing plate is small is important. If the backing plate is relatively small, then the 3" duct is likely to be oriented towards the rotor’s hub, where it needs to be. If the backing plate is larger, then the duct could be oriented towards the side of the rotor, or towards the vanes on the outside perimeter. Neither of which are ideal.

#26

I can’t comment on the backing plates shown, but figured I’d share what I ended up trying out. I didn’t want to buy backing plates if I could make something myself that worked for cheap. Worse case senario, it didn’t work and then I would have justification for buying some nice backing plates. I left the factory shield on and cut an ovalized hole as close to the center of the hub as possible. I then used a ducting piece from Home Depot that allows you to adjust the diameter and make a joint (~$3-4 iirc). This piece was then riveted to the backing plate and some ducting hose was attached to that. Some what surprisingly, it works great, I have yet to have any heat issues, pads wear evenly and except for a set of Napa rotors that only lasted a few weekends, my rotor life seems to be slightly longer than average. Is it the best? Probably not, but for only a few bucks and some time, it gets the job done.

#27

sean - I did the same thing - works fine and cheap.
Ed

#28

I suggest strapping two of these on the car

#29

Here is the solution I ultimately went with. I didn’t like how my E30 backing plates directed air flow. They seemed to primarily orient air against the face of the inside rotor. I looked at a couple other designs that seemed to do the same thing. I wanted the air flow to be pointed exactly at the rotor air inlet, and I wanted some stand off distance so the bearing and caliper might get a little air flow. Also, the standoff distance would prevent a high pressure zone forming at the hose opening.

It took a while to figure out how to securely fasten the end of the 3" air hose. The top 1.5" of a Chef Boy R Dee can did the trick.

In support of the fine folks at Bimmerworld, my backing plates were not the ones they sell.

#30

Second picture.

#31

my gut reaction is that most of the airflow will just spill anywhere. The commercial plates attempt to force it into the center of the rotor and a high pressure zone helps - not sure why you think that hurts. Your design may be adequate for our cars though. I have seen brackets to hold hose like this in circle track part catalogs.
cheers,
bruce

#32

leggwork wrote:

[quote]my gut reaction is that most of the airflow will just spill anywhere. The commercial plates attempt to force it into the center of the rotor and a high pressure zone helps - not sure why you think that hurts. Your design may be adequate for our cars though. I have seen brackets to hold hose like this in circle track part catalogs.
cheers,
bruce[/quote]

A high pressure zone at hose outlet would impede air flow thru the hose. The commercial backing plates that I’ve seen don’t look like they try too hard to force air into the rotor air inlet. They are more pointed at the inside rotor face, then the rotor air inlet near the hub.

A high pressure zone at the air inlet would be good up to a point. Once the rotor vanes are pumping as much air as they can, additional air coming thru the hose just builds up into a high pressure zone without much helping airflow thru the rotor much. So a tradeoff occurs between the high pressure zone helping the rotor pump more air, and the high pressure zone preventing more airflow thru the hose. Where the variables of the situation goes from more efficient to less efficient is hard to guess. Fluid flow and heat xfer can be tricky.

I’d submit that if a person wants to get air to the rotor inlet, they at least have to direct air at it. As opposed to directing air flow at the face of the rotor. And if the objective is to create a high pressure zone at the rotor inlet, someone would have to do better then to orient the hose straight at the rotor face AND rotor inlet, and then call it “sealed off”.

#33

James Clay of BimmerWorld told me a few years ago that the best way to decide when to replace a rotor is to run your fingernail across the surface (after the rotor has cooled!).

If it snags on the cracks, toss the rotor.

Carter