Bike Fit Question

[No Chain]

Anyone ever rode a frame a couple of sizes too small? My son is 19 and wants to start riding. He was fitted and told he needs a 60 cm frame. I have an older 56 cm Trek 5200. Can I make this work?

 

[boomslang]

A tough question. (Warning... anything from this point on is my opinion only and should not be taken as anything related to an actual fitting). Without going for a fit test it really depends on his body type. (I'm assuming the 60 cm frame was not from a full test). A 4 cm drop is a lot to overcome. I would suspect he might get some toe overlap and if there is any at all he is probably not suited to it. You can always pull the seat tube out farther to get the correct leg extension (up to a point) but I personally have trouble fitting bikes to my short trunk so I tend to buy them a bit smaller than a person my height (6') would normally get. I find it more comfortable with a smaller cockpit.

If your son is normally proportioned this bike is probably too small and could result in problems, or at best, a poor ride which may sour him on the sport. He could try it but if it feels at all uncomfortable, bite the bullet and get a proper size. Better a lower end bike sized correctly than an expensive wonder machine that doesn't fit.

In the end, it's all about the feel.

Hope this helps.

 

[JayKosta]

A lot depends on his goals, interest in cycling, and body configuration.

I would start with your current 56 frame and check whether the seatpost is long enough (has adequate length inside the seat tube) when raised high enough for him.
Some seatposts have a 'minimum insertion' mark - so look for that or ask here or at local dealer.

The next item is positioning the handle bars so they are in a comfortable (useable) position.
1) with hands on the flat section near the stem
2) with hands on the brake hoods
3) on the low drop section - this is much less important unless he intends to start off doing TT or Tri, etc.

The stem can probably be easily changed to make changes to the bar placement.

Getting the 'best' frame size & geometry is important for maximum comfort and efficiency - especially on long & strenuous rides.
For rides of less than about 40 miles, or less than 3 hours, it isn't as important.

My 'road bikes' are 59cm, but I also happily ride an old single speed Rollfast on 30 mile rides.
I use a long piece of iron water pipe for the seatpost...

Jay Kosta
Endwell NY USA

 

[ustabe]

My son is 19 and wants to start riding. He was fitted and told he needs a 60 cm frame. I have an older 56 cm Trek 5200. Can I make this work?

Probably not, if the fitter knows what he's talking about.

How tall is the tyke?

 

[on3m@n@rmy]

Anyone ever rode a frame a couple of sizes too small? My son is 19 and wants to start riding. He was fitted and told he needs a 60 cm frame. I have an older 56 cm Trek 5200. Can I make this work?

I'm no expert, but have a couple ideas to consider. It depends on the kind of bike we are talking about, but in the following I assume it's a road bike.
1. the shorter top tube is going to compact his torso so that breathing normally could be a problem. This might be overcome by moving the seat back and/or buying an bit extra long bar stem to stretch out his torso to a normal position.
2. I assume he has much longer legs than you or your 56 cm frame is intended for. If so, at the maximum saddle height for the seat post the leg may not be able to straighten out enough, and he could end up riding with excessive knee bend, which could damage the knees (e.g. tendenitis) especially if he does not ride high enough cadence and instead peddles using more of a power stroke.
3. the other thing about a smaller frame is the crank arm length is likely going to be a bit shorter. A guy needing a 60cm frame is likely going to need a 175mm crank arm. If the crank length on the 56cm bike is less than what he needs, this will compound the issue I mentioned in #2.

You might be able to workaround the issues in #2 and #3 by getting a longer seat post and longer crank arm, if he needs it.

I am not aware of any bike fit experts in this form, though I'm sure they exist. One forum guy who's a real gearhead (RDV4ROUBAIX) I know has built tons of wheels, and may also have some fit expertise. You could try to PM him... he may have ideas of know of someone who does.

my guess is the bike probably will not work out
good luck

 

[hfer07]

Anyone ever rode a frame a couple of sizes too small? My son is 19 and wants to start riding. He was fitted and told he needs a 60 cm frame. I have an older 56 cm Trek 5200. Can I make this work?

Absolutely no-the bike should/must fit the rider-not the other way around-and specially for a young rider whose development can be derailed & get undesirable unbalances caused by forcing muscles & posture to work wrongly due to the frame size.

 

[No Chain]

Thanks for the replies. Very helpful information.

