Rear Disc Nut

[RCA]

Could anybody enlighten me on what the size of the nut that holds the rear discs on is?, Nothing I have is big enough so looks like I am going to have to buy one!!!
cheers
Richard

[shpub]

Errrrr its loose and held in place by the wheel nuts. Undo wheels, undo calliper and curse the top allen key bolt and it should all come apart.

Steve
www.tvrbooks.co.uk

[incorrigible]

Steve is, of course, completely correct

But FYI the nut you're on about holds the drive shaft in, you only need to undo that if you're taking the hub off (wheel bearing etc)

I you're taking the hub off you'll need to loosen that nut BEFORE taking the discs off, get someone to stand on the brake pedal to hold the disc in place while you jump up and down on a breaker bar

Obviously (I hope) ignore this if you're just changing discs/pads

[RCA]

Ok a little encouragement with the hammer and hey presto they came off, cheers steve
On another note the rear caliper piston will not go back in, how many times does it need to be turned, it does not seem to move at all, and on the front there does not seem to be anything to turn, does it just push in???
thanks





>> Edited by RCA on Tuesday 27th August 16:13

[incorrigible]

An angle grinder key does a good job, or you can nip to halfords and get a tool for it, 'bout a tenner

[GreenV8S]

quote:
RCA, to return the piston into the caliper, it needs to be turned clockwise, whilst under slight pressure. The way I do it is to put a small G clamp onto the piston and over the back of the caliper, tighten it lightly so it puts a small amount of pressure onto the piston, then use a set of pipe grips to turn the piston, and as the piston returns tighten the g clamp to keep some pressure on it. Also make sure that when you use the grips to turn the piston, that you only grip the outside lip, do not grip on the shiney surface as it could cause damage.
Hope this helps.
Quinny.

Front just pushes in, rear has to be 'screwed' in to rewind the handbrake adjuster. This is common to most/all Ford rear disc brakes and you can get a standard 'Ford caliper wind-back' tool to do this for twenty quid or so. It's possible to do the job without the tool, but far far easier with it.

[RCA]

Many Thanks, have just picked up my new ford winding tool!!!!, 17 squid!!!!, here goes!!!

[heliox]

before you start, make sure the fluid reservoir hasn't been topped up as when you wind the pistons back the exess fluid is returned to the reservoir and will spill out over the inner wing..not nice.

heliox

[RCA]

All done, many thanks for the replies!!!, As it turns out The red dot grooved discs that are on offer at halfords were the wrong ones as my chimaera has 5.0 brakes!!!, 260mm at the front and 280mm at the back, TVR said that some do!!!!, Luckily I took both front and rear discs and pads with me so got a match!!!
many thanks again
Richard

[RCA]

Too good to be true!!!, just tried driving and the fronts keep locking even without touching the brakes!!!, mainly the offside one, any ideas???

[beljames]

Variety of options....

The pads themselves: They could be the wrong size. Could be slightly out of line when you fitted them. Or could be a duff part. If it's just offside does this imply that the nearside is okay? If one locks, the other will probably do so out of sympathy (okay - I made that up, but there is probably some reason why it happens).

The calipers: Over time calipers tend to seize slightly. They normally free up as part of the piston pushing process when changing the pads and if you got the pads in with little hassle then this is less likely. I normally retract the pistons further than they need to go so that the pads are slightly loose in the caliper before pressing the brake pedal to tighten them up. That way i know that there is enough play in the caliper. Did you have any trouble getting the pads in? Had a seized caliper on my old Astra once. Lots of smoke... Sanded the pad friction material down to solve the problem (I DO NOT recommend this!!! I was a student and couldn't afford to get the caliper overhauled!)

You should be able to turn the wheels (just) when everything is all fitted and arced up. The brakes will obviously seem a bit better when new pads are fitted.

[RCA]

Matched everything up with old bits to make sure they were correct, both sides are locking, I remember when I put the front wheels on and tightened the nuts I could not turn the wheel, does this imply that the piston was not pushed in far enough??, I thought that once the pads were on the disc that everything would sort itself out once the brake pedal was pushed?? I pushed the brake pedal a few times before starting the engine to firm them up and that was fine, but once running they seem very spongy!!!???? I am v.confused!!!! None of my other cars have done this before!!!

