S5
vsOstro VAM
Two flagship aero bikes, two very different personalities.
The Cervélo S5 is a wind-tunnel-honed speed weapon. The Factor Ostro VAM is the lighter, more refined boutique alternative.
S5
- Verified wind-tunnel king — Cycling News measured the new S5 as the fastest bike they've ever tested at 40 km/h.
- Locked-in high-speed stability — reviewers consistently report 2–3 km/h faster cruising on familiar roads with no extra effort.
- Generous tire clearance for an aero bike — 34 mm claimed, with stock 29 mm Vittoria Corsa Pros on wide Reserve rims.
- BBright press-fit bottom bracket is a recurring maintenance gripe — particularly with the Di2 battery housed inside it.
- Lacks snap below 30 km/h and demands rider input to come alive.
Ostro VAM
- Lighter frame and wheels — 820 g painted frame and a 1,270 g claimed Black Inc 48|58 wheelset, ~200 g lighter than the S5's Reserves.
- CeramicSpeed bearings throughout — SLT headset and T47 threaded bottom bracket come stock; most rivals charge extra.
- Free factory fit customization — bar width, stem length, crank length, and saddle setback chosen at no upcharge at order time.
- Tighter 32 mm tire clearance than the S5's claimed 34 mm.
- No power meter on the stock Dura-Ace build — must be specced separately.
Editor’s analysis
Both bikes claim WorldTour pedigree and aero supremacy — but one is engineered to dominate flat-out, and the other to disappear underneath you on every kind of road.
On paper, the Cervélo S5 and Factor Ostro VAM occupy the same shelf: top-shelf aero road bikes with deep-section integrated cockpits, premium SRAM and Shimano electronic builds, and price tags that start at the high four-figure mark. Both have raced and won at the WorldTour level — Visma-Lease a Bike on the S5, Israel-Premier Tech on the Ostro. But ride them back to back and the design priorities diverge sharply.
The Cervélo S5 is the purer aero specialist. Cervélo's own numbers claim 6.3 watts saved over the previous generation at race speed, and Cycling News's wind-tunnel test pegged the new S5 as the fastest bike they've ever measured at 40 km/h with a rider on board. It's also the heavier of the two — a Granfondo-tested size 56 came in at 7.44 kg — and almost every reviewer mentions the same thing: it lacks snap below 30 km/h and only truly comes alive when you push the wattage up. Cervélo's BBright press-fit bottom bracket is a known maintenance pain point, and the 1x SRAM Red XPLR option on the flagship is polarizing.
The Factor Ostro VAM is the lighter, more well-rounded machine. Factor claims an 820 g painted frame in size 54 and a 7-watt drag reduction at 48 km/h over the V1 — close enough to the S5 in the wind tunnel that Cycling News ranked it among the fastest road bikes they've tested. Component spec is where it pulls ahead: CeramicSpeed bearings in both the T47 threaded bottom bracket and SLT headset come standard, plus the 1,270 g claimed Black Inc 48|58 wheelset. Velo's reviewer described it as 'the bike that punches above its weight on the climbs' while still gliding with the best aero bikes on flat roads.
The honest summary: the S5 is sharper at speed and a more uncompromising aero tool — the bike to buy if your local roads are flat and your race calendar is criteriums and breakaways. The Ostro VAM is the more versatile all-rounder, and the more polished ownership experience — CeramicSpeed bearings, threaded bottom bracket, factory-spec bar and stem options, and a frame light enough to climb with dedicated lightweight bikes. Cervélo wins the wind tunnel; Factor wins almost everything else.
Where the builds differ.
Comparing our editor's-pick builds side-by-side. Winners highlighted row-by-row — lower price and weight, and the better-spec component, each mark a point.
Build variants & pricing
Both platforms live in the $10k+ tier — neither offers a budget entry point. Editor's picks are tier-matched at SRAM Force AXS with a power meter on each side.
Prices are current US MSRP. The S5 ranges $10,100–$14,500 across five builds; the Ostro VAM ranges $10,399–$12,599 across four. Cervélo's flagship is the polarizing 1x SRAM Red XPLR; Factor's tops out at a 2x SRAM Red AXS with power meter.
How they fit, how they steer.
Both at size 54 — the fit-picked size for a 5'8" rider on each bike. Stack and reach are identical at 542 mm / 384 mm. The S5 runs a steeper 73° head tube with 55.6 mm trail; the Ostro sits half a degree slacker at 72.5° with 58 mm trail and a 10 mm longer wheelbase — Cervélo dives into corners, Factor stays planted.
Which size should I buy?
Size recommendations based on stack, reach, and effective top tube. Both ranges overlap closely in the middle; the Ostro VAM extends a touch smaller (45 cm) than the S5 (48).
→These are starting points. Flexibility, riding style, and preferred position all shift the answer — if you’re between sizes, a professional fit beats a chart.
What the magazines said.
Published reviews from trusted cycling outlets. Click through for the full write-up.
Which one should you buy?
If you race flat crits and want pure measurable aero, get the Cervélo S5. If you want one bike to climb, descend, and own for a decade, get the Factor Ostro VAM.
S5
If your roads are flat or rolling, you race above 35 km/h, and you measure success in wind-tunnel watts, the S5 is the sharper tool. It's the verified fastest bike in the segment, and its locked-in high-speed stability rewards heavy-handed wattage like nothing else.
