Bicycle Mechanics - Sidwall tear - possible brake pad issue or other?

Hello Mechanics,

I own a 2005 Trek 1000 all OEM parts. I am the second owner. Since I started riding in May, I have had 2 small sidwall tears on the front tire, left side just above the tire bead. I researched some old threads, like this one [http://www.bikeforums.net/showthread.php?t=288270&highlight=sidewall] that seem to describe the situation, but not exactly. My tears are about the size of a grain of rice (6-8mm), not the length that the pictures in the post exhibit.

During my last ride, I got a flat, no big deal. I was prepared with proper equipment. The puncture was on the rim side of the tube, centered. I patched it and upon inflating got another flat which is when I noticed the sidewall tear. I used a tire boot to get home.

Upon evaluation of my front brake pads, I have noticed that the right brake caliper's contact point with the rim is perfect. However, the left side, where the tears occur, seems to make contact on the rim, but may touch the tire slightly as well, it is tough to tell. I have looked for ways to adjust this, but I just can't find what I am looking for.

Does this sound like a possible brake pad issue or could it be the tire's construction itself? I had purchased a new tire a month ago (Seca Serfas for $20). Could it be from the tire lever while repairing the flat?

Any help would be appreciated.

Thanks!

It sounds like you've got more than one problem.
The puncture centered on the rim side of the tube sounds like you need new rim tape. I recommend Velox rim tape in the appropriate width.
The brake pad needs to be adjusted so that it is definitely not touching the tire. Use the pads through caliper fixing bolt for this.
Defective tires or cuts from road debris are also possibilities, but one thing at a time.

Al

It sounds like you've got more than one problem.
The puncture centered on the rim side of the tube sounds like you need new rim tape. I recommend Velox rim tape in the appropriate width.
The brake pad needs to be adjusted so that it is definitely not touching the tire. Use the pads through caliper fixing bolt for this.
Defective tires or cuts from road debris are also possibilities, but one thing at a time.

Al

I have the pad all the way at the bottom of the opening... is that normal for 700x25c tires and basic Alex rims?

I will replace the rim tape. Thanks!

How do your pads look? There should be some sort of wear indicator. As your pad wears, the front left brake arm on dual-pivot brakes will start to swing up a bit. This will raise the pad, but it shouldn't be enough to reach the end of the adjustment range.

Also, if your front wheel is out of dish, to the right, the brake arm will have to reach further. You could check this by flipping the front wheel around and squeezing to brakes to see if the pad appears lower.

Is the front brake centered? Again, if it's off to the left, the arm will reach further and raise the pad.

There might also be a flat spot in the wheel. Does it reference the brake pad without up and down motion when spinning?

Other than that, I dunno. Make sure there's nothing in the dropouts preventing the axle from seating all the way. Is it possible that your fork is bent?

Do you install your tires so the label is always over the valve stem? If so, were the two tears in the same place relative to the label?

Photos of the brake closed around the rim might help.

How do your pads look? There should be some sort of wear indicator. As your pad wears, the front left brake arm on dual-pivot brakes will start to swing up a bit. This will raise the pad, but it shouldn't be enough to reach the end of the adjustment range.

Also, if your front wheel is out of dish, to the right, the brake arm will have to reach further. You could check this by flipping the front wheel around and squeezing to brakes to see if the pad appears lower.

Is the front brake centered? Again, if it's off to the left, the arm will reach further and raise the pad.

There might also be a flat spot in the wheel. Does it reference the brake pad without up and down motion when spinning?

Other than that, I dunno. Make sure there's nothing in the dropouts preventing the axle from seating all the way. Is it possible that your fork is bent?

Do you install your tires so the label is always over the valve stem? If so, were the two tears in the same place relative to the label?

Photos of the brake closed around the rim might help.

I didn't the first time, but now I always do... all I know is that the tear is on the same side.

Another possibility (which happened on my tires) is that if you run flat resistant tires with not enough air pressure, the rigidity of the tire sole will make the sidewall bend excessively and eventually tear.

I have seen some older trek 1000s with your same problem. The brake pad does not reach down far enough and rubs the tire. This can be solved by getting a longer reach caliper, making a drop bolt, or grinding down the bottom of the brake pad hole so the pad will sit down farther (don't worry there is plenty of material there)