Juddering when braking

[vorsprung]

When I'm going fast on a steep downhill for instance if I pull on the front break quite hard the bike judders
I noticed this after a steep descent ( down the hill to the awlsicombe pub, Ian) I then did the rest of the ride only using the back brake 

To be exact the front fork flexes as if the brake is snatching on and off

The front wheel isn't very true.  I am not very good at that sort of thing 

Could the juddering be caused by the wheel not being true?

It does judder a little at lower speeds but I guess then there isn't so much energy in the decelloration so there isn't so much energy in the judder

I haven't ridden the bike for 12 weeks since my crash.  I have used it on the turbo though.  Before the crash the wheel wasnt very true either but I don't remember it juddering.  My crash happened during heavy breaking on a hill

I'm gonna have another go at truing it tomorrow anyway

hmm also I could swap in a wheel from another bike see if it still does it

[clarion]

Could well be the front wheel being untrue.  When you've sorted that, make sure the brakes are toed in correctly.

And there's never any harm in checking the headset is tight.

[Adam]

Speaking of headsets, I had a very similar juddering when using the front brake on my commuter which got worse throughout last year.  Eventually I got round to searching for the reason.  Although the headset was done up perfectly tight, all the ball bearings inside were dry as a bone. 

I guess 10 years of not being touched might have something to do with it..................

So, a big dab of grease all round, and no more juddering.

So check you're properly lubricated. 

[clarion]

Um yeah - that'd def be the next thing to check if the three things I mentioned don't stop it.  Dry bearings, or pitted races.

[Jacomus]

Could also be as benign as you have dripped a small splodge of oil on your rim.

[Biggsy]

Assuming rim brake.........

An untrue wheel can cause a sort of juddering or uneven braking.  Certainly true the wheel if you can.

I wouldn't worry if it only happens when the rim is wet or contaminated with oil or dirt, but something is more seriously wrong if it happens with a clean and dry and true rim, too.  Check for play in the caliper arms, and excessive play or flex anywhere else on the bike.  A loose headset can produce a knocking or juddering sensation under braking if it's very loose.

[Paul Smith SRCC]

If it is it a recent development then something has caused it.

Some combinations are worse than others, some drop bar 700c road bike forks with cantilever/v brake calliper for example do occasionally get feedback that the fork judders. Often although this is not good news by making sure you use both brakes it is liveable with, some riders use one of their brakes more than the other, changing their braking style often helps.

I mention this as perhaps you fall into the category and it is only when you did indeed brake aggressively on down hill stretch that it flagged up this problem, in any event it is worth paying attention next time you ride to see if you do indeed do just that.

Paul_Smith
www.bikeplus.co.uk

[tiermat]

I have had this on my MTB and it turned out to be loose stancions on the sus forks causing flat spots on the rim which made the situation worse to the point where I got juddering even at low speed.  When I looked at the rim I saw that patches of the TCC coating had worn off which would have made the braking worse, even if I had replaced the forks, if I hadn't replaced the rim.

Sold the complete bike in the end so it's SEP now...

[Hot Flatus]

I've had this. Check for headset play, and check that caliper nut is tight.

[vorsprung]

It's not a loose headset

This was the first thing I checked because I've had that happen before on another bike

I trued the wheel as best as I could.  Although the wheel now is much truer laterally it still seems to have a "hump" and there is a problem with the vertical truing.  The wheel does have a small dent in the rim.  It is possible this is crash damage but I doubt it

I went for a test ride and the juddering still happens - it is slightly less severe

Then I wondered if it was the mudguards.  If the wheel has a bulge then it might rub on the mudguard during breaking when the fork flexes.  I removed the mudguards.  Still judders.

Then I switched wheels.  No judder.  It is definitely the front wheel.  So I need to get it fixed somehow.  Any tips on truing?

[gonzo]

I've experienced something exactly the same.

Basically I'd worn the rim down so much that the braking surfaces had become concave and at one point, the rim was beginning to fold open.

