Steering wheel shake when applying brakes

[Coalhod]

Hello: 1965 Cooper S with 7.5 inch disc brakes at the front and AFAIK original brake discs. After a recent 3 hour run at 40-65 mph on twisty roads toward the end of the run the car had a bad front end shake when braking. It seems better now since the brakes have cooled however still a bit of shaking when applying the brakes.
I plan on inspecting all front suspension parts as well as check the discs with a DTI. At this point it seems to be a classic case of warped brake discs. The suppliers have many 7.5 inch disks now from standard replacement to drilled versions. My thoughts are the drilled disc would be the best however there is supposedly a solid disk with higher carbon content which in theory would help with high heat issues.
Anybody here had the same issue?

Thanks,

Andrew

[Dr S]

Are they binding? I used to do 12 cars etc with mine, pushing hard and never had issues.

Or are you sitting foot on brakes with hot brakes?

[Coalhod]

I will check for binding. The car rolls freely when on a slight incline. I keep my foot off of the brakes until needed.

I neglected to mention the pad material is EBC Green Stuff and will check those also. I have used Mintex in the past with good results.

[Dan Tweed grey]

Play in the rack can cause this too, I have these syptoms on the n/s and it is play in the rack bushes.

[Coalhod]

Thanks. I did notice a clunking sound on the n/s especially when going over bumps. Dampers are brand new so probably not their bushings.

[Peter Laidler]

That clonking is the steering rack in my opinion and that wear is very probably the answer to the front end shake. Disconnect the rack from the hobs, test the track rod ends, the tightness of the rods in the rack and the rack for unwanted movement in the rack housing.

[Coalhod]

Dan, Peter you were right!

I'm getting .0025-.003" runout at the brake rotors, caliper removed. Some play at the rack especially the n/s where the rack bushing is. Rack rebuild time.

Many thanks to all! I blame this on trying to chase a Sunbeam Tiger.


Andrew

[Dan Tweed grey]

Awesome, I'm hoping to sort mine out when to shows die off for the winter.
Also will be chucking some straight cut drop gears in a ditch....