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front caliper torx/star bolt


griffchris

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I'm trying to remove my uprated front brake calipers (420R), they are loctited in place with 2 star headed bolts. I purchased a star socket set from Halfords today, and set to it - the E12 socket kind of fits, but its chewing up the bolt head, so I don't think it is the correct socket type.  The bolt head has a couple of markings - "10.9" and , I think, "BC".

From reading it appears there are "Torx" and "Torx plus" standards - not sure this is relevant, does anyone know what socket I need to get a proper purchase on these??

Thanks

Chris

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Thanks Jonathan!!!

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Thanks Jonathan, I've edited my post above to add a photo.  I looks like the E12 socket I have should fit but it is a wee bit loose and I don't want to round off the bolt head any further.  I am having to put a lot of force through it against the loctite.  E10 is too small.

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The photo is of the bolt head, not the socket.  This link here shows a similar bolt rather better.  Excuse the poor description, but it seems to be the rounded protruberance onto which the splines sit that prevents the E12 socket from sliding on far enough to get a really good grip.

As an aside, my calipers are different to the uprated front calipers shown on the Caterham parts website.

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Presumably there is a bracket to which the caliper is bolted and that bracket is fixed to the upright?

I've noticed that the latest cars have a different upright with bosses to accommodate radial calipers.

There also seems to be a couple of different factory fit options with both two and four pot radial options.

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Yes, I spoke to parts today and they confirmed these are a new upright/caliper configuration.  They didn't know what the bolts were either *wobble*  - but are going to get back to me.

Last night I managed to coax the bolts out of one caliper using the E12 Torx socket, but on the other side (the side I tried 1st), the bolt heads are too rounded off to get a purchase.  Doing a bit more research, I am fairly certain that these are External Torx Plus bolts (M10 x 70), which have their own specific socket range, denoted EPxx, I found comments such that using a standard Torx socket on a Torx Plus bolt is likely to lead to damaged bolt and socket *banghead* 

I have ordered a Torx Plus socket set, in the hope that these will still get purchase on the damaged bolts, I have also ordered a bolt extractor kit as a back up.....

 

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Look forward to seeing if the next ones fit. And my money is on them doing just that.

If there's enough head left there might be ways of getting the bolt out before you resort to extractors. Experts often recommend welding something onto it that gives you some leverage. I try cutting a slot with a Dremel.

Jonathan

PS: And your experience might have saved someone else's bolts! :-)

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Yes, you read my mind, I've just been looking at M10 x 70 cap heads.  The External Torx bolts are grade 10.9, but I can only find the cap heads in 12.9 (i.e.higher grade - I've looked at Namrick, Westfield and a few other websites) - would this be a problem (?impact on torque values etc)?

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A 12.9 is higher tensile strength than 10.9, of course, but unless what you are bolting them into is strong enough to allow you to increase the applied torque there's no point changing.

Further, the higher tensile bolt is also more brittle and more susceptible to failure cause by cyclic loads such as seen with repeated heating and cooling.

I'd stick with what's specified. 

 

 

 

 

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If buying alternative bolts, you also need to be sure what pitch to buy.

It's more common for M10 fixings to be 1.5mm pitch rather than the 1.25 that JK links to.

Like for like repacement would be a more sensible option.

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If the head's too chewed up to use the sockets when they arrive...

1st option would be to weld an old socket on and turn that off.  If no welder available I'd grind the head off, withdraw the caliper over the remaining shank then turn the lower section out afterwards.  Once the clamp of the bolt head is released the rest will probably turn out with your fingers.  If you try and use an easyout before releasing the clamp you'll probably just snap it and have a whole new problem.

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On the subject of replacing the Torx + with cap heads or hexagons, does anyone think that would be an issue?

From what I've found out Torx heads were originally designed to enable greater torque to be applied to Phillips/Posidrive type screws, because the Torx resists 'cam out' better. They were also used as tamper proof fixings when Torx tools weren't so widely available and that was the original use for the male type Torx bolts. They have no advantage in terms of torque application over a cap head or hex head.

So there seems no reason at all why these particular bolts couldn't be replaced by cap heads or hexagons, assuming, of course, the same thread and material spec is used.

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In you situation, I would buy the same bolts again.I suspect that if you'd had the correct tool to start with they would have come out OK. My experience of hexagonal drive v old style torx is that the hex ones are more likely to give trouble.

I had never heard of Torx plus and would have had exactly the same trouble if it makes you feel better.

Duncan

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