Monthly Archives: June 2013

Brompton inner tubes


As we’ve seen in previous entries nothing in the Brompton universe is straightforward. Inner tubes compatibility are ample proof of this.

If you eventually need to replace them, bear in mind that a regular 16″ children bike tube will not fit. This is the one you are likely to find in a rush in a bike shop and for your surprise too wide. You’ll notice is very tricky when sliding it inside the tyre. These inners will cover ranges between 1.75 to 2.125 inches (45-50mm).

On the other hand, Bromptons are equipped with up to 1.37″ (1 3/8″, 35mm) inches width tyres. Schwalbe makes good quality spares and are the ones I recommend.

Compatible inner tubes suit from 28 to 37 mm width tyres

Compatible inner tubes must suit 28 to 37 mm width tyres

Most of the Brompton compatible tubes fit tyres from 340 to 355 mm bead seat and widths from 28 to 37 mm approximately.

16 inches inner tubes are very light :mrgreen:

16″ inner tubes are small and as a result very light :mrgreen:

Bromtpon Eazy Wheels


Replacing the factory wheels was the first repair that came to my mind when I got the Brompty. Although I did it long ago, I have saved it for last within this saga of Brompton repairs because the result is not satisfactory. I would say work in progress 🙂

Factory rollers vs. Eazy Wheels

Factory rollers vs. Eazy Wheels

By installing the Eazy Wheels you have the added advantage of being able to pull the bicycle along on the ground. Stardard wheels are just simply a shame and won´t work.

I love the idea of the versatility of a Brompton

I love the idea of the versatility of a Brompton

Good, I have no more to carry mine everytime I go walking with it when commuting, I thought. But the reality is that your bike needs also a rear carrier, or Brompton mudguard at least, to support parked mode and wheel it along. Otherwise the Eazy wheels by themselves won´t make any difference. I can’t believe I didn’t figure it out until I put them on. Well, at work I never needed to pull/push the bike around :mrgreen: .

Eazy_wheels_4_close_up

Tyred rollers with industrial bearings can also be fitted to the rear rack

A rubber bung, fitted to the bottom of the seat post, can be used as a brake to prevent unwanted rolling.

Full kit

Eazy Wheels full kit with rubber thingy

My Brompton does not have a rear mudguard that will add the extra wheel for stability, or what it could be even better, a rear rack that comes equipped with two wheels improving the handling when it is half-folded.

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Bikes with no mudguards/rack but Eazy Wheels installed, are as stupid as mine looks in the picture

Not everybody need to enable this function. That is the reason it is offered as an option when placing your order. In that case you will have to pay on top 20 quid for the better quality wheels, and another 50 quid for the pricey mudguards or 100 quid for the Version R of the bike (mudguards & rack).

The installation of the wheels is so straightforward… nothing to say about it. What a drag!

Brompton Y trigger


Throughout Brompton three speed models history the bikes have been equipped with Sturmey Archer or SRAM internal gear hubs (IGH). The one to service has a SRAM 3 speed gear hub combined with a Sachs Torpedo shifter that operates the gears.

Sachs Torpedo and Sram Torpedo

Sram owned Sachs at the end of the 90’s. Components were relabelled (right picture)

After years of use there are no signs of shifting smoothness at all. The main reasons are rusty cables and a tatty Torpedo unit that needs replacement.

Fortunately the better functionality of the original Brompton trigger, and the fact that can be either used with Sturmey Archer or SRAM 3 speed hubs, will ease gear shifting for peanuts (£12.75 plus gear cables).

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Brand new in package. You can reuse the old clamp to fit the new trigger

Sachs Torpedo vs. Brompton Y trigger

IGH control components installed in the bars are very basic as a rule. In the Torpedo’s design the simplicity is carried to an extreme. It looks like an old downtube gear lever but clamped in the handlebar instead. It works in friction, due to the index mechanism is incorporated in the hub. With Sachs Torpedo thumbshifters you will only notice gear changes in your legs because this Sram internal hub gear is very silent unlike Rohloff hubs, for example, that emit a loud click each time you change between gears.

The Y trigger, besides winding the cable, incorporates a design that simulates the ratcheting system of a SIS shifter thanks to a pawl leant against a stepped inner wall. It is different however, as you can tell some play of the lever when you move it slightly back and forth. It reminds me of the Rohloff twister which must be setup with some slack. Now when you rotate the thumb levers you will listen to a reassuring snap noise that confirms the gear has been engaged.

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Brompton control trigger has two operating arms so that it can be reached when is in the farther position.

