As a beginner, I know very little about gearing on bikes.
I read the post about crank sets lasting 1500 miles and was surprise as my set has missing tooth tips on the middle gear after 500 k. I am riding a diamondback sorrento with 24t, 34t,41t. The 41t I'm not quite sure of it could be42t. My question is can I get gears that retaian a 24t but raise the other two so that my speed would be higher than about 28 k on flat roads?

Charlie

You can get almost any kind of gearing you want. It depends on the type of cranks you have and the bolt patterns. Also on some cranks the chainrings are bolted together which means you can't change them. You would need to buy a different set of cranks with changeable CR's. Your local bike shop (LBS) can advise you either way.

Welcome to biking! You'll find a bunch of kids here in their 60's.

Cranks and chainwheels should last much longer than 1500miles.
You probably have low-mid range Shimano chainrings which are made of soft metal and prone to chipped teeth. Better quality rings dont suffer very much from chipping.

The gearing you want is a sensible touring range, ideal for trails and road. You may be able to fit bigger chainrings to your current crank, but ideally you need a crank with a Bolt Circle Diameter (BCD) of 110/74mm to fit chainrings of about 24/36/48.

You can still find these but they are not a current standard.

If you do get a new set of crank, look for a forged Al one, that is compatable with your bottom bracket, and of the correct length for your legs. The best model of this type is the Specialities-TA Zephyr, but it is very expensive. I believe Richley make a nice model as well.

If your chainrings only have 500 k on em, and it's your middle ring, chances are they're supposed to be like that. Most companies have different tooth profiles and ramps or pins on the sides to help improve shifting. Does the chain ring look like it's been ground down in one area? If you closely at newer bikes you will see the same pattern.

Did you grind on some concrete or just normal riding? If you don't remember any significant hits, chances are your chainrings are fine!

L8R

I agree. When I selected a new 40T middle ring at a bike shop (to get a different gear ratio, not because I had worn out my 38), I was taken aback by the two pairs of ground-down teeth. It took me (and the salesman) a moment to realize that this had been done deliberately at the factory, and the ring was indeed brand-new.

If your crankset is Shimano or Shimano Hyperglide compatible (some Suntours) you probably don't have any problem right now. Shimano chainrings do not have uniform teeth. The teeth, especially on the middle chainring, are all different shapes from very tall and pointy ones to very low flat ones that do look like they are broken in half. They are designed this way to promote smoother shifting. This is probably what you are seeing. I thought the same thing when I took a good look at my chainrings after just a few hundred miles.

To answer your question, yes, you can put a larger big ring on with a few more teeth. HOWEVER, you can run into a capacity problem. Front derailleurs can handle a certain range of difference between the size of the smallest ring and the largest ring. You can also run into problems if there is too much difference between two adjacent chainrings. The rule of thumb I have heard was a 12-tooth difference (say your 34 middle and a 46 outer), but in practice 14 will usually work fine but in your case you would need to be aware of the possible max your der will handle. Your LBS would be the best advisor on this.

I currently run a 21-speed 48-40-24 / 13-26 "1.5-step plus granny" with old SunTour XC derailleurs on my mountain bike, having recently replaced my original 28T inner ring with the 24. To obtain a smooth, fast 24-40 gear change, I do have to pedal gently while paying attention to how far I move the shift lever, and I need to avoid trying to shift across too many rear cogs at the same time. In practice, this has been a problem only when I frist start off after storing the bike in the (minimum-tension) small-small combination. In contrast, the 28-40 upshift was almost idiot-proof.

The Diamondback Sorrento, if I recall, is commonly sold in department stores, and is of questionable componentry. the missing tooth tops are likely deliberate, and I'll bet that the chainrings are riveted together, making chainring swapping impossible. This is just one of the reasons why you should never buy from a department store. there are many other reasons, which you probably have already experienced, or soon will.

Yep, I used to sell them. The rings are definately meant to be like that.

If you want to increase you chainring size go for a Shimano Alivio chainset 44-32-22 combo. They cost about £35 in the UK so say about $50 in the US. You'll find that you should be able to retain your current bottom bracket as well.

Thanks to all for your advise. A word to velosnob I did buy my bike at a LBS, and yes it is inferior in quality but then I had no idea if I would ride enough to make it worth my while buying something expensive. I now would like something better but try to convince my wife that I need one is another story. I was reading this forum before I bought so knew the opinion of department store bikes.

Charlie

Charlie,
Most of us have been there. I bought an inexpensive bike initially because I didn't want to spend a bunch of money then lose interest. My bike had some of the most inexpensive component available. Once I really got into cycling and decided I wanted better stuff I started an upgrade program that has turned my inexpensive comfort hybrid into a pretty darn nice commuter/tourer that I love and would take anywhere in the world. Maybe in total I have spent a little more than I would have for a road bike with better components to begin with. But I now have a bike that is just about perfect for its intended use, and the knowledge of bicycle mechanics I consider priceless.

From total ignorance about a year and a half ago I have learned to do everything you can do to a bike. I recently built a bike from scratch. All this stuff is really kind of easy once you do it and get the right tools. One of the most intimidating things to me was the the whole crankset/bottom bracket system. Heck, lately, I've been swapping cranksets and trying out new chainring combinations about once a week. After riding it unpainted for a few weeks to confirm the fit, just yesterday I stripped the bike I built so I could take the frame to be painted. Took less than 1/2 hour.

So you don't have to apologize for starting with an inexpensive bike. They get you started and can be excellent learning laboratories if you want to learn. Any components you put on your inexpensive frame can be moved over to a better frame someday. Since you will buy a piece or two at a time you can spend a little more and get better stuff.

I really don't think you need a new crankset just yet, though.
Regards,
Raymond

Halfords done some research a few years back and found 80% of customers who purchased bikes over £150 came back within 2 years to upgrade to a £600+ bike.

Examine the "missing" teeth. You may notice that they're in clusters of two and three and are spaced 180 degrees apart; this is how many chainrings are manufactured so as to facilitate upshifts from smaller to larger rings. Different companies have different names for it but this is an increasingly common feature of cranksets and chainrings.