Dawes Discovery Twin brake modification

How to improve the braking power; or
The five minute project that took all evening!

Last update 25th January 2008

Please click here for the top level page.

Please click here for the cycle index page.

Phil Deaves, Swindon, Wiltshire

Background

Our old Peugeot tandem has a rear hub brake operated by the left lever, and front and rear centre-pull brakes operated by the right lever. This gives excellent stopping power. In contrast, the new Dawes tandem had only a single Vee brake operated by each lever. This proved adequate at stopping the mass of two riders, but was reluctant to cope with the additional mass of a third rider on an Add+bike. When we nearly overshot a few junctions, we decided that "enough is enough", and that we should consider additional braking power.

If you have read the introduction to our bike "family", you will have seen that I have already added a calliper brake to the Add+bike. Every little braking power helps, but the rider is not yet strong enough to pull the lever hard enough. We thus investigated alternative brakes.

The Discovery Twin has a braze-on for a disk brake, so the first thought was to use that. Unfortunately, the carrier mounts are positioned such that the carrier itself covers the disk brake mount. In many circumstances this wouldn't matter as it could be removed, but as the carrier holds the coupling for the Add+bike, we cannot dispense with it!

We took the tandem to Swindon Cycle Superstore, our local bike shop, for advice. A lot of possibilities based around having a disk brake were discussed, and the shop staff offered to do what was necessary to allow for both a disk and the carrier. As can be expected, a disk brake and mechanism are not cheap, and in addition we would need a new hub on which to mount the disk. Because we have tandem-specific wheels, we would need a new rim, too. What price safety?

As it turned out, fortune was on our side. One of the shop assistants noticed a thread on the left of the rear hub, and cast his mind to the Cycling Touring Club journal, which contained an advertisement offering, amongst other things, a drag brake. This item would be adequate for our needs, as we wanted it to operate in addition to the Vee brakes, not instead of them, and there would be no impact on the carrier. Swindon Cycle Superstore referred us to the drag brake supplier, and offered to fit the parts if we wished.

Off we went home, and I called St John's Street Cycles to order the parts. I knew we wanted the Arai drag brake, but wasn't too sure about the quick release kit: was it really necessary? I already had a spare brake lever. Discussion with the assistant left me with the impression that he thought that I was stupid. I mean, of course you need the quick release kit, to get the wheel out quickly (in retrospect, I could have saved Ł30 less a penny, and used a couple of spanners which I carry anyway). The drag brake, I was told, is designed to be used with a lever they can supply for a further Ł30 (again, less one penny). This, it turned out, was a shifter lever. I was really confused: I need a brake lever. Well, I was told, it's so you can turn the brake on and off (can't a brake lever do that?). Anyway, I bowed to pressure and agreed to place an order, whereupon I was put through to another assistant to complete the financial parts of the transaction.

"Hello, what can I sell you?", she greeted me, and promptly tried to sell me a mounting kit. This I definitely did not need, as the Discovery Twin also has a braze-on for this type of brake (I'd already established that at Swindon Cycle Superstore), so I resisted. I won't hurry to use St John's Street Cycles again: I can go to a double glazing salesman for that kind of sales technique! Six days later (there was a Sunday and bank holiday Monday in the waiting time), the parts arrived, and I set about fitting them.

Fitting the parts

To fit the brake, I enlisted my father's help, as he happened to be staying at the time. This, we thought would be a quick, easy evening's work. How wrong we were! The stages were broadly thus:

Lift the tandem into the maintenance stand
This, in itself, was quite difficult, partly because we are both quite slightly built, and also because a tandem is, obviously, about twice as big and as heavy as a conventional single bike.
Remove the rear wheel
Open the quick release lever, use a spanner and an old rag to lift the chain away (don't want to get oily fingers unnecessarily, they may spoil something). The Discovery Twin has chunky, "mountain bike" tyres, and we found that it was much easier to remove the wheel once the air was released. Helpful hint! It is much easier to get a deflated tyre past the Vee brake blocks than an inflated one!
Fit "quick release" arm to brake
Very straightforward, this was simply a matter of undoing one nut, removing the old arm, and attaching the new arm in its place with the same nut.
Screw the outer part of the brake onto the hub
Easy, peasy! This shouldn't take long!
Attach the inner part of the brake
Again, quite straightforward, though it was necessary to remove completely the quick release skewer. There were two nuts on the axle, separated by a washer. Close inspection showed that the washer was exactly at the position required by the inner part of the brake, so we simply removed it and fitted the brake part in its place. So far, everything was satisfactory!
Re-fit the rear wheel
Slightly harder than it might have been, because the carrier closed the frame up very slightly. After trying to open the frame out, squeeze the tyre past the Vee brake, and line the axle up in the right place, we hit a minor snag: we had forgotten to put the skewer back in! That completed, we put the wheel back in its rightful place. Don't forget to re-inflate the wheel.
Attach the frame-mounted part to the frame
To ensure that there is friction in the drag brake, part turns with the wheel, and part is attached to the frame to stop it turning. We hit another snag at this point, because the bolt supplied was not long enough to span the brake's mounting arm, the braze-on, and the gap in between. Fortunately, I had two longer bolts of the same diameter left over from attaching the carrier. I used one now, and was to need the other later...
Determine where the cable goes
The obvious route along a diagonal was taken by a shifter cable, so we decided to run it from the stoker's handle bars (actually, that part had been decided in advance), downwards and under the captain's pedal bearing, then straight backwards under the frame. A quick check showed that sufficient cable had been supplied, so all was well.
Put the shifter/brake lever on the handlebar
This was where the fun really started. First off, it was necessary to remove the handle bar tape. Of course, try as I might, I couldn't remove it without tearing it, so it all went straight into the dustbin, without being reused. It was at this point that we found that the internal diameter of the shifter mount was smaller than the external diameter of the handlebar. We opened out the metal mounting as much as we dared, without snapping it, but the area where the bolt fitted through was still far too small. We resorted to filing away as much metal as necessary. This took hours! I did think that I could give up on the filing, and fit a conventional brake lever, but the stud on the end of the cable was ever-so-slightly too small to grip in the lever. There was nothing for it, then, but to keep filing the shifter in shifts (no pun intended)! Eventually, sufficient metal had been removed to ease the shifter onto the handlebar, and it was time to put the tightening bolt through.
Position the brake lever precisely, and tighten it
The bolt wasn't really long enough to span the gap, and effectively told us so by stripping the threads in the shifter casting. The second of the left-over bolts was used at this point, and it was found that there was enough good thread still in the casting. In fact, this bolt was too long! I thus cut it to a compromise length with a junior hacksaw. Helpful hint! When cutting bolts, always put a nut on it first. Removing the nut after cutting helps make sure that the new end of the thread is good. I remembered to do this, and the new length bolt fitted in position fine. At last!
Fit cables
After all the fuss earlier, this was relatively straightforward. I had enough spare cable outer to run from the shifter lever to the final braze-on that holds the cable outer, whilst letting the cable itself through (I don't know the proper name for this part). The only minor niggle was that, although all the outer was the same colour (black), it was in three bits, so in the interim it is held together with black tape. The joins are both more-or-less invisible. In retrospect, it would have been better to have put some grease (or at the very least, oil) in the cable outer, as there is quite a long pull, meaning that the brake does not always return fully to the "off" position.
Finally
Now, by the light of a torch, I was able to complete the project by putting the adjuster and securing nipple on to the cable and fit it to the brake arm. All that then remained was to take the bike off the stand, and give the new brake a quick test whilst wheeling the bike back to the garage.

In conclusion

There were a number of disappointments arising from this modification:

the aggressive sales pitch from the brake supplier, reinforcing my preference to buy if possible from my local shop
the only instructions supplied were for fitting the "quick release" arm to the drum brake, with no instructions as to how to fit the brake itself. Fortunately, I was able to work it out for myself, but I wonder how many wouldn't have been able to
for a store which seems to pride itself on being able to supply exactly what you want (and more...), it doesn't seem unreasonable to me to expect the store to know that handle bars come in different sizes. I am a relative beginner at this game (particularly with modern kit), and was unaware. Surely they could have asked, and saved a lot of bother
why couldn't brake cable have been supplied to enable the use of a brake lever? Whilst I can see some benefit in being able to latch the brake on, there is also no reason why a "pull-for-on, release-for-off" technique couldn't be used.

That said, I applaud the honesty of Swindon Cycle Superstore for admitting that they are not the best people from whom to buy a drag brake, and not becoming the "middle man" with the associated price mark-up.

This project cost Ł60 for the brake, Ł30 for the lever, and Ł30 for the quick release conversion kit. In hindsight, I could have provided the same extra safety feature for about half the cost, by using a spare brake lever, and using "slow release" techniques (that is, use a spanner to remove the two bolts necessary).

The whole project took about 4 hours to complete. Most of that time was spend filing away the shifter mounting block (for Ł30, we were determined not to waste it!). The only tools necessary were a couple of spanners and an allen key, all of which accompany us on our journeys.

Does it work?

Yes, a resounding yes. The following day, we took the bike (with Add+bike) for a test ride, using a rather round-and-about route to and from the local bike shop for some replacement handlebar tape. We worked up a bit of speed, free-wheeled, and virtually stopped on the drag brake alone. With careful control (usually vocal: "brakes!", "release!"), we are much less at risk of overshooting any junctions.