Talk to me about Brompton gear upgrades ...

[Messenger88]

In which case I'm guessing you have a 25 tooth rear sprocket; I believe the SA8 can take either 23 or 25 teeth.
If you set the 'rear' value of my calculator to 25, it returns your 33 - 107 range for the SA8 & 50T - which also matches the figures on the Tiller site.

Thanks for all your help.

88

 

[CopperBrompton]

Having had a quick look, that seems about right, so I think you've cracked it. :-)

 

[T4tomo]

So how are you getting on with the SA8? I'd be interested to know.

I have an S3L (I think that's the right code for it) which has the higher choice of gearing 54T chainring as my commute used to be pretty much flat. Now moved house and have a much hillier route. Approx 400ft of vertical rise, either steady gradient over 5 miles or over 2 miles including a little section of 10-12%, depending on which train station I use. I can honk up it out of the saddle in 1st but could do with a lower gear tbh plus the gaps between gears are quite large for the steady but varying incline piece. Always feel like I need gear 2 1/2 or 1 1/2.

I do like the efficiency lightness and reliability of the SA3 though, so If I'm adding 10% to the weight of the bike I don't want to sacrifice efficiency and reliability.

 

[CopperBrompton]

I absolutely love it.

There are two small downsides. First, you need to rotate the pedals a full turn forward before you fold the rear wheel, to tension the chain. If you don't do this, the chain can come off, but once you know about it it's not an issue.

Second, the twist grip effectively loses you half the right handlebar. I'm planning to get an extender so I can fit Ergon grips.

Otherwise, it's perfect. Virtually infinite gears with tiny steps. 1st is low enough for stupid hills, and 8th lets me reach 30mph on steep downhills. Twist-grip is effortless. Lots of fellow Brompton riders on group rides have commented on the fact that I'm able to maintain a constant cadence at all times, and I beat everything away from the lights.

Get one.

 

[Kies]

I have a twist shifter on the Dahon - very easy gear changes

 

[T4tomo]

I'm not a big fan of twist grips to be honest, reminds me of my old raleigh commando ( yep parent too poor to get me a chopper). I have twist grips on a cheapo tandem we have which I occasionally change gear without meaning to.

Explain more what you mean about extenders. I currently have micro bar ends on my S bars ( great for the flat bits off my commuye and or when it gets windy, as it allow you to flex your elbows and get lower / more aeroand moved the brake levers and gear changer in a bit to accommodate them (plus trimmed the foam grips slightly). Is the twisty grip a big intrusion? You are on M bars I think.

Plus do you notice the extra weight of the SA8?

Thanks

 

[Pale Rider]

T4,

Easy - and cheap - enough to put a smaller chain ring on the front.

Or/and you could convert your Brommie to BWR - Brompton Wide Range - 6-speed.

http://www.sjscycles.co.uk/brompton-gear-upgrade-set-3spd-to-6spd-bwr-exccables-prod19449/

 

[CopperBrompton]

It's not much cheaper than the 8-speed conversion, though, which is a lot slicker and gives wider range.

 

[Pale Rider]

It's not much cheaper than the 8-speed conversion, though, which is a lot slicker and gives wider range.

I wondered about that, although I believe the BWR is quite a bit lighter.

The 8-speed twist shift is slicker.

I'm used to my Brommie's six speed, but changing sequentially is a bit cranky.

 

[ufkacbln]

Thanks. From what I can see, that only gives lower gears, so I'd have my three existing ones, plus three lower ones. That would address the bottom end, but not give me the extra top-end I'd like.

There are three versions

Mountain drive: Reduces front ring by a factor of 2.5
Speed drive: increases the front ring by a factor of 1.6
High speed drive, increases the front ring by a factor of 2.5

What you need to do is sort the gearing ti suit your normal riding and then fit the Schlumpf to accommodate the difficult bits.

For instance, I have a 34T front ring on my Gekko which suits me perfectly for city riding (stop and start) however I wanted the third of my riding that I am faster to be more efficient so fitted an HSD to give me an 85T front ring for these times.

Had I been a racer and the majority at high speeds then I could achieve the same withan 85T front ring and a Mountain Drive to reduce the gearing for the occasional hill or trafic interaction

 

[CopperBrompton]

I wondered about that, although I believe the BWR is quite a bit lighter.
The 8-speed twist shift is slicker.
I'm used to my Brommie's six speed, but changing sequentially is a bit cranky.

Yes, it's true the BWR is lighter, but given the speed with which a Brompton accelerates and the fact that I hardly ever carry it any distance (either unfolding and wheeling, or trundling on the EasyWheels), the weight difference is a very small price to pay in my view.

 

[T4tomo]

yes I'm not keen on the non sequential gears on the six speed. so trikeman - are you saying you can't fit bar ends once you have the twistgrip shifter for the SA8? or is it just a case of sliding all the shifter & brake gubbins a little more central on the bars to accomodate

pale rider - switching to 50T whilst helping me out up steepest hill - loses me the top gear for the downhills and flats and I still have big jumps between gears. It is the cheapest option though!

 

[CopperBrompton]

I have twist grips on a cheapo tandem we have which I occasionally change gear without meaning to.

I love twist grips - have them on my trike too. Have never changed gear without meaning to.

Is the twisty grip a big intrusion? You are on M bars I think.

Bar ends are no problem, but to replace the entire grip I need to be able to extend the bar.

Plus do you notice the extra weight of the SA8?

It is heavier, but notice it - no. If I'm walking any further than up/down stairs or across a platform, I either wheel it on the EasyWheels or unfold it and push it. For me, the fold/unfold is so fast I can't understand why anyone chooses to carry it any distance.

 

[CopperBrompton]

so trikeman - are you saying you can't fit bar ends once you have the twistgrip shifter for the SA8?

See above - you can add bar-ends but I want to replace the entire grips with Ergon ones, and that needs a bar extension.

 

[T4tomo]

Ah understood helpful photo too. That would work for me, I only use the foam grips anyway, not expensive leather ones! Plus S bars make sit easier to move the controls inwards to make some extra handroom to accomodate bar ends. Maybe it's just the cheaper Revoshift controller on he tandem that is an issue is you haven't had any problems