maybe your braking too much? If your doing say 5omph on a long descent and you want to stop to check your rim temp, you brake to a stop, heating them up, then touch them. Maybe it's the braking to check them that is heating them up. I've done some pretty long, technical descents, up to 21miles, and really don't touch the brakes more than a couple of times.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

Beloki lost a tire when he skidded sideways, skipped his rear wheel and rolled a tubular. Also, note that the pros probably do a lot less braking on descents than us mortals, who also don't have road closures.

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"Go yell at an M&M"

Well Dude, you have more cajones than I. Good point on extra heat generated from stopping. Had not thought of that. Are there really hills in Phoenix? A friend of mine (and reigning world champ AG triathlete just moved to Scottsdale). Some of these local mountains have switchback like turns and as brave as I like to be I just have to brake sometimes. I guess I am a wuss but I force myself to imagine the faces of my two kids when I start getting a little too aggresive.

Beloki rolled a tire when the glue became sticky (i.e., started to liquify) because of the heat of the road. Hit a corner the right way, and off it goes. If you watch the video, he actually did an incredible handling job of the bike before being planted on the ground. Us mere mortals would have done a lot more skidding/flipping/screaming.

I don't think you have much to worry about. The biggest thing is burning through brake pads and potentially warping the rims. I'd bet the actual increase in pressure is relatively low, and still below risk of a blow-out. Jobst Brandt (wheel guru) had some articles related to exactly this. I'll see if I can find them and post a link.

For inspiration, check out this photo: http://velonews.com/...%20Mike%20Elmer.html Now that's a descent!

Chris

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"I do not hurt on the bike, I punish."

Mike- I wouldn't worry about it too much. I've only blown a tire from braking heat once, coming down Hauser bridge off of King Ridge up north of here. That gets seriously steep before the hairpin at the bottom, and I'm a wimp on technical descents. You know the roads i ride out here, and I've only done it that one time.

that being said, I only inflate my tires to about 110 psi anyway, I don't think there's much need for any higher pressures around here.

J

[reply]I have always wondered about this. There are some pretty steep climbs around where I live (Nor Cal) and sometimes when I am doing a long (ie, over 5 mile) descent I have on occasion stopped and felt the rims of my wheels and found them to be extremely hot. I don’t ride the brakes and try to feather off and on but the rims still get so hot they are sometimes too hot to touch.[/reply]

"Too hot to touch" typically means somewhere in the 145-170F range. Given that tires increase in pressure by 1psi per 10F (I think that was the number quoted to me) then the tire will be at most 10psi higher at 170F than at 70F. If the 1psi/10F isn't right then it could go higher than that. I ride at 120-125psi most of the time, so if you start at 70F and 110psi the chances of popping from high psi are fairly low. With tubular glue 170F might be more of a concern, but I don't think that clinchers will have the same issue. I used to go down hills in Ithaca NY all the time and have to go from 40mph to a dead stop frequenly with no issues.

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Beloki never actually rolled the tire. He did what in motorcycle world is called a highside. His wheel skidded, hooked up and down he went. Either way he went down.

You're partly right. He did highside it, but when it hooked up again it took the rear tire off the rim. Pics post-crash clearly show the tire off the rim.

In part, from http://www.sheldonbrown.com/brandt/descending.html Guess there is the potential, but I think Jobst is referring to very very steep European descents. If you don't know who Jobst Brandt is, you don't know bike wheels ;-)! Braking Heat on Steep Descents

Although tandems with their higher weight to wind drag ratio have this problem more often, steep mountain roads, especially ones with poor or no pavement require so much braking that single bicycles blow off tires from overheating. For tubulars the problem is not so much over pressure than rim glue melting as all pressure sensitive glues do with heating. As glue softens, tires slip on the hot rim and pile up on the valve stem. This is the usual indicator that tubular tire wheels are too hot. The next is that the tire arches off the rim in the area just before the stem.

This is a serious problem both for tubulars and clinchers because most clincher tires, given enough time on a hot rim will blow off if inflated to recommended pressure. Pressure that gives good rolling performance (hard) while tubulars roll off from lack of adhesion to the rim. The faster the travel, the more descending power goes into wind drag and the better the rims are cooled. Going slowly does not help, unless speed is reduced below walking pace.

On steep descents, where rims stay too hot to touch for more than a minute, reducing tire inflation pressure is a sure remedy. However, tires should be re-inflated once the rims cool to normal. The blow-off pressure is the same for small and large tires on the same rim, it being dependent only on the opening of the rim width. Also, tires with a smaller air volume become hot faster than larger ones.

OK, but he was sideways when it rolled, it didn't cause the crash. Had he done a few things just a little better , he would have made it. When it slides, do to light or heavy braking, you let the brake go, this causes a return of traction and goodbye. On the motorcycle it is a loss of traction from spinning the tire, once you roll off and it hooks up--goodbye.

\\OK, but he was sideways when it rolled, it didn't cause the crash. Had he done a few things just a little better , he would have made it. When it slides, do to light or heavy braking, you let the brake go, this causes a return of traction and goodbye. On the motorcycle it is a loss of traction from spinning the tire, once you roll off and it hooks up--goodbye. \\

From my viewing of the video it looked like he started fishtailing when he hit the melting pavement, actually almost managed to save it by 'surfing' the bike down the road, but then his tubular rolled and jamed into his rear brake. which pretty much screwed him.

does anyone have a link to the .mpg of the clip that was floating around the net at the time?

J

2003 TDF videos: http://ww2.olntv.com/tdf03/03tdfvideo.html

Beloki crash: http://mms:/...eo/14action8_300.wmv

--Marcus George
UCLA Triathlon
http://www.triathlon.ucla.edu

If you are feathering the brakes on a descent you are braking too much. You shouldn't touch the brakes unless you need to do it to make a corner and then as late as possible. Brake hard to get to the speed you want and let go.

Staying on the brakes just decreases stability and messes up steering and weight distibution so the minute you get spooked and start using them to scrub some speed things feel worse and you get more scared and you use the brakes more and your rims heat up and ....

You're actually safer using them as little as possible and once you get used to the feel of an unfettered bike you won't be able to go back to riding the brakes because it will feel so very wrong. Bad pavement also causes less problems at speed, kind of like how the pros ride Paris Roubaix cobbles and just glide over the tops.

Yes that is a danger, and yes part of the reasons many smart folks ride tubulars. I once crashed in Colorado Springs (guy in front got a flat on a clincher - rim hit the road - he hit the road - I hit him - well over 60mph) near the Airforce Academy. It was no big deal, the Airforce sent a helicopter to pick us up - I woke up a few days later in the hospital with a Shimano lever in my leg...neat.

A tubular at least stays on the rim if you get a flat...flat down hill on a tubbie you carefully slow down and stop - flat on a clincher at speed your ass is going to splat - for sure if there is a curve of any sort.

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What if the Hokey Pokey is what it is all about?