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84

It's to ensure that young boys who ride BMX bikes will be able to have children when they grow up. Fine print: More accurately, it’s to assuage the worries of the parents that are buying the BMX for their young male child that they might not have grandchildren. Actually efficacy for such purpose is under debate.


75

Cables: The main difference that I am aware of is the diameter of the cable. Most brake cables are 1.5 or 1.6mm in diameter. Most shift cables are 1.1 or 1.2mm, galvanized shifter cables are 1.3mm. I'm sure that there is a lot of science behind the difference but I'll leave that to someone else. One major difference in MTB vs road BRAKE cable is the ...


59

It's to give the illusion of safety.


57

This appears to be a disc brake spacer (block). Such a spacer may be inserted in the disc brake caliper between the brake pads. When the wheels are removed, and hence the brake rotor, an inadvertent pull on the brake lever might move the pistons* so that the rotor cannot be inserted any more. It is even conceivable that the pistons might be dislodged ...


34

Economics of scale. For instance, when a bike manufacturer buys thousands of groupsets directly from a component manufacturer, they get a significantly better per unit price than a retailer can. The retailer not only must necessarily buy in lower volume, but also typically buys through one or more layers of middlemen, each layer adding their cut to the ...


23

It appears to be a clamp-on pump peg that got moved down out of the way either intentionally or from coming loose.


21

Generally it's absolutely fine to buy a relatively new bike, and not worry about component availability. Bicycles are not like cars that have specific components for each model, or at best some component sharing across a manufacturers models. In general, practically all bicycle components are standardized so that bicycles can be built up (or modified) with ...


18

In addition to economies of scale, you also have to consider the difference in price sensitivity and leverage between a manufacturer and a consumer. If Shimano told Trek that they'd start paying retail prices for their cranks, for example, your next Trek would have SRAM cranks. You can be sure they've negotiated the lowest plausible price, because it's very ...


18

Looks like a derailleur guard It mounts to the rear drop out on the derailleur side. It protects the derailleur from some impact damage. EDIT: 06/19/2021 The comments seem to be running strongly against the need for this device. Many experienced riders see this device as useless, and for their use case this is true. One possible use case: If I had a child ...


17

The stop rings go over the head of the bolt. The grooves on the ring line up with grooves on the bolt head and encourage it to keep from rattling loose. They are simply snapped or pushed over the head of the bolt once it is tightened in place. I suspect that in some country, they may be a requirement for manufacturers. However, I haven't ever actually ...


17

The purpose of such a steering damper is to stop the front wheel from turning when using a (two-leg) kickstand or while pushing the bike. Not much use otherwise.


17

These are to protect your frame from the support bolt on Shimano front derailleurs (I don't know if SRAM have the same). You can see them on page page 7 of this manual.


17

Certain parts of a bicycle are more easily upgradeable than others, while other types of upgrades require special tools, much more money investments or are limited to whatever standards are used in its design. For some parts, the opportunity of an upgrade coincides with the older part being worn out; in other cases, the replacement is not warranted by this ...


16

They're trying to sell you stuff. More expensive stuff (have you looked at 11 speed consumable (chain+cassette) prices vs 10 speed?). I would not bother upgrading. As groups go to higher and higher speeds, the older stuff gets pushed down to lower component levels. So today's 11 speed 105 group will be next year's (or likely a few years later) Tiagra ...


16

You can normally use chains from other legitimate vendors, be it SRAM or KMC or something else. You do not need to use Shimano™® chains only. But no-one can tell you whether your chain is of sufficient quality. Only you can inspect it, measure it and try it. We cannot do that. I am not even 100% convinced it is actually a fake chain, but I will just take is ...


15

The one substitution that will probably give you the most bang for your buck is better tires. High-quality tires roll with much less rolling resistance, have better grip, weigh less, and roll over small imperfections more easily. And if you're riding on tires with knobby treads, but only riding on the road, tires with minimal/no tread will ride much faster ...


15

Providing the 7900 is the same, I’m sure it is but someone more qualified can chip in if it’s different. How did it fall out ? Shimano have a proper tool for removing them. Info from here Fawkes


14

The ball-end wrenches are really handy when there's an obstruction in front of the bolt, since they can be inserted at a slight angle. But since the contact area is smaller, you're slightly more likely to strip the hole. So I would use a regular wrench when possible.


14

Any and every part of a bicycle can be replaced, including the frame. (Many people would probably regard a different frame as a different bicycle though.) You ask whether there are components that 'cannot be upgraded'. I think you are misusing that word. Anything can be upgraded, i.e. replaced with a equivalent but better quality version. I think what you ...


13

Are you sure the upper part has not been sliding down such that we can really take a clue from the distance between the two parts? I suspect that the two parts of the fixture are meant to hold an air pump with the upper part having come down. On modern bikes the fixtures rely on a spring as part of the pump to secure it between the two pegs. It looks like ...


13

Great question! I think the market drives this -- not necessarily just the folding bike market, but the component market. Mountain bikes have been the predominant type of bicycle for the past thirty years. This has meant that every manufacturer has a line for very, very inexpensive mountain bike componentry. If you want to build up a bike on the cheap, ...


13

The main problem is quality, in terms of dimensions and variance. If you think its an 11 speed chain but someone has just repackaged some 10 speed chain, then there will be issues. Likewise, if it were the right chain but didn't pass Quality Control and was rejected because it didn't match the required dimensions, then it could fail quicker, or accelerate ...


12

There are generally two types of dropper seatposts, mechanical (e.g. GravityDropper) and hydraulic (e.g. RockShox Reverb). Mechanical dropper seatposts use a spring to move the seatpost and a bolt to keep it in place. This is a very simple design and there are few things that can break or jam, and the weight is also kept very reasonable since there are few ...


12

There's a couple of things here. First there are the physical properties of the groupsets. As you move up the groupsets, what you're buying into is essentially smoothness and lightness. But for a recreational rider, you'd basically need the groupset to hit a certain minimum level of quality, and anything beyond that would be lost by the rider. And my ...


12

It matters in many ways where you buy the bike from. If you're buying online, then the parts will most likely be the same, although you should be careful to read the specs. Some online (brick and mortar as well) shops will have overstock bikes from previous years and the parts will be different from the current model year. If you buy from a local bike ...


12

I'd wager the two biggest reasons you don't see foot-sized pedals are the increased rotational weight, and the difficulty you would have catching the pedal with your foot before it struck the ground or the front tire. I'm sure someone tried this once and promptly scrapped the idea after the foot-sized pedal struck something. Pedals need to be stiff and ...


12

That is a "chain stay protector" and it is installed in, let us say, a non-traditional way. Typically it would be a couple inches forward of where it is. As the name suggests, the purpose of the pad is to protect the chain stay from wear and damage from the chain, which can hit the stay with a lot of force when riding at high speed over rough terrain.


12

This part is officially called "cable hook" and "cable hook unit" in Shimano docs. See attached image (I won't link it because the PDF is not hosted by Shimano) and this document (page 7).


12

Tl;dr: use 700c or 29" 27x2.125" is very rare. 27x2⅛" would be more likely, and wouldn't quite be the same thing, but for tubes the answer would be the same. Generally though, 27" tyres are narrower than this, up to about 40mm or 1 1/2" Schwalbe says that for 27" tubes you should use 700c, which are very common. The bead seat ...


11

I think this is quite a broad question, so I'll highlight a few parts of the bike: Seatposts/saddles: Probably interchangable Forks: You wouldn't want to swap them, and chances are a beefy mountain fork wouldn't go into a road frame anyway, even if you could get the right headset. Gearing: Road bikes typically have higher gearing than mountain bikes ...


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