Ostro VAM
If you want a single bike that climbs with lightweight machines, holds aero pace on flats, and ships with the best bearings, threaded BB, and factory fit options in the category, the Ostro VAM is the more refined long-term ownership story. Slightly slower in the tunnel — measurably better everywhere else.
Questions buyers actually ask.
Short answers to the things we get emailed about most often.
01Which is faster in the wind tunnel?
The Cervélo S5, by a small but measurable margin. Cycling News's wind-tunnel test ranked the new S5 as the fastest bike they've ever measured at 40 km/h with a rider on board, saving roughly 27.6 watts versus their baseline. The Factor Ostro VAM placed in the same top tier — Factor claims a 7-watt saving at 48 km/h over the V1, and Cycling News rated it 'one of the fastest' alongside the Cervélo and Specialized Tarmac.
The gap is real but small enough that frame, wheel, and rider-position choices probably matter more than the platform itself for most riders.
02Which is lighter?
The Factor Ostro VAM, noticeably. Factor claims an 820 g painted frame in size 54, and complete Dura-Ace builds have been weighed at 6.7 kg. The Cervélo S5 is the heavier of the two — Granfondo measured a size 56 at 7.44 kg.
That's roughly 700 g of system weight on a like-for-like build. On a 30-minute climb, that translates to about 10–15 seconds for a 70 kg rider — small in absolute terms, but the Factor also feels lighter underneath you out of the saddle.
03What's the maximum tire clearance?
Cervélo S5: 34 mm claimed, though one Velo reviewer was 'sceptical' about that number after seeing how tight 32 mm already looked. Stock builds ship with 29 mm Vittoria Corsa Pro TLR G2.0 tires.
Factor Ostro VAM: 32 mm claimed. Stock builds ship with Goodyear Eagle F1 tires (which several reviewers recommend swapping for tubeless).
Neither is a gravel bike — for chip-seal or rougher, look at an endurance frame instead.
04How serviceable are the bottom brackets?
This is the single biggest practical difference between the two.
The Cervélo S5 uses a proprietary BBright press-fit bottom bracket. Multiple reviewers call it 'difficult' and 'a hassle,' especially because it houses the Di2 battery — battery service is awkward, and most home mechanics will end up at a shop.
The Factor Ostro VAM uses a T47 threaded bottom bracket with CeramicSpeed bearings as standard. T47 is the modern consensus standard — easy to service, no creak, no proprietary tooling. For long-term ownership, this is a meaningful win for the Factor.
05What about the integrated cockpits?
Both bikes ship with proprietary one-piece bar-stem units that limit aftermarket adjustability.
The Cervélo HB19 has a clean one-piece design with backward compatibility to previous S5 generations. Cervélo offers a 60-day no-cost swap if you order the wrong size.
The Black Inc Integrated Aero Barstem on the Factor is similar in concept, but Factor goes further on initial fit: you can spec bar width, stem length, crank length, and saddle setback at no extra cost when you order. That's the customization story Factor is known for and one of the clearest value-adds in the category.
06Which has better wheels?
Different philosophies.
The Cervélo S5 ships with Reserve 57|64 Turbulent Aero wheels — co-developed with the frame, with steel spokes (Cervélo specifically chose steel over carbon for serviceability and global support) and DT Swiss 180 hubs on top builds, 240s on Ultegra/Force.
The Factor Ostro VAM ships with Black Inc 48|58 wheels — claimed 1,270 g, roughly 200 g lighter than the Reserves, with carbon spokes. They're stiffer and faster up to speed, but one Velo reviewer flagged that carbon spokes are harder for shops to work on and can fail more catastrophically on impact.
Lighter and racier on the Factor; more serviceable and tougher on the Cervélo.
07Are there budget builds on either?
No. Both platforms start at roughly $10k and go up from there. The S5 starts at $10,100 (Ultegra Di2) and tops out at $14,500 (Red AXS or Red XPLR 1x). The Ostro VAM starts at $10,399 (Ultegra Di2) and tops out at $12,599 (Red AXS with power meter).
If you want a true mid-tier carbon aero bike under $6k, neither is the right shopping list — look at the Specialized Tarmac SL8 Comp or a Canyon Aeroad CFR build.
08Which holds resale value better?
Both are boutique-leaning brands with smaller production runs than mass-market competitors, which generally helps resale. Factor in particular runs smaller volumes and has a more exclusive perception, which tends to slow depreciation on the used market.
Cervélo benefits from constant WorldTour visibility (Visma-Lease a Bike, Vingegaard, Tour wins) — the brand recognition keeps demand strong even as builds age out. Both will lose the most value in the first year and depreciate more slowly after that. Buying a one-season-old flagship second-hand is one of the better entry points to either platform.
Similar bikes
If your priorities don’t map cleanly onto either of these, one of these adjacent bikes probably fits better.
Tarmac
The benchmark all-rounder — lighter than the S5, broader build range than the Ostro VAM, and the bike most reviewers default to for cross-platform comparison. The safer, do-everything pick if you only want one road bike.
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Aeroad
Often cited as the only bike that matches the S5's pure speed sensation at a meaningfully lower price. The direct-to-consumer catch is no local dealer and no demos — best if you already know your fit.
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Madone
Trek's aero-race flagship with the IsoFlow seat-tube cutout, claiming S5-rivalling drag numbers but with a built-in compliance feature that softens longer days. The comfort-leaning pick in this radical aero bracket.
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