Where can I rent bikes in Arnhem, The Netherlands?

You can take your bike on the train outside rush hours (rush hours: 06:30 - 09:00/16:30 - 18:00) and it will cost you €7.5 per bike, per day. But don't get your bike in Amsterdam and transfer it to Arnhem, this is just way too much hassle.

According to this website, there are 5 bikeshops where you can rent bikes in (the neighbourhood of) Arnhem. Namely:

• Reerink Rijwielen (on two locations)
• BikeLife Groesbeek
• Nol Mastbergen
• Peter Oversteegen (PDF document).

Here is a map showing these bikeshops around Arnhem. In this way you can decide which shop you choose based on the region where you want to bike.

I've linked the above names to the rental web page (or contact page if there's no rental page) so you can see the information for yourself. As you don't speak Dutch and the website might be unavailable I've also summarised the information below. Prices are per day, unless otherwise noted. Regular opening hours are 09:00 - 17:00.

Reerink Rijwielen

Bike's can be delivered and picked up by the company (probably additional costs). On Sunday and Monday they're closed, so no bikes can be rented or returned.

• Mountainbike - €15
• City bike - €7.5, with electrical engine €30
• Kid bike - €5
• Half wheeler - €7.5
• Deposit - €50

It's mandatory that you can show an identification document. If you choose a mountain bike, keep in mind that you have to return it clean. Otherwise a €10 charge per dirty bike will be incurred.

BikeLife Groesbeek

This company does not have rental information on their website, but you can e-mail them or give them a call to ask for their rates. Closed on Sunday and Monday.

Nol Mastbergen

Closed on Monday and Friday open until 20:00.

• Mountainbike - €15
• Three speed city bike - €7.5
• Electrical bike - €22.5
• Tandem bike - €15
• Deposit - €100

It's mandatory to show a valid identification document. If you rent a bike for a week you will only pay 5 days. If you want to rent a bike you can make a reservation by phone (+31 317 31 23 72).

Peter Oversteegen

Closed on Mondays unless it's a school holiday. This varies per year so if you want to rent a bike on Monday you should just contact them to ask if they're open.

• Mountainbike 29" wheels - €20
• Mountainbike 26" wheels - €17.5
• Kid mountainbike - €12
• Multispeed City bike - €8.5
• Multispeed Tandem - €18
• Kid bike - €6
• Half wheeler - €6
• Kid tandem - €18 or €10 for a half day

In addition to Andra's answer: most larger bicycle shops can provide rentals.
And yes, taking bikes on a train is going to cost you. Not sure about the current rate, but was something like €10 one way when I last did it years ago, so it may well be cheaper to rent.
There are also restrictions on bikes in trains, limiting you to specific trains at specific times (no rush hour trains for example) and frequently a maximum of 2-3 bikes per train car that has facilities to take bikes (not all do) so you may not even all be able to take the same train.