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Sidi ST Air Vented Boots

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Q & A

Have a product related question about fit, features, or functionality? Ask it here.

If you have a question about availability or need immediate assistance, call 1-800-841-2960.

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Sidi ST Air Vented Boots

Shipping & Returns

Orders $100 and over qualify for our free shipping offer. See our full shipping policy for further shipping details.

Return any new, unused and unaltered item within 30 business days. Create a return label online for as little as $7.99. Please read our return policy.


  • Perforated Lorica outer for maximum airflow
  • Perforated Teflon treated nylon lining
  • Double stitched in all high stress areas
  • Padded achilles area
  • DuPont polymer toe shift pad
  • Composite inner sole
  • Dual compound sole
  • An elastic panel adjacent to the entry zipper allow a bind free zip and improved fit
  • Replaceable, shock absorbing heel cup
  • The ST can accommodate riders with up to an 15" calf diameter 12 1/2" above from the bottom of their heel
  • External ankle brace system
  • Exclusive cam-lock buckle system for easy entry and boot removal while still offering a perfect glove like fit
  • Bolt on replaceable, adjustable and aerodynamic nylon scuff pads on the toe
  • All bolt-on parts are replaceable
  • Closeable air vents on the foot outer
  • Removable arch support

Sidi Boots & Shoes

Metric Sizing USA Mens USA Womens
34 2 - 2-1/2
35 2-1/2 - 3 3-1/2 - 4
35.5 3 - 3-1/2 4 - 4-1/2
36 3-1/2 - 4 4-1/2 - 5
36.5 4 5
37 4 - 4-1/2 5 - 5-1/2
37.5 4-1/2 - 5 5-1/2 - 6
38 5 - 5-1/2 6 - 6-1/2
38.5 5-1/2 6-1/2 - 7
39 5-1/2 - 6 7
39.5 6 - 6-1/2 7 - 7-1/2
40 6-1/2 - 7 7-1/2 - 8
40.5 7 8 - 8-1/2
41 7 - 7-1/2 8-1/2 - 9
41.5 7-1/2 - 8 9
42 8 - 8-1/2 9 - 9-1/2
42.5 8-1/2 - 9 9-1/2 - 10
43 9 - 9-1/2 10 - 10-1/2
43.5 9-1/2 10-1/2
44 9-1/2 - 10 10-1/2 - 11
44.5 10 - 10-1/2 11 - 11-1/2
45 10-1/2 - 11 11-1/2 - 12
45.5 11 12
46 11 - 11-1/2 12 - 12-1/2
46.5 11-1/2 - 12 12-1/2 - 13
47 12 - 12-1/2 13 - 13-1/2
47.5 12-1/2 - 13 13-1/2 - 14
48 13 - 13-1/2 14 - 14-1/2
48.5 13-1/2 - 14
49 14 - 14-1/2
49.5 14-1/2 - 15
50 15 - 15-1/2
51 16 - 16-1/2
52 17 - 17-1/2

General Sizing information

If you are unsure about your size, compare your body measurements to the charts provided to determine the correct fit. These charts will give you a good idea of the size to order, but be sure to read special sizing information that may accompany an item description. Some merchandise dimensions may vary from the averages charted here.

Sidi Half Sizes

Sidi half sizes are 3 mm longer, with slightly increased toe box volume. Full sizes are 6 mm longer, with proportionally greater volume.

Sidi Boots & Shoes Width

  • Narrow sizes roughly correspond to a B to C width on the industry-standard Brannock sizing scale.
  • Standard-size shoes roughly correspond to a C to E width (averaging at a D width) on the Brannock sizing scale.
  • Mega sizes roughly correspond to a EE to EEE width* on the Brannock sizing scale.
* Occasionally a cyclist who does not have an exceptionally wide foot but who uses a high volume orthotic and/or has a very high instep will be more comfortable in a Mega shoe.

Mega & Narrow Sizes

Mega sizes are cut with more material throughout, and a larger-volume heelcup. Narrow sizes are cut with less material throughout, and a narrower, lower-volume heelcup. Sidi Mega shoes are constructed on a Mega last which is an additional 4mm wider across the ball of the foot - with more volume, a higher instep, and wider heel cup.

Sidi Women's Boots & Shoes

Sidi Women's shoes are built on an anatomically correct woman's specific last, following standard woman's tapered foot shape:
  • Tapered last mimics a woman's more dramatically tapered foot shape.*
  • The forefoot is proportionally wider but still lower volume.
  • The heel is narrower.
* A woman with a consistently wide or narrow foot (wide or narrow from the heel to the forefoot) may experience better fit in a Sidi Men's standard or Narrow width.

Fitting Sidi Shoes

Stand up when fastening the closures, start at the toes and work back toward the heel.

The Soft Instep Pad should be centered laterally, positioned so the letters "I" and "D" are over the high point of your foot.

Shoes will become more conforming as they warm up-a process that can take up to 30 minutes-so be patient. You'll want to periodically tighten straps and ratchets as this occurs, working front to back. Do not buy shoes that are too tight, thinking they'll get bigger over time. Sidi boots do NOT stretch!

When fit properly, edges of the material that fit over the shoe's tongue should be roughly parallel. The gap should NEVER narrow toward the ankle, the straps shouldn't bottom out, and there shouldn't be any significant puckering of material anywhere on the shoe. If any of these conditions apply try a smaller or narrower size.

Conversely, the uppers should never look like they're blowing apart. There should be approximately 1 cm of ratchet strap exposed between the Caliper Buckle and the Soft instep pad, and 1 cm of hook-side High Security Velcro showing. If there's more, try a larger or larger-volume size.

