Road bike front brake shuddering

Discuss light weight issues concerning road bikes & parts.
User avatar
WMW
in the industry
Posts: 855
Joined: Sun Jul 29, 2012 2:59 pm
Location: Ruidoso, NM

by WMW

Endoism wrote: Would it pose any dangerous problems to my full carbon Specialized fork? I can see it flexing back and forth a bit under medium braking (That's 'flexing' not rattling due to loose headset :) )


It isn't going to hurt your fork.

A slightly loose headset will not make a rattle... it will just be less stiff than normal. Make sure it is as tight as you can make it without restricting motion.

Is the issue happening only once per wheel revolution, or more often?
formerly rruff...

Endoism
Posts: 13
Joined: Sat Aug 13, 2011 2:29 am

by Endoism

nathanong87 wrote:u tried ur wife's wheel on ur bike

try your wheel on her bike

Yep, I did that - there was a tiny bit of pulsing/shuddering under brakes, but quite nelagible. Her carbon/alum fork is nearly 200g heavier than my full carbon fork. Perhaps that extra heft adds to it's stiffness

@MileHighMark
That would be a good cheap solution! Nice - ill give that a go before I do anything drastic. Thanks!

Endoism
Posts: 13
Joined: Sat Aug 13, 2011 2:29 am

by Endoism

WMW wrote:
Endoism wrote: Would it pose any dangerous problems to my full carbon Specialized fork? I can see it flexing back and forth a bit under medium braking (That's 'flexing' not rattling due to loose headset :) )


It isn't going to hurt your fork.

A slightly loose headset will not make a rattle... it will just be less stiff than normal. Make sure it is as tight as you can make it without restricting motion.

Is the issue happening only once per wheel revolution, or more often?


Cool, I rechecked and re-preloaded the headset bearings - still pulses.
I can't ascertain it's pulse frequency - it only pulses at higher speeds, so it's difficult to perceive. I'll see if I can grab an old tyre, paint a nice large bright reference mark in one spot and do some trial runs....

What were your thoughts to to the pulsing frequency?

User avatar
WMW
in the industry
Posts: 855
Joined: Sun Jul 29, 2012 2:59 pm
Location: Ruidoso, NM

by WMW

Endoism wrote:I can't ascertain it's pulse frequency - it only pulses at higher speeds, so it's difficult to perceive.


If the pulsing is due to the brake track being uneven in width in one spot (usually at the joint) it will be very noticeable at low speeds. Try it on a steep downhill while going slow.
formerly rruff...

User avatar
yourdaguy
Posts: 2206
Joined: Thu Mar 17, 2005 3:25 am
Location: Southern Indiana USA
Contact:

by yourdaguy

I had this same problem with a set of 7801 wheels I bought off ebay (now we know why he sold them). Both the front and read pulsed and I tried sanding the rims, etc. I finally decided that it was a variation in the hardness of the brake track. I found a new front rim on ebay that I guy bought for a project and never even laced it up. I relaced the front and it was fine. The rear pulsed less than the front and I just live with it. The wheelset has several thousand miles and the rear still pulses.
For certain parts stiffer is more important than lighter.

User avatar
theremery
Posts: 2673
Joined: Sun Jun 12, 2005 10:56 am
Location: New Zealand

by theremery

Double check that you don't have something sticky like Coke (dried) on the rim.....Wash it with lots of water and a few drops of detergent. BTW....Kinlin rims are Scandium enhanced, aren't they??...Cool stop SALMONS dude!!! (NOT Black!)....these pads (salmons) look after your rim. After you've tried water as your solvent, If this doesn't work, try a non-polar solvent (Benzene, thinners etc) and see if there is any difference.
Don't laugh re the coke....I had a mate who darn near killed himself with a sticky front rim......it took us ages to figure it out!! the rim looked (and felt) absolutely normal when having a look at it.
Updated: Racing again! Thought this was unlikely! Eventually, I may even have a decent race!
Edit: 2015: darn near won the best South Island series (got second in age
-group)..woo hoo Racy Theremery is back!!

