I bought a secondhand spesh epic last year and have had some problems with the elixirs which are factory fit. i'd appreciate some advice on how to resolve the following…
1. front pulsing – new pads fitted and caliper aligned [ish] first ride out and the problem is still present. checked the disk for flatness and it looked like an old vinyl record so i get a new one rather than try to realign it – thinks; i'll leave that for another time. when the disc is loose on it's bolts it's perfectly flat but when the bolts are tightened it's not straight.
2. the new disc doesn't sit centrally either – how best should i centre it, i thought of using countersunk screws to centre it then replacing with the proper screw once semi tight – would this work.
3. what is the quickest way of aligning the calipers, tried the business card trick but when you tighten the bolts it skews the caliper and deforms the disc.

is it time to give up and go back to vee brakes/take it to an "expert"/throw them in the bin/use public transport etc etc

Here are some ideas from a bloke with old 5s & 3s.

Pulsing – Are the pads overlapping onto the spokes of the disc?Pack out the caliper with washers.
Disc not centeral – To the caliper centreline? Push the pistons fully in. Pump them out with the lever with the caliper loose. If one piston has come out further than the other then try lubing them with B fluid and working them in and out. If one piston is still out further than the other then repeat but this time as you pump the lever bias the caliper to restrict the movement of the non sticking piston(pressing the pad against the disc with some support to the other side of the disc as they are quite week in this direction).
When alligning you need to pump the lever until the pads clamp the disc GENTLY and then tighten the caliper screws a tiny bit at a time alternately. Make sure the bolts have washers and that they can rotate. Clean and lube the mating surfaces.

Hope I am not teaching you to suck eggs!
Good luck!

thanks imp 999 – but
Pulsing – Are the pads overlapping onto the spokes of the disc? they are overlapping but they all do apparently – it seems that avid don't make a disc which has the same sweep area as the pads and this probably assists in cleaning. but the pulsing is a lower frquency indicating a disc alignment/straightness issue
Disc not central – To the caliper centreline? no to the wheel – i'm not certain of the technical term but if you spin the wheel the disc doesn't appear to be round allthough it is – apologies for the pigeon tech speak!

try something other than avids?

i think pulsing is an avid problem generally.
ive hard of it before, never had it on hayes or shimano (though did on a hope with a wavy rotor once)

never noticed a rotor not being central, but may well have happened, countersunk bolts sounds like a good idea, but cant imagine it being more than half a mm out, and wont braking settle it into the bolts anyway overtime?

aligning the caliper, i just loosen the mounts, pull the brake on, and gently tighten the caliper up again, a bit at a time, alternating top and bottom….

Photos would defo help, I have had juicy 7's and currently have juicy 5's none of my avid discs overlap onto the spokes.

I do find that a little caliper service is required once in a while, including bleeding – do you have a bleed kit?

Basically what imp999 said but I find it easier to push the pistons back whilst the bleed screw is open, so I tend to do that operation as part of a bleed.

Discs

The disc off centre thing sounds a bit interesting. If you are sure the disc isn't warped then:

1) Discs: try removing the disc, and clean the mounting surfaces and edges thoroughly, check the back of the discs where they make contact and clean them too. Check the bolt holes in the discs make sure they are clear, check the bolts make sure they are not bent or have any lumps on them.

2) Hubs: clean as above and check the threaded holes in the hub, ensure the bolts go in straight and none of your threads are threaded or drunken. If there is a problem you can get an engineering shop to retap and maybe helicoil.

3) Fit the discs. Make sure you do the discs bolts up in small steps, in an opposite pattern, so start at the top (12 oclock), then to the opposite at the bottom (6 oclock), move around clockwise from the top to the 2 oclock, then 8 oclock, then move to 4 oclock and then do 10 oclock, repeat each one gently until all are tight.

If its still off centre then check the gap between the inside edge of the disc and the hub using feeler guages, if there is any gap then measure each gap and make sure its the same.

Caliper

1) Remove the wheel and pads, make sure the inner area of the caliper is clean, i use a baby teat brush, small wire thing with plastic bristles, and washing up liquid warm water.

2) Apply some b lube like imp999 said, attach bleed syringe to caliper and then push caliper all the way back in, put the caliper bleed block in and do the bleed thing.

3) Put in brake pads (and the all important pad separator spring_, and wheel with disc.

4) The caliper should be self aligning but I find that the little cones on the bolts can sieze up, so strip the bolts off, clean and apply a little lube, grease or small amount of oil to allow them to move freely until they have been tightened up.

5) Then with the reassembled lubed caliper go through the alignment procedure as described above by the venerable imp999.

Please do send fotos so we can see if there is anything obvious..

Whilst what Olly says may well be true, I've personally never had a pulsating problem with avids, I have the juicy 5s on my inbred and they feel great, a juicy 7 on my bullit was great until I decided to up the anti with some avid codes which are also great so far. I'm sure its one to watch out for but I dunno if changing the brakes rather than solving the problem would suit your budget..

Maybe you have an iffy hub. If the bolt holes are off centre and if very iffy they could be different heights that would explain the pulsing the off centre disc and the warping when tightened issue.

Do you have another wheel to try with it?

I'm with Andy. If the rotor is flat off the hub then it's the hub warpping it. Try the new rotor. If it happens again then it's the hub. If it doesn't then you've got a dodgy rotor.

As for setting up Avid disc brakes. Make sure the CPS bolts and washers are loose. Squeeze the lever several times and hold to clamp the rotor. Whilst still holding the lever visually check both calliper pistons are roughly evenly 'out'. If they are tighten the CPS bolts gently – not fully tight. Release the lever, spin the wheel gently and visually check the brake is running free. If it is then pull the lever to clamp the rotor again. Then tighten the CPS bolts up 1/8th of a turn at a time, alternating between top and bottom bolts. When the bolts are tight then release the lever and check the brake is running free.

May sound faffy but tightening the bolts a bit at a time and alternating which one you tighten stops the calliper from being pulled out of place. This is true of any make of calliper.

guys – thank you for your help on this. i will try and fit in some fettling time this week – not sure when yet as it's all gone a bit hectic since christmas. will definitely get the chance at the weekend so will report back on my findings.

thanks again and look forward to more challenging [to me] questions. *thinks* i could learn how to strip and rebuild the whole bike with this sort of help using that there forum gadget…

are there any books you could recomend – i learnt a lot from haynes manuals in my youth?

I dunno about books, I reckon if you search on here or other bike forums you will find most of the stuff you will have to deal with has already been answered. Although a quick search didn't find this problem but maybe a deeper look would find it. Otherwise just ask, plenty of armchair experts here..

I think what the others above said about the hub being the problem may well be a place to look. Whilst I would be pretty surprised if the hub was bent/warped. Its possible the mount holes are off (or threads as I mentioned above) or just sloppy so the disc does not centralise.

If you were in Exeter I would happily take a look at it for you..

Park Tools is pretty good for repair info:

http://www.parktool.com/repair/readhowto.asp?id=142

Nobody seems to have mentioned the geniune avid rotor bolts have a shoulder that fits into the hole a bit more snugly than a normal bolt would,might be worth checking yours.Second the advice on tightening the rotor evenly, tighten opposing bolts sequentially, rather than going in a circular fashion.

i've got a brand new genuine g3 rotor still in the shrink wrap and i wouldn't describe it as a shoulder more like an unthreaded bit it still allows some "rattle" space prior to final tightening. had a quick look this evening and this is what is causing the centreing issue i think – will need to try the feeler gauge method to centre it on the hub… more news to follow me thinks

If you havent got a shoulder that's yer problem. Disc bolts with shoulder look like this, see the little shoulder between the threaded bit and the bolt head. They are available here : crc:

they definitely haven't got the same shoulder halfway between the thread and the head like these. crc "out of stock" but stock email requested, i think i can wait a few days.

thanks coatesy and toys