Hope XC4 caliper advice

[Nick C]

Second time today for requesting advice.

Today I received, amongst other things, a front and rear pair of XC4 calipers and Pro levers.

Now I'm certain that both sets of calipers need servicing, but certainly one of the pistons on the rear seems out of alignment. I've just shot off an email to Hope asking for service advice, but in the mean time can any home mechanics (kitchen table type) tell me if it's easy to self service these and what tools would be needed?

The front calipers will fit straight onto my Sid fork, but the rear are going to need a bracket, how does one go about finding the correct bracket?

Sorry if the questions seem a little 'dumb', these are actually my first set of disc brakes!

I'd also be interested if anybody has a locking key/spanner for the ring that holds the discs to the hub, although I'll be posting the same question in the 'wanted' forum.

Pictures of the brake and lever combo, including the dodgy piston:

 

[dbmtb]

Looks like the pistons need resetting - which is good practice anyway when fitting to a new bike.

I'd suggest that
1) you unscrew the reservoir cover on the lever.
2) Carefully prise the pads back outwards with a large flat-head screwdriver where the rotor would go. BE CAREFUL - you will probably squirt some dot fluid out of the reservoir at some speed - so wear eye protection. Nake sure all he pistons have fully slid back into their sockets.
3) replace lid.
4) check all pistons are moving evenly by squeezing lever gently.

If the pistons are out of balance you might need to service the caliper - clean and oil the pistons etc... A big job you might not want to embark on.

 

[cornholio's RC200]

I recently had a problem with my XC4s (stuck pistons) and sent the offending caliper to Hope to see if they could get them out. I got a call from Hope the next day saying that they don't carry spares or work on them anymore. The caliper arrived back two days later. Unfortunate but great service from Hope.

Yours doesn't look as bad as mine; the rear two pistons on mine are stuck flush with the caliper thus rendering them useless. You might want to put some new pads in them though.

There is an exploded diagram and servicing instructions on the Hope website but I'm just trying to find a suitable tool at the moment to try to get the pistons out. Mine need blowing out with a shock pump or airline and then the pistons unscrewing. Seal kits are available from CRC if you need them.

 

[Nick C]

Thanks for the info guys.

I downloaded the diagrams from Hope last night and their reply to my email confirms they don't service the XC4 or carry many spares.

I've actually just been on the CRC website and bought a spare set of seals etc for both sets of calipers and levers. I'll pick up some oil shortly too.

I also spoke with Lee at Grizedale Mountain Bikes, he says they used to run the XC4 on their old bikes and had endless problems with pistons sticking out. He said they used to clean the side of the stuck piston, push it back in, pull the lever and clean again and then repeat a few times. Obviously a short term fix. He also said if I'm having problems and have the parts, they would be happy to fit them for a small handful of pennies.

I'm still unsure on the mounting bracket for the rear. Hope said it will fit straight onto the frame without a bracket, I think the chap failed to notice the age of my bike as this clearly isn't the case. Lee stated that it would need an IS mount of some sort, something I need to research clearly.

 

[Nick C]

Ok I stupidly thought the following lugs were designed for disc calipers, as this would be a ridiculous place to put them, am I fighting a losing battle hoping to run a rear disc brake on my Trek? :cry:

 

[dbmtb]

If you cover the postage and material costs, I'd be happy to have a go at saving these. But the mounts on your frame are mudguard and rack fittings - not disc mounts.

I reckon I could make them work again. But if I were you I'd just pass them on...

 

[8690q]

Those are Treks bright idea for mounting discs.

You will need a bracket to bolt on to those two holes which then gives you the 51mm IS mount.

These used to be available from Trek but not sure if they'd still have any these days. Maybe you could try a long established Trek dealer in case they have some kicking about. I'm pretty certain Gary Fishers of the same era have the same mount.

Edit:

I found it http://www.cycleworld.co.uk/product/998 ... nt_Adaptor

If it's not this it's awfully similar :?

 

[Nick C]

That looks very similar to an image I saw on the internet of a Trek running discs on the rear, sadly the image was too small to make them out exactly, but the arm seemed to be long like the one on that page. I wonder how much flex there is with it? I think for the price it will be worth purchasing one and if it doesn't fit it can sit in my box of bits.

'dbmtb' thanks for the offer, but as I've ordered all the spare parts for them, I'd like to give them a go myself and a reasonably local bike mechanic has also offered to build them if I get stuck.

 

[Neil G]

I was going to suggest getting someone to make a braket up, wouldn't have thought it would be that difficult

 

[Nick C]

You're probably right, but the chances are it will cost more than a tenner.