smasha

The hard part is identifying and finding a suitable fork. Rigid aluminium forks that accommodate racks are not really fashionable.

It may be easier to have braze-on eyelets installed on this fork. Under the circumstances, that's the solution I'm hoping for, at this point.

smasha

If I was setting this up as an on-road touring bike, and just using the front bags for a sleeping bag and a puffy jacket, I could probably get away with some hack that puts a bit of downward bending force on the lower mounting bolts, even though the manufacturer now advises against using a front rack with this fork.

But setting this up as a grocery bike, on which I'm likely to push the rated weight limit of the front bags and front rack, that's not a good idea. I really do need to minimise or eliminate the leverage forces on bolts used to mount load-bearing racks.

With this in mind, I'm starting to think "the solution" may be braze-on eyelets installed on the fork. I think that meets your criteria of not being packaged, labeled and hanging on a peg behind the sales counter. What I need to do now is find a frame-builder who can assess the feasibility of this, and hope that the manufacturer is willing to make a good-faith effort to cover that cost, after advertising the bike as being compatible with a front-rack, and advertising their front-rack as being compatible with this bike.

lasauge 

Two thoughts that I'd add here: why not use a mid rider rack and just double up rack and fender struts on the same bolt? And second, I'd have to do a test fit to be sure, but looking at the pictures I'd think you could make a rack work with that lower threaded hole as long as the strut comes in from the front - just add a leather washer or two and that will take care of the dropout not being flat.

Ironfish653

Ok, lemme get this straight; you intend on having so much load on this rack, that any possible offset from the dropout will fatally compromise the single M5 bolt tasked with supporting all this tonnage?

Being that none of the proffered solutions are acceptable, let alone "perfect;" the most obvious course of action is to have the desired mounts welded to the fork, and that the manufacturer should help cover the cost of modifications, because they didn't anticipate that you would want to install a particular rack on your second-hand bicycle? Got it

​​​​​​

smasha

Flat or not, that would still be pushing a downward leverage force on the bolt. It's actually worse than nothing. With a "naked" bolt, the downward leverage is only there when the rack is weighted. With extra fittings, the downward leverage is there when the bolt is tight, and increased when the rack is weighted.

oldbobcat

Since the fender strut would face rearward and slightly downward, it would have no trouble being mounted on the outside.

But yeah, a thick washer and a longer bolt would make it a dandy mount for a rack stay.

smasha

Over time, this is kind of inevitable, given the leverage forces that would act on the bolt.

If braze-on eyelets can be installed, they can be installed so a rack will mount flush, entirely eliminating any leverage forces on the bolt. No other proposed solution accomplishes this. It also solves other problems, such as clearance from the QR skewer.

Since the manufacturer advertised the bike being compatible with a front rack, and also advertised their front rack as being compatible with this bike... But now, only after I brought this to their attention, they say that was all incorrect... Yeah, it does seem reasonable to request that they make it right, or cover the cost of making it right.

smasha

As I noted, above, that's actually worse than nothing. With a "naked" bolt, the downward leverage is only there when the rack is weighted. With extra fittings, the downward leverage is there when the bolt is tight, and increased when the rack is weighted.

Ironfish653

I think you’re grossly overestimating the force vectors involved here, and also underestimating the margin of difference in a flush joint -v- 1-2mm off spacers. A flush joint will support the hundreds of pounds you intend to carry, but a >2mm offset will cause the bolt to bend?

If I was installing this rack, I’d either use a couple brass crush washers to fill that gap, or an aluminum sleeve, beveled to match the profile of the fork. I could probably do it in about an hour, with the materials in my garage.

You could also upgrade the mounting bolt itself; instead of the Grade 5 SS typically used, you could get higher strength Grade 8, or source some NAS “Aerospace” grade hardware.

oldbobcat

I'm assuming, this being a front fork, that the load on this rack would be no more than 20 lbs. And, of course, the washer and bolt head fit flush to the fork and rack. Assuming he's not going to give his girlfriend rides on it. Obviously, don't us an aluminum bolt intended for mounting water bottles.

smasha

What's led you to believe there'd be a 2mm offset? The actual gap between the fork and a rack flange would be at least 7mm.

smasha

Grocery bike, it could hit about 20lbs, per side.

