A Question for You

kentvette

CCCUK Member
And I'm sure you are 100% correct - and ordinarily I would agree...........with a stock vehicle. Yes, I'm using 'o' ring seals - yes, the brakes are in good condition, - yes, using good pads (Hawk HP Plus) However with 50% more of 'everything' braking inadequacy (certainly for me) is still an issue. I remain to be convinced that some of the aftermarket 'big' brake options on the market are a significant and worthwhile improvement. Even in the 'States the best you will get from anyone who has used ab altermative is "great brakes, work well bla, bla, bla". No one individual or company has actually measured and compared stopping distances etc. I'm certainly not prepared to shell-out 3 or 4 £K in an attempt to significantly improve my brakes based on comment like "great brakes, work well" etc etc

I have a friend here who is currently changing the original brakes on his '72 for a Wilwood set-up, 6 pot fronts and 4 pot rears, with new rotors (all round I think). He enjoys track events and reckons the new brakes will be a big improvement. I'll be very interested to see what he thinks. While I doubt I'd make the change, certainly not to 6 pits, the Wilwood callipers are lovely bits of kit!
 

kentvette

CCCUK Member
Will do. Any cyclic noise caused?

You may hear a bit of "squeaking" from the pads if there is run-out. It it stops when you rest you foot on the brake pedal, its' often the cause of the noise. If the rotors have been off, there's a chance they didn't go back in the same orientation (180 degrees out). And, if you've had new spindles, you'll need to check run-out.
 

Forrest Gump

CCCUK regional rep
And I'm sure you are 100% correct - and ordinarily I would agree...........with a stock vehicle. Yes, I'm using 'o' ring seals - yes, the brakes are in good condition, - yes, using good pads (Hawk HP Plus) However with 50% more of 'everything' braking inadequacy (certainly for me) is still an issue. I remain to be convinced that some of the aftermarket 'big' brake options on the market are a significant and worthwhile improvement. Even in the 'States the best you will get from anyone who has used ab altermative is "great brakes, work well bla, bla, bla". No one individual or company has actually measured and compared stopping distances etc. I'm certainly not prepared to shell-out 3 or 4 £K in an attempt to significantly improve my brakes based on comment like "great brakes, work well" etc etc

Could you convert to servo assisted?

My servo brakes are good, certainly capable of locking the wheels, and the car pulls up well. My only complaint would be that the pedal is not as solid as I would like.

I would think for track days there are other things that can be done before needing to splash out on wilwoods, such as high performance pads, drilled and/or slotted discs, high temp brake fluid and additional cooling.
 

Chuffer

CCCUK regional rep
Could you convert to servo assisted?

My servo brakes are good, certainly capable of locking the wheels, and the car pulls up well. My only complaint would be that the pedal is not as solid as I would like.

I would think for track days there are other things that can be done before needing to splash out on wilwoods, such as high performance pads, drilled and/or slotted discs, high temp brake fluid and additional cooling.

The downside of drilled discs is their propensity to crack between the holes due to high temperatures generated under constant hard braking such as on track days .
 

Roscobbc

Moderator
The last few weeks I have been using the Vette once or twice a week for local shopping trips - tbh using more regularly seems to have improved a number of things, including perhaps my own perception of what to expect from a 52 year old vehicle......:unsure:
 

Chuffer

CCCUK regional rep
The last few weeks I have been using the Vette once or twice a week for local shopping trips - tbh using more regularly seems to have improved a number of things, including perhaps my own perception of what to expect from a 52 year old vehicle......:unsure:

I bet you get some looks in the supermarket car park :)
 

Roscobbc

Moderator
I bet you get some looks in the supermarket car park :)
Strangely not Andy - kinda think that most people who use supermarket car parks don't actually care about cars or have the slightest interest - why else would you typically see shoppers simply 'flinging' car doors open against the car next door without a care in the world. And if you just happen to be sitting in your car at the same time also have the neck to deny it ever happened.
It's the mix of people, all ages and seemingly background who stop and make comment - the two blokes yesterday with hoodies on, slouching around with their strides half way down their ass's - the thumbs-up from the old boys - the other drivers who even when having the right of way, stop to let you out of a turning.......
 
