General Cycling Discussion - Fit question

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wez312
07-13-08, 05:01 PM
So let's say I am riding a 60cm bike right now, have been for a little while, according to the competitivecyclist.com fitting calculator thing I should be riding about a 49cm. How much of a difference if this going to make?

Here are my stats from competitivecyclist.

Measurements
-------------------------------------------
Inseam: 29.5
Trunk: 24
Forearm: 13
Arm: 23
Thigh: 22.5
Lower Leg: 22
Sternal Notch: 56
Total Body Height: 69


The Competitive Fit (cm)
-------------------------------------------
Seat tube range c-c: 48.5 - 49.0
Seat tube range c-t: 50.0 - 50.5
Top tube length: 53.4 - 53.8
Stem Length: 10.2 - 10.8
BB-Saddle Position: 71.5 - 73.5
Saddle-Handlebar: 48.7 - 49.3
Saddle Setback: 0.9 - 1.3

Thanks for your help!


alanbikehouston
07-13-08, 06:12 PM
I think your measurements may be off. If you are 5'9" tall and you have been comfortable on a size 60 bike, there is no way your inseam is just 30 inches. A cycling inseam is measured from the floor to your public bone, and more likely your cycling inseam is 33 inches or 34 inches.

To measure your cycling inseam, you need a book that is about 18 inches long and two inches wide, a tape measure, and a friend. Pull the book up against your crotch until it is uncomfortable. Then push the book an inch higher. Have your friend measure from the top of the book to the floor. Take the measurement about seven times, and the medium measurement is your cycling inseam.

An easier way to see if a bike fits is simply stand over it. I am 5' 9 1/2 inches tall. When I stand over my size 60 and size 62 bikes, the top tube is pressing slightly against my crotch. But, not to a painful degree. When I ride this bikes, they fit me perfectly.

For myself, there are three sizes of bikes that work for three types of riding. Using traditional geometry, a size 60 fits me well for urban riding in heavy traffic where I want a higher head position to watch motorists closely.

For faster riding on road with little or no motor traffic, I would want a bit lower bar position, and would ride a size 57 or size 58. If I were forty years younger, and racing on a closed course, I would select a size 55 or 56, to get the bars ultra-low, and make it easier to ride in an aero position.

Go to two or three shops, and tell the staff EXACTLY how you plan to use your bike (urban commuting, touring, fast touring, racing) and get their fit suggestions. Which ever shop tries to put you on a bike less than a size 55 is staffed by idiots, and you should leave immediately.

RonH
07-14-08, 06:43 AM
So let's say I am riding a 60cm bike right now...

Inseam: 29.5
???

My inseam is 30" and my bikes are 57cm.


deraltekluge
07-14-08, 09:06 AM
So let's say I am riding a 60cm bike right now, have been for a little while, according to the competitivecyclist.com fitting calculator thing I should be riding about a 49cm. How much of a difference if this going to make? The numbers just don't add up. 11 cm difference is huge! On a road bike, Trek calls 60 cm "large" and 50 cm "extra small". You're a bit less than "medium" in height, and with short legs. The 60 cm bike has a stand-over height of 80.3 cm (31.6").

Siu Blue Wind
07-14-08, 09:17 AM
???

My inseam is 30" and my bikes are 57cm.

???!!! My inseam is 30" and my bike is 50cm. :twitchy:

You guys are proportioned funny. :p

wez312
07-14-08, 09:35 AM
Ok so I measured inseam again and the most it is is 32"...so apparently that should put me in the range of anywhere from 50cm-56cm? (ideally)

deraltekluge
07-14-08, 09:39 AM
???!!! My inseam is 30" and my bike is 50cm. :twitchy:

You guys are proportioned funny. :pOr you are. Or, perhaps more likely, talking about different types of bikes??

Again, using Trek as examples, their SU 2.0 "urban" bike in "medium" size has a 19.5" (49.5 cm) seat tube and a 77.5 cm stand-over; while their 2.3 "road" bike in "medium" size has a 22" (56 cm) seat tube and a 76.6 cm stand-over.

alanbikehouston
07-14-08, 09:52 AM
The best way to find out if a bike fits is to test ride it. Pick a model you are interested in. Stand over the bike with your belt buckle against the back of the stem. Look for a bike where the top tube will lightly brush against the crotch of your jeans when you are standing flat-footed up against the stem.

Have the store staff adjust the saddle height and bar height, and take the bike for a test ride. If a bike fits you properly, you should have a comfortable fore/aft weight balance. If too much weight is on your hands, the top tube is too long. If very little weight is on your hands, the top tube is too short.

Bike fit also depends on how and where you ride. If you ride on busy streets, with vehicles on your left and right, you need have your head up where you can watch those vehicles closely. If you plan to get a racing license, and enter short time trials, you will want a bike that puts the bars into an ultra-low position.

Visit two or three good shops. Take test rides. Ignore internet advice (except the foregoing).

Siu Blue Wind
07-14-08, 10:36 AM
Or you are. Or, perhaps more likely, talking about different types of bikes??

Again, using Trek as examples, their SU 2.0 "urban" bike in "medium" size has a 19.5" (49.5 cm) seat tube and a 77.5 cm stand-over; while their 2.3 "road" bike in "medium" size has a 22" (56 cm) seat tube and a 76.6 cm stand-over.

I'm 5'5" and have a road bike with compact geometry. I think competitive cyclist is measuring for road bikes because it doesn't match my mtb bike measurements.

http://i123.photobucket.com/albums/o286/Flycrow/seat1.jpg

Longfemur
07-14-08, 11:57 AM
There's got to be something way out of whack with how you're measuring something. It's pretty much impossible to ride a 60 cm bike when a proper fitting one would be 49 cm. For what it's worth, I have a 30 inch "inseam" and I ride 49 cm centre-to-centre, and even that just gives me minimum clearance when in bare feet (just right when in riding shoes, but not tons of clearance).