Geometry question
#1
Senior Member
Thread Starter
Join Date: Dec 2011
Location: NE Ohio
Posts: 2,595
Bikes: 1992 Serotta Colorado II,Co-Motion Speedster, Giant Escape Hybrid, 1977 Schwinn Super Le Tour
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 455 Post(s)
Likes: 0
Liked 112 Times
in
85 Posts
Geometry question
Maybe I need more coffe but sometimes I cannot see tge solution!
When you have toe overlap, where the toe interferes with the front wheel, how should a frame geometry be changed? Does this indicate a longer TT? A steeper HT angle?
While I wait I'
m goingvto have more coffee!
When you have toe overlap, where the toe interferes with the front wheel, how should a frame geometry be changed? Does this indicate a longer TT? A steeper HT angle?
While I wait I'
m goingvto have more coffee!
#2
Randomhead
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,395
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,696 Times
in
2,517 Posts
Enjoy the coffee. More rake and slacker head tube angle will give more toe clearance and will not change the handling much. How much overlap is it?
#3
Senior Member
Thread Starter
Join Date: Dec 2011
Location: NE Ohio
Posts: 2,595
Bikes: 1992 Serotta Colorado II,Co-Motion Speedster, Giant Escape Hybrid, 1977 Schwinn Super Le Tour
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 455 Post(s)
Likes: 0
Liked 112 Times
in
85 Posts
My current frame,maybe 1". But just trying to exoand my knowledge base!
#4
framebuilder
Tom, there are several ways to increase your front center to avoid toe overlap. Production frames almost always rely on using a steeper seat angle to push the front wheel forward. This is okay for a performance style of bicycle but not for a more relaxed sitting-more-upright-position (more necessary as we age). Eric is right that the easiest thing to do is slacken the head angle and at the same time that increases the fork rake. Another option is to lengthen the top tube while at the same time shortening the stem. Sometimes these compromises can negatively effect how the frame handles. And then you have to ask yourself "what is more important?" Maybe you have to tolerate some toe overlap (especially if you have fenders). These problems are why in some circumstances, smaller wheels should be chosen. This is particularly true on smaller frames. The desire to stick with big wheels never made sense to me when building a custom frame when smaller wheels can remove some of the problems. For example if one is going to use 38 mm wide tires, it is better to use a 650B tire than a 700C one. Or perhaps going to an MTB 559 tire.
Likes For Doug Fattic:
#6
Senior Member
Join Date: Jan 2013
Location: South Jersey
Posts: 2,266
Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 714 Post(s)
Liked 800 Times
in
475 Posts
As a shorter rider, I always have to deal with toe overlap issues. I've found that pushing the entire front end further forward and using a shorter stem to be the best solution for me. This has several benefits, especially for off road bikes, with the only negative being that it is harder to ride with no hands at lower speeds.
#7
Randomhead
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,395
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,696 Times
in
2,517 Posts
I tried moving the head tube forward/shorter stem on my randonneuring bike and I like it. It's fine on high speed descents, and I have never noticed anything while cornering. The only thing it does is "steer in" a little on a really tight turn, like into a driveway. I might go with a little less rake, it has something like 65mm. Okay, the other thing is that I have trouble getting used to the way the short stem looks.
With such low trail, some front load is required though. I'm sure I'd get used to it unloaded, but if I was riding it unloaded regularly I'd want more trail. I did it to get the rando bag closer to the head tube.
With such low trail, some front load is required though. I'm sure I'd get used to it unloaded, but if I was riding it unloaded regularly I'd want more trail. I did it to get the rando bag closer to the head tube.
#8
Senior Member
Thread Starter
Join Date: Dec 2011
Location: NE Ohio
Posts: 2,595
Bikes: 1992 Serotta Colorado II,Co-Motion Speedster, Giant Escape Hybrid, 1977 Schwinn Super Le Tour
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 455 Post(s)
Likes: 0
Liked 112 Times
in
85 Posts
Thanks for your replies!