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Rockrider ST500, Mountain Bike Undershorts, Men's
With its thick pad and breathable fabric, the ergonomic foam pad on these men's undershorts absorbs vibrations and prevents chafing and irritation.
Free returns
Free shipping over $35
Free pickup
San Francisco, 735 Market St. Options
Select an available color and size to see options.
Product Features

Sitting Comfort
Ride comfortably for up to 4 hours with the ergonomic foam pad (13 mm).
Moisture Management
Actively wicks away perspiration to the outer surface for quick drying
Stability
Fitted cut without compression, very elasticated waistband
Stretch
Spandex in the fabric to guarantee ease of movement.
Compatibility
You just need one: these undershorts are compatible with our men's MTB shorts
Lightweight
6 oz in size L.
Eco-Design
Opaque part: 87% recycled polyester Mesh part: 86% recycled polyester
Product Customer Reviews

Sizing is a bit weird. I went for a size larger than I normally have and that seems to fit ok. They are very comfortable though and have good padding. Cheap too, what’s not to love except the bonkers sizing.
I recently bought 2 pairs of these to replace my old MT500 undershorts that are excellent, especially for the cost, and fit extremely well, but worn out now after years of use. Likewise, I have an old and new pair of the MT900 undershorts - and it is the same issue with crazy tight legs.bottom sizing (cannot get them on) but waist stated way larger . As the issue on the latest MT500 and MT900 is the same, below I paste the issue from the MT900 as its the same. As others have said, the latest (2021) version of these are sized/cut for a stick insect. Dont buy without trying on in store. Likely uou will need to size 2 times up and take the waist in. Decathlon, PLEASE fix the weird 'large waist/ultra skinny legs' fit - its mad! I have a 32" Waist, and like the pair of these I got years ago bought Large, which used to be for 82-89cm and fitted well 32-34" with a slim athletic legs/hips. The latest version Large MT500 now state on the label they are for 98-104cm (38-41")!! However, despite the claimed size being way bigger than my waist, I could barely get these on my thighs/bottom, they are so tight around the thighs and bottom, my legs started throbbing! And I have a slim athletic shape legs/bum - not a 'Chris Hoy' figure. Friends keep telling my I need to eat more and put on weight, so its not my shape, but the new cut of the shorts. The waist might just at a push stretch to 41" - but there is no way anyone with that waist would get them above their knees. The shorts themselves (my last pair) are excellent especially for the price, brilliant - the pad is fabulous, comfy, light. Such a shame they have totally ruined the cut. I am going to have to try an XL (for my slim build & 32" waist!) in store and hope I can then take the waistband in - as they are otherwise great value undershorts. Maybe these were a mis-manufactured batch - however I also have the excellent MT900 undershorts - and also an old pair - and its exactly the same issue. You would need absolutely pipe cleaner legs, no bottom and a huge waist for the cut to have the correct snug but comfy fit.
It makes my bottom feel numb instead...not comfortable.
Hi Thomas,
Thanks for your feedback about our ST 500 mountain bike under shorts. I'm sorry to hear that they are not comfortable for you.
If you're dissatisfied with the shorts, you may return them at any of our stores. Our product designers are riders themselves and monitor the reviews, so please rest assured that they are continuously working to improve our products.
Jason
Digital Sport Leader
Cycling & Roller Sports
I přesto, že použitý materiál včetně polstrování vypadá slušně, tak kraťasy jsou pro mě nepoužitelné, protože gumové manžety na nohavicích jsou až příliš těsné na danou velikost. Bohužel nohu "škrtí" a nedokážu si představit, že bych v nich měl vydržet vyjížďku.
Dobrý den, Radime,
děkujeme za Váš čas věnovaný recenzi tohoto produktu. Každá zkušenost je velmi cenná a pomáhá nám s vývojem nových modelů.
Chápeme, že ne každý střih kraťas vyhovuje všem naším zákazníkům. Z těchto důvodů máte vždy 90 denní bezplatnou lhůtu na vrácení pouze vyzkoušeného zboží.
Za způsobené komplikace se velice omlouváme.
S láskou ke sportu
Tereza
Ich habe vor Jahren die ROCKRIDER MTB Innenhose ST 500 Herren schwarz in 2xl gekauft und die ist sehr weit. In XL bekomme ich sie gar nicht erst an.
