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Mosaic RT-1 titanium road bike frame



Fast, responsive and keen titanium frame that'll make you rethink your frame material of choice.

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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Mosaic's RT-1 proves that titanium still deserves to be taken serious as a performance frame material, and will put a high-speed grin on your face.

Mosaic Bespoke Bicycles hail from Boulder in Colorado and were started by Aaron Barcheck who used to work for Dean Titanium Bicycles where over his seven year stint there rose to become head builder. You might not have heard of Dean but they had quite the select following in mountainbike circles back in the day when titanium was the exotic frame material of choice before carbon waded in. With over 500 titanium and steel frames under his torch Aaron left Dean to start Mosaic Cycles in 2009.


Mosaic will knock you up a frame in titanium or steel, and you can ask for a track, road, cyclo-cross, gravel racer or mountainbike out of your favoured tubes. The RT-1 is Mosaic's top-of-the line titanium frame, made from custom butted size specific 3Al/2.5V titanium tubes to your custom geometry. The RT-1 frame on its own costs £2,550, but if that's too much for you the straight gauge titanium tubed RT-2 is £300 less, and if that's still too rich for your blood you can get a True Temper S3 steel road frame for £1,400.

This RT-1 frame has been built up by Mosaic importer Prestige Cycles with the kind of bling kit that a £2.5K frameset demands, which brings the price of the whole bike up to a tidy £7,590. As you can have the frameset garlanded as posh or as practical as you like that kind of outlay isn't written in stone and there are obvious ways of cutting costs without insulting the breeding of the frame. Prestige could for example offer an 11 speed Athena, Mavic Cosmic Elite, Easton bar and Prologo saddle combo that would bring the price of a whole bike down to a meagre £4,999. With that in mind there's not much point in focusing too much on the parts; it's the frame that's the important thing here.

Prestige have plumped for the full Campagnolo Record 11 mechanical groupset, certainly no complaints there. It's either clunky or positive in its shifting depending on your point of view, and in light of modern electronic developments could almost be seen as archaic, but it still works perfectly well. If you did want to run any kind of electronic groupset Mosaic will happily make you a frame with internal cable routing to keep the spaghetti all tidied away.

The frame is plugged with a light but firm ENVE full carbon tapered fork that blends well with the oversized titanium tubes. The Reynolds 72 Aero clincher wheels definitely highlight the frame's racing potential being both fast and stiff, as well as producing that all important resonant rumbling noise. To be honest they're probably not the wheels to spec on this bike for everyday use, not least for the fact that they can get a bit of a handful in a gusty wind, some Reynolds 32 clinchers might complement the Mosaic both performance wise and visually if you wanted something of a similar brand and outlay. They're shod with perennial favourites Continental GP 4000 tyres.

Thomson bars, stem and seatpost put all the contact points in the right place and the post is topped off with a Fizik Kurve saddle. While all that equipment is a wonderful example of bicycle finery it's not necessarily the lightest all round and brings the bike weight to 7.57kg (16lbs 11oz). That's more than respectable in itself for a non-carbon machine, but something that could be chipped away at with some parts swapping, if that's your thing.

As it's a custom frame what you see here is just the one example of what Mosaic can do for you. Internal brake and shift cable routing? No problem. You can have disc mounts, the choice of a dashing seat mast or normal seat post, even S and S Couplings if you travel a lot. There's a custom paint option too if you like your bike to match your socks. Quite importantly and to make sure your Mosaic fits you perfectly Prestige Cycles offer a BikeFit service, a two-hour session working towards getting a personalized fit to optimise your power, efficiency and comfort so you can get the most out of your new shiny, well, not shiny, bicycle.

Titanium was the go-to material for top-end bikes a few years ago where its comparative light weight, potential longevity and oft lauded springy ride made it the stuff of many a small boy's dreams. Then carbon came along and knocked it off its perch, but there are a lot of frame builders out there who think it's still a viable frame material. Its inherent qualities make for a comfortable bike frame; it's durable, resisting the dents and knocks of day to day living better than some frame materials; and in a crash is likely to come off less battered than others. It's easy to cut the tubes to custom sizes, and can still be built up competitively light if needed, It's corrosion-resistant so it doesn't need to have a protective layer of paint over it, and it scrubs up well so will look good for years to come. All qualities that some riders still look for in their bike frame.

