Search found 33 matches

by Bugsbunny
12 Jun 2020, 6:57am
Forum: Bikes & Bits – Technical section
Topic: Brompton gear ratios - for climbing
Replies: 19
Views: 1327

Re: Brompton gear ratios - for climbing

Hi all

Here's an update after the upgrade and a couple of weeks riding.

It took an extra trip back to the mechanic to get the FD shifting right. Initially I had troubles with the FD shifting down from the big chain ring. It didn't have enough "movement" to get back into the small ring. Then later on, the gear shifter for the FD had some fault whereby going from small to large it wouldn't hold it in the large ring. But happy to report its now shifting up and down without any troubles. It has on my last ride developed some ever so light rubbing on the chain in the FD cage but that should be easily fixed. I have had no dropped chains. Mine uses the Ultegra 8000 FD (I wanted 105) but no stock. Mechanic said the older 105/Ultegra as more adjustable to suit the Bromptons than the new models.

With the additional cable, there has been zero impact on the fold. I've seen this modification with the switch gear mounted on left and right hand side of the handlebar. Mines on the right.

Folding must be done with the chain in the big ring. Its little tricky when you need to pedal backwards folded - you need to do it very slowly.

Gearing wise its fantastic. In the shortest gear its about as low as is practical else the speed becomes too slow to balance the bike. Going downhill with it back in the big ring it has plenty of range.

Cost justification is subjective. But for the new crankset, new Ultegra FD, installation, 1x cable and switchgear, plus new MKS QR pedals amounted to approx USD$230.

I would recommend it for those wanting much greater range and/or climbing gears.

Bugs
by Bugsbunny
28 May 2020, 10:42am
Forum: Bikes & Bits – Technical section
Topic: Brompton gear ratios - for climbing
Replies: 19
Views: 1327

Re: Brompton gear ratios - for climbing

Just installed. The crank arms are too long to fit the original B folding pedals so swapped for these MKS quick release versions.

So far shifting is not quite a smooth between chain rings as I had hoped but will give it some time.
by Bugsbunny
16 May 2020, 2:06pm
Forum: Bikes & Bits – Technical section
Topic: Brompton gear ratios - for climbing
Replies: 19
Views: 1327

Re: Brompton gear ratios - for climbing

Bugsbunny wrote:Thanks guys.

I’ve put an order down for an FSA 46/30 crankset.

The final gear inches should be around 52.

Edit. My understanding is that it fits the original Brompton bottom bracket so that makes the mod less complicated.

More updates once installed and test ridden.
by Bugsbunny
15 May 2020, 1:56pm
Forum: Bikes & Bits – Technical section
Topic: Brompton gear ratios - for climbing
Replies: 19
Views: 1327

Re: Brompton gear ratios - for climbing

Thanks guys.

I’ve put an order down for an FSA 46/30 crankset.

The final gear inches should be 52.

More updates once installed and test ridden.
by Bugsbunny
20 Apr 2020, 8:51am
Forum: Bikes & Bits – Technical section
Topic: Braking upgrades on Brompton
Replies: 29
Views: 3815

Re: Braking upgrades on Brompton

Brucey wrote:is there some reason why you don't just fit the later version of the brake calipers?

cheers


I would go down this path but I can't find much info on their performance improvement. Are they noticeably better?

I've been impressed with Shimano RB dual pivot calipers so was quietly hoping someone could say they fit on Brommie. :D
by Bugsbunny
20 Apr 2020, 7:38am
Forum: Bikes & Bits – Technical section
Topic: Braking upgrades on Brompton
Replies: 29
Views: 3815

Braking upgrades on Brompton

Hi fellow Bromptoneers,

I have a 2017 model so mine didn't get the upgraded brake calipers from Brompton. Anyone got any suggestions on improving braking performance?

Bugs
by Bugsbunny
20 Apr 2020, 4:18am
Forum: Bikes & Bits – Technical section
Topic: Brompton gear ratios - for climbing
Replies: 19
Views: 1327

Re: Brompton gear ratios - for climbing

hoogerbooger wrote:I agree that gearing is a very personal matter and you would probably be best to rely on your own judgement.

[Thanks for the pictures. I've read about the 3 sprocket conversion, but having already gone down the line of adding a Schlumpf speed drive + a SA SRF5(W) (from Brommie plus) I decided not to go there, although might have done before. (As discussed on this Forum the SRF5(W) is not a reliable way to go hence I'm currently looking at going back to 12 gears on a SA AW....but I may have the same problem Brucie alerts to on keeping rain out at the driver interface with the ballring without the benefit of the chain-guard protecting it......or maybe Bruce is saying the cover used on the old AW & similar vintage hubs is a better seal than that on a BWR. The speed drive provided a rather expensive alternative to a double chainset, which is compact, reliable, but difficult to find a supplier that fits them & requires some nerve and special tools to fit yourself)]


Thanks for your feedback.