The Perfect Fit

The uppers are snug, with no bunching or puckering of material, with approximately 1 cm of ratchet strap remaining above the Caliper Buckle and 1 cm of scratchy-side Velcro exposed.

Fitting Tips

  • Try shoes on at the end of the day - your feet swell by at least a half-size as the day progresses, and as much as a full size on hot days. Stand up. Feet expand under pressure - standing up will give you a better sense of how your shoes will fit under pedaling pressure.
  • Bring the socks and orthotics you ride with - they have a tremendous influence on foot volume and fit.
  • Be patient! Non-leather cycling shoes do not stretch over time - how they fit in the store will be how they fit, period. However, as the shoes warm up from body heat the uppers will become more pliable and conforming. Give your shoes at least 10 minutes to heat up, and readjust the closures to accurately gauge how they'll feel mid-ride.
  • Ask for help centering the soft instep closure system over your instep or adjusting the heel retention device. (If your shoe has one.)
  • Foot measuring devices typically measure length and width only, and do not account for overall shape or foot volume. It's imperative that you try on shoes a half-size larger and smaller than your measured size, for confirmation of proper fit.
  • If possible try a half size up or down for comparison. If you're in-between sizes, think about how much your feet typically swell on a bike ride.
  • If you are not currently in a Sidi or you own a Sidi that is more than 5 years old you may not be the Sidi size you think you should be (this is especially true for women's shoes)
  • You may not realize you have a wide foot and may be wearing a regular width shoe that is too long in order to get the width right. In that case it is always better to switch to a wide model in the correct length.

How To Tell Size & Cut

Every Sidi shoe (except the Triathlon models) from the 2002 model year forward is stamped with the size and last. (Mega, Narrow or Women's shoe) The stamp is usually found on the tongue. For example, a Woman's model in size 40.5 would be stamped 40 ½ W, with the "W" indicating that it is a Women's model. (In older shoes this may be an L) If you had a Mega model, the stamp would be 40 ½ M, and if you had a Narrow model, the stamp would be 40 ½ S, with the "S" indicating that it is a Slim model. Ignore the size on the sole, which is the closest whole size, meaning that a 42, a 42.5 Women's and a 42 Mega would all have 42 stamped on the sole.


Model Name for Gear
ST Air
ST Air
Age & Gender

Item Numbers

Details Item Number Availability Store Pickup
Details:Black  6/39 Item #043-9407-39 Availability:Backorder: Ships in 7-12 daysStore Pickup:Unavailable
Details:Black  7/40 Item #043-9407-40 Availability:Backorder: Ships in 7-12 daysStore Pickup:Unavailable
Details:Black  7.5/41 Item #043-9407-41 Availability:Available: Ships in 3-5 daysStore Pickup:Unavailable
Details:Black  8.5/42 Item #043-9407-42 Availability:In stock: Ready to shipStore Pickup:Available
Details:Black  9.5/43 Item #043-9407-43 Availability:In stock: Ready to shipStore Pickup:Available
Details:Black  10/44 Item #043-9407-44 Availability:Available: Ships in 3-5 daysStore Pickup:Unavailable
Details:Black  11/45 Item #043-9407-45 Availability:In stock: Ready to shipStore Pickup:Available
Details:Black  11.5/46 Item #043-9407-46 Availability:In stock: Ready to shipStore Pickup:Available
Details:Black  12.5 U.S./48 Euro Item #043-9407-47 Availability:In stock: Ready to shipStore Pickup:Available
Details:Black  13/48 Item #043-9407-48 Availability:In stock: Ready to shipStore Pickup:Available

Motonation guarantees its footwear and products to be free from defect in materials or workmanship for one (1) year from the date of purchase for the original owner. A product recognized as defective by Motonation will be repaired or replaced at Motonation's discretion.

You must establish proof of purchase to obtain warranty service or replacement.

Motonation will only warranty products purchased from authorized SIDI dealers within the Unites States and its territories as well as Canada.

Certain authorized retailers do sell our products online, or through online auction sites, when in accordance with our regulations. In order for the warranty to apply to online purchases, an itemized receipt from that dealer must be included. If you are not sure if the seller is an authorized SIDI dealer, please contact the seller and request a physical address and account name. Whether this is an authorized SIDI dealer must be verified through our customer service at 619-401-4100. If the seller does not provide this information, then our warranty does not apply to this product.

This warranty is expressly in lieu of all other warranties. Any implied warranties of merchantability or fitness for a particular purpose are limited to the same duration as this express warranty.

Motonation is not liable for any incidental or consequential damages.

This warranty does not cover any representation or warranty made by a dealer beyond the provisions of this warranty.

If you are asked to return your boots or shoes for service, please remove any non SIDI items such as cleats or insoles. Any extra items will only be returned by request at the owner's expense.

The Motonation warranty does not cover:
Products without an invoice or sales receipt, which makes it impossible to establish the date and origin of sale, and also due to the risk of illegal or illicit provenance (e.g. stolen, sold in violation of the fiscal regulations, etc.).
Products that have reached the end of their normal life cycle.
Damage due to accidents, negligence, misuse, corrosion, incorrect installation, improperly performed repairs, use of incompatible spare parts or components, unaproved modifications or normal wear and tear.
Consumable materials including heel pads, mechanical enclosures, replacement treads, soles etc.
Any expenditure related to the transport of the product to and from an authorized Service Center.
Labor costs associated with removing the product from the shoe, and preparing it for shipment.
Compensation for inconvenience associated with not being able to use the product while being repaired or replaced.


This warranty gives you specific legal rights and you may also have other rights, which vary from state to state

WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov


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