The quality of the work and finishing of the Mosaic is, without any hint of exaggeration, exquisite. Free from any paint or stickers there's nowhere for any defects or poor workmanship to hide which is lucky because there aren't any; every fish-scale weld is neat and perfect and the tubes are faultlessly finished, there's real craft oozing through the RT-1 frame.

In these days of performance bikes being swoopy and curvy with every frame part squashed and bent and swagged and manipulated to eke every inch of efficiency out of the bike it's almost refreshing to come across a frame that's made up of straight, round tubes. There's very little in the way of visible tube treatment although the RT-1 is butted internally, the top and down tubes are somewhat larger than you might be used to in a titanium frame while the oversized 44mm headtube flares out ever so slightly and very elegantly at the ends to accommodate the Chris King headset.

That top-tube is slightly sloping, with the rear brake cable internally routed through it, while the gear cables are directed more traditionally externally via the down tube through minimalist threaded cable stops. Emerging from the oversized bottom-bracket shell the chainstays are really quite fat while those tapered seatstays are contrastingly skinny, seemingly to give a little bit of compliance to the rear-end, and are dead straight with no curves of wiggles in them as is the usual trend. They meet up at deep-cowled dropouts to offer both a full weld area to the tubes and increase stiffness to the rear end.

Although there is the option for a custom paint job this frame doesn't need anything as common as colour hiding its panache. All the graphics, what there are of them, are reverse polished out of a bead-blasted frame which as a look resets the stylish scale a little. The down-tube graphic isn't the usual repeated insignia down each side, it's simply a large single shiny 'Mosaic' logo running along the top of the tube, with the only other adornments being an 'R-Series' graphic on the seat tube and top of the seat-stay. The headbadge is an intricately and elegantly shaped piece of stainless steel.

Before you even swing your leg over it the Mosaic is a thing that elicits quiet joy. If you like your bike to look like a cereal box you're probably best looking elsewhere, although with the custom paint option you could go as emetic as you like. Which would be a shame. I'd happily pay a large percentage of the frame's price for these understated looks alone.

Enough of the artisan and the aesthetics, how does the Mosaic perform? Not like a titanium bike. Well maybe not like you might expect a titanium bike to ride, in a good way. The inherent elastic qualities of the metal can be exploited when fashioned into a bicycle frame to produce a soft and comfortable ride, useful in damping out road vibration and it's an oft repeated axiom that titanium makes for a compliant, relaxing ride. From the first pedal stroke the Mosaic throws that pub wisdom straight out the lounge bar window.

The mark of a good frame builder is whether they can effectively manipulate their chosen material to create the frame characteristics they want. Using titanium Mosaic could have easily gone down the stereotypical comfortable and forgiving road, as it were, making a bicycle that would be a joy to ride all day, but with intelligent use of oversize tubing in the RT-1 they've chosen to produce a stiff and fast bike that's a joy to ride. All of the tubes on the RT-1 bar the seatstays are subtly oversized making for a pleasingly stiff structure, not so rigid that it makes your fillings dance, but if you're still of the belief that titanium bikes are little bit noodly when you smash the power down then you'll have to have a rethink.

The ride is best described as pleasingly taut. The Mosaic just loves to pounce forward, there's a real Tigger spring in its step. An indication of the true character of this bike would be it's reluctance to be shifted out of the big ring, and that's a real 53 tooth big ring, not just the bigger ring of the two. Sit up and smell the flowers rides were attempted, and they certainly are possible for a while but the RT-1 would gently nudge the speed up in imperceptible increments and it was an inevitability that at some point the ride would be going full gas again. It wants to go fast, all of the time, while giggling. Social rides were awkward.

Maybe it was those wheels helping chivvy things along but they can't account for everything, most likely it was the Mosaic's keen stance and eager pedigree nicely proving that titanium can still be a feasible performance frame material among the carbon heavy peloton. You could easily race the RT-1 and not be able to use it as an excuse. Those fat chainstays certainly direct your power through to the rear wheel and combined with the oversize bottom-bracket and voluminous down-tube mean there's no flop or wobble to the frame and it eagerly jumps forward with every thigh pump.

