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Fork rake revisited...(9 posts)

Fork rake revisited...Psychler
Sep 12, 2003 7:16 AM
As noted in the post below, I am trying to dial in my frame/ bike...I want to "stabilize" the feel...less twitchy.
Which is LESS rake...45 or 43? I have a 43 on the bike now, builder told me that the 45 would make it MORE twitchy.... Ouzo/ Reynolds said the 45 would stabilize it more and make it LESS twitchy....ahhhhhh. I looked over all the diagrams, but I got more confused...consider me a dolt and just TELL me which one to use!
I have a 45 supplied by the builder, but put on the 43 I had on my previous frame. . If I use the 45, I will have to cut it...thus I can't return it and I am out the $$$.
re: Fork rake revisited...sievers11
Sep 12, 2003 7:24 AM
Less rake is a lower number(MM). It refers to how far the center of the drop outs line up with the center of the steer tube. Generally the smaller the number the more presise the steering because of the narrower wheel base and that the front wheel is more over the top of the headset. As you get a more layed out fork the ride get more solid because the wheel base gets longer and the effective angle of the head tube gets more slack.

You builder is on crack, I be you miss understood him or you should get a new builder, because he may have now idea what is going on. But from what you said Reynolds is right and your builder is wrong.
re: Fork rake revisited...Psychler
Sep 12, 2003 7:58 AM
Would the average human feel the difference between 43 and 45mm rake?
re: Fork rake revisited...Chen2
Sep 12, 2003 8:44 AM
Yes you will feel the difference between a 43 and a 45. As I explained before. I've had a 43 and now a 40 mm rake Ouzo Pro on my bike this year. These two were identical except for the rake. The bike is a 56cm Trek 5500 with a 73.8 HTA. I could feel the difference immediately, but not a huge difference. The 40 rake has more trail than the 43. It feels more stable and does not initiate the turns quite a quickly as the 43. Wheelbase has nearly nothing to do with steering. I noticed that the 2004 56cm Trek comes with a 45mm rake, even less trail, quicker response.
Here is a good link:
www.kreuzotter.de/english/elenk.htm

~Al
No, the builder is correctlaffeaux
Sep 12, 2003 10:29 AM
Your explination is incorrect. The 43mm offset will be more stable than the 45mm fork. The builder is correct.

A longer wheelbase, if achieved through a slacker head tube, or longer chain stays will indeed produce a more stable ride. However a longer wheelbase achieved through an increased fork rake will produce a less stable ride.

I have no idea if you can feel 2mm of rake or not, but if you are looking for a more stable ride with the options you have, go with the 43mm fork (assuming both forks are the same length). A longer fork will effect the head tube angle, at which point this becomes a more invloved question.
You must be on crack.Alexx
Sep 12, 2003 5:11 PM
You obviously don't know sh!t about steering geometry, otherwise you wouldn't have made this idiotic post.

Since you didn't get it the last 25 times I posted on just this subject (BTW, I'm a mechanical engineer, and I DO know what I'm talking about...), a fork with less rake will give you more trail, a shorter wheelbase, and more stability at speeds. Any effect on ride is purely coincidental. Angles don't change with rake.
don't you read???C-40
Sep 12, 2003 8:14 AM
Gee, we wentover this in great detail just a few days ago. Obviously 43mm rake is less than 45, BUT the 45 produces less trail than the 43 and quicker steering. I assume you're confusing rake with trail.

The formula for trail is (R/tanH) - (rake/sinH). The first half of the equation is the trail without the effect of rake. The second half is the REDUCTION in trail from rake. If you use less rake, there is a smaller reduction and hence a larger trail.

If you want more stable handling, you should try a 40mm rake.

For reference, why not copy and past this info into a word documment, then yu won't need to ask the same thing over and over. Computers are wonderful tools if used properly.
don't you read???Psychler
Sep 12, 2003 8:23 AM
No need to get rude... So I am a tad thick about these things...not a reason to get testy... You needn't answer if a post id it is going to get you upset. When this question was presented to the builder and Reynolds (who both got back to me today from an e-mail weeks ago) it ran contrary to some of the input here...which I will say, some of you disagreed with eachother... However, I do thank you for your input...
didn't mean to be rude, but...C-40
Sep 12, 2003 11:50 AM
When all the information is presented in such detail, even to the point of calculating the amount of trail for all three rakes (last time), I figured that would be enough.

Personally, I think it's darn good advice to save information for future use.