Vibration, starts when braking, only at high speed

[andydclements]

I think it's time I got the S3 sorted, so I've one thing meachanically that i haven't managed to sort.

If I brake from any speed below 70mph, everything's fine, no matter how hard or soft Ipsh the pedal.

If I brake from more than that, I start to get a judder, but it stays all the way through the braking action, so right down to the point at which the car stops.

I've done a lot of work on the front to cure this and another previous problem, here's what I've done.

To find & fix the slightly wooly steering, and tendancy to wobble the steering under braking I replaced the

universal joint

wheel bearings

brake discs

brake pads (couple fo times, different brands)

lower wishbone bushes (twice, the guy putting the rubber set in first mucked one up, so I then put in poly ones from SJ)

upper wishbone bushes

anti-roll bar mountings

anti-roll bar to wishbone bushes

steering rack.

Parts re-furbed include

calipers.

hubs checked for run-out (and cheked discs as well).

One of the last jobs I did was to replace the ARB to wishbone bushes, if you can call them that, the foam bits that look like packing material. I think this was at the same time as things like the rack, ARM mountings etc.

This work cured the initial problem, the steering felt better than ever, the car and stering wheel didn't wobble under normal braking, but it left me with a new problem. The vibration mentioned at the start of the message. I haven't done anything with the car for quite a while, but the TE will soon be back together (fuel tank issues sorted), and I want to get on with the S3 over the winter.

The vibration is very violent, I feel it most through my feet , well right foot actuallly as it's the one touching the car, but it can be felt on any part of the passenger compartment, and that makes me think it's something making the chassis resonate.

One thing I'm not certain of is the chamfered washers on the ARB to wishbone area, I don't recall any washer being differen to the others (OK, I din't look and didnt read the manual).

Has anybody ever pulled this area apart, did theirs have one washer that was chamfered?

Do people think this being replaced with a flat washer could cause the washer to hit the wishbone, under braking, and start vibration?

Andy

[bigsi]

andy its the calipers and discs, same as mine im afraid.

i spoke with pete at pnm about mine as mine fade badly and i get wobble when braking even though mine were refurbed, he did explain why but i cant remember, so much so that im getting a 4 pot upgrade off him and new discs. the girlings just are not up to the job anymore period.

give pete a call he can explain better than i can

simon

[hilly]

I take it your S3 is an early Triumph upright based car ?

If it is then one of the arb washers is chamfered.

The chamfered side goes on the outside up against the arb where it transitions from thread to solid bar, if you look at the arb there is a matching raised are it fits around.

Not sure why it is like that, maybe put in like that to eliminate a stress riser a sharp edge would cause, just a theory.

Need to think about the vibration ?????????

Hilly

[andydclements]

andy its the calipers and discs, same as mine im afraid.

i spoke with pete at pnm about mine as mine fade badly and i get wobble when braking even though mine were refurbed, he did explain why but i cant remember, so much so that im getting a 4 pot upgrade off him and new discs. the girlings just are not up to the job anymore period.

give pete a call he can explain better than i can

simon

I'd agree if I had either fade or wobble, or if the calipers were showing any issues, or marks on the discs.

That , coupled with the fact the vibration started after I sorted the other problem, but hadn't touched the brakes that time, makes me thing it's something else.

Andy

[matk]

I know Pete Gentilli had some awful vibration issues and renewed just about everything he could think of at the front end. Turned out to be worn engine mounts. Long shot?

[iainskea]

Andy, you said you replaced the universal joint - only one of them?

My car model has an upper and lower UJ, and the lower UJ is the subject of many topics re vibration as you describe. In fact, I have a lower UJ in my hot little hands right now, just arrived from Lotus UK for fitment this weekend. The symptoms are more in the steering wheel than the feet, but a 'judder' none the less.

Iain

[cly_mitchell]

Andy,

I just went though a brake problem. It was more of a grabing sensation except in a turn then the inside wheel grabbed badly. Wayne B sent me a pm insisting that the factory brakes were more than able to stop the car well under any condition other than heavy track use. I too have all new front end parts as well as calipers and pads. It turns out my arb was short threaded and there was a space between the washer and the lower control arm. I installed a spacer to eliminate the gap and my brake problems have subsided. I think my arb was re-threaded at some point as the threads were SAE and this space is not in the parts manual.

This is just my experience. I believe Wayne B to be "the man" in the G-TE (if not for all cars) if he says the brakes are good enough I will take his word for it and look elsewhere for the problem.

Cheers

Clay

[esprit22]

Had a similar problem with mine, turned out to be a shagged front shock. For the cheap price they cost, it's well worth changing them both with new top rubbers as well.