Thankfully all of that oversizeness doesn't cancel out every last nuance of titanium's famed damping qualities. Even with the Reynolds 72 deep section wheels bolted in the ride wasn't uncomfortable, but it would be more suited to a rider who likes to feel the road underneath them. That's useful because if you're as eager to ride at speed on the raggedy edge as the RT-1 itself, then constant tarmac feedback is a necessary sensation. If you want day-long comfort then this might not be the particular bike for you, although a chat with Mosaic could see them conjure up a frame with more polite characteristics in your future.

That's not to say it's a harsh uncompromising machine. Those pencil slim seatstays do a good job of isolating the rider from the harshest edges of road buzz, because the deep section rims and a 30.9 alloy seatpost don't really do much to add any comfort. And there's enough damping in the rear triangle that if you get ugly smashing the pedals around the back end doesn't jump about like a frog in a frying pan; jagged-edged technique is softened out a bit by the time it gets to the dropouts.

Steering is as direct as the back end, The oversized down and top tubes and 44mm headtube locking in a full carbon ENVE tapered steerer fork ensure there's no yaw or vagueness to the front end and it goes where you point it. Despite its eagerness to be Spitfire fast all the time the steering on the RT-1 isn't a nervous whippet handful so it's not going to spit you off on the first corner or tire you out after 20 miles. Its handling isn't tug-boat lazy either, but a happy neutral.

Of course, as this is a bespoke frame you can get Mosaic to blend those butted titanium tubes together to behave pretty much in whichever way you want. They have a custom 4-stage process that transforms a rider's dreams and needs into a suitable bicycle frame. In this particular version of the RT-1, Mosaic have built a fast, responsive, involving and fun bike with just enough sting removed from the tail to make it comfortable. The level of construction and handling here is a reminder that titanium still has a place in the highest echelon of performance frame materials.


Fast, responsive and keen titanium frame that'll make you rethink your frame material of choice.

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Make and model: Mosaic RT-1 Frameset

Size tested: 56cm

About the bike

State the frame and fork material and method of construction. List the components used to build up the bike.

Frame - Mosaic RT-1, custom butted 3/2.5 titanium

Fork - Enve 2.0 road, full carbon, tapered steerer

Wheels - Reynolds 72 Aero clincher

Chainset - Campagnolo Record 11 Ultra-Torque, 53/39

Shifters - Campagnolo Record 11

Rear Derailleur - Campagnolo Record 11

Front Derailleur - Campagnolo Record 11

Cassette – Campagnolo Record 11, 11-25

Chain – Record 11 speed

Brakes - Campagnolo Record Skeleton

Stem – Thomson Elite X2

Handlebars - Thomson Carbon Road

Bar Tape – Fizik

Seatpost - Thomson Elite 30.9

Saddle - Fizik Kurve

Tyres - Continental GP 4000

Bottom Bracket – Campagnolo EPS Ultra-Torque OS-Fit Integrated Cups

Chain – Record 11 speed

Headset - Chris King

Seatpost Collar - Thomson

Tell us what the bike is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about the bike?

The RT-1 represents the best of what Mosaic has to offer with its Road lineup. Performance add-ons blended with a lightweight double-butted titanium tubeset make a bike equipped for anything.

It's a custom built titanium bike, you decide what you want out of your bike frame and Mosaic will make it so.

Frame and fork

Overall rating for frame and fork

Tell us about the build quality and finish of the frame and fork?

The Mosaic is exquisitely made; the immaculate welds, polished graphics and stainless headbadge mark it out as a frame of outstanding beauty and quality. The ENVE fork is just as subtly elegant and suits it well.

Tell us about the materials used in the frame and fork?

Custom butted 3Al/2.5V titanium frame, full carbon tapered fork.

Tell us about the geometry of the frame and fork?

As a custom bike the geometry can be fiddled with to do whatever you want it to do. As it's laid out here, with 73° seat and head angles and 560mm top and seat tubes it's nippy.

