Help with steering vibration

Help with steering vibration

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MrChips

Original Poster:

3,263 posts

209 months

Saturday 29th October 2016
quotequote all
Hoping someone might have some experience with having resolved a similar issue. It's a mk2 Tuscan, with upgraded discs (330mm front) and Ferodo DS2500 pads, both around 500miles old, with no serious use or trackdays etc.

Recently been having an issue with a wobble through the steering wheel during medium braking. Light or hard braking it doesn't show up so much, but under medium braking especially above 30mph, the steering wheel visually wobbles left to right. Car still brakes in a straight line, and you cannot feel any vibration through the pedal.

The usual culprit would be warped discs, or something wrong with the discs/pads however the discs are about 500miles old, and been checked with a DTI. Being the upgraded discs then i doubted they had warped.

So... what also needs to be checked? All bushes look good, so we're thinking maybe the track rod ends, or maybe even the rack itself.. would this vibration be a symptom of the rack failing?

so called

9,074 posts

208 months

Sunday 30th October 2016
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Sorry I don't have any suggestions right now but will do a bit of research.

dvs_dave

8,581 posts

224 months

Sunday 30th October 2016
quotequote all
Common with new discs and pads, and bedding the brakes in should sort it out. Warped disks are actually rare on any car. The usual cause is an uneven layer of pad material on the discs causing the wobble. Less noticeable on normal cars as there is more NVH insulation masking it.

To bed them in properly you need to basically do 10 hard stops (just before lockup) down to walking pace from 60mph. Accelerating at a normal pace back up to 60 between each run. This will get the discs and pads properly hot and deposit a nice even (and consequently vibration free) layer of pad material in the discs. Important that while doing this, don't come to a complete stop as then you risk depositing too much pad material on the disc where it stops rotating, causing a high spot, and then vibration.

Once you've done your 10 stops, just drive around enough to cool the brakes down to normal and you should then find your vibration has gone.

See here for an example of numerous sources giving similar advice.
http://brakeperformance.com/bedding-in-rotors.php
HTH

MrChips

Original Poster:

3,263 posts

209 months

Monday 31st October 2016
quotequote all
Thanks both but the discs were bedded in properly (pretty much exactly as you've just confirmed Dave thumbup)
And also been checked with a dti and they're not warped or have any high spots from what we can see. I'd also expect some vibration to be felt through the pedal if they are bad enough to cause the steering wheel wobble?

Is there any downside to maybe cleaning the discs and pads up and then doing the bedding in process again from scratch?

We're going to stick the car over the pit again and check all the steering linkages to be sure but I guess the only way to fully rule out the discs is to try another pair?! If that fixes it then hopefully I can get another set from the supplier as it shouldn't be happening after 500 normal miles frown

Or maybe I need to just send them back to be checked by the supplier on a lathe or something.

Edited by MrChips on Monday 31st October 17:56

Whitey

2,508 posts

283 months

Monday 31st October 2016
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I replaced my drag link bushes with poly ones which solved this on mine. Lot's of discussion on this in the Cerbera section.

so called

9,074 posts

208 months

Wednesday 2nd November 2016
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Whitey said:
I replaced my drag link bushes with poly ones which solved this on mine. Lot's of discussion on this in the Cerbera section.
I'm pretty sure this had to be done on my old Tasmin for the same reason.

TwinKam

2,937 posts

94 months

Wednesday 2nd November 2016
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Yes that.
This is a suspension/steering (ie wheel location) issue rather than a brake one. Check all bushes, ball joints, wheel bearings, rack etc for play, if all is acceptable then check the front toe setting ("tracking").

MrChips

Original Poster:

3,263 posts

209 months

Wednesday 14th December 2016
quotequote all
Right, this one is still ongoing.. found some play in the rack, and in the UJ, so have had the rack referred and replaced the steering UJ. Also changed the drag link bushes.... and our survey says... the vibration is still there.

There's no vibration at all when coasting or accelerating, only when braking.

To try to avoid just replacing the whole front end bushes.. I guess the next step just for my sanity is to swap the discs and pads off a known good car just to be 100% sure it's not the discs themselves. They're the 330mm upgrade kit from Dom although i understand that they're not selling them anymore. If it is the discs, then what would be the general consensus on how to deal with it? they've done 2k miles, no track work at all.

ClassiChimi

12,424 posts

148 months

Wednesday 14th December 2016
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MrChips said:
Right, this one is still ongoing.. found some play in the rack, and in the UJ, so have had the rack referred and replaced the steering UJ. Also changed the drag link bushes.... and our survey says... the vibration is still there.

