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

Tri bike rear dropout mod for tire size options

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.

Tri bike rear dropout mod for tire size options

Old 03-09-21, 10:00 AM
  #1  
treebound 
aka: Mike J.
Thread Starter
 
treebound's Avatar
 
Join Date: Apr 2005
Location: between Milwaukee and Sheboygan in Wisconsin
Posts: 3,448

Bikes: 1995 Trek 520 is the current primary bike.

Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 113 Post(s)
Liked 58 Times in 39 Posts
Tri bike rear dropout mod for tire size options

I’ve got a Trek Equinox 7 from around 2008, and even though it was spec’d with 23mm wide tires when new, modern 23mm tires won’t clear the seat tube so I had to find a 700x20mm tire and 20mm tires are virtually non-existant these days.

So I think my options are to convert the bike to 650b (I really don’t want to go this route), or modify the rear dropouts, or have the rear dropouts replaced.

Right now I’m thinking it might be viable to machine or file a horizontal slot rearward in the vertical slot thereby turning the dropout into a pseudo-horizontal dropout. I haven’t done any careful measurements yet to determine how far rearward I would need to extend the slot nor have I verified if this is even feasible. I’m kind of thinking just an axle diameter might be enough to provide clearance to the seat tube.

I don’t want to convert to tubular rims, so if I damage or wear out the current tires then the bike is basically parts.

I have attached a marginal photo of the rear of the bike along with a quick and dirty CAD sketch showing what I’m considering. And of course if I cut too far rearward then durability becomes a factor.

I figured the framebuilders section might be the best place to post this. I don’t know how long I’ll keep this bike so just looking for input right now.

thanks for any advice or opinions.



treebound is offline  
Old 03-09-21, 01:25 PM
  #2  
unterhausen
Randomhead
 
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,362
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,662 Times in 2,496 Posts
I feel like you're out of luck. I didn't see what kind of aluminum this is made out of, but generally replacing aluminum dropouts isn't a great idea.
I think the dropout will break if you mill the slot.
unterhausen is offline  
Old 03-09-21, 04:05 PM
  #3  
treebound 
aka: Mike J.
Thread Starter
 
treebound's Avatar
 
Join Date: Apr 2005
Location: between Milwaukee and Sheboygan in Wisconsin
Posts: 3,448

Bikes: 1995 Trek 520 is the current primary bike.

Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 113 Post(s)
Liked 58 Times in 39 Posts
Thanks for the input, kind of the conclusion that I'm coming to.
__________________
= = = = = = = = = = = = = = = = = = = = = =
Life happens, don't be a spectator.
treebound is offline  
Old 03-09-21, 07:09 PM
  #4  
Andrew R Stewart 
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 17,998

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: 4171 Post(s)
Liked 3,789 Times in 2,269 Posts
How wide are the rims, are they OEM spec still? (We've had more then one older bike that when "up graded" to current trendy wider rims end up not having much/any tire clearance with the older tires). I assume the bike has seen a number of different skinny (23?) tires in the search. I say this because the labels are not the actual dimensions and playing with tires "suggested" widths is an age old marketing device to drive sales. When things get tight or close there's no method like actual trying to be sure. Bummer that the bike is so restrictive but I guess that's part of the untold cost to buying on the ragged edge. Andy
__________________
AndrewRStewart
Andrew R Stewart is offline  
Old 03-10-21, 05:52 AM
  #5  
treebound 
aka: Mike J.
Thread Starter
 
treebound's Avatar
 
Join Date: Apr 2005
Location: between Milwaukee and Sheboygan in Wisconsin
Posts: 3,448

Bikes: 1995 Trek 520 is the current primary bike.

Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 113 Post(s)
Liked 58 Times in 39 Posts
The rims are narrow. The problem is the height of the tire which rubs against the rear side of the seat tube.

I think I still have an pair of dried out 700x23 tires that are shorter than the 20’s currently on the bike.

I might have to just stop at one of the local bike stores and bring some calipers with me and start measuring tire heights.
__________________
= = = = = = = = = = = = = = = = = = = = = =
Life happens, don't be a spectator.
treebound is offline  
Old 03-10-21, 06:51 AM
  #6  
burnthesheep
Newbie racer
 
Join Date: Feb 2018
Posts: 3,406

Bikes: Propel, red is faster

Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 1575 Post(s)
Liked 1,568 Times in 973 Posts
This is why I'd never own a vertical dropout tri/TT bike. Sorry that doesn't help the situation. But I wouldn't do what you have listed.

You could perhaps experiment with running wider wheels like an HED. 23's site shorter on those than narrower wheels. You'd just have to measure your chainstay width. If your rims are really narrow now, even the older HED "c2" width wheels might be wide enough to fit that 23 tire. Maybe find a local who owns a set of said wheels and meetup just to test fit.

Used HED's go for reasonable used prices if they aren't the newer 25mm wide ones. The 23mm wide ones go for pretty reasonable.
burnthesheep is offline  
Old 03-10-21, 10:06 AM
  #7  
treebound 
aka: Mike J.
Thread Starter
 
treebound's Avatar
 
Join Date: Apr 2005
Location: between Milwaukee and Sheboygan in Wisconsin
Posts: 3,448

Bikes: 1995 Trek 520 is the current primary bike.

Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 113 Post(s)
Liked 58 Times in 39 Posts
I’m going to check the rim widths of my road bike wheels, and if wider then I will begin some tire swapping checks.
__________________
= = = = = = = = = = = = = = = = = = = = = =
Life happens, don't be a spectator.
treebound 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


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.