Daft question of the day...possibly

Newfish

Hello,

I've just fitted my new m785 brakes and m770 shifters. When I ordered them there wasn't an option for which brake was which side (front right etc). As it turns out they are the reverse of what I had before (and always had) rear brake left hand, front right hand.

Now the cables are too long anyhow so I have to shorten and rebleed them, however (silly question alert) can I swap the cables over between levers? Having just spent £130 I want to be sure first.

Thanks in advance.

Chunkers1980

Yes. From the Germans I take it.

Newfish

Thank you. Yes from Rose Bikes, Deore XT BR M785 fronts £60, backs £63!!

The Rookie

HOSES.......

Yes and the Shimano techdocs include a hint on how to do it that usually means you can escape without rebleeding....

Newfish

The Beginner wrote:

HOSES.......

Yes and the Shimano techdocs include a hint on how to do it that usually means you can escape without rebleeding....

Yes, hoses, thank you for the correction, I have already had a look at the Shimano Techdocs and it looks doable, have also ordered a bleed kit from Epic solutions, so if it all goes pear shaped I can rebleed them. Thats my day sorted then...

Newfish

Right, I have a new question if I may. I have changed the HOSES over, and reduced them in length too. Had one minor sketchy moment when one of the callipers came out a little far but got it back in ok.

However I have noticed something odd, the rotor on the back (160mm) doesn't seem to sit as far in the calliper as it did in the old one. Could this be possible? I spoke to my LBS mechanic the other day when I put a bigger rotor on the front. He said that as long as the rotor is using the entire pad that is fine, especially to the outer edge, if it is not it will wear in such a way that the pads will eventually touch and the brake stop working. Now this makes perfect sense, however I am a bit puzzled as to why the rotor isn't using the entire pad on the new brakes. I haven't changed anything other than the calliper, and there are no spacers to put in or remove to make the calliper sit further down.

Any ideas, or do I just need either a smaller adapter or a larger rotor. Its 'short' by about 2.5mm, so not masses.

Any ideas appreciated, although I don't think its Wiggles fault just yet.

cooldad

What did you replace? Avids? Are you still using the Avid washers?

Newfish

No it was Tektro Drako's. There were no spacers before and no spacers now either.

The Rookie

Photos.....should be a straight swap with no issues.

Newfish

Well thats what I thought, I shall take some photo's and get them up.

Newfish

Right then, here are the photo's.

In this one you can see where the rotor sits just below the top level of the two braking surfaces of the pads.



In this one, you can see the calliper and the mount. What I think I need is either

1 - a rotor that is 3mm bigger. or
2 - a new adaptor that is 2-3mm shorter where the rear bolt attaches the calliper to the mount.



What I have done so far...

1 - Bolted the new calliper on exactly the same as the one that came off was.
2 - Unbolted ALL 4 bolts (calliper and mount) to see if there was any lateral movement. There wasn't.
3 - Come on here to ask you knowledgable people to see if there is a solution that I'm not seeing.

The solution I have come to is one of two, grind down the end of the mount, retap the thread and bobs your uncle. I don't want to do this.
or two, get a new mount. this is the one I think I need but I need to know the distance between the hole that the bolt goes through to mount to the frame and the top of the bit where the calliper attaches.

DCR00

im not convinced this is that much of a problem

are you 100% that your old calliper didnt sit like that as well?

Newfish

I don't know if the original ones did this, but I don't think so. The rear pads, which I have replaced three times since owning the bike, never had a ridged wear pattern but were smooth all over.

I don't know if this will be a problem but was told by my LBS when I fitted my new front rotor, that it is very important that the pads wear evenly all over otherwise eventually the bit at the top that doesn't wear at the top will meet the other pad and the brakes will stop working.

DCR00

given the tolerances that seem to be suggested by the pic, i think you would have replaced the pads before it got to that stage anyway

Newfish

Rotor is probably 2mm or so, pads 3mm each or so. So 1mm wear on each pad an they'll touch. Surely there's more life in them than that?

DCR00

Its not quite a simple as that

You may get uneven wear on the pads, but for the pads to touch i think the rotor would have to wear at an equal rate as the pads, and that just isn't the case

Newfish

Morning,

I think I haven't explained properly. The top image is how the set up looks at the moment. Notice how the rotor (yellow line) sits below the top of the pads (red lines)
As the pads wear, the top of the pads, by the retaining pin (not shown) isn't getting worn down by the rotor.

Eventually they will look like image 2 where the pads are worn but the bit that isn't touches. When this happens the pads will obviously be pushing against each other and not on the rotor any more.

What I require is an adaptor that sits 3mm lower at the attaching point nearest the back of the bike, so that the callipers are lowered and the rotor sits so that it gives even wear over the entire pad surface.

Does that make more sense?

Rindle

I have had problems in the past with non branded OEM adaptors not fitting quite right on anything other than the original brakes and frame. Were the Tektros original on your bike?

I know its extra expense but if so I'd be tempted to buy a set of shimano rotor adaptors.

The Rookie

As its a wavy rotor, have you checked that the pic is at the peak and not a trough?

DCR00

Ive never had an issue with OEM adaptors

I currently have Formula brakes on Superstar rotors and adaptors. Before i changed them to 180mm i was using Hayes discs on Formula adaptors.

Newfish

@rindle - that's what I did think and have asked CRC for the measurement I need to check but they are being either very thick (I sent a picture) or just unhelpful.

@ TB - yes it is and yes I have so no joy there

Does anyone happen to have a rear shimano adaptor they could measure please. I'll post the pic of what I need if not sure

Rindle

Yep,

What do want measured?