Go Back  Bike Forums > Bike Forums > Framebuilders
Reload this Page >

Adjusting a frameset to 650B Geometry Question

Notices
Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

Adjusting a frameset to 650B Geometry Question

Old 03-01-19, 06:54 PM
  #1  
Gyro_T
Full Member
Thread Starter
 
Gyro_T's Avatar
 
Join Date: Apr 2011
Location: Oregon
Posts: 296

Bikes: 1974 Jack Davis, Zeus Competition, Bridgestone MB2, Kona Rove Ti 1 X 11, Salsa Fargo Ti

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked 7 Times in 7 Posts
Adjusting a frameset to 650B Geometry Question

I have an old 531 tubing kit and the main triangle is already together. I hope to fit 42mm tires on 650B rims and wanted to know if I should trim the length of the fork blades (pre-raked) to keep the geometry correct, i.e. didn't want the head tube lifted up too much, or the chain stays to be too long. This is going to be an all around touring bike. With 42mm tires the total diameter may be not far from 700C wheels with narrow tires, so possibly no trimming would be necessary?
Gyro_T is offline  
Old 03-01-19, 10:03 PM
  #2  
Andrew R Stewart 
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,003

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4172 Post(s)
Liked 3,792 Times in 2,271 Posts
Can we make assumptions?

Like what tire diameter tires (rim diameter and tire width) the frame (and hence the main triangle) was designed for? How about steering geometry or stay lengths? Can you indent stays, have you done this before? Have you drawn out any aspects of the original or modded designs?

By shifting BB drop fork height issues can be dealt with to a degree without seat or head angles shifting too much. But the devil is in the planning. I'd design a new frame and see how the old main triangle overlaps with the new. I don'[t think we can offer specific suggestions without a lot more info. Andy
__________________
AndrewRStewart
Andrew R Stewart is offline  
Old 03-01-19, 10:35 PM
  #3  
calstar 
Senior Member
 
calstar's Avatar
 
Join Date: Mar 2012
Location: santa barbara CA
Posts: 1,115
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 96 Post(s)
Liked 30 Times in 21 Posts
Using the chain stays that are with the kit? You might have to modify/indent them to fit 42s. Same with the fork, check the crown to see what the max tire size may be, maybe not 42s.

regards, Brian
__________________
Brian
calstar is offline  
Old 03-02-19, 06:56 AM
  #4  
dsaul
Senior Member
 
Join Date: Jan 2013
Location: South Jersey
Posts: 2,258
Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 712 Post(s)
Liked 793 Times in 471 Posts
Theoretically, the outer diameter of a 700 x 23 tire is exactly the same as a 650b x 42 tire at 668mm.

In any event, if you are using the same size tires front and rear, none of the angles will change. If the tire diameter is different from the original, bottom bracket drop and trail will be the only things that change. Tire clearance is a different matter and 42's may not be possible with a road frame and fork.
dsaul is offline  
Old 03-02-19, 09:00 AM
  #5  
Gyro_T
Full Member
Thread Starter
 
Gyro_T's Avatar
 
Join Date: Apr 2011
Location: Oregon
Posts: 296

Bikes: 1974 Jack Davis, Zeus Competition, Bridgestone MB2, Kona Rove Ti 1 X 11, Salsa Fargo Ti

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked 7 Times in 7 Posts
Originally Posted by dsaul
Theoretically, the outer diameter of a 700 x 23 tire is exactly the same as a 650b x 42 tire at 668mm.

In any event, if you are using the same size tires front and rear, none of the angles will change. If the tire diameter is different from the original, bottom bracket drop and trail will be the only things that change. Tire clearance is a different matter and 42's may not be possible with a road frame and fork.
Thanks dsaul! I thought it might be pretty close, just wanted to hear it from someone else. And to answer the others, yes, I have flattened the profile of the inside of the chain stays, and I have ordered a wider fork crown to fit the wider tires. This is my first complete frame, but I have been practicing with brass and silver on racks and scrap tubing for a while. I had to get a new pair of chain stays (from Henry James) since I lost one from the kit somehow. I bought this kit from the shop I worked in from 1973-1978. We got ten sets on a closeout deal from the distributer. We paid $20 each for the double butted tube sets. I am prepared to down size the tires a bit. I have a gauge and the 42mm would fit based on the gauge but it would be a tight squeeze. I am able to flatten the inside of the chair stays a bit more and plan to do that today. I used a sculpted out block of wood and a vice for that purpose.
Gyro_T is offline  
Old 03-02-19, 09:18 PM
  #6  
unterhausen
Randomhead
 
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,364
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,664 Times in 2,497 Posts
you can fit wider tires if you make the stays longer than you might otherwise make them. Many people say that longer stays is imperceptible to them, and they certainly are for me.