With regard to how conventional indexed shifters work vs. IGH shifters remember that all internal gear hubs require to fully ease pressure on the pedals when operating the shifters. Geared hubs allow users to change gears if the bicycle is stationary, just ease the pedals slightly backwards and the gear will be selected for when you start off pedaling again.

Sturmey Archer 3 spd. vs. SRAM 3 spd. hubs

Both gear hubs surprisingly look and performance the same.  Let’s see a SRAM unit:

Old fashioned IGH shells always bring to my mind the image of sweet corn cans, don't they?. :mrgreen:

Old fashioned IGH shells always bring to my mind the image of sweet corn cans, don’t they? :mrgreen:

As far as the cable attachment and cable tension are concerned these two hubs have similarities and can receive the same shifter. A new trigger installation will be a straightforward task in both cases. The differences start when the gear cable leaves the specific Brompton cable pulley assembly (CPULA):

Forom the point of view of the user, the pinch bolt and chain rods are the only difference

From the user’s point of view, the pinch bolt and chain rods are the only differences

Sturmey Archer system have a rod that goes screwed in to a barrel (B) with a lockening nut (N) that indicates the final point where rods are connected establishing cable tension. In Sram hubs the threaded rod shown below engages easily by pressing the tab (C) of the plastic adjustor A. SRAM has a more solid system (I’ve seen some snapped Sturmey Archer anchor bolts) but it is missing the tension reference provided by the nut.

The down chain must be completely screwed in before setting connecting the rod and pinching the gear cable to the plastic adjustor

Note that the gear indicator chain must be completely screwed in to the hub before connecting the rod and pinching the gear cable to the plastic adjustor A

Shifter installation

The manual for the Brompton Y trigger can be downloaded here.

I’m not going to explain the entire process. In that case follow the instructions. I want to focus and highlight those features that make Brompton parts universe so particular.

The first surprise (and thankfully the only one) was something as common like a gear cable. I knew 80% of Brompton parts are manufactured solely for its design, but I was not expecting a cable to be a problem. I should have inspected the Torpedo carrier first, the narrow groove hints that the head of the cable is smaller.

Hooked carrier conceals a very small cable end

The double hook conceals a very small cable end

My last hope was looking at the Brompton trigger, but a regular cable did not suit as well.

I stripped the whole trigger unit to show that the goes does not go fully home

I stripped the whole trigger unit to show that the cable does not go fully home

The solution was to grind away the excess of cable end so as to ensure hole fitting:

File the tip squarely or if you prefer finish the cable with just two flat sections.

File the tip squarely or if you prefer finish the cable with just two flat sections.

The original cable for these shifters look like this:

From left to right: conventional gear cable (Jagwire), Campagnolo and small headed Brompton shifter cable

From top to bottom: conventional stainless steel gear cable (Jagwire), Campagnolo and small headed Brompton cable (it’s red!)

You don´t need to disassemble the trigger to proceed with a cable or shifter change. If so it will give you an idea that 10-15 pounds items cannot be complex.

The parts are made of plastic. The splined clamp will allow any angle positioning

Inner parts are made of plastic. The splined clamp will allow any angle positioning

To insert the cable select middle gear and slightly push back the lever as I do with my fingers to make visible the hole.

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Remember that you do not need to remove the top cap of the shifter to pass the cable. And do it with the trigger installed on the bars if you wish.

Once the end of the cable seats in the resting position go back to top gear, where the cable is not pulled.

Trim the housing, introduce the inner cable inside and gently remove the slack from the rear frame pulley assembly.

Unfortunalety ferrules are also specific and none were used. I hope bare cables don´t slide inside the shifter.

Unfortunalety ferrules are also specific and none were used. I hope bare cables don´t slide inside the shifter.

Then attach the cable to the adjustor A in SRAM hubs or anchor bolt in SA mechanisms and cut the cable. Fit a cable crimp to prevent fraying.

To close the system connect the down chain until cable slack is almost removed.

IMG_4615

Feed the grooved end B of the gear indicator chain into the adjustor A until it is just not loose. Observe you are not pulling the indicator chain out of the axle at all.

Don´t go forcing too far when fitting the chain inside the plastic device. The secret in SRAM hubs is to take up the slack of the cable in top gear by pulling it softly leaving 5mm side-to-side movement at D-D (see black and white cable attachment diagrams). In Sturmey Archer hubs the axle nut has a hole to verify gear alignment. In middle trigger position, the chain end should be leveled with the axle. Adjustment is carried out by turning the barrel B to obtain correct setting. Relock the nut N to remember cable fitting. Next time, when you have to take off and reinstall the rear wheel, no tweaks need to be done in the cable tension.