There's no vibration at all when coasting or accelerating, only when braking.

To try to avoid just replacing the whole front end bushes.. I guess the next step just for my sanity is to swap the discs and pads off a known good car just to be 100% sure it's not the discs themselves. They're the 330mm upgrade kit from Dom although i understand that they're not selling them anymore. If it is the discs, then what would be the general consensus on how to deal with it? they've done 2k miles, no track work at all.
How are the calipers fixed to the hubs, any spacers/washers used at all?

I have the Brembo 324 mm brake upgrade on my Chim,
I had similar brake judder
Id fitted the calipers and new discs and pads, done loads of emergency stops to bed them in then went on a track day, only on track when braking very aggressively from high speed did I discover judder from the N/s front brake, steering wheel going left to right and almost out of control.

I'd used two 0.5 mm shims to centre the caliper to the disk,
I removed one of the shims,, makes very little difference as the pistons soon take up the slack
Added some 3M tape on the rear of the pads and started again.
I'd done at least 500 miles by now, I'd noticed that the outside pad wasn't pressing against the disc on the outside edge 15mm or so very effectively, after 1000 miles they had eventually worn and added material to the outside edge of disc.

It took a long time to get the discs to bed in but now they do not judder.
Fantastic brakes.

Do you get any brake squeal when there hot and coming to a gentle stop?

Some pictures of the brakes might be of help.
If it's only happening on one side I'd defo say it's the brakes, check for suspension/wheel bearing/track rod end movement while your at it.
Goodluck

ETA 2000 miles, ok, hmmm.
As mentioned above, I've noticed on a number of occasions the pads have left visible marks where I've come to a stop with warm brakes, once these big brakes bed in they should be deploying plenty of material into the discs as they operate so can we see a pic of the discs, I notice with my Chim that normal driving conditions the brakes are so effective I barely touch them and they still stop the car effectively, if I never did brake tests the pads would have hardly worn even with thousands of miles into them,
Check everything is tight and do the brake tests again, I tend to run my left foot on the pedal for a few swpeconds at a time, get them hot then do the tests, these big brakes are under employed in reality so you've got to get them really working on our cars to bed them in.
,

Edited by ClassiChimi on Wednesday 14th December 21:43

Incognegro

1,560 posts

132 months

Wednesday 14th December 2016
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[quote=ClassiChimi]
.

Do you get any brake squeal when there hot and coming to a gentle stop?


What does that imply. This has been annoying me for years. First on my 304mm CL pads upgrade and now on my 350mm upgrade and on the cp6600 calipers

QBee

20,904 posts

143 months

Wednesday 14th December 2016
quotequote all
Have you still got your original Tuscan disks and pads?
If you do, perhaps that would be the best test to try?
Perhaps controversially, in the absence of track days and track day speeds, i wonder whether you really needed the big brake upgrade anyway?

ClassiChimi

12,424 posts

148 months

Wednesday 14th December 2016
quotequote all
Incognegro]lassiChimi said:
.

Do you get any brake squeal when there hot and coming to a gentle stop?


What does that imply. This has been annoying me for years. First on my 304mm CL pads upgrade and now on my 350mm upgrade and on the cp6600 calipers
Squeal sort of implies vibration, harmonics are the audible sign.
I also had squeal, still do but very rarely now,
Vibration tape on the backs of the pads in congunction with liberal use of something like Mintex Ceratec on the parts of the pads that come in contact with the caliper body seemed to solve it on mine but I actually think it's because the pads are eventually wearing evenly, this has helped stop much of the squeal.

At the end of the day you have to get the pad and disc matched and wearing together if the pads are to hard you'll never get them working properly and much noise is likely to happen.
But all IMHO



MrChips

Original Poster:

3,263 posts

209 months

Wednesday 14th December 2016
quotequote all
ClassiChimi said:
How are the calipers fixed to the hubs, any spacers/washers used at all?

I have the Brembo 324 mm brake upgrade on my Chim,
I had similar brake judder
Id fitted the calipers and new discs and pads, done loads of emergency stops to bed them in then went on a track day, only on track when braking very aggressively from high speed did I discover judder from the N/s front brake, steering wheel going left to right and almost out of control.

I'd used two 0.5 mm shims to centre the caliper to the disk,
I removed one of the shims,, makes very little difference as the pistons soon take up the slack
Added some 3M tape on the rear of the pads and started again.
I'd done at least 500 miles by now, I'd noticed that the outside pad wasn't pressing against the disc on the outside edge 15mm or so very effectively, after 1000 miles they had eventually worn and added material to the outside edge of disc.

