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car: 95 850 2.5 20 valve auto, milage 100k
Problem : braking from 70 down quite a 'sharp' vibration and noise. Not detectable under 40 or so.
History : 18 months ago circa 30k ago both front calipers and discs and pads were replaced to cure sticking calipers - genuine volvo parts i believe.
3 thousand miles ago the front calipers were stripped and cleaned, disks and pads inspected (8mm left on all pads, disks well within tolarance) and everything put back together - note torque wrench used for all assembly. (by me)
1700 miles ago one rear caliper was replaced (sticking) along with both disks (brembo) and all pads and handbrake shoes. (by me)
Rear tyres are 40k old and half worn, one front tyre is 5k old the other was replaced 1000 miles ago (tyre fitter witnessed to use torque wrench to re-apply wheel!).
The problem started this morning, and is - i think - getting very gradually worse I have done 150 miles today)
On the way home tonight i stopped and tightened all the wheel nuts using an 18" extending wheel wrench, although i put 1/4-1/2 a turn on all the nuts nothing felt loose or of a particualrly difernt torque (nor overtight for that matter). This didnt effect the problem at all,
There is not really noticable pulse in the pedal or shake in the steering wheel.
All wheel have been felt by hand an none seem hotter than their opposing number on the other side of the car (fronts warmert than rears naturaly).
Now i have never had warped rear disk and thats ny first thought (due to it happening durring braking and the nature of the vibration - it really feels quite sharp, i would expect a warpesd front to be damped a bit by the sliding pin arrangement of the caliper)- has anyone else and did it feel as I am describing?
My betting is a warped disk (possiby a warped alloy though i dont know why...) or possibly a wheel out of balance (though it feels to much for that it really gets your attention!).
The plan is to do the following on each wheel in turn:-
Jack up the car
Use a dial guage to check run out on the ront surface of the alloy
remove alloy
Use dial guage to check run out on disk
If I find run out on a disk i intend to remove, clean all maiting surfaces and reseat and check again...
any thoughts, advice or sugegstions for other causes/checks i should do greatfully recieved..
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ok im not goign to be looking today the wheel lock security key thingy just crumpled trying to remove the studs (i said one or two naughty words!)
new locking wheelnuts from volvo tomorrow, locking wheel nut removal tool also ordered in...dont you just hate it when jobs just get more and more complicated!
anyway i can see a 'print' left by one of the brake shoes on one of the rear disks....but reserving judgement till i can get the wheels off and put a dial guage accross them....
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If the vibration is only happening while braking, then it is not a wheel out of balance. Do check the tire pressures, espcially the rears.
If you didn't replace the caliper yourself, you might want to bleed it to make sure all of the air bubbles are out of the line.
Because you do not feel the vibration in the steering wheel, it needs to be one of the two rear brakes or a bent suspension piece - find any really good pot holes lately?
Klaus
--
(V♂LV♂s 1975 164, 1995 854T, 1998 V70R)
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Hi Klaus,
yes the vibration is only happening under braking...i had good look at the tyres an they look & feel fine (will check with a guage tomorrow but my thumb test says they are both about the same!)
I replaced the caliper myself and presure bled the whole system with 2 ltrs of fluid so i dont think there is any air in there..there is no spring in the pedal.
Cant say i have found any pot holes recently..certainly not enough to bend suspension....and I had the tracking done last week (about 1000 miles ago)
I think its a rear disk, the question being as i replaced them about 2000 miles ago with brembo disks (so not cheap ones) and torqued the wheels up with a torque wrench WHY would one warp so qiuckly - there isnt even any clear wear on them yet!
the dial guage will tell for sure, but i dont want to replace to have the same thing happen to another set of new disks!
the sensation when it happened felt rather like it does when ABS is kicking in...in terms of the speed and sharpness of the event, but ia m sure it wasnt because (a) thats a distinctive sound and (b) the brake pedel wasnt pulsing....
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Wheel nut torque is critical to keep rotors true on volvos. The key part is making sure all the wheels are tightened to the same torque. This means one must use a reliable and accurate torque wrench whenevr tightening wheel nuts. I think by using your extending wheel wrench you may have caused this problem, a human is never as accurate as a machine at this. I always go over every nut with the wrench to make sure they are the same tighness after they have all been tightened as sometimes the first one or two nuts may not have been tight because the wheel might have been slightly crooked. as for the shop that tightened them did they use the right torque? Some shops (most I think) use one standard torque setting on their wrenh for all vehicles. This can cause overtightening of the nuts as volvo is one of the lower torques. I wou;d remove all the nuts and retorque them to Volvo specs (with the wheels off the ground). I hope this helps.
