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[Geoffers]

Hi Trevorch. I had exactly the same problem with the front disc of my M.G. Breva 750. The disc had worn unevenly and had a high spot that was causing the pulsing. Only 2 thou but enough to cause the problem, which was getting steadily worse. Might be worth checking your disc with a micrometer to see if this is the case. A friend of mine also had this problem with Brembo discs, which were replaced under warranty.
Hope you soon get it sorted.
Geoffers.

[Alan R]

Hello again-------- so the sensation then is as if it were "Grabbing" ?? ------ This is caused by the rubbing surface of the disc face not being actually flat across the full surface. Remember as a kid --on your push bike ---if the front rim got a slight dent in the side where the CALLIPER brake blocks rubbed ?? You'd get an intermittent GRAB !! as the blocks momentarily dropped into the ding. Same thing here only much magnified by the hydraulic pressures involved.... The face may be at 90 degrees to the spindle( Thus no Swashplate action) but this will be in the form of a RADIAL depression in the surface. As mentioned, it only needs a couple of thou for this to happen. To help you visualize this---- 10 thou. (0.010") is the thickness of the lines on an Engineers 6" ruler....... Your pistons are pulled back very slightly by the ELASTIC HYSTERESIS of Rubber---- look at this }------ http://www.madphysics.com/exp/hysteresi ... _bands.htm ------- and will actually have the slightest of contact. That's quite normal. You may hear a slight "Hissing" sound as well. With the disc removed place a known flat edge over the rubbing surface and check for NO CLEARACE at all...(Use the thinnest feeler gauge possible--- = 0.0015" ie 1.5 thou I think is the standard. A bright light behind the join area also helps to see any dips or hollows....... Here's a thought for you during those flying lessons----- The rear gunner in a Stuka dive bomber ?? Great faith in his pilot, eh ?? Spent all his wartime activities going down backwards--fast !! Happy Landings-----------------------------

[Roeland]

Very interesting. I think part of the handling of my bike might actually be exactly what is been discussed here. I will check it tonight. thanks

[trevorch]

Alan R, food for thought indeed. will work on it this weekend. BTW 9th lesson today, landings improving, but it isn't easy to get everything right yet, but living the dream.

Cheers TrevorCH

[apparently lucky eddie]

Thats a rich mans game, flying, Trevor, I learned to fly at Biggin Hill back in the late 70'/80's. It amused me no end when I rolled up to the club on either a very loud Ducati or an oily, incontinent old Triumph twin to see some of those rich gits looking down their posh noses cos I was n't in a Jag or something posey. Flew the usual little Cessnas, Firefly, Grumman Tiger/Cheetahs and even an old Moth. Good fun and a source of 5* 100 octane petrol for the Duke too. Wouldn't want to pay the bills now though. You'll enjoy 10 and 11, which used to be stalling and spinning, although that may have changed by now.

[trevorch]

Hi, ALE (short for Apparently Lucky Eddy.)

Stalls come up next week, spins are not required anymore. Yes, I wish I had done it all forty years earlier. Sorry off the subject, must get back to checking Bullet disc this weekend and adjusting the rear chain.

Cheers TrevorCH

[trevorch]

Hi All,

Dial gauge reveals a run out of 0.5 at inner radius and 0,7 mm at outer radius of disc. This is about the same as I found on the original disc. So just dropping a note to my dealer to order a replacement. So was the replacement already warped? Can't say because I did not measure it at the time. How does a disc warp. Never really been subject to sustained heavy braking from high speed, not the way I ride and I suppose it is designed for the job. I reckon it must be due to lack of heat treatment or something like. Anyway, I will keep getting it replaced and kick up a bit of a stink this time.

Cheers TrevorCH

[shappers]

Hi Hi, sounds as if the hub the is bolted to is not true. Causing a flat disc to buckle.

Cheers, Shappers.

[shappers]

oops! spot the missing word, sorry.