Technical Hmm, that didn't go well🙄

[Myusername]

So today I set about fitting my set of longitudinal roof rails. I wanted them because:

1. They will immediately imply to passersby that here is someone with an active lifestyle, and probably very attractive, as well as making the car look better, plus...

2. A vague afterthought that they might be useful...

So how hard can it be? Weeeeellll...it didn't go well.

Both the fixing bolts and the treads in the roof appear to be made of melted chocolate, and I am not convinced that they are firmly enough attached to withstand the aerodynamic load of either a bike or a roof box. In fact, movement can be felt with the n/s rear fitting.

Has anyone else has the same issue, and if so, how did you resolve it?

I'm thinking of new bolts with an ever so slightly larger thread to cut into the roof fitting, but don't know what size the bolts are (I'm not really very techie.).

The thoughts of the collective appreciated as always.

 

[A3jeroen]

I think they are normal M6.
Don,'t use anything else!

gr J

 

[koalar]

I think they are normal M6.
Don,'t use anything else!

gr J

I believe you are correct

the bottom of the OEM longitudinal roof bars I have seen, fit into the dimples of the roof. Once snugged down its going nowhere unless both bolts grow 10mm give or take

 

[Myusername]

Oh the bars fit perfectly into the dimples in the roof, and look great. Just the threads in the roof are not good.

 

[koalar]

a 1/4" Grade 5 lag bolt starts to fail at 13000 lbs (6mm is slightly bigger)

The rails will fail long before the bolts as long as the they are correctly tightened.

I "think" the engine lifting eye is only 2x 6mm in aluminium

Fiat vans are sometimes get drilled out to 8 mm when someone has damaged the thread. Its not needed as it weakens the rails. I not tried on a panda I suspect 8mm would also be possible but you are on your own. Measure twice first.

 

[rmjbn1]

Did your roof have plastic plugs in the holes for the roof rail bolts? And did they unscrew OK?

The plastic can go hard with age and might have left some detritus in there.

I would try running a bolt in and out of each hole with the roof rails off to check each thread.

If any don't feel right, I'd have a go at digging/flushing any gunk out of the hole, then run an M6 tap in them to clean up the threads.

As you say, it needs to be tight!

 

[koalar]

In fact, movement can be felt with the n/s rear fitting.

this is not correct

should be solid

take it apart and inspect closely

OEM roof bars or third party ? second hand or new ?

 

[Myusername]

They were from a breaker and fit perfectly.

The plastic caps were a pain to get out, but I made sure the holes were clean, and ran a bolt in each one before fitting.

The driver's side was ok, although I don't think too much force would have been needed to strip them too. The passenger side holes were really problematic.

I'll order some new bolts and try them.

 

[DaveMcT]

It's likely your bolts are too long and hitting bottom before they pull the bar brackets into place. I would suggest you use at least 8.8 spec zinc plated and cover end to end with a good stiff anti-seize paste.

 

[koalar]

The driver's side was ok, .

swap the bots over would tell you if the bolts were the problem before ordering anything

 

[rmjbn1]

Good point. It's possible they gave you the wrong bolts. Just whipped one of mine out, M6 bolt, 25mm shaft, fitted with two washers.

Oh, and did yours come with the rubber gaskets to fit under each mount?

 

[Myusername]

Yes, rubber gaskets fitted, and measured the bolts, 25 mm length.

 

[rmjbn1]

Hmm, if the bolts are good but don't feel snug in the holes and won't tighten, then I'd guess it's likely the hole threads are damaged.

If that's the case, then as koalar says above, the only option would be to drill it out to take the next size up - don't try and force a wrong bolt in there, it'll just strip the thread and won't be secure.

You'd need to drill out with a 7mm bit (technically 6.75mm if you can find it, but, well, good luck) and then cut a new thread with an M8 tap (standard thread pitch for M8 is 1.25mm)

You'll also need to enlarge the holes in the rails to take M8x1.25 bolts.

These little jobs are never as easy as they should be, are they?

 

[koalar]

Hmm, if the bolts are good but don't feel snug in the holes and won't tighten, then I'd guess it's likely the hole threads are damaged.

If that's the case, then as koalar says above, the only option would be to drill it out to take the next size up - don't try and force a wrong bolt in there, it'll just strip the thread and won't be secure.

You'd need to drill out with a 7mm bit (technically 6.75mm if you can find it, but, well, good luck) and then cut a new thread with an M8 tap (standard thread pitch for M8 is 1.25mm)

You'll also need to enlarge the holes in the rails to take M8x1.25 bolts.

These little jobs are never as easy as they should be, are they?

you can try and clean out the old threads with a M6 plug tap first. M6 tap is always good to have in your toolbox as its one of the most common size bolts.

.

 

[DaveMcT]

The roof lugs are about 15mm diameter with M6 hole down the middle. Depth to bottom is about 20mm. You need a bolt that's 15mm longer than the thickness of the roof rail. Any more will hit the bottom of the hole before the roof rail is held down. If the threads are damaged, the easiest option will be to tap to M8 and be done with it. Use a tapping block to keep it perpendicular.

I don't have a roof rail to hand to check, but socket cap screws might be the best option. DO NOT USE STAINLESS and always use a good anti-seize all the way up the threads.