Go Back  Bike Forums > Bike Forums > Fitting Your Bike
Reload this Page >

Let me get this straight: <52cm frame + 700C wheels = problems?

Notices
Fitting Your Bike Are you confused about how you should fit a bike to your particular body dimensions? Have you been reading, found the terms Merxx or French Fit, and don’t know what you need? Every style of riding is different- in how you fit the bike to you, and the sizing of the bike itself. It’s more than just measuring your height, reach and inseam. With the help of Bike Fitting, you’ll be able to find the right fit for your frame size, style of riding, and your particular dimensions. Here ya’ go…..the location for everything fit related.

Let me get this straight: <52cm frame + 700C wheels = problems?

Old 06-08-22, 01:25 AM
  #1  
Junior Member
Thread Starter
 
Krov9's Avatar
 
Join Date: Mar 2021
Location: Helsinki, Finland
Posts: 140
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 58 Post(s)
Liked 45 Times in 25 Posts
Let me get this straight: <52cm frame + 700C wheels = problems?

So I (5'3" / 160 cm) have been looking for bike to do some short tours and commutes with, for starters, and on a budget.

Is the dominant understanding that you simply can't find a well-proportioned frame with 700c wheels in sizes 52cm and under?

What I've gathered from reading what Georgena Terry and others have said about designing bikes for riders my height and under (plus looking at dozens of x-small road bikes on the used market) is that if you want to cram 700c wheels on a "level toptube" diamond frame with a seat tube of ~52cm or under, it requires compromises with the seat tube and head tube angles, meaning that the seat tube will be at a near vertical angle whereas the head tube angle will be notably slack? This seems to apply to at least most of pre-2000 road frames in the smallest of sizes.

Now, from theory to practice, I found an 80's road frame for cheap since the previous owner complained about the handling. I'm building it up, as an experiment, with 650B wheels and 38mm tires that it clears surprisingly fine.

With that configuration, I'm just barely able to straddle the top tube (=standing over it the bike slightly tilted or on my toes). Also numerous size calculators suggest that with ~70cm cycling inseam I'd need something smaller than 50cm, with answers ranging from 45 cm to 48 cm. I haven't been able to test ride my "experiment" yet, because I'm still waiting for some 155mm cranks in the mail to compensate for a meager 250mm of bottom bracket height after the 650B conversion. Let's see how that goes.

Now I've also got my eyes on a good deal on a sloped toptube frame for 650c wheels, but I'm concerned that with 38cm seat tube and 47,5cm (actual, not "virtual"?) toptube it might be even too small for me?

Since 650c wheels and tires in all but the skinniest junior training sizes are hard to come by, I'd perhaps consider mtb-sized 26" (559mm) wheels with >1" slicks for that frame...

I'd like to hear how this all sounds to you, and which route you might suggest me going?
Krov9 is offline  
Old 06-08-22, 05:42 AM
  #2  
I am potato.
 
base2's Avatar
 
Join Date: Jun 2015
Location: Pacific Northwest
Posts: 3,165

Bikes: Only precision built, custom high performance elitist machines of the highest caliber. 🍆

Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 1813 Post(s)
Liked 1,678 Times in 961 Posts
Your bottom bracket seems low to me. I'd be concerned about pedal strikes even with the shorter crank arms.

A taller wheel/tire size would bring everything up.
So would a fork with a longer axle to crown measurement. But, I gather your stand over height doesn't allow for much of either.

Something about this whole thing seems "off" to me. Can you post pictures? Rims lining up with brakes would be a sure-fire way of getting in the ballpark WRT wheel size & Terrys aren't known for toe overlap or other fitment issues. IOW: She knew what she was doing....Are you sure this is the proper OEM fork?

I just feel there is more to this somewhere.

What is this '"80's road frame you found for cheap?"

I would default to these guys being an authority on the matter.

Last edited by base2; 06-08-22 at 06:00 AM.
base2 is offline  
Old 06-09-22, 05:00 AM
  #3  
Junior Member
Thread Starter
 
Krov9's Avatar
 
Join Date: Mar 2021
Location: Helsinki, Finland
Posts: 140
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 58 Post(s)
Liked 45 Times in 25 Posts
Originally Posted by base2
Your bottom bracket seems low to me. I'd be concerned about pedal strikes even with the shorter crank arms.
I know right! The weird thing is that with the common 23x700c race tyres the BB spindle would sit only 4mm higher, at exactly 10" / 25,4 mm!

Originally Posted by base2
Something about this whole thing seems "off" to me. Can you post pictures? Rims lining up with brakes would be a sure-fire way of getting in the ballpark WRT wheel size & Terrys aren't known for toe overlap or other fitment issues. IOW: She knew what she was doing....Are you sure this is the proper OEM fork?

I just feel there is more to this somewhere.

