At last I’ve solved the annoying front brake pulsing/grabbing and fork diving when coming to a stop, and after 5000 km of use it is still perfect. I tried all the published methods I could find (including disc replacement) but the problem always returned within 50 kms of riding with little use of the front brake. This led me to believe and confirm that the wheel was not machined exactly 100% perpendicular to the axle and the discs were rubbing the pads leaving a deposit in a small section on the discs thus creating the problem. If you have the same problem, this is how you can easily check for yourself. Put the bike on a stand or the centre stand, raise and support the bike so that the front wheel is free to rotate. Remove the brake pad pin clips, pull each pin out, remove the anti-rattle plates then replace the pins and clips. As the pads have slightly elongated holes they can be lifted with a finger and dropped without any restriction and this is the way to determine just where the problem lies. Start with the outside pad, if the fault isn't here, go to the inside pad. While continually lifting and dropping the pad, slowly turn the wheel forward, as soon as the pad doesn’t drop, mark the tyre with some chalk, keep turning the wheel until the pad drops by itself and again mark the tyre... so you’ve now found the high spot for that disc. Do the same for the other disc, and you should find that the chalk marks will be at the same position on both sides of the tyre. If so the problem can now be corrected with a 20mm x 20mm x 200mm length of soft pine timber and a substantial hammer (seriously, I don’t advocate violence, but desperate times deserve desperate measures) and it saved me buying another wheel.
If you have semi floating discs and the bobbins are not seized, any small discrepancy shouldnt be a problem, surely.
Well, yes I do have floating discs and the bobbins were cleaned and freed, but that was just one of the many methods I tried and the problem still persisted. In the process I also replaced the caliper seals as I thought the pistons were not retracting enough and rubbing the discs and at that time it made no difference, but I'm not saying that it didn't contribute the final result.
Mine's had the pulsing for a couple of years - failed MoT twice on it. I cleaned discs, bobbins and checked runout - all fine. Also serviced the brakes and checked that all pistons were operating well. Finally, I've just switched from the stock M4 calipers to M50s - not only has it transformed the braking, but the pulsing has gone completely.
I'm so pleased that the M50 calipers solved your problem, it's one that I had considered but put it aside as a last resort. If you can improve the poor rear brake you'll be a hero for a lot of riders. Replacing the brake fluid with Castrol React SRF might do the trick as described here www.youtube.com/watch?v=RLgbsgNZ_Ss
I've been down the same route myself. 1. Swapped stock pads for Galfers. No change. 2. Cleaned and checked bobbins. No issue, so no change. 3. Swapped stock rotors for Galfer wave rotors. No change at all. 4. Replaced the stock calipers for M50s. No change. 5. Rebuild the M50's with new seals since the calipers were bought used. No change. After 10 months, 10k miles, touring, commuting, and a track day, I'm at my wits end. Like you, I figured the only culprit would be an out of plane disc mounting pad. I took the wheel to a local shop over winter and had them check things out. Granted, they are no metrology shop, but they found no issue with the wheel. I picked up a used set of Marchesinis to use as a set of track wheels. I only did one short road ride on them, but there was no pulsing before or during the track day that I could detect. Perhaps the pulsation needed more time to return. However, swapping back to the stock Enkei wheels INSTANTLY produced the pulsation. I ended up shipping the Galfers back to the factory for inspection, so the track day was run on the stock rotors. I'm of the mind that these aren't up to the task...and may still be contributing to the problem alongside the stock wheels. I'm planning on swapping the Marchesinis onto the bike for street usage once the current set of track tires is toast. I'm hoping/praying/pleading that the issue is a poorly machined batch of wheels because this problem is my biggest gripe with the bike!
Well you've proved that the machining of the stock wheel is indeed at fault, so now when it suits you can try my method to correct the faulty wheel. You should find that one rotor (say on the right caliper) will rub the inside pad and the other rotor (left caliper) will rub the outside pad, so before you use the hammer and timber be mindful which way it needs to go to correct it and not make it worse. Good luck
I'll find a good machine shop who can true up the rotor mounting pads while maintaining the perpendicularity w/ the axle...
@Technomad, the standard bikes (up to 2015) never had M4 calipers on them, they came with the same as those on the 848. I fitted M4 calipers (as used on 1098S) which were a huge improvement over the standard calipers. I'm sure the M50 are too. Money well spent imo. That said, the problem persists, its nothing to do with the caliper as such, although granted it could be the pistons not retracting enough, or indeed the calipers being bolted up slightly on the piss. I have had my M4 calipers off and fully cleaned them, plus new pads of various makes. The only thing that made any difference for me was to clean the disc bobbins. Not sure I fancy smacking the crap out of the disc, but I guess if it works...
Yes, I meant to edit my post to correct that - but knew you’d pick me up on it ;-) When I first had the pulsing, I cleaned the bobbins and it - just - got through the rolling brake test. Second MoT, I did that AND stripped down the calipers (and of course checked alignment when refitting) and - just - got through. Third time, I picked an MoT station that only has the only fashioned static brake test :-D and sailed through. Then immediately replaced the calipers with the M50s. So far, no issues at all, except now needing to tweak front preload - I had to do a fairly hard stop yesterday due to car farting around in front of me, which created a loud clonk of travel being used up!
Sorry for the late reply, I tried shimming around the bolt holes with Alfoil strips, one layer was not enough and two layers were too much...another failure! I'm bending the rotor/disc carrier legs and I'll explain the method I used. CAUTION before you start...ensure the pad pins are secured with the clips so they don't fly out with the hitting. Once you have established and marked the high areas on both sides of the tyre, turn the wheel to the front for easier access, now... 1. The rotor that rubs the OUTSIDE PAD has to be hit IN towards the centre, so in the marked area, place the timber on the first leg of the carrier just under the bobbin, place your leg on the opposite side to hold the wheel and hit the the timber reasonably hard, then with the same force, do the remaining legs of the carrier IN THE MARKED AREA...then test and see if it is not rubbing the pad, if it is, repeat the process until it is not rubbing. 2. The other rotor that rubs the INSIDE PAD has to be hit OUT and away from the centre, so feed the timber through the spokes, locate it in the same position just under the bobbin and try to hit with the same force as with the first side, and repeat as necessary until it doesn't rub the pad. Once this is done the rotors need to be worked with a course Scottish pad and cleaned with a suitable liquid, methylated spirits it fine. I recommend washing the pads and bedding them in as well. I guess this method does sound butcherous and unprofessional but it didn't damage or jeopardise the performance of my bike in any way.
