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DH Bike Sizing?

12570 Views 8 Replies 4 Participants Last post by  Techfreak
I'm currently looking for my first DH bike, but I'm not sure what size I am. I'm just about 6 feet tall and like a longer bike. I'm currently loving the feel of my size long Banshee Rampant with a 590 mm toptube, and I've noticed most medium DH bikes are a bit longer than this, by 7mm, so It's the length I'm looking for. BUT I've been told the toptube does not really give you the length of the bike. I don't want my DH bike to be shorter then my small travel bike, so how do I know what I'm looking for?
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At 6 feet, you can probably fit on most medium and large bikes out there. The big difference between your Rampant and many DH bikes is the seat tube angle. A typical DH bike wil have a seat tube angle in 55-65 degree range while your rampant is probably 71-73 degrees. When you measure effective top tube length you go all the way from the center of the headtube to the center of the extension of the seat tube along a line parallel to the ground (horizontal line).

On the other hand, the measurement that really matters on a DH bike is what is called "reach": this is the horizontal distance from the bottom bracket to the center to the headtube. This is a measure of the size of the cockpit when you are standing and not seated.

Banshee lists reach and stack measurements for their bikes, so you can look up both the Rampant and the Legend and compare the sizes. You can also use a geometry calculator such as this one:

to calculate reach and stack for other frames you are considering.

In the end for you the choice between medium and large will probably come down to riding style and the kind of terrain you ride most frequently. Large frames: longer wheelbase, more bike in front of you, more stability at speed. Medium frames: more weight on the front end, more agile in the tight and twisty and slow speed manouvering.
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I am 6 feet tall and bought a Giant Glory 2010. On the bike frame has a sticker on it which says says 5' 6' to 5' 10". I am six feet and have enjoyed the bike. I have had a number of over the bar crashes though which makes me wonder if the size of the bike has any influence on that. I have been riding DH for ten years and did not have allot of OTB crashes before. I am wondering if I should have purchased the large frame.
Wow, I spent about an hour playing with that calculator. My Rampant is LONG! Thanks for showing me that, the bike I was looking to order is way too small. Back to the drawing boards.
Yeah, on a DH bike the reach is more important than the Effective Top Tube measurement. I'm almost 6'6", so finding a bike that fits has been a hassle.

daisycutter - yes, the frame may be too short, which is leading you to having too much weight over the front wheel. There are a couple of things you might want to check: a.) how much is the fork diving? Crank up your LSC a bit to make the fork stand taller or put in a stiffer spring. This is my current problem with my DH bike, so in goes the stiffer spring. b.) raise your stack height a bit to shift your weight back a little. My hardtail is small for me and I have to jack up the stack height to make it rideable. When I do it is golden. If I don't, I'm OTB all the time.
Techfreak, I spent the last day scouring the internet for a DH frame and a FTW FB10 has a 16.9" reach, might fit a tall guy like you?
Funny you should ask. I have an XL and it is PERFECT. Besides, Frank really knows how to build a bike.

LOL - saw your post on another board too!
Lol your ERegular aren't you. it's a sick bike. I'de love to support your buddy but the geo seems off for me, so I figure I'de pass it on. Too bad I passed it on to the guy that told me about it :p.
Yep. The geo is somewhat adjustable as the shock mount has 3 positions. FTW is an absolute craftsman when it comes to building bikes. Maybe you should take a look at a Knolly Podium or a Canfield Jedi. That was my short list anyway.
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