What is this '"80's road frame you found for cheap?"
I don't think I mentioned anything about brakes or forks so I struggle to follow you here... In terms of brake reach, it's pretty reasonable at 50mm with the said 650B wheels, and I'm confident this is the original fork for this frame. It's a mid-80's low end Rossin "Infinity" road bike in the smallest size, 50cm. I've only just run a mockup configuration, and as of now I don't have a good pic of the bare frameset.

As for the other candidate, it looks like this




With the little info I have (while waiting for the seller to respond to my questions) I tried to make a geometry model, had to guess-timate most of the measurements but here goes:
So what I know is head tube 10 cm; seat tube top to center 40,5 cm; toptube 47,5 cm (which for this model I assumed is measured from the actual, sloped toptube, not the virtual horizontal line which would close in to 50 cm, but OOH I have long arms&torso in relation to my lower half)
322mm radius is for 559 wheels with inflated 42mm tires.
Krov9 is offline  
Old 06-09-22, 05:57 AM
  #4  
Senior Member
 
Join Date: Oct 2008
Location: Northern NY...Brownville
Posts: 2,592

Bikes: Specialized Aethos, Specialized Diverge Comp E5

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 249 Post(s)
Liked 473 Times in 278 Posts
I'm 5'4" and ride a 52cm Aethos with 700c wheels...works great.
I've also ridden 49cm frame with 700c wheels...no problems at all
Kai Winters is offline  
Old 06-09-22, 06:52 AM
  #5  
I am potato.
 
base2's Avatar
 
Join Date: Jun 2015
Location: Pacific Northwest
Posts: 3,165

Bikes: Only precision built, custom high performance elitist machines of the highest caliber. 🍆

Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 1813 Post(s)
Liked 1,678 Times in 961 Posts
Originally Posted by Krov9
I don't think I mentioned anything about brakes or forks so I struggle to follow you here... In terms of brake reach, it's pretty reasonable at 50mm with the said 650B wheels, and I'm confident this is the original fork for this frame. It's a mid-80's low end Rossin "Infinity" road bike in the smallest size, 50cm. I've only just run a mockup configuration, and as of now I don't have a good pic of the bare frameset.
I only mentioned the brake reach as a means of guesstimating an appropriate wheel size. I work in a Co-Op & regularly see all manner of combinations of parts. The most recent was a 700c Electra Townie with a 20inch (406) BMX coaster brake wheel installed & a 7 speed cassette installed where the single speed cog ought to be. You probably guessed it; the derailleur was indeed blown out from coaster brake application & the frame tweaked from being tightened down on a 120mm OLD.

Anywho. If you're confident everything lines up as it should, then all is good as far as I can see.
__________________
I shouldn't have to "make myself more visible;" Drivers should just stop running people over.

Car dependency is a tax.
base2 is offline  
Old 06-10-22, 06:41 AM
  #6  
Junior Member
Thread Starter
 
Krov9's Avatar
 
Join Date: Mar 2021
Location: Helsinki, Finland
Posts: 140
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 58 Post(s)
Liked 45 Times in 25 Posts
Wow, sounds like someone tried to construct their own "minivelo" without knowing what they were doing!

The 650B mockup makes the wheelbase appear quite long, I'll see how that will affect the handling.

Sub-10" BB height (250mm) sounded low for me too, but I just read from Dave Moulton's blog about his 1953 TT machine having only 9.25 inches (23.5cm)! So I guess, with the shorter cranks and watching out at tight corners I should do fine.

I'm really intrigued with the rusty NOS frame pictured above despite sloped top tubes not being exactly my thing, aesthetically. The seller told me that even the virtual top tube would be under 50mm, and that the frame should clear 28x650c tires, no wider - so no hope for 40mm 26" I guess?
Krov9 is offline  
Old 06-10-22, 10:36 AM
  #7  
Bikeable
 
headwind15's Avatar
 
Join Date: Jan 2011
Posts: 326
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Likes: 0
Liked 104 Times in 73 Posts
I have been a frame builder for the last 20plus years and am an small frame expert. If your cad pic is accurate as far as seat height, I would recommend a shorter seat tube. Face it you are really short. To have a frame with the right per-portions, you should strive to have even more seat post showing, than your head tube size. If you don't do it, it look like you have this little stump sticking out of the frame. I am 5'-6", and used to ride a 52 cm for many years. so sure, I could ride some huge frame, but so much nicer to have one with more stand over. so, my bikes tend to have 10cm/ 4" shorter seat tubes, (42 cm), I even have an old Bianchi with a 38cm seat tube. I think you should go with less than 36 cm, without considering anything bigger. On BB height: It really depends on your riding style/ how much it bothers you about forgetting and pedal thru a corner and dig a pedal in in and potentially crash/ get scrapped up. I used to race a lot and when riding a lot of Criteriums with a 10.5 BB, I would occasionally strike a pedal. I tried racing on a bike with a 10.5 BB. Instead of striking a pedal, it would really dig in. I would be lucky to keep it upright. (not fun). Plenty of people don't pedal thru corners/ have low bb's. 10.5 is a really common standard, for a bike with 700c/ wheels 170 mm crank arms.
headwind15 is offline  
Likes For headwind15:
Old 06-12-22, 12:30 PM
  #8  
Junior Member
Thread Starter
 