Also, you can braze the rear dropouts on the stays and then check the fit before you braze anything else on the rear triangle. It's a lot better if you have a fork for that, but you don't need a fork for rear stay clearance checks
unterhausen is offline  
Old 03-04-19, 10:35 AM
  #7  
Gyro_T
Full Member
Thread Starter
 
Gyro_T's Avatar
 
Join Date: Apr 2011
Location: Oregon
Posts: 296

Bikes: 1974 Jack Davis, Zeus Competition, Bridgestone MB2, Kona Rove Ti 1 X 11, Salsa Fargo Ti

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked 7 Times in 7 Posts
Originally Posted by unterhausen
you can fit wider tires if you make the stays longer than you might otherwise make them. Many people say that longer stays is imperceptible to them, and they certainly are for me.

Also, you can braze the rear dropouts on the stays and then check the fit before you braze anything else on the rear triangle. It's a lot better if you have a fork for that, but you don't need a fork for rear stay clearance checks

Thanks Unterhausen,
I left the stays a bit longer and now I am pretty confident there will be no problem with 38mm tires, not positive about 42mm but I can be happy with 38s. The method I used for shaping the chain stays did not work as well as I would have liked. I was shooting for maintaining a convex surface on both the inside and outside and getting a nice regular "D" shaped cross section. I shaped a block of oak and placed the stay in that "U" shaped groove and used a piece of softer wood on the inside and squeezed it in a vice. An arbor press might have been better. Basically it wound up squeezing in on both sides despite my groove on the outside face. Consquently, it looks a little flattened on the outside face, and I can chalk that one up to a "first frame" lesson. I thought I could get the clearance without creating a concave crease on the inside of the stays, but maybe that is just not feasible.
Gyro_T is offline  
Old 03-04-19, 10:46 AM
  #8  
unterhausen
Randomhead
 
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,364
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,664 Times in 2,497 Posts
I have used a hammer. Don't go crazy with it.
unterhausen is offline  
Old 10-02-19, 04:30 PM
  #9  
Gyro_T
Full Member
Thread Starter
 
Gyro_T's Avatar
 
Join Date: Apr 2011
Location: Oregon
Posts: 296

Bikes: 1974 Jack Davis, Zeus Competition, Bridgestone MB2, Kona Rove Ti 1 X 11, Salsa Fargo Ti

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked 7 Times in 7 Posts
Clearance looks decent for 42 mm tires without fenders...or mud. I need to shorten the fork blades about 30 mm. I would like to get a nice square cut and I'm a little unsure if I can do it with the tools at hand. I have an ordinary homeowner hacksaw, of course, and a dremel with a cutoff wheel. These are 531 fork blades with the "Imperial" shaped of oval which is flatter than most of what we see now the "Continental". Any suggestions on how to get a clean straight cut on those blades would be greatly appreciated.

Gyro Gearloose
Gyro_T is offline  
Old 10-02-19, 05:17 PM
  #10  
TiHabanero
Senior Member
 
Join Date: Nov 2012
Posts: 4,435
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 1726 Post(s)
Liked 1,350 Times in 705 Posts
Can be done with a hacksaw, but need to have good sharp blade and good control over the saw. Use two hands on the saw one on the front and other on the handle. Slow cutting motion, keeping eye on straightness of cut. Cut several mm longer than desired. Have a line marked all the way around the leg and judge cut by the line. If going off line, turn blade 90 degrees and start again. Eventually you will get through the leg reasonably well and take a file to make it straight. I have done all my tubes this way with good results.
TiHabanero is offline  
Old 10-02-19, 05:27 PM
  #11  
unterhausen
Randomhead
 
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,364
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,664 Times in 2,497 Posts
a steerer cutting guide will work
unterhausen is offline  
Old 10-02-19, 07:04 PM
  #12  
Doug Fattic 
framebuilder
 
