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I 'upgraded' from a set of Magura MT6 to Formula R1s. I am not sure why I did this, the Maguras were fabulous. I am using a set of KCNC rotors.
The R1s are new but were produced some years ago I think. I am really struggling to get the rear wheel to spin freely without any rub on the disc. I have done the usual of loosening the brake mount allen bolts and retightening, and also took the pads out and tried to push the pistons back. The problem remains. From what I have read the clearance on Formula brakes at the discs is notoriously tight, and I am wondering if maybe Formula discs are a bit thinner than other ones? I also tried slotting in a couple of business cards either side of the disc before resetting the mount - the clearance is so tight I can't even get a business card in the gap!
Looking at the brake levers I see there is an adjustment for lever reach, and there appears to be another adjustment possible where the cable enters the housing at the lever with a plus and minus sign on it, but I have no idea what this does?
Can anyone offer any advice?
Magura rotors are thicker than most other makes - that might be your issue. I’m not familiar with the R1 though.
I've got a few sets of this era, they're really good but obviously getting older and wear/age can have an effect.
Formula are tight but it shouldn't be a problem. There's one really specific formula-ey thing which is that the diaphragm for the fluid reservoir is at the back, against the bars, and it vents through there too. So if it's not venting, it becomes a little air spring and causes problems. I've had it happen when it's been really dirty there but probably more relevantly, when it was overtightened onto the bar. I think it's more of an issue with painted or carbon bars than with raw metal as it's softer.
Did the pads move back properly? If not I'd suspect there's too much fluid in the system (which usually just means it's been bled with worn pads)
The lever adjuster won't help, it's purely span. The other adjuster is basically "feel".
Thanks Northwind. Yes the pads do move back - a tiny amount. I suspect I will have to admit defeat and put the bike in the hands of a mechanic, it just seems there is very little tolerance in the whole system, while the front brake works just fine.
If you're going to take it to a mechanic anyway, it couldn't hurt to try and let a little fluid out- just undo the little torx at the caliper and and then push the calipers back and retighten
I've got the fear just reading your message Northwind.
But yes I will try... it couldn't hurt... could it?