Krov9's Avatar
 
Join Date: Mar 2021
Location: Helsinki, Finland
Posts: 140
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 58 Post(s)
Liked 45 Times in 25 Posts
Originally Posted by headwind15
I would recommend a shorter seat tube. Face it you are really short. To have a frame with the right per-portions, you should strive to have even more seat post showing, than your head tube size. If you don't do it, it look like you have this little stump sticking out of the frame. I am 5'-6", and used to ride a 52 cm for many years. so sure, I could ride some huge frame, but so much nicer to have one with more stand over. so, my bikes tend to have 10cm/ 4" shorter seat tubes, (42 cm), I even have an old Bianchi with a 38cm seat tube. I think you should go with less than 36 cm, without considering anything bigger.
Interesting! Most simple calculators of the kind where you just input your height/cycling inseam (mine are 160cm / 5'3" and 70 cm) suggest me sizes ranging from 47 to 51cm, and given that these come from a classic, level top tube road geometry point of view, that would translate to having 10 cm more of seat tube than you suggest!

On the other hand, I you are right, then that sweet 38cm seat tube, 47,5 cm top tube 650C NOS Colmbus SL frame I found on eBay might just do the trick?

As I've got most of the parts already at hand, I'm going to build up the old 50cm Rossin just to get to ride and see how that feels.

Considering tecnhology etc. I find myself drawn towards the C&V segment, but if I bought a say, post -1980's frame, I wouldn't have any problem per se fitting it with modern components. It just appears that I might be able to get better weight, build quality etc. for the price by going with older standards and used stuff...
Krov9 is offline  
Old 06-12-22, 04:26 PM
  #9  
Bikeable
 
headwind15's Avatar
 
Join Date: Jan 2011
Posts: 326
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Likes: 0
Liked 104 Times in 73 Posts
You have a huge advantage that you have the Rossin to try out. I would guess that the Rossin has a 51 or 52 cm top tube. If you really want a 47.5 top tube and don't want foot overlap, yea, you will need to think smaller wheels.
headwind15 is offline  
Likes For headwind15:
Old 06-14-22, 11:54 AM
  #10  
Junior Member
Thread Starter
 
Krov9's Avatar
 
Join Date: Mar 2021
Location: Helsinki, Finland
Posts: 140
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 58 Post(s)
Liked 45 Times in 25 Posts
Originally Posted by headwind15
You have a huge advantage that you have the Rossin to try out. I would guess that the Rossin has a 51 or 52 cm top tube. If you really want a 47.5 top tube and don't want foot overlap, yea, you will need to think smaller wheels.
Yeah, that's how I feel too. I'll try my best to build and adjust it, and only after that decide if I'd be better of looking for another frames. I just got the cranks today, and I'm about to take some pictures of the Rossin in said mockup configuration to clarify the proportions. I should probably also measure it's top tube for reference.

I'm not claiming to know much about bike sizing or fitting, so I have no idea wether a 47 or 52 cm toptube would be better for me. I would guess handlebar and stem reach also play a part here? I've never had a bike with drops, so I'm thinking of a swept back "comfort bar" with a modest rise, or maybe one of those moustache bars with frop levers at the bends, which would stretch out the position quite a lot compared to say, north roads, right?
Krov9 is offline  
Old 06-16-22, 12:13 PM
  #11  
Senior Member
 
icemilkcoffee's Avatar
 
Join Date: Aug 2009
Posts: 2,487
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 1623 Post(s)
Liked 1,819 Times in 1,013 Posts
That steel frame looks to be too small for you. The bottom bracket height is 243mm! I think it was for junior racing.
Back in the mid 90s' to the mid 2000's, Trek and Cannondale both made a bunch of 650c wheel road bikes. I feel these are the best options for shorter riders. I would keep an eye out for those if I were you. This is a 44cm Cannondale R500 I got for my son who was around 5'1" when I bought him the bike:

I put the 155mm Origin8 crankset , short reach Microshift brifters and Panaracer Pasela 650x28c folding bead tires on there.
650x28c and 650x25c wire bead Pasela tires are available all the time. 650x28c folding bead Paselas are available once in a blue moon.
icemilkcoffee is online now  
Likes For icemilkcoffee:
Old 06-16-22, 02:05 PM
  #12  
Junior Member
Thread Starter
 
