Thule bike arms and carbon frames?

Hi all! Anyone have any experience of this type of clamp with carbon frames?

I recently got a fresh rack with this type of arm fitted. Just got around to trying it out today and am unsure how tight I dare clamp it on my carbon frames. The jaws concentrate the clamping forces down a ridge each side of the jaw. This does have pretty firm rubber padding on it but because it’s a thin edge it concentrates all the pressure in a small area. I just snugged it up to the frame and it seemed to hold firm enough but the temptation was there to tighten it a bit more and compress the rubber a bit. Would this be wise or is it best to leave it just snug?

Need to be careful, depends on the frame. MTB frames are generally ok. I have seen a road frame a customer crushed the down tube by winding the clamp up (you could flex some surfaces on that frame with your thumbs though)

I was a no, it was a large chunk of the reason I sent mine back at the cost of £50 postage

Careful ain’t good enough, get a bike carrier that suits. You’re doing something I wouldn’t. I used to work in the trade and have seen a few victims of what you’re doing.

I used to transport bikes for a living. I’d happily use one of those . Just don’t crank it too tight.

Just don’t crank it too tight

But the torque limiter specifies when that is, to me it felt very very very tight

Never had an issue. Used many many times. All MTBs though

Three bike manufacturers I’ve asked about them on customer’s behalf have advised not to use them.

There is a Thule clamp load spreader accessory that is very handy in that situation, costs about a tenner and wraps round the frame under the clamp

From your link it doesn’t look like it’s load-bearing, more just to stop the bike tilting over ?

If that’s right I’d clamp it lightly and maybe wind an old inner tube round the whole lot for extra peace of mind

Had the same concerns, even using the load spreader mentioned above. Bought the Upride carrier for piece of mind.

@ianc, cheers! I will look for that. There is a version of that arm that comes with a torque limiter and seems to have additional padding between the jaws to spread the load like this one.

Cheers all for the many different views(as is usual here :-). I think I will continue to tread carefully with them. Haven’t actually gone any where yet with them on. Just tried them for size on the car. The Fiamma rack on the camper seems to have kinder clamps(actually more like a padded strap), I might borrow them for this rack.

There is no need to tighten these things up at all. They are only there to prevent the bike from swinging back and too so you just need to take up the slack. I’ve used these types of clamps on my carbon bike loads of times with zero damage at all, just tighten up so the jaws contact and compress the rubber a small amount and that is all you need. I tend to clamp to my down tube or seat tube which are circular in cross section. My top tube is tapered so the clamp can slide. But the key is not to tighten the clamp up hardly at all…there is just no need.

@wobbliscott of course you are quite right. There really is no need for these to be overtight. I think it is just one of those things where my head goes off on one and starts imagining the clamp somehow slipping off(which of course it shouldn’t) and the bike flopping over and being dragged behind the car. So I start thinking just tighten it a bit more. Of course, if I really wanted to go belt and braces on it I could fit one of these things and clamp to that as tight as I want.

Of course I can understand the temptation to over tighten. Maybe if you want that additional security then use a bungee as a secondary measure. But seriously even with my steel MTB weighing in at a hefty 33lbs, so well over double the weight of my carbon road bike, I just close the clamps relatively lightly on the frame and job done. Usually try to attach to the seat post but not always possible. Never had an issue even at motorway speeds. The tightness of the clamp doesn’t influence any movement of the bike on the rack so its’ not going to wobble around any more compared to you hanging off the clamp applying shed loads of torque.

Thule are not daft and have been designing these things for years and understand the needs for all kinds of bikes made from all materials so are not likely to design something so inadequate. What they can’t design for easily are the actions of the users of their carefully and excellently designed kit.

If you can’t trust yourself not to over-tighten it, then avoid.

An additional strap or bungee might be enough to set your mind at rest, but I’d say that regardless of the type of rack.

If you can, try to clamp it on to the seat tube where the seatpost will be inside the frame for extra strength. Otherwise, just be sensible with it, certainly don’t crank it up to the max just because you can! It’s the wheel straps that hold the bike in place, the arm just stops it toppling over.

sort answer dont use it on the frame.

