H: Hubs, Wheels and Tyres Brake Shoes and Linings

[billirwinnz]

Hi David

Those are impressive numbers. From the Porterfield web site it looks like they provide a reline service rather than supplying linings. Do you know if it's possible to buy their lining material so that those of us who live outside the US can use it? I have another couple of old bikes that need better braking. I'd also like to try it on my 600 MV which has pathetically small and ineffective Campagnolo mechanical calliper disk pads.

Keep up the good work!

Bill

 

[davidd]

I am reasonably certain that Porterfield does not supply linings separately. I will ask them directly about foreign customers. One thing that can be tried is for someone in Australia who has a brake reliner is to give them some detailed information and see if they can locate the material by checking with their suppliers. There cannot be many suppliers of friction material with this high spec.

I should mention here that this lining is quite dangerous if you don't have a modified steering stem. I have written many times that if you improve the brakes you will cause yourself a wobble. Unfortunately, David Tompkins did so today in practice. A rider slowed quickly in front of him and he got on both brakes hard. The front end went into a wobble and the rear brake, that had an aluminum torque stay, snapped the torque stay in half. We all want better brakes, but when they work at a very high level you will run into problems that would not happen with low performing brakes.

The good news is that David rode in the race after crashing and got second. His lap times dropped another 5 seconds in the race for a total of 12 seconds better than last year. He had no problems with the brakes or corners.

I will send David a new steering stem on Monday, but I wish it had occurred to me earlier. Frankly, I did not expect the braking performance to increase so dramatically.

David

 

[davidd]

Just to continue with the new shoes, some more tips if you are considering doing this yourself.

I have a 9/16" rod of 6161 that I use to plug the pivot hole prior to machining. I use a 9/16" adjustable reamer to clean the pivot hole out. I pushed mine in, but Pat had two of his split the pivot. I would urge a light fit and I have done some with a slip fit. Frankly, a heavy fit is not necessary. I used Loctite 290.

David

 

[Texas John]

The Ferotec D3920 (UK write-up) says "D3920 Medium high coefficient material with high metal content for medium to heavy duty applications no including oil environments. (Fully cured version is D3921).
http://www.ferotecfriction.com/d3920-uk/

US description is different, and does not mention "High Metal Content"
"Medium to heavy duty flexible material for drum and band brakes, excavator brakes and clutch linings. (D3921 is the fully cured version of D3920)"
http://www.ferotecfriction.com/d3920-us/

Unless USA and UK are different materials, which I would then expect to have different product numbers.
I would think one would want to avoid "Metal Content", whether High or not.

 

[davidd]

I think there has always been metal available in post war brake linings, particularly the higher friction ones. Many of the Ferodo materials that have been supplied for Vincents in the past have had metal in them. The metal in linings help them survive high heat as well as helping distribute the temperature faster through the brake shoes so there are fewer hot spots.

3920 is a popular lining used for many bikes. It often ends up in the rear brakes of racers because it is not the highest friction available, it is a medium high friction and will be less prone to locking up. There are very high friction linings that use modern materials like Kevlar and carbon that are good for 1900 degrees F. I suppose they will give you a warning when your brake shoes melt at 1200 degrees F. But, my point is there are materials much tougher than metal going into brake linings.

I think the real key is how they wear. Many brake reliners will know if a lining is tough or easy on drums. Unfortunately, you can get diverging opinions on the same lining.

Frankly, I am not concerned about the wear on drums. If you are getting a fantastic increase in stopping power and wearing your drums out at twice the rate, that is a winning combination in my book. The fact is owners do not seem to replace their drums due to wear very often and that says a lot. I have replaced car drums and rotors quite a few times in my life.

David

 

[davidd]

Those are impressive numbers. From the Porterfield web site it looks like they provide a reline service rather than supplying linings. Do you know if it's possible to buy their lining material so that those of us who live outside the US can use it? I have another couple of old bikes that need better braking. I'd also like to try it on my 600 MV which has pathetically small and ineffective Campagnolo mechanical calliper disk pads.

Bill,

I think that you may be able to buy material directly from Porterfield. Some was sent to someone in Australia a few weeks ago. RD-4 is the material that we have tested and I think it is an excellent performer. It works well cold, which is a must for the street and its coefficient of friction goes up as it gets hotter.

For the race track I will keep going up in the coefficient of friction, but I am now getting away from the good cold working linings. The next lining I will try has a coefficient of friction at .70 plus, but it needs to be 250 F to start working. I am guessing that this will not be a suitable street compound due to its poor cold performance. The final lining does not start to bite until it is 400 F. I don't think this lining would work for many racers because the warm temperature is so high, but it may be useful to a racer like Phil Canning who is routinely overheating his brakes with the Twin racer.

The biggest obstacle so far has been making the extra shoes to install new linings on. I just finished making a small batch of 8" brake shoes so we can swap out the front shoes on David Tompkin's racer.

For anyone making shoes for themselves, use a carbide cutter for the steel shoe face for the cam. I found them to be hardened steel which is cast into the shoe. I have had several failures of the stock shoe and 8" shoe faces, H48. It is used on both shoes. H48 appears to deform too readily and creates a depression in the metal where the cam pushes. I think that this cannot happen with the EBC shoes, which is a nice feature.

David

 

[nortonrider]

I just relined my shoes with D3920, front and rear. I had considered D3915 and Green Gripper.

These were all I could find for materials to buy.

Interested to hear any long term drum wear characteristics of D3920 since it has been some time there have been any comments about this friction material on here.

The re-liner shops don't really know about wear characteristics.

Also, where do you buy the non-metallic higher co-efficient Kevlar- type material?

 

[billirwinnz]

I fitted Ferotec D3920 to my Prince about 30,000 miles ago (replacing AM4). I've since fitted it to every drum brake bike I've owned with much improved braking hot and cold. I haven't noticed any abnormal drum wear. I didn't take before and after measurements so can't be categorical that it's no more than wear with other linings.

 

[bmetcalf]

Interesting other applications; https://www.ferotecfriction.com/d3920-us.html

 

[Marcus Bowden]

Thank you Bill my handsome I am just about to embark on a load of shoes to be relined.