Join Date: Dec 2009
Location: Niles, Michigan
Posts: 1,459
Mentioned: 50 Post(s)
Tagged: 0 Thread(s)
Quoted: 610 Post(s)
Liked 1,905 Times in 647 Posts
You can use masking tape as a cutting guide. Use a small adjustable machinist square to set the top of the tape distance from the top of the blade. Obviously you move the square with the ruler set to your preferred distance to different spots to make sure the tape is equidistant all the way around. Next cut close but not exactly on the tape line. If you start to go crooked, you turn the blade over and finish the cut from the other side. Now file right to the tape line. This method insures the shortened blade remains square at the top.
Doug Fattic is offline  
Old 10-02-19, 11:22 PM
  #13  
Gyro_T
Full Member
Thread Starter
 
Gyro_T's Avatar
 
Join Date: Apr 2011
Location: Oregon
Posts: 296

Bikes: 1974 Jack Davis, Zeus Competition, Bridgestone MB2, Kona Rove Ti 1 X 11, Salsa Fargo Ti

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked 7 Times in 7 Posts
Thanks to TiHabañero, Unterhausen, and Doug for your valuable suggestions. I have what I need to proceed. This may be the longest frame building project ever. Looking forward to starting another frame soon.
Gyro_T is offline  
Old 10-03-19, 05:53 AM
  #14  
unterhausen
Randomhead
 
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,364
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,664 Times in 2,497 Posts
how long has it taken you? If you bought the tubes retail back in the '70s, then you win. But my travel bike that I just finished was started in 2010. And I'm not quite done with a frame I started in 2008-ish. It's quite possible Andy has me beat though.
unterhausen is offline  
Old 10-03-19, 08:28 AM
  #15  
Andrew R Stewart 
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,003

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4172 Post(s)
Liked 3,792 Times in 2,271 Posts
Originally Posted by unterhausen
how long has it taken you? If you bought the tubes retail back in the '70s, then you win. But my travel bike that I just finished was started in 2010. And I'm not quite done with a frame I started in 2008-ish. It's quite possible Andy has me beat though.
Maybe... I have the frame/fork from Doug's brazing class (we made a Dutch style bike as his Ukrainian project uses, and no the rumors of Doug being called to testify before congress are false) that is still unfinished. I just don't have the time to add the braze ons… The class was in 2008.

I have had frames (that were completed) take a few years before. My 3-speed started as a hub scavenged from Geo Rennies Bicycle Shop in about 1980, the bike was on the road by 2006. Then there's the projects not even started but have been moved with me many times. Andy
__________________
AndrewRStewart
Andrew R Stewart is offline  
Old 10-06-19, 11:18 PM
  #16  
Gyro_T
Full Member
Thread Starter
 
Gyro_T's Avatar
 
Join Date: Apr 2011
Location: Oregon
Posts: 296

Bikes: 1974 Jack Davis, Zeus Competition, Bridgestone MB2, Kona Rove Ti 1 X 11, Salsa Fargo Ti

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked 7 Times in 7 Posts
Originally Posted by unterhausen
how long has it taken you? If you bought the tubes retail back in the '70s, then you win. But my travel bike that I just finished was started in 2010. And I'm not quite done with a frame I started in 2008-ish. It's quite possible Andy has me beat though.
I bought two Reynolds 531 tube sets of the in either 1974 or 75 while working at Bumsteads Sporting Good in Ontario, California. One set was built up by Jack Davis as my road race bike, which I equipped with Campy Nuovo Record and I still own. I finished out some very rough lugs (Prugnant knock-offs) back about that time and then did not touch it again until the mid nineties. I had problems with keeping the brass flowing and did not have a much information to go on at that time. Since then, this forum, Youtube videos and practice, I managed to finally finish the frame with a new set of cast lugs. I found a new fork crown to match the "Continental" 531 oval fork blades at Rene Herse Cycles. Technically, I won't be done until I finish the fork and paint it the whole bike. That may not happen until later this year. I am shooting for my second frame to be done by next Spring!
Gyro_T is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
bikebreak
Bicycle Mechanics
7
11-08-18 03:06 PM
sweetspot
Cyclocross and Gravelbiking (Recreational)
35
10-11-18 11:19 AM
Soundtallica
Cyclocross and Gravelbiking (Recreational)
5
02-11-17 11:16 PM
Dylansbob
Bicycle Mechanics
4
01-27-11 12:07 AM
Ciufalon
Classic & Vintage
27
01-03-11 06:27 PM

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


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.