Purchasing a road bike

Question
How do I know what size frame is good for me?  I am about 5'11' and about 185 pounds.  Is there a way to figure what size frame I should be looking for?


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Followup To
Question -
I am going to enter my first triathlon in August.  So for the next 2 months I am going to train train train.  I have a mountain bike but I think I need a road bike.  What do you think?  But everywhere I go they want $650 to start.  I don't have that kind of money.  What are my alternatives?  I really need this bike to fit my frame.

Thanks
Answer -
Hello Gary,

Most of the times they wouldn't let you start on a mountainbike!
Second, when your are knowing that you want to like riding roads maybe you can sell your mountainbike.
A other option is to look at a used one, there are many athletes who want new materials for every year.
I can't advice you to take a look on Ebay, and triathlon magazines and websites. Maybe there a road/triathlonclubs where you can find info or even your new bike.

When you have other questions, i'll be here.

Michael

Answer
Hello Gary,

I have tried to calculate for you your size.
When I did it right, your about 1.55 mtr tall.
And therefor you should see a bikeheight from not taller than a 48 centimeter.
But it also depends how long your legs are.
Go to a good cyclestore, where they can measure you and give you advice about height, and length for the specific bike.
Maybe they also have a nice secondhand bike for you.

I hope this will answer your question.

Michael