Specialized Road Bike Size Guide: Find Your Fit by Height and Leg Length

Sizing a Specialized road bike

Specialized labels its road frames in centimetres and covers several very different fits: the racy Tarmac, now in both the SL8 and the newest SL9, the lightweight Aethos, the upright Roubaix SL8 with its Future Shock, and the aggressive alloy Allez Sprint. The SL8 and SL9 share the same geometry, so between those two you are choosing aero and weight, not fit. The Tarmac and Aethos sit racy, the Roubaix runs much taller, and the Allez Sprint sits taller and longer than a Tarmac at the same number, so riders replicating a Tarmac position on the Allez usually drop a size. Pick the model first, then the size.

Browse the range: all Specialized bikes at Bikeroom.

Please note. These sizes are a starting point, not a guarantee. The models sit quite differently at the same cm number, so compare reach and stack, not just the size label. A fit check settles any doubt.

Quick size finder

Find your height, cross check your inside leg, and read across to the cm size. The Tarmac SL8 and SL9 share identical sizing; the Roubaix reaches the widest range with a 44 and a 64.

The Allez Sprint sits taller and longer than a Tarmac at the same number, so if you are matching a Tarmac position rather than sizing from scratch, drop one size. Only the Roubaix offers the 44 and 64 extremes.

How to measure yourself

Height. Stand barefoot against a wall, heels together, and measure to the top of your head.

Leg length (inseam). Barefoot, feet about 15 cm apart, press a book up to the wall like a saddle and measure floor to spine.

Then use reach. Compare the reach below with a bike you like, since a Tarmac 54 and a Roubaix 54 put you in very different positions.

Tarmac SL8 (race all rounder)

The Tarmac SL8 is the race all rounder, the lowest and most aggressive front end of the range, and it runs true to size. Between sizes, most riders size down for the stiffer, lighter smaller frame with more room to raise the bars. Available in 7 sizes: 44 to 61.

Tarmac SL9 (race all rounder, newest)

The Tarmac SL9 is the newest Tarmac and the direct successor to the SL8, and for sizing it is refreshingly simple: it shares the exact same stack and reach as the SL8 at every size, so order the same size you would ride in the SL8. The changes over the SL8 are almost entirely aerodynamic rather than fit related, with only the 54 tweaked slightly to reduce toe overlap. Available in 7 sizes: 44 to 61.

Same aggressive race position as the SL8. If you are choosing between the two, size identically; the SL9 is the faster, more aero frame, not a different fit.

Aethos (lightweight)

The Aethos uses the same numeric sizing as the Tarmac but sits a touch taller and more relaxed at the front, a climb focused, comfortable ride without aero pretension. Keep your Tarmac size and expect slightly higher bars. Available in 6 sizes: 49 to 61.

Roubaix SL8 (endurance)

The Roubaix SL8 is the endurance bike, with a much taller stack and the Future Shock cushioning above the head tube. It sits you up and cannot be slammed lower than stock, so take your usual road number; comfort riders do not need to size down. Available in 8 sizes: 44 to 64.

The Future Shock sits above the head tube, so the effective front end is higher than the stack figure and cannot be lowered. Several owners swap the tall Hover bar and the stock saddle to taste.

Allez Sprint (alloy race)

The Allez Sprint is the aggressive alloy crit racer, but at any given number it sits about 20 mm taller and 12 mm longer than a Tarmac. So riders coming off a Tarmac usually drop one size to keep the same drop. Available in 6 sizes: 49 to 61.

What Specialized riders find

Across the range the guidance when between two sizes is to size down for a racier fit and smaller frame stiffness, or up only if you have long legs and a short torso or want comfort. The Tarmac SL8 runs true to size with the lowest front end, and the newest SL9 shares its geometry exactly, so it is not a different fit, just a faster, more aero frame. The Aethos takes the same number as your Tarmac but sits higher and more relaxed. The Roubaix sits very tall, its Future Shock cannot be slammed, and owners often swap the upright Hover bar and the stock saddle. The Allez Sprint is taller and longer than a Tarmac at the same label, so Tarmac owners typically drop a size, going down for crit racing and up for training heavy use.

Between two sizes?

Go smaller for a sharper, racier fit or larger for comfort and stability. Pick the model for its fit character first, then the size by height and reach. Send us your height, inside leg and current bike's reach and we will confirm.

Shop Specialized road

• All Specialized bikes including the Tarmac SL8 and SL9, Aethos, Roubaix SL8 and Allez Sprint

Race, light or endurance? Ask our concierge

The Specialized road bikes fit very differently, so the model choice matters. Share your height, inside leg and riding style and our concierge team will recommend the model and size. Talk to our concierge.

These sizes are guidance, not a fitting guarantee. Stack and reach are official Specialized frame data; the Tarmac SL9 shares the SL8's geometry at every size. Rider height ranges follow Specialized's chart; the Allez Sprint sits taller and longer than a Tarmac at the same number. Always confirm against the specific bike you are buying.