seat clamp for a rear rack... anything better?

[Jezrant]

A friend is thinking of getting a Specialized Diverge mainly for fast commuting and very occasional touring (1-2 weeks per year). He has a carbon Roubaix that he loves for club runs and finds Specialized bikes fit him well. However, to attach a rear rack on the Diverge, the top stays of the rack are supposed to bolt into the seat post clamp. This looks a poor design, as if it was an after-thought. What's even the point of the lowered/shortened seat stays? Anyway, is there a better way to attach a rear rack on a bike like this that doesn't have proper fittings brazed onto the seat stays? Note that at least the bike has threaded eyelets down near the dropouts.

Bike:
https://www.specialized.com/gb/en/mens- ... 519-133799

Seat post clamp/rack fitting:
https://www.specialized.com/gb/en/speci ... r/p/133425

[Patrickpioneer]

if its not a carbon bike, measure the diameter of the seat stays and order some P clips, the type with rubber. then fit the rack to them.

[Gattonero]

If you look at the design of that frame (IMO, questionable, but this is not the point) the seatstays are quite low so traditional bosses won;t work well with the normal struts that are used in most pannier racks. Is bette to clamp the struts high, you get a better bracing.
Also any damage is quick to repair by replacing the seat collar -widely available from different brands- rather than removing+pressing a rivet-nut. The section of those seatstays also won't work well with rivet-nuts, and are likely to be thin gauge so easy to flare/wear...

[Gattonero]

if its not a carbon bike, measure the diameter of the seat stays and order some P clips, the type with rubber. then fit the rack to them.

That tubing is likely to not be designed to carry a load in such way as a p-clip and a rack will do. Ought to be the reason why there aren't threaded bosses.

[pwa]

The problem exists because the frame's seat stays meet the seat tube lower down than is usual, so the usual fixing point is taken away. With most racks the rack stays will actually be angled upwards (requiring a bit of bending?) to reach the seat post clamp, but I reckon that may be the neatest solution.

[Jezrant]

I don't understand the point of those lowered seat stays. I've also noticed on the Specialized website that the chainstays are very short too (422mm). Isn't that a bit too short for a rear rack? Unless the rack was adjustable or meant to be further back than normal, wouldn't the rider risk clipping the panniers with his/her heels?

[Gattonero]

I don't understand the point of those lowered seat stays. I've also noticed on the Specialized website that the chainstays are very short too (422mm). Isn't that a bit too short for a rear rack? Unless the rack was adjustable or meant to be further back than normal, wouldn't the rider risk clipping the panniers with his/her heels?

It's not a touring bike, has a short wheelbase and rear end for a purpose.
The brand has made a series of "bikepacking" bags so they may have deliberately skimped on the options for traditional bags

[thirdcrank]

From Specialised's own description

With the Diverge Sport, you'll be prepared for anything, from smooth tarmac to the loosest, roughest tracks out there. It's packed with all the same technologies as its pricier cousins, only its spec places an emphasis on reliable performance, not components so flashy you'll be eating nothing but top ramen for months.
(My emphasis.)

Except it seems you won't be. I can understand how modern marketing means people can end up with a bike that is unsuited to their needs, but why on Earth buy a bike that doesn't tick all your known boxes? (I think box ticking is the correct cliché for the marketing. )

I had to look up "top ramen" which seems to be some sort of pot noodle. I won't be listing it as something I learned on the forum because I'll have forgotten it soon.

[pwa]

Probably enough heel room for small panniers (Ortlieb front rollers?) if your feet are not too big.

[Gattonero]

From Specialised's own description

With the Diverge Sport, you'll be prepared for anything, from smooth tarmac to the loosest, roughest tracks out there. It's packed with all the same technologies as its pricier cousins, only its spec places an emphasis on reliable performance, not components so flashy you'll be eating nothing but top ramen for months.
(My emphasis.)

