Roof bar attachment points

[RayS]

Bit of a long shot, but does anyone know the thread size and form in the roof attachment points of many current cars. These are under a little hinged flap - two on each side - and are presumably to some standard size as Thule and others sell roof bars to fit.
I thought they were M6, but ordinary M6 set screws do not enter to easily and I obviously do not want to damage the female thread. I wonder if they are M6 fine thread which has a pitch of 0.8mm instead of 1mm. I have asked suppliers and makers but they are taking a long time to reply and I need to get something sorted out very soon.

Any advice much appreciated.

 

[Lutz]

The threaded roof bar anchorage points that you refer to are not normally designed to take a screw. The thread is only intended to stop the serrated pins on the feet of the roof bar from slipping out when under tension. The roof bars are normally vehicle specific.

 

[MichaelE]

I presume your car is the saloon?
Some cars do have the roof bars bolted to these fix points but im not sure on the Mercedes as my cars have always had the roof rails on them.

 

[Lutz]

The only experience that I've had with threaded anchorage points is on Vauxhalls and these are for pin location purposes only, not a bolted attachment.

 

[MichaelE]

We have had a couple of vehicles ( french come to think of it) where you removed a cover and bolted the roof bar into place.

 

[ProfJohnL]

As Lutz pointed out, there is no standard roof bar system that fits all models. The details of the attachmant points will be unique to each manufacture or even model.
I don't know what the MB220 fitting system requires, but can I suggest you contact MB or your dealer, or contact a roofbar specialist who may be able to supply the detailed information for your model.

 

[Dustydog]

Many years ago I was carrying a large pine table securely strapped to a roof rack . At 55mph the roof rack left the car with the table. Fortunately there were no other vehicles about. The table smashed into hundreds of bits. If a motorcyclist had been following me I shudder to think what may have happened.

Rightly or wrongly I have refused to use a roof rack ever again. The bars on my car have a stated maximum weight but I wonder if that takes account of the aerodynamic loads that do arise?

 

[MichaelE]

As Lutz pointed out, there is no standard roof bar system that fits all models. The details of the attachmant points will be unique to each manufacture or even model.
I don't know what the MB220 fitting system requires, but can I suggest you contact MB or your dealer, or contact a roofbar specialist who may be able to supply the detailed information for your model.

Actually you are incorrect there are standard roof bar systems it is the mounting brackets/feet that are unique?

 

[RogerL]

Actually you are incorrect there are standard roof bar systems it is the mounting brackets/feet that are unique?

Since the brackets/feet are part of the system, then Lutz is correct that there are no standard roof bar systems.

 

[MichaelE]

Actually you are incorrect there are standard roof bar systems it is the mounting brackets/feet that are unique?

Since the brackets/feet are part of the system, then Lutz is correct that there are no standard roof bar systems.

Im afraid you are wrong as with the Thule roof bar system the bar is standard( you choose either aero or square bar) and you buy a foot pack to suit your car, this is a clever idea as you only have to change the footpack when you change cars, so yes there is a standard bar system and no the footpack is not part of the roof bars

 

[RogerL]

If the footpack is an extra then it's not a bar "system", it's just a bar - which isn't standard with other bars.
Pedantic I know !

 

[MichaelE]

Thule's Universal, low-profile roof rack for cars with fixed points is not unique to 1 make of car or model so i guess there is some sort of standard roof bar system out there after all?

 

[RayS]

Thanks for comments. Thule have at last told me the bolts are M6 but not whether usual thread (1.0mm pitch) or fine thread form 0.8mm pitch but doubtless will advise in due course.

Since only the foot profile of the various fitting kits differ for different vehicles ( to ensure the bars are horizontal front to back) this seems to indicate that M6 is the de facto standard for attachment points on makes other than Mercedes - perhaps this may be of assistance to someone else.