2017 Westward Ho! Run

[MikeM.]

We've not heard about the front brake torque arm failure happening for quite some time, makes you wonder just why it happens?

[Janet]

One of our members, Richard, suffered a catostrophic failure of the front brake torque arm, resulting in a broken torque arm, brake plate, cam spindle and fork alloy slider.

IAbout 100 miles away from the Polish IJR site in 2008, I had the bolt between the torsion bar and the brake plate drop out. I was riding Glyn's 1951 M18s at the time. Luckily we were in a town and crawling in a queue of traffic towards some lights. I pulled on the front brake and instantly knew there was something wrong so let go and aimed for two vacant parking spaces at the roadside, pulling up in full control at the kerb edge.

Glyn didn't mention how serious this could have been as I wandered down the street to see if I could find it, working on the theory that it could have only come out since I last applied the brake. I was pleased to see it sitting there waiting for rescue and I was grateful to the lovely man who saw my predicament and stopped to let me run into the traffic to retrieve it. Then we set about refixing it, finally gobbing over it with chemical meetal. This was intended as a bit of temporary resistance because it isn't really structural. Having entertained the customers at the adjacent cafe, we continued on our way amid waves and cheers.

On arriving at the rally site we saw Ludwig's bike, missing the bottom part of a fork leg. If I understand correctly, his bolt had sheared off, the brake plate span round and smashed it while he was doing a considerably faster speed that I had been. That was when I began to feel a bit wobbly, realising what could have happened to me. Sometimes traffic jams are a good thing. To get home I swapped with Gary Corcoran's front wheel as he was travelling by van with his family so wouldn't be needing it for a while, until I could return it.

Glad to hear Richard is OK and hope he's working on embellishing the story in true motorcycling fashion. Nothing less than riding at 80mph when it happened will do.

[clanger9]

We've not heard about the front brake torque arm failure happening for quite some time, makes you wonder just why it happens?

Ouch, that is a very scary incident. Very relieved to hear Richard is OK; torque arm failure is one of the nastiest things that can happen when riding a bike...

There's been some discussion lately on the Ajsmatchless mailing list about this. The verdict seems to be that the cross section of the torque arm is slightly marginal around the brake plate bolt. Under some circumstances, it seems it is possible to exceed the strength of the steel here, especially if there's any corrosion or thinning of the metal. The main issue is that the torque arm material is quite thin, so it doesn't need to lose much thickness to become dangerous. I wonder where it broke?

If you are making a replacement arm, it would probably be better to have a "dog bone" shape here to increase the cross-section area.

[g80csp11]

all the replacement torque arm's are stronger with a larger diameter where the bolt attaches to the brake plate . my advice is buy a new one and don't make one . it's certainly a bolt that I check regularly as Janet says they do sometimes come loose

[clanger9]

That's good advice. Glad to hear the replacement torque arms are stronger.

[Mick D]

Hi

Is there any chance I could see a photo of the failed component? I may be able to give an approximate diagnosis of what has happened.

Regards Mick

[dave16mct]

Sorry he's not on the forum and I won't see him for a while now. I saw the brake plate which was in several parts and the brake cam spindle was broken too, I didn't see the torque arm.
Dave.