Help Needed! Brake Callper Bolt won''t torque

Hi all Had an issue with my steering vibrating under braking and garage told me the front discs were warped, so I went about changing them today. I was a bit sceptical as the wobbly steering was only at higher speed braking (and standing on the anchors showed no issues) but hey ho they said it was the discs so off I went. Anyway, nearside no problem, done and dusted in 25 mins. Drivers side was an issue though. Got through to refitting the caliper and the bottom bolt won't torque. It tightens all the way to the end then goes a little tight, then loose, then tight again, etc. I swapped the bolts and same issue with the bottom. The top torques fine with either bolt. I have the Brembo calipers so these are the 10mm Hex head bolts. I did notice when removing the lower bolt some small pieces of silver metal in the threads so I'm guessing there's something wrong with the bolt hole. I know I didn't cross thread it, and when I originally took the bolt out i didn't really notice if it needed the same torque as the top one so not sure if this was present before hand. So, what to do? I assume I need to get the hole retapped or get a new hub. I also assume the car is not safe to drive any long distance. I've done everything up, top bolt torqued properly and come inside for a beer. I'm falling out of love with this car, just can't seem to get it into a decent state for long enough to enjoy it. :nooo:

I suggest that the thread is stripped. It will need helicoiling or replacing. I would take the hub off and ask a local machine shop to do it if you don't feel confident. I think it is M12x1.5mm but they will check. Keep calm, not really a biggie. MC

Strange though, no issue getting it out originally so I guess it's just wear and tear. I can't understand the physics of why it happily tightens to the end but can't torque up. Thanks for the confirmation though, I don't plan on getting the hub off as being 4wd there a bit too much effort and lack of experience on my part for that. I'll contact the garage and see if I can get it done asafp. What's the sitrep with driving the car? Assume as little as possible, or will the top bolt do a job?

Probably find whoever put it in last overtorqued it & pulled the threads, or its stripped partially on removal. What will be happening is there is enough meat left to run down, but as soon as any real torque is applied then the threads will be just climbing over each other. Whip it off & get it rethreaded with a helicoil, it will be stronger than the original thread & shouldn't cost much to do at any decent engineering workshop.

Thanks. Could it be helicoiled in situ? The caliper can be moved out of the way and with the wheels turned fully you are looking straight at the hole to be retapped. And, any advice on drivability please?

Ok first of all you have done nothing wrong , the bottom bolt is open to the atmosphere front and rear and so the base of the bolt corrodes. When you remove it you are basically dragging corrosion which is bigger than the hole up and out .. it strips the threads in the hub . The tell tail sign is a difficult to " crack " the seal and then the first turn its still hard to unwind the bolt .. in fact its tight the whole way out . Difficult to explain , i can feel when there might be a problem and so have a chance to get customer authority before proceding .. warn them basically but ive still stripped threads after all these years without realiseing it . When you do refit these bolts then a decent amount of ally grease is a must ! The repair .. A helicoil is a goood idea but not really strong enough imho .. we use timeserts , these are not that cheap when compaired to a helicoil .. ie £20 verses £180 for a kit . The procedure is remove caliper , wheel on a full lock , drill out with supplyed drill , counter sink , tap a new thread then fit the timesert .. hub stays on the car . As reguards to driveing an unfit car then i have to say no , but ive no choice there .. i always say no and get it recovered Top bolt only holding the caliper , wheel rotation forwards will press the caliper onto the hub when brakeing .. in reverse it will do the opposite . Just to point out the obvious which isnt really needed but its what i do .. make sure you have sanded down the hub face before fitting a new disc .. any high spots and you will have wheel judder ... Btw a loose wheel also causes brake judder .. found that out the hard way on a road test prior to looking at a car that was in for brake judder !

Thanks Demort, I'm not convinced by the warped disc scenario, and if I find I still have the same symptoms I won't be happy. I wouldn't have touched the discs and caused these issues if they hadn't advised me to change them. I'll be on the phone first thing trying to get myself booked in to my Indy. I'll have to drive like a vicar I guess to get over there, it's only 10 miles. I have definitely torqued the wheels correctly, if anything I overdo it slightly at 100ft/lb so no issue there.

Dont worry about the wheels .. that was just something that happened to me one time which i wasnt expecting ... but it did prove what else can cause brake judder ! I cant remember your first post about this .. sorry .. brake judder along with steering shake is normally front discs though . Driveing the car is your choice .. as i said .. my hands are tied on what to advise as i do this for a living .

No problem, it was just steering wheel shake when braking at anything above 25mph, below that and it stopped. No pedal judder or any other issues, just the steering wheel going nuts. The faster I was travelling, under medium to light braking the faster and more violently the wheel shakes. No issues though when braking hard, I have stood on the anchors a few times to test it and it stops without any drama. I changed all of the control arms and the track rod ends last week, it didn't make a difference so when I had it in for alignment I asked them to check it. They said they did a run-out test on the brakes and they were 'suspected" warped. Both from wheels still have a lot of E-W movement when rocked with the car in the air. The only thing left that hasn't been changed in the inner track rods.

Paragon Helicoiled one of mine a few years ago, its been on and off numerous times with no problem :thumb: I did take the hub off though and took it to them.

Thanks buddy, good to know it's not as bad as I'd feared (Demort also put my mind at rest yesterday). I've no way of getting the hub nut off so I'll give the garage a a call first thing tomorrow and get it booked in and let them do it all. I did pop out this morning, I was a bit pissed off and I wanted to go to the gym so I went out and was very careful to avoid as many braking situations as possible, but initial feedback is the wobbling has gone under braking. I'll not use the car again now until I'm driving it to the garage, again I'll just need to be extra careful on the way.

Just to update, had this sorted today for a reasonably cheap sum of £125. I had to drive like a vicar on the way to the garage, which was quite tough, but managed it ok and all done. Had the thread drilled out and the hub sorted with a Time sert and new bolt. Thanks for the advice and support.