Road Cycling - Geometry and fit

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.




View Full Version : Geometry and fit


Phil Biker
05-24-00, 07:03 AM
Shopping for new road bike; old Dawes recently ripped off. Many (incl Xavier) say geometry and fit are key. So where do I go from here? Pls don't send me to LBS, as I can't tell hacks from pros. I'm a 6'-1" long-mileage biker (coast to coast in my youth); age up and fitness down now, so want something light. What are the main choices in geometry, and how should I make them? Is there a reference source that deals with this? Any tips for selection? How about tips or rules or thumb for fit/adjustment? I've seen references to FitKit -- any good; available where? Thanks for any help


Xavier
05-24-00, 11:03 AM
Phil,

I know. That is why I began my little business and I get many calls a day imply on this question.

Call me, it is free to you (1.888.285.5835)and I want to inform you. I get a few calls a month on riders that purchased wrong sizes. Either at LBS or internet or via Fit kits. This really angers me.

Do you have a frame now? Do you like? If so measure that and look for companies that offer that size. Again top tube is most crucial.

Many shops will usually ask you height weight and inseam. What do height and weight have to do with frame size? None. Inseam is roughly a measure to use as guideline. Shops will ask you inseam and then look at some generic chart to determine correct frame for you. They overlook that all frames are measure different (c-c, c-t, c-clamp) which is which? It gets confusing. And the main problem is the top tube. Many shops disregard this crucial lenght. Recently a few shops are asking this and pointing this out to consumers as they are fianlly seeing what I am doing. Yeap, I get many shops call me in secret to see how I do this. If only they actually knew cycling.

Bottom line is you will need to know what top tube you want and everything esle will follow.

Fit Kits? I do not like them. Why? Many shops doing these do not know. They buy them and follow instructions. Generic intructions. Forgeting we are all different with different needs. You may want to sit farther back or more forward, or you may want shorter top tube or longer, or smaler frame. What then? If using Fit Kit, go to a person that actually knows. One needs to know exactly where to take measurements. This is very hard. Also only take that information with a grain of salt because what they determine for you is according to the person that wrote the "instructions".

As far as frame materials, that is all purely personal preference and I hate it when shops tell people this is better than that. Why? Because it costs more? Nonsense.

Here I ask a lot of questions. Mainly the type of riding you do and this will help me recommend materials.

Xavier
05-24-00, 10:29 PM
Snowplug,

All your answers are personal to each rider. There is no set stem lenght or handlebar height. It is what you prefer.

You can see a so called "expert" but many simply are not and those very few that maybe will only give you a generic fit. Again we are all different. You may want to sit higher or lower or closer or farther.

Once you get a good top tube use any stem reasonable and start by there. This is mainly trial and error.

In the normal threaded stems you can raise or lower very easily. Not so with the new threadless systems. So be very careful there.

All the bikes we ship out of here we do not cut the forks on the threadless systems just for this reason. You determine where you want the stem to be. I always tell people to also add spacers on top just in case. Better to cut long than too short.

Many shops will simply cut with one 5mm spacer and then you really are in trouble. I get many call due to this. I wish shops would know more and not put riders in this position. Now they are seeking new forks or new stems with rise.


Xavier
05-24-00, 10:37 PM
Phil Biker,

Contact Dawes. I am sure he will respond quickly. Hopefully you knew the frame size you had and Dawes knows the geometry.

This way you can know the top tube lenght on the bike as you liked it.

Once you know that, you are set. Look for companies that give you that exact top tube. Once you narrow those down then you have the material to narrow down (steel, aluminum, etc.)

Best of luck

Snowplug
05-25-00, 12:41 AM
Xavier,

If you size your frames by top tube length, what handlebar stem length do you work to, and how far should the stem handlebar centre be above the top tube?

rexydog
06-08-00, 04:39 PM
Snowplug,
where are you located? One thing that irritated me in my last purchase, (ciocc steel) was that shops were really not interested in giving me allot of attention in getting comfortable, i.e. short test rides, unwillingness to change out components and such. There is a well known shop in boulder that understands that when you pay 3k plus for a new bike, you deserve to get some attention. I agree that most shops don't know how to use fit kits or listen to their customers. We spent about three hours making damn sure that my bike fit, was comfortable and rode/handled well. That's service.

Xavier
06-09-00, 10:01 AM
snowplug,

When people call me first thing I do is ask them if they currently have a bike. If so do they like the fit. Many times they say yes. Then job is done. Simply measure the top tube and buy a frame nthat gives you that top tube. Some people go out of their way in time and money to pay for fit kits, many administered by non knowledgeable personnel that simply open an intruction book and follow step by step. Sure this is OK but it is only a generic formula. We are all different and require different needs. You may be accustomed to a specific fit that you have come to like. So go with that. Many people come out of this fit kit sessions with a new position and many really hate it. Of course they do. They were accustomed to something else.

