Go Back  Bike Forums > Bike Forums > General Cycling Discussion
Reload this Page >

Question on Road Bike Fit

Notices
General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

Question on Road Bike Fit

Old 01-06-21, 08:06 AM
  #1  
LeSexyFishorse
Senior Member
Thread Starter
 
Join Date: Nov 2020
Posts: 67
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 37 Post(s)
Liked 13 Times in 12 Posts
Question on Road Bike Fit

How substantial is a few mm when talking about road bike fit? I have an opportunity to get a nice Road bike for cheap but the frame measurement from BB to top is 51mm vs what is 56mm+ which is recommended for me. How negative effects will you get from that kind of a difference? Are they something you can overcome or does it make the bike a "hard no" on the buy?
LeSexyFishorse is offline  
Old 01-06-21, 10:14 AM
  #2  
DaveSSS 
Senior Member
 
Join Date: Sep 2008
Location: Loveland, CO
Posts: 6,211

Bikes: TWO Cinelli superstar disc with SRAM Force AXS

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 575 Post(s)
Liked 249 Times in 201 Posts
I assume you're referring to the stack height? If so, those values would have to be in centimeters, not millimeters. 5cm is a big difference, since the most common change between frame sizes is 2cm. The reach dimension will not be the same either. I just bought two new frames that are the smallest I've ever owned, but I know exactly what stack and reach l want, so I knew exactly what my new setup would be. I went from a 527mm stack to a 509mm stack. I used 15mm of spacer under the stem and the same -17 degree stem, in a 10mm longer length, to correct for a shorter reach. The stack is only 3mm lower than my old frames.

Last edited by DaveSSS; 01-06-21 at 10:18 AM.
DaveSSS is offline  
Old 01-06-21, 10:24 AM
  #3  
wphamilton
Senior Member
 
wphamilton's Avatar
 
Join Date: Apr 2011
Location: Alpharetta, GA
Posts: 15,177

Bikes: Nashbar Road

Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 2869 Post(s)
Liked 260 Times in 173 Posts
A few mm is trivial, representing a small change in the positioning of your torso and arms.

Our tolerance for these slight variations appears to vary among individuals. I wouldn't think twice about a 5mm higher handlebar, nor a couple of mm reach either way. For others it's a deal killer.

If you mean frame size, 51 vs 55 CM as Dave suggested, that's out of the question. The bike won't ever fit and you'd regret it.
wphamilton is offline  
Likes For wphamilton:
Old 01-06-21, 10:29 AM
  #4  
jadocs
Senior Member
 
jadocs's Avatar
 
Join Date: Jul 2018
Location: USA
Posts: 2,127

Bikes: Ti, Mn Cr Ni Mo Nb, Al, C

Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 906 Post(s)
Liked 496 Times in 333 Posts
Sounds like cm to me and not mm.

Also sounds like you are referring to seat tube height. Meaning this is technically a 51cm frame and you should be on a 56cm frame.

Is this a standard geometry frame?
jadocs is offline  
Likes For jadocs:
Old 01-06-21, 10:58 AM
  #5  
Moisture
Banned.
 
Join Date: Oct 2020
Posts: 766
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 515 Post(s)
Liked 87 Times in 71 Posts
No. Don't buy it
Moisture is offline  
Old 01-06-21, 11:00 AM
  #6  
LeSexyFishorse
Senior Member
Thread Starter
 
Join Date: Nov 2020
Posts: 67
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 37 Post(s)
Liked 13 Times in 12 Posts
Originally Posted by jadocs View Post
Sounds like cm to me and not mm.

Also sounds like you are referring to seat tube height. Meaning this is technically a 51cm frame and you should be on a 56cm frame.

Is this a standard geometry frame?
Originally Posted by wphamilton View Post
A few mm is trivial, representing a small change in the positioning of your torso and arms.

Our tolerance for these slight variations appears to vary among individuals. I wouldn't think twice about a 5mm higher handlebar, nor a couple of mm reach either way. For others it's a deal killer.

