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Gt6 mk3 two different front calipers


Danwedges
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My front passenger brakes squeal when braking and squeak slightly without braking so I ordered a set of anti squeal shims only to find when fitting them that I have 2 different calipers on my car the driver side has larger diameter pins that hold the pads than the passenger side

Now I know this isn't right but I'm struggling to work out what calipers i should have and ill probably need to replace yhe brake pipe to the caliper as im under the impression that one side is metric and one side is imperial

My car is a 1972 Rotoflex gt6

What I've read is 72 onwards is metric and up to 72 is imperial 

Which do I go for?

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hi dan, mines is a October 72 build and has metric calipers. don't know when your build was , but the age of the cars now they could have anything on. you`ll have to check carefully if the brake pipes are metric or English or both? and change accordingly. you can still buy new calipers at the club shop and elsewhere, or buy second hand and rebuild yourself if confident

its difficult to guess by years according to the heritage records mine is built oct 72 and is non roto but not registered till june 73, has mostly late gt6 stuff but 72 instruments. but loads could have happened between 73 and now.

I used to live in Washington and in fact all over the north east, ?

 

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It's the Rotoflex that throws me because from what I've read it was only early models that had the Rotoflex so under that assumption mine should have the earlier imperial type but as you say who knows what's been put on since 72 they're repro calipers that are on as they aren't stamped with the g for girling 

Small world most people dont know theres a washington in england Can't beat the north east haha 

 

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That's not right Pete.

There are three types. Early 16P, later 16PB with revised dust cover design, both of these being imperial and both having the larger pad pins. The M16 is the final version and is similar to the 16PB apart from smaller pins and metric threads. These need the shouldered fixing bolts.

My '72 GT6 with roto has M16 callipers. As documented in another thread I've had issues with repro callipers. Whether they are the same from all sources, I don't know

Nick

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But to add further confusion, they are not the same as Ford M16 callipers (which use the same pads as "our 16 ones which is VERY handy) 

The ford ones have a lug mounting which is smaller, and they will mount directly to a spitfire upright. However, they won;'t work with a GT6 disc on spitfire upright (Unless you have access to a lathe and can reduce the disc diameter a little) I have often considered this the simplest solution to improving spitfire brakes. Think I stumbled across it on something written on the canley classics blog a few years ago. Would't be too troublesome to get a batch of discs machined up. 

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Easier to change it all to GT6, but probably more expensive. The garage phoned to tell me they'd sheared off both the bleed nipples on my calipers. 

"Should we repair it?"

"What do you think? :angry:

What did the do? Drill and re-tap? No, two new callipers. The easiest path.

Doug

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6 hours ago, dougbgt6 said:

 

Drill and re-tap? No, two new callipers. The easiest path.

 

Most mechanics these days are parts-fitters only. Off with the old, on with the new. My local garage is a great port of call for me, and recently they removed a non-functioning heater blower and put in a replacement unit from a scrapyard. When I checked the old one I could see a broken wire which could have been resoldered in place. They told me it wasn't worth their while as it would have cost as much in labour as it did to replace.

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So am I right in thinking I'll need to replace the flexi brake hoses to ones that match? Also do both metric and imperial hoses have the same thread for the hard lines or will I need to replace the hard brake lines on one side to match up with the odd side?

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It is awkward Dan. I keep brake pipe and fittings and make my own up. So you can have say a metric male end going to a metric caliper and the other end English fitting to the pipe. But it's best to be totally one or the other then there's no mistakes. Definitely do not put English fittings into metric or vice versa the thread forms and sizes are not compatible. 

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Yeah I assumed if the hose was metric on one side it would be metric on the other I might just order a pair of calipers, 2 flexis and a reel of brake line and remake the full front brake lines at least then I know everything is how it should be

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If its the pads, Ive got small pin pads fitted to my earlier large pin callipers (theres far more choice of pads for Ford M16 callipers) by drilling the pad holes out a little larger. Very easy to do as the backing metal is soft and they work perfectly.... 

