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Rear Disc Pad Knockoff

Started by _LXSS350_ , Aug 11 2011 11:39 PM

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#1 _LXSS350_

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Posted 11 August 2011 - 11:39 PM

As per my thread in drivetrain (shown below) we are putting together a few hatchbacks. Now I was going to stay away from the extra expense of floating any of the diffs, but today was told I might have to float the diffs if I wanted to run 4 spot APs on the 9" diffs, or else I will face the pads getting knocked off with axle movement??? Truth??

With the HZ stud pcd and the need for a handbrake (PIA) nobody seems to know anything other than how to fit old small live axle dunnydore rear brakes. Good for a dunnydore but lets face it who cares if a dunnydore hits a fixed object its just more rubbish of the roads. The only dunndore I have ever driven with decent brakes was the W427 but I cant have that bigger rims on a classic like an LX Hatch.

Typical of a hot rodders attitude "bugger it" want the best brakes.

Really aiming for something like the photos.

Posted Image

Posted Imagehttp://www.gmh-toran...ough-9-options/

#2 dattoman

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Posted 12 August 2011 - 12:10 AM

Yes you will need to float them if your going to run that style of thing with big rubber and fast corners

There are ways around knockoff
Heavier springs behind pistons , ability to drive , pressurised systems , etc

And Harrop sells a kit to convert small commodore brakes to the larger h/b size of VT on brakes
So then anything available for VT-VZ will bolt up

Theres also universal handbrake backing plate mechs that do the same
RRS uses them to do their Fud rear conversions if you check their site
All their Ford brakes seem to be COmmodore based due to availability... or were

#3 Litre8

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Posted 12 August 2011 - 07:50 AM

After any sort of fast cornering I had horrific rear pad knock-off with L8 when running a 9" with flanged axles. Problem totally resolved by running a Harrop full floater.

#4 _LXSS350_

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Posted 12 August 2011 - 09:47 AM

Thanks Datto and Litre8. Hot rodding is like pandora's box you open your wallet and spend lots of money. Litre8 did you try anti knockback springs before you went full floater? Its surprising just how fixed axles move when going hard into corners. But I am assured that I will once again end up in the sand trap with the pedal on the floor, especially if going as hard as the car should be capable of. Had a look at some of those park brake kits like on flee bay,rrs etc
http://www.turbo202....id=39&Itemid=86
http://www.rrs-onlin...kesproducts.php

The rrs thing is ford pcd and comes in kits with its own 6 spot calipers.Doesn't appear to be sold separate. Couldn't see the rear park brake adapter kit on the Harrop site.Loads of dunnydore rubbish. Is SLR8000 running a park brake?

#5 dattoman

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Posted 12 August 2011 - 10:13 AM

Just cause you can't find it on Harrops site doesn't mean its not there :)

Even flash race taxis with the best of everything and floating everything get knock off
Thats why they tap the brakes down the straight to set the pads back in place before the corner

Don't go thinking bigger is better and buying the wrong parts
Overbraking a car won't make it stop any better.... infact it will be worse.... than a properly set up package
Especially in a Torana

Your limited by how fast it car go around Wannaroo ... have a look at some of the faster guys up there and see what they are running
In Toranas that is .... I can't think of a single car running 6 pots

#6 _LXSS350_

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Posted 12 August 2011 - 10:30 AM

Just cause you can't find it on Harrops site doesn't mean its not there :)

Even flash race taxis with the best of everything and floating everything get knock off
Thats why they tap the brakes down the straight to set the pads back in place before the corner

Don't go thinking bigger is better and buying the wrong parts
Overbraking a car won't make it stop any better.... infact it will be worse.... than a properly set up package
Especially in a Torana

Your limited by how fast it car go around Wannaroo ... have a look at some of the faster guys up there and see what they are running
In Toranas that is .... I can't think of a single car running 6 pots


No pretty much convinced to stay 4 spot as the car is still a street car and staying with 4 spot we have less warm up time. If we where doing 25 laps of Wannaroo at full fight speed fade may become more of an issue. Rather get the best pad material or even slightly bigger rotors than go to six pots for a 1200kg car.

#7 TUF 308

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Posted 13 August 2011 - 03:02 PM

Forgive me but what is knock back? and what is the difference between a floated and non floated diff?