If you mean frame size, 51 vs 55 CM as Dave suggested, that's out of the question. The bike won't ever fit and you'd regret it.
Originally Posted by DaveSSS View Post
I assume you're referring to the stack height? If so, those values would have to be in centimeters, not millimeters. 5cm is a big difference, since the most common change between frame sizes is 2cm. The reach dimension will not be the same either. I just bought two new frames that are the smallest I've ever owned, but I know exactly what stack and reach l want, so I knew exactly what my new setup would be. I went from a 527mm stack to a 509mm stack. I used 15mm of spacer under the stem and the same -17 degree stem, in a 10mm longer length, to correct for a shorter reach. The stack is only 3mm lower than my old frames.
I mean the distance from center of the BB to the top of the seat tube. Sorry if that was not clear. I am also referring to a classic road bike type frame if that helps. Sorry I think the mm was a translation error, should be cm I think. They recommended a 56 for me when I went for a bike fit which I understand is a Medium frame?
LeSexyFishorse is offline  
Old 01-06-21, 11:03 AM
  #7  
jadocs
Senior Member
 
jadocs's Avatar
 
Join Date: Jul 2018
Location: USA
Posts: 2,127

Bikes: Ti, Mn Cr Ni Mo Nb, Al, C

Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 906 Post(s)
Liked 496 Times in 333 Posts
Originally Posted by LeSexyFishorse View Post
I mean the distance from center of the BB to the top of the seat tube. Sorry if that was not clear. I am also referring to a classic road bike type frame if that helps. Sorry I think the mm was a translation error, should be cm I think. They recommended a 56 for me when I went for a bike fit which I understand is a Medium frame?
If a fitter told you that you need a 56cm frame, a 51cm frame will be too small for you. It's not just about how high the seat tube is. Smaller frames have less reach and you will be cramped.
jadocs is offline  
Likes For jadocs:
Old 01-06-21, 11:07 AM
  #8  
Barry2 
LRP=HR
 
Join Date: Sep 2019
Location: SF Bay Area
Posts: 710

Bikes: 79 Holdsworth Special, 93 C-dale MT3000 Tandem, 96 C-dale F700CAD3, Two Cervelo R3's 2011 & 2018, JustGo Runt, Ridley Oval, Kickr Bike 8-)

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 272 Post(s)
Liked 225 Times in 155 Posts
Originally Posted by LeSexyFishorse View Post
How substantial is a few mm when talking about road bike fit?
For the past 14 months I've been riding a 61cm Cervelo. I had to replace the seatpost with a zero setback and replace the stem with a shorter one to get a more reasonable reach.
With these changes, I've been able to comfortably get 2,000+ miles in 2020.

However, I've recently replaced the bike with a 58cm Cervelo. I had to in the end.

You can modify a larger bike to get close to your needed dimensions (assuming you can standover the top tube), but it is really not the best solution.

Barry
Barry2 is offline  
Old 01-06-21, 11:14 AM
  #9  
alcjphil
Senior Member
 
alcjphil's Avatar
 
Join Date: Jun 2002
Location: Montreal, Quebec
Posts: 4,189
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 1056 Post(s)
Liked 420 Times in 286 Posts
The difference between 51 cm and 56 cm is 5 cm which translates to just about 2 inches. That is a huge difference in frame size. However, other frame dimensions are equally important. Top tube length, for example is also very important. A 56 cm frame with a 57 cm top tube will fit very differently than a 56 cm frame with a 55 cm top tube
alcjphil is offline  
Likes For alcjphil:
Old 01-06-21, 12:00 PM
  #10  
chaadster
Thread Killer
 
Join Date: Aug 2008
Location: Ann Arbor, MI
Posts: 9,895

Bikes: '15 Kinesis Racelight 4S, '76 Motebecane Gran Jubile, '17 Dedacciai Gladiatore2, '12 Breezer Venturi, '09 Dahon Mariner, '05 Novara Big Buzz, '12 Mercier Nano, '95 DeKerf Team SL, '19 Tern Rally, ‘21 Breezer Doppler Cafe+, ‘19 T Lab X3

Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 1294 Post(s)
Liked 281 Times in 177 Posts
Let me point out to the OP that the frame size recommendation given by their fitter is almost certainly a center-to-center measurement (c-c), i.e. from center of the bottom bracket to center of the top tube. Center-to-top (of seat tube) is pretty meaningless unless talking about sizes of frames all made in the same way, as in the same model from the same make.

