Chainrings

Contrary to a couple of posters above Stronglight make chainrings in non-compact sizes for compact bcd. Their CT2 rings are well regarded and go up to 53 tooth.

I've got them from dotbike (link above) and a french online shop i found, but can't remember the name of at the moment (they must have either been cheaper than dotbike or dotbike didn't have stock at the time), before.

If you need new chain rings, have a look at hese before you buy:
http://www.dotbike.com/p/5085

Relatively cheap and available in a good range of sizes

From what you have described yours chainrings are worn. Chainrings will last a long time unless they are run with a very stretched chain, it's worth getting them looked at by your lbs, and also getting a chain wear gauge so you can periodically check your chain.

My money is on rear mech alignment make sure that upper jockey wheel is perfectly in line with the sprocket !

If your gears at jumping forward under load and you've replaced chain and cassette together in the correct way, the only 2 outcomes to this are 1) your chain rings are worn too although this is very unlikely. 2) the pawl springs inside your freehub have worn out and are failing to engage with the ratchet consistently. (Surprised nobody on here has considered this but as a mechanic this is a very common cause of gear slipping) the amount of people that have asked me for new cassette and chain when its the freehub causing the problem is simply staggering. Was it doing that before you changed everything? If so that's where I'm putting my money..

A) you can go up to 52 but will need to raise the derailleur a few mm and may need an extra 2 links on the chain. Nobody makes higher than a 52 for a compact chainset

B) providing BCD is the same compatibility shouldn't (in theory) be an issue although its best practice to match the brand of chainring to the brand of crank

C) compact just means that both rings run the same (smaller) BCD but any road groupset bar Campy will most likely run double. It doesn't need to be compact specific, just have the same BCD..

Hope that helps..

George

oops sorry just noticed that you said you replaced the cassette as well.

Re changing the size of the chainrings - most rear mechs have a maximum number of teeth difference they can cope with. This depends on the spring in the mech, the cage length etc. So it would be worth finding the manufacturer's spec on the max capacity of the rear mech then see if it will cope.

If the chain is still slipping it's probably adjustment of the mechs or maybe the cassette is worn (if the chain was well worn the cassette could be shot as well) - it can be hard to tell if it's slipping at the front or the back.

Could be worth a trip to the LBS before you spend a lot on new chainrings etc

Ah that's a lot of questions! First off 3000km isn't much for chainrings, I would have thought you would get more than that.

a) and c) If you currently have a 'compact' then you must replace with 'compact' as the so called BCD is different to a double. This is the diameter of the chainring bolts ring with respect to the axel.

As for manafactuer, most will work with each other although I have experience with Campagnolo. I have SRAM on my bike and replaced the worn chainrings to Stronglight and had no issues. Aesthetically it didn't look great though. Since then I moved to a ROTOR crankset.

One last advice, shop around. Chainrings can be expensive. I bought my Stronglight from Ribble at a reasonable price.

Where is the chain slipping? Is it slipping at the front?!

No way have your chain rings gone at 3000 miles!

a) Yes you can increase teeth with deraileur, chain may become too short though.
b) Chainrings will say what chain they are compatible with
c) you do ride a double, but you ride with 34/50 the BCD will be 110 (double refers to the two chainrings compact doubles will have a BCD of 110 and standard doubles a BCD of 130)

But yeah, I doubt your chainrings have gone at 3000 miles, might be a rear derailleur setup issue.