Sunday, June 14, 2009

Chain Suck . . .

Saturday Phil and I went to Buffalo Creek for a truly great day of mountain bike riding.

The wildflowers were gorgeous!

Well, okay – mostly truly great. Because there were a couple very unpleasant episodes of chain suck that nearly ruined the whole adventure.

As I noted earlier, Phil just picked up his new Santa Cruz Blur XC Carbon (WB II) bike this week, and was quite anxious to take it out for its first ride.

With all the rain we have been getting in Golden, Phil was really skeptical when I told him riding at Buffalo Creek would be fine. He was sure it was going to be a soggy muddy mess.

But Buffalo Creek’s trails are quite sandy; and where they aren’t sandy, they are comprised of pea-sized decomposed granite gravel. Riding out there after a big rain is actually a lot of fun, because the moisture gives the trail a more tacky texture, and you can keep your wheels from spinning out even if you lack basic technical skills – like me!

So, we unloaded the bikes – and had to borrow a tire pump from the folks who were parked next to us – thank you! The day would have been ruined otherwise, because Phil’s tires had about 7 psi . . .

Then we got on the trail heading to Gashouse Gulch. Phil shifted, I heard a “thunk” and saw he had dropped his chain. Assuming it was no big deal, I proceeded on.

After waiting about 10 minutes at the trailhead, I realized there was a problem, and rode back downhill to find him. He was working to release his chain from where it was tenaciously lodged between the back of his cassette and his spokes.

To quote the great Sheldon Brown:
Chain suck occurs primarily when downshifting under load from the middle to the smallest chainring. The bottom run of the chain may not immediately disengage from the middle ring, and can get carried upward until it wedges betwixt the chainwheels and the right chainstay.

This jams the crankset. Since you probably wouldn't have been shifting to the granny if you weren't already climbing, the sudden lock-up of the drive train deprives you of what little momentum you had, and you are very likely to stall and fall.

Chain suck is commonly caused by bent chainring teeth, dirty chains, or, occasionally, burrs on the teeth of new chainwheels.

In Phil’s case, he would find out later that a slightly bent rear derailleur was the source of his trouble, but we didn’t know that at the time.

After working at it for close to 25 minutes, Phil got his chain untangled, and we were off.

Conditions were perfect and we had a great ride . . . until we were about 1 mile from the top of the last climb of the day, and Phil was thrown to the ground by the evil chain suck monster.

It looked grim for about 30 minutes, but ingenuity and some good old-fashioned brute strength freed the chain. We wrapped up the day just before the rain moved in.

When I shared the following analogy with Phil, he just sort of grunted and rolled his eyes, but I think it is valid, so here you go:

Your first ride on a new bike is quite similar to your first sexual encounter with a new partner.

You have been anticipating the day for some time – weeks, maybe even months. You want everything to be perfect.

And it rarely is. There are almost always small “mechanical” problems that take some time and patience to resolve.

That patience, however, will be rewarded in the end. Phil’s love affair with WB II got off to a rocky start, but I think it will all work out . . .

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