Shaving an Arai Drum Brake

[docbluedevil]

Greetings from Colorado!

First post on this forum and appreciate all the great info here.

My wife and I have placed an order for our first tandem, a '04 Co-Motion Speedster Co-Pilot, through Mel at Tandems East. [So far, a great experience with Mel.]

We ordered an Arai drum brake for all of the mountain passes around us as well as for loaded touring. Mel had offered shaving the fins off the Arai brake with a lathe which would shave off about 6 oz. He said it would not affect performance and would cosmetically look good as well.

Anyone have any experience with this? I can see the pros regarding weight. Any cons? Anyone with pics? I've read a reference to this on the forum but have not found any in-depth info about it.

Thanks ahead of time.

Abe.

[Gtscottie]

I am not sure if shaving the drum is such a good idea. The reason for the fins is to dissipate heat outward caused by the friction of the brake shoe against the drum allowing the drum to cool quicker and give you constant braking power. If the fins are gone you may get over heated brakes, which will cause brake fade. I am not sure that 6 oz is that big of a deal unless you are planning on racing.

[TandemGeek]

You can read a typical discussion on the pros and cons of the shaved Arai drum brake by clicking on this link to the Tandem@Hobbes archives. http://search.bikelist.org/query.asp?SearchString=%22RE%3A+Tandems+East+Aria+Shaved+Drum+Exchange%22&SearchPrefix=%40msgsubject&SortBy=MsgDate%5Ba%5D

This is a thread with 25 responses which cover the range of "opinions" and experiences. There is no general consensus and many suggestions that the weight savings are not worth the "potential" problems associated with overheating a shaved Arai. While there are certainly folks who have reported overheating an unmodified Arai -- smoking the drum and/or damaging the bearings in the hub -- conspicuously absent are any first-hand reported failures by folks who actually use the shaved drums. That doesn't necessarily mean failures related to drum shaving haven't happened; it just means no one has felt compelled to share the story if it has... but it is interesting that there aren't any such posts.

Ultimately, it probably comes down to this: If you are a lightweight team who is interested in having a drum brake for piece of mind the shaved drum will probably work fine. If you are a heavy team or a team that knows it's toting an extra 6oz around anyway and will use the drum for loaded touring why bother screwing around with it; it's only 6oz. Personally, I don't think the fins are all that effective as a heat sink but I'm not an engineer nor have I run the numbers; however, I have heard enough from the folks who are engineers and who have run the numbers to think they are of marginal value.

There is one other option for folks sitting on the fence and that is a rear disc. While not intended to be used as a drag brake, the rear disc does alleviate the problems associated with rim heating and is a nice brake option for lightweight, go-fast teams who occasionally find themselves in the mountains on a descent where they become a bit concerned about rim heating. Since the use of discs on tandems is pretty much in beta test mode I have previously recommended that folks consider having their tandems fitted with braze-ons for rim, disc, and drum brakes for the greatest amount of flexibility. I would note that Co-Motion will purposely not set up a tandem so that both a rear rim and disc brake can be used simultaneously to preclude the use of the disc as a "drag brake". I would also note that Mel was not fond of the newer Avid disc brake installations when we last were together at MTR '03.

There you have it. Personal experience? Both of our road tandems are fitted with hardware for disc drag brakes but have never bothered to use them. There have been a few occassions where I wish we had, if only for added piece of mind. We routinely ride with teams who have finned drums, shaved drums, rear disc drag brakes (old Hope models), Avid disc drag brakes, and Avid rear primary brakes. They all work as intended but the constant is that the discs and shaved drums are used by lightweight teams who do not place super-high demands on rear brakes. The heavier teams we ride recognize that they are kidding themselves to think shaving 6oz off of their total team/bike weight is even worth considering.

Here's a photo of a family we often ride with on their Triple from a few years back. It's not a great photo or very large but you can clearly see the shaved Arai on the rear wheel.

[Michel Gagnon]

As far as I know, Tandems East is the only one that offers the shaved drum. I do think the fins help a bit because they increase the surface of the drum in contact with air. The fins are not, however, as well designed as the fins present on some electronic equipment, for instance, so they are not as effective as they could be.

You recall, Mark, the discussion on drum brake failures. I would suggest that the lack of failures amongst shaved drum users is due to a few factors:
- limited number of users;
- the fact hills in the East are steep, but shorter than hills in the West.

The last factor might be one of the most important ones. I think that most "serious" users -- i.e. those that want to do a few West Coast mountain passes via back roads -- will either get a real unshaved Arai drum brake or will adapt their riding style accordingly and stop a few times to cool their brakes.

[docbluedevil]

Thanks for your input!

