At first I thought this might be the seam, but usually they are a perpendicular, straight line. Either way, should I be worried?

Where is it in relation to the valve hole?

looks like a deep scratch from rubbing against a curb/rock/whatever.
sandpaper it, if it dissapears, it was just a scratch

+1

An impact probably caused the gouge at the edge, the rest is either a fracture, or a scratch. Most likely a scratch looking at how it gets a bit thicker on the less worn area of the rim. If you want to be sure, remove the tire and look inside, rather than sanding. Cracks go clear through, scratches don't. If it's a scratch, ignore it and the brake shoes will polish it out soon enough. You might also just ride it and see if the brakes polish it out which will only take a day or two, thereby confirming the scratch theory.

If it is cracked, and the crack does not extend around to the bottom of the rim, you can ride it a while longer, as the inflated tire will preserve the alignment, but it's a short term thing, so start lining up the replacement now.

Opposite.

I think the crack / scratch has been there a few days already, so it's not getting polished out. I'll try to pull the tire off when I get a chance to get a better look.

that tire looks ancient, and those brake tracks look pretty badly worn out, so it might be time to be considering new rims anyways, and putting new tires on them.

Gatorskins look like that. Perfectly normal.

Edit: Well... It certainly doesn't look like its in very good condition. New tires wouldn't hurt.

If it is a crack, do not pass go and replace the rim / wheel.

If it is a scratch you can buff it out... have had my fair share of these on the polo bike which does have brakes so the scratches become very noticeable right away.

yeah, that first picture in particular, the tread surface looked like it was covered in a lacework of cracks. never seen one that bad.

Look at the tread rubber. That tire is ready for retirement.

Hi,

Why are fine cracks in the tread rubber a problem ?

The rubber has hardened somewhat I guess so somewhat
less grip, but if the carcass is fine whats the problem ?

I guess if the sidewalls have hardened it won't roll as well, but
if they are thin good rolling types will it make much difference ?

According to Sheldon Brown "Cracks in the tread are harmless."

Why needlessly change a tyre for such tiny cracks ?
They are tiny and appear to be very surface only.
There is loads of tread and life left in that tyre.

rgds, sreten.

S.B. :

" Many cyclists waste money replacing perfectly functional tires
simply because they're old, or may have discolored sidewalls.
If you just want new tires because the old ones look grotty,
it's your money, but if you are mainly concerned with safety/
function, there are only two reasons for replacing old tires:

1. When the tread is worn so thin that you start getting a lot of flats from
   small pieces of glass and the like, or the fabric shows through the rubber.
2. When the tire's fabric has been damaged, so that the tire has a lumpy,
   irregular appearance somewhere, or the tube bulges through the tire.

"

The cracks won't cause the tire to fail but they do indicate the rubber has lost flexibility and thus it has lost grip. Gatorskins don't start with a lot of grip to begin with. Be very careful on wet pavement and metal features or lane paint.

Keep riding, report back when it fails, with pictures!!!

JOKING!!!!

Look into that rim, get the tire off and see if the crack is spreading through the rim. Replace that tire, it looks as if it has zero grip left with all that dry rot. New tube as well, they are cheap enough. My guess is that it IS a fracture in the aluminum, originating at that ding in the edge of the rim. If its spreading inside, replace the rim. If its not yet inside, ride it but keep an eye on it.

Also...I would keep the wheels a little cleaner, look at the spokes! Clean bike makes cracks easier to see early, before a failure happens!

Edit: ok maybe those are black spokes, but they still look dirty. The nipples sure do.

If it's exactly opposite the valve hole that would make me think it's the rim joint although I've never seen one that was angled like that before.

Rims are in heavy compression when the spokes are tensioned so I don't think you're in a lot of risk of the rim suddenly blowing apart but you could see some issues such as brake pads catching on the crack, etc.

If your rim is cracked I would probably replace it, but all of these people harping on you about your gatorskins are perhaps being overzealous. I rode a pair for a LONG time past them looking at that, because they looked like that pretty shortly after I bought them. They weren't the grippiest tires in the rain to begin with because they weren't designed for that, and I didn't think the performance noticeably deteriorated when they had superficial cracks like that on the tread.

From the pictures it looks to me as if the outer perimeter of the rim has been flattened for about 2 inches of the circumference. I would assume that the flat spot and nick and possible crack are all cause by a fairly hard hit. Reminds me of when I hit a railroad track at 20 mph once. If you remove the tire and tube you could confirm whether or not there is a flat spot in the rim by spinning the rim slowly adjacent to a stationary object.
It's really difficult to assess the damage (if any) via "cyber space", though the quality of the pictures is good.

Hi,

I don't buy it. The cracks are tiny and surface.
It may have lost some grip, or gained some.

They will be no worse and probably slightly better
on "wet pavement and metal features or lane paint".

They might be worse on the slickest surface,
but I doubt it, they look absolutely fine to me.

rgds, sreten.

Checking again they are a lot smaller
than the actual tread pattern, IMO that
makes them really a complete non-issue.

You never saw it because you cannot make a rim with an angled joint. When built the rim is under intense compression, running along the circumference. A joint hat isn't exactly radial would invite slippage of one side under the other causing the rim to buckle.

The rim looks toast to me. The not small nick by the tire seems to have a crack inside and it sure as hell won't buff off.
It looks very well used and beat up to start with. I would start off summer with a new rim.

+1 It looks like a flat spot besides, in of itself it would not be a problem. I have been riding a deeper flat spot 4,000 miles.

There seems to be two issues here:
1) take the tire off the rim and look at the inside of the crack area. A real crack will show all the way through. ....If the rim is cracked, it's immediately trash. If you absolutely must ride it, at least drop the pressure way down to 50% of normal or so.
2) A cracked tire is a bad tire, with one exception. If the cracks go deep enough to expose a portion of the casing threads, then road grit works down into the cracks and into the threads and then grinds up the threads as the tire flexes (and the tire does flex, as it rolls). The lone exception to this rule is tires on indoor-only (velodrome) bikes, since the question of road grit is absent in their use.

This looks like a cracked rim. It should be replaced, and I'd suggest new tires too. As rubber ages, its grip characteristics deteriorate considerably, they are also far more succeptible to punctures.

As an example, old motorcycle tires are dangerous, they no longer adhere well to the road.

A new tire may give you a better margin of safety when dry, and certainly when it's wet.