As has been pointed out, notably by alcjphil , there are much more relevant measurements to use when shopping across brands (and even models). I’d suggest talking to this “fitter” and getting something useful, like stack and reach measurements, if in fact they can even provide them. I suspect that no good fitter would send a client out in search of a 56cm frame these days; the variations in frame design are far to great to give such a simple number any helpful significance.
chaadster is offline  
Likes For chaadster:
Old 01-06-21, 08:20 PM
  #11  
LeSexyFishorse
Senior Member
Thread Starter
 
Join Date: Nov 2020
Posts: 67
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 37 Post(s)
Liked 13 Times in 12 Posts
Originally Posted by jadocs View Post
If a fitter told you that you need a 56cm frame, a 51cm frame will be too small for you. It's not just about how high the seat tube is. Smaller frames have less reach and you will be cramped.
Originally Posted by Barry2 View Post
For the past 14 months I've been riding a 61cm Cervelo. I had to replace the seatpost with a zero setback and replace the stem with a shorter one to get a more reasonable reach.
With these changes, I've been able to comfortably get 2,000+ miles in 2020.

However, I've recently replaced the bike with a 58cm Cervelo. I had to in the end.

You can modify a larger bike to get close to your needed dimensions (assuming you can standover the top tube), but it is really not the best solution.

Barry
So if I understand correctly, too small a frame will make me feel cramped when riding? Is this something I can remedy safely? Could I not extend the handlebars and raise the seat to get a better feel? Again talking about the 51 vs 56cm limit here. How bad of a compromise would it be? I guess what I am trying to see is if I can live with a smaller frame for a bike I really really like or if I should just live with the heartbreak and let her go. 2 Inches doesn't seem like much to me but I suppose I don't have the experience to properly quantify the effect.
LeSexyFishorse is offline  
Old 01-06-21, 08:23 PM
  #12  
LeSexyFishorse
Senior Member
Thread Starter
 
Join Date: Nov 2020
Posts: 67
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 37 Post(s)
Liked 13 Times in 12 Posts
I think they might have been referring to center to top of seat tube since I told them I was looking for a vintage road bike frame.
LeSexyFishorse is offline  
Old 01-06-21, 08:30 PM
  #13  
jon c. 
Senior Member
 
Join Date: Mar 2012
Location: Tallahassee, FL
Posts: 4,064
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 1125 Post(s)
Likes: 0
Liked 264 Times in 153 Posts
That's too large a difference. I ride a 54 and wouldn't consider trying to make a 51 fit.
jon c. is offline  
Old 01-06-21, 08:30 PM
  #14  
Moisture
Banned.
 
Join Date: Oct 2020
Posts: 766
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 515 Post(s)
Liked 87 Times in 71 Posts
You need to understand more about what stack and reach/ top tube length is right for you in order to answer your question re living with a smaller frame
Moisture is offline  
Old 01-06-21, 08:32 PM
  #15  
Barry2 
LRP=HR
 
Join Date: Sep 2019
Location: SF Bay Area
Posts: 710

Bikes: 79 Holdsworth Special, 93 C-dale MT3000 Tandem, 96 C-dale F700CAD3, Two Cervelo R3's 2011 & 2018, JustGo Runt, Ridley Oval, Kickr Bike 8-)

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 272 Post(s)
Liked 225 Times in 155 Posts
Originally Posted by LeSexyFishorse View Post
So if I understand correctly, too small a frame will make me feel cramped when riding? Is this something I can remedy safely? Could I not extend the handlebars and raise the seat to get a better feel? Again talking about the 51 vs 56cm limit here. How bad of a compromise would it be?
For a trip to the shops, 5cm dont matter.
But for 2,000 miles a year I purchased one 3cm smaller...... yes 1 1/4 smaller.

So you will need to make the decision for your age, intended use, and wallet size.


Barry
Barry2 is offline  
Old 01-06-21, 08:59 PM
  #16  
LeSexyFishorse
Senior Member
Thread Starter
 
Join Date: Nov 2020
Posts: 67
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 37 Post(s)
Liked 13 Times in 12 Posts
Unfortunately, I dont know if I can get stack and reach numbers since its an auction site.
LeSexyFishorse is offline  
Old 01-06-21, 09:04 PM
  #17  
LeSexyFishorse
Senior Member
Thread Starter
 
Join Date: Nov 2020
Posts: 67
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 37 Post(s)
Liked 13 Times in 12 Posts
Originally Posted by Barry2 View Post
For a trip to the shops, 5cm dont matter.
But for 2,000 miles a year I purchased one 3cm smaller...... yes 1 1/4 smaller.