Can you tell me a bit about your Schlumpf drive? I've only casually heard bits and pieces about it but would be interested in knowing more. I don't know enough about the pros/cons of each mod, and the comment by Brucey about the weather shield on the hub was news to me. Most of the Brommie shops here just promote the mod but don't share much of the downsides...
by Bugsbunny
14 Apr 2020, 12:10pm
Forum: Bikes & Bits – Technical section
Topic: Brompton gear ratios - for climbing
Replies: 19
Views: 1327

Re: Brompton gear ratios - for climbing

Bugsbunny wrote:
Brucey wrote:do you have a BSR or BWR hub?

Any photos of you current setup?

cheers


Mine should be the BWR hub as it was originally a 6 speed setup. I’ll try take some pics when I get home.
by Bugsbunny
14 Apr 2020, 10:43am
Forum: Bikes & Bits – Technical section
Topic: Brompton gear ratios - for climbing
Replies: 19
Views: 1327

Re: Brompton gear ratios - for climbing

Brucey wrote:do you have a BSR or BWR hub?

Any photos of you current setup?

cheers


Mine should be the BWR hub as it was originally a 6 speed setup. I’ll try take some pics when I get home.
by Bugsbunny
14 Apr 2020, 9:28am
Forum: Bikes & Bits – Technical section
Topic: Brompton gear ratios - for climbing
Replies: 19
Views: 1327

Brompton gear ratios - for climbing

Hi guys

I have a 2017 Brompton which I've modified (gearing wise) as follows:

- Replaced front chain ring to 38T
- Standard Brompton 3 speed hub with 3 speed cassette (19T down to 11T).

I'm thinking of replacing the crankset to either: 50/34T or subcompact 46/30 - but cannot decide between the two.
I'm not concerned much about top speed - but rather gears for climbing as I prefer cadence at ~85+ rpm.

Plugging in the gear ratios I get the following (in meters).

CURRENT SETUP: 38T chain ring mated to 19T cassette = 1.69m.
OPTION 1: 34T chain ring mated to 19T cassette = 1.51m.
OPTION 2: 30T chain ring mated to 19T cassette = 1.33m.

I hv a roadbike with 46/30 crankset mated to a 40T cassette giving a ratio of 1.57m.

If I go with option 1 I get a 11% reduction.
If I go with option 2 I get a 21% reduction.

The % don't make much sense to me. Given that I have a spare 50/34 at home - would that be "enough" or should I spend the extra $ and go for option 2. My aim is to be able to climb steep pitches (16% gradients) and the biggest climb here in Hong Kong 1000m at avg of ~8%.
by Bugsbunny
30 Sep 2018, 4:07am
Forum: Bikes & Bits – Technical section
Topic: Brompton: New gear shifters and brakes
Replies: 9
Views: 2027

Re: Brompton: New gear shifters and brakes

Regarding the “fit” issue raised. It that specific to a handlebar type? I have a S bar.

Secondly. I want to use the T bag but it doesn’t fit the S bar. Will the new controls give added space to hack the T bag on without too much cable interference? (I currently hack on the C bag without too much dramas)
by Bugsbunny
28 Sep 2018, 10:00am
Forum: Bikes & Bits – Technical section
Topic: Brompton: New gear shifters and brakes
Replies: 9
Views: 2027

Brompton: New gear shifters and brakes

Does any one know how much of an improvement are the new (2017 onward) Brompton gearshifters and brakes?
by Bugsbunny
24 Aug 2018, 11:37am
Forum: Bikes & Bits – Technical section
Topic: Tyre And Rim Size Safety Concerns
Replies: 24
Views: 1641

Re: Tyre And Rim Size Safety Concerns

reohn2 wrote:
Bugsbunny wrote:
reohn2 wrote:No it doesn't.
A 19mm internal rim handles a 406x50mm Big Apple with 60psi on our Circe tandem,Childback tandem fitted with Vittoria Rannoneur 559x40's @ 45psi and my Salsa Vaya with Vittoria Voyager Hypers 700x40 @ 45f 65r(as supple and slick as any "road" tyre)no worries.In the past I've run 28,32,35mm slick tyres on 19mm internal width rims,and 28,32 and 35mm slicks on 17mm internal width rims all without any issues at all.