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uhmmmm...
i used the wrench only AFTER the problem was getting worse and worse to chek the nuts were all fairly even....
they were initially tightened with a known torque wrench by myself to volvo specs...except the front left which was tightened with a toorque wrench at my tire suppliers who i know from past experiecen and observation this time sets their wrenchs each time (and i have perviously checked that its the right setting)...
also my hand extending wrench tightening tells me by 'feel' that those nuts were about right...and all pretty much equally tight....
i agree hand tightening is not ideal but you will understand being in a motorway services faced with a a lot more miles i really wanted to make sure the bolts WERE tight and all pretty even....which they were, also i believe the real enemy is the airpowered guns that can really over tighten just one or two bolt...that the torque setting is equal on all 5 bolts and brought up slowwely across the bolts tis the really crucial bit rather than the precise setting is my unederstanding (within reason of course!)
btw you should never do the final torque for wheels up off the ground you can strian braking and gearbox componants...although obviously they should be pretty snug before you drop them down....
but thanks for the thoughts...they sort of echo my own...but dont really tally with my evidence...i still think its warped disk!
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First, for your problem, I agree that it's something wrong with your rotor. But because you said it arose suddenly, for my money it's the following:
1) Because you said it arose almost overnight, I suspect that you've got a rust spot on your rotor! If so, you'll probably see a patch of discoloration (rust) on the rotor, probably the size and shape (i.e., a "stamp") of your brake pads. Moisture under the pads have been known to generate a rust spot -- and this spot causes the rotor to "grind" everytime the rotor rotates, with you feeling that spot in the pedal.
I know, because it once happened to me -- and when I looked at the rotor, there was a reddish blotch on the rotor identical to the imprint of the brake pad! Rotating the rotor by hand, in fact, I could feel the extra resistance or "rubbing" as the rust spot slid under the pads!
And it did feel exactly like a warped rotor.
And if it isn't that, then I'll consider:
2) warped rotors, possibly because you may not have broken in the replaced rotor, originally (there's a right way, per instructions accompanying the special rotorsI buy, and a wrong way, per popular myth, to speed up to 50 or 60 mph and then stop fast).
Or possibly because of incorrectly torqued lugs bolts or nuts. I never let tire shops install new mounted tires on my car; I do that myself, because I am leery of overtightened lugs! And I use a torque stick on my electric impact driver, followed by a part turn with my torque wrench to spec.
And re: "...btw you should never do the final torque for wheels up off the ground you can strian braking and gearbox componants...."
Straining brake and gearbox components? That has got to be the winner for myths, 'urban' or otherwise.
The torque generated by an engine, and resisted by the traction of the tires, application of brakes, etc., dwarfs the torque that you could possibly muster. And let's not forget the torque to the wheels if, for example, a person leaves a car in "Park" on a hill without also applying a parking brake -- a practice I certainly don't condone but nevertheless is all too commonly done (as I watch such idiots slam the shift into Park, hear the car go "clunk", and then step out of the car, and which I'm sure you have also observed on too many occasions).
And if you think that this applies for "opposite" torque, remember that wheels on each side have lugs that are torqued in opposite directions relative to forward rotation of the wheels.
It just doesn't stand up to scrutiny.
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thanks for the info....
i like the rust spot...but wouldnt it have been flatted out after 150 miles rather than getting worse?. Interestingly i DID wash the car (including hte wheels rotors yesterday...but i do that every weekend...) guess a good look in the morning with some nice bright daylight might be informative!
the rotors had no special 'breaking in' instructions, i just took it easy for the first 500 miles or so...unfortunately as it a car used daily for work on 500 mile journeys there is a limit to what i can do on that -and i have never ever had an issue with new rotors before (and beleive me i have gone through a few over a few hundred thousand miles!), also remember these are the rears (and i dont tend to drive hard) so i wouldnt expect them to get that hot - when i got in tonight i checked tham with my hand to see if anything was binding and i got my hand within 1/4" of the disks before i could even detect any heat at all...
the bolts im actualy pretty sure were right, 3 of the 4 wheels i did myself (torque wrench and 3 stage tightening) the 4th i watched the guy set the wrench, watched him do it and when i checked them today(ok not with a torque wrench but with my educated arm against the ones i had done!) they felt ok - near as i could tell, certainly no great disparity between nuts and no great disparity to the other wheels....
as to the urban myth...lets think about it a minute before we disparage it so totally...