Except it seems you won't be. I can understand how modern marketing means people can end up with a bike that is unsuited to their needs, but why on Earth buy a bike that doesn't tick all your known boxes? (I think box ticking is the correct cliché for the marketing. )

I had to look up "top ramen" which seems to be some sort of pot noodle. I won't be listing it as something I learned on the forum because I'll have forgotten it soon.

As much as I agree wit some hype (and I don't like the frame design), you should read the whole sentence or at least a few more words

you'll be prepared for anything, from smooth tarmac to the loosest, roughest tracks out there.

There ARE bosses where is practical to use them, by the dropouts. To have them on low seatstays is useless, have you ever tried to fit a traditional rack on a normal frame of a very small size? Good luck with that, you're 100 times better off by using a seat clamp with threaded bosses, it's easier and offers a more stable connection.

[Gattonero]

i.e. imagine if there were bosses on the seatstays of this frame, the bracing angle would be quite bad if compared to the existing solution. The longer and the more angled are the struts, the more side flex you get.

[thirdcrank]

... you should read the whole sentence or at least a few more words ... .

I really did read every word (my evidence for this is my comment about the pot noodles whose name I've already forgotten )

All I was trying to say was, given the vast range of bikes now on sale, why pick one where you need to ask a friend to post on an internet forum to find a wor around for something you think is important? Tarrant rules, OK?

[Gattonero]

You underlined the words "prepared for anything", if those are read alone you may think that is a bike that can really do anything, but the whole sentence is about the terrain not about a wide spectrum of cycling disciplines. In fact, there's no such thing as "universal bike" that is very good in all conditions.
I don't see the big deal in that bike per se: it's a bike for bridleways, light singletrack/offroad that doesn't involve drops, and the likes. You may even tour the world with it, though if I was to stay on the tarmac I'd choose a proper road bike for that, it gives you the chance of take the diversion off the smooth track without slowing you down.

[Brucey]

bikes with compact geometry frames and disc brakes are less easy to fit racks to than models that don't have these features. I wouldn't worry too much about the upper mounts for the rear rack; if you use the right rack its lateral stiffness is mainly to do with the rack design and the lower mounts, not so much the upper mounts.

Depending on the priority of loaded touring (not to mention how big the load is) your chum might get on OK with these mounts (some of the load can be carried at the front of course) or they might be better off with 'a proper touring bike'.

If a proper touring bike just isn't trendy-looking enough, consider something like a Genesis Croix de Fer instead. This is basically a touring bike in a slightly more fashionable frock. Still has disc brakes and long rack stays though.

cheers

[Gattonero]

A couple of thoughts about that Specialized seat collar with rack mounts.


Like many collar if this kind, the closing bolt is not hinged with a nut on the opposite side (which is much better distributing the torque, and can be replaced), however if it's really available in several sizes as they say - 29.8mm, 31.6mm, 31.8mm, 32.6mm & 34.9mm- this means that the perfect fit can be achieved to the OD of the frame tubing, thus minimizing the bend of the closing bolt that will inevitably happen as soon as the collar fits a tad loose on the frame.
It also seems that the closing bolt is made in two sections male+female instead of having a bolt threaded directly in the alluminium. This is a good idea as far as strength, but means that a standard bolt cannot be used should it fail.
I also wonder how long is the thread available for the rack mount bolts to engage onto, and how forward the rack mounts will be as they are in fact co-axial with the seat collar closing bolt.

Many other designs would move the rack mounts below, in a better position. Though I don't like the collar closing bolt that threads directly in the alluminium.


To me, a better design seems the Salsa collar:

Not a fan of welded alluminium sections, but this collar has got many advantages.
For a start, it's available in 27.2mm ID so can clamp directly on a seatpost (not having to remove the frame original collar). Then has got a hinged bolt, and it looks like it's a standard M5 bolt that can be replaced anywhere anytime (the opposite side is drilled so any bolt that is long enough will do). Plus the rack mounts have a very long thread, which is always welcome especially in alluminum.