Run your finger around the braking surfaces and check to see if the surface is curved. If the outside of the braking surface is beginning to bend open, then simply don't ride the wheel again. It's really not safe as it could easily explode when you next ride it sending shards of metal everywhere.

[Wowbagger]

Are the brake blocks fitted the right way round?

I had some judder, especially in the wet, on one of my bikes and close inspection revealed that the blocks were indeed back to front.

[Biggsy]

Depends what this "small dent" is.  If it is an actual small dent in the rim from impact then then you won't remove it by truing.  It's unlikely even that a repair by hammering or bending with tools will leave it good enough for baby-bum smooth braking.

Park Tools have some notes on truing here. But I get the impression, vorsprung, that you already know how to true a wheel.  If you can't get the wheel sufficiently true by normal methods then I would replace the rim.

[Ian H]

Then I switched wheels.  No judder.  It is definitely the front wheel.  So I need to get it fixed somehow.  Any tips on truing?

Bring it to Awliscombe.

[Wibble]

Last time this happened to me it was a loose headset.  Hold the front brake on and rock the bike backwards and forwards.  If you can 'feel' a knock then it's the headset.

[Paul Smith SRCC]

Then I switched wheels.  No judder.  It is definitely the front wheel.  So I need to get it fixed somehow.  Any tips on truing?

Do you have a computer fitted? If yes make sure the wheel magnet is near to the valve hole, most rims are slightly heavier at the join, which is normally opposite the valve hole. Only a small point but it can be enough to make a difference. Some rims even have a wheel balance that slots into the valve hole for this very reason.

If wheel is running free lift front of ground, spin wheel and see where it comes to rest, it should stop with the heaviest section at the bottom, normally this will be the join with the valve at the top, even if the tyre, tube and valve cap are fitted this will still often not be enough to counter the weight of the join. To demonstrate remove wheel, spin it, hold each end of the axle and you will feel that it is not a constant force spinning and indeed it is often quite significant, you will then realise how this can actually effect the handling.

Paul_Smith
www.bikeplus.co.uk

[vorsprung]

Then I switched wheels.  No judder.  It is definitely the front wheel.  So I need to get it fixed somehow.  Any tips on truing?

Bring it to Awliscombe.

Thanks!

What day/time is good for you Ian?  I am currently not working so any time is good for me

[Ian H]

Bring it to Awliscombe.

Thanks!

What day/time is good for you Ian?  I am currently not working so any time is good for me

I'll PM.

[nuttycyclist]

The simple test, for me, is to run the fingers round the rim. Is there a "dink" there (e.g. where it's hit a pothole).

That has more of a juddering cause than an out of true wheel.

[Wobbly John]

It's also worth checking the forks, especially steel ones. I had judder on my hack bike which I couldn't identify, and it eventually turned out to be the fork blades cracked at the fork crown. 

I found out when the forks sheered off when I bunny-hoped a 1" dropped kerb at about 20 mph. 

I slid about 40 yards on my shoulder.  

[clarion]

It's also worth checking the forks, especially steel ones. I had judder on my hack bike which I couldn't identify, and it eventually turned out to be the fork blades cracked at the fork crown. 

I found out when the forks sheered off when I bunny-hoped a 1" dropped kerb at about 20 mph. 

I slid about 40 yards on my shoulder.  

Especially steel ones, because aluminium or carbon would have given you a free face plant before you got the chance to wonder what the problem was...

[vorsprung]

The simple test, for me, is to run the fingers round the rim. Is there a "dink" there (e.g. where it's hit a pothole).

That has more of a juddering cause than an out of true wheel.

Yes there is a dink

[vorsprung]

Ian had a look at it and got it straighter than I could by hitting it with a hammer and stuff

The dink is more than a dink it is a mashed rim

The wheel still judders under braking

I guess I need a new rim

[Ian H]

It's round and true for 95% of its circumference, but the remaining 5% takes a short cut straight across. Still, it was an excuse for a cup of tea and a chinwag.