"The torque generated by an engine, and resisted by the traction of the tires, application of brakes, etc., dwarfs the torque that you could possibly muster. "
agreed but when torquing up the rear wheels on a fwd car they are beign pushed BACKWARDS agains only the handbrake...and if you think about th torque your vehicle puts o nthat on even asteep hill its not that great compaired to swinging on torue wrench...also your vehicle is spread over both wheels rather than just one and it tend to be let down gently onto them rather than crunching a wheel nut up...
"And let's not forget the torque to the wheels if, for example, a person leaves a car in "Park" on a hill without also applying a parking brake -- a practice I certainly don't condone but nevertheless is all too commonly done (as I watch such idiots slam the shift into Park, hear the car go "clunk", and then step out of the car, and which I'm sure you have also observed on too many occasions)." yep thats the other one, and the one that would really worry me (afterall sorting the handbrake out is at least easy if you mess it up), again you torquing up against that pin..and it NEVER gets the sort of torque the engine can generate..)i guess it must also all be being transfered through the diff as well...now if you use an impact driver to do it the torque is being hammered on as a 'hit' as opposed to gentle (relatively) build up.....
"And if you think that this applies for "opposite" torque, remember that wheels on each side have lugs that are torqued in opposite directions relative to forward rotation of the wheels." - agreed
i guess its probably one of those things that you would get away with 999 times out of the 1000 but it just isnt good practice....like it or not it IS placing strain on componants, certainly cant be good to brake the nuts loose as this can require considerably more torque than doing them up....esspecially if you use a impact drive which works by imparting a shock to the whole system...
that said i have doen it myself on occasion....
thanks for the thoughts, certianly given me some more to chew on!
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posted by
someone claiming to be paco the taco
on
Wed Feb 15 05:19 CST 2006 [ RELATED]
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sorry, any torque you do with a wrench either direction is nothing compared to what the engine/tranny and brakes do. You are right in that it does put stress on the components, but really nothing compared to what it is designed to handle. Your method certainly isn't improper or wrong, but best not to spread your misunderstanding as fact.
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hang on..the parking pin i nthe transmission isnt designed to handle the torque generated by the engine....thats really the point...its a fail safe ...and then we are going to load it up with a torque wrench....or worse stil land impact from an impact gun...its not designed to handle that...
anyway when i worked for a main dealer (breifly) many years ago on the floor i was told ALWAYS to drop the car onto its wheels before torquing everything up as it can do damage not to....perhaps wrongly but that was the recomendation way back when, and it wasnt a volvo dealer i might add......and it makes some sense to me...
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re: "...i like the rust spot...but wouldnt it have been flatted out after 150 miles rather than getting worse?. Interestingly i DID wash the car (including hte wheels rotors yesterday...but i do that every weekend...) guess a good look in the morning with some nice bright daylight might be informative!..."
I agree that it seems as if the rust spot would wear away. When it first happened on my car, I thought it would dissipate after I drove it awhile. Never went away -- I must have driven it for a month before I got fed up and replaced the rotor (actually, I replaced the pair -- both sides -- as well as the pads, as I didn't want any effects of one brake working differently than the one on the opposite side).
re: "...the rotors had no special 'breaking in' instructions, i just took it easy for the first 500 miles or so...unfortunately as it a car used daily for work on 500 mile journeys there is a limit to what i can do on that...."
Well, that (just taking it easy) actually sounds better than other "break-in" procedures I've heard, such as drive up to 60 mph and slam on the brakes hard!
I buy my brake rotors from a company, Eurosport Tuning and Brakes, and they always enclose a flyer in each rotor's box describing the proper break-in procedure -- i.e., what they consider "proper", anyway. So for what it's worth, let me share it with you and other readers -- I'm not a metallurgical engineer, but there's a chance that these guys know more about brake rotors than I do, so I follow their advice. Instructions for new brake pads (per the box of IPD's PBR Deluxe pads) are almost the same instructions, too.
Basically, after installing the new rotors (and pads, ideally) it's to drive up to about 25 mph or so and then moderately (no hard stops) slow down (but do not come to a complete stop) and then repeat 4 to 6 times -- speed up, moderately slow, speed up, and repeat (no complete stops in between). You want the rotors to gradually (not rapidly) rise in temperature in this step. Then park the car and leave it slowly cool for a few hours. What I do is drive around my block a few times (there's little traffic) and I time my stopping and going so that on the last cycle I can pull into my driveway and park and leave it.
Anyway, good luck, and do check the rotor for that rust imprint.
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thats the plan for today...unfortunately it rained last night so the disks are now showing surface rust anyway...i plan to take it for a spin round the block before starting work to clean the surface stuff off....
thanks everyone for the advice, given me one or two things i hadnt thought about to look out for and thats exactly what i wanted!
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