Avid BB-7 Disk Brake Adjustments

A shot of a road version of the BB-7 Avid mechanical disk brake - his example is nice and clean, rather than using an image of mine ~

Even this very detailed description and advice does not cover the problem I had with BB-7 brake set up that neither the bike store that sold me the bike with these brakes nor mechanics at my LBS were able to identify.

I bought a Traitor Ruben in the summer of 2009. I generally ride it to commute to work when the weather looks like rain or is otherwise crummy - otherwise I ride a more pleasant (in my view) road bike. One of the main advantages (if not the main advantage) is that in rain the mechanical disk brakes, Avid BB-7s, have no noticable drop-off in performance that you have with rim brakes. The problem can be that adjusting these brakes to perform reasonably whether raining or not can take some effort.

The many-step process described by the blogger above leaves out the problem I was eventually able to correct that seriously lowered the BB-7s' performance for me. The problem I had stemmed from incorrect setup by the store that sold the bike to me. (Or perhaps by the company that produced it, I suppose.)


Two disk brake pads not yet mounted in their spring are at left, two mounted in spring (they look like a tiny waffle iron) are at right.

In order to operate properly, the brake pads, pressed together with their spring into a kind of brake pad-sandwich, need to be inserted fully into the caliper slot. Each pad has two small "ears" that are supposed to fit into a metal clip that is inserted into the caliper from the opposite side from where the brake pads slide in. As it turns out, this clip is quite strong and getting the pad "ears" to fully engage with the clip takes a bit of force - and if you convince yourself that they are fully seated (it isn't readily apparent whether they are or not by visual inspection) then the brake pads don't lay flat against the pistons but instead are sort of balanced on top of two pins that are in the middle of each of the pistons. When the pads click into the clip properly the pin on the piston will seat in a slot in the back of each pad and hold them in the right place. (Yes, hold them in the right place in addition to the clips - the clips that seem to work more to keep them out of the right place.)

What this means is that instead of having the pads solidly pressing against the pistons on each side, they are wobbling around, made parallel to the disk only by the tiny spring that is intended simply to push them apart. It is possible for an otherwise sensible bike mechanic to perform the usual setup process and miss that the pads aren't fully inserted. When the pad aren't sitting fully against the pistons, the pads wear at a highly accelerated rate and the performance is poor, although it isn't so poor as to indicate the serious problem you actually have in this situation.


Here you can see the slot where the clip inserts, just to the left of the red adjustment dial that is visible

My simple solution that Avid would doubtlessly not like was simply to take the clips out and insert the pads fully so they were in the right place and mounted on the pistons properly, and leave it at that. The little posts on the pistons are inserted into slots in the back of the pads and keep them in place just fine, it seems. I did try to insert the clips after the pads were in the right place, but that didn't work, so I just left them off. I had a BB-7 on a bike (just on the front fork) that I gave away that was an older model (before this "mtn" and "rd" distinction appeared) and I don't think it even had this clip, so I decided that I couldn't see any reason why if the pads were properly inserted that the clip was necessary. With the pads fully inserted it has been much easier to adjust the brakes to achieve decent performance (and pad wear). I have been riding like this for 500 miles or so, no problem.

So, how did I discover that I had this problem that mechanics didn't see? I had a separate problem with the rear wheel of this bike and had it rebuilt when several spokes blew (described in this post) so I had my LBS that rebuild the wheel and when they put it back on the bike the guy neglected to tighten the skewer enough and silly me didn't check his work so I was riding in a downpour and the rear wheel popped out, yanking the brake bads and spring out. (Luckily I did not fall, although I was mighty surprised.) When I looked closely at the wear on this set of pads, I realized something other than simple adjustment was wrong. I bought new pads for front and back and realized upon more thoughtful examination that the front pads weren't fully inserted (and presumed this had been the problem with the rear one as well). Geez!

I guess the sense that disk brakes are a little more complicated to adjust masked the more serious problem since I assumed that the bike store had set the things up properly in the first place. At one point, tired of making constant adjustments, I stopped at the other good LBS and a mechanic performed his version of the setup but while it seemed OK for a while, it was back to poor performance in a day or so. Anyway, I guess I learned something - perhaps even several things.

In addition to my disappointment with professional bike mechanics in this (which isn't really that great; this isn't brain surgery) I think the Avid instructions supplied are part of the problem - they are pretty poor. The Avid PDF manual (that is the same as what is delivered with the brakes) states that pads should "click" into place but the critical importance of seating the pads in the clip isn't mentioned specifically as the necessary requirement. The two pages have the same information in nine languages, so the degree of clarity in any particular language is proportionally reduced. The steps to take are described, but not much "why this step is important" sort of info.

Bike Parking in Defiance of Signage

Bike parked, locked to railing where it isn't supposed to be (or perhaps it's OK)

In a previous post I described this not-very-friendly sign's placement in front of the Adams Building of the Library of Congress in Washington DC. The sign is on a post that isn't bolted down, so it sort of wanders around this area. The apparent goal is to keep bikes from being locked to the railing and blocking the ramp for disabled persons, but the sign isn't clearly associated with that ramp and to put the sign on the ramp would block the ramp!

Where this bike is locked, then, isn't a problem. But the sign would suggest it is.

Maxim Gun Equipped Bicycles (1896)

Part of an article about a bicycle show in Washington DC - the article is in the Washington D.C. "Morning Times, March 26, 1896 issue.

