Afraid of descending

[I like Skol]

Pythagoras.

EDIT: Actually Pythag and vectors of force.

 

[Dogtrousers]

I never really found out for sure. The tyre was in good nick but afterwards there was a gash in the sidewall, close enough to have been caused by rubbing on the block over time. I didnt think that was likely but I don't entirely rule out schoolboy error for sure. I assumed I'd hit something previousy and hard front breaking caused the failure. I generally run my tyres at 100 psi.

I wouldn't have thought that your brakes would have time to overheat going down the Beacon would they? Not that I have any knowledge of brakes, but just to note that it's only about 1.5km long, and follows about 6k of gradual climb, and possibly a view-admiring stop at the top, where you won't have been braking at all.

 

[Yellow Saddle]

I wouldn't have thought that your brakes would have time to overheat going down the Beacon would they? Not that I have any knowledge of brakes, but just to note that it's only about 1.5km long, and follows about 6k of gradual climb, and possibly a view-admiring stop at the top, where you won't have been braking at all.

1.5kms is plenty of distance to overheat brakes if used improperly. If you descend slowly, dragging the brakes, then they heat up without the benefit of air cooling and overcook. However, if you go faster, don't drag the brakes but only brake in short and sharp bursts, they cool down sufficiently and don't transfer the heat to the tyres.

Tandem riders in particular fall foul of rear wheel blow-offs. They're extra heavy, extra scared and like to drag the rear brake. In fact, a drag brake was invented just for this purpose. It is usually a third brake which is located on the rear wheel. It is either a drum or disc and sometimes even activated with a friction shift lever so that it can be applied and left to drag until later - almost like a handbrake.

 

[Dogtrousers]

I remember my mate's dad giving us a lecture about not overheating the drum brake on his tandem before we took it out. This was in the 70s. We probably ignored his advice. I'm afraid all I can remember is that it was yellow and that having handlebars that wouldn't steer was seriously weird.

 

[Yellow Saddle]

@I like Skol is correct.

The two forces don't just add up to a total.

The resultant force is the hypotenuse on a right-hand triangle where the cornering force (centripetal force if you like) is the one right angle and the braking force the other.

Therefore you have far more traction than you would guess and you can reasonably safely brake hard even in a corner. The trick is to judge how hard you are cornering. Keep in mind that maximum available cornering force on a bicycle on good road is when you lean out at 45 degrees and your cornering force is thus 1 g.
Maximum braking a bike can do without the rear wheel lifting is only about 0.4 to 0.6 g, depending on your body position at the time. Going downhill means your position is unfavourable thanks to the slope, so 0.4 g is about max.

I have no doubt that soon there will be some electronic gadget that does the mental calculation for us and takes the fun out of adrenaline.

 

[Yellow Saddle]

I never really found out for sure. The tyre was in good nick but afterwards there was a gash in the sidewall, close enough to have been caused by rubbing on the block over time. I didnt think that was likely but I don't entirely rule out schoolboy error for sure. I assumed I'd hit something previousy and hard front breaking caused the failure. I generally run my tyres at 100 psi.

It's always a good idea to keep data and photos of accidents for geeks like me. I now don't know if the tyre blew off from too much pressure or whether it burst from a weakened casing.

A good tyre, inflated to about 90% (lots of variable factors play a role here) of its maximum pressure can blow off if the wheel gets very hot from braking. By very hot, I mean too hot to touch after you've come to a standstill. Manufacturers know this and obviously keep the max recommended pressure well below the theoretical maximum.

A quick burst of braking heats the tyre far less than long slow dragging.

 

[rich p]

It's always a good idea to keep data and photos of accidents for geeks like me. I now don't know if the tyre blew off from too much pressure or whether it burst from a weakened casing.

A good tyre, inflated to about 90% (lots of variable factors play a role here) of its maximum pressure can blow off if the wheel gets very hot from braking. By very hot, I mean too hot to touch after you've come to a standstill. Manufacturers know this and obviously keep the max recommended pressure well below the theoretical maximum.