A 19mm internal rim may "handle" and "mount" the tires you mention. Its how it affects the ride. It will no doubt be plusher in a straight line. But if you are a roadie (and I'm not sure of the context of the OP's usage) then hysteresis will result. Get out of the saddle and rock the bike and combined with the much lower tire pressures due to the larger/wider tyre and you will feel it - particularly on the front tire as your weight is shifted forward. Going hard into a corner (e.g. crit racing) and you will feel it. My personal experience is the taller tire gives you less handling feel/control.

That is a trade off - hence my suggestion. I really can't comment in the context of tandem bikes and how they handle/ride.

I'm on record on the forum as descending on twisty bumpy bad tarmac far faster on bigger supple tyres (Vaya/Hypers on 19mm rims) than on any narrower high pressure tyres.
There's bound to be a little more movement of a bigger tyre when out of the saddle putting power down that's a given.
Tyre pressures are directly related to tyre size for load,over inflated tyres leads to bad handling as the tyre bumps over small imperfections instead of conforming to them,and is worse on a wet road.the other extreme underinflated tyres for load lead to tyres distorting too much and bad handling.
I've carried out extensive tests on a good few tyres of differing sizes before reaching my conclusions.I don't race but like to descend fast.
Nothing puts tyres to the test more than fast descending on tandems due to the extra weight,our fast tandem riding is over and our fast tandems sold on due to Mrs R2's disability(hence the need for the electric Circe) but we're no strangers to it.


Interesting. We are riding in very different genres. A tandem with the heavier bike and heavier loading of two riders will mean that you pump your wide tires much more than those same tires on a single rider bike. This will mean less hysteresis. Moreover, your genre of tires I suspect have stiffer side walls than say a typical road tire (e.g. Conti GP4000) which again will affect how they ride and handle. I'm also suspecting wider arcs in your downhill turns on a tandem than for shorter wheel base racing road bikes.

I'm also a mad descender and its precisely my experience with wide tires/narrow rims that leads me to call out caution to it. A tall flexi tire (high profile) does not handle well. I'm a big fan of wide tires - don't get me wrong. I just recommend they be paired up with a wide rim - when in the road biking context.

Thanks for sharing. Its good to learn of your experience.
by Bugsbunny
24 Aug 2018, 9:22am
Forum: Bikes & Bits – Technical section
Topic: Tyre And Rim Size Safety Concerns
Replies: 24
Views: 1641

Re: Tyre And Rim Size Safety Concerns

reohn2 wrote:
Bugsbunny wrote:
reohn2 wrote:Are you sure about that?
I'm currently running 37mm actual width,40mm actual width and 50mm actual width tyres on 19mm internal rims without any problems whatsoever.


My experience is with road bike rims/tires and not MTB rims/tires (which I'm assuming is what your experience refers to).

No it doesn't.
A 19mm internal rim handles a 406x50mm Big Apple with 60psi on our Circe tandem,Childback tandem fitted with Vittoria Rannoneur 559x40's @ 45psi and my Salsa Vaya with Vittoria Voyager Hypers 700x40 @ 45f 65r(as supple and slick as any "road" tyre)no worries.In the past I've run 28,32,35mm slick tyres on 19mm internal width rims,and 28,32 and 35mm slicks on 17mm internal width rims all without any issues at all.


A 19mm internal rim may "handle" and "mount" the tires you mention. Its how it affects the ride. It will no doubt be plusher in a straight line. But if you are a roadie (and I'm not sure of the context of the OP's usage) then hysteresis will result. Get out of the saddle and rock the bike and combined with the much lower tire pressures due to the larger/wider tyre and you will feel it - particularly on the front tire as your weight is shifted forward. Going hard into a corner (e.g. crit racing) and you will feel it. My personal experience is the taller tire gives you less handling feel/control.

That is a trade off - hence my suggestion. I really can't comment in the context of tandem bikes and how they handle/ride.
by Bugsbunny
24 Aug 2018, 8:44am
Forum: Bikes & Bits – Technical section
Topic: Tyre And Rim Size Safety Concerns
Replies: 24
Views: 1641

Re: Tyre And Rim Size Safety Concerns

reohn2 wrote:
Bugsbunny wrote: .......If you are on 19mm rim (assuming internal rim width) then I would suggest a maximum tire width of 25mm.

Are you sure about that?
I'm currently running 37mm actual width,40mm actual width and 50mm actual width tyres on 19mm internal rims without any problems whatsoever.


My experience is with road bike rims/tires and not MTB rims/tires (which I'm assuming is what your experience refers to).