Originally Posted by
moochems
I would like to restate that I think you are very well informed.
Thanks. I do try to do my own research before asking questions so that I am not asking the most basic of questions.
Mechanical leverage in regards to disc vs rim brakes is as you have stated it. I still feel my cable pull disc brakes far outperform any rim brake I have used. I do have a strong grip. Also, wet roads usually mean wet rims, in my experience rim brakes lose performance in such conditions. With my cable pull disc brakes I have to be careful not to exceed available traction because my brakes seem to work every bit as well in the wet or dry. I wonder how brake fade compares on long descents, I still pulse my brakes to avoid over heating, but my brakes get slightly better with a small increase of temperature. On a really long descent I don't need to worry about overheating the rim and thusly a potential blowout. I don't mean to nit-pick, but like I said, I really like my cable pull disc brakes.
ALL brakes are subject to fade regardless of the type of brake or the vehicle it's on. I get rather confused about the blow-out scenario, it seems to me that the (rubber compound)brake pads would melt and suffer severe fade before they could heat the rim to such a degree that the rim wall would fail. Although, earlier this year I was practicing braking because I was so afraid of locking up the front wheel that I was using the back brakes exclusively and with the weight shift inherent to braking, I couldn't stop very quickly. I had gone over the handlebars in 2002 (or about) from a panic stop. But when that happened, now that I look back, I think it wasn't a wheel lockup that could be replicated on solid ground. I was biking down the road and this really hot girl was jogging and as she passed me I turned my head to check out her.... and during that time I drifted onto the side of the road which was grass (by the time I turned my head back to the road, I was directly in front of a ditch where water was going under the road) and so I think what happened was that the wheel locked and dug into the dirt and THAT is what caused the bike to flip, not slamming on both brakes. In any event, I was practicing using both brakes for better stopping and I had a GPS on the bike on a very clear day and had excellent satellite visibility and I got the bike up to 20mph and did a panic stop and I was able to stop the bike in about 2 bike lengths and the rear did lock up and skid slightly. I reached down and touched the front rim and it was very hot to the touch, maybe 125-130 degrees F. However, on a long downhill descent, I would think that the rubber/synthetic brake pads would liquify (causing a very thin liquid rubber between the pad and the rim) and cause fade. I find it hard to imagine that you could heat a rim to such a high degree that the metal would be compromised to the point of failure. I keep my tires at about 60psi, so that is significant pressure on the rim walls, but has anyone seen this actually happen (rim brakes causing a rim that's in good condition heat the rim to the point of failure and blowout)? I don't know what my rims are made from, they are only slightly magnetic (a magnet sticks to the spokes MUCH stronger than to the rim itself) so I guess they are some combination of aluminum and steel. I could imagine that the rim can get so hot that the inner tube will fail, but not the rim wall.
On long descents, I sit up full straight (when possible) to keep the bike speed down (wind resistance goes up exponentially with speed) let the bike get up to a good speed and then brake for a few seconds, usually the back brakes and it seems to work for me. But I never ride the brakes because I do know that all brakes are subject to fade.
I would think that disc brakes are MORE subject to fade than rim brakes because you need so much more force on disc brakes than rim brakes. You are still converting the same amount of kinetic energy to heat, so I don't for sure if that would be the case.
If you wanted to check out the bikesdirect bikes:
Www.bikesdirect.com
Www.bikeisland.com sells the same bikes but perhaps with a cosmetic flaw or other such "problem" for a reduced price of of course. If you search by size, you can see what they have that fits you. Maybe you like what you see maybe not.
I have NO problem with cosmetic flaws. I live in a very high crime city and so I would see it as a theft deterrent
When I am in center city (where there are a lot of bikes and bike thieves) I always try to lock my bike next to a nicer bike. Also, if I am in a really high crime area, I take the front rim and seat/post with me after I lock up my bike (this is another reason I want to avoid disc brakes).
Bike theft is really something nobody cares about. I saw this youtube video where this guy takes his bike and locks it up and he uses a giant bolt cutter to cut his chain right in front of a police car and pedistrians and puts the bolt cutter across the handle-bars as he drives away and nobody even looks at him. He did his 3 different ways in 3 different locations. He even brought a power grinder to grind down a U-lock and plugged it into the outlet in the traffic light base and nobody said a thing to him (he had a hidden camera recording all this).
Thanks for your advice.
Chris