Technical FAQ: Freehub noise and brake stiffness

This week, Lennard Zinn addresses questions about limiting freehub noise, brake stiffness, and using hand pumps.

Freehub noise

Dear Lennard,
I’ve recently purchased a new set of wheels which have a loud freehub. I believe I can add some grease to the pawls to dampen the sound, however I have three questions:

1. Would adding too much grease clog the hubs and slow the wheels down?

2. Which is the best grease to use?

3. How do I know how much to use?
— Peter

Dear Peter,
In general, you have to be careful with using grease in a freehub. It can really suck if your pawls stick down and don’t lock up the freehub; it’s a good way not to make forward progress if your freehub is freewheeling when pedaling. It’s also a good way to crash if you stand up coming out of a corner expecting your freehub to lock up and it doesn’t.

In the case of your particular freehub, which is a pretty standard, Campagnolo-style design (except that yours has multiple teeth on the end of each pawl, which may account for the noise), you may be able to get away with putting some grease in there, if you’re careful. If you do this, make sure you only use a small amount and that you grease ONLY the teeth on each pawl. DO NOT let grease get under the pawls, and do not grease the pawl hinges; this can stick the pawls down. Use oil under the pawls and on the pawl hinges.
— Lennard

Disc brakes vs. Rim brakes

Dear Lennard,
I’m a fairly big rider at 6-foot-6 and 253 pounds. I spent 15 years riding mountain bikes before a knee injury opened me to the joy of road riding. I think given my MTB past, I’m pretty soft on wheels and don’t break spokes, but I do get a fair bit of rub and flex — especially when I give a short (all I can do) squirt up an incline. My question is, are disc-brake wheels inherently stiffer than rim-brake wheels? I’m contemplating a new bike and would like more info.
— Robert

Dear Robert,
No, disc-brake road wheels are not inherently stiffer than rim-brake wheels, other than that they have more spokes.

Yes, the rear hub axle is 5mm longer on the disc-brake wheel, which allows the spokes on the drive side to be set outward 2.5mm further, making for an improved bracing angle to the rim. That could make the rear wheel slightly stiffer. The non-drive-side spokes generally are more vertical (less favorable bracing angle, although they are under lower tension anyway) than those on a rim-brake wheel; this is because, even though the end of the hub is 2.5mm longer, the spoke flange is further inboard to make room for the rotor.

The front disc hub’s non-drive-side flange is further inboard, to make room for the rotor, so that spoke-bracing angle is less ideal than on a rim-brake wheel. [related title=”More Technical FAQ” align=”right” tag=”Technical-FAQ”]

In order to counteract the braking torque applied to the rotor, a disc-brake wheel generally will have more spokes and they will be laced in a crossing pattern (usually three-cross). A rim-brake wheel’s spokes will often be radial, making them shorter than on a disc brake, which improves the spoke-bracing angle and stiffens the wheel.

So, all in all, I would guess that the stiffness of one vs. the other is completely dependent on the rim and comparing them would not be apples to apples, since it is rare to build a disc-brake wheel with a rim appropriate for rim brakes.
― Lennard

Using hand/frame pumps

Dear Lennard,
What is the secret to getting good inflation on my road bike tire with a hand/frame pump?

I have a good day if I get it to 60-65 psi! Tire capacity is 120 but I ride with 90-100, and would like to get it to 75-80 with the hand/frame pump after a flat. 60 is rideable but I worry about pinch flats.
— Tom

Dear Tom,
The key is having a frame pump with a thin enough cylinder. Keep in mind that the force you can apply to the pump handle is much less on a hand pump than on a floor pump.

Pressure is equal to force per unit area, which can be measured in pounds per square inch. The pressure you can apply with a given force increases if the area over which it is applied decreases. In the case of a bike pump, the pounds of force you can apply is higher the smaller the square inches of the piston are — in other words, the smaller the diameter of the piston and cylinder, the higher the pressure you can generate on the column of air going into the tire. Of course, this comes at the expense of the volume of air you can pump. It takes more strokes to get a given amount of air into the tire with a skinnier pump of the same length as a fatter one, but you can ultimately get more air into the tire with it.

So, the key is to have a skinny hand pump; don’t bring a mountain-bike hand pump along with you on your road bike. And you can pump your tire after a flat most efficiently with a long, skinny hand pump — provided you have a place to fit it on your bike; then you can get both higher pressure and fewer strokes as well.
― Lennard

Follow-up to flying with disc brakes

Dear Lennard,
In a post entitled “Flying with discs” last fall, Brad noted that he was eager to travel with his new disc-brake-equipped bike, but faced the dilemma of not having a bike box large enough to accommodate the bike without removing the fork. The problem is that the fork cannot be removed because the disc brake hose is routed within the fork, and that requires disconnecting the hydraulic hose and then reconnecting it (with bleeding, I presume) at his destination. I believe I have a simple solution to this problem and wonder whether you can test it out (since I do not own a disc-brake equipped bike) and tell us whether it works.

To be able to remove the fork without disconnecting any hoses or cables, my solution is to add some extra length to the hose (by replacing it with a longer one) and loop it in front of the bike’s head tube in a manner that would be very similar to the curve one sees in front of the head badge on an ordinary caliper brake set up, but in a circle or two. The extra length of hose could be held in place by a few zip ties, or even some kind of plastic retainer that could be designed for this purpose. To remove the fork, undo the cable ties to extend the hose so that the fork can drop through the head tube when the pinch bolts and top cap on the stem are released. Once the fork is released from the head tube, it can be tied up along the top tube or down tube and secured with padded protection. When reassembling the bike, one merely coils the hose and secures it in place with zip ties. I think a relatively small diameter loop could provide enough extra hose to accommodate this extension, have no effect on braking (since it is hydraulic) and be relatively costless.
— Marc

Dear Marc,
I think that’s a very interesting idea, and it should work fine. While not everybody would like the aesthetics of extra loops of hose in front of their head tube, those who want to travel with a minimum amount of hassle with a bike with hydraulic disc brakes might feel that it’s an easy tradeoff to make.
― Lennard