Jax Rhapsody

I don't think they really need disc brakes, but the disc brakes, and... oppulent...full suspension designs are more for appearance than function. It really wasn't too long ago that hard tails were the step up, then F/S took off, anybody not in the cycling scene walking in to a walmart in 2002 is going to "hafta have" that Next Break Point with the fancy full suspension and front/rear cantis. Seems like a much better alternative than the Roadmaster Granite Peak. Fast foward and the Genesis V2(6/9)00 with front disc brake just seems bad a$$, especially compared to the STILL manufactured Granite Peak... the seemingly only steel frame/steel wheel mtb made today. Really it just has to sell... you know what they say; sex sells. How well they function is quality and rider dependant.
Despite knowing better; I wouldn't mind another Mongoose XR-250, and the V2600 looks pretty good. But that's really the point, not something that functions like it should. I'm not some hate all walmart bikes user here, but I ain't jaded either. I'd advise regular people to stay away from any bike there not a rigid or hardtail.

livedarklions

Any reason to assume that super-cheap mechanical disc brakes are any better or worse than super-cheap rim brakes?

My guess is that no one on this thread really has experienced riding with them enough to make the comparison.

prj71

More importantly...Do disc brakes need consumer grade Walmart bikes?

Kapusta

They do not need disc and for the same price could likely be better bikes without.

Same goes for suspension.

livedarklions

I've assumed that low-end mechanical disc brakes are more expensive than low-end rim brakes, but is that still true?

unterhausen

I am not sure about that. It's quite possible they are about the same.

Kapusta

Because cheap, crappy discs are not really any better than rim brakes, and on a $200 bike, it is a silly place to be spending extra resources. Put the money someplace it actually matters, like wheels that are not disposable, or tires that roll better, or a drivetrain that will stay well adjusted..... but they won’t do that, because those a subtleties that do not register with the average buyer.

cyccommute 

They are slightly more difficult to adjust to work properly than cheap rim brakes. However, when it comes to HelMart bikes there is really no “better or worse”. Every corner that can be cut has been cut to the point where the bikes are actually dangerous to ride.

burnthesheep

I bet they can get the cost of it within pennies, making it irrelevant. Then it boils down to "we make it look like what folks see on the nicer bikes" so they can sell them. Shrug.

Kapusta

With the corners that would need to be cut to make them the same price, I would then rather have the rim brakes. The frame and wheel tolerances needed to get rim brakes working are looser than with disc. With rim, you just need the brake bosses in the general ballpark (both location and being properly aligned). With disc you need the dropouts, caliper mount, rotors, and rotor mounts on the hub to all be within some reasonable spec. Also, while mech disc is not a particularly complicated or refined component, it is a little more so than a v-brake caliper.

Point being that to make them the same price, something has got to give.

Of course, to echo what Cyccommute said, you are really just comparing varying degrees of garbage, here.

rydabent

Brake MFG are switching over to discs, so that is what is more available to bike MFG.

livedarklions

This is probably going to come down to whether it costs more to produce both disc and rim brake frames or just making one kind.

livedarklions

I blame it on the corporate b'crats.

SkinGriz

Funny thing about value. Everyone wants to make a million dollars an hour, spend 2 million an hour, and pay their gardeners, employees, babysitters .01 dollars per hour.

Coworker brought in some sheet metal from I think a 1930’s Chevy truck. On our breaks or downtime he was hammering it straight, tacking here, there, etc.

He commented to me about the quote he got from a professional body guy. Another coworker said “that’s a rip off.” I asked how many hours he thought. Quickly we worked it out the body guy would be charging ~100$/hour.
I commented something like “That’s what I figured it was going to be. Dude- everyone self employed in so cal needs to charge at least that just to keep a decent standard of living.”

smashndash

I have tektro novelas on one of my old bikes. I have ridden bikes with R8000 disc brakes. I ride rim brakes. The tektros are not worth the packaging they come in. Absolute garbage. The difference between modern discs and alloy rim brakes in the dry? meh.

Edit: I started on a walmart bike with V brakes. They were more than adequate.

unterhausen

If you think what's in a cheap disc caliper, there really isn't much there. It's just a lever that pushes on one of the brake pads and the other brake pad is static. Very cheap springs. And the disc is just a stamping. Hubs are a little more complex, but probably cost about the same. The big difference is the frame mounts, that probably costs an extra 50 cents.
Event the big brands can do a mediocre job of disc mount alignment. Granted, a bike shop can fix that and the overworked person that puts them together at walmart is going to have no idea. My understanding is that they are give so little time to assemble a bike that a test ride is definitely out of the question. I can't imagine any of them will line up the brake pads if they were mounted catywumpus.

