How much vibration is normal for a fork?
#1
500 Watts
Thread Starter
Join Date: Aug 2006
Location: Ann Arbor, MI
Posts: 833
Bikes: Trek 7200 FX ('05), Trek 6000 ('07)
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
How much vibration is normal for a fork?
My brakes suck, as some may recall from previous posts, but when I brake hard enough down this one 15 grade incline on my commute my fork really vibrates. This vibration causes the braking to seem weird (that is how I first noticed it). What will happen is that my brakes will operate normally and then every half second or so the front of the bike will like... I can't explain... Not jump but like have a small but sharp "knock" and the brakes will resume normal operation.
At first I thought maybe my front rims were messed up (like something was knocking against the pads or some irregularity or something), but now I can tell it is the fork.
This leads me to my question - how much vibration/flex is okay for an aluminum front fork? Mine will flex maybe 3/4 of a centimeter and vibrate under the most strenuous braking.
Thanks!
[edit] - the vibration's effects on the braking and weird knocks and stuff has been happening since I got the bike, and I don't think that the level of knocking actually could interfere with braking performance a lot so this isn't a life/death situation ^.^
At first I thought maybe my front rims were messed up (like something was knocking against the pads or some irregularity or something), but now I can tell it is the fork.
This leads me to my question - how much vibration/flex is okay for an aluminum front fork? Mine will flex maybe 3/4 of a centimeter and vibrate under the most strenuous braking.
Thanks!
[edit] - the vibration's effects on the braking and weird knocks and stuff has been happening since I got the bike, and I don't think that the level of knocking actually could interfere with braking performance a lot so this isn't a life/death situation ^.^
#2
cab horn
Join Date: Jun 2004
Location: Toronto
Posts: 28,353
Bikes: 1987 Bianchi Campione
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 42 Post(s)
Likes: 0
Liked 25 Times
in
18 Posts
I'd carefully check over the entire fork for cracks/defects. Do so before you hop on it again.
Is your headset adjustment loose?
Is your headset adjustment loose?
#3
500 Watts
Thread Starter
Join Date: Aug 2006
Location: Ann Arbor, MI
Posts: 833
Bikes: Trek 7200 FX ('05), Trek 6000 ('07)
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
No cracks no defects (LBS approved ^.^). I'm not sure about the headset adjustment. How can I check that?
#5
Senior Member
Join Date: Jul 2002
Posts: 727
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Sounds like brake chatter to me. The cheapest fix is new brake pads, Kool-Stop salmons are supposed to work well at eliminating chatter, but it's not guaranteed.
#6
500 Watts
Thread Starter
Join Date: Aug 2006
Location: Ann Arbor, MI
Posts: 833
Bikes: Trek 7200 FX ('05), Trek 6000 ('07)
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
I've been advised to replace my pads with Kool Stops before. I probably will get around to doing that in like 700 miles or so...
#7
Senior Member
Join Date: Jul 2005
Posts: 7,487
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 140 Post(s)
Liked 162 Times
in
89 Posts
Originally Posted by kill.cactus
I've been advised to replace my pads with Kool Stops before. I probably will get around to doing that in like 700 miles or so...
#8
Senior Member
Originally Posted by kill.cactus
My brakes suck, as some may recall from previous posts, but when I brake hard enough down this one 15 grade incline on my commute my fork really vibrates. This vibration causes the braking to seem weird (that is how I first noticed it). What will happen is that my brakes will operate normally and then every half second or so the front of the bike will like... I can't explain... Not jump but like have a small but sharp "knock" and the brakes will resume normal operation.
At first I thought maybe my front rims were messed up (like something was knocking against the pads or some irregularity or something), but now I can tell it is the fork.
This leads me to my question - how much vibration/flex is okay for an aluminum front fork? Mine will flex maybe 3/4 of a centimeter and vibrate under the most strenuous braking.
Thanks!
[edit] - the vibration's effects on the braking and weird knocks and stuff has been happening since I got the bike, and I don't think that the level of knocking actually could interfere with braking performance a lot so this isn't a life/death situation ^.^
At first I thought maybe my front rims were messed up (like something was knocking against the pads or some irregularity or something), but now I can tell it is the fork.
This leads me to my question - how much vibration/flex is okay for an aluminum front fork? Mine will flex maybe 3/4 of a centimeter and vibrate under the most strenuous braking.
Thanks!
[edit] - the vibration's effects on the braking and weird knocks and stuff has been happening since I got the bike, and I don't think that the level of knocking actually could interfere with braking performance a lot so this isn't a life/death situation ^.^
The reference is Cuthbertson's repair manual I quote: "Certain combinations of fork type and frame geometry can make flutter more of a problem. In my experience, round, thin-gauge, wide-diameter, straight steel fork blades with a short offset and fairly steep head angle, are more susceptible to flutter than other types of forks". His book was written in 1996 when alloy forks weren't quite the rage they are now. His advice if all else fails (toe-in, cleaning rims, checking headset preload, etc), is... buy a new fork.
Frankly, I wouldn't even look at a bike with "straight-through" forks.