How was the bike in terms of height and reach? How did it compare to other bikes of the same stated size?

As Mosaic are a bespoke frame builder they'll build the RT-1 to fit you perfectly.

Riding the bike

Was the bike comfortable to ride? Tell us how you felt about the ride quality.

It was purposefully direct, but with a comfortable edge factored in.

Did the bike feel stiff in the right places? Did any part of the bike feel too stiff or too flexible?

It was stiff enough to punch forward when required, but those slim seatstays added a bit of comfy flex.

How did the bike transfer power? Did it feel efficient?

Yes, the Mosaic just loved squirting forwards.

Was there any toe-clip overlap with the front wheel? If so, was it a problem?


How would you describe the steering? Was it lively, neutral or unresponsive? Chirpily neutral.

Tell us some more about the handling. How did the bike feel overall? Did it do particular things well or badly?

It did going fast very well.

Which components had the most effect (good or bad) on the bike's comfort? would you recommend any changes?

Swapping the wheels would probably help with comfort here, but hey, your custom bike, your choice of bits.

Which components had the most effect (good or bad) on the bike's stiffness? would you recommend any changes?

The Reynolds wheels certain contributed, as did the ENVE forks, I'd keep the forks and swap the wheels.

Which components had the most effect (good or bad) on the bike's efficiency? would you recommend any changes?

The build on this Mosaic was all about going forwards fast, no compact chainset, aggressive position, slippery wheels. You may want to change some or all of this for your own bike.

Rate the bike for efficiency of power transfer:
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Rate the bike for sprinting:
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Rate the bike for cornering on descents:
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The drivetrain

Rate the drivetrain for performance:

It's good, but a bit clunky in these slick shifting and electronic days

Rate the drivetrain for durability:
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Tell us some more about the drivetrain. Anything you particularly did or didn't like? Any components which didn't work well together?

This Mosaic came with Campagnolo, you'll either love it or hate it. I like it. But your Mosaic can come with whatever you want to slap on it.

Wheels and tyres

Rate the wheels and tyres for performance:

The Reynolds wheels are fast.

Rate the wheels and tyres for durability:

You probably wouldn't put these on your Winter bike if you wanted them to last.

Rate the wheels and tyres for weight:
Rate the wheels and tyres for comfort:

Not the most compliant wheel package.

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Tell us some more about the wheels and tyres.Did they work well in the conditions you encountered? Would you change the wheels or tyres? If so, what for?

These wouldn't be my first choice of wheel, they're very race orientated, which thankfully suited the bike quite well, but something more prosaic on the Mosaic for day-to-day use might be a better choice.


Rate the controls for performance:

All top shelf stuff here to match the frame, no complaints.

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Rate the controls for weight:

All light enough stuff, but nothing nerdy svelte here.

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Tell us some more about the controls. Any particularly good or bad components? How would the controls work for larger or smaller riders?

Again, the Mosaic will be your build but I got on with the Fizik saddle and Thomson components although a shallower drop bar would suit me better.

Your summary

Did you enjoy riding the bike? Hell yes!

Would you consider buying the bike? Not specifically in this configuration, but a custom Mosaic frame is now on that list of dream bikes.

Would you recommend the bike to a friend? Yes.

Rate the bike overall for performance:
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Overall rating: 9/10

About the tester

Age: 42  Height: 180cm  Weight: 73kg

I usually ride: It varies as to the season.  My best bike is: The one I\'m on at the time

I've been riding for: Over 20 years  I ride: Most days  I would class myself as: Experienced

I regularly do the following types of riding: road racing, cyclo cross, general fitness riding, fixed/singlespeed, mtb, Fun


Jo Burt has spent the majority of his life riding bikes, drawing bikes and writing about bikes. When he's not scribbling pictures for the whole gamut of cycling media he writes words about them for and when he's not doing either of those he's pedaling. Then in whatever spare minutes there are in between he's agonizing over getting his socks, cycling cap and bar-tape to coordinate just so. And is quietly disappointed that yours don't He rides and races road bikes a bit, cyclo-cross bikes a lot and mountainbikes a fair bit too. Would rather be up a mountain.

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