univega.duder

My friend wants to add a rear rack to his 1987 Cannnondal ST 500 to be able to haul groceries in panniers. It's an aluminum road bike without eyelets on the seat stay for a rack. I suggested a Tubus Fly rack with a single strut mounting to the brake bridge. Is this dangerous or unsafe? I know the Tubus rack is rated for 40lbs. The local bike shop suggested no more than 20 pounds though I think they're probably considering the lack of eyelets and aluminum frame.

Is he going to ruin the Cannondale? Would a large saddlebag be preferable? Is the bike shop being overly cautious? Would P-clamps be preferable? I'm imagining groceries weighing a total of ~40lbs.

I've attached a photo showing the year and model of bike (not his exact bike) and a photo of how I was thinking the Tubus rack could mount. Would be grateful for any suggestions. Thanks!

cyccommute 

First a bit of a nitpick. The bike does have rack mounts. It doesn’t have rack mounts on the seat stay. That’s less of an issue.

The original Blackburn racks came with only a single stay like the Fly and was meant to be bolted on with the brake. The Cannondale has a flush mount on the brake which makes this kind of attachment harder. You’d need a very long brake nut and would probably have to drill out the tab that the Fly uses to mount it. It’s not the optimal mount.

I would suggest the Tubus Vega with the dual stays. To attach them to the frame, I’d use Tubus clamps. They are more expensive then vinyl covered P-clamps but they are also easier to mount and much stronger. I’ve used them as the upper mounts on an aluminum bike for 12 years and about 25,000 miles without issue. This picture was taken many years ago but nothing has changed.

IMG_0622 by Stuart Black, on Flickr

They are even strong enough to replace the lower rack mounts if needed. I’m not sure I would use them like in the photo below on an aluminum bike but they are certainly more stable and less prone to movement (which might case damage to an aluminum frame) than P-clamps.

image by Stuart Black, on Flickr

As for weight limits, the lower legs of the rack carry the weight. The upper stays are only there to stabilize the rack and load. I don’t see a problem going up to the maximum weight. It won’t hurt the frame. The bike won’t handle all that well with a 40lb load but that’s a different kettle of fish.

univega.duder

Hi Cycomute - Thank you for the excellent suggestions. I think the Tubus clamps could be a great solution. I like that it would allow use of two struts rather than one and they look better than P - clamps. Thank you!

PaulRivers

The Tubus Disco illustrates the easiest way to do this:


The bottom rack mount point has the rear wheel skewer pass through it - giving the rack the same strength as if your bike had rack attachments. The drawbacks is the need to remove the rack to remove the rear wheel, but it's not a huge deal.

fyi, the tubus fly has adapters to go on almost anything - rear wheel skewer like this rack, and at the top a different adapter to mount to the rear brake if needed. I'd prefer this rack for groceries because it's more of a rectange shape on the top though.

bikemig 

Agree with what others have said about mounting a rack on this bike. Also the 'Dale ST series were designed to be touring bikes or sports touring (so people did mount racks on them BITD) and these are overbuilt compared to modern aluminum frames. They are stout bikes and I wouldn't think twice about installing a rack or doing some heavy duty hauling on one of these.

univega.duder

Thanks Paul- I think the rectangular top rack is a good idea as well. It would certainly give a little more stability if something need to be bungied down.

I was thinking I could use the existing holes near the rear dropouts to mount the rack. I'm not sure what these were intended for - I'm guessing fenders. Here's a he photo showing where I think I could mount the rack struts.
​​​​​​​

bikemig 

Fenders or racks. These are strong drop outs and the ST series are stout bikes.

cyccommute 

The Tubus clamps come in various diameters. Measure the seat stay diameter to determine which one you need. If you don’t have a caliper, use an adjustable wrench and measure the distance. The clamps in the picture of the orange bike are slightly narrow for the bike but I made them work.

The Vega Classic isn’t square but it has a slightly wider deck. The Disco is 86mm wide while the Vega Classic starts at 86mm and widens to 100mm.

The other problem I have with the Disco is the same problem I have with all racks that depend on the quick release skewer to mount...they depend on the quick release skewer to mount. Completely defeats the point of quick release. The mounts on the Cannondale frame are capable of handling the rack mount. Make your life (and your friend’s life) easier.

univega.duder

@cyccommute Thanks for the tips on measuring the seat stay diameter. And I agree I'd prefer not to use the quick release mount if I have the option of mounting directly to the frame.

PaulRivers

Those...look like rack mount holes, I think?

Practically speaking, any of those options would work...aesthetically, I prefer the brake bridge mount.

edit: oh, there's another option, I used a seatpost clamp for my brothers bike (axiom trekk seat collar with rack eyelets):
https://www.eriksbikeshop.com/axiom-...?skuId=8012804

cyccommute 

Yea, they are rack mount holes.

While I agree with you that the brake bridge mount is aesthetically better, the recessed nut makes the mounting much harder. The mounting knee (Tubus' term) would have to be drilled out to the diameter of the recessed bolt and a longer recessed nut would be needed. I'm not sure there is enough metal on the mounting knee to drill it out large enough.