Prototipo Works: A better bidon cage bolt?

by Dave Rome


Ever had a bolt head that’s just a whisker too tall for your bidon to smoothly slide into its cage? Maybe you’ve rounded out a low profile button-head bolt? Or perhaps you’ve looked for a more minimalist option to replace the unused bolts across your bike?

It would seem the people behind Melbourne-based company Prototipo have experienced all of this and more. This new company is specialising in the smallest of small parts, and aiming to do those parts better.

The products in Prototipo’s range are so tiny that they’re shipped in recycled paper receipt rolls (think toilet paper roll, but for paper receipts). This includes ultra-low profile bidon cage bolts, almost head-less bidon cage bolts, aluminium valve caps (yeah …) and a high-quality stainless-steel Presta-to-Schraeder valve adapter.

A better bolt

With a choice between stainless steel or lighter 6061 aluminium, and head profiles lower than anything else out there, Prototipo’s bolts are the headline act for the new start-up.

“Currently all our parts are precision CNC machined, [a process that] produces extremely accurate, consistent and repeatable results,” says the owner of Prototipo, Lindsay Thebus. “All our parts are CNC-machined first before gaining extra strength and abrasion resistance via titanium PVD coating or anodising.”

Using a CNC process isn’t standard practice for bolt production, as Thebus explains.

“The rolling process produces the majority of the world’s externally threaded fasteners,” Thebus says. “This mass production method is economical in scale but limited to standard head profiles and not very flexible or financially viable for unique, small, low volume bespoke production runs. We tried post-machining premium specification fasteners with rolled threads but ultimately needed more control in design features like stress risers and hex/torx depth whilst maintaining strength in our low-profile heads.”

In using Prototipo’s bolts it became clear that they’ve managed to combine an impressively low head height without feeling sketchy to install. In fact, the fit between the tool and bolt is rock solid and a noticeable improvement over the generic lightweight button-head bolts often provided on bikes.

Prototipo’s Original low profile bolt is pictured on the far right. To its left sit Specialized’s alloy cage bolts which are impressively good, but they’re still noticeably taller and with less tool engagement than the niche offering.

“It’s a fun challenge to combine a low profile head, especially an ultra low profile head with functional hex/torx depth and competitive strength in such a small area,” Thebus said. “Where it matters most we try to keep as much material in specific places and redirect stress via stress risers, fillets or add strength simply through thickness. We’ve tried to keep our tolerances as high as possible to protect all users and toolsets of all levels from entry-level to professional.”

All of Prototipo’s bolts have a tapered end which makes the bolt easier to locate into place. It’s a design element that makes the initial threading a breeze and shaves off a little weight in the process. However, it reduces the effective bolt length by a few millimetres and so you should factor this in if you run spacers or accessories beneath your cages.

Prototipo’s Under Flush bolts fill unused bidon cage mounts.

While Prototipo’s original and low-profile bolts work well with or without cages in place, the “Under Flush” bolts are a unique solution to cleaning up the aesthetic of a frame when bolts aren’t needed. I’ve currently got a gravel bike on review with over 15 bidon cage/accessory bolts across it, and the Prototipo Under Flush bolts would be something I’d look to run on some of the unused mount areas. Similarly, they’d be great for cyclocross racers looking to get a more comfortable carry off the bike.

The Under Flush bolts do beg a question though: What’s wrong with a cheap plastic cap that fills the space of the bolt? Well, not much, but the Under Flush bolts do arguably look nicer and will never be misplaced.

Weight-wise the minimalist-looking Prototipo bolts are competitively light, but you’ll need some fancy scales to measure the difference. For example, regular steel button-head bidon cage bolts weigh 4.5 g for the pair, while the comparable Prototipo bolts are 3.6 g. While a pair of regular alloy bidon cage bolts are 1.8 g, with the Prototipo Original’s sitting at 1.3 g. These are all pretty insignificant numbers, however, the Prototipo do feel stronger and less likely to round out.

As with most unique, well-made, and clever products in cycling, these don’t come cheap. Currently, the bolts are sold in pairs and sell for between AU$9.95-AU$12.95. Most people will need to spend $20-$26 to replace their existing bidon cage bolts. Add in a likely postage fee and that’s no small expense for such a small part.

For those baulking at that price but who still need something almost as low profile as these bolts, then try some regular disc brake rotor bolts. These use Torx T25 heads which allow a low profile and decent tool engagement. That said, even the original bolts from Prototipo are noticeably lower in profile again.

All Prototipo bolts are sold as two pieces – I’d personally prefer they were sold as double that.

Currently, all the bolts are only available in a single M5 x 0.8 mm thread to suit the vast majority of bikes on the market today.

Valve caps?!

Price aside, I understand the market need for nicer bolts. However, I simply don’t understand the need for Prototipo’s alloy Presta valve caps. Sure they’re stronger (and marginally heavier by 0.4 g for the pair) than plastic ones, but why even use valve caps to begin with? To me it just feels like a gimmicky product that detracts from the good work the company is doing with its bolts.

Valve caps and adapters. They’re undeniably high quality, but the former is questionably useful.

Thebus sees it differently. “We found there was a medium-large group of people who felt the protective qualities, ingress prevention and barrel protection warranted the ongoing use of valve caps,” Thebus said. “Within that sample of people there was a small group who wanted something better and stronger than the simple standard plastic offerings.

“It’s a risk to produce such a small niche product but we’ve been getting great feedback that it’s filling the void and our favourite is seeing them used in builds where every component has been thoroughly researched and they add the finishing touch!”

Speaking of valves, Prototipo offers a quality CNC’d Stainless steel Presta-Schraeder valve adapter. Such adapters are a useful item to keep in a saddlebag in case you want to fill your tyres at a car service station. Prototipo’s is the nicest one I’ve seen yet.

In short, Prototipo has seemingly taken something as mundane as bidon cage bolts and added tangible differences. However, the small company will want to get them onto the shelves of bike stores and large online retailers as the bolts are already a pricey upgrade before having to pay for dedicated postage.

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