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Shouldn't affect the flexi-hose as there ought to be a short length of hard-line between the end of the hose and the calliper.  Only the fitting on the end of the short hard-line will be different.  In fact, one way round (3/8" UNF into M10 fine)  the threads go together quite convincingly as the metric fine thread has virtually the same pitch and is a little bigger in diameter than the UNF.  Not good practice as doesn't give sufficient engagement for full strength.  Going the other way it's usually too tight to work, though it might go if "gorilla'd".

When considering new "repro" callipers, read this

I don't know if all repro callipers come from the same basic manufacturer (ours came via ebay seller) but beware.  If you do buy new and have troubles with long pedal travel, complain early and vigorously to the supplier!

Nick

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3 hours ago, Danwedges said:

I'd rather go refurbished girling calipers as the pedal feel isn't as I'd like and seems to stiffen up if you press it twice even tho the brakes have been bled and have no air in the system

Trouble is that symptom could be caused by the master cylinder or possibly the servo. How about clamping the calliper hoses one at a time and then both together to see how much difference you get at the pedal? 

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I don't have a servo on my car but I read a different post where someone inspected the grooves in the caliper for the seals in both original and repro calipers and showed pictures of the difference in groove shape and claimed it caused the pistons to return too much and described similar symptoms as I have that they can't get a good feel on the pedal and can only achieve a good feel via pumping the brake 

I mean don't get me wrong my brakes work and work well but they definatly stiffen up if I press them twice  

Hose clamps are one of those things I've been meaning to buy for ages but only ever remember when removing a petrol tank or some other tank containing fluid and wishing I had a third hand to keep the hose kinked 

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yes I read that but I doubt youve got repro callipers and it could be expensive to change them and find no improvement. At least not having a servo reduces the possibilities but on balance I would think the MC is more likely to be the cause and its a certainly cheaper to change. I paid about 12pounds incl delivery for a Land Rover 3/4" (slight increase in bore diameter but with a smaller reservoir than the original) unit and am very pleased with the result. 

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Dan,

Coming in on a long thread, so may be I've missed some.   But you say your brakes "definatly stiffen up if I press them twice ".   Have you thought of flexible hose deterioration?    If the rubber hose delaminates inside, the lining can form a valve, so that pressure cannot get back from the pistons.     New hoses aren't costly, well worth changing.

John

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one simple problem to give double press brakes is excessive front wheel bearing end float 

the spec is 002" to 00.8" end float , its best to stick closed to the 0.002" which is hand nipthe castle nut and back off one flat 

at 0.008" you get significant rock at the wheel rim and pad push back 

and with  no end float and you seize the outer  race to the stub axle  ££££s

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Dan it sounds like youre really going to have to clamp the hoses to narrow down the cause of the problem. You dont have to have hose clamps as Im sure mole grips or g clamps could be used with some round steel bar to do the job without damaging the hoses (assuming of course that their not the steel braided type)...

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18 hours ago, Danwedges said:

I don't have a servo on my car but I read a different post where someone inspected the grooves in the caliper for the seals in both original and repro calipers and showed pictures of the difference in groove shape and claimed it caused the pistons to return too much and described similar symptoms as I have that they can't get a good feel on the pedal and can only achieve a good feel via pumping the brake 

That was me.  I linked to that thread earlier too.  The comment on the groove shape was not so much a claim as a speculation as to the cause as we could find no other reason for a long pedal.  New braided hoses, no play in wheel bearings, no disc run-out, back brakes fully adjusted up, yet "forced" piston adjustment would solve the problem for a while - until the pads wore down and calipers appear incapable of self-adjusting properly, to the extent that the pedal would go most of the way to the floor if intervals between our forced adjustments were left long enough.  This is a caliper issue, but whether root cause is the shape of the groove, the seal dimensions, the seal hardness or piston finish I'm not completely sure.  I've rebuilt the original Girling units (M16) for my GT6 and will rebuild the original 16Ps on my Vitesse.  Now have an eye out for a used genuine pair to rebuild for the Spit (with GT6 brakes!) to replace the repro ones.

Note that poorly adjusted back brakes (or non-working "self"-adjusters) can give a longish pedal that feels much better after a double-pump.

Nick

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