Something wrong with my bike..?
Comments
-
Sewinman wrote:
Was having some weird skipping with the Wilier, checked the casette and I have shreared off half the teeth on the smallest cog! Its done about a 1000 miles max 
How did that happen!?
Speculation time!
Your smallest sprocket is very small- 11 or 12 teeth. It is said that very small sprockets are more vulnerable to wear than larger ones. Back in Ancient Times (1970s), when people made bike parts to last for several years or even decades, instead of one season's racing, it used to be claimed that a 13T was tough on chains etc....
You are using small sprockets with your smallest chainring to get the gear you like. This is increasing chain angle, but more importantly it is increasing the leverage your cranks are delivering- so your chain tension is particularly high, increasing the strain on your small sprockets.
Modern sprockets are very thin, so you can squeeze a dozen into a cassette. They don't have much lateral strength.
Put all this together and with a little wear and a mis-shift under load and the teeth start to give way. Once one's gone the rest have to carry even more load.
This seems plausible to me, but then I'm a bit skeptical about modern groupsets!
Right- I'm just off to go and throw my clogs into a loom.... :-)
Cheers,
W.0 -
WGW - I think you are right.
So a question - given that my favourite gear was the the worst combo for wear, could i get a different casette so that sort of gearing would be less extreme?0 -
Sewinman wrote:WGW - I think you are right.
So a question - given that my favourite gear was the the worst combo for wear, could i get a different casette so that sort of gearing would be less extreme?
If it's a triple, there should be a gear on the middle ring which overlaps your favourite, which will be nearer the middle of your cassette. If it's a double, then what is this little ring you speak of?0 -
Sewinman wrote:WGW - I think you are right.
So a question - given that my favourite gear was the the worst combo for wear, could i get a different casette so that sort of gearing would be less extreme?
Your 'favourite gear' is, as Jonginge said, available elsewhere in your existing chainring: cassette option list. You don't need to change cassette - just use the one you have properly. No extreme chain lines; bad bad bad. Bad Sewinman
Faster than a tent.......0 -
Rolf F wrote:Sewinman wrote:WGW - I think you are right.
So a question - given that my favourite gear was the the worst combo for wear, could i get a different casette so that sort of gearing would be less extreme?
Your 'favourite gear' is, as Jonginge said, available elsewhere in your existing chainring: cassette option list. You don't need to change cassette - just use the one you have properly. No extreme chain lines; bad bad bad. Bad Sewinman
:oops:
It is a double at the front and a compact cassette at the back. You say that, but I don't think it available! If it is available then would it not be an equally extreme gear, but just going the opposite way?
I am wallowing in my pit of ignorance.0 -
Sewinman wrote:Rolf F wrote:Sewinman wrote:WGW - I think you are right.
So a question - given that my favourite gear was the the worst combo for wear, could i get a different casette so that sort of gearing would be less extreme?
Your 'favourite gear' is, as Jonginge said, available elsewhere in your existing chainring: cassette option list. You don't need to change cassette - just use the one you have properly. No extreme chain lines; bad bad bad. Bad Sewinman
:oops:
It is a double at the front and a compact cassette at the back. You say that, but I don't think it available! If it is available then would it not be an equally extreme gear, but just going the opposite way?
I am wallowing in my pit of ignorance.
If that's the case, there will be less overlap, also doubles suffer less from the chainline than triples. You either need a cassette which has bigger sprockets, or a compact chainset, or just get used to pushing a higher gear.0 -
Yes, if you need it. You probably don't.Sewinman wrote:WGW - I think you are right.
So a question - given that my favourite gear was the the worst combo for wear, could i get a different casette so that sort of gearing would be less extreme?
What are your actual chainring & sprocket sizes?
We need to put together a gear chart, which allows you to identify the ratios you like to use, then you can set up the drivetrain to achieve them optimally.
Ratios can be expressed in several ways, but it doesn't really matter as long as you're comparing like to like. I'm most familiar with "Gear Inches", where you convert your gear ratio to an equivalent wheel diameter. But you can use development (metres on road per crank turn) or gain ratios, which take crank length into account.
At any rate- post your chainring & cassette sizes (count 'em, if you have to) and we'll go from there... There's almost certainly a BigRing/MiddleSprocket combo that's very close to what you were using, and if not then you can choose a new cassette that provides one.
Cheers,
W.0 -
Ok, thanks. I am in grey old Milton Keynes today but will post it up once back in town.
Cheers!0 -
This is where it starts getting a bit geeky. You might need to count the actual teeth on all the sprockets,
"Compact" most likely actually refers to the front chainrings, meaning they have 50 and 34 teeth, rather than the 53 and 39 from a Double. The numbers will be stamped on them though, so have a look.
At the very least you'll need to count the number of teeth on the smallest cog at the back. It's either 11 or 12, but one tooth there makes a difference. Unless someone knows a web page I've never found, you might actually need to count the teetth on all the sprockets.
If it's a compact, then your favourite gear has a "gear ratio" of either 6.1 if it's 11 teeth at the back or 5.6 if it''s 12. You're aim is to find a gear using the big chain that has the same "gear ratio". With 50 teeth up front you'd need either 16 (to replace an 11) or 17 (to replace the 12)
With a Double the gearing is higher, but it works out as 15 (instead of 11) and 16 (instead of 12)
You'll need to count the teeth on the rear sprockets to find out which one of them has 16 or 16 or 17 teeth on it, but it will be on of the middle ones, and should be a nice straight line from the front chainrings to the rear, much better for the chain.
There is a problem though. There is usually more than 10 teeth difference between the smallest and biggest cogs. To fit this range in some numbers are skipped. You're biggest two cogs might be 23 and 25, with no 24. A cassette with cogs with 15, 16 and 17 teeth isn't too common, at least one of them is usually skipped.
The other approach is to ride down a bit of road in your favourite gear at your prefered cadence and note the speed. Chainge the big ring, match the speed and see what gear you need to be in to do that speed at the same cadence.0
