Front Platform Rack Mounting, failure risks, etc

[PrairieCrowBikeworks]

Talking platform-style front racks here. More specifically, platform racks that are mounted to fork at the crown and a midblade eyelet, no strut running all the way to the dropout. For extra heavy duty porter style racks I run a strut (or struts) to the dropout to support the rack fully, but these racks stiffen the fork considerably, and one of the goals of the platform racks in question is that they avoid that.

How do you choose to have them mount to the fork? I build racks with 3/8th cromoly for all my custom frames. I have made racks with 3 points of mounting as well as 4 mounting points, and have not had failure on any, even on my own 3 point racks which I have overloaded to the point of making the bike unridable, as well as crashing hard. There are times I worry about my racks that use that singe mounting point in the crown- if it fails while loaded on a rough road it can lead to very sudden wheel lock up. The easy way to reduce this risk would be to only build racks that use 4 mounting points, but my frames are lugged and my customers are into their fun carved fork crowns, so I try to have the rack either stay out of the way, or compliment the crown. This is why I have so far avoided added eyelets through the top of the fork crown- I like that big flat space, evoking early MTB styling. On a bike getting direct post mounted centerpull brakes this isn’t an issue, I just use the centerpull mounts for 2 upper rack mounts, but with the Cantilevers it gets stickier, and my next 3 customers have asked for cantis. Is a well built three point rack really something that is just for 5 or less lbs, or am I overthinking it? I’d love to be able to keep building these without losing sleep over my pals losing teeth, the 3 point is just easier to integrate into the cantilever equipped lugged dinosaurs that I love making.

These bikes aren’t “mountain” bikes but they aren’t restricted to the road. These riders will likely load these racks with weigh ranging approximately between 6 and twelve packs of liquid, (a twelver of cans weighs 13 lbs) or that weight in camping gear or food on a quick stop at a grocery store. I know I do. I’ve loaded mine with multiple 6" 4x4 timbers. Racks will get overloaded eventually, if not by the first owner of the bike, the second. All of my customers end up up camping/touring with their bike, even if they didn’t order it for that.

On a few of my frames/racks that have racks and cantis I’ve built the rack so it mounts to the midblade eyelet and to the canti stud, but this can lock the customer into using that exact canti model forever, since different models of cantis sit higher or lower on their stud and my racks aren’t adjustable. I also found this set up to be more prone to brake squeal so I’d like to avoid it.

I’ve heard a few anecdotes of broken front racks that were supporting wire baskets that were ridden heavily loaded on rough but not crazy terrain. I’ve only ever seen the small VO ‘rando’ style racks fail myself, in my retail bike shop days, and those were also likely heavily loaded (like a 12 pack of beer weight). Usually these failures were on racks that used the separate bendable slotted or drilled ‘tange’ to attach the rack to the fork crown. Everyone that sells the nitto front racks seems to have stopped saying “just strap a basket on it and live in paradise” and now says “don’t put a basket on it or overload it!!” . On Crust’s website they state the weight limit of one of these Nitto racks as 4.5 lbs. If I’m build racks to carry more than that should they be 4 point mounted?

I see a lots of other builders making racks that just use a single pass-through bolt at the crown, and plenty of these bikes are advertised as rough road randonuer bikes - how to do you talk to customers about weight limits? Or is the pass-through bolt design actually just so tough that if done right it’s not a risk?

Here are a couple pics of the rusty old prototype on my daily. Single pass through bolt at the crown. I’ve ridden it loaded with 15lbs off road plenty and I can find no signs of stress/damage. Super stiff.

Here is a more recent platform rack (ignore the separate pannier rack), still using a bolt that passes through the fork crown. This rack has the added cantilever stud mounting point that I’d like to avoid… This rack design feels super burly and it leaves the crown nice and visible. I also add a large washer that is brazed directly the the pass through bolt on the rack end, to help stabilize that and reduce any flex side to side.

While I value the form of the 3 point rack, is the increased strength of the 4 point worth it for the function side? Your thoughts pls. Thaaaanks.

[bushtrucker]

I’ve always liked racks with 3 mounting points — especially the Nitto ones that mount off the canti studs — and find them stiff enough for a bag or small (137) basket. I wouldn’t want one with a super wide porter style deck on it as I’ve found they can twist pretty easily with wider loads. The exception being a Pass and Stow rack or I guess any rack that has legs/supports that connect at the dropout.

Since the rack you’re showing there has a deck that’s a lot wider than the fork I think two struts wouldn’t look out of place at all. And maybe best to err on the side of caution since you can’t really provide a load rating to the customer and a front rack failure will almost certainly be pretty catastrophic.

[manzanitacycles]

First off, your racks look really nice, especially the low-riders. That’s a lot of work right there

I’ve made a few lightweight rando racks and only one beefier porteur rack. That rack used 4 mounting points, mostly for added stability. I would think a 3-point porteur rack would twist a bit when loaded down, affecting handling.

As you can see in the photo, the 4-point rack didn’t hide the crown lug. If I were you I’d go with a 4-point design for added stability and strength.

