I have XT front and rear. Prob 3 years old. They feel nice and firm, well bled etc.

I got them to replace some X2s and they were comparable in power.

This week whilst rebuilding my wheel, I rode my wifes bike to work. It has old HOPE Monos and there was nearly and OTB when I braked riding one handed.

Clean discs and new pads or is there something else to check? The pads have a lot of life left and are £15 an end here so don’t want to buy them needlessly. I can’t see any sign of a leak at the caliper.

I have disc cleaner and 98% isopropronoyl (sp?) alcohol. Which is better? Use both? Should I remove the discs from the hubs and soak them in the alcohol then remove, dry and spray with the aerosol cleaner?

Thanks

My findings after using a lot of Iso Alcohol is that it’s a good cleaner but not a degreaser. I’d use steel wool or Scotchbrite pad to remove all previous brakepad residue, wash discs with washing up detergent, dry and then use the acohol. Fit new pads and follow the breaking in procedure. This bit’s important as you’re laying down a new layer of brake pad material on the disc. This provides “adherent friction” which along with abrasive friction stops the wheel from turning.

D.

thanks Dave.

How old are the disks? I was having similar problems with my XT brakes, would bleed them and they still felt spongy, then I got a spare set of wheels with new disks and all the sponginess disappeared. Promptly got a new set of disks for the old wheels.

The disks had lost just over 0.5mm, I think Shimano disks are 2.5mm when new.

the disks are a few (3?) years old but the conditions here are kind to components.

They’re HOPE rotors. I don’t have callipers to measure them but they doesn’t seem to be much metal worn away ie. no ridge from the braking surface to the spider.

The brakes aren’t spongy. They’re rock solid. No rubbing and minimal travel from extended to the bite point – just the way I like it.

The rotors are 203mm and 160mm. On a hardtail and I only weigh 73kg. I should be stopping on a penny.

The issue is a lack of power once applied.

i had that with XT’s, cleaning, degreasing, burning etc all had limited temporary effect.

swapped the disc. all the issues I had went away.

Really jambo.

Sounds expensive and annoying…

After 3 years and if you’re confident that the rest of the brake is sound, my experience suggests it’ll be worn discs. Shimano discs seem don’t seem to wear down evenly across their face, but seem to scallop in from the edges. What this means is that there’s no pronounced ridge from wear and if you put new, perfectly flat pads in, they feel terrible, because until the pad wears to the shape of the disc, you’re only braking with a section of the outer part and innder part of the disc. You should be able to see the tracks on the disc if it’s this.

The other way to look it to find a known straight edge like a metal ruler or the sliding arm of a micro meter across the disc. You’ll see the scallop this way.

Ooh. I’ve just seen that you’re using hope rotors. My advice about measuring the rotors stand, but AFAIK, hope rotors are thinner than shimano. Since shimano use servo wave to modify the force through the lever, maybe the way power is being applied to the disc is in a sub optimal position?

Thanks.

I’ve always used HOPE rotors and when I first rode the XTs (and for a good while after) I couldn’t help but wonder how I’d justified the extra expense of HOPE brakes.

I’ve access to a 203mm HOPE rotor (on my wife’s bike). As I know it works well, I’ll give it a go. With new pads in it should eliminate or confirm the disc being the problem. On my way home soon and have picked up a couple of pairs of pads.

Could be the classic microscopic caliper leaking seal/s.new calipers is the only cure.
Do they squeal like little piggies?

Scrub/scuff disks with wet and dry and soapy water, chemical cleaners can only do so much, they won’t remove baked in dirt.

Sometimes you have to take a brillo to the frying pan.

@steffybhoy

Rear squeaks slightly. Not enough to bother me when riding. Front doesn’t.

It’s dry, dusty and wonderful riding here. I realise you sai “microscopic” but would I see any kind of oiliness around the calliper if your suggestion were the problem. I was just able to blow them clean*.

*wife went out with my new pads in the car.

Had the same problem with M785 discs. It turned out to be a tiny weep from the caliper seals, causing re-contamination of the discs and pads. Swapped to new SLX calipers and the problem was solved.

Mine are 785s…

Maybe it is a dud calliper.

Mmmm.

I put new pads on and swapped the disc for my wife’s.
I also put new pads in mine.

Her brake is still lovely, mine isn’t. It’s rock solid ie. well bled. It just lacks power for the force applied at the lever. It wasn’t like this new. If anything it was grabby / snatchy / too powerful.

Anything else worth checking or is it new caliper time? *eye’s up her front M4…*

You mention new pads but have you bedded them in properly? It can pretty much only be the pads from what you describe. That said the only disks I’ve eve had issue with on my Shimano brakes is Hope ones.

There is a simple answer.

It has either the term ‘Hope’ or ‘Magura’ attached to it.

😕

I gave up on three old sets of Shimano that exhibited similar lack of performance that you describe. They all got a few years in and slowly faded, and nothing seemed to rejuvenate them past one or two rides. I still have two sets Deores on our family bikes – but they are less than a year old and came with new bikes, and one old set of SLX is going still (least used bike), but other than that we are rocking Old Skool Hope Mini’s (17 years old and still work!) or two sets of just brilliant Magura MT2’s.

The MT2’s have a huge pad retraction, great power and so much modulation. I’ve crashed twice on them, once leaving a mark on the bars across clamp and they have survived, so concerns about the strength of them seems misplaced. Ive bought both (brand new) sets off PinkBike from folk changing them to Shimano…

nickjb – You mention new pads but have you bedded them in properly? It can pretty much only be the pads from what you describe.

Realised I hadn’t! 5 – 10 hard stops on my driveway and they’re fantastic again. Not as well modulated as HOPE but as powerful as the M4.

I’ve ridden the M4s again and the front isn’t as good as it was before. I think it was the disk and pads. Hopefully not a leak in the XT calliper. I say hopefully but I do really like the look of the Saints and £50 on CRC seems reasonable.

MattO&A – Yep. The Inbred has old M4s and even older Mono.

Hi Mike, We're really sorry that these 15 year old brakes have required bleeding 😉 Hope you can forgive us.

— Hope Technology (@Hopetech) October 28, 2016

Just had a similar problem with my front 785. Got to the point where it barely slowed me down. Cleaned rotors and replaced the pads but no improvement. Replaced the caliper and all is well. I assume there was a small leak on the seals. New caliper from crc comes with new pads so works out not too bad price wise.

Even better value if you get the slx caliper, which is identical except for the colour and logo.