It took a long time to get the discs to bed in but now they do not judder.
Fantastic brakes.

Do you get any brake squeal when there hot and coming to a gentle stop?

Some pictures of the brakes might be of help.
If it's only happening on one side I'd defo say it's the brakes, check for suspension/wheel bearing/track rod end movement while your at it.
Goodluck

ETA 2000 miles, ok, hmmm.
As mentioned above, I've noticed on a number of occasions the pads have left visible marks where I've come to a stop with warm brakes, once these big brakes bed in they should be deploying plenty of material into the discs as they operate so can we see a pic of the discs, I notice with my Chim that normal driving conditions the brakes are so effective I barely touch them and they still stop the car effectively, if I never did brake tests the pads would have hardly worn even with thousands of miles into them,
Check everything is tight and do the brake tests again, I tend to run my left foot on the pedal for a few swpeconds at a time, get them hot then do the tests, these big brakes are under employed in reality so you've got to get them really working on our cars to bed them in.
,

Edited by ClassiChimi on Wednesday 14th December 21:43
Thanks for the reply smile

The callipers have the slightly larger spacers needed to accommodate the discs yes. These were skimmed when fitting as they were originally a bit too big.


Here are the pads when i first took them out. I did notice that it looked like the inside pad on the drivers side wasn't cleaning the disc quite as much when just moving the car in and out of the garage.




The callipers have since been off and been checked over and are all moving freely so maybe it could be something relating to the spacers. The effect i'm seeing is exactly as you described, with the steering wheel visibly wobbling left to right under braking. I can take my hands off the wheel, and the car still brakes in a straight line though.

The car is with a well known garage who i trust fully, but they obviously don't want to simply throw parts at the car so are trying to help me keep the bill down! I was gutted when they drove it after doing the rack and the UJ that it was still there but at the end of the day this is one niggle that i can't ignore nor fix myself.
All bushes etc have been checked.. i did wonder about the wheel bearing, but that would show other symptoms when driving normally i would think? same for any wheel imbalance? (only done 1k since this was done last as well)

I gave my old discs to a PHer but they've been kept outside, plus these were new discs and pads at the same time so would be bedded in together. I think the only way of testing the brakes is going to be finding someone willing to swap theirs onto mine to test for a couple of miles. There are a couple of people locally within our Berkshire region who may help but i can understand it's a tall ask!


QBee said:
Have you still got your original Tuscan disks and pads?
If you do, perhaps that would be the best test to try?
Perhaps controversially, in the absence of track days and track day speeds, i wonder whether you really needed the big brake upgrade anyway?
Sadly not an option to refit the originals, and i do understand the point about needing the bigger brakes, but the cost difference wasn't huge (the old ones needed changing really anyway) , plus i have taken it on track in the past.. just not since fitting these discs.

Edited by MrChips on Wednesday 14th December 22:54

ClassiChimi

12,424 posts

148 months

Wednesday 14th December 2016
quotequote all
The disc wear pattern can tell you a lot!
If you look at a disc that's had a well matched pad working on it, you'll,see the same scrapes into the disc and the small deposits of break pad compound like dots of black all over it, as the pad hits the disc these small deposits that have been ground into the disc at heat start that the process of cutting the disc again and that's what stops you. If you don't get the compound to sort of bind with the disc as it's cutting then they won't work well.
So as the brakes heat up the brake pad should be slowly transmitting its compound onto and almost into the disc,
When this process has been completed all over the disc and pad in an even fashion you have good brakes.

If your pad compound is not getting the correct temp for its best application then you've got problems.
I have a road based disc and pad, so they work effectively on the road and get upto the correct temps easily and immediately from stone cold.
If you've got a pad with lots of metal in it it's also likely to squeal, the cost of aggresive brakes I suppose.

As the O/P has taken serious attempts to solve this I'm just sharing my personal experience of very big brakes and brake judder.

By removing one 0.5 mm shim on the N/S two caliper bolts on my car helped a lot!
Any added shims (if used by O/P ) should be looked at closely, there's a huge amount of energy going through these things, anything that can create harmonics should be omitted if possible.
.

MrChips

Original Poster:

3,263 posts

209 months

Wednesday 14th December 2016
quotequote all
Yep, it's definitely a weird one.. Trouble is.. brakes have been fine for 2k miles.. this behaviour came on fairly quickly.. over the course of around 40miles. The pads are Ferodo ds2500 which i've had before, so not overly track focused, but i do drive reasonably quickly on the road.
It's a good shout on the spacers, although the callipers have been off and on twice and the issue is still identical but i'll suggest they take a look at the spacers themselves.

