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MG MGB Technical - Bearing adjust front wheel.
|I have a light play in right front wire wheel, and according to the book i should pull out the split pin thru a hole in the hub and tight the nut...but how much??|
|Alfredo, yes you have to pull out the pin bu the bearings are adjusted by shim selection. There is a lot about this in the archives. |
|There should be play , between 2 and 4 thousandths of an inch (0.05 to 0.1 mm)is specified . So if wheel was pre-loaded it would be wrong .|
|Thanks Iain, i got it..|
|That's great Alfredo. Sounds a bit complicated but it works well. Two to four thou is bang on for end float as well.|
|Lot of conflicting advice in that thread, you have to make sure you pick out the correct bits! As far as the hub nut goes it should be tightened to a minimum of 40 lb ft, then tightened further to the next split-pin hole, which should be before 70 lb ft. If you have the shims right you will still have the 2 to 4 thou free play in the bearings. But play at the wheel can be caused by worn king-pin bushes, and possibly track-rod ends, so you need to be sure where the play is before you start adjusting things.|
|I got the nut off, there is no shims.|
So now i put new 5 thou shim, and tight the nut, but the split pin is not aligned. Must i shim it now to get the pin in and slight realise the nut?
|You have to use a torque wrench and do it as Paul says, Tighten to 40 lb ft , then set the wrench to 70 and start to tighten again . A slot in the nut will always line up with one of the holes before the wrench clicks again. One hole is up/down and the other left/right as you look at the stub axle.|
The idea is to fit enough shims between the outer bearing and spacer so that when the nut is tightened quite hard (40-70lbs/ft) there is still a little movement in the bearings (2-4 thou).
You'll need a variety of shims from Moss or MGOC etc and it's easiest done dry if it's a wire wheel hub, with the bearing down inside the stub, without the oil seal on, then grease up for final assembly when you have found the shims needed.
Mine needed 45 thou one side, 48 the other, which is typical, so get a load including the 30 thou one.
If you don't have a torque wrench it's not hard to estimate pressing down on a 1 foot bar with 40 lbs force, then press some more to align for the next split pin hole. Maybe practice on the bathroom scales. I used to do Saab rear hub nuts to 210 lb/ft by standing on a marked point along a long bar with a support under the socket :-)
|I did not read Paul comments skip it for some reason, and unfortunatly i donot have a torque wrench, but i will borrow one to finish it, |
|Also to amplify what Rich has said, the shims aren't under the nut but between the inner race of the outer bearing and the spacer.|
|Interesting to note Rich's comments re his shim pack thickness. I was always taught that on the B the shimpack starting point should be 1mm plus ten thou. This would have given Rich a clearance on one and a half thou on one side which is near enough spec and four and a half on the other side which would need only one adjustment of the pack.|
|Manage to fix the bearing play, took to MOT, ok in there, but it failed on back wheel brakes, reckons 30% diference off front right to left...any ideas..|
There is quite noticiable clonk at front, when brake,
i thought it was the king pin play, but while at the Mot, when testing the system, we find no play, it passed.
Could it be the calipers, shoes are ok...discs enough material..
Have look at the cross member mountings. Are the bolts tight and are the rubber pads in good condition.
|Failed on back brakes *and* front brakes, I assume, there should be a lot more difference between front and back than 30%, whereas there should be much *less* difference than that between sides (either front or rear).|
Back brakes are tested twice - for foot pedal operation and handbrake - which failed, or was it both? Weak footbrake could be contaminated linings/drums, siezed slave pistons, pinched rear brake pipe. Failure can also be too much pedal travel because of worn linings and drums or simply poor adjustment. Weak handbrake could be seized cable, worn linkages, or again to much travel due to a stretched cable or poor adjustment.
If the fronts are different to each other it could be one bad disc, contaminated pads one side, sticking piston one side, internally delaminating flex hose one side partially blocking the pressure. Normally I'd expect any side to side difference at the front to cause it to pull to the good side under braking.
Front clonks could well be king-pin play but they test for that, and play in several other parts in that area. Could be A-arm inner bushes, cured a clonk one side on my V8 with new bushes, then the roadster started doing it. Can't see it being a caliper, unless it is actually loose, which is pretty dangerous, like any other loose components in the steering and suspension.
|Possibly movement of the pads in the calipers causing front clonking.|
Was the 30% failure due to handbrake difference, footbrake or both? Have you had the drums off? Leaking cylinder or axle oil seal is common.
If it was just the handbrake lube the cable and re-adjust both back brakes. If it's a mess in there the best course is to take everything out (mark which shoes go where if you are going to use them again) clean, degrease, lube, fix leaks, and reassemble. Rich.
|Oh, possible spline clonking if you have wire wheels?|
|Back brakes failed due to left wheel brakes 30% less than the right,and as you suggested i will have a look at linnigs, shoes and handbrake...|
Front brakes passed, but iam not to happy with that clonk, specially after a comment i had from a Ebayer....remember?..i will explor all possibilities as per your comments..
I have wire wheels, but they seem to have a nice fit.
|One quick check would be to look at the inside of the wheel on the weak side. This type of difference in effectiveness could well be a failure of the hub oil seal on the weak side. When this happens the oil gets on the shoes and inside of the drum. It then sprays onto the back side of the wheel rim. When it gets to this stage it is easy to identify.|
This happened to me recently. As you have to fit new brake shoes on both sides at the same time I changed both oil seals. If you do this remember to top up the axle oil afterwards.
|Took off hubs, the shoes are ok, but cylinder on left wheel is seized one side, badly rust, the right one also in bad condition, i wont atempt to replace the seals, fit new ones.|
Any trick to replace them, such as how to leave the adjuster etc...how do i prevent to loose the brake oil from pipes when removing the cylinders?
|Use a brake hose clamp on the rear flexy at the axle or put a piece of clean polythene under the master cyl cap and screw it down to stop fluid loss. I prefer the latter for the rears as it stops fluid loss and I don't really like clamping pipes. They bