Monday, September 17, 2007

Q&A: Drag

QUESTION:
Dear Mr. Langley,

I have had a problem with my Seven Alaris ti frame of late. It has a Shimano Ultegra triple. The wheelset is Mavic K's ssl. My weight is 240 lbs. I ride 100-150 miles/week. I feel a drag in the rear of the bike and its not my rear. It occurs in certain gears, when I apply moderate to heavy pedal force. It is intermittent, but can be duplicated on a hill with the front middle chainring, and middle of rear cassette. The bike has been checked and wheel hubs have been replaced or adjusted, brake calipers have been checked and centered. The freebody hub has been changed, I have tried different wheelsets and skewers. Although my gut feeling is that it is not the frame I have run out of troubleshooting ideas and may have the frame checked by Seven. I would really appreciate your feedback on this issue.

Regards,
Nicholas

ANSWER:
Hi Nicholas,
Sorry to hear about the problem. I wonder if you have checked your chain, cassette and chainring for wear? If any of the 3 are worn out or nearly worn out, that can make the pedaling feel terrible. I wouldn't call it a "drag" feeling, but it's kind of like that because there's more resistance and you feel like you're working too hard to pedal the bike. Another consideration is the derailleur pulleys. These wear and can bind and they can make it considerably harder to pedal. Ditto for the bottom bracket bearings. You can check either by lifting the chain off and turning slowly by hand. There should be little resistance in the pulleys and the crankarms.

I know you meant drag as in overall bicycle drag, but my experience has been than sometimes riders sense or feel drag from other parts of the bike and think it's the wheels or brakes when it's other things. The fact that you mentioned pedaling and what gear it's in made me think of these possibilities.

Of course there is also the sobering possibility that the frame has cracked or broken where it's hard to see. For example, you might closely inspect the rear dropouts and see if one is cracked. It might be almost impossible to see. Get down close with a flashlight and have a friend push sideways on the wheel to put some stress on the dropout. If it's cracked it just might open up and you'd see it. If that's the problem, the wheel would be able to shift when you're riding and strike the brake causing the drag. A broken chainstay or seatstay might do something like this, too. You can usually find cracks by flexing the bike various ways and watching the tube junctures closely to see if they move, shift, or open up.

I hope this helps you solve the problem and that if it is a broken frame Seven get it's fixed up for you soon. If you find out what it is, I'd enjoy hearing about it.
Jim

2 comments:

alex said...

I have the same thing going on now, my situation is a bit different but the feeling is the same. I switched to the Reynolds DV48c wheels and a SRAM cassette and that’s when the feeling started. Previously I was using the Mavic Ksyrium SL wheels and a DA cassette. Thinking it could be something other then the wheel I also changed the chain, but the feeling is still present. Side note I only get this sensation on climbs…. What should I do next? I am thinking about going back to the DA cassette. Also, could it have anything thing to do with the spoke count of the DV wheels?

Thanks,
Alex

Bicycle Aficionado www.jimlangley.net said...

I would try removing the wheel and feeling for anything unusual in the hub or cassette. They should turn easily on and off the bike. If something isn't fitting correctly, it could cause binding and drag and you might be able to feel this. You could also try a different cassette and see if the feeling goes away, which would indicated there's a problem with the cassette or the way it fits. Nothing against SRAM but I have heard more tales of defective parts about their new products than from other companies. They're good about taking care of these issues but you'll want to check closely. It shouldn't have anything to do with the spokes in your wheels in any case. If they were loose that could make a bike feel slow but if the wheels are new the spokes should be very tight and not a problem. You could try putting your wheel in someone else's bicycle to see if it feels like it drags there. And you can try installing a different wheel in yours to see if the drag stops. If you can be certain it's your wheel, then you can experiment with different cassettes or checking the hub and bearings to make figure out what's causing the problem. Remember that when you close the quick release it compresses everything and you have to consider this, too. Hope one of these suggestions helps solve the problem.
Jim