Even considering all that, I think the biggest risk is probably the pads wearing out.

BlazingPedals

Once upon a time, disc brakes were expensive. That's not so true anymore. disc-capable hubs are about the same cost as non-disc, calipers are calipers, cabling costs are similar... I suspect as disc brakes become cheaper, we'll be seeing more commodity bikes with them.

And yeah, buyers think they look cool, so regardless of performance, they're a selling point.

Kapusta

It is still more complex than a v-brake.

Even the cheapest disc calipers need a way the adjust the inboard pad. Plus, the mechanism that activates the moving side is some sort of ramp and bearing setup. Granted, none of this is very complex in the larger scheme, but compared to v-brakes -which basically just have a bushing for the arm to move on - it is more complex.

And then there is the addition of a rotor.

Further, those really cheap mech calipers that do not have an outboard adjuster are kind of a PITA to set up well.

Look at this another way: look around at what $20 will buy you for a v-brake caliper vs what it gets you for a mech disc caliper plus rotor. Granted a manufacturer will may much less for either of these, but I think it still makes the point about which costs more to produce.

cyccommute 

I disagree. Even cheap disc calipers are relatively complicated compared to a linear brake because of the way that they work. Rim brakes, for the most part, just have to convert a linear pull of a cable to a linear movement of the brake arms. The bearings on the brake can be a simple bushing an offer very good service. A mechanical disc has to convert that linear cable pull into a rotating motion for an actuator to push the pad into the rotor and retract it. Exploded views of the different kinds of brakes show much more complicated mechanisms that require much more engineering and more complicated assembly. These exploded views show how much more complicated mechanical discs are. Most to the parts for a linear brake are bolts and washers.



For the mechanical disc, the engineering is much more complicated.


While I was looking around for pictures I ran across the exploded view for hydraulics. I never realized how simple they are in the caliper. There’s more complication in the lever for hydraulics but they are actually pretty simple.

unterhausen

I don't think a bb7 is a good thing to pick to compare, that's not a particularly cheap brake. The cheaper brakes don't look like that. I'll have to go look by the bike shop and see if they have thrown any cheap brakes out recently.

cyccommute 

The cheaper brakes are usually very similar to the Avid BB5. They often use the same brake pads. It’s slightly simpler than a BB7 but not by much. Here’s an exploded view of that brake. The green arrows point to the bits that make the brake much more complicated than a rim brake. The body also has to cast and machined where cheap linear brakes are often stamped on this level of bike. Disc calipers can certainly be made cheaply but I really doubt that they can be made as cheaply as stamped steel linear brakes.

foothillbilly

I'm a slow-and-easy rider and I don't have a particular need for disc brakes. That said, big-box store bikes have cost me too much by being junk. I'm thrifty enough to see them as a waste of money.

drbarney1

Three years ago I bought a Walmart mountain bike for little over $100 because I liked the spring and shock absorber suspension system. The steel frame has some kind of candy apple green finish resembling green lacquer over chrome and it never scratches the way paint does because it is a harder surface. I conjecture the axles and bearings in the crank and pedals could be inferior soft metal. I make the assumption that frame is the only part of it that is built to last as long as any far more expensive bike but it is not as light; something irrelevant to me because I am not interested in racing. The wheels and tires were questionable, the spoke bolts inside the rims often caused pin hole leaks in the inner tubes in spite of the gasket covering them and the tires wore out in a matter of weeks. I replaced the wheels with mag wheels which eliminated the spokes and problems of spoke nuts because I had no faith a better quality of spoke nuts and gaskets could guarantee the elimination of this problem. I found tires on ebay made in Puerto Rico which I ordered because you can get them in any color you want instead of black. It turns out the neon green tires and probably their other colors last a very long time. After more than two years of steady use the tread looks brand new. I changed the crank assembly and put a new set of disc breaks on the bike. The front wheel already had a disc break but I liked the style of the disc. I put on a new premium brand cassette but kept the derailer because it was made by a reputable company. I also added a lithium battery flasher, and rear lights putting LEDs inside 1959 Cadillac bullet tail lights for a red rear light flanked by two yellow turn signal lights. I had a more comfortable seat which I put on.
I spent under $500 and have a bike unlike anything anyone could buy at any price and it is designed for my needs.
This does not mean I do not admire the beauty and workmanship of high end bikes more suitable for other people.

prj71

fixinbikes

hey let my cheap butt get disc brakes on my wally bike!