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5500 new fork and handling problems/ help(5 posts)

5500 new fork and handling problems/ helpgtrguy
Oct 7, 2003 4:22 AM
I have a Trek 5500 that I upgraded the fork from a carbon/steel to an Onzo all carbon. The LBS ordered the fork with the right goemetry for my frame. I also added Mavic/Ksyrs (sp?) wheels and replaced old "600" wheels(before Ultegra). The problem is that the at speed above 25 the front end gets Squirrly. It never used to. Any ideas? Is it just the lighter weight?
re: 5500 new fork and handling problems/ helpgtrguy
Oct 7, 2003 4:27 AM
I have to add that my 5500 is at least 6 yrs old
not enough info...C-40
Oct 7, 2003 4:39 AM
Your problem has nothing to do with weight.

I would suspect that the new fork may not have the "right geometry".

The old fork should be carefully measured from the center of the axle to the bottom of the crown race and compared with the same measurement on the new fork to be sure that a length difference did not change the head tube angle. Only a significantly shorter new fork would cause what you describe. The offset or rake on the fork should also be checked to see that the new fork does not have substantially more rake than the old fork.

As long as the headset is properly adjusted, there is no reason that there should be any significant difference is the bike's handling. I would check the headset adjustment the very first thing. Headset bearing races often "settle" during the first few miles of use, resulting in immediately loose bearings. This ususally means that the installer did not properly seat the lower races on the fork and head tube.
re: 5500 new fork and handling problems/ helpChen2
Oct 7, 2003 6:27 AM
I upgraded my 1998 Trek 5500 with an Ouzo Pro with no problems, in fact it feels more stable. What size is your Trek and what rake was the new fork?
re: 5500 new fork and handling problems/ helpSpiderman
Oct 7, 2003 8:46 AM
Try swapping out the wheels.
I used to work at a manufacturer and about 80% of the bikes that came back with "wobble" issues had Ksyriums on them. The bikes were all aligned so it wasn't that. We would swap out wheels and test ride it and the problem usually went away.

We went sure but we theorized that because the K's are so stiff, they transmit a lot of vibration through the wheels. It was just a guess, we didn't know if we were right, but the problem seemed to go away.

Another thing you can check is the actual alignment of the fork. Its all carbon so adjusting would be hard, but make sure the dropouts are even depths and the wheel is seated properly.

double check the crown race - maybe it wasn't installed on the fork properly.

just some thoughts.