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Advice on a soft pedal after bleeding master / upgrading brakes

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Hmmmmmm.

I've never bled a M/C and I've never had any trouble with my brakes. Interesting.

My brother in law has a similarly moving pedal and he too has 256 front brakes but drums on the rear. He is also using a larger Servo and M/C.

Despite numerous bleeds with every item under the sun and manual pushing we've never got it better.

My wifes cabby has the standard set up and the brakes are sharp and the pedal moves a bit but not too much and they do inspire confidence.

My tin top has no servo, a massive M/C 256mm discs up front and mk4 caliper / mk2 golf gti rear discs. My peda moves about an inch. That's all. But I have 2 flexis on the rear. One over the beam and then one from a bracket to the carrier (not required I later found out).

I know that is of zero help in your conundrum but I'm flummoxed, both with yours and my brother in laws. I was hoping that there might have been something that went bingo! but apparently not.

It's all very odd.

My grasp of Fluid Dynamics is not deep enough to work out the fluid transfers required within the system but I do wonder if the M/C isn't big enough and the amount of fluid needed to activate all the pistons the required distance is virtually all the fluid in the M/C and whether or not a larger one (that hold more fluid) is required.  

That's the only explanation I can come up with for both yours and my bro in laws moving a lot.

It's something that sin't mentioned much so it would be interesting to do a poll of people who've upgraded the brakes to see how much the pedal moves. I suppose after doing an expensive upgrade that is 'known' to work you'd have to be brave to say 'I've done the suggested improvement and now it feels like rubbish at the pedal' . I suppose it also depends on what you expect it to feel like.

Ian

Cornish Host.
1980 VW Derby
Clive the Cabby
Ujum the Invisible
Mynx the  Tintop

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Yeah I don't know enough about the fluid dynamics either. Maybe just a bigger MC would sort it…amybe it wouldn't!

Frustrating for sure to figure out! Will take the car for a drive again tomorrow and see how it feels.

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Well to be honest, I have 2 cabbies, a year apart both had different feels to the pedal.

Both had everything Brake wise replaced when I got them Calipers, Wheel Cylinders, rubber hoses, and MC

One of the two would go through pads on the front but feel rock hard but one side of the car the pads would be thinner.

The other would stop but feel spongy…and didn't go through pads and the pads had even wear.

Forward through the years… I had to replace the vented rotors, and I rebuilt the Calipers and replaced the heel cylinders on the "Hard Pedal".  I used a power bleeder, and bled the whole system front and back twice over 2 days.

What do you know the Cabbies both have spongy brakes now.  :)  Go figure.

I don't think it was the fluid as I changed over from Castrol GT/LMA to Synthetic Originally when I First got the cars.  But they are the same now.  Go figure.

So am I suspecting that I have softened hoses that are ballooning?  Do I need to change them out after about 10 years?  I have to wonder, as the one cabby got the expensive Steel Jacketed ones, and one doesn't …

Then my question is are you using Solid Rotors or vented?

My 90 came with Solid rotors and I don't remember it being a soft pedal as well.




What do Divorces, Great Coffee, and Car Electrics all have in common?

They all start with GOOD Grounds.

Where are my DIY Links?

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Hi mate,

Rears are solid discs and the fronts are vented; basically Corrado G60 stuff.

Flexi hoses on the fronts are brand new. The rears haven't been replaced but nothing has changed to the rears; only the front brakes were upgraded.

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Took the car out again over the weekend and think I can better describe the situation now.

So, there just seems to be a lot of "dead travel" in the pedal before the brakes really engage. It isn't "mushy" or "soft" really, it's just a lot of pedal travel before things get going. However. if I put the pedal to the floor, the brakes are certainly strong enough to send you through the windscreen!

So the brakes certainly work, just the pedal itself has a lot of travel before sufficient force is actually applied to the brakes.

Ideas? Does this change anything?

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Well the Rube Goldberg set up y'all have is different than my direct foot to pedal to booster to MC.

With any length of travel differences I have ever seen on re-fitting a new MC or booster to the cars I have wrenched on it is the Free-play adjustment that usually caused the weak pedal play.

As there isn't much you can do between the booster and the MC, there is the free-play adjustment between the pedal and the Booster.

I would imagine that your setup would also have to be worried about worn bushings in the Mech and the Pedal to booster play.  I would look at the distance between the pedal push and engagement of the booster and try to eliminate the free play between them.

I have seen as much as a 1/2 inch difference between the pedal free-play and the booster after swapping over Boosters and or MC, as I don't know if the Manufacturer of the new MC had substituted the Depth of the MC cup that cause the differences in the length of push needed to engage.

I have also seen Boosters whose pedal to clevis connection differ… I just figured that it was the rebuilder of the booster using replacement parts that weren't the original OEM fitment.

I have had MC's and Boosters swaps that were a bolt an go, but then again I have had new ones that needed adjustments….out the WAZOO (read Keister).


 

What do Divorces, Great Coffee, and Car Electrics all have in common?

They all start with GOOD Grounds.

Where are my DIY Links?

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Hmm you talk about 1/2 an inch, but honestly mine feels more like a couple inches of not much until you start getting good braking force
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