How safe is her road bicycle at 70 km/h (43 mph)? ?

Question

My partner, Katherine and I have established a close friendship for a few years. The scenario is that she enjoys trying to keep up with my car, while she is on her bicycle.

I was driving downhill on a 6% grade of a 6 kilometres straightaway at a leisurely 70 km/h. As I glanced in my rear-view mirror, I was amazed that she was actually keeping pace with me.

Now, my main concern is rather she was riding at a reasonably safe speed. How safe is her road bicycle at 70 km/h (43 mph)?

Answer 1

Contrary to common belief, a road bicycle is more stable going at higher speeds. Therefore she will be safe as long as she keeps well away from your car, and as long as she wears a decent helmet.  

Answer 2

HI Yin

Kate's road bike should handle quite safely to at least 80 km/h (50mph). Even higher with a little bit of fine tuning. There is of course the ever present danger of potholes, spilt oil, ice (on frosty mornings) and road kill. (I understand opossums are regulars). As long as there aren't too many tight curves she should be fine. It is much harder to avoid an obstacle if she is committed to a line through the bend.

Still probably worth while reminding her about gravel rash and collar bones if she falls. (You get to say "I told you so" if it happens)

It is unlikely she will get much faster than 70 (43) on a 6% grade with her current set up. She would have to be pedalling at something like 130 rpm already.

How has she been when she gets home? Lathered in sweat with her pulse racing?  If she has, give her a break she's been doing some power climbing.

The power climbing will help improve her 1/4 mile sprint time.She needs to work on that 57 sec (was there a head wind?). If she can get her finish speed closer to the 45 km/h (28mph) she has posted previously then her times should be in the low 40's. (about the same as the world record for the best runners.)

Sounds like she is hooked on chasing sports cars and 1/4 mile sprints, I think she is odds on, to start hill climbing as well.

Have fun

P.s. I am a little curious about the use of metric.

Answer 3

Perfectly safe. Road bikes are built to handle higher speeds than this, even, so don't worry about it, as long as she's wearing a helmet!

Answer 4

It's all safe until something goes wrong.    :o)

At those speeds, your body and bike get torn up if you crash, and any number of things can take you down.  Best case scenario is that you only slide out on the pavement and lose a lot of skin.  There are lots of less-than-best-case opportunities, though, and anyone who has crashed much on the mountain or the road knows that helmets really don't do much at all for you other than keep your head intact (which is still important!  lol).   You can be severely injured or die in a high speed crash in just an instant and your helmet won't do anything to help.   Or, you can die slower from internal bleeding....again, what's that helmet doing for ya?    :o)

Anyway, not to be a fear-monger here.  If she's comfortable with the speed, rides smart on curves, respects traffic, and has her bike in excellent mechanical condition (wheels trued and dished, good tires, frame in alignment, good brakes with fresh pads) then hey, have fun with it.   If her tires are loose fitting on the rim or in poor condition, or if the bike has any shimmy/vibration at faster speeds, then the scare and risk factor go up fast.   You can ride for your whole lifetime and not crash, but the one time you do, you'll be faced with a choice of whether or not to repeat the risk.   Some of us are dumb that way and have lots of x-rays under our belt.   (see my halo...)

:o)

(ps...that part above about opossums on the road made me laugh!  But it's true!  I feared for my life in Ohio once when I ran over a dead squirrel at 43mph and frequently came up on dead raccons and rabbits on the curves.  Anything in the roadway becomes a bigger hazard when you're rolling fast, especially when you're on tiny tires and a racing geometry road bike.  Not only can you lose control, but if you get a flat at high speed from something like a piece of blown car tire in the road, you'd better be able to hop off the bike quickly or you're going to crash hard.)

Answer 5

see that she is an experienced cyclist, that she has a very good helmet and that she keeps well away from your car. She HAS to keep her distance...if she falls over when she's too close to your car, she might get seriously (fatally?) injured. Check her brakes to see if they're good enough. Scan the road for any potholes or loose stones - even small ones can make a bike veer in the wrong direction. Finally, are there side streets where other cars can suddenly drive out and hit her? Are there many pedestrians, especially children? What if they suddenly cross the road - would she be able to stop just in time?