C5X Roofbars

[exXM2]

Bought roof bars for C5X Hybrid with flat roof (the model without rails). The bars fit nicely across the roof but the fixing screws that go into the captive nuts in the door openings don't fit. They are standard M6 with a pitch of 1mm. I have tried a tap, then a tap of pitch 0.75mm, made a screw with pitch 0.75mm, everything just jams or won't start. Same with UNF and UNC equivalents, even tried BA! It's not me getting them cross threaded, an engineer from local Citroen dealer tried them in another C5X for sale, same result. Citroen don't list the screws separately. The supplier is relying on the online charts which are supposed to to match car and product, which are clearly not correct. Anyone have roof bars on a C5X (or even other Citroen) that fit or can shed light on the correct screw pitch?. Or as the C5X is a French design made in China is there some other standard of screw thread?!

[myglaren]

I had a similar problem using the roof bars from my C5 on my current Mazda. Fortunately a neighbour has a business importing nuts, bolts and screws and was able to give me a handful that work.
Previously I used to rely on a local business called K Engineering who could supply any imaginable nut, bolt or screw, among other things.

Had a quick look and they don't appear to have a branch near you but there is sure to be something similar on Teesside.
https://www.k-engineering.co.uk/branches.htm

[PaulC5]

A search suggests there is also a 0.5 thread pitch. https://www.mscdirect.com/product/details/06179394

[Richard_C]

As far as I know China uses its own certified version of ISO standards - metric. I've got the odd made-in-China woodworking machine and they are all metric.

The normal M6 is M6x1 thread form but M6x0.75 is a permitted ISO standard so it could be that. My 2025 C4 is definitely M6x1, but the roof bars I have don't screw in they just have little studs that push snugly up into the hole to stop fore and aft movement, once the bars and feet are assembled they are not going to move downwards or fall out. So in extremis maybe get some M5x1 10mm and just push them in?

Are you sure the threads are not full of paint? I bet they fit the threaded rivets and spray the car afterwards. If that is the case you might be able to take an ordinary M6 bolt, taper the end a bit with a file then screw it in a bit, back it out, screw it in a bit, back it out ....

[Sloppysod]

Not sure this will work, but do you have any glue sticks, the ones you use in those little electrically heated glue guns.
If you do, put something like thick oil/ vasoline into the to threaded holes, to act as a realease agent, warm up the glue sticks a little, then screw them into the holes, unscrew and measure. Could possibly use a candle.

[exXM2]

Thanks everyone, Seems that K engineering and others only have the usual M6x1mm. Other sizes presumably for precision / scientific engineering. You are right that the threads are painted but I did try 1mm and 0.75 mm taps to clear them but they just jammed. Sloppysod, I love that suggestion which I will keep in my mental toolbox! I did try something similar by forcing a plastic rod in and counting the threads, but it wasn't too clear and suggested about 0.9mm which isn't a standard.
Anyway I am returning the bars and may try a proper Citroen set. Failing that I'll try to modify and old set and just use pegs.
Martin