Sitzt perfekt, sehr leicht,
Jo
Nach der ersten Freude kam leider die Ernüchterung. Das Polster ist leider schief eingenäht und sitzt daher nicht richtig. Um eine Retoure zu vermeiden habe ich sie trotzdem behalten und ausprobiert, aber das Polster sitzt leider so schief, dass die eine Gesäßhälfte quasi ungepolstert ist. Die Beinabschlüsse sind tatsächlich recht eng, aber das hat mich weniger gestört. Insgesamt eigentlich eine ganz gute Innenhose mit Abstrichen.
Material, Verarbeitung, Polsterung und Preis sind gut. Aber: die Gummibündchen am Beinabschluss sind VIEL zu eng und schnüren den Muskel regelrecht ab. Bei mir in Größe XXL (eigentlich habe sonst L oder XL) ist der Durchmesser der Gummibündchen gerade mal 15 cm; der Umfang also 30 cm. Mein eher "normaler" Oberschenkelumfang ist aber 62 cm. Klar dehnt sich der Gummi, aber angezogen ist er dann maximal gdehnt/gespannt und schnürt alles regelrecht ab. Total unbequem, ja unangenehm bis schmerzhaft. Kann man so nicht verwenden. Ich weiß nicht ob das nur ein Fehler bei meinem Exemplar ist oder generell; aber so ist das Teil unbrauchbar. Ich habe die Gummibünde jetzt abgetrennt. Dann rutscht die Hose beim Fahren zwar nach oben, das ist aber das kleinere Übel. Insgesamt: so nicht zu gebrauchen; mit realistisch weiteren Gummiabschlüssen wäre es wohl sehr gut.
Hallo Michael,
vielen Dank, dass du dir die Zeit genommen hast, um deine Erfahrung mit uns zu der Mountainbike-Innenhose ST 500 MTB Herren schwarz von ROCKRIDER zu teilen.
Wir bedauern sehr, dass die Mountainbike-Innenhose ST 500 MTB Herren schwarz von ROCKRIDER nicht deinen Vorstellungen entspricht. Dein Feedback werden wir an den zuständigen Produktmanager weitergeben. Wir arbeiten an einer kontinuierlichen Verbesserung unserer Produkte und dabei ist uns das Feedback unserer Kunden besonders wichtig.
Solltest du weitere Fragen haben, steht dir unser Serviceteam (service[at]decathlon.de) jederzeit zur Verfügung.
Wir hoffen, dich in Zukunft wieder von unseren Produkten überzeugen zu können und wünschen dir noch ein schönes Wochenende.
Mit sportlichen Grüßen
Frederic
Team DECATHLON
Etwas eng
Sehr gute gepolsterte Hose
Muy cómodo
Hola José Luis,
Desde el equipo de ciclismo agradecemos la confianza que depositas en Decathlon para realizar la compra del short interior MTB ST 500. Así como, la valoración positiva que haces de nuestro producto en la web.
El comentario y la puntuación que has expuesto nos anima para seguir trabajando y sacar los mejores productos. Este modelo incorpora nuestra nueva badana para mejorar en confort durante la práctica deportiva y con corte que permite mejor adaptación y evita la sensación de presión en las piernas.
Nuestro equipo trabaja para satisfacer a nuestros usuarios ciclistas, buscando la mejor calidad y prestaciones con los precios más ajustados posible.
Esperamos volver a verte por nuestras tiendas y por la página web.
Reciba un cordial saludo, que tengas un buen día.
Atentamente,
Javier - Experto producto ciclismo Decathlon
Muy cómodos. Lo utilizo para moto de enduro y ninguna molestia
Hola Diego,
Desde el equipo de ciclismo agradecemos la confianza que depositas en Decathlon para realizar la compra del short interior MTB ST 500. Así como, la valoración positiva que haces de nuestro producto en la web.
El comentario y la puntuación que has expuesto nos anima para seguir trabajando y sacar los mejores productos. Este modelo incorpora nuestra nueva badana para mejorar en confort durante la práctica deportiva y con corte que permite mejor adaptación y evita la sensación de presión en las piernas.
Nuestro equipo trabaja para satisfacer a nuestros usuarios ciclistas, buscando la mejor calidad y prestaciones con los precios más ajustados posible.
Esperamos volver a verte por nuestras tiendas y por la página web.