After reading the large thread, it sounds like the fins are used to help dissipate heat. If that's what they were created for, I'm gonna leave them as is. Plus, shaving the brake will likely void a warranty. I'm not into potentially compromising a vital mechanical system to save some a few ounces, especially with the mountainous terrain in which we live. I've never felt that I was in danger going uphill or on the flats; it's the descents that make me think about my mortality.

6 oz heavier and a ton safer,
Abe

[Joe Voelkel]

Well, let me be the first one to post about over-heating a shaved Arai drum brake.

It happened last summer, on the steepest hills of the Cabot Trail in Nova Scotia. I was riding a Co-Mo Speedster (shaving from Mel, of course, as well as a stoker-controlled lever brake). With my wife and about 35 lbs of rear pannier weight, our total weight sans bike was about 325 lbs.

We had to stop repeatedly to allow the brake to cool down. I'm not sure how hot those babies are supposed to get, but even with the water pouring down (the most beautiful scenery day = the fogged in, rainy, day -- go figure...) the brake was sizzling.

Eventually, an SUV from a group of people who were mixing riding and driving an SUV stopped, put the bike on the rear rack (yes, the tandem stayed safe!) and gave us a ride down the hill.

The same thing happened on the one big downhill on the next day, which was sunny. However, after the trip I took off the brake cover and cleaned the pads up--I have not had any problem with them this year in the Finger Lakes, which offers up some pretty steep hills.

Now, I wouldn't say for sure this was due to the shaving, but I own another tandem with an unshaved Arai, and never had this problem. Mel tells me he has gone down steeper roads with no problem, so maybe it was that particular brake unit. In retrospect, I wished I had put on a new set of brake pads for my rim brakes--they were about 3/4 done. If I were to do it again, I would take the unshaved route--shaving the brake must void the warranty.

[swc7916]

We had to stop repeatedly to allow the brake to cool down.

Why did you find it necessary to stop? Were the brakes fading or something?

[R900]

I like ours, although I want to swap it for a disk:

http://www.weberwoodworking.com/bikes/T20005.jpg

We've had zero problems, but live in Eastern Indiana, some hills, but nothing super long or steep. The brake as worked perfectly, and I do use it. I mainly got it because I was unhappy with the Avid canti's. That has now been fixed on the front with a new fork and a Shimano R600 caliper, I've tried some other rear, and currently run some old XT canti's, better but still not great. I think a disk would give us most of the benefit for the drum (for our region), and improve normal braking. A single disk should also save a fair amount of weight compared to the drum/canti combo.

I'm not as worried about the weight, the shaved drums just look a lot sleeker.

[LWaB]

As far as I know, Tandems East is the only one that offers the shaved drum.


Also Longstaffs in Britain.

[LWaB]

I'm not sure how hot those babies are supposed to get, but even with the water pouring down (the most beautiful scenery day = the fogged in, rainy, day -- go figure...) the brake was sizzling.



Our unshaved Arai gets sizzling hot on the longer hills too. If it isn't starting to fade, I figure it is just doing what it is designed to do, turn kinetic energy in heat.

[Michel Gagnon]

Well, let me be the first one to post about over-heating a shaved Arai drum brake.

It happened last summer, on the steepest hills of the Cabot Trail in Nova Scotia. I was riding a Co-Mo Speedster (shaving from Mel, of course, as well as a stoker-controlled lever brake). With my wife and about 35 lbs of rear pannier weight, our total weight sans bike was about 325 lbs.

We had to stop repeatedly to allow the brake to cool down. I'm not sure how hot those babies are supposed to get, but even with the water pouring down (the most beautiful scenery day = the fogged in, rainy, day -- go figure...) the brake was sizzling.......



How were you using the drum brake ? Were you using it on and off with a brake lever like any other brake or were you applying it all the time to slow you down?

I don't have a shaved brake but nevertheless, I use it like a normal brake, going on and off.

[sch]

Judging from our experience on two tandems and a team weight of 380 or so with bike, any
prolonged braking will result in a LOT of heat. It would behoove owners to hop off the bike
at the bottom of a hill after braking from say 40mph to stop and check the temp of whatever
braking surface you have (except do not touch the disk!!). Our rear rim was too hot to touch
more than a few seconds on several occasions with braking from 35 to zero down a half mile
hill to my house. The rear disk on the new bike gets MUCH hotter. Drums would be intermediate
with the heat distributed over a larger mass, but long descents with drag set can be expected
to get the drum well above boiling point of water. A little experimentation ahead of time is
a good idea to get some appreciation for expected temperature rises.

[merlinextraligh]

IMHO, the only reason you'd want a drum brake is to help reduce overheating from high braking demand.

If you're braking demands aren't enough for heat to be a concern, you don't need a drag brake in the first place.

If your braking demands make heat a concern, I'd want my drum brake to dissipate heat as originally designed.