[olivia_violet]

I have made a few “rando” style racks with three mounting points like you show, I’ve made them with silver brazed stainless so they are not terribly strong and ive definitely overloaded them pretty heavily. I’ve always been a bit nervous about this as well.
I had one fail with a heavy basket on it, it broke near the single top mount, luckily I had the rack attached to my aluminum fenders so it bent forward and scraped on the wheel, but it didn’t lock up the wheel catastrophically like you might have expected. So I guess a fender can act like a fourth mounting point.
Using a handlebar bag mounted to a decaleur also makes me feel more comfortable putting a heavy load on the rack

[Alex]

3 point racks have a catastrophic failure mode that usually involves a header and hospital trip, so I try to do 4 points if at all possible. The failure is that the fork crown mount breaks and the rack pivots forward, jamming against the tire and turning into a self energizing brake. I’ve had it happen to two racks made in my shop, one was on my own bike and the 4th fender point caught it. The other was a rack that a friend made for his bike and it caused a bad crash. Rivendell had it happen with enough Nitto racks that they recommend a safety strap between the bars and tombstone.

I like to run the stays from the fork blades to the outer perimeter of the rack instead of straight up. It makes for a much stiffer rack.

I usually put in a cross brace at the right spot for Ortlieb hooks to act as a decaleur with my handlebar bags. Bigger racks get lift the dot snaps around the perimeter for my porteur bag. Here is a 3 point rack with both features, scroll through the pics to see both bag setups.

Gifford - photos.alexwetmore.org

A 4 point rack that I made for an ex:

Modified Soma Mixte - photos.alexwetmore.org

A light 4 point rack: Lightweight rack for bottom mount Ortlieb hooks | Very light… | Flickr

Screenshot from IG post where the grade 8 crown bolt broke on a 3 point rack:

It’s a 5 bolt rack now:

[PrairieCrowBikeworks]

That is exactly the type of failure I am concerned about, @Alex. Mine are also usually connected to the fender, which might help a bit depending on how loaded the rack is and the terrain. But I think it’s a real good argument for avoiding the 3 point rack type for racks that will hold much cargo.

[PrairieCrowBikeworks]

Thanks for all the replies- they are all super helpful! I think I have come up with a location for a second set of struts that will satisfy my aesthetic goals as well as the structural needs. That bolt break that @olivia_violet and @Alex describe and show is exactly what I am worried about. The ‘5 bolt’ rack in the last picture is probably the direction I’ll go in in the future, or something like it.

I’m still interested in hearing any additional rack failure stories, as well as the materials and designs others have used (with positive or negative results).

Just a little more info on mine- I build them with cromoly from Aircraft Spruce, 3/8th O.D. and the .028 wall thickness. I’ve used a couple other cromoly sources but they didn’t bend as nicely in my experience. I primarily use bronze for all the joints on these racks. For the struts/stays that run from the fork blades up the platform, while they may look like they are parallel to each other, due to the spacing of the platform rails, they converge enough to get some triangle structure happening which seems to make the rack rack much stiffer. Not always running to the outermost edge of the rack but getting some (if not as much) of the same effect in terms of side to side stiffness. So far I’ve liked the look of the “overhang” on my platform racks, like a wing or balcony, emphasizing certain lines, but another strut running to the outer edge might offer enough that the change/compromise is worth it. I have a friend who went over his handlebars (not rack related) years ago and had to have his jaw reconstructed, and I’d like to do what I can to minimize the likelihood of a rack I build contributing to a fall like that. Risk never reaches zero I know but I’d like to help it remain low.

[PrairieCrowBikeworks]

That is exactly the kind of breakage that I’m worried about @olivia_violet. I do the same with fender mounting on most customer bikes but I worry with a heavy load and rough terrain, where failure is most likely to occur, it might not do enough, especially with a knobby tire. But it didn’t happen in your case, so maybe this sort of failure is not as much of a “guaranteed total disaster” as my mind has made it into. Glad to hear it wasn’t in your case at least!

Brazed stainless sounds great from a finishing standpoint! I’ve always thought stainless racks with silver fillets look great. Enough people seem to build them that they work for a certain amount of cargo.

[PrairieCrowBikeworks]

Thanks @manzanitacycles for the kind words, they are a lot of work aren’t they? Lovely rack in your picture as well, from what I can see!

[olivia_violet]

Really interesting reading this, thanks Alex.
This thread is making me rethink how I make racks.
I feel comfortable with the three points design for holding up a bag that is supported be a decaleur or the handlebars. But I think I need to come up with something new for a basket or other load that is only on the rack

[olivia_violet]

I started using stainless because it’s what I can get locally without ordering a minimum of 20’ (this is just a hobby for me)
It looks great and doesn’t require much finishing but the silver joints on small tubes just aren’t that strong, I’d like to try making some racks with chromoly and then having them nickel plated in the future

[Alex]

4130 holds up remarkably well without paint. I have one rack that has been bare for over a decade (because I planned on getting it chromed, and haven’t made the trip yet) and it really doesn’t have any rust. I made one big rack for a cycletruck out of stainless and it looks awesome and has held up well, but it is also heavier (since stainless is weaker), cost a lot more, and took more work.

The fender mount can be a 4th point and is what saved me from going over the bars when that fork crown mount broke. It’s not perfect, because if the fender flexes into the tire it will still make a self-energizing brake. I would be okay with this on short fenders with lots of tire clearance, but wouldn’t count on it for fenders with a long front overhand and limited clearance.