Reciba un cordial saludo, que tengas un buen día.
Atentamente,
Javier - Experto producto ciclismo Decathlon
Precio calidad perfecto 👌
Hola Nilson,
Muchas gracias por escribir tu opinión en la página web de Decathlon, nos hace felices saber que has encontrado el producto que buscabas.
Nuestros equipos trabajan para satisfacer a nuestr@s usuari@s ciclistas, buscando la mejor calidad y prestaciones con los precios más ajustados posible.
Tu comentario y puntuación positiva nos anima a seguir esforzándonos para mejorar, y también ayudará a otr@s clientes a encontrar los productos que mejor se adapten a sus necesidades.
Te esperamos en cualquiera de nuestras tiendas Decathlon y en la página web decathlon.es
¡Hasta pronto!
LLUÍS BARRERA
Experto Ciclismo Decathlon
Cómodo.
Additional Product Information
Composition
Main fabric
- 13% Spandex
- 87% Polyester cationic
- 56% Polyurethane
- 1% Polyethylene low density
Foam
- 100% Polyurethane
- 87% Polyester cationic
Yoke
- 14% Spandex
- 86% Polyester cationic
- 56% Polyurethane
- 1% Polyethylene low density
Lining
- 100% Polyethylene low density
Undershorts support.
Bibless undershorts can be much more practical. But do you get enough support? To guarantee the support you need, even without straps, we have made a pair of undershorts that hugs your body just like boxers. The elasticated waistband adapts to fit you and stays in place with no adjustment needed.
A 2nd skin with comfort to boot.
The pad has been designed for more regular users looking to progress in MTB. The support foam is also soft but more dense. It protects pressure zones for up to 4 hours. The foam is soft and the stretchy outer layer hugs the cyclist's body so the pad can follow their movements. Foam thickness: 13 mm Foam density: 220.5 lbs/m³ Foam firmness: 25 KPa
Shorts, undershorts.
Undershorts are to MTB what kilts are to Scotland: you wear them against your skin! To avoid chafing, we therefore recommend changing them and washing them as if they were underwear. And when you're riding, your shorts and undershorts should never be attached. Why? Because each has their own role to play: - The undershorts stay in place for comfort and support. - The shorts move with you for better freedom as you cycle along.
Care instructions
You can find detailed info on looking after your mountain bike clothing on our website
Product tests
Our team of product designers based at the B'Twin Village in Lille is continuously working to make cycling more comfortable for our users. Our obsession is to create products that meet the specific cycling needs of our users and eliminate things that get in the way of their rides.
Determining the environmental impact of our products
A product's environmental impact is calculated for its entire lifecycle using various indicators. An overall rating (ABCDE) is given, allowing you to easily identify products with the best environmental performance by comparing similar products to each other (T-shirts, pants, backpacks etc.). Decathlon openly displays the environmental ratings of its products. To find out more: http://sustainability.decathlon.com/
Origin
Imported
Product testing
Our engineers always have real riders test all our products in real conditions. These tests round out our lab tests and let us validate all our products before they hit store shelves.
Storage instructions
Store in a clean and dry place.
Superior quality. Unbeatable prices.
For 40 years, Decathlon has delivered the best value in the retail sports industry by offering high-quality, sustainable and cost-effective products.
Decathlon makes the difference
-
Research and development
delivers high-quality cost-effective products
-
State-of-the-art production processes
minimize manufacturing costs
-
Optimized supply chain
reduces retail prices
-
Minimal retail footprint
lowers overhead and indirect costs

Rockrider ST500, Mountain Bike Undershorts, Men's
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Heavy products return policy
If you return a product you will receive a refund for the purchase price plus any applicable sales taxes, less any non-refundable charges.
Decathlon will cover all shipping costs associated with your return except for items excluded from our return policy such as bikes, basketball hoops, snowboards, surfboards, tents, and other larger / heavier items.
Return costs for heavy products:
Weight Thresholds | Shipping within California | Shipping outside of California |
---|---|---|
> 9 lbs | $20.00 | $25.00 |
> 30 lbs | $50.00 | $65.00 |
> 100 lbs | $100.00 | $125.00 |
> 200 lbs | $200.00 | $230.00 |
If you return a product at any of our store locations, we will gladly help you find the best alternative product or refund you on the spot.