In my bike the cable is just slack in top gear with the Brompton Y trigger. Otherwise the shifter pawl would find the cable taut and difficult to step back along the stepped trigger cage.

Before, when the Torpedo lever was installed, I adverted a tighter cable in third gear.

RIP :)

RIP 🙂

It is rewarding when every trigger click corresponds the hub gears. Job done.

Brompton brake levers and cables replacement


I’m on a roll :mrgreen:. Second repair this week for the old Brommy… and still planning more upgrades.

It’s now time to get sort out the dodgy brakes by replacing levers and set of cables. Don´t be surprised if I tell you old Brompton brake levers have very poor braking power and quality construction. They are made of cheap materials and lack of spring return. Very nasty indeed.

1999 Brompton lever

1999 Brompton lever

Because my budget is low I decided to install a pair of Tektro levers suitable for the actuation ratio of the side-pull calipers that came originally with the setup. They get on well with u-brakes and road type calipers, such us side-pulls, dual-pivots and so on… and not compatible with linear pull brakes.

Cast aluminum Tektro lever. It's not compatible with linear brakes

Cast aluminum Tektro lever. Clamp bore 7/8″ (22.2mm)

These particular levers are found on many reasonably priced BMXs, and because they are small, match perfectly with Brompton tiny bars. Sure not the best choice but they do the job. Better anyway than any brake lever made by Brompton until the new 2013 models were unveiled.

Left: former brake lever Right: 2013 design

Left: former brake lever. Right: 2013 design

There is nothing much to be said about the brake cables. Then again, I decided not to use Brompton spares and go for cheaper inner and outer cables. The original housings are known to be more flexible to accommodate sharp radii when the bike is folded and also more durable. With dry weather the difference should be negligible.

I’m not bothered about getting dual-pivots. Old side-pull brakes still work fine despite superior dual-pivot design. Original Brompton’s calipers are pricey, £65 the brakeset. An alternative would be the Shimano R450 57mm drop calipers. Even tough, I’m really tempted to get new ones. 2013 bikes must brake amazingly with new aluminium brake levers, machined double walled rims, dual pivots and better pad coumpoud.

IMG_4787

Final result

A quick wheel truing and brake pads adjusment brought the service to an end.

Brompton rear frame clip for older models


One of the most frustating things in pre-2007 models is the lack of a mechanism that stops the rear triangle from folding when you lift the bike up.

IMG_4590

Got it from Brilliantbikes.co.uk that delivered overseas some Brompton parts faster than any spanish dealer

In order to update my 1999 Brompton the retro fit kit is needed as it comes with an 8 mm seat clamp bolt. If you are using already a 6mm bolt there is a much cheaper kit for sale without the clamp lever, £9 instead of £23,75

Packaging content

Complete retrofit kit

The installation process consists on two steps.

First you will have to modify the rubber damper discarding the conical buffer disc (aka suspension block bolt) for the one that have a recess to engage the latch lever.

IMG_4598

Suspension block bolt disc to be replaced

IMG_4605

Appearance of the new disc bolt. This time is inserted thru the elastomer from the other side

A plastic shim washer (SW), a stepped nylon washer (C) and a nut (N+BW) is necessary to hold the block (SB) from behind when fitting the new buffer disc bolt (BD) as shown in the picture (Fig. QR10). Grease the bolt not to have funny noises. After installing the bolt make sure the small hole is in the bottom position and thus the two tiny lines marked in the disc facing up.

Follow the steps shown int he picture

Follow the steps shown in the Fig. QR10

Secondly replace and discard the old quick release bolt. Three parts will be assembled inside the seat clamp band (SCB) of the bike in the order and orientation shown in Fig. QR05: a hollow stepped cylinder (S), the metal lever (L) and the spring (T). Assemble the parts sliding them with the quick release in angle.

New seat clamp and parts inside the frame band

New seat clamp and parts inside the frame band

Tighten the seat clamp by using a nut and the required metal tabbed washer (SCW) for M8 bolts. Fig. QR06

IMG_4607

For post-2007 bikes use the existing flat washer instead (M6W).

At this time, the installation is fully functional but not complete. The kit does comes however with an ergonomic black handle (HDL) that protrudes much longer than just the metal lever. Secure it to the lever with the self-tapping screw (STS). Fig. QR 07

IMG_4602

My bike now updated :mrgreen:

And this is it.

For further instructions you will find helpful the video from the official Brompton Channel on Youtube. Hard to find better technical advise and spoken english. Well done.