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Fork rake, Trail, Handling, and high speeds(13 posts)

Fork rake, Trail, Handling, and high speedssurf
Feb 11, 2002 8:31 AM
I know this topic has been discussed before but I am still mixed up.

My bike is very touchy and was tough getting used to as far as handling goes and especially when getting on the aero bars. Right now I have it down (I was riding a touring bike before this). One surprising thing to me though was that at high speeds the bike was rock solid, no wobble and very steady. So, I probably wont change anything (I was going to look into replacing the fork at on time) but I still don't get the fork and how it influences ride.

What is for rake (is it just the curve in the fork, mine seems to have a lot of curve or at least a moderate amount). IS more rake better for high speeds or handling . ect?

What is trail?

How do those bikes handle with straight forks (Forgot the company but they specialize in tri and TT bikes).

Any other comments would be appreciated.
Thanks!
re: Fork rake, Trail, Handling, and high speedsChen2
Feb 11, 2002 9:02 AM
Yeah, I'm trying to get myself better educated on the subject myself, I need to see a picture. I think the curvature alone can be misleading because the angel in the crown area has just as much to do with rake. Straight forks can be made with as much rake as curved forks. www.SheldonBrown.com have definitions for rake and trail, but I need a picture.
-Al
re: Fork rake, Trail, Handling, and high speedsbrider
Feb 11, 2002 9:11 AM
I'll try to clear this up. Yes, fork rake refers to the amount of offset in the fork blades (straight bladed forks do have rake as well, even though they aren't curved). Trail refers to the distance behind the steering axis that the tire contact patch is (a straight line drawn through the steerer tube hitting the ground). So both fork rake and head tube angle determine trail. The larger the trail, the steadier the bike will be. Of course, there are practical considerations. I don't recall what the real-world numbers are for trail. Any way, if you look at the derny races (usually in the Eurpean 6-day events), you'll see that the bikes used have the forks turned around. This is for the high (very high) speed stability. When you throw in aero-clip-ons, there's a whole 'nother idea put in the fix -- that of steering from the shoulders and torso rather than the hands. But that's just technique, and not really dependent on the geometry of the bike. Hope that helps.
This website has a good diagram for showing R&T...Cima Coppi
Feb 11, 2002 9:19 AM
http://www.msteelcycles.co.uk/wuzframed.htm

Look about half way down the page.

CC
This website has a good diagram for showing R&T...Chen2
Feb 11, 2002 11:02 AM
Thanks much. Without the picture I couldn't understand why trail increases as rake decreases. A picture is worth a thousand words, it's trite but true.
-Al
This website has a good diagram for showing R&T..._Marty_
Feb 11, 2002 3:26 PM
sooo.. if rake goes up.. trail goes down.. bike gets.. nervous? and if rake goes doan.. trail goes up.. bike calms down? right???
This website has a good diagram for showing R&T...Chen2
Feb 11, 2002 5:49 PM
Marty, that seems to be the case. Comments anyone?
-Al
you wanna comment? take thiscyclopathic
Feb 11, 2002 8:35 PM
2 bikes







 bike 1bike 2
head angle 71.5 72
seat angle 75.3 74
rake 51mm 38mm
wheelbase 983mm 975mm
TT 532mm 535mm


guess which one would handle faster?
/clue 0.5 in headangle changes Trail by 3mm/
InterestingChen2
Feb 12, 2002 6:55 AM
Two bikes with = trail, I would think the bike with the shorter wheelbase would be the quicker, no?
-Al
re: Interestingcyclopathic
Feb 12, 2002 9:04 AM
Trail1 = trail2+3mm+(38-51) = trail2-10mm

anyways it should be faster but it's slower. I have serious doubts about published data.

CP

PS btw bike 2 has shorter chainstays, maybe that's why?
re: InterestingChen2
Feb 12, 2002 9:34 AM
I gotta think about this. And I misread your earlier post.
I was just now trying to compare the 56cm OCLV with the 56cm C-40. Both have 43mm rake, the Trek head tube angle is 73.8, the Colnago is 71.8. The Trek's TT is 56.1, the Colnago's is 55.0, all of this based on published geometry and in part confirmed by my measurements. My friends C-40 has a 1cm shorter wheelbase. So which has the quicker steering? Trek because of it's steeper head tube angle??
Less trail?
-Al
seems socyclopathic
Feb 12, 2002 10:13 AM
Trek should have trail ~54mm and C-40 67mm.

didn't work for me though.. can you get them for test ride?
YepChen2
Feb 12, 2002 11:27 AM
One of my riding buds has a C-40 and I've got a 5500, both 56cm, we're going to switch pedals some day and ride each other's bikes. Mostly I'm just trying to educate myself on bike geometry, not looking for a new ride now, thanks for your help.
-Al