#8 rodomo

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Posted 13 August 2011 - 03:22 PM

Forgive me but what is knock back? and what is the difference between a floated and non floated diff?

Knock back is the pistons and pads recedeing back into the caliper as you drive. Sideways movement of the rotor/hub especially around corners, pushes the pads back away from the rotor. Also, the caliper piston seal slightly pulls the piston back when the pedal is released and is a built in characteristic of the groove in which the piston seal fits in the caliper.

A fully floating axle is like a truck type set up where the hub is supported by 2 opposed tapered roller bearings (same as your fronts) and the axle is removable without removing the hub.

Usually resulting in less axle float (in and out) than an axle mounted single bearing (Torana)

Edited by rodomo, 13 August 2011 - 03:23 PM.

#9 TUF 308

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Posted 13 August 2011 - 04:13 PM

Thanks for that. Somtimes you just have to ask

#10 _LXSS350_

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Posted 27 August 2011 - 01:33 AM

Just a closer to the thread
Due to safety concerns ended up going full floater,Billet Moser 35 spline axles, Big bearing strange aluminum carrier and pinion, Wavetrac with 4.11 gears, AP Racing 4 spots on 315mm two piece hat/rotor complete with custom radial mounts and a custom 3" carbon fibre tailshaft.

#11 Litre8

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Posted 27 August 2011 - 03:04 PM

Carbon fibre tailshaft? They must be light, how do they go for longevity etc?

#12 _LXSS350_

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Posted 27 August 2011 - 05:30 PM

Carbon fibre tailshaft? They must be light, how do they go for longevity etc?

We have never run one as we tended to run aluminum. Have an aluminum one but ordered a carbon fibre one from PST in Florida. The tailshaft is about 6lbs, add the 1350 yoke and uni's is extra 5.5lbs. They run them a lot in all forms of racing at much higher stress levels than we run. Longetivity looks ok but time will tell. Weight is always an issue with going fast.

#13 A9X

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Posted 27 August 2011 - 08:12 PM

I run harrops all round, and my big salisbury diff is from Ron Harrop's own stuff. Floating rear end and the whole shebang was supplied assembled from Harrop.

Still get horror knock off on some stages of Targa .

Quite scary sometimes.

If there is a fix, i'd love to hear it

#14 _LXSS350_

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Posted 27 August 2011 - 11:28 PM

Welby do you run strong knock back springs? We will run 4lb springs for a start and have a set of 7lbs in the parts kit. It vital to feel comfortable while high speed cornering and regardless of driving ability hitting the brakes should always mean "brake" not first tap to "reset the pistons".

#15 A9X

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Posted 28 August 2011 - 07:13 PM

I'm hearing you.

For me , i'd even be happy with consistency. 3 out of 5 times you'll tap the pedal and feel ok, then you'll get 1 time wher it will need a single pump to reset, then you get the scary one where the pedal practically goes to the floor!

We are running the calipers as supplied.
Datto would give you the specs.

Looking to upgrade from the harrops, but need to step up to 17's for clearance.

#16 dattoman

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Posted 28 August 2011 - 10:43 PM

I don't think there are any springs in your calipers Mark
But despite all the other Harrop cock ups at least they didn't leak
So we never pulled them apart to check

You can't cure it.. even with floaters and springs... but they both help

#17 _LXSS350_

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Posted 28 August 2011 - 10:55 PM

I think the thing is once your travelling at over 250kph+ everything happens so fast the security of not having to reset the pistons is a bonus. It doest matter what it cost because I dont like hitting solid objects at any speed let alone 150mph+. Might look at the targa rules to see if we can build a hatch to join the targa fun or perhaps the MCM. Go the Torana's.

#18 dattoman

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Posted 28 August 2011 - 10:56 PM

I'm not sure your hearing me
You can't stop it... but you can reduce it
So get used to tapping the pedal down the straight or become friendly with trees

#19 _LXSS350_

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Posted 28 August 2011 - 11:12 PM

I'm not sure your hearing me
You can't stop it... but you can reduce it
So get used to tapping the pedal down the straight or become friendly with trees

Oh I am hearing you and fully understand the mechanics.
LOL ......... Just doesn't mean I have to like the answer !!!!
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