Cycle carriers in the wind

[Falwheeler]

Just bought a Thule roof mounted cycle carrier and intend using it for a trip to Dartmoor tomorrow, a trip of about a 100 miles. Are these carriers safe, secure in the gale force winds we are enjoying down here at the moment?

 

[Pauluk]

I've got MontBlanc carriers. Think Thule are very good too. My speed is limited to 75 mph with the carriers and bikes on. I expect it gets quite winding up there at that speed so I think you'll be fine.

 

[Falwheeler]

Thanks Pauluk, only used rear mounted carriers til now

 

[Broadside]

I don't have anything scientific to this but I don't go over 60/65mph with bikes on the roof (I use Thule too). The increased wind noise at that speed is enough for me to think any faster is going to rip the roof rails off the car!

You do however see plenty of people doing 90mph with bikes on the roof but I go slower because there are no prizes for wrecking your bikes by them falling off!

I think cross winds are your bigger worry, if it is really blustery then I would go a fair bit slower but I wouldn't let it prevent me from travelling.

 

[lulubel]

I haven't had bikes on the roof, but I have done 80-85mph (all the way down through France and Spain) with a massive roof box on the top without any problems. Considering the bikes have a much smaller profile, I'd think they'd be fine.

 

[Peteaud]

I have thule bars and halford carriers on the roof.

No problems at 70mph even with strong side winds (today on the A303)

Just double check everything and i stop 1/2 way just to check things over.

 

[Pauluk]

I suspect the main issue with roof carriers is if you were to ever have to do an emergency stop at speed. I'm not sure that the locking clamps and wheel straps would hold on to a couple of 10kg-15kg bikes if you were to brake very hard at high speed. I usually keep my speed down (below 55mph) for this reason.

I don't think cross winds are that much of a problem compared to the forward momentum under hard braking.

 

[Peteaud]

all the weight of the bike should be going through the clamping arm.

That said, i have never braked hard with the bikes on top.

 

[Pauluk]

all the weight of the bike should be going through the clamping arm.

That's true Pete, and the forward force will be into the clamp jaws too, not out.

Mmmm must try this next time

 

[Norm]

I suspect the main issue with roof carriers is if you were to ever have to do an emergency stop at speed. I'm not sure that the locking clamps and wheel straps would hold on to a couple of 10kg-15kg bikes if you were to brake very hard at high speed..

I'd be very surprised if something which is sitting in a 55mph wind had any forward force at all when braking hard. I would expect the wind resistance to be much more than any forward momentum during braking at any speed over about 40.

Another way of saying that is that I find it considerably easier to stand up on a braking tube train than I do standing on the pegs of my motorbike at motorway speeds.

 

[Peteaud]

That's true Pete, and the forward force will be into the clamp jaws too, not out.

Mmmm must try this next time

Perhaps someone with a very expensive carbon bike can test the theory for us, any takers.....

Actualy, can you put carbon bikes in those clamps?

 

[Pauluk]

I'd be very surprised if something which is sitting in a 55mph wind had any forward force at all when braking hard. I would expect the wind resistance to be much more than any forward momentum during braking at any speed over about 40.

Another way of saying that is that I find it considerably easier to stand up on a braking tube train than I do standing on the pegs of my motorbike at motorway speeds.

Firstly, trains don't decelerate that fast even under emergency braking, its just as well since they don't want passengers ending up in the drivers cab.
Secondly, if you were to sit on my car roof and hold on to the roof bars as I braked at 55mph I think you would find that the forward inertia of your body would make it very difficult for you not to be shot down the road like a human canon ball even with a head wind.

Pete, can we test this one instead

 

[Norm]

That's probably because my mass-to-drag ratio would be a little different to a bike's. Try the same trick with a sheet of A4,

 

[Peteaud]

Firstly, trains don't decelerate that fast even under emergency braking, its just as well since they don't want passengers ending up in the drivers cab.
Secondly, if you were to sit on my car roof and hold on to the roof bars as I braked at 55mph I think you would find that the forward inertia of your body would make it very difficult for you not to be shot down the road like a human canon ball even with a head wind.

Pete, can we test this one instead

All we need is a test dummy

That's probably because my mass-to-drag ratio would be a little different to a bike's. Try the same trick with a sheet of A4,

We need to test this mass to drag ratio.

 

[Pauluk]

All we need is a test dummy

We need the dummy, a bike and a piece of A4 paper. My guess, and its just a wild arse guess, is that the dummy goes furthest, followed by the bike then the A4 sheet will probably be no where to be found.

Interestingly enough I spoke to the MontBlanc development engineer some time ago via email, when I bought my carriers, about the maximum bike weight for their carrier. They told me 15Kg. I said that doesn't seem much as my roof bars could take over 75Kg, but she said that during the design and test stages they have to consider all eventualities like high speed cornering and braking. I said my bike (at the time) was 15.5Kg and she said I couldn't carry it on their carrier. I just removed the seat/seat pin then it was just under 15Kg.