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Discussion Starter #1
I have recently acquired my 68 Alfa GTV Stepnose and have noticed a strange happening when driving. After I take a tight corner at speed my brake pedal has an extra inch of travel. Still stops fine but a little disconcerting. Once I have pumped once the brake pedal it remains to normal. I have no fluid leaks and it is not fade as it happens whether I apply the brakes before the bend or not. The disks are fine (straight) so I dont think it is any piston knock back.

Any ideas would be much appreciated.

- Jim
 

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Sounds like you're experiencing piston knock back caused by loose wheel bearings. Loose/worn bearings will allow the rotor to wobble back and forth which pushes the caliper pistons into the caliper bores a little. When the brakes are then applied, the pistons must travel further before the pads contact the rotor.
 

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Discussion Starter #3
I have had the car off the ground and tested the wheels for any wheel bearing play but cant feel any (ie by 12/6 and 3/9 o'clock). Perhaps they need alot of force (ie hard cornering) to give movement.

- Jim
 

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Discussion Starter #4
Before buying the car had only covered 300 miles on 3 years if that makes any difference.

- Jim
 

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Sounds similar

This does sound similar to the master Cylinder problem I had on my 1750.

A constant pressure on the pedal caused a 'dropping" of the pedal.

The fluid is leaking past the seals in the M/C not out of the system.

I bought a new M/C from Alfaholics and it was solved.

i'm no expert though, only linking similar symptoms.

Regards

Nick
 

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my vote goes to rear wheel bearing play causing pad knock off.
 

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Discussion Starter #7
I have checked the front wheel bearings but not the rear so you may be onto something there. Are they fairly straight forward to change (My workshop manual doesn't cover the rear very well)?

Thanks

- Jim
 

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Same problem

I have a 1967 GTV with the same problem.I am on single circuit brakes with ATE calipers.When belting round a corner I to have the longer pedal.I replaced the rear wheel bearings with tight high quality japanese bearings (not wobbly new SKF FAG).The wheel (disc)play is the same.My car has the 2L LSD diff.I reckon that the play everyone says is the rear wheel bearing is that the axle is not supported sufficently on the internal spider gear and the play is pivoting on the rear bearing and there is no play there.Also if all ALfas have rear wheel bearing play is it the fact that dual circuit brakes don't give the same amount of travel after kickback and therfore don't feel it.I NZ and Australia there is a holden that comes std with heaps of rear wheel play it has floating calipers as soon as racing guys fit wilwood fixed calipers they have the same problem.
 

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My '67 had no such brake issues for nearly 20 years, then I put Milano calipers on the front and Spider ATE's on the back. Now, I can't get rid of the dropping pedal problem. Anything that will push the pads away from the rotor will cause pedal drop, as in too much runout at the wheels (loose bearings or warped rotor). A worn clevis pin in the linkage for the brake master can do it by introducing slop. Leaking seals in the MC can do it.

I've checked and/or changed everything that could be a problem, including brake pads, and nothing made a difference. What are we all missing? Could it be the adjustment of the MC linkage?
 

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Those dirty ole brakes

I have the same set up on my car as well I have alluminium calipers off a GTV6 or 75 as they are called in NZ and a 2L LSD with the std 2L calipers on the back.My car is also a 1967 GTV i am running the std booster and a master cylinder of 22mm bore I think.I have heard that mark 1 1750 s used the same master and brake booster but smaller pistons in the rear calipers and no proportioning valve for the rear.If all diffs/rear wheels have the same amount of play in them as I have seen then it possible that with dual circuit brakes the kick back is not noticed except on very worn cases and if smaller pistons are used et al 1750 mark1 then there is less fuild to push back and less or hopefully no kick back.Mine only has a problem when cornering
 

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Somewhere in my files I have a printout of a discussion about this issue, from ages ago. One theory being posed was that the under car location of the brake master is at least partially a factor. The solution being considered was to install a flow control valve in the brake lines, to help maintain a steady pressure in the lines. Does this sound familiar to anyone or must I solve the mysteries of my own filing system and find the missing notes? Tilton makes such a valve for hydraulic clutches.

I don't think the issue is too much front or rear brake bias. I have a Tilton proportioning valve. It doesn't help the drop pedal problem.
 
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