So you will need to make the decision for your age, intended use, and wallet size.


Barry
How did you do with your 3cm smaller frame? I am in my 30's, physically fit, I intend to do some fast riding for exercise but no serious rides allowed at the moment due to the lockdowns. Unlikely I will go further than 20-30 miles per ride I suppose. Trying to get this one cheap which is why I am buying at auction. This makes the frames that I like for this price even rarer at auction. They do happen and I dont mind waiting if the downsides of a small frame of this degree are significant. What do you think?
LeSexyFishorse is offline  
Old 01-06-21, 09:13 PM
  #18  
Bigbus
Senior Member
 
Bigbus's Avatar
 
Join Date: Mar 2018
Location: On the Move
Posts: 892

Bikes: Giant Road Bike & Giant MTB $ Fuji Road Bike

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 279 Post(s)
Liked 190 Times in 143 Posts
Hey Lesexy, no matter how high you raise the seat and slide it back plus push out the handlebars, you're going to feel like you're all over that bike and not in a good way. The human body can adapt to a lot, but I doubt if that bike will ever feel right for you. With that said, I know how you're feeling and you really want to make it work. Good luck with your decision,
Bigbus is offline  
Old 01-06-21, 10:36 PM
  #19  
veganbikes
Clark W. Griswold
 
Join Date: Mar 2014
Location: ,location, location
Posts: 7,695

Bikes: Foundry Chilkoot Ti W/Ultegra Di2, Salsa Timberjack Ti, Cinelli Mash Work RandoCross Fun Time Machine, 1x9 XT Parts Hybrid, Co-Motion Cascadia, Specialized Langster, Phil Wood Apple VeloXS Frame (w/DA 7400), Cilo Road Frame, Proteus frame, Ti 26 MTB

Mentioned: 35 Post(s)
Tagged: 0 Thread(s)
Quoted: 2020 Post(s)
Liked 925 Times in 646 Posts
Get a bike that fits. Bikes that don't fit are not fun and not worth it. Yes you can find stories of people doing and see them but it just isn't comfortable and your fitter wouldn't be happy seeing you on a bike that is so ill fitting.

Pro riders will sometimes opt for a smaller frame for aerodynamic gains but they are pro riders who train hard and ride a lot, a lot and dedicate themselves to getting the best position to win and also to handle the bike as well as you can. Plus they have doctors, masseuses, fitters and mechanics who can get it all done and make it work. We are mere mortals and don't quite have all of that nor should we strive for that unless we want to be professionals. Other than that I wouldn't want to work that hard to bike to not win, I would want to enjoy more.

A good deal is only a good deal if it is a good deal. I could buy a bike to resell or take parts off of or something like that but buying a bike that doesn't fit with the intention of riding it, isn't a good deal for sure. I have seen a lot of bikes in my time that are awesome bikes at decent prices but if it doesn't fit I don't buy it as it is not a good deal for me. I don't need another wall hanger that I didn't ride and can't really ride with any sort of comfort, I want bikes I can ride and enjoy.
veganbikes is offline  
Likes For veganbikes:
Old 01-06-21, 11:11 PM
  #20  
chaadster
Thread Killer
 
Join Date: Aug 2008
Location: Ann Arbor, MI
Posts: 9,895

Bikes: '15 Kinesis Racelight 4S, '76 Motebecane Gran Jubile, '17 Dedacciai Gladiatore2, '12 Breezer Venturi, '09 Dahon Mariner, '05 Novara Big Buzz, '12 Mercier Nano, '95 DeKerf Team SL, '19 Tern Rally, ‘21 Breezer Doppler Cafe+, ‘19 T Lab X3

Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 1294 Post(s)
Liked 281 Times in 177 Posts
Originally Posted by LeSexyFishorse View Post
I think they might have been referring to center to top of seat tube since I told them I was looking for a vintage road bike frame.
The mid-90s were 25 years ago, and by that time, the adoption of TIG welding, new tubing shapes, and the compact geometry revolution were already happening and changing how frames were designed and fit, so depending on what the definition of vintage is, I nonetheless think its rather ridiculous that a serious fitter would spit out a frame size recco based on seat tube C-T. I still think you should be putting this question to them, and getting a proper explanation for their sizing suggestion.

