[matt2991]

I have a 2005 Specilized Allez. Ever since I put my junior gearing on, I realized that there is a very noticable amount of drag on the rear end of my bike. My tires are inflated, brakes aren't rubbing, and all the rest of the basic signs. I took it to the bike shop, and there weren't able to tell the problem. The mecanic agreed with me and said that there is a weird drag. My coach said that my frame flexes. I was just wondering if that is possible, and if it is my frame flexing that is causing the annoying drag/feeling that my bike has a bag of bricks attached to it.


Thanks so much,
Matt

 

[sanjuro]

Keep in mind that whenever there is some phantom noise or rubbing, 90% of time it is the rear wheel, 6% the chainring bolts, 2% front derailleur, .9% the bottom bracket, and .01% the frame, especially if you have an all aluminum frame.

What I would do if I was your mechanic is remove the rear wheel, check for bearing play, spoke tension, freehub wobble, and if your axle is broken.

After that, I would tighten all the chainring bolts.

You should also check the derailleur hanger bolt and the dropout bolts, if it is a carbon rear triangle.

But if you changed gearing, there is a strong possibility it is the front derailleur, especially if you switched to a compact crankset. If you did switch to a compact crank, the front derailleur had to be moved to fit the smaller chainring.

Finally, frames do flex, although much less than people think. If you are 250lbs or put out 400 watts, yes, you will notice flex, although I doubt it on an aluminum frame.

Frankly, I think detecting mystery problems is extremely difficult for anyone besides expert mechanics. I have seen junior mechanics totally miss an issue like this and then a master finds it in a minute.

 

[matt2991]

Cool, I am going to bring it to the shop again tommorow. The thing is my coach started pulling the frame and you could see it flexing. IDK though? I am gonna ask my mechanic again. Hopefully it is a quick fix because I have a race Sunday.

 

[matt2991]

If I did replace my frame, it would be a Blue RC8 (team sponser)

 

[matt2991]

It happens mostly when I sprint or climb. However it still happens when I am in my granny gear.

 

[ire]

Does the frame have a crack? I think a cracked frame is more plausible than excessive frame flex

 

[matt2991]

No crack on the frame. IDK why my coach said my bike has a really noticeable flex. Like when I am riding, it feels like my rear tire is always flat.

 

[JRogers]

I agree with others that the chances of your problem being that the frame is actually really flexy is pretty small. Aluminum frames, even cheap ones, can be made quite stiff and it would be a difficult thing to notice for an average rider. I would bet that something is wrong with your wheel (the things Sanjuro suggested) or, maybe more likely, it's just something about the way the bike rides.

I remember a thread on another forum where a guy complained for a similar thing on his TT bike- he said it felt slow, like something was dragging him and making him slower. But he did a test by riding the bike on a set course and comparing his time with other times he had ridden the same course. He found the problem TT bike to be significantly faster.

 

[maddog17]

is it possible that the rear rim has a crack in it?

 

[matt2991]

Just had the mechanic look it over. He found nothing. He said I should try a lighter and stiffer frame. He said it could be flexing depending on how much power I give out. Its really weird and frustrating because I defiantly feel a significant drag. Maybe I am just being weird and a weight weeny.

 

[sanjuro]

Personally, I would seek out a second opinion.

I've heard of cases where aluminum felt dead after several years, but I doubt highly an aluminum frame would ever flex.

 

[matt2991]

Ya I doubt that its flexing, but who knows. My coach and teammates think I am an idiot for not agreeing with them. But I think they are idiots for seing a flex.

 

[ire]

Ya I doubt that its flexing, but who knows. My coach and teammates think I am an idiot for not agreeing with them. But I think they are idiots for seing a flex.

My advice would be to learn to wrench on your own bike. It helps if you know how to take everything apart and check for issues...I rarely let other people work on my bike.

 

[maddog17]

for them to see a flex would mean that there is a break somewhere.... or your riding a frame made out of beer cans.

 

[JRogers]

I will just say again that I highly doubt it's the frame flexing. If the wheel is fine and you don't think it's in your head have you tried different tires? I think generally people greatly overestimate their ability to discern differences in frame material and stiffness.