[PVK 596Y]

Had a similar problem with mine, turned out to be a shagged front shock. For the cheap price they cost, it's well worth changing them both with new top rubbers as well.

Its worth checking front AND rear discs for run-out when they are on the car.

Paul.

[andydclements]

Thanks guys, I think , by these posts I'm going to have to look at the ARB, it's mountings etc again.

Yes I did only replace 1 UJ, the upper one was perfect, the lower one was completely s****ed.

I'm not getting the traditional side to side wobble/ vibration, of the steering/ wheel / car, it's s VERY pronounced vibration, too fast even to be brake discs warped (but I have checked them all anyway since it costs nothing).

And, it did start when I replaced bits and re-fitted the ARB, so I'll have to check threading, correct washers etc.

Thanks for the suggestions guys

Andy

[andydclements]

I eventually looked at the ARB mountings, and found my short term memory while putting them together last time must have been really bad.

I remember getting the old ones off (took the main pivot bolt out to make it easier, and muttered about the state of the distance tubes (rusted very badly), I remember struggling to fit it all back together. I was sure I'd put the bits all back on with new bushes, and sure there were no "chamfered washers", all flat ones.

So yesterday the new poly ARB to wishbone bushes arrived from SJ (only ordered late Friday afternoon), unfortunately only one chamfered washer but I decided i would make one from a flat washer if I had to. this time I removed the ARB from the chassis mounts to make it easier than removing the wishbones. To my surprise I found the chamfered washers were there, but no distance tubes. I must have thought I'd put them on and not remembered to push them through the small hole in the wishbone once the ARB was through.

Without the tubes it mean the foam bushes were compressed too much and the washers on the ARB were able to cut through and touch the wishbones.

Not sure if this is going to cure the issue, but it could well have been the problem, it's when I did the ARB along with a few other things this vibration started to occur.

Andy

[USAndretti42]

Hope you've found your fix, Andy. When you brake you do put the lower, front wishbone leg in tension which could have led to metal-to-metal, or nearly so, contact so that could be it.

[andydclements]

Hooray.

It only took 18 months to sort it out. OK 12 or so months of nothing didn't make it a fast fix, but it was all down to 2 stupid little bits of steel tube that I forgot to put in when I was on my back struggling to get the ARB on.

I know I still have the slight brake disc issue to sort, but I've got another hub to try and do that, the main concern was that brake disc warp/ hub warp etc couldn't cause the metallic vibration.

One thing I spotted while I was under the car putting it all back together, I have 8 spacers for each ARB mounting , the ones used to adjust the castor, I'm sure the manual says up to 4, maybe I'd better check the alignment at some point.

It was fun driving it home from the MOT station this evening, I haven't driven anything other than the Excel for few weeks, other than to the MOT station and back, and that was going to be a gentle drive as I couldn't guarantee the car was road-worthy.

[iainskea]

Nice Andy - what a great read through many possible faults and eventually find the cause, well done.

If it wasn't fixed I was going to suggest you get the shocks checked on one of those electronic testing stations that spins up your wheels and prints off the results under light and heavy braking.

Iain

[andydclements]

I klnow it's been a while, but I decided to have a play with the S3 today.

It seems the final bit of the puzzle falls into place. By replacing the distance tubes on the ARN mount I managed to get rid of the worst of the vibration, but it had still left the braking judder which set the resonation off. I took the hubs off and checked for bearing issues, despite not finding any damage to an visible surfaces and it being new grease I found some flakes of shiny metal in the grease, so I can only guess the surface of the cone on one of the races is starting to brake up after 50 miles or so (I plan to go and get some SKFs this week rather than the stuff the closer bearing supplier has), In also thought about the pads, I had Apec in there on the first re-build, I'd swapped to EBC Green and now I've put Power Train in. Despite the potential bearing issue and a couple of thou run-out on the discs it's nearly all fine, so I'm going to replace a couple of bits and hopefully it's all sorted.

SimonF, do you want to see how yours should handle?

[lotusvette]

hi, if you go down the skim the disc route, it could make you think its something else, a mate of mine with a audi had a shocking braking and wheel problem , had them skimmed and it was just as bad so he looked elsewhere on the car, i wasnt convinced so i bought some new discs and pads for him, fitted them while he went shopping, when he came back he took it for a spin, cured--it had a slight pull to the left but that was tyres, funny though ,back in the 70s, disc skimming was common place in lots of garages, take it to a mot station and see if they could spin it up on wheel brake machine, might just see something,steve