Now, of you do not have a bike with nice fit that accomodates YOU then all anyone can do is reccommend. Sadly this here is trial and error. If you are very lucky a local shop may have a bike that may accomodate you and you can test ride. You will not get a 3 hour test ride but you can quickly see the reach to the bars. If OK then stick with that. Later on you can experiment with stems. As far as stem height, this is a hard one now days with the ahead stems. Why? Once the fork is cut, many times you are stuck there. That is why I tell all to buy a frame w/o the fork being cut and use many spacers on top and bottom. Once you find the correct height then make the final cut. Many shops do not know about cycling and quicly cut these off and more times than you can imagine I get calls on this about people wanting to see of there is a solution. Sadly no cheap solution oher than a new fork.

Bottom line is you are the expert. I answer this question many times a day and very few consumers get angry at me as they wanted to talk to a salesmen that will tell them exactly a number. These folks set themselves off to buying wrong sized items as they will be sold into sales pitches from shops with overstocked goods they need to unload.

Again if you currently have a bike look at the measurements. If you would like shorter reach then you determine what would be shorter (1cm is usually good either way) Again, did God make us all the same. No we are all different and like different things. So why would a chart be used for all?

Feel free to call me as I love to discuss this with anyone. Take care.

Snowplug
06-09-00, 10:05 PM
Rexy Dog,

I work for Coca-Cola, here in Saudi Arabia, as an Expatriate and started riding again after a 7 year lay off. Lots of Expats riding here, but no pro shops, so we buy by mail. Try this site for fun, it has a good fit kit, I tried it and for me it sized the frame a bit too small.

http://www.bsn.com/cycling/ergobike.html

I've been riding for many years and have my geometry perfect for me. For me the right size frame is when the handlebar stem length is between 100mm to 110mm, and the seat forward/backward adjustment puts the seat exactly in the middle of the seatpost.

The good shops I have been to have a machine that you sit on and it is similar to a bike you sit on, but with adjustable geometry. They set this thing up untill everything fits according to their experience and your agreement. This includes stem length seat height, bar width and everything else.

Martha
09-03-00, 04:03 PM
I too am buying a new road bike, replacing my 11 year old Bianchi road bike. I was just sized by a Serotta-certified sizer on a Serotta size-cycle. I intend to get this sizing done a second time by a different professional for confirmation and averaging. (The sizing-session fees are worth it to me to get the right bike size this time around- my 52 cm Bianchi has not been a great fit.)

Although I do not have the full written report yet, apparently I need a 50 seat tube (c-c) and a 50 top tube (c-c). I think (so far) I want to get steel again. I expected I would want titanium, thinking it would be slightly softer on my very small frame size than steel. However, from my test rides on Serotta Classique steel and Classique Ti I felt less road vibration with the steel and the Ti reminded me a little of my old harsh aluminum C-dale. (For the test ride, the two bikes were set up with my seat and comparable tires on them, although the Ti frame was 1 cm larger than the steel.) At this stage of my life (40's) I am wanting a comfortable road bike particularly for longer rides (40-100 mile). The Serotta Ti bike has been my only test ride on Ti so far.

I have located only one manufacturer that has stock frames to fit me (50 x 50), which is Waterford. They have a 50 x 50.5 and they will up or downsize the top tube length up to 1 cm at no cost on the higher end bikes, which is what I'm looking at (Reynolds 853 tubing). This is an expensive stock frame however - $1600.

I checked Terry. They only sell a 49 cm seat tube and a 52 cm seat tube. Both have small front wheels. I don't think I am interested in going down to a 49 cm and 24" front wheel. I may have to go to 650's and that would be okay I guess, since some high end wheels are available in 650 as well as 700.

Since I cannot find other manufacturers with a 50 x 50 geometry, my other option is a custom bike, such as a Serotta similar to the Classique. The stock Serotta is about $1000 and I think custom geometry is about $300.

One other factor: I intend to get the Ultegra gruppo with triple crank. This factor probably plays into the geometry since it might involve a minimum chainstay length to work well.

I do expect that no matter what bike I get, I will need a head tube extension (e.g. 20 mm).

Anybody have any suggestions for other options or things for me to consider?

One other thing: some might say the two bikes I have listed here (Serotta and Waterford) are like comparing a racier car to a Volvo. So what do I really want? I want a light bike that feels quick, that is stable at speed and not twitchy (I rest my back intermittently by riding upright with no hands), but most of all, is comfortable on long rides.

