Decathlon B-Twin brand : 1st place I look for bike components

Decathlon (UK) is a shop I now look at first for bike components. The usual choices for brake and drivetrain components etc are Shimano and Sram and seem to have a decades long duopoly.

Recently I noticed Decathlon have bike components using their B-Twin branding. I trust this shop and they have a casual returns policy, and they also tend to offer quality products as their own brand at much cheaper prices than alternatives.

So currently they are my first point of reference when looking for anything to do with cycling including clothes

There are only a few stores in the UK. They have the same type of store presence as IKEA.

Decathlon UK Cycling dept

Items I have bought

7/8 speed 11-34 tooth rear derailleur : £7.99
to replace Shimano

V-brake pads 

Derailleur hanger / dropout replacement : A checklist

Example of a hanger

Bicycle Derailleur Hanger replacement
Replacing a hanger can be a nightmare.
What are the 'rules' when replacing one ?

Here is my 'naive' list for when having to replace your hanger.
My knowledge : 3/10

Is there a universal/generic hanger ?	No. Your hanger will likely be specific to your frame
do the bike makers make spare hangers ?	It seems most don't. CNC machine companies sell copies on Ebay/Amazon etc.
How do I identify my hanger ?	If you know the bike make and model and year. But in the end it seems theVISUAL comparison is the most important bit. It has to look very like a copy on a CNC list of hangers
Are the generic hangers in shops any use ?	Probably only as a 'get me home' hanger, if that. It probably will fit badlyif at all
How many hanger types are there ?	100+ ?
Where should I buy ?	Probably Ebay from a CNC comapny. Check their photo list or send them an email. You could send them a photo of your hanger to help
Try the bike maker ?	You could try
Hanger bolt	If you still have your old hanger bolt you can use that. If not, you'd be best buying the bolt too. This will be an option by Ebay sellers
Price	Expect maybe around £7/$15 without bolt ? Add another £1/$1 for bolt

Shimano Rear Derailleur cage sizes SS GS SGS

Shimano rear derailleur cage sizes (reference)

Short - SS

Medium - GS

Long - SGS

My (naive) understanding.

When buying a rear derailleur (Shimano code RD)
Also keep in mind the cage length
In general short cage (SS) will have a short looking cage and long a long lookingcage
My understanding is that longer cages can deal with bigger teeth gears (front and/or back)

Examples :
A short cage (SS) probably won't cope with a 34 teeth big gear on a rear cassette. Maybe best for 26t rear max (?)
A long cage will likely cope with a 34 teeth rear cassette

Keep in mind to take into account the size of your front gears
It's about how much chain the rear cage can deal with from both the front and rear gear sizes. 

Road bikes often seem to have a 'smaller' 1st rear gear (e.g. 26 teeth) and SS cages are often for them (probably the point is that SS will be quicker for changing gear)
MTB's often have a 32 or 34 teeth rear 1st gear (big looking) and will probably need a GS or SGS (can deal with bigger teeth on rear or front)

My current status on this subject : pretty unsure but I have a 34t rear cassette so going for SGS to be safe. Awaiting more wisdom.

Shimano FD-R443 front derailleur : a quick look

Shimano DR-R443 front derailleur for triple front rings
For road bikes with a flatbar
This one is compatible with 7-8 speeds. I think the newer version also fits 9 speed.
For double front rings you would choose the FD-R440

This is the front derailleur on my commuter bike. It seems to be specifically for road bikes with a flatbar. I guess intended to be used for a road-bike chainset with mountain bike shifters. Maybe the indexing is specifically set.

Good quality. I have seen some shops list it as a Tiagra component, but my research does not confirm this. Looks more like a component from no group.

Weight : mine is 105g