I’ve got a few Thule Carbon Frame Protector thingies in the drawer and am happy to use them in conjunction with either this style of clamp (where it doesn’t really need to be super tight) or the traditional Thule 591 roof carrier. Never had a problem with either, even with light road bikes.

That said, I now have a couple of UpRides on the roof along with a couple of older 591s and, obviously, I tend to use the UpRides for the carbon bikes although one flaw with them is that they don’t work with fixed mudguards – an annoyance on my own winter gravel bike, so this goes in the 591 with a frame protector.

In your case, I would probably recommend a couple of those frame protectors, a deft touch when clamping them up and not to worry too much 🙂

@scotroutes yeah, I think now that I can trust myself not to overtighten but still might use a protector of some form. In truth I will probably be slinging a chain lock around it anyway which will be a back up.

@wobbliscott @bails @andybrad yeah, my first attempt was to fix it around the seatpost but the clamp was at an awkward angle so went to the frame instead. Might have another go at the seat tube though.

I have actually been looking at this for the wrong reasons tbh. Although the rack seems mostly very sturdy and well designed. It’s a Thule BackPac . It is let down by the bike support rails. They have sliding extension pieces made out of fairly thin pressed steel. With them at full extension to fit my HB130 they do have a bit of flap in them and the thin wheel strap doesn’t seem to do much in the way of stopping the bike from having a bit of side to side roll along the rail. I had been foolishly thinking having the clamp a bit tighter would help with this which of course it won’t.

I have a couple of spare Fiamma premium rails in the shed which are a much sturdier rail with the sliding chocks and I know from experience that these will hold my bike without any side roll at all. So, I will be fitting a couple of these to the Thule rack instead and all should be well.

Cheers @daern will give em a try.

Used them for years on various different carbon (and alu, and steel) frames, never any bother.

Just bear in mind they don’t need to be too tight, but they can not sit ‘well’ on some frame tube shapes.
I use a boat strap as well, just in case you know 🙂

I had same clamps on a Thule Towbar rack (and similar on a Yakima one) I put them hand tight and then add a strap round the open part of the clamp – started doing this after looking out rear mirror and watching my full suss gently rotate out of view.. I think that movement of the suspension, coupled with wind load pushed the bike out the jaws somehow. It was in the inside of the rack and the wheel straps were tight so it just rotated slowly and lay flat with fork and pedals on the surface of the rack and the outside bar grip a few inches off the ground. Always used a strap since 😁

 I will probably be slinging a chain lock around it anyway which will be a back up.

A chain lock bouncing around and rubbing the frame will do a lot more damage than a properly-applied clamp.

We swapped them out for the fammia arms that wrapround the frame. You can buy them indivdually and they arent expensive and fit the Thule racks no problem.

@scotroutes yes, I will find a way to pad it securely and if I can’t then a strap it will be.

All I used to do with those type of clamps and my carbon bikes was to leave the turn screw ‘locked’. You can turn it and open/close the clamp when there’s no load on it but as soon as it’s slightly gripping the frame, the wheel just spins and won’t tighten further. Sort of like an ultra low torque limiter.
Given the facts that the wheel clamps are actually holding the bike securely and that I used a backup strap around the bikes and rack as well, I never had an issue with either damage to bike from the clamp or with the bike coming loose.

The biggest problem with any frame Carbon or metal with any clamping system is rubbing rather than the frame popping out of the clamp. There is bound to be a bit of relative movement from slight wobbling (which is inevitable) and tightening the clamp just increases this as the clamping force exasperates the rubbing – another good reason to tighten as little as possible.

So I just wrap several layers of tape around the clamp contact point and replace regularly as the clamp wears through the tape and use that as a sacrificial protective layer.

However this is not really an big issue on my light carbon road bike (my only carbon bike) but a bigger issue on my much heavier metal MTB’s.

Cheers All! For the tips and advice. I’m happy enough now to carry on using it.