leading axle forks?

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06 Sep 2006 08:51 #74834 by Rickman
leading axle forks? was created by Rickman
Why does my LTD have the axle on the front of the fork tubes, where just about every other bike I look at has the axle on the bottom of the tube?

1983 KZ1100-L1 "LTD Shaft"
Wiseco 10.5:1 1171 piston kit, bored by APE
Dyna 2000, Dyna S, Dyna grey coils, WG coil power mod, CB900 starter

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06 Sep 2006 09:41 #74846 by apeman
Replied by apeman on topic leading axle forks?
My KZ750H [LTD] bikes have the leading axle as well. That, plus the increased stearing head rake makes the handling much more highway (or drag strip) stable at the top end. My KZ750E [Standard] has the lesser rake and the axles at the base of the forks, and is much more responsive in the twisties.

Petaluma and Truckee, CA -- member since Jan. 23, 2003;
PREVIOUS KZs: 1980 KZ750H with 108,000 miles; 1980 KZ750E with 28,000 miles; and KZ750H street/cafe project, all sold a few years back.

This is what I do for fun, not for work. It is art, with a little engineering thrown in.

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06 Sep 2006 12:37 #74884 by kawadruida
Replied by kawadruida on topic leading axle forks?
My Z550 has the leading axle type, and my Gpz550 has a center axle fork. I think that apeman is right, the Z550 being a compromise between those two examples (leading axle but less rake than the LTDs)

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  • pstrbrc
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06 Sep 2006 13:01 #74888 by pstrbrc
Replied by pstrbrc on topic leading axle forks?

My KZ750H [LTD] bikes have the leading axle as well. That, plus the increased stearing head rake makes the handling much more highway (or drag strip) stable at the top end. My KZ750E [Standard] has the lesser rake and the axles at the base of the forks, and is much more responsive in the twisties.

Actually, the leading axle (assuming the same triple clamps, and therefore the same triple clamp offset) would decrease the trail, making the steering quicker. If the bike with the leading axle fork tubes has more rake, the leading axles would just lessen the increased trail due to increased rake. Got that?
I think the leading axle was a way to minimize the effect of the increased rake, while still giving the "chopper" look. The ergonomics of the bikes (where the rider's hands, feet, and butt interact with the bike) is probably the difference in the perceptions of quickness. For instance, my GPz1100 has a whopping 29 degrees of rake, where the standard had (IIRC) 26 degrees. Which one do you think is more fun in the twisties?

\'81 GPz 1100 project
Elkhart, Kansas USA
\"Man does not control his own fate. The women in his life do that for him.\" Groucho Marx

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06 Sep 2006 13:08 #74893 by mariozappa
Replied by mariozappa on topic leading axle forks?
This is an interesting question. And I'm interested in the answers and opinions.
My 1982 kz750H project bike is supposed to have leading axle forks, but has the forks with axles on the bottom.
I've only ridden it at about 30MPH since it has crappy old tires on it, so I can't say how it handles...yet.
Somebody has obviously swapped the forks out awhile ago, and I wonder if it will help or hinder the steering.
:huh:

1977 KZ650C1
and the KZ650/KZ750 Conversion ;)

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06 Sep 2006 21:03 #75012 by apeman
Replied by apeman on topic leading axle forks?
Mariozappa and pstrbrc,

Your posts interest me, since I clearly have a limited understanding of steering geometry. I thought (wrongly, I guess), that the increased linear distance between the steering head and the axle made the bike less responsive (and more stable at high speeds) in steering. Both the leading axle and the greater steering head angle contribute to this increase in distance. What is it that I have misunderstood.

Mariozappa, I was thinging about putting the forks from a KZ750E on my KZ750H [LTD]. The E model has the axle on the fork bottom. It sounds like you have this setup, so I would like to hear how it works after you get your bike in top shape. I THOUGHT it would make my LTD more responsive in the turns, like the E model is. Fellow KZriders, am I wrong about this????

Petaluma and Truckee, CA -- member since Jan. 23, 2003;
PREVIOUS KZs: 1980 KZ750H with 108,000 miles; 1980 KZ750E with 28,000 miles; and KZ750H street/cafe project, all sold a few years back.

This is what I do for fun, not for work. It is art, with a little engineering thrown in.

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07 Sep 2006 05:05 #75040 by mariozappa
Replied by mariozappa on topic leading axle forks?
Apeman,
I let you know how it works out.
I've seen the 900 and 100 LTD without the leading axle that came from the factory, but I don't know what the difference in the rake is.
Back to looking at the specs.
:S

1977 KZ650C1
and the KZ650/KZ750 Conversion ;)

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08 Sep 2006 09:36 #75290 by timber
Replied by timber on topic leading axle forks?
pstrbrc is right. the leading axle and raked trple trees are ways to reduce trail in those long chopper front ends. that little bit makes a big difference in trail figgures. most trail numbers are from 3.5 to 6 inches of trail.

the comment about rake is not always to correct way to guess how a bike will handle in the twistys. trail is a line that goes thought the neck stem to the ground and a line that goes though the axle to the ground. the distance between those two points is your trail. longer the trail the more stable the bike is at speed and it wants to go in a straight line but a slow speeds you get what chopper folk call wheel flop. the shorter trail numbers you see in sport bikes account for the snap handling and response that you need in a sport bike.

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  • pstrbrc
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08 Sep 2006 10:14 #75294 by pstrbrc
Replied by pstrbrc on topic leading axle forks?
For those of you who would like a basic primer in motorcycle suspension, here's a link:
www.carbibles.com/suspension_bible_bikes.html
It's written by a car guy, so it's not nearly as complete as some of my textbooks on my shelf (I haven't always been a minister, :) I was a beer-drinking engineer in another life :blush: ) but what's there is good.

\'81 GPz 1100 project
Elkhart, Kansas USA
\"Man does not control his own fate. The women in his life do that for him.\" Groucho Marx

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