 

[Notso Swift]

I kind of agree in the above no, BUT in real life it is more "Depends", if you can get the contact points in the right place it will be fine

Between Seat post (length and set back) and stem (length and angle) I suspect you would be OK.
It may not look cool but flipping the stem will give you a heap more flexibility
Cost of new bike versus the contact points... can be the difference between do and not do!
If he like it you can always by a new bike in 3 months


You didn't answer the height question, which would help everyone

 

[Indurain]

The pro's ride bike frames too small for them all the time. The most important measurement is the top tube length. Not the height. People stuff this up all the time.

What you also need to consider is, did he measure up with a standard frame or a compact frame? If standard you can use a smaller compact frame. In other words a 56cm compact is equal to a 58cm or more standard.

Try him on the 56cm with a seatpost with 2 to 2.5cm setback and a slightly longer stem. See how it goes. As long as the stem isn't too high needing heaps of spacers or too low making riding uncomfortable.

good luck. Experimenting with position is the only way. I got sized up and feel my frame is 2cm to big (on the top tube). As such I now need to use a 100mm stem.

 

[luckyboy]

Have a similar query to this.

Found a frame I like (regular frame) that has these measurements: Top tube C-C= 55cm, Seatpost tube C-C= 55cm, Seatpost tube C-T= 57cm.

My Competitive Cyclist fit (can't afford £150+ for a proper fit) says my measurements should be: Top tube C-C= 56.6 - 57.0cm, Seatpost tube C-C= 56.7 - 57.2cm, Seatpost Tube C-T = 58.4 - 58.9cm.

The bike I'm currently riding (compact frame) has these measurements: Top tube C-C= 55cm, Seatpost tube C-C= 47cm, Seatpost tube C-T= 49.5cm.

My current bike is a bit small (my arms feel a bit cramped/the reach isn't enough).

I guess I should wait to find a frame that's a big bigger?

 

[karlboss]

Agree with notsoswift, ideally the frame would fit, but in the event it doesn't get the contact points right using seatpost, and stem. Saddle position right first. From 56-60 it wouldn't surprise me to see that a stem and seatpost that will do the job with length and setback. It really wouldn't surprise me if the recommendation of 60cm was wrong, though you said bike fitting, so it's probably right. Once the contact points are right, if the wrong frame size is used there will only differences in handling, you can adapt to those.

 

[ultimobici]

The pro's ride bike frames too small for them all the time. The most important measurement is the top tube length. Not the height. People stuff this up all the time.

What you also need to consider is, did he measure up with a standard frame or a compact frame? If standard you can use a smaller compact frame. In other words a 56cm compact is equal to a 58cm or more standard.

Try him on the 56cm with a seatpost with 2 to 2.5cm setback and a slightly longer stem. See how it goes. As long as the stem isn't too high needing heaps of spacers or too low making riding uncomfortable.

good luck. Experimenting with position is the only way. I got sized up and feel my frame is 2cm to big (on the top tube). As such I now need to use a 100mm stem.

Problem with using a frame that is a couple of sizes too small is that the drop to the bars may be too great. Many pros use the smaller frame to get more drop than they might be able to on a "correctly" sized frame. Hence the number of extra long stems on pro bikes to compensate for the shorter op tube.

To put a young rider on a smaller frame may induce injury from poor posture too.

 

[dsut4392]

Have a similar query to this.

Found a frame I like (regular frame) that has these measurements: Top tube C-C= 55cm, Seatpost tube C-C= 55cm, Seatpost tube C-T= 57cm.

My Competitive Cyclist fit (can't afford £150+ for a proper fit) says my measurements should be: Top tube C-C= 56.6 - 57.0cm, Seatpost tube C-C= 56.7 - 57.2cm, Seatpost Tube C-T = 58.4 - 58.9cm.

The bike I'm currently riding (compact frame) has these measurements: Top tube C-C= 55cm, Seatpost tube C-C= 47cm, Seatpost tube C-T= 49.5cm.

My current bike is a bit small (my arms feel a bit cramped/the reach isn't enough).

I guess I should wait to find a frame that's a big bigger?

Done with due care and attention, the Competitive Cyclist fit is probably a good bet - it worked for me.

You could probably make the smaller frame work for you with setback seat post and slightly longer stem, but could equally well make your existing frame work better for you with the same tweaks (assuming there's nothing wrong with it). I'd wait for a frame the right size to come up if I were you as you'll probably regret buying another bike that doesn't feel right..

 

[luckyboy]

Yeah I think maybe waiting is the best. It's very tempting though.

A traditional geometry 55cm frame would surely be less cramped reach-wise than a compact 55cm?
The seatpost angle on the compact frame I have now is actually less than the traditional frame I want, so the same toptube length without it sloping would allow more room, no?

edit: Oh toptube length on the frame I want is actually 55.6cm not 55cm