Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Brake Pedal 'Pulse'....

Clearly I am guilty of that predominantly male problem... "Only read the instructions when you have a problem"

OK... Update of sorts.

Went out for an extended drive today, it really put a smile on my face.... But that's another story.

The pulsing is quite severe at high speeds, less noticable at low speeds. I tried lots off hard braking from high speed in attempt to flatten whatever's causing the pulse. No difference. I also tried a while driving with my left foot on the brake... No difference.

When I got home I took the front wheels off. The near side is fine, the offside is definitely binding.. By rotating the disc, half of it is being grabbed by the pads, the other half revolves freely.

I have some extremely bright handheld lighting and examined the disc at all angles - there's not a mark on it (although I can't see the inside face). I gently rubbed with fine sandpaper - but it hasn't made any difference.

Hmmmm!

Maybe the pad has jammed or not fully returned into the piston so with a slight disc warp it catches. Hence the pulse frequency with speed?

I remember changing pads on a renault 5 & pushing the pistons back in for the new pads was a real sod.

Can that be fixed?

The discs shouldn't warp on a brand new car should they? It's not been tracked and I don't leave the brakes on....

Yes I guess by new discs. If it is under warranty I would go back to the dealer.

Neil,
As ever it is difficult if one cannot see the items, but if there isn't any rust or pad marking on the discs, then it could be a warped disc. It does sound a bit that way, especially with the more pronounced judder at high speed and you detecting that the pads are binding on only half on the disc.

I use a dial test indicator on a magnetic base to test if mine are running true, but if you don't have such a thing then try setting up a pointer (like a nail through a block of wood) that you can fix steady next to the disc with the point tip of the nail touching the disc surface. Then rotate the disc and if you can see a small air gap between the nail and the disc on one half and the nail just touches the disc on the other half, then it shows the disc is running out of true... if so on a new car like yours, I would have thought that it should be a warranty job to change the disc.

Hope this helps, if you like PM me and we can discuss, MZ.

Edit: John/Neil - sorry didn't see your exchanges... slow typing!

Hi MZ, that's very helpful thanks.

When rotating the disc by hand (wheel off) it only just grabs it, with the wheel on, the momentum caused by the weight of the wheel makes it barely noticeable. I suspect the stationary nail head would not pick up such a small 'out of true' warp. Neither would my eyesight!

At speed, driven, it feels like a rumble strip on the motorway - well, 60% of that sensation.

The car needs to go back to BHM at some point for another issue - I'll ask them to check and replace the disc under warranty.