Disc brake on tandems

[TheBrick]

Thread dredge I know but this came up in a google search.

I friend was telling me recently that one of the reason disk brakes are common on the rear of sports cars is because they actually offer better heat dissipation than hub brakes. So there dose seem to be to possibility of using a rear disk as a drag brake give a suitably designed calliper and disk. May be a thicker disk would work better and more fins on the disc caliper.

[gilesjuk]

I have ridden hardtail MTBs with disks on the road. I can never get the brakes set up so they don't rub ever so slightly.

£25 for a dial indicator and base on ebay. Check the discs are true and adjust.

Also, Avid brakes have the dished washers for alignment which tend to move around. Other brands are less adjustable but tend to stay put once aligned.

[reohn2]

Thread dredge I know but this came up in a google search.

I friend was telling me recently that one of the reason disk brakes are common on the rear of sports cars is because they actually offer better heat dissipation than hub brakes. So there dose seem to be to possibility of using a rear disk as a drag brake give a suitably designed calliper and disk. May be a thicker disk would work better and more fins on the disc caliper.

Disc/k brakes are OK for short term use ie; bringing speed down quickly or repeated on/off use, but a drag brake needs to be on for minutes sometimes tens of minutes at a time and needs to get rid of the heat hence the fins/flange on an Aria drag brake.Disc/ks can't disspate the heat that well and will overheat and fade.
The problem with tandems is the extra weight and unlike cars theres no engine braking,the only thing to stop them is the brakes themselves and the Aria drag does the job best as a third brake for keeping that extra weight in check and under control whilst using the rim brakes as you would normally.
Santana did a comparison test comparing an Aria with a disc/k as drag brakes,no contest the Aria won handsdown.

[TheBrick]

I know that the drag brake dose, I think you miss understand my post.

I am claiming (though second hand knowledge fro ma motor engineer) that disk brake can provide better head dissipation than hub brakes, and that is one of the reason they are used on HP vehicles. It is mealy the fact that bicycle disks are not designed for tandem use down long hills like a drag brake is. However is perfectly possible to have them beable to cope with being used a drag brake if redesigned properly. Then you could have the advantages of a disk brake and the drag brake without the disadvantages of the hub drag brake system. It seems to be a size of market issue rather than a technical one. Aria is a big lump of metal and I bet if a similar amount of metal was put in to a disk brake you could get better performance.

[reohn2]

........I am claiming (though second hand knowledge fro ma motor engineer) that disk brake can provide better head dissipation than hub brakes, and that is one of the reason they are used on HP vehicles It is mealy the fact that bicycle disks are not designed for tandem use down long hills like a drag brake is. However is perfectly possible to have them be able to cope with being used a drag brake if redesigned properly. Then you could have the advantages of a disk brake and the drag brake without the disadvantages of the hub drag brake system.

I wouldn't know, i'm not an engineer.

It seems to be a size of market issue rather than a technical one.

Could be.

Aria is a big lump of metal and I bet if a similar amount of metal was put in to a disk brake you could get better performance.

Possibly!
If an engineer could put some views forward I'd welcome the input

[horizon]

We use the Arai all the time (if you see what I mean). I don't have an opinion anymore about rims versus discs but I thought this thread was about an Arai versus a disc as a drag brake. What we value about the Arai is that it can be left on, not just for long descents but for lots of shorter, steeper hills when keeping the brakes on is really tiring. It's a huge relief just to know it's there and not holding onto the brake levers for grim death. Although several posts mentioned this, I would just say again that it isn't the braking effectiveness of the disc that is in question but its role as a drag brake.

[zscooby25]

We started off with a Peurgeot tandem with cantilever brakes and a hub brake. Front and rear brakes worked on ONE lever and the hub brake worked on the other.
Braking was almost useless. Two brakes on one lever halved the effect. The hub brake snatched and could not be modulated. After a visit to the hedgerow due to a front tyre blowout on a long descent we decided discs were the way forward and started searching for a suitable steed.
We found it. A Viper Evasion Tandem, a mountain bike but able to take 700c wheels. We fitted my own built 700c wheels with Deore MTB hubs and Hope 203 discs with Hope Mono 6 Ti 6 piston downhill calipers powered by hope mono levers.
Result. Fantastic stopping power. Even fully loaded with front and rear panniers we can stop on a sixpence. Long descents are no problem, Tried it in Tuscany on many long descents with unknown twists and turns.

You don't need to drag a brake if you are sure you can stop when you want to!!!!

Discs on tandems, it's the future believe it. Can you think of any form of wheeled transport which does not use disc brakes for maximum stopping power?