Krov9's Avatar
 
Join Date: Mar 2021
Location: Helsinki, Finland
Posts: 140
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 58 Post(s)
Liked 45 Times in 25 Posts
Originally Posted by icemilkcoffee
That steel frame looks to be too small for you. The bottom bracket height is 243mm! I think it was for junior racing.
Back in the mid 90s' to the mid 2000's, Trek and Cannondale both made a bunch of 650c wheel road bikes. I feel these are the best options for shorter riders. I would keep an eye out for those if I were you. This is a 44cm Cannondale R500 I got for my son who was around 5'1" when I bought him the bike:

I put the 155mm Origin8 crankset , short reach Microshift brifters and Panaracer Pasela 650x28c folding bead tires on there.
650x28c and 650x25c wire bead Pasela tires are available all the time. 650x28c folding bead Paselas are available once in a blue moon.
That bottom bracket height, among others, is most likely way off in the geometry drawing I made, really based on just the three or so measurements I knew.

Here's the ebay page for that frame, for that price Columbus SL and >1700 gram sure sounds like a steal, right? https://www.ebay.com/itm/26557287338...sAAOSw3f5hcWxp

Judging by the measurements, it seems that frame might have been designed with 24" rather than 26"/650C wheels in mind?

I've been keeping my eyes open for any Cannondales etc. in the right sizes, but so far I've only come across 48-50cm bikes with 700C wheels and awkward seat+fork angles.

The Rossin is coming together albeit slowly, as there still seems to be some issues with availability of parts, namely ITA bottom brackets. One I bought from LBS wasn't the right length after all, so I'll have to order somewhere else.

At the moment I have two 155mm cranksets, a Dotek without chainrings and a Miche Young double with 35-42. I first bought the Dotek from abroad for a little too much, and then I found the Miche locally for much less. The Dotek crank was sold as a BMX crank, but it's obviously meant for double, and the spider looks like it would be easy to drill&tap for triple too. I've heard these Doteks have some bad cred, so maybe I'll try the Miche first.

Last edited by Krov9; 06-16-22 at 02:09 PM.
Krov9 is offline  
Old 06-16-22, 02:22 PM
  #13  
Bikeable
 
headwind15's Avatar
 
Join Date: Jan 2011
Posts: 326
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Likes: 0
Liked 104 Times in 73 Posts
I believe that unless you put a super high stem on a frame with a 47 cm top tube, your knees are going to hit the handlebars. I do not know of/ never seen geometry for / have never seen an adult bike with a (super short) 47cm top tube.
headwind15 is offline  
Likes For headwind15:
Old 06-18-22, 09:41 AM
  #14  
Junior Member
Thread Starter
 
Krov9's Avatar
 
Join Date: Mar 2021
Location: Helsinki, Finland
Posts: 140
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 58 Post(s)
Liked 45 Times in 25 Posts

Finally some pics of the Rossin in its current state! Those 170 mm cranks are there just for test, they look huge with 130mm bcd and the bashguard! Brake reach on these old Weinmann scissor mechanism center pulls is just enough, I considered going with a pair of modern long reach dual pivots, until I figured that might cause some problems with fitting 42mm wide fenders.


The cockpit is kinda weird, I know that. It's there just for a test, I'll figure it out once I get to try how this thing rides. The inverted levers appealled to me because they seem to provide a short reach for my stubby fingers. The swept back comfort bar is to keep my head up high in traffic, and the quill adapter - ahead stem combo is supposed to allow ease of adjustment even after installing handebar tape. Shifter placement is something I'm not very sure about: I'm not used to downtube shifters and the reasonably high handlebar would put the levers quite far down from where my hands are, so I've been thinking about going with either stem-mounted or thumbshifters. I have a Suntour V GT Luxe / Vx set in the parts bin, so I'll probably try that first. This build sure is not for C&V purists

Based on my rough measurements the Rossin figures out something like this:


Compared to my other bikes, a late-80's Schwinn Impact with a 54cm top tube and a 52cm-ish Mercier mixte with a whopping 56cm of effective top tube, this steed sure feels short. But maybe that's just right?

Last edited by Krov9; 06-18-22 at 09:51 AM.
Krov9 is offline  
Likes For Krov9:
Old 06-18-22, 12:38 PM
  #15  
I'm good to go!
 
Iride01's Avatar
 
Join Date: Jul 2017
Location: Mississippi
Posts: 15,226

Bikes: Tarmac Disc Comp Di2 - 2020

Mentioned: 51 Post(s)
Tagged: 0 Thread(s)
Quoted: 6332 Post(s)
Liked 4,927 Times in 3,390 Posts
Looks nice, but with that low stack and effective short top tube length will your knees miss the bars?
Iride01 is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.