shauramo

Probably the millionth question about rear rack attachment, but this was a little difficult to search on google or forums. Here goes:

I have a Univega XXIX (Rigid 29er) with no rack eyelets. I have fiddled with Tubus clamps before on another bike, so I am aware of their existense. The seatstays of the frame are quite a bit curved, so I was thinking about another solution. At least Tubus makes QR axle adaptors, but does anyone have experience - or an opinion - in combining the axle-mounting with using one of those seat collars with rack mounts (e.g. by Salsa, ProblemSolvers etc)?

As I would figure this would be an easier installation compared to Tubus clamps. My only concern with this is that the attachments points would then be somewhat further apart than what they would be if there would be rack mounts on the frame. The seat collar would not be super high, as the top tube is sloping. The seat collar's vertical height would be roughly a couple of centimeters / 1 inch above the parallel line of the top of the rear tyre, to give an idea what I would be working with. Sure, at least medium-long struts would be needed for attachments.

I know using the QR axle mounting lowers the load capacity a little, but I am not embarking on a world tour. So in conclusion, do you think this setup would be too flexy/wobbly, and should i consider tubus clamps instead of the seat collar? Or, do you think that seat collar is the sturdier than the axle mount, and a combo with seat collar and tubus clamps would be better.

I think using two pairs of tubus clamps / p-clips would be a) a little pain due to the bent seatstays and b) quite ugly.

Thanks in advance!

djb

I set up one of my wifes bikes with a qr mounted rear rack (axiom streamliner) so I can attest that it works fairly well, and within reason for weight, is a good solution. Its a bit of a pain in the rear removing the rear wheel, but not a big big deal.

personally for the top parts, I figure the wider stance of using p clamps instead of the seat collar woiuld be an advantage to stop rack "wagging", but honestly I think it will come down to how much weight you put on it, and how well you end up doing the attachment points.

I suspect there is no black and white answer here, but that you will have to try things with your load and see what works better. At least here, the cost of trying diff attachments is fairly small, so you can try diff ways.
I guess though the rack choice will be a factor. Look up the Axiom streamliner rear rack, you'll see that it does have these "setback" metal pieces at the qr point, to move the rack back a bit, as it is designed for bikes without eyelets, like roadbikes, which have shorter chainstays. This advantage of gaining 2 or 3cm or more is a help for not hittnig heels on panniers, but again, some panniers have diff shapes than others, and sizes, so again, lots of variations.

re looks, I'd just go with what works best, but you will have to load up panniers with what you are thnking of taking to really see how it works in real life riding.

consider also that slightly wider tires and or slightly less pressures will help things in having less jarring forces going into the frame and therefore rack, which in this case might be a help.

seeker333

The seatstays on your bike (and most others) are not straight but you can still attach rack stay mounts to them. I'd worry more about function than fashion here, even if it's "ugly". Either way it's going to be ugly compared to fitting rear rack to a proper touring bike.

The distance (length) of rack stays matters somewhat, as longer equates to less control of load, so likely more (lateral) movement of load and rack. The lateral movement/deflection is what kills racks, especially the Al ones. For this reason I would go with closer (shorter stay length) attachment to seatstays rather than seat collar. This way you don't have to buy extra long stays, plus that funky seat tube collar might cause seatpost to slip (potential to create a new problem). I assume you refer to these Tubus accessories:

https://www.tubus.com/product.php?xn=60

https://www.tubus.com/product.php?xn=33

shauramo

Thank you very much for the replies!

Yes this seems reasonable. I just wanted to ask, since I gave a possibility to "no difference between seatstay and seatcollar attachment, since [insert a engineering-inspired answer here]" I was more focused on the difference in mount height/distance, than on the "width" of the mounting points.

Yes, I am looking for a solution that works. I can manage ugly, but wanted to see opinions. I think anyone will choose the most clean looking setup, if the functionality and sturdiness are not questionable. But I believe that this is not the case, and that the clamps offer a much better solution overall.

Thanks! Although I am inexperienced in heavy load carrying, the setup I am now planning would have to be something I can count on.

Yes, these parts exactly.

SEAJAYBIKE

THIS. THULE TOUR RACK. I've installed them and they are SOLID as a rock. Thule bought this design from Freeload. It has been around quite a while.

Aubergine 

I have used a Sunrace (I think) seatpost rack mount with good results. It has two arms so is about as stable as mounts on the seat stays.

fietsbob

Old Man Mountain is another source of a QR axle mounted rack, & Tubus * makes an adapter piece to use that kind of mount, as well ..


*mentioned above..

Of course towing an Extrawheel trailer, It carries the pannier racks and uses the skewer as its tow fork mount..






....

seeker333

If you use the Tubus seatstay clamps, I recommend using rubber (cut from old inner tube) or 3M Super 88 electrical tape under the clamps to protect finish from abrasion.

You may need to factor in the additional tube diameter from this protection layer when measuring seatstay diameter (they come in 5 sizes, pick closest).

djb

despite what I said about the width aspect, the axiom rack on my wifes road bike is made for mounting on a road bike rear brake caliper, so just one mounting point onto the bolt that holds the rear brake to the frame, and it works fine--but again, it depends on how much weight you are talking about. She has never overloaded that bike, but even with just one pannier on and a reasonable weight , the one point support has worked fairly well.

Kontact 

I have a hard time seeing why a axle QR mount would ever be weaker than using braze-ons. If a QR can't move during sprinting forces on the wheel, how is 40 pounds on a rack going to budge it?

shauramo

Thanks! I took the "lower load capacity due to QR use" as given from qr adapter description by manufacturer (not sure if was for tubus). I personally thought that the QR wouldn't be the problem, if there were no braze or p-clip type clamps, but the seatpost collar use.


I have looked at the Thule rack, even read a review on it where someone with experience on racks was surprised it was so sturdy. One side of me thinks it's pretty cool, but somehow I would consider this more an option for the fork (obviously it is meant to work at both rear and front). I think the curved seatstays and cables on both seatstays would make attaching the Thule a little troublesome. But I might be considering it for the front, as at some point I will have a child carrier in the back (seattube attachment), so it might be wise to share some of the load to the front (and some will probably argue that loading the front is better than back anyways, but we don't need to get into that now and I am no expert on this, as you probably can figure)

3speed

My last touring bike had eyelets on the dropouts, but not on the seat stays. I used a seatpost collar mount with a rack strut going to each side. It was perfectly solid for a 1,000mi trip. Zero problems. I noticed a lot more sway from my old steel Trek touring bike with a solid bolted on rack than I did with the newer bike and the collar mount. I personally wouldn’t worry aboit that aspect of it. I bet of you aren’t putting more than 20lbs on that rack, you’ll have no problems as long as the QR mount is rated for it.

Also, I didn’t know Univega was still around. Weird.

Kontact 

Just to be clear, while the QR as an attachment point might be incredibly strong, that doesn't mean that a particular manufacturer's QR rack is as strong as the eyelet design. Many QR racks use a pretty long lever arm to move the rack back for heel clearance, and that might be an issue for heavier loads.

So while I would trust the dropout mounting point, I would be inclined to take the advice of the rack company about their product's capacity.

I have also seen QR mounts that didn't look like they were providing enough overlap with the QR head, possibly causing the QR to bend as it is tightened down (Axiom Streamliner). Unlike a bolt, the head of the QR is mostly hollow and really just engages along the edge. If that's what's happening it is bad news.



And if you are going to use P-clamps, don't use electrical or any other adhesive tape under them. The adhesive tends to act as a lube under clamping pressure and makes the clamp creep. Thin, rubbery plastic is ideal.