I'm not sure what pictures you're looking at, but part of the issue here is that nothing but Silly Putty will fit flush with the bottom eyelet of this fork.

And with at least 7mm between the eyelet and where a rack flange would be, this is not a good idea with most any material used to make M5 bolts.

oldbobcat

I'm seeing it all to clearly now. Thanks for your patience.

Ironfish653

This picture you posted.

All I can really evaluate is the variation from “flat” around the bolt hole. I don’t have either your bike or the rack, so I can’t tell what sort of other clearance/interference you’re dealing with.

I’m sorry you ran into a hardware incompatibility. It’s frustrating when that happens.
You can either improvise / adapt or scrap it all and start over.
Based on my experience, this is not an insurmountable situation. There are a number of things that have been proposed that should yield sufficient results. Being that they are improvised solutions, you may have to try them to see if they work; there’s no off the shelf fix here.
Insisting on ideal seems a strange hill to die on for something as inconsequential as a grocery bike

smasha

I suppose "ideal" can have slightly different meanings, in different contexts.

So far as I may have used of the term "ideal" in this context, I mean I'm not going to have a catastrophic failure that pushes a loaded pannier rack into the front wheel, while I'm riding along a busy highway and/or doing 50kph.

To achieve that ideal, I want to get the rack flanges flush with the eyelets they're bolted to. This will likely require the installation of braze-on eyelets. I'd like to think this is not an insurmountable situation, but it's a PITA, and a disappointment, and the whole project is on hold while I wait for an update from a frame-builder.

grumpus

I'd be inclined to mill* a flat around the hole so that a spacer can sit level. Use a cutter with a radiused outside edge to avoid creating a stress riser.
* a drill press** will do fine, and you could probably just regrind an old drill bit rather than invest in a milling cutter.
** or even a Dremel type tool, a small spherical burr and a steady hand.

smasha

That could solve the problem of a spacer/standoff/washer sitting flush against the fork, but it does not solve (1) the problem of the bolt extending about 7mm out from the fork, to where the rack flange would be, thus creating a lever, and (b) there would still only be about 5mm clearance between that bolt and the QR hardware.

grumpus

ITYF the clamping force of the screw is sufficient that the bending stress is not a problem as long as the spacer clamps properly between rack and dropout, and the screw head clamps properly on the rack. I'd use thread-lock, and check the screws after the first few loaded rides.
Looks like plenty of room for a 12 mm spacer.

smasha

Seems like a lot of work for a solution that's far inferior to having braze-on eyelets installed where they'd work well. Assuming that braze-on eyelets are a viable option.

Troul 

imo, it would make more sense to use the "designed" fork that the OEM intended to achieve what you are after wrt using a rack.

rumrunn6

fwiw - you can cut a washed w/ a hacksaw, if you wanted to knock off the top of the bottom one

smasha

I've got the Tubus Tara rack here, and playing around with it, the fit may not be as bad as I thought.

Pictured, below, is from the Tara installation manual. The red piece is an optional spacer/standoff, 8mm long x 8mm OD.

Based on this, an 8mm spacer with an 8mm OD should be fine... If it sits flush with the face around the eyelet.

So now I'm reconsidering a counterbore around the eyelet. I think that part of the dropout, below the weld, is solid. If that's the case, I don't think an 9-10mm ⌀ counterbore, about 2mm at the deepest point, would put me in any danger.

This would leave the rack close very the QR hardware, but not touching.

This would also put the rack a little off level, but I've seen much worse.

I'm not sure about adding braze-on eyelets now, as the flat-mount brake is kind of where I'd want to put eyelets, on that side. It may be feasible, it may not be.

As always, looking for constructive thoughts and opinions from everyone else here.

smasha

What fork is that?

smasha

Just put half a washer under the bolt? I was thinking about that, but if the bolt loosens itself, I'd lose that half-washer. It's a high maintenance solution, and it still wouldn't sit flush.

rumrunn6

sorry, don't cut it in half, just chop off a little bit leaving some metal around the hole. I did it once for a diff. purpose & have a pic ... somewhere ...

post #20 here



but I agree. high maintenance because every time you remove the wheel you'll have to mess w/ it to keep the washer facing the right way