And any comments on lugged vs. welded designs? Thanks.

pat5319
09-27-00, 12:17 AM
find someone to help you who knows:

what "set back" is, if your tibias are long get lots,(LeMonds come to mind)
how to get your tibial tuberosity over your pedal axle when your crank arm is forward and parallel to the ground (slighlty forward of you time trial or sprint- slightly back if you do very long rides or climb)
when you leg is fully extended your heel should drop a bit
a "lower" bottom bracket gives you more stability and a smoother ride (a higher BB corners better but who cares unless all you do is "crits")
your overall flexibilty in large part determines you riding position
if you want a race bike "stage angles" are usually best for long rides and general use
your waist length is important (if it's short get sort top tube if long get long top tube)
you should be able to ride "no hands" fairly easily if you're going to be comfortable on it (the bike) for the long haul

Snowplug
11-05-00, 03:51 AM
Lots of riders are better off having custom frames made. One of the best cyclists I train with, rides a frame with a top tube which is 1 1/2" longer than his seat tube, due to the length of his torso and arms.

You need a good professional to measure and determine the correct sizing, or consult with someone who has the knowledge.

Snowplug

http://www.exclusive-cycling.com

Xavier
11-06-00, 04:43 PM
To end this subject.

Everyone is different and everyone has different requirements. Just because your arms are xxx long doesn't mean you have to have xxx top tube or whatever lenght.

Just to point one big case out of many - Sean Kelly.....

dvicakra
02-17-01, 07:47 AM
Surely we can agree that different kinds of riding can put the same person in very different positions (more or less upright, more or less stretched out, etc.). Everyone _is_ different. My randonneur/long distance style bikes (Singer, Rivendell) have much longer toptubes than my recreational 'racer' types (Colnago, Merckx, to pick two that differ).
But I come to ask advice (esp. from the Webmaster), not to make pronouncements:
on the Colnago, I seem to prefer the 55.5 toptube/15.8 setback with a 110 stem (tip of the saddle to center of the handlebar clamp at 54.8cm). Geometries of Carrera and Pinarello are different than Colnago, both in tt and setback. So which sizes of these bikes, for example, best compare to the Colnago?
Do we go strictly by toptube length?
The idea is to achieve the same fit.
Your respected opinions would be most interesting to me.
I am thinking particularly about purchasing a Prince or a Carrera Hercules (possibily a Giove: do you offer this Mr Cintron?)
many thanks
Dvicakra (which is Sanskrit for "two wheel")

banerjek
10-28-10, 05:44 AM
Shopping for new road bike; old Dawes recently ripped off. Many (incl Xavier) say geometry and fit are key. So where do I go from here? Pls don't send me to LBS, as I can't tell hacks from pros. I'm a 6'-1" long-mileage biker (coast to coast in my youth); age up and fitness down now, so want something light. What are the main choices in geometry, and how should I make them? Is there a reference source that deals with this? Any tips for selection? How about tips or rules or thumb for fit/adjustment? I've seen references to FitKit -- any good; available where? Thanks for any help
For someone who has ridden coast to coast, I'm a bit confused as to how you haven't figured out a way to fit things for you.

In any case, first thing you need to do is find out what kind of bike you actually like, and you probably won't do as well if you try to guess things blind. So although you specifically want to avoid the LBS, I'd still recommend going to a few and test riding a few bikes to see what you like. Don't sweat not being able to tell the hacks from the pros -- the bike you like is the right one, and in any case, you probably know more than you think.

simonaway427
10-28-10, 05:50 AM
There are soooo many factors that affect a fit. Its like asking online how you should adjust your car seat, steering wheel and your mirrors, it simply CANNOT BE DONE.

The only way you will know for sure is by going to the LBS. Yes, I get it that you're timid about the quality of the fit, but you always have the option of walking out and going somewhere else. At a minimum, they should be setting you up on a trainer with the prospective bike and go thru a myriad of adjustments.

If they tell you to stand over the bike to see if it fits, run away....run very fast.

Grumpy McTrumpy
10-28-10, 06:06 AM
wtf

http://bluntobject.files.wordpress.com/2010/01/wtf-dog.jpg

StanSeven
10-28-10, 06:06 AM
For someone who has ridden coast to coast, I'm a bit confused as to how you haven't figured out a way to fit things for you.

In any case, first thing you need to do is find out what kind of bike you actually like, and you probably won't do as well if you try to guess things blind. So although you specifically want to avoid the LBS, I'd still recommend going to a few and test riding a few bikes to see what you like. Don't sweat not being able to tell the hacks from the pros -- the bike you like is the right one, and in any case, you probably know more than you think.

You just replied to a ten year old thread. I doubt the OP is still interested :)

stien
10-28-10, 06:27 AM
This thread began out really weird...then what? How did you even dredge this one up?

unterhausen
10-28-10, 08:34 AM
locking