Jump to content
Sign in to follow this  

I need professional insight on brake heat management. (flattrack)

Recommended Posts

I am racing flat track. Currently if I do more than about ten short laps back to back my brakes will fade completely from dragging. On dirt I can feel them go, on ice we have so much traction that I don't know they're gone until I've done a 180 (and I replace fluid after every fade). I don't have the cash to weight my crank and I've already crammed as much flywheel weight on it as I can fit. I'm using 400 degree race dot4 and a solid galfer wave rotor. I removed the disc guard for airflow and I also have a braided steel line.

 

The expert 750's have brake systems that they can drag until they glow red. Feed me information, please.

Edited by SchafferFinney

Share this post


Link to post
Share on other sites

Cartbon rotors and cermaic pads. They cost money. Do not think you can just make a scoop and solve the problem.

 

Perhaps things have changed since I rode flat track but we never used the brakes (back only, still that way I assume).

 

Try lowering your pedal, perhaps you have your toes touching it? You could put a inline pressure switch, a battery and a LED on the bars to indicate you are on the brake, verifying you are riding it.

Share this post


Link to post
Share on other sites

Rdingslikecrack - Caliper slides fine. I clean and lube the pins probably twice in the life of a set of pads. I've tried most types of race pads including the sport carbon xx or whatever that high end ebc for offroad is. Also, oem is on that list.

 

William1 - I'm dragging the brake on purpose. Carbon rotors are far out of the question for my situation. As far as I know they have a warm up period before they gain feel which is hard to accomplish on a dirt track. On top of that, not every situation calls for riding the brakes as hard as the ice or short track. I have definitely considered an air scoop, though. Lightspeed makes one for $100 I think. I can't find any reliable feedback though because most of it is based off woods/mx. As far as I'm concerned they have more time to cool the brakes between uses.  *edit: As far as I know nobody in flat track runs carbon, either.

 

Bolon - Yes. Flattrackers are really cautious about sharing secrets, something about keeping an advantage? I've gotten answers but nothing as concrete as I need.

 

 

Something I also didn't mention: My rotor is not glazed and I clean my pads fairly often with a wire wheel. I have also verified that the rear wheel isn't cocked by any legitimate amount.

Edited by SchafferFinney

Share this post


Link to post
Share on other sites

A home made scoop out of alloy sheet is a easy thing to create. However, they provide cooling air the instant you move, along with the air, they will gather drit kicked up. They also tend to retain the heat as soon as the bike is stopped and that promotes localized glazing and rotor warpage unless you have a fan or rotate the wheel when off the track and all heated up.

 

You are right about the heat up time for carbon/ceramic or carbon/carbon brakes. They would take a few laps of running and firmly applied to get to operating temps. But they thrive in glowing hot conditions. Brakes are funny in that either they are designed to be super heated all the time or not at all. Therefore, when either type is used in the incorrect scenario, you have lttle brake action.

 

A larger caliper may help the heating issue. It may require a larger master too if the piston size changes. Larger diameter rotors can also work better. My own experience regarding pads is they rarely are 'just the solution'. It is a rotor material AND pad. Most bike rotors these days are stainless and they stink (they get 'slippery' when hot). Cast iron often works better. Customers hate them because of rust.

Share this post


Link to post
Share on other sites

Typical overheated brakes are from = too thin or too small a rotor, incorrect pad material make up, for application, sticking calipers. Or finally moisture in brake fluid causing brake fade.

Now knowing you are intentionally doing this, I say you are using too small a set up.

Try referencing your rotor bolt pattern to maybe see if a dual rotor design is available, of course you will need the rest of system as well.

I've saw guys run rotors on both sides of hub also. Custom made brackets etc. Basically using a off set rotor bracket to clear chain , that bolts behind sprocket, caliper mount also have to be made up, you can plumb a brake line t in place to run two hoses. I bet someone makes oversize kit that will work.

I hope this gives you an idea.

Share this post


Link to post
Share on other sites

Also keep in mind, that ceramics and titanium brakes are usually most heat resistant. That said, they are also harder causing more extreme rotor wear quicker.

The thinner a rotor the hotter it gets, the hotter it is the quicker the pads wear, its a vicious cycle! The bigger the diameter of rotor the more it will cool. You can try having the rotor cross drilled at machine shop.

Share this post


Link to post
Share on other sites

SchafferFinney, did you try asking about this at the Flattrack.com forum? Give it a try. If no luck, find a guy over at that forum named Dale Lineaweaver. He is a Flattrack genius. Not sure how available Dale is right now. He took a fall and has a broken hip, but you can try.

Share this post


Link to post
Share on other sites

After reading your comments I think my problem could easily be the disc being made of 420 stainless. I hadn't considered how little heat an SS rotor can actually absorb before it quits. It would be hard for me to find a foundry to cast me an iron rotor thats actually worth anything, any ideas on the downfall of using M4 instead? Or, a good source for cast iron rotor blanks? If I can get two or three rotors made I no longer care about wear.

 

As far as changing rotor/master cylinder/piston size - no. I'm fairly confident (i'll double check) that some parts of that are actually against the rules. Along with that I really don't want to change the contact feel and feedback of my current system too much. I can manage to sacrifice SOME in the name of durability but not much.

 

Edit: I talked to Dale a few months ago about some engine work and he told me to call back about this time of the year, looks like I'll be giving him that call. Thanks for reminding me!

Edited by SchafferFinney

Share this post


Link to post
Share on other sites

Try giving performance machine a call, they use to and still might supply most of the mags the 750 guys run and alot of the brake hardware. They do Street bike disks but can probably switch to race brakes quickly being a machine shop. If it's any help the old ama street race bikes of the 80's used cast iron disks they were always rusty if they sat to long.

Share this post


Link to post
Share on other sites

I remembered that JM Bayle was a big time brake dragger, especially on his CR500. Looked it up and read that his mechanic made an air scoop setup to blow across the special finned works caliper that Honda made for him. This may not be an option for you.

Any chance of grafting on a rear wheel setup with bigger calipers and rotors from a street bike?

Share this post


Link to post
Share on other sites

3 words, STR caliper cooler .... basically a higher end heatsink most ice / flattrack guys are running some form of one

Share this post


Link to post
Share on other sites

Try running DOT 5.1 brake fluid (not to be confused with DOT 5). DOT 5.1 fluid is compatible with all DOT 4 systems, but both dry and wet boiling points are around 50 degrees F hotter than DOT 4 fluid. You can also peel the layer of insulation from the back side of an old pair of pads and double it up on the new brake pads. Adding a scoop to direct air over the caliper would probably help as well.

 

The problem with fluid coolers are that the brake fluid does not circulate in a system, so while a reservoir with fins would keep the fluid within cooler, the fluid in the caliper closest to the piston can still boil. Once any of the fluid in the system boils your brakes will become spongey.

Edited by KJ790

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×