[Drth Vadr]

Hi everyone I'm new around here and I was hoping for some help choosing the right geometry and fit for a Dh bike. I don't have the luxury of living in a area where every LBS has a Dh bike on the floor to use as a template. Every size DH bike seem to have a wide range of different geo angles. Should I be using the reach I like for AM/Trail bikes to choose a DH bike. I'm 5'11 32 inseam and proportionate. I seem to think I should be on a size smaller then what I currently ride in AM. I like buying online So I really need to be comfortable and confident buying a DH bike without riding it as I am with AM bikes.

 

[ustemuf]

5'11..... pretty much a medium in the majority of frames will be good for you.

 

[Sandwich]

23.5" effective TT is the magic number for me @ 5'11" and 32" inseam. Medium Sunday, 18.5" Trek Fuel, Arrow DSS3, all fall right about 23.5-24, and they fit great. the trek is arguably a tiny bit too long.

best bet is to buy a medium, targeting an average TT length, and then see if you want larger or smaller. I've ridden longer bikes and enjoyed them, and shorter ones and hated them, so I know I don't want to go small.

 

[ebarker9]

That's interesting info. I'm pretty much exactly the same height/proportions and I'm on a medium Socom, which feels perhaps a tiny bit short in the top tube. Like there's a relatively small sweet spot where I can stay balanced front/back, low, with my weight on my feet. That's listed as a 23" ETT...wonder how much of a difference there is going to 23.5" or so.

 

[6thElement]

5'11" is into large territory, you could be M or L.

 

[Sandwich]

Couldn't tell you what kind of a change it'll make. Some people LOVE short bikes and others like limos. I rode a large Demo and it felt great, but I've also had a 24.5" Prophet and it was a nightmare on anything other than flat.

It seems like fit generally comes down to taking a suggestion then extrapolating based on how you feel. I think my arrow (at 23.6") with a 55mm stem was THE bike I've felt most naturally comfortable on...but until they start making custom frames, you kind of make what it is work.

I don't fully understand reach and stack (never took the time to learn) but it seems that certain people have opinions on what measurement is best, and a lot of them depend on other things, like fork length or head angle or what have you, so the old standards seem to work pretty well, along with downtube length.

 

[bizutch]

Every person I've ever met at 5'11" is very happy on a medium. The only frame I know of that would be an exception is older model Morewood Izimus. Their large was everyone else's medium.

The only person I would put on a large is someone coming from motocross who only plans on riding at Mt. Snow or Snowshoe. The other 99 percent of DH riding, you'll want to be on a medium. That puts you at a 46" wheelbase.

Regardless of what anyone says, the top tube length or "reach" is negligible when you get a bike up to speed.

Adult motocross bikes come in 1 size.

 

[atrokz]

I'm 6'1" and going from a M to a L made a major difference with my control at speed and ability to stay over the front end without getting bucked. Exact same bike. Not sure where you get that most people 'belong' on a M. A bunch of racers made the switch to larger frames in the past few years.

That said, at 5'11", try a M first.

 

[ebarker9]

I think the relationship between foot and hand position at speed is not at all negligible and the top tube length certainly plays a role in this. And adult motocross bikes do come in 1 size but there are some pretty big differences in the way that those are ridden compared with a DH bike.

 

[Drth Vadr]

I ride a 23.75 TT on my AM bike. Old DH bike I use to have was 23.9 TT, but I always felt like the bike was a tad to big and I felt unbalanced and to stretched out when it was time to get behind the seat. I've been thinking that a 23.25 or 23.5 TT may be perfect, something just below 46 WB. Now it is time to decide what frame.