A quick burst of braking heats the tyre far less than long slow dragging.

I doubt it was overheating as I used to speed down the straights and only brake to kill speed prior to the corner, then accelerate out and it's all over in 2 minutes. It's a hill I've done a thousand times but now I'm like Bambi on ice which actually feels more dangerous but hard to overcome.
I'll never know but my best guess is the brake block minimally rubbing on the tyre over time, or a small split caused by hitting a stone or something previously.
A friend I was cycling with once had 3 blowouts due to a split in the wall that was so small it was very hard to spot. We were novices and I think I'd have worked it out sooner now.

 

[Jody]

Everyday is a school day with @Yellow Saddle

 

[Venod]

I never really found out for sure. The tyre was in good nick but afterwards there was a gash in the sidewall, close enough to have been caused by rubbing on the block over time. I didnt think that was likely but I don't entirely rule out schoolboy error for sure. I assumed I'd hit something previousy and hard front breaking caused the failure. I generally run my tyres at 100 psi.

Could the gash in the sidewall have been caused by the rim after the tyre blew off, I say this because I was following a club mate down the North side of Holme Moss, a big lad so he was on the brakes, from the top, just before the 1st LH bend his front tyre blew off, he managed to stay upright but was very lucky there was no traffic as he drifted across the road round the bend, there was no damage to the tyre or tube, he put it on again and completed the ride without further incident.

The same bend was the scene of a spectacular crash on another ride, I had just come round the bend going up when a saw a rider coming down as he passed I thought he is going too fast, I heard a bang he missed the bend completely and ht the wall, his knee was a right mess (difficult to look at) an ambulance had to be called, his new Giant (second time out) was in 2 pieces, he was in shock I couldn't get him to sit down, I had fears he might collapse.

 

[Kestevan]

WRT braking and indicating right, surely the simple solution is to have your brake levers setup with the front on the left as per our friends in the continent.

Most of mine are like this; and an added benefit is that you can change to a lower sprocket more easily as you brake to a stop at junctions.

 

[ColinJ]

I suspect that some of our posts are not helping allay fears of descending!

I am surprised that people have not occasionally been hitting 100 km/hr on Holme Moss. I have touched 90 going down the A58 from Blackstone Edge to Littleborough and the A646 in Burnley after the Manchester Rd traffic lights as the road plunges down towards Rose Grove. Neither of those descents feel as scary as Holme Moss. I suppose the extra 10 km/hr would be hard to gain though, especially because pedalling is not going to help at those speeds.

 

[Yellow Saddle]

WRT braking and indicating right, surely the simple solution is to have your brake levers setup with the front on the left as per our friends in the continent.

Most of mine are like this; and an added benefit is that you can change to a lower sprocket more easily as you brake to a stop at junctions.

I want my strongest, most dexterous hand controlling my most important brake.

 

[Kestevan]

I want my strongest, most dexterous hand controlling my most important brake.

So do I

 

[Alan O]

Ah, someone is paying attention. I was getting depressed there.

No, it isn't. I take it you are responding to the 2 and 2 scenario?

The answer is 2.82. I'll give you some time to chew on it. However, most people guess 4 and ride as if it is 4 even if they don't know the answer. This one isn't instinctive.

Well, I guessed it couldn't be that simple

I do know that 2.82 is 2 times the square root of 2 - is that getting close?

Alan

 

[Alan O]

Well, I guessed it couldn't be that simple

I do know that 2.82 is 2 times the square root of 2 - is that getting close?

Alan

Ah, now, I deliberately made that guess without checking any other replies, but now I see the words "Pythagoras" and "vector" I do think I've got it, by jove!

Vector triangle, two equal sides of length 2, so hypotenuse is the square root of (2 squared plus 2 squared) = root 8 = 2.82.

Alan