Is there a limit to safe downhill speed on a bike I have a very steep hill on my route which levels out after about 2 km. The first quarter is extremely steep and shortly after I enter it the bike skips around a little bit and by the time I'm at the bottom I'm gripping the handle bars and working pretty hard to keep it under control.

Is this a normal issue or is it indicative of problems with the bike? It happens both with my mountain bike and the touring bike. Less on the 29'er mountain bike perhaps due to the wider tyres and less twitchy handling.

There is a lot of acceleration right from the start going down.

Clarification:- I'm not concerned with other people's safety or traffic, my question is more about at what speed does my bike become unhandleable and/or fall to pieces.
The maximum safe speed is the speed where you still have control you think is needed.

There are levels of control


Can you stop if a car suddenly reverses out of a driveway?
This is the highest level of control; it means we'd never exceed about 25kph (16mph) on the flat. Obviously we frequently exceed that, and so we're trusting that such intrusions into our "road space" will not occur on this ride.
Can you swerve to avoid a small child or animal that suddenly runs onto the road?
Since such intruders are notoriously unpredictable, we also need to brake and swerve. If I know there are kids / dogs on the loose, I slow down to that 25kph level, or slower. But if it's reasonably open road I figure it's reasonably safe to clock 40kph (25mph). I've encountered oncoming cars in my lane as I round a bend on a descent at this speed, and there's plenty of time to evaluate my options, brake, and take evasive action (time flows really slowly in such cases).
If the road is really clear, i.e. you can see well to the sides, and a long way in front.
In this case we can easily do 60kph (35mph). Around this point (and faster) some rider / bike combinations can experience shaking, which can be quite frightening. You need to experiment a bit to learn what's going on. In many cases resting your knee against the frame seems to dampen the shakes. In other cases I've had success relaxing my grip on the handlebars - this seems to suggest that it was my fear of death grip on the bars causing the wobbles :-)
Ok the road is clear, and you're feeling lucky. How fast can you go?
If we keep going faster, it seems we pass the zone where the speed wobbles occur. If you are not a pro (being paid to do it), and are not confident, or are just a sensible person don't do it. However, I can confess to cracking 120kph (70mph) on a descent on a road bike. I found that as I went faster the bike became more stable, I'm guessing from the gyroscopic effect of the wheels. The same effect seemed to make turns more difficult. The first time I also found it was extremely hard to see properly, since I wasn't wearing any eye protection. And it took over 400 meters to stop on the flat. We can be sure that if any of the above mentioned road intrusions occurred then I would have been toast.


After all that, given the pictures you've posted, I would recommend at top speed of 30 to 40kph (16 to 25mph), because it looks like a residential area. Even that may be too fast, especially because of the incline, which means your center of gravity is higher and so you have less braking capacity.