More Wobble Diagnoses

Here are some responses to my previous post on wobble:

1. I'd mention how non-parallel drops will bow a hub axle & 'cone' out the bearing seat(s). I went through a couple hubs before I realized this. -WeedBMX

2. Some bearings just simply have play in them too. I've cured some wobbly hubs with new, higher quality bearings. I've also cured some hubs that are way too tight with once wobbly bearings. Although very very tight, bearing manufacturers also have a tolerance to work with. - Couch of Zodiac Engineering

3. It is very important to distinguish between bearing arrangements that may LOOK similar, but behave in different ways.

With a crank:-

The load acts in a relatively constant direction relative to the OUTER race, so the INNER race "sees" a load which acts radially but at a varying direction.

ie. if you mark a white dot on the inner race of the BB bearing, then when the dot is at the bottom, the load acts to push the axle INTO the dot.
But when the dot is at the top the load acts to pull the axle away from the dot.

So it is important that a crank axle is a fairly close fit inside the bearing to prevent the axle "rolling around" inside the race and causing wear.


With a hub:-

The load acts in a relatively constant direction relative to the INNER race, so the OUTER race "sees" a load which acts radially but at a varying direction.

So with a hub, it is more important that the OUTER race is a good fit in the hub shell and the inner race can be a looser fit on the axle (which helps allow the bearings to align with each other).


There are a number of standard bearing "arrangements" based upon whether load is radially oscillating or constant; and that "fully retain" different races. For the record it is "incorrect" to fully retain all the races. Bearing mountings should allow for differential thermal expansion of different components. - G of G-sport

Warranty Claims

I've had a number of cats come through the bike shop lately with various warranty claims. Some are legitimate (such as a new KHE tire's blown sidewall), while others are completely rider error. In this post I intend to discuss the purpose, scope, and effects of the warranty process...

A Little History

There was once a day when a manufacturing failure would lead to the rider swear off that particular company for life... or until they came out with some far too cool new part. At the same time, the quality of complementary that made its way into the BMX market was marginal. Tolerances were wide open, if specified at all; and materials were often very poor. What this did was leave an opening in the market for some quality.

Enter the high(er) quality manufacturers. Profile Racing began offering tight tolerance machined hubs; Primo introduced their cold forged Powerbite cranks (cold forging offers greater tolerance control than casting or hot forging along with good grain orientation in the outer limits of the structure). These components earned a reputation for being less likely to bend, break, or snap. But how could companies compete with high end, and high dollar, components?

In the late 1990's Odyssey took a turn from mediocre quality, fair variety components, toward a different business model. The idea was to introduce two concurrent and complimentary ideas to their product line: post weld heat treatment for their forks, and a no-questions-asked warranty.

41 Thermal, as they call their heat treatment regimen is designed not only to reduce the heat affected zone inherent in welded components, but also to make the component bend noticeably before breaking. From this, Odyssey forks developed a reputation for being extremely strong, while staying cost, and weight competitive. Even though there have been quite a number of bent components over the years, the easy, and fairly quick warranty process has reduced the amount of negative feedback on their components.

Today, it is quite common for riders to suggest purchasing Odyssey components because of their amazingly lenient warranty process (Nuno even offered to warranty my cracked Polycarbonate Twisted pedals!) Picking up on this, many other manufacturers have eased and streamlined their warranty systems. They have learned that supporting the rider, even to some immediate detriment, can have long term beneficial effects.

Purpose of the Warranty Process

You can ask around and I am sure you will get various responses to this question. My response is from the perspective of a shop manager, rider, and prospective manufacturer. The warranty process should be designed to induce a positive company image in the mind of the rider. What this means is that a component should not fail without due cause (i.e. riding hard will inevitably damage parts, especially when we get into lighter weight components). If a component fails due to manufacturing errors, it should most definitely be covered under warranty. A common example of this is a crack directly on a weld, which indicates contamination in the melt pool, and subsequent weld.

