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GT6 Caliper Bleed Nipple Stripped


Ingieuk
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Hi All,

I have managed to strip the bleed nipple thread in the RHS caliper, dissapointed in myself is an understatement!

Any idea what thread the bleed nipple will be? By the commission number (late rotoflex mk3) they should be the metric 16PB caliper. Interestingly each caliper has a different type of bleed nipple (one short, one long) so I need to check I actually don't have two different calipers.

Has anyone got any experience of tapping out the bleed nipple to a larger size and sourcing a different bleed nipple? Or possibly a helicoil thread insert?

I did consider a recon caliper (or a pair) but I'm conscious some people have had issues with them. Prior to this I had no braking issues - the master cylinder was long overdue an overhaul, hence the ill-fated bleeding operation.

Any thoughts/criticism of my mechanical sympathy welcomed!

Richard 

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imperial calipers are 3/8unf thread, metric will be M10 fine thread. 

The same thread is used on bleed and also pipe connection, so you can check which you have. Take the caliper off, and see if the flexi hose (which should be imperial!) will screw into the caliper.

 

Recon calipers are usually fine, the problem lies with the brand new calipers. However, don't be surprised if an additional fee if is charged you have a broken bleed nipple.

I think there is a technique for recovering the threads, using an insert. Saw a brass one on amazon I think. Google is your friend, but recon may be a safer bet, and possibly cheaper.

Somebody else may have a brighter idea!

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1 hour ago, Pete Lewis said:

dont remember where from but there was a Co selling a repair kit, with a spigoted drill  a  tap and  6  replacement nipples all in a set 

pete

They're sold under the rather strange name of 'Nipple Therapy'... don't ask.

However at £65, unless you're doing a lot of calipers, a replacement is a lot cheaper.

http://www.fraserbrowneng.co.uk/store/index.php?route=product/product&product_id=51

Only one S/H caliper on eBay at present and it's LHS:

https://www.ebay.co.uk/itm/Triumph-GT6-MK3-L-H-FRONT-BRAKE-CALIPER-1966-70-64327813-16P/303546477388?hash=item46acc7ab4c%3Ag%3A2N8AAOSwjMtentUM&LH_ItemCondition=3000

There's a pair of Ford Capri 3.0 calipers for £40, they're also type 16 but are they the same mountings?

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10 hours ago, Ingieuk said:

Hi All,

I have managed to strip the bleed nipple thread in the RHS caliper, dissapointed in myself is an understatement!

Any idea what thread the bleed nipple will be? By the commission number (late rotoflex mk3) they should be the metric 16PB caliper. Interestingly each caliper has a different type of bleed nipple (one short, one long) so I need to check I actually don't have two different calipers.

Has anyone got any experience of tapping out the bleed nipple to a larger size and sourcing a different bleed nipple? Or possibly a helicoil thread insert?

I did consider a recon caliper (or a pair) but I'm conscious some people have had issues with them. Prior to this I had no braking issues - the master cylinder was long overdue an overhaul, hence the ill-fated bleeding operation.

Any thoughts/criticism of my mechanical sympathy welcomed!

Richard 

Hi Richard,

You certainly have my sympathy, we all do these things and end up wondering why we ever started the job in the first place. Most of my garage nightmares seem to involve either shearing or stripping a threaded part. Dropping nuts into dark inaccessible recesses where they promptly become wedged is another!

Take care over the metric vs imperial thread patterns, as late 1972 seems to have been the changeover point. My late rotoflex Mk3 (October '72) had one metric and one imperial caliper when I bought it 20 years ago! Don't know if it let the factory that way, or if one had been changed incorrectly before my ownership. I've since replaced both calipers with service exchange imperial items and changed one of the brakes pipes to match.

Nigel

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1 hour ago, Colin Lindsay said:

 

There's a pair of Ford Capri 3.0 calipers for £40, they're also type 16 but are they the same mountings?

No, but they are the same as spitfire/herald Type 14 mounting lugs. The question though is does a GT6 brake disc fit (it does to a spit/her hub, but it may be too bid a diameter with a ford type 16 caliper.

 

Sorry for thread drift. (what I want is somebody to try it out!!)

 

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It can be quite difficult to tell the imperial and metric 16PBs apart.  The fact that 3/8" UNF fittings will screw into the M10 x 1 (fine) tapped holes (albeit feeling slightly slack) does not help.  The mounting holes are also slightly larger needing special bolts with slightly thicker shanks, but still a UNF thread.

Is the thread definitely stripped in the caliper - or are you inadvertently trying a UNF nipple in it?  They should actually hold reasonably well if both threads are in reasonable shape but much easier to strip by over tightening.

M10 x 1 male threads will not screw into 3/8" UNF tappings without significant force and damage is caused.

Nick

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Thanks all for the very informative responses!

Nipple therapy is an interesting name for a product! Though I only have one caliper to sort.

Once on the bench I have managed to identify I indeed have two type16pb metric calipers. It looks like the thread is salvageable so I've ordered a M10x1 (fine) bottoming tap and replacement bleed nipples.

I found the chrome on all four pistons is in a poor state so the calipers are going to get a full overhaul. I won't split them though as a couple of exploratory heaves on a breaker bar wasn't close to shifting the bolts.

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9 hours ago, Nick Jones said:

Sounds hopeful.  Bigg Red offer the seal kits and stainless steel pistons for these calipers, which have worked very nicely on the three pairs I've done.  You'll have to ring them to order though as they don't appear on their website.

Nick

+1 for Bigg Red, good quality and service. 

They have an eBay shop, including kits for GT6 calipers:

https://www.ebay.co.uk/itm/FRONT-Brake-Caliper-Piston-Seal-Repair-Kit-for-Triumph-GT6-Vitesse-BRKP29/283793885884?fits=Car+Make:Triumph|Model:GT6&epid=3004075958&hash=item42136f0abc:g:ljEAAOSwL9paazCC&redirect=mobile

Nigel

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On 28/06/2020 at 21:39, Nick Jones said:

Sounds hopeful.  Bigg Red offer the seal kits and stainless steel pistons for these calipers, which have worked very nicely on the three pairs I've done.  You'll have to ring them to order though as they don't appear on their website.

Nick

I wish I'd checked there first, 4 pistons and two seal kits was £67 from JP, £35.99 from Bigg Red. 

Nevermind! Know for next time. 

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  • 2 weeks later...

Just to update this with a resolution. 

Having got the calipers out it was evident the threads are good and strong in comparison to those on the bleed nipple. Having ran an m10 bottoming tap through them they came up lovely.

A new set of brass m10 fine nipples and fittings and all is right again. Phew! New pistons and seals have worked a treat. 

Thanks all for the help. 

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