None of the materials have a rider weight limit, including carbon. They will all work extremely well used in the normal course of riding.
Most riders have problems with bending or breaking a rail when "jumping" a pot hole..curb..railroad tracks..and don't time the jump correctly impacting the saddle. The force of a fall can also damage or break a rail.
Stress risers caused by the seat post cradle when the sharp edge of the seat post cradle abrades the saddle rail can cause the rail to break. It is very important the seat post cradle is a minimum of 30mm long from front of cradle to rear of cradle. Cradles less than 30mm long will allow enough leverage that a impact from the rider or during crash could cause the rail to fail.
Some brands of seat post cradles break rails more quickly than others -- Syncros, early Control Techs and American Classics all used "straight cut" sharp edge seat cradles that create stress risers. These stress risers can be reduced by rounding the edge of the cradle with a file where the rail exits the cradle -- top/bottom and front/rear.
We also recommend that the clamping force used to hold the rail not exceed the seatpost manufacturer's recommended torque. Most seatpost manufacturers recommend seatpost clamps be tightened not more than 10 N/m for 6 mm bolts and not more than 25 N/m for 8 mm bolts. Excessive clamping force will stress the rail and eventually cause rail breakage.
A carbon rail is lighter than tubular titanium. Both carbon and titanium rails flex, adding comfort to the saddle.
All rails except carbon rails in carbon woven bases are inserted into the saddle base under compression (the saddle base squeezing the rail trying to make the rail shorter/more compact). The base is under tension (the rail is trying to expand the base making the base longer.) This compression/tension is what holds the rail in the base.
When the rider's weight/road vibrations/impacts cause the rail to flex, the rail actually moves in the base, momentarily relaxing the tension of the base and compression of the rail providing more flex and resulting better comfort level of the saddle.
The carbon rail inserted into a carbon composite or nylon composite base is inserted under compression/tension so has similar flexibility to tubular Titanium but is lighter by about 18 grams.
A carbon rail in a carbon woven base saddle is not inserted under compression/tension because the carbon woven base won't flex enough during insertion to allow it. The base will break before flexing enough to allow the rail to be inserted. The carbon rail in a carbon base is held in place with a super strong glue that eliminates the rail movement in the base which makes a carbon rail in a carbon woven base less comfortable.
Cr/Mo and manganese rails are lighter and flex more than steel.
Vanox is a proprietary alloy composite of stainless steel, titanium and vanadium, made in Germany. It is an ideal alloy for saddle rails because of its durability (not subject to stress riser -- where the sharp end of an unmitered seatpost cradle has been known to cause titanium rails to break) and is actually lighter than regular titanium rails (not tubular titanium, which is lighter yet). It's less prone to failure, is lighter and is slightly less expensive than all-titanium rails.
All Terry saddles are made with nylon composite bases.
You can make several adjustments to make sure your saddle is adjusted properly.
Set the height of the saddle so that there's a slight bend in the knee of the leg that's at the bottom of the pedal stroke. If the saddle's too high, your pelvis will rock from side to side; too low, and you won't get the best use of your leg power. Knees can take a beating from an improper saddle height as well.
The saddle should be level. Viewed from the side, the saddle shouldn't appear to be nose up or nose down. If the nose is tipped up, you'll feel a crunch in the wrong spot of your anatomy! Tipped down, and you'll be forever sliding toward the handlebars and bearing a lot of unnecessary weight on your arms.
Fore to aft saddle position should be set so that when a plumb line is dropped from the front of the knee of the fowardmost leg (with the crankarms in a horizontal position), it intersects the pedal spindle. This will give you the most biomechanical bang for your buck.
Your position on the bike is as important as the position of the saddle. If the bike doesn't fit properly, you may never find a truly comfortable saddle. The most common complaint we hear is that the nose of the saddle still places an undue amount of pressure on the rider, even if the saddle is adjusted properly as discussed above. If the rider's reach to the handlebars is too far, the pelvis can tip forward enough to put pressure on sensitive bits. By shortening/raising the handlebar to bring the rider into a more upright position, the pelvis will rotate back enough to move the rider's weight onto other areas.
If you've done all of the above, it still doesn't mean the saddle will be comfortable. (What?!?!) No kidding -- that old expression, "One man's junk is another man's treasure" applies to saddles, too. It might take some experimenting to find the perfect saddle. Rules are meant to be broken, so don't feel bound to any of the starting points above or to a saddle that everyone else thinks is great. It's your comfort, after all!
This is a tough question to answer since there are so many variables - rider weight, riding style, care given to equipment, climate in which equipment is used, where the saddle is mounted on the rail, if the rider wears cycling shorts or something else while riding and a host of other things.
With all that said, 5,000 miles is a reasonable amount of miles to expect from a saddle. 10,000-15,000 miles is at the high end of the scale. 15,000-20,000 is looking for rail or base failure. (All of these expectations can be severely reduced by an abusive riding style, extremes in temperature and one or more of the other things listed above.)
A saddle that is "broken in" should feel "softer" than a new saddle. The base hasn't been "seated" onto the rails; the foam hasn't contoured to the rider's sitting position; the leather is still stiff.
The saddle can continue to be ridden for many more miles if:
1). the cover isn't torn;
2). the edges of the leather cover aren't showing signs of wear through;
3). the foam under the leather doesn't have any "soft" spots indicating foam breakdown;
4). the edges around the soft tissue area aren't breaking down.
The only other thing that might happen is a rail breaking due to a stress riser caused by the seat post cradle (see question #1).
The rail can pop out of the saddle if it's hit hard enough; the base flexes one way and the rail another. Don't try to reinsert the rail yourself. It takes a special tool to do this right. Send your saddle to the address below and we'll inspect it and re-insert the rail if the saddle is still sound. The charges are as follows:
1). Rail popped completely out - $9.95 postage only;
2). Rail popped out on one side - $15 plus $9.95 postage (the rail has to be cut and replaced);
3). Rail bent or broken - $15 plus $ 9.95 postage;
4). Replace rail with tubular titanium rail - $30 plus $9.95 postage.
Carbon rails cannot be replaced or repaired.
Don't send any money! But do send your snail mail address and email address. We will repair the saddle (if possible), return it and include a letter indicating the amount owed.
ProNet, Inc.
910 N Cambrian Avenue
Bremerton WA 98312
Our saddles are best cared for by washing with water and a good bar soap. Wipe it with a damp cloth and air dry it. Don't use any treatments or chemicals other than water and a bar soap. Many cleaners use petroleum that will cause the glue that holds the leather to the foam to soften and loosen. They can also cause the foam to expand and distort.
This may be caused by the rails rubbing in the seatpost clamp. Remove the saddle from the bike, lube the rails and also the seat post clamp cradle nut/bolt. The squeak may also come from the rails rubbing where they join the saddle base. This can be helped by removing the saddle, turning it upside down, and applying silicone lubricant to the rails so it can run into the holes that hold the rails. Please don't use a petroleum-based lubricant; it can damage the leather and the glue.