P Line - Upgrading the gears 4-12.

[TC99]

I'm suffering trying to cycle up steep hills on my P Line. I am going to be frugal for a month or two and am spending several hundred quid getting the gears upgraded to 12. Brilliant Bikes are doing the work.

I know I will have two gear changer controls. Seems a bit Heath Robinson to me but needs must. Anyone else had this mod done?

 

[CaptainWheezy]

I did it myself, upgraded my T-Line from 4 to 12, pretty straightforward using parts from Brilliant Bikes!

 

[TC99]

I did it myself, upgraded my T-Line from 4 to 12, pretty straightforward using parts from Brilliant Bikes!

They quoted me for the parts and said they would fit them free. I like that. Getting them to service it too.

How have you found the upgrade?

 

[T4tomo]

You could just change the chainring for a smaller one at a fairly insignificant cost, and keep it as a lighter 4 speed, but lower geared than current

 

[CaptainWheezy]

How have you found the upgrade?

Much more usable than the standard 4 speed. I used it shortly afterwards on a holiday in Mallorca where I did some pretty big hills no problem!

 

[Fastpedaller]

It's also possible to fit an additional chainring and front derailleur which will keep it a bit lighter.

 

[TC99]

You could just change the chainring for a smaller one at a fairly insignificant cost, and keep it as a lighter 4 speed, but lower geared than current

If I was just using it for city riding then this would be it for me.

 

[tinywheels]

I had brilliant bikes fit a chainring plus a few more parts to enable me to get up the East Sussex hills. I still can't get up most of them. However the lower gearing is great for commuting in town.
At a guess 12 gears is the way to go.
Not sure about the faffing about with 12 Brompton gears though, 6 is a pain in the arse.
About time Brompton got round to fitting allfine to all relevant models. Are you listening Brompton!

 

[CaptainWheezy]

Just for reference, I also fitted a 44 tooth chainring (not so straightforward on a T-Line as it also required a spider adapter from BikeGang in Taiwan and a special tool to remove & refit it to the cranks), so I've got the best of both worlds. Would be much easier on a P-Line as its just a chainring swap.

 

[T4tomo]

Standard Brompton are generally too high geared, they seem to think everyone is using them on the flat in towns cities. They use to let you choose what sized chainring it came with, but now you have to change it yourself after purchase I think.

There is a chart somewhere in this forum that shows the Standard 4 gear gear inches vs the old standard 3 speed, and the 4 speed sits significantly higher.

Retro fitting 4 -> 12 speed is a very expensive way to do it. getting low gears with a chain ring swap is more sensible. if wider range is needed a non standard double chain ring and FD is both cheaper and lighter. plenty of you-tube "how you do it " guides.

 

[Kell]

There is a chart somewhere in this forum that shows the Standard 4 gear gear inches vs the old standard 3 speed, and the 4 speed sits significantly higher.

It's in the OP's other thread.

https://www.cyclechat.net/threads/taking-my-p-line-to-6-gears.298104/#post-7222242

But whoever made that graph didn't really do a great job of comparing like-with-like.

The three speed was calculated using a 44T chainring, but the 4-speed with the 54T and 56T.

I did compile a graph myself using a gear calculator and the same size chainring - it was when I was weighing up the possibility of a G-Line (no one was quite sure what the gearing was at that time and I still don't actually know) and how it compared to my current 6-speed set-up.



Brompton Gear ranges by Kell, on Flickr

 

[Kell]

Or you could watch this...


View: https://www.youtube.com/watch?v=Ojk7z5o7l0k

 

[T4tomo]

But whoever made that graph did the three speed with 44T chainring, but the 4-speed with the 54T.

The standard 4 speed is a 54T chairing - thetas why is so highly geared. the standard 3 speed (A-LINE) is 44T

 

[Kell]

The standard 4 speed is a 54T chairing - thetas why is so highly geared. the standard 3 speed (A-LINE) is 44T

But they're all interchangeable. So it's still not comparing like with like. If you want to know how the gearing ratios actually compare, it doesn't give you the correct info and tells you half a story.

 

[T4tomo]

If you want to know how the gearing ratios actually compare, it doesn't give you the correct info and tells you half a story.

I don't. The OP might.

I was merely pointing out:
1) a smaller chainring might achieve his aims for the fraction of the cost of new back end / wheel on his bike.
2) I'm not sure your chart covers the standard current brompton offerings now they no longer offer a choice of chainring as a free cost option as they use to back in the day. It may be the gear inches are correct but the labels wrong, I dont know.