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Chuffer

CCCUK regional rep
On the few times |I have used mine for a shopping run I always park at far end of carpark where it is nearly empty because most people can`t be arsed to walk !
One time I came back to find a group of young lads admiring it and usually get a comment from other shoppers on other occasions . In the first lockdown last year when there were long queues to get in supermarkets I think every head turned as I went by . :)
 

antijam

CCCUK Member
I recently took my C3 down to the local Mercedes dealer to pick up some spares and parked among a range of M-B exotica. When I came back to the car it was surrounded by a group of Mercedes employees. I'm not sure they knew what they were looking at since one wanted to know if it was a 'real one'? o_O
 

Chuffer

CCCUK regional rep
I recently took my C3 down to the local Mercedes dealer to pick up some spares and parked among a range of M-B exotica. When I came back to the car it was surrounded by a group of Mercedes employees. I'm not sure they knew what they were looking at since one wanted to know if it was a 'real one'? o_O

Sounds like the average numpty employed by main dealerships to me :rolleyes:
 

CaptainK

CCCUK Member
Sounds like an event to be planned for the Club when we're allowed back out - instead of rolling road days, track days etc, we all turn up with our different braking setups and have a 100 - 0 mph braking test on a runway or something. Granted it won't be particularly scientific as they'd all be fitted to different cars etc, but hey hum. I'd be interested to see the difference between a properly setup NON power brakes and power brakes. I know in mine, after changing from NON-power to Power brakes, that there was a huge difference.
 

Chris Sale

CCCUK Member
After seeing some of the comments regarding C3 Brakes in this thread I thought it might be useful to look at the differences between lip seal vs O-ring seal pistons in C2/C3 disc brakes, for the benefit of anyone not already familiar with these differences. My source for much of what follows regarding lip seals is the January 1965 SAE paper ‘High Caliper Braking’ (by Duntov & Brown from Chevrolet, Shaw from Delco Moraine) on the development of Corvette disc brakes.

In any disc brake setup, one of the main components – disc, caliper or piston – must be able to move or ‘float’ in order to accommodate the movement of the hub on the spindle due to cornering forces etc.

I have never seen a floating disc on a car but I think these are common on motorbikes, and many cars on the road today have floating caliper brakes. For various reasons, when GM/Delco were developing the C2/C3 disc brakes they decided to go with fixed discs and calipers, and use floating pistons to absorb any movement. Another requirement was for the pads to be in constant contact with the disc to minimise brake pedal travel.

For floating pistons to work, they need a mechanism that enables them to keep the pads in contact with the disc as it deflects on the spindle due to cornering forces, and/or due to disc runout. Without such a mechanism, the pistons will be ‘knocked back’ by the movement of the pads, displacing brake fluid back to the master cylinder. The effect of this will be to require additional brake pedal travel on brake application because the displaced fluid will first have to be pushed back into the caliper before the pistons can make the pads contact the disk. When driving, this can be experienced as a slight lag between hitting the pedal and starting to brake, plus an initial ‘soft’ feel to the pedal.

GM/Delco solved this problem by using springs behind the pistons to keep the pads in contact with the disc as it deflects on the spindle. The springs need to be light enough to avoid creating excess drag, and the piston seals must have less friction in the cylinder bores than the spring force for the springs to do their work. The flexible lip seals used in original C2/C3 brakes meet this requirement and eliminated the knock-back problem.

However, good as the original C2/C3 disc brakes were, a couple of problems started to appear over time. One was a tendency for moisture to enter the cylinders and start corroding them as the piston boots degraded. The other was a tendency for the cylinders to leak if cars were not used for extended periods of time.

The first problem is beyond the scope of this article. The second, the leak over time problem, was due to the flexibility of the lip seals allowing the pistons to drop in their bores due to lack of use. This would deform the seals just enough to allow fluid to pass them. Hence the advice you will often see to ‘tap the brake pedal regularly’ if the car will not be driven for some time.

To combat the leakage problem, after-market suppliers developed O-ring pistons as direct replacements for the lip seal pistons, and many C2/C3 owners now use these. There is no doubt that O-ring seals provide much better leakage protection than lip seals during periods of inactivity. However, there is a possible disadvantage to using O-ring pistons in that the O-ring seals are a tighter fit in the cylinder bores than the lip seals. Consequently, if an O-ring piston is ‘knocked back’ the springs may not be strong enough to overcome the seal friction and enable the pistons to keep the pads in contact with the disc.

After doing considerable homework on Mr Google, I think the lip vs O-ring consensus would seem to be as follows:

  • For cars that will see limited use, or will spend much of their time on display, O-ring pistons will be superior due to their better ability to prevent leaks over time.
  • For cars that are driven regularly, O-ring pistons should work well in cases where bearings are correctly adjusted and disc run-out is a minimum.
  • For cars that are driven regularly but which may have looser-than-spec wheel bearings and/or excess disc run-out, there is a good chance that piston ‘knock back’ will occur, resulting in a hesitation when the brakes are next applied.

Chris Sale
’64 Coupe (with lip-seal front disc brakes)
 
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