Bicycle Travel > General Discussion

Long, steep descents -- questions about safety

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New Jawn:
Not long ago I finished a section from Oxford, OH to Newton, KS -- yes, some hills but nothing that I would call mountainous.  Now I'm looking at some long rides that will definitely have steep descents, some perhaps long, continuous descents (think western CO) or long descents with lot of curves (Appalachian Mts). 

So, just let it roll unchecked?  I would guess that speeds  could easily go over 40 mph and perhaps higher?   Just thinking about it makes me a bit nervous.  Assuming the road isn't too curvy, just not worry about how fast I'm going?   I've seen Tour de France footage of those guys going downhill like rockets and there's no way ever that I would have the guts to do it. 

If I try to keep the speed down, I'd think that my brakes could overheat (Surely Disc Trucker), so alternate front and back brake?

Any advice on how to address long, steep descents in a safe manner?

Thanks in advance.

I think I got up to 53 mph loaded down with gear on a long, straight descent in Nevada.
I actually passed a dump truck that had down-shifted.
The driver saw me coming up behind him and had a shocked expression.

But really - airport runway straight and almost zero traffic - plus I had 1.95 tires.

Descents depend upon a number of things:
1. % Grade - The steeper it is the more likely you may get into trouble.
2. Road Width - 12-foot lanes or less? Shoulders? Mountain roads are often narrow.
3. Traffic Volume - The more traffic there is the more the challenge. Drivers are grumpy if you are just doing 30 mph.
4. Road Surface Condition - Mountain roads often have more wear & tear. A sudden pothole and you are done in.
Also 5. Brakes - Disc brakes or rim? Disc brakes are more powerful and rim brakes can really heat up your rims.

In contrast to Nevada, I've ridden Going to the Sun in Glacier N.P. more than a dozen times.
The west side has a longer descent at a constant 8%, but the road is narrow and packed with cars.
What I do there is stop frequently at overlooks to let traffic go by and then start again in the gaps.

Obviously, if you have a lot of switchbacks, you can't let it rip.
(If you are not sure, you should expect a switchback or two just to be prudent.)
Also, be careful for the oncoming, uphill traffic.
Impatient folks behind a slow truck can and do pull out into your lane to pass.

Hope this helps. - J

Pat Lamb:
In addition to John's road condition consideration, I'd add whether or not there's gravel (or rocks) on the road, and whether the road and/or your brakes are wet.  There was one lovely pass where the road was a consistent 6%, but there were occasional 3-6" rocks on the road -- you want to make sure you can safely steer around those!

Also, brake early and often if it's raining so you can clear your brakes.  Rim or disc, if the braking surface gets wet you don't have brake power.  And yes, it can happen with a good rain rate on discs!

Other than that, brake as you need to maintain your speed so you can steer the bike.  Riding the brakes is bad, you're better off either alternating wheels (front for 10 seconds, rear for 10 seconds), or pulsing the brakes (brake hard for 5 seconds, let it roll for 5).  If you think the brake surface is getting too hot, stop and let it cool.  Take a few pictures, have a drink and a snack, squirt some water on the rims and see if they've stopped hissing when you do that.  It's possible to blow even a mountain bike tire off the rim if you overheat it too badly; skinnier tires at higher pressure are closer to blowoff if you ride the brakes.

I have done some very long steep descents. One was so long and steep and at such an angle that by the time I got down to level ground again both hands felt as though they had been beaten with a hammer. All I can tell you is this. Work the brakes alternately and sometimes front and rear at the same time, off and on off and on off and on. I have heard of rims Heating and popping the tube. Never had that problem. Just break to keep the speed down and let off. Break to keep the speed down and let off, and just keep doing that.

In addition to everything mentioned above - be wary of loose gravel.  I was coming down Mt Graham in AZ, wasn’t loaded with gear, had to be doing at least 30 mph just before a hairpin curve.  As I was breaking I hit a patch of gravel.  Not sure of the exact chain of events but front tire went flat - bike and I did a complete flip.  Broke my collarbone and a couple of ribs and my helmet was cracked in 5 places.  Needless to say I am very cautious before entering any hairpin curves.  I slow down well before the curve.


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