[beljames]

The wheels will normally turn, although admittedly, it often requires a bit of duress! But as you're saying 'locking up', I'm assuming that four litres can't shift them! This is a little frightening.

Sometimes pads are over-manufactured and there is some 'burn off' in the early miles, but this should not be so profound that the damn thing doesn't shift! If it does go, I would drive it around gently a bit, (keep checking that things aren't getting too hot down there), and given a remarkably short period of time they will bed in, but your engine shouldn't be straining!

Can you remember whether you got the piston flat against the face of the caliper, or did it stand a little bit proud? Was it an almighty effort to retract the piston? You are right, the brakes will sort themselves out after fitting, and obviously you got the caliper back round the disk with no hassle. Normally you would spot a duff caliper when fitting not when driving. It's not unusual for both sides to go together by the way!

I'm trying to thing if there is some other obvious thing you've missed. Is the hydraulic system overfilled? Did you loosen the cap from the reservoir when fitting the pads (if not, do it now - if a load spills out this may be the problem - but unlikely).

[trefor]

Maybe the new pads are too thick for this installation?

[heliox]

quote:
I thought that once the pads were on the disc that everything would sort itself out once the brake pedal was pushed?? I pushed the brake pedal a few times before starting the engine to firm them up and that was fine, but once running they seem very spongy!!!????

If you've matched everything and are confident that the pads and disks are ok then i'd have another look at the calipers again and have a good look at the clearances between the disk and caliper.
The front wheel should free spin and not be tight (even with new pads it shouldnt be tight)Winding the

The "spongy" pedal is normally caused by air in the system or fluid leaks and as youve put new disks on it might be worth bleeding the system and changing your brake fluid too.
It does sound like the pads are too wide though.

heliox

[GreenV8S]

quote:
Matched everything up with old bits to make sure they were correct, both sides are locking, I remember when I put the front wheels on and tightened the nuts I could not turn the wheel, does this imply that the piston was not pushed in far enough??, I thought that once the pads were on the disc that everything would sort itself out once the brake pedal was pushed?? I pushed the brake pedal a few times before starting the engine to firm them up and that was fine, but once running they seem very spongy!!!???? I am v.confused!!!! None of my other cars have done this before!!!

Is the rotor offset exactly right? You can check by looking at the gap between the inner corners of the caliper and the two faces of the rotor. These gaps should be equal, meaning the rotor is central within the caliper. If it's just a couple of mil out, the gap on one side of the rotor will be too small and there won't be room for the new pad. With the wheel off the rotor will be able to twist slightly to 'even up' the gaps, if you see what I mean?

Also check that the outer edge of the rotor isn't fouling the bridge of the caliper i.e. the rotor diameter is not too big for the caliper position. (You can usually get a mil or so of play on the caliper mount which can cause or cure this problem.)

Finally if you've taken the calipers off, double check that you've put the caliper the right side of the mounting lugs on the upright and haven't added or removed any spacers or washers. (You wouldn't be the first!)

Let me know How you get on?

Hope this helps,
Peter Humphries (and a green V8S)

[RCA]

Cheers peter, it turns out that the discs offset was out by 3 mm even though this is what came up under TVR and was even checked by Red Dot who said it was correct!!!, It turns out that my front discs are the granada ones that have had the two holes drilled in to convert it from a five stud to a four stud!!!!!!
Put the old discs back on for now until winter when the old girl is going in the garage for a couple of months to be stripped and have everything re done i.e uprated brakes, new suspension, + engine stripped and cleaned/chromed/anadised!!!!
many thanks
Richard

[philshort]

3mm - isn't that about the size of the thick washers between the calipers and their mounting? I only ask because I couldn't work out how to fit the calipers properly until someone else mentioned them!

[RCA]

Taking the washer out which is about 2mm, still did not give me enough clearance, I tried!

[shpub]

Every sympathy... but it is a nightmare. See
www.pistonheads.com/gassing/topic.asp?t=14427&f=8&h=0

Steve