There is another purpose, as the Odyssey example shows: to increase customer base simply because of the streamlined warranty process. Although I do not list this as a primary reason for purchasing a particular component, it is certainly beneficial to the rider; even more so if they are on a budget.

When a claim goes too far

I had a cat come into the shop with corroded nipples on a machine built (pre-built) wheel. He claimed it was a warranty issue because he had never see that happen before. Perhaps unfortunately for him, I had. The corrosion was due to excessive sweating seeping onto the aluminum nipples. The electrolytes in sweat increase the rate of oxidation (and on some materials nitrogenation) of materials. Often these oxides are much more brittle than their parent materials, leading to sudden failure or cracking. The point is manufacturers have no way of knowing, nor a reasonable way of preventing all of the outlying conditions that may lead to failure.

So the next time a part fails on you, ask yourself a few questions:

* How did the component fail (break? bend? where? how much?)?

* What lead to the failure?

* Could it have been a manufacturing issue?

Of course you could send in the product in any case, but if they deny your claim, don't give them a bad wrap if they conclude that it is not a manufacturing issue. If they do deny and you feel it is unjust, post it up on line with the question of whether it is a manufacturing fault.

A closer look at detanglers (Gyros)

Although they have gone a bit out of fashion, I have always found detanglers to be an integral part of my brake setup for two reasons:

1. I NEVER have to unwind my bars/cable(s)
2. Properly setup, the load is distributed over two cables, rather than one. This leads to an increase in stiffness, as well as providing a failsafe in the event that one cable snaps.

On that note, I highly suggest the use of a dual cable setup (either with an Odyssey Modulever, or something like the Dragonfly/Snafu adapter) and brake noodles for the lower bends.

Note: No detangler manufacturer recommends disassembling their units, nor should it be necessary unless you lubricate a bushing detangler. But I find these things fun and throw caution to the wind :)

But this post is about the guts of detanglers, so lets get on to that. The original Gyro (or Oryg) is pretty easy to figure out: 2 pieces of stamped and bent steel with loose-ball bearings. These use no lubrication; actually, they require no lubrication be used. By doing so, debris is able to freely pass through the bearing mechanism without being trapped by lubricants.

Advantages:

• Cheap and easy to manufacture
• Replacements are available at almost all bicycle shops

Disadvantages:

• Flexy
• Can be noisy and not so smooth when debris is present
• Prone to "gyro flop" where the detangler shifts side to side due to uneven cable lengths (which can be adjusted out, but is more difficult than newer detanglers)

Next came the Odyssey GTX sealed bearing detangler(s). The original steel has been discontinued due to much better sales of the lighter GTX-R aluminum version. Both are a good improvement on the above Gyro.

Advantages:

• Sealed to keep things running smooth for a good long while
• Very stiff assembly reduces the incidence of "gyro flop"
• GTX-R (aluminum) is a good bit lighter and available in red and blue anodizing
• Long lasting (I have never worn one out)
• Built in set screws for custom cable setups
• Can be disassembled with a flat head screw driver

Disadvantages:

• Set screws tend to fray cables, deterring many people from using them
• Virtually all cable heads require modification to not hit one another. The main culprit is the seats for the cables were machined shallow to allow for the set screws
• Significantly more expensive than competition
• Difficult to rebuild as balls do not easily hold in the retainer

A response to the GTX by Snafu, and more recently Stolen, is a simple Teflon bushing detangler called the Mobeus (or Satellite).

Advantages:

• Cable heads sit snug and clear one another
• Bushing requires no lubrication
• Lower cost and weight than GTX (though the GTX-R is within 0.2 oz)
• Low profile

Disadvantages:

• When lubed, debris builds up quickly and rapidly degrades performance
• Some people complain of binding when pulling the brakes during a tailwhip
• More prone to "gyro flop" than the GTX, but less than Gyro/Oryg
• Requires snap ring pliers to disassemble