[reohn2]

.......You don't need to drag a brake if you are sure you can stop when you want to!!!!

I disagree,a drag keeps things under control,and although Tuscany is hilly(and beautiful,we love the place ) they're not that long,compared with Alpine descents,where you can be doing 60mph+ in no time at all,a drag is essential for a tandem IMO.
I was chatting to a very prominent TT champion a couple of years back who had a horrendous crash on an alpine descent due to relying on discs alone when they faded after repeated use

Discs on tandems, it's the future believe it. Can you think of any form of wheeled transport which does not use disc brakes for maximum stopping power?

I agree but not for dragging a brake,they simply won't take the heat like an Aria will.

[Si]

We've never needed a drag brake - depends where you ride I guess. In the gently rolling Midlands and the Marches there isn't normally much call for speed control over long descents....also helps if you have the bottle to let it run then hoik on the brakes before the corners, then let it run again. If I were in the Alps though, I'd certainly want a drag brake.

[RJS]

I think Milfred Cubicle has answered his own question, the Arai is the only DRAG brake that can dissipate the heat, (it was intended for a moped I believe), it's just that a suitable disk brake isn't made, there are plenty of disk braked tandems that stop perfectly well, when riding style and/or terrain don't require the brake to be held on for longer periods, there was the Winzip for a short while but I think it did not sell well enough to warrant manufacture. I'm thinking that a motorcycle caliper/rotor could be adapted, with the correct one possibly it may not be any heavier than the Arai, which is of course no longer made.
Dreaming again Cheers, Rob.

[reohn2]

RJS
I bought a spare Aria for £40 when I heard they were ceasing production

[MikewsMITH2]

We started off with a Peurgeot (sic) tandem with cantilever brakes and a hub brake. Front and rear brakes worked on ONE lever and the hub brake worked on the other.
Braking was almost useless. Two brakes on one lever halved the effect. The hub brake snatched and could not be modulated.

The cantilever fitted to the Peugeot tandem, and most other tandems up until recently, are quite adequate if properly set up and good quality brake blocks are used e.g. Koolstops. A change to alloy rims helps wet stopping. The dual brake lever, or 2 into 1 adapter also work well. Some users prefer a separate lever for the drag brake. The original Atom rear drum brake is generally ineffective, but some users report good results. I have never heard of them "snatching" The Atom hub is unreliable anyway (axles bend or break) and I swap them for Sturmey Archer X-RDC hubs, which are very effective. We have fitted many of these to tandems and have had no complaints. We have the Arai on one of our tandems and it is good as a drag brake AND a stopper. SJS list an alternative now which doesn't look as good but it seems well engineered. We have only sold one of these and have had no complaints.

I have a report of a front tyre blowout from overheating in Sussex, let alone the Alps! Thorn have an interesting article on disc brakes, which is just one of the compromises in the design of their tandems due to their adoption of the Rohloff hub gear. http://www.sjscycles.com/thornpdf/Thorn ... oHiRes.pdf

Some info on our website peugeottandem.com

[Brucey]

...I was chatting to a very prominent TT champion a couple of years back who had a horrendous crash on an alpine descent due to relying on discs alone when they faded after repeated use .....

did he say what kind of brakes they were? Hydraulic? Pad type?

BTW I agree that just two brakes (of any kind) is inadequate on a tandem. A drag brake that will take the heat + a pair of something else that will stop you quickly (even if it is just once...) is a workable arrangement. Three brakes is a good idea in any event, since the failure of one brake isn't going to instantly cause an accident.

cheers

[RJS]

MikewsMITH2, we've had a front blowout on our Tandem Twosday, (20" wheels don't help), I normally don't hold the brakes on but this was a steep, twisty, rough, potholed lane, (coming down from Dunkerswell in Devon), another day I mentioned to a friend at the bottom of a hill how hot the rims got, he put a finger on it, soon took it away again with a shout We've got an Arai now, but have never been able to set it up to work as well as I know they can.
Cheers, Rob.

[reohn2]

did he say what kind of brakes they were? Hydraulic? Pad type?

No,but he was very interested in our Aria.

BTW I agree that just two brakes (of any kind) is inadequate on a tandem. A drag brake that will take the heat + a pair of something else that will stop you quickly (even if it is just once...) is a workable arrangement. Three brakes is a good idea in any event, since the failure of one brake isn't going to instantly cause an accident.

cheers

Agreed.

Three brakes with one of those dragable,beats two(even BB7 discs) in certain circumstances,such as long(5miles+)fast descents.
Otherwise the BB7's and 203mm rotors cope very well indeed on anything in the UK.
We have both set ups,so best of both worlds