84
votes
Accepted
What is the foam tube on the top of bmx frame for?
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 ...
- 29.1k
81
votes
What is the difference between brake cables and derailleur cables?
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'...
- 9,189
59
votes
56
votes
Random piece of plastic
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 ...
- 9,610
34
votes
Why is buying a bike as a whole cheaper than buying separate parts and building it?
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.
...
- 29.9k
23
votes
What is this device attached to the seat-tube?
It appears to be a clamp-on pump peg that got moved down out of the way either intentionally or from coming loose.
- 81.8k
21
votes
Is it a good idea to buy second hand bike model that has been discontinued?
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 ...
- 75.5k
20
votes
Accepted
How maintenance-free can a commuter bike be?
The best is probably to look at the so called Dutch bikes - or the bikes offered by subscription services, that are usually designed to lower maintenance requirements and maximise utility - often at ...
- 17.6k
18
votes
Why is buying a bike as a whole cheaper than buying separate parts and building it?
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 ...
- 920
18
votes
Accepted
What are the most basic parts of a bicycle which cannot be upgraded over a period of time?
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 ...
- 14.4k
18
votes
Accepted
What is this U shaped metalic piece with 2 holes?
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 ...
- 20.6k
17
votes
Accepted
What is this spring between the fork and the frame?
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.
- 2,932
17
votes
Accepted
What are these tiny pieces of metal that came with my Giant TCR Advanced 2?
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.
- 5,766
17
votes
Can a counterfeit Shimano chain be used on an authentic Shimano drivetrain?
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 ...
- 16.1k
17
votes
How maintenance-free can a commuter bike be?
The two ‘key’ things for a commuter bike to reduce maintenance are to use an internal gear hub, and to use a belt drive.
An IGH has the distinct advantage of everything being encapsulated in a way ...
- 1,101
16
votes
Accepted
Are Shimano 10 speeds going away?
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 ...
- 46.1k
15
votes
Can a new chain significantly improve the riding experience? If yes - what else can?
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 ...
- 29.2k
15
votes
What are the most basic parts of a bicycle which cannot be upgraded over a period of time?
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 '...
- 75.5k
15
votes
Accepted
What is this stamped metal piece that fell out of a new hydraulic shifter?
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
- 1,098
14
votes
Why are ball socket allen wrenches
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 ...
- 4,272
14
votes
Accepted
Can a counterfeit Shimano chain be used on an authentic Shimano drivetrain?
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 ...
- 121k
14
votes
Accepted
How much faster would I go with a better road bike?
That's really hard to answer. Every year, bike makers come out with claims that this year's model is N% more aerodynamic than last year's, etc. Although they don't always give hard specs on CdA.
Also, ...
- 29.2k
13
votes
Accepted
What is this device attached to the seat-tube?
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 ...
- 1,929
13
votes
Accepted
Why do folding bikes usually have MTB components?
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 ...
- 29.1k
12
votes
Accepted
Why is there a koozie on this bike's chainstay?
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 ...
- 340
12
votes
Accepted
What is the name of this small component inside Shimano Tourney STI
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).
- 5,699
12
votes
What is a substitute inner tube for 27x2.125" tyres (in Prague)?
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"...
- 57.2k
12
votes
Accepted
What is this part that came with my eggbeater pedals?
Without a picture it sounds like the grease port tool
This picture was found in this article on rebuilding eggbeater pedals.
The Crank Brothers Eggbeater pedals, however, require periodic ...
- 20.6k
12
votes
Fuji bolt fell out please help!
The crank appears to be a cottered crank and hence the missing part is a cotter pin. See the article by Sheldon Brown about cottered cranks https://www.sheldonbrown.com/cotters.html
These parts can be ...
- 16.1k
12
votes
Is it okay for my rear derailleur to be as "compressed" as this when in the lowest gear on the bike?
There's no issue with it looking like that while in small-small. It's very normal.
The derailleur's total capacity number defines what large/large combination is supported while still allowing the ...
- 81.8k
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