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going from 45mm rake to 43mm rake...(14 posts)

going from 45mm rake to 43mm rake...venga venga venga
Dec 1, 2003 3:56 PM
... any noticable difference in steering? i've read from earlier posts that more rake leads to quicker steering by decreasing trail so will this 2mm difference in rake make my bike steer like a pig or am i just splitting hairs? its not like going from 45mm to 40mm rake.
oops am i wrong?venga venga venga
Dec 1, 2003 4:05 PM
quote from http://www.citybikes.com/bikes/frame_geometry.htm

"Fork Rake
The fork rake or offset is changed by the bend in the legs of the fork, or in the case of straight taper forks, at the crown. The more rake a fork has the more "trail" there is in the steering, which makes the bike easier to control over rough terrain and at high speed, but more side to side floppy at low speeds"
citybike is wrong....C-40
Dec 1, 2003 4:11 PM
All rake reduces trail and speeds up the steering. A slight reduction in rake will slow the steering a bit at high speeds and make the bike a bit more stable. You'll barely notice the difference.

The formula for trail is: R/tanH -(rake/sinH). From this formula, it's obvious that more rake reduces trail.
so how about those chopper...venga venga venga
Dec 1, 2003 4:20 PM
...low rider bikes (as an extreme exaggeration of rake)? they look to have a lot (in feet) more rake than a road bike. just by looking at it, it would seem the front wheel would flop over. even my mountain bike's fork seem to flop over but maybe that's due to the slacker head tube angle 70 vs. 73 degrees for road.
confusing head tube angle with rake....C-40
Dec 1, 2003 4:34 PM
Motorcycles use the term "rake" to describe head tube angle. The equation is still the same. Choppers have an extremely slack value for "H" (the head tube angle). No telling how large the offset or rake is.
so confused....venga venga venga
Dec 1, 2003 5:06 PM
...every new link i find ffrom a google search shows up something diffferent. sheck this out

http://www.kvanproductions.com/cycling/bicycle_geometry_101.htm

and check out the chart they included. so fpr my small litespeed siena, i have a 73degree head tube. according to this site's chart 33.3375mm would be quick steering, 44.45mm would be touring and 52.3875 would be neutral steering. are these guys deadd wrong too?

i'm not questioning your knowledge (or maybe i am ;) ) but would you have any online references for your geometry theory?

thx
unusual....C-40
Dec 1, 2003 5:38 PM
Never seen a road bike with less than 50cm of trail or more than 67cm. Neutral is usually in the mid to upper 50's.
Steering geometryChen2
Dec 2, 2003 11:36 AM
Here is a site that I like to refer to for help understanding rake and trail:

http://www.kreuzotter.de/english/elenk.htm

I changed from a 43mm rake to an otherwise identical fork with a 40mm rake. I could feel the difference immediately, but it wasn't a huge difference and I could live with either. In some ways I like the 40 better and in other situations I like the 43 better. (We replaced the components on my wife's bike with the originals prior to selling, so I had an extra fork.)
~Al
cruisers and chopperslaffeaux
Dec 1, 2003 6:16 PM
"Cruiser bikes have very slack head tubes, so they have more trail despite their fork rake, not because of it. "

Here's an easy to understand article:
http://www.phred.org/~josh/bike/trail.html
THX GUYS...venga venga venga
Dec 1, 2003 6:35 PM
great article. easy to read (for my thick skull) and to the point. what i didn't understand earlier was that the centering force is controlled by the amount of trail. more rake, less trail, less centering force = quicker steering. makes sense. but what to make of the previous articles i posted? maybe the chart was supposed to read trail for the given head tube angle and not rake for the given angle.
ConfusionAlexx
Dec 2, 2003 6:10 AM
For some reason, there are still people in the cycling industry who still refer to trail in a backwards manner. Any engineer will tell you that reducing RAKE (a.k.a.: OFFSET) will give you a higher numerical value of TRAIL. Since trail is defined as a numerical value, then, logically, "more" trail means a larger numerical value, correct??

Well, some people who have been in the business for decades consider this to be "less trail". Why? I dunno-probably because they want to keep trail and rake connected somehow. I know it doesn't make sense, but I've seen this happen time and time again, and from people who actually know what they are talking about.

Whenever you talk about trail, you first need to ask them about their own understanding on the subject.
Just don't end up like this guy.DERICK
Dec 1, 2003 9:31 PM
Just don't end up like this guy.Saddle_Sore
Dec 2, 2003 1:33 AM
WTF?! Has that picture been altered by some Photoshop wizard? What is the rationale behind that design?

An early cadidate for Weird Bike of 2003 award maybe?
Just don't end up like this guy.DERICK
Dec 2, 2003 8:17 AM
No clue as to the the design. I don't think it has been photoshoped though. I actually came across the picture on this site a few years ago and saved it.