This is rapidly becoming the 2nd most annoying issue i've had with the car.. although it'll take a lot to make to the number one spot above the phantom dashboard squeak (i've fixed it with earplugs smile)

ClassiChimi

12,424 posts

148 months

Wednesday 14th December 2016
quotequote all
MrChips said:
Sadly not an option to refit the originals, and i do understand the point about needing the bigger brakes, but the cost difference wasn't huge (the old ones needed changing really anyway) , plus i have taken it on track in the past.. just not since fitting these discs.

Edited by MrChips on Wednesday 14th December 22:54
Funnilynenough quite similar to my Brembo pads smile

Your photo shows the bits of metal in the pads, the more metal the hotter and the more they'll cut into the disc.

They look like a road pad to me and you can see the corresponding grooves in the pad that should be the same and totally even allover the disc.
Mine came about because my N/s caliper when bolted up to the hub sat slightly closer to the inside edge of the disc, the o/s sat higher and the pad gripped the outside edge of the disc from day one and was excellent,
The N/s it took many miles to wear the inside edge of the disc down until the whole pad now contacted the disc and then I had even wear.

Your pads look ok to me but how old are they, have they had a cold winter then used in summer, slightly breaking up on the edges, but they do look like they've been biting into the discs, not sure f you've done enough miles on them,
If the cars running, go and drive around with your left foot on the brake, get them really working, not to hot but enough to get the pads and discs to cut into each other.

Some more pictures of your set up would be interesting,
Someone's checked you haven't got a ball joint or wheel wobble issue, balancing or out of shape wheel?

If you can get a pic of the spacers etc, what thickness have been used, what can you get away with, you can offset the caliper from the disc by a fair bit really, good few mm, just push the Pistons in further on the one side and one brake test will centre the pads. This way your getting away from spacers, the less the better.

I'd be taking the caliper etc off and starting again, do you have a bracket that connects caliper to hub, this is where the problem may lie, how is your bracket bolted to the hub.
I can't really picture your brakes so I'm just guessing.
Many a good mechanic come on these forums, hopefully someone will come and give good advice.

ClassiChimi

12,424 posts

148 months

Wednesday 14th December 2016
quotequote all
MrChips said:
Yep, it's definitely a weird one.. Trouble is.. brakes have been fine for 2k miles.. this behaviour came on fairly quickly.. over the course of around 40miles. The pads are Ferodo ds2500 which i've had before, so not overly track focused, but i do drive reasonably quickly on the road.
It's a good shout on the spacers, although the callipers have been off and on twice and the issue is still identical but i'll suggest they take a look at the spacers themselves.

This is rapidly becoming the 2nd most annoying issue i've had with the car.. although it'll take a lot to make to the number one spot above the phantom dashboard squeak (i've fixed it with earplugs smile)
Dashboard probably requires more Velcro or the nuts need tightening.

Oh crikes, this is a Tuscan, ain't s clue sorry frown

So your brakes, what are they and for what car originally.

If they are a race derived brake then there's a good chance they'll clatter and or whine frown

The securing clip looks very similar to my Brembo's which looks a goid sign, as they have two securing pins that's another source for vibration so I cover them in brake grease.


Brembo 324 mm Ford Focus discs using Brembo BMW E38 Brembo road pads
Here's a pic of them new.
I'll try and get a shot of my discs as they are now for reference smile



[url]



|http://thumbsnap.com/zkkgWgiF[/url]

ClassiChimi

12,424 posts

148 months

Thursday 15th December 2016
quotequote all
N/s disc after about 600 miles, notice the lack of wear on the outside edge and compared to the O/s disc below you can see how the N/s disc the pad cuts into the disc closer to the wheel centre line, I had brake squeal and judder until the N/s disc had worn this and the pad down (about 1000 miles ) road use, it eventually started cutting into the outer edge of the disc and now it's uniform wear across the whole disc. Gosh does any of that make sense!

N/s




O/s


You'll notice the small lip on the o/s disc of about 1.5-2.0 mm on the inner edge, the caliper holds the pads slightly higher up the disc so it presses more firmly across the disc, once I'd done this rather long bedding in and got the same wear on the N/s it resolved itself as much as anything I've done.

What's important to note is how the inside pad is wearing as opposed to the outside, my brakes juddered because the inner pad was bedded and working well but the outside pad was not, you can imagine the Pistons pressing evenly but the pad grabbing better on the inside so causing an imbalance and vibration.

The two pics are taken at the same time, o/s bedded and working well,
N/s not so!

