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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.

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Old 09-28-10, 08:00 PM   #1
CHAS
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75 mm fork bend with 45mm trail?

70mm rake with 45mm trail?
Ordered a frame. Just got the option of having 70mm bend put into the fork. This will be with a 71.5 degree angle.
That should equal 45mm trail or maybe more as the short frame has a greater angle than the taller ones.

I want low trail. Is this too much?
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Old 09-29-10, 02:53 AM   #2
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70mm rake with 45mm trail?
Ordered a frame. Just got the option of having 70mm bend put into the fork. This will be with a 71.5 degree angle.
That should equal 45mm trail or maybe more as the short frame has a greater angle than the taller ones.

I want low trail. Is this too much?
What is your wheel diameter? To calc trail posters need that info.
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Old 09-29-10, 10:10 AM   #3
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584 for 650B
It should also take 622-700c wheels
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Old 09-29-10, 10:11 AM   #4
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Originally Posted by CHAS View Post
70mm rake with 45mm trail?
Ordered a frame. Just got the option of having 70mm bend put into the fork. This will be with a 71.5 degree angle.
That should equal 45mm trail or maybe more as the short frame has a greater angle than the taller ones.

I want low trail. Is this too much?
70mm rake at 71.5 degrees using a wheel radius of 340mm (700c) gives 40mm of trail.
A 355mm radius would yield 45mm of trail.

If you plan on carrying loads on the front that would make sense.
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Old 09-29-10, 10:17 AM   #5
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you can use this calculator

http://yojimg.net/bike/web_tools/trailcalc.php
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Old 09-29-10, 10:51 AM   #6
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is the head tube angle slack to increase toe clip clearance? When you have a slack head tube angle, you need a lot of rake to get a low trail geometry
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Old 09-29-10, 01:47 PM   #7
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Thanks to all of you.
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Old 09-29-10, 02:54 PM   #8
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Quote:
Originally Posted by CHAS View Post
70mm rake with 45mm trail?
Ordered a frame. Just got the option of having 70mm bend put into the fork. This will be with a 71.5 degree angle.
That should equal 45mm trail or maybe more as the short frame has a greater angle than the taller ones.

I want low trail. Is this too much?
the builder is giving you the option to decide your fork rake and trail?
if so
then this is the wrong approach
the builder should have the nuts to know that they need to build for you
for your desires and needs in the bespoke bicycle.
what geo to fit under your position data
To give the client options on geo is bad on the builders part atmco
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Old 09-29-10, 06:36 PM   #9
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I prefer a bit less trail for a road-going 650b with handlebar bag. If you're not using a bag, 45mm will feel pretty good, especially with medium-width tires. If you're using very wide tires it may be overly stable on the road.

All of it is pretty unimportant, though. If you read enough (especially Bicycle Quarterly) it can come to seem as if a few mm of trail can be Earth-shaking. It isn't.
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Old 09-29-10, 07:30 PM   #10
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"To give the client options on geo is bad on the builders part atmco "

I think you have a fair point there, but I would say there are exceptions. He may just be asking what kind of front end the bike should have in the same way the cogswell porteur had several, then the client has the options before them in the same way they would have options on an MTB vs a cross bike, except it is a little more narrow.

For better or worse, we live in a world where the heart surgeon asks me what I want to do relative to various treatment options...
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