User avatar
yourdaguy
Posts: 2206
Joined: Thu Mar 17, 2005 3:25 am
Location: Southern Indiana USA
Contact:

by yourdaguy

I think the 7801 rims were scandium enhanced also. I even wet sanded mine with a diamond whetstone (from my ski tuning tools) and there was no change. I wonder if scandium has issues with this?
For certain parts stiffer is more important than lighter.

User avatar
WMW
in the industry
Posts: 855
Joined: Sun Jul 29, 2012 2:59 pm
Location: Ruidoso, NM

by WMW

theremery wrote:Kinlin rims are Scandium enhanced, aren't they??


Niobium.
formerly rruff...

Endoism
Posts: 13
Joined: Sat Aug 13, 2011 2:29 am

by Endoism

WMW wrote:
Endoism wrote:I can't ascertain it's pulse frequency - it only pulses at higher speeds, so it's difficult to perceive.


If the pulsing is due to the brake track being uneven in width in one spot (usually at the joint) it will be very noticeable at low speeds. Try it on a steep downhill while going slow.


I think the pulsing is occurring more than once per revolution and decreases in severity when I'm going less than, say, 10kph...

The pinned joint is actually very very smooth without any sharp edges, so I'm pretty sure that's not the cause...

Endoism
Posts: 13
Joined: Sat Aug 13, 2011 2:29 am

by Endoism

WMW wrote:
theremery wrote:Kinlin rims are Scandium enhanced, aren't they??


Niobium.

Reckon I should still use Salmon pads?

Another update, I swapped with a mate's Ksyrium Elite front wheel, did a few Kim's and a variety of stopping pressures: nice and smoooooth... My mate also reported that there was a bit of pulsing from his Speedvagen ( with my front rim), but definitely not as severe as when he rode my bike with the shitty rim. So it sounds like that the full-carbon Specialized fork that I'm running, is also a bit flexy....

HillRPete
Posts: 2292
Joined: Tue Apr 12, 2011 8:08 am
Location: Pedal Square

by HillRPete

I didn't have great joy with Koolstop Salmon, on American Classic rims though. Plain black Swiss or Shimano pads are a good baseline, if they don't work, Salmon won't do any magic, as far as I experienced. Doubt the choice of pad will affect the shuddering much, in any case.

Endoism
Posts: 13
Joined: Sat Aug 13, 2011 2:29 am

by Endoism

I'd be happy if I could source AC 420 rims by themselves... I've had a set before and they weren't too bad...

HillRPete
Posts: 2292
Joined: Tue Apr 12, 2011 8:08 am
Location: Pedal Square

by HillRPete

Agreed regarding the AC420s, but there are lots of interesting (wider) alternatives these days.

User avatar
WMW
in the industry
Posts: 855
Joined: Sun Jul 29, 2012 2:59 pm
Location: Ruidoso, NM

by WMW

Salmon pads are recommended for Kinlin rims.

Have you thoroughly cleaned your rim and pads?
formerly rruff...

Endoism
Posts: 13
Joined: Sat Aug 13, 2011 2:29 am

by Endoism

WMW wrote:Salmon pads are recommended for Kinlin rims.

Have you thoroughly cleaned your rim and pads?


I cleaned my rims (hot water and Meguires car wash) and gave the brake pads a bit of a scuffing with some 100-grit and it alleviated the pulsing a little, but it's definitely still there. I've got a set of salmon pads coming soon - hopefully that'll help a little more...

As long as my full-carbon Specialized fork isn't going to snap on my and send my front teeth into the road, I'm relatively happy in just tolerating the pulsing since I like my White Industries hubs so much.. If worse comes to worse after a trial ride of Hotham at the end of Feb in preparation of 3 Peaks, I'll borrow a mate's Ksyrium wheel..

Really wish I had read more reviews regarding Kinlin rims BEFORE I bought them....

Post Reply
  • Similar Topics
    Replies
    Views
    Last post