Wrong size threads in tailgate . Need some advice please .

[1536Z4]

I have got round to fitting the carbon tailgate today but the threaded inserts they have used are M6 and the bolt threads are M8 :x

The fittings concerned are numbered 5 , 8 and 10 on real oem tailgate https://www.realoem.com/bmw/enUS/showparts?id=DU52-EUR-02-2008-E86-BMW-Z4_30si&diagId=41_1696

I have sent Geoff Steel an email regarding this but the person concerned is out until tomorrow . I have asked them if there is enough metal on the threaded inserts to tap out to an M8 or could I reduce the threads on the fittings to M6 which may be easier said than done . Before I get a reply from them my question is will either of these methods seriously reduce the security of the fittings especially the hinges as I don`t want them failing when I`m doing the speed limit down the motorway .
The only other way is for them to have the tailgate back and fit the correct size but again that may not be an option as they are probably done during the moulding stage ??

Advice and any other suggestions welcome . Thank you .

 

[Street]

I googled out of interest the different strengths of an M6 and M8. Depending on the grade of steel bolt it suggests an M6 has a proof load of around 1.3 tonnes. Given the yield load would be even higher, the 4 bolts combined for the hinge would probably lift the car up before the bolts snapped.

The challenge as you say to reduce the ball pin with a die wouldn't be insignificant. The other bolts can probably just be replaced with stainless M6's.

Size Grade 8.8 Grade 9.8 Grade 10.9 Grade 12.9
M5 820 kg 923kg 1,180kg 1,380kg
M6 1,160kg 1,310kg 1,670kg 1,950kg
M8 2,120kg 2,380kg 3,040kg 3,550kg
source: https://thomsonrail.com/metric-nuts-and-bolts/

 

[1536Z4]

Given the yield load would be even higher, the 4 bolts combined for the hinge would probably lift the car up before the bolts snapped.

That`s exactly what I needed to know and a relief as that will mean I can use M6 bolts as you said Reducing the thread size on stopper shouldn`t be too much of an issue as that can be put in a vice but the ball pin thread will be a pain as no real way of holding the ball tightly whilst using the dye . I will wait to see what Geoff Steel come back with and hopefully they will say that the ball pin fitting on the tailgate can be tapped out to size .

Thank you [ref]Street[/ref],

 

[Vanne]

Yeah, id be in agreeance with that. i get 5 and 8, but 10 is in the body of the car right? and your re-using the bracket from the original tail gate? weird.. not sure on yours, but with the UK racing plastics window fitted, i cant run 2 struts, they nearly eject the whole boot lid everytime i let it come up by itself. so i am only running one strut. saves some weight too lol.

 

[1536Z4]

i cant run 2 struts, they nearly eject the whole boot lid everytime i let it come up by itself. so i am only running one strut. saves some weight too lol.

:rofl: I wish you had posted this earlier . I fitted both struts and couldn`t understand why the tailgate wouldn`t go down more than half way . Then the penny dropped that it was due to the lighter weight and I removed one of the struts .