Another novelty is the duplex wheel [that is, bicycle - with side-by-side seating], with the Maxim rapid-firing gun mounted upon it. It carries two riders, one to propel the machine and the other to work the gun. It is understood that a proposition has been made to the representatives of the Cuban government to equip a regiment of their soldiers with these machines, it being shown that with proper handling they would prove awful and effective engines of destruction.

Unfortunately no illustration of this bicycle was included and I have had no luck finding one elsewhere. The machine-gun equipped bike didn't seem to prosper as a tool of war.

The Woman Cyclist - 1896 Article

Ad for "bicycle suit" for women cyclists, 1896

Text from an article in the Washington DC Morning Times, June 7, 1896.

THE WOMAN CYCLIST.
She Reigns Supreme This Season. Some Timely Suggestions for Her.

The woman cyclist reigns this season. The number of women who have taken to the wheel shows an increase of 75 percent, and the makers of machines for women can scarcely keep pace with their orders.

In the selection of a machine most women who are making their debut as riders this reason need reliable wholesome advice, and if any points of value are secured from this article its purpose will have been fulfilled.

So far as the costume is concerned, knickers are very largely worn in Europe, especially in Paris, but in America they are the exception more than the rule, and therefore this is addressed to ladies who will ride in skirts.

The question of weight in connection with ladies' machines has recently received more attention at the hands of manufacturers than ever before, and the consequence is reliable machines may now be purchased, fitted with brake, mud guards, dress-guard, and gear-case at just about thirty pounds in weight.

In selecting a machine a lady should see that the handle bars and saddle can be so adjusted as to enable her to sit perfectly upright, for nothing looks much worse than to see a lady adopting what is known as the "scorcher" attitude.

Large makers build machines in more than one size, and exceptionally short and exceptionally tall ladies should have machines built higher and lower respectively in the frames than standard patterns.

The pedals should be rubber, and not all steel, the latter with their sharp points being more liable to catch in the rider's dress, pedals to suit the width of foot, can, of course, be selected.

A really first class-machine by a leading firm will cost nearly $lOO, or perhaps a little more, but, of course, very good machines can be purchased for less than that amount.

There are several little things a tider should be particularly careful about, and one of these is the application of the brake. The brakes fitted are usually those which act on the tire, and should consequently not be too suddenly applied, or they will probably tear the tire.

And finally this ~

A lady will find it very convenient to mount from the curb, and will thus be enabled to properly arrange her dress. Sometimes this method of mounting is impossible. A lady will then do well to allow one of the pedals to ascend to its fullest height and descend the merest trifle, and then, placing one foot on the pedal in question, spring into the saddle, the weight of her body on the pedal necessarily causing the machine to go forward. When well going it will only be necessary to slightly raise herself in the saddle, actually standing on the pedals, and the dress will fall as it should. This will be found to be a perfectly easy accomplishment with a little practice.

Full article as PDF is here.

Bikes that Live Outside & Snow

Shogun (and companion bike) in the snow

This 1980s Shogun, which I see often locked up in Shirlington in various places, seems to spend a lot of time outside. It has caught some of this (hopefully) last snow storm, March 27.

Cross Country Cycle Road - 1896 Plan

Map for a cross country bicycle route

Taken from Washington DC Morning Times, June 7, 1896. Reflects some wishful thinking on the future of cycling in the days before automobile owners (and their allies) took over the lead in advocating for funding a good network of roads. The article's author advocates a connected network of "good roads" rather than more expensive macadamized (asphalt) dedicated "bicycle tracks" or "bicycle paths" for long distance bicycle travel.

Some quotes ~

To establish a bicycle track from coast to coast so that wheelmen can journey from New York to San Francisco as easily if not as rapidly as they now do by train. Such tours have been undertaken and partlv carried out. One man would wheel from Salt Lake Cit to Buffalo. Another, at some time, would start at Chicago and wheel to the Pacific Coast. But they seldom wanted to take the trip twice. It was too tiresome. Roads were too bad. Too many mountain paths had to be climbed, too many prairies tortured through. But I am looking into the matter so as to do away with all this.

What has hampered us more than anything in this cross country project are the wheeling [cycling] enthusiasts. These gentlemen insist upon bicycle paths and so we get nothing. A macadamized bicycle path costs in a rocky locality $15,000 per mile. Now make this same locality and use tho road that is already in it by merely improving it and the cost will not be $3,000. You can make a mile or very bad road into very good road for that sum. That is what I mean by intelligent wheeling legislation.

"Across the country in eighty days will be the wheelman's attraction a few years hence. Now it looks funny, but that is what Jules Verne's idea or "Round the World In Eighty Days" did to people years ago. Now we can belt the sphere in seventy days."

Full text of article available most readably here.

108 Links, Half Inch of Stretch (Full Link)

New chain and old chain match up for while, more or less

On the left is a new SRAM chain for my Traitor Ruben, on the right is the original SRAM chain after (?) 3,000 miles (I guess). Turns out the original chain is the 1030model, which is the least expensive 10 speed chain they have (and stretches the fastest, it seems). Since my "good" road bike has a Shimano CN-6600 10 speed chain that hasn't stretched yet, after more like 5,000 miles, I was quite surprised to realize (a) that this was a cheap chain, and (b) that it has stretched a lot.


Over the full length of the chain, full link worth of stretch

The chain has 108 links (one half inch per link, when installed - total of 54 inches) plus a "power link" to hook the ends together. After however many miles I have gone, the chain is now one full link (one half inch) longer overall. Should have replaced it a while ago! To slow down this problem, I bought a better grade of SRAM ten speed chain to replace it.

It isn't the chain plates that stretch, of course, but the pins inside that bend. I don't think this caused the cogs or rings significant damage. Hmm . . .