But, if we assume you y were talking about racing bikes from the 60s, 70s, and 80s, then yeah, dropping to a 51cm from a 56cm proper fit is gonna be very small, cramped, and a generally poor selection. Id advise against it, for sure.
chaadster is offline  
Old 01-07-21, 01:56 AM
  #21  
LeSexyFishorse
Senior Member
Thread Starter
 
Join Date: Nov 2020
Posts: 67
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 37 Post(s)
Liked 13 Times in 12 Posts
Yeah I have decided to take more experienced advice and pass on the 51. Its a shame because I really wanted it but I suppose if I would just end up hating the feel because it doesnt fit it would be a waste anyway. I guess I will just be patient. Thank you for all your insights guys, really appreciate it.
LeSexyFishorse is offline  
Likes For LeSexyFishorse:
Old 01-07-21, 07:14 AM
  #22  
chaadster
Thread Killer
 
Join Date: Aug 2008
Location: Ann Arbor, MI
Posts: 9,895

Bikes: '15 Kinesis Racelight 4S, '76 Motebecane Gran Jubile, '17 Dedacciai Gladiatore2, '12 Breezer Venturi, '09 Dahon Mariner, '05 Novara Big Buzz, '12 Mercier Nano, '95 DeKerf Team SL, '19 Tern Rally, ‘21 Breezer Doppler Cafe+, ‘19 T Lab X3

Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 1294 Post(s)
Liked 281 Times in 177 Posts
Originally Posted by LeSexyFishorse View Post
Yeah I have decided to take more experienced advice and pass on the 51. Its a shame because I really wanted it but I suppose if I would just end up hating the feel because it doesnt fit it would be a waste anyway. I guess I will just be patient. Thank you for all your insights guys, really appreciate it.
I understand your frustration, but your patience will be rewarded! There are good supplies of vintage bikes, covering at least three decades of production, on eBay, Facebook Marketplace, and Craiglistlists across the country, so undoubtedly youll find exactly what you want and need.
chaadster is offline  
Old 01-07-21, 09:12 AM
  #23  
Sy Reene
Advocatus Diaboli
 
Sy Reene's Avatar
 
Join Date: Feb 2015
Location: Wherever I am
Posts: 6,582

Bikes: Merlin Cyrene, Nashbar steel CX

Mentioned: 11 Post(s)
Tagged: 1 Thread(s)
Quoted: 3398 Post(s)
Liked 660 Times in 450 Posts
Originally Posted by LeSexyFishorse View Post
I think they might have been referring to center to top of seat tube since I told them I was looking for a vintage road bike frame.
You also have to be wary that whoever's selling the '51cm' measured frame, whether they just measured the actual distance from the BB to the top of the seat tube. Of course a bike with a sloping top tube will have a much shorter actual seat tube, while you're fitter was likely referencing a size based on a horizontal top tube. IOW, there is a possibility that a sloping top tubed bike might have an actual measurement of 51cm if the seller is just measuring with a yardstick, but be equivalent to eg. a nominally labelled 56cm bike.
Sy Reene is offline  
Old 01-08-21, 12:58 AM
  #24  
Camilo
Senior Member
 
Join Date: Apr 2007
Posts: 4,829
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 347 Post(s)
Liked 131 Times in 86 Posts
Originally Posted by jadocs View Post
If a fitter told you that you need a 56cm frame, a 51cm frame will be too small for you. It's not just about how high the seat tube is. Smaller frames have less reach and you will be cramped.
And a shorter head tube which will - stem height being equal - cause a larger saddle to bar drop because of that and the fact that because of the need to extend your seat post higher because of the shorter seat tube. You might be able to make up the difference in reach (shorter top tube) and handlebar drop with a taller and longer stem, but maybe not.

Like others have said. Without knowing the other geometry factors, its much more than likely that a 51 cm frame is quite a bit too small for you.

Study up on frame geometry and make some fit measurements on your current bike to get familiar with this stuff. Buy a frame that is within normal stem height and reach of being able to mimic your current fit (assuming you're happy with it).
Camilo is offline  
Old 01-08-21, 10:49 AM
  #25  
Moisture
Banned.
 
Join Date: Oct 2020
Posts: 766
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 515 Post(s)
Liked 87 Times in 71 Posts
Should be able to find stack and reach dimensions regarding most bikes if you search up the name of bike and look for a geomtery chart.

You being 5'11, should not go any smaller than 56cm. Unless your legsnare very short you can go 58.
Moisture is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.