Flatbar handlebar Common Sizes

This post is about flatbar handlebar common sizes on commuter/urban/flatbar road bikes.

Flatbar or Riser ?
Flatbar is generally pretty straight.
Riser bar is the V-type shape.
For a commuter/flatbar road bike my preference would be flatbar.
So this post is about Flatbars.  

If you have a flatbar handlebar bike.
And want to buy a new flatbar handlebar.
You probably need to work out 2 main dimensions.

The 2 most important specs seem to be :
Stem size.
Width (across)

Flatbar common Stem sizes :
Importance : I think very important (if you can't adjust the fitting for the handle-stem joint.)      

The 2 common flatbar Stem Sizes :
25.4mm (standard)
or 31.8mm (oversized)

There are other sizes but these are the common 2 sizes
Tip :
If your handlebar in the middle looks 'normal sized', it's probably 25.4mm
If your handlebar looks overly big in the middle, it's probably 31.8mm 

Common flatbar widths (across)
Importance : not so important  (?)

Typical flatbar widths :
600mm ?
580 mm would be pretty small.
620mm gives you a bit more space .
The width can go up to 750mm

Note : Riser bars seem to have much wider lengths, such as 750mm
I have read that bars can come big in order to 'saw to size'

Brake types for bikes

Brake Types for Bikes list

brake type	example	take note	retrofit needs
rim	Caliper (most modern ?) V-brake (wire across top) Cantilever (old ?)	weak in wet
disc		strong in wet hydraulic (future standard ?) or mechanical (cheaper)	hub adapter ? (remove spokes ? new wheel ?) fork adapter (fork adapter or new fork with disc fixings ?)
drum/roller/hub	roller is shimano version	niche. needs special hub ? heats too easy ? good in wet ?	need hub on new wheel or remove spokes ? need compatible fork ?

update : none yet

Caliper bike brakes

Above is a table I am using to make sense of brake types for bikes. It could be incorrect. Currently I have 'caliper' rim brakes but thinking of switching the front to either a disc brake or hub brake for more safety. The front brakes seem the most important as I use them about 95% of the time.

Reason for table :
Trying to gather my thoughts as hard to find choices in quick view method. My understanding is 2/10. Will update table when more is known. 

My current brakes : Caliper rim brakes
Thinking of : replacing front with hub or disc.
Brake lever type on my bike : flatbar (MTB brake levers)

Reason for changing :
Rim brakes lose a lot of power in the wet. Disc and roller brakes are not affected by wet. For commuters I think at least the front brakes should be disc (or less likely ... roller).

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 

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.

UK : Boardman Hybrid bike in Cash Converters

I saw a cboardman hybrid bike in a Cash Converters shop. I guess this will rarely happen. The newest version is £499 in Halfords, so assuming it's in decent condition it seems a bargain at £199. Disc brakes.

Halfords UK : Boardman Hybrid Bike 2014

BTWIN Fit 500 Road Bike : An ideal commuter bike ?

About : BTWIN Fit 500 Road Bike
Other names : BTWIN Velo Route Fit 5
Available in : Decathlon only
UK Price : £379.99
This is about the UK version

In the video I believe this bike to be the black bike

BTWIN Fit 500 Road Bike

If I was designing an ideal commuter bike, this would be the sort of bike I would come up with. For me everything is pretty much ideal and I could then add/change a few parts easily. For me an ideal commuter bike is basically a road bike with a flat handlebar and adjustable handlebar stem and lots of comfort (e.g. a big fat saddle), practicality (e.g. a rear mudguard)  and safety features (e.g. lighting etc).

BTWIN bikes seem to be a Decathlon brand, and I have only seen them in a Decathlon store. There is a cheaper 'entry level' bike (the 300 ?) but it looks a bit too wimpy to me. Decathlon seem to market road bikes with flat bars as 'fitness road bikes'. I don't use a pannier etc, so for me a 'fitness road bike' is an ideal base for a commuter bike. I am a bit confused as to the name of this bike as the name in the shop (BTWIN Fit 500) seems to differ from what I believe is the bike on the website (BTWIN Velo Route 5)