I've ordered some replacement M6 Torx head bolts for my roof rails as one sheared during fitting and another shows corrosion after being on the vehicle for three years.

What metal composition gives the best corrosion resistance and thread strength? I see there are options of titanium and stainless steel. Freelander 2 2010 [MY2011] FA 2.2 TD4 XS

The cause of bolts shearing can be that the bolt bottoms before tightening therefore you are twisting the head off at the end of the female thread, ensure the thread and hole depth is greater than the distance from top of the mounting hole to the bottom of the of the rail bolt head. Corrosion resistance would be stainless steel but is softer than high tensile steel. my PC is slightly to the right of Genghis
2012 HSE SD4 In Orkney Grey now gone, best car ever.

The problem with the Land Rover roof rails is the roof rails themselves, not the bolts. Even though the bolts seam a bit light.The roof rails are far too flexible with a load & the centre support is a joke at best.

The standard bolt is strong enough & it is galvanized. You do not want to use stainless steel on a steel body. If you use stainless steel wrap in gas (thicker tape) PTFE tape so their is a barrier. Use M6 Allen bolts.

When bolting down tighten up the cross brace last with the last 2 to 3 turns otherwise you are bending the bolts going into the roof.

https://www.freel2.com/forum/topic35376.ht...s+upgrade7

Some photos down this page with an M10 on the run (now returned to an M6).
https://www.freel2.com/forum/topic32055.html

Down under I have seen plenty of expedition racks where numerous welds have snapped.

We haven't been traveling yet due to Covid as we can't cross borders in Australia, but I think the latest modifications with 5083 alloy bar & Teflon on the end brackets should pretty much solved the actual problem with the roof rack, or more to the point the rails. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

Dartman the one wrote:

The cause of bolts shearing can be that the bolt bottoms before tightening therefore you are twisting the head off at the end of the female thread, ensure the thread and hole depth is greater than the distance from top of the mounting hole to the bottom of the of the rail bolt head.

Thanks to both for the replies.

The bolt sheared because it was so stiff I tried using an impact driver . I don't think they're too long as they are bespoke 38mm ones which came with well known aftermarket rails.

A garage has removed and fitted a new captive nut which they made and tapped. (I had made matters worse by using a tungsten l/h bit to try removing the bolt and that also snapped). They've also cleaned the threads on the other one on that side so I'm just awaiting the replacement bolts.

I'm intrigued by titanium for a future upgrade. Freelander 2 2010 [MY2011] FA 2.2 TD4 XS

The roof rail & cross brace setup as a whole is in tension when screwed down. It is difficult to fasten the bolts without bending them. But if done in the right order with the cross brace the setup is ok.

My issue is corrugated roads & the roof rails as is are not up to the task. I had to do an improvised fastening in the outback with M10 bolts & file out the feet of the rails.

I have replaced the M10 bolts back to M6 & a bracket. I would rather the M6 bolts snap than the roof fatigue & crack.

Stiffening up the roof rack as a whole reduces stress on any one foot an any one time. I would rather have 6 light bolts & a solid roof rack than heavy duty bolts & a flexing roof rack.

3 of the 4 crossbars I use are actually bolted together as one so provide a lot of bracing across the whole setup. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

"Stiffening up the roof rack as a whole reduces stress on any one foot an any one time."

Sure about this? I would have thought that a roof rack with a margin of flex would rather distribute the forces more between the foots. What are your thoughts? 2013 SD4 SE (hers)
2013 SD4 HSE (mine)
Ex: 2008 D3 V8 HSE
EX: 2000 D2 TD5

The roof rail is only screwed onto the centre support with a self tapper, which fell out due to road corrugations & the rail was bouncing up & down on the centre bracket. Also squeaking at the front & rear roof brackets.

For the next holiday I fastened the rail & the centre support together with a bolt & Nyloc nut. I then found that the bottom of the extrusion cracked due to too smaller area.

Now with the structural joint I think it should be ok. I don't want the load on the roof acting like a hammer over every corrugation.

Unless you have driven on our outback roads one will not appreciate the damage a 1000 km of corrugations can do. Last trip we had about 2000 km of corrugations in total.

It is not only the physical damage, it is mentally tiring driving on these roads, especially 3 days in a row. How much can a koala bear!

https://vimeo.com/364281135 Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18