Sincitycycler

I saw this at some Mtb site but I forgot what link it was .

Is this a valid system for fitting? According to this formula, I have a 36" "bike" inseam and hould be using 22", which seems pretty big . BTW, I'm 6'2" and use a 61 cm Roadie...

Good fitting guide?

Sincitycycler

bump

Raiyn

No it isn't a good guide. You want three to four fingers of room between the top tube and the boys. Try a 19" Also there's no need to bump threads

Maelstrom 

Actually, if that were a method at all, I would like say -17 or -18. Interesting idea, I am gonna have to play with the idea ...

BTW go try a 19"

ChroMo2

a 19" frame would be good, but you would really appreciate a 21" frame. Smaller frames are good for trails. Bigger frames are better for long rides on pavement, they're actually faster.

MasterSezFaster

Ok Sin... did I not answer this for you in another thread?

My bad, I just check and I answered it for a different roadie I, my self, also ride a 61cm roadie but mtb's are a totally different breed.

Here is what I said to the other guy (with some modifacation), "I am 6'2" with a 34 1/4" inseam and 20" would be the largest size I would get and that would be pushing the limit and if I were only going to be on fire trails or well groomed trails. If you will be riding technical trails I would say look into getting an 18" or 19" frame if it will be for XC and a 17" frame if the trails are VERY technical. You need to remember, you do not size a mountain bike like a road bike. They are two totally different animals "

MSF

Killer B

WTF are you posting in the MtnBiking forum if you're a Roadie?

The correct answer to your question is "Way Big", go figure....

Raiyn

Considering this is the Mountain Bike section and not the Riding on Pavement section one should presume we're not talking about pavement bikes here

Sincitycycler

WTF? I want to diversify my riding experience. Yes , even in the desert it gets cooler and I don't like going 25+ mph on my road bike with cold wind blasting in my face and engaging in runny nose heaven.

MasterSezFaster

Ahhh don't worry Sin, just like in the roadie section some folks here have their head up their ***
No need to justify your self, ask away.

MSF

mtnbiker66

Fer sure.

Krazy Koz

Kudos to you for actually taking your inseam measurement; I would say that 85-90% of all people who buy bikes never do this. Once you get your inseam size, all you need to do is plug it into one of the two frame size formulas: one for MTB frames and one for road bikes. To get your MTB size, take your inseam measurement, multiply it by .65, and then subtract four inches from that. Or stated another way:

MOUNTAIN BIKE FRAME SIZE:
(inseam * .65) - 4'' = frame size
ergo,
36 * .65 = 23.4 - 4 = 19.4

Therefore, you should ride a 19'' frame.

ChroMo2

I ride 90% on pavement. I ride between 3 and ten hours when I ride. My bike is built for real world cross country racing (not a closed circuit) it goes anywhere, anyplace, anytime, and it does it fast! When I go off road I have no second thoughts of my capabilites. I'm 6'2" with a 36" inseam and my 21.5" stumpjumper with ridgid fork took me 135 in a day, 80 miles on singletrack. My bike never gets locked or attached to a car to take it somewhere. By design, my bike can pace many roadbikes and still do trails reserved for dual suspension bikes. My current frame size is 19" front suspension only (to slaughter the trails) I miss having a bigger frame, but since my riding techniques are above average, I have great compensation in my abilites to do on and off road riding.The rider is a big factor in the equation. I don't know what your limits are, but I don't have any.

Sincitycycler

Thanks!

Brian

If it were only that simple. Based on my experience selling bikes, and my own experience with the bikes I currently have, there is no simple formula. If I've got 4 bikes ranging from a 15" to a 19", I don't see how your forumla is valid. Of course, that variation can be applied to my inseam as well. Are you measuring pants, or are you measuring your body? My Old Navy jeans just touch my shoelaces. My Armani slacks measure about 2 inches longer, with a proper break at the cuffs. The only way to properly determine your frame size is to check the standover on the actual bike you're going to buy. You'll also need to check for proper reach and leg extension. And plenty of people choose the wrong size.

dirtyamerican

Assuming all bike frames have the same standover height and geometries, which they vary by a lot!

MasterSezFaster

19" is your starting point. Try bikes between 17" and 20". Here is where mtb's are like roadies, the different geometries will affect what size frame you get as well as the terrain you are going to ride.

An example would be, a large framed RockyMountain RMX has the same standover hight as a large Kona StabPrimo but the top tube of the RMX is very short compared to the Stab because one is more of a racer(the Stab) and the other is more for big hits. Now if I go get on my XC bike (Bianchi Caál 8800 48cm/19") I have very little standover compared to either of the others and a longer tt.

As with the road bikes, you need to ride as many different bikes as you can to find the "right" one for YOU. You may even get a bike on the larger side. I have a buddy that races semi-pro xc (constantly places in the top 10) and does a lot of 24hr events, he is 5'9" (not sure about his inseam but he does not have long legs) and rides a 20" bike. He uses the same bike when we hit the jumps and drops. Just pointing out it will be what you feel most comfortable on.

MSF

Sincitycycler

hooligan

It's whichever feels good. Test ride the bikes.

stapfam

The 3 to 4 fingers is the best way to measure, but a 19" from one manufacturer will be different to a 19" of any other manufacturer. Get the 3 to 4 fingers and then check out top tube length and reach to the bars.

(Thinking Kona that have an extended seat tube above the Top bar and a longer reach than most)

Krazy Koz

Measuring your body part, from the bottom of your foot to the bottom of your pubic bone. I would certainly hope that nobody would take a look at the tag in their pants and go to the bike shop hoping to get a good bike fit. I wouldn't argue that anyone should simply trust an abstract number over their own experience on a bike. However, I would argue that frame size has become standardized to a large extent and while there are differences between the geometry of one bike and another, I would also say that those differences are smaller than the similarities (except with Kona and Fisher bikes, I've noticed).

A formula will not give you a size for every bike in every circumstance, but it will give you a starting point, and one that will more than likely get you pretty close to your size.

Big caveat: I would say that the formula I presented is what I use for trails. For downhilling, freeriding, and hucking you are going to want an even smaller frame.