I will take a pic of them now as those were taken a good 4000 miles ago
I now have what looks like even disc wear on both sides and they appear almost identical and don't judder or make any noise.
It's all a combination of factors, plenty of grease and pad tape,
As few shims as possible,

Maybe there's an even more road based pad than the Ds that might help.
We really need to see a pic of both sides of the offending disc to assess wear pattern.

Ps, my wheels would also stay in line and the car tracked pretty good even with this imbalance under braking.
Here's a thing, sounds extreme but it worked???
Once this process took its course and my brakes became very even left and right, I'd lock the N/s brake up everytime just fractionally before the right side, I raised the ride height just a few mm on the N/s front and lowered the O/s rear and all of a sudden no locking of that wheel and brakes come on evenly both sides now.
Geo is also important so I'd be getting that checked out.
Even though I have access to scales I've not corner weighted my car yet!!
I used to also lock the o/s rear brake up and that's a bugger,,,, the ride height adjustment has also reduced this rear wheel locking up.
Using the out riggers as a way to set ride height is a best guess and until I've corner weighted my car I don't actually know how the weight sits on each corner.
I've obviously evened it up with my ride height change,,, it took me at least two upyears before I worked this out, the brakes would also lock up the same way with the standard brakes!

The ride height levelling is what has stopped uneaven braking and premature lock up.

Hope some of this helps frown

I think these brakes are so sensitive if any things not quite right you'll know about it.


Edited by ClassiChimi on Thursday 15th December 08:26


Edited by ClassiChimi on Thursday 15th December 08:29


Edited by ClassiChimi on Thursday 15th December 08:39

ClassiChimi

12,424 posts

148 months

Thursday 15th December 2016
quotequote all
I'm obsessing hehe
One more brain wave,, with the Chim hub it's not the most level surface to bolt to,
Mine are tapped out, bolts screwed through then a half depth nut screwed on to the bolt end on the inner face of the hub, pinching it all together, plenty of locktight as it also acts as an anti vibration tool ( my instinct ? )
Torque setting, FT!
Tight.
I've been working all night, I'm back at 1pm, better get the feck off here thumbup

Mr Chips, I'd really like to see your front hub assembly that's on your Tuscan, that'll start another debate in itself hehe

I've just remembered another thing
When my brackets were mounted to the hubs, the calipers would catch here and there, I rubbed the hub down slightly to get clearance, you don't want any binding or pressure being applied anywhere especially as your tightening them up.
Errr, it was the brackets slightly catching the hubs not the calipers, combination of filing down the bracket/hub sorted it. smile
The bloody hubs, it's also very easy to get a bolt out of alignment especially when or if they've been drilled out, if that's not square top to bottom, issues!
I was very careful to drill mine so they were uniform, the hub face isn't exactly accurate either, if there's any twisting or odd pressure being applied to the bracket when it's being nipped up it's likely to vibrate.


Did you fit these brakes Mr Chips,
I've learnt you have to get them spot on or something will show up.

By applying lots of grease to the pad where they sit in the calipers so where harmonics are going to get transmitted through helps hugely.
I've seen and heard many a Ferrari or Porsche or any other great car with brilliant brakes and they can all squeal,
The nature of the beast as there's a number of points where vibration can take place, pad compound is the most likely cause in most cases, you want instant massive braking power then big surface area and aggressive pads are a must, slow speed squeal is about the wrong temps in the pad and disc for that application, that's my guestimation anyways, that and the size of them. scratchchin

PPS hehe
Once you get these big brakes working they should make you feel like your driving a far more expensive car sort of thing.
It's the sensitivity and light pedal touch, just a small foot pressure adjustment is instantly replicated in braking force, I could dance with lock up like abs I reckon, fk my tyres but hey hehe
Edited by ClassiChimi on Thursday 15th December 09:23


Edited by ClassiChimi on Thursday 15th December 09:28


Edited by ClassiChimi on Thursday 15th December 09:39

Incognegro

1,560 posts

132 months

Thursday 15th December 2016
quotequote all
QBee said:
Have you still got your original Tuscan disks and pads?
If you do, perhaps that would be the best test to try?
Perhaps controversially, in the absence of track days and track day speeds, i wonder whether you really needed the big brake upgrade anyway?
If that was for me mate, Im a Cerbie... the big brakes were done in anticipation of going on to enjoy the car at track days etc. After hearing all views Im leaning the squeak towards the lack of some sticky pads applied to the back of pad (I was told they were built into the AP branded ferodos Im running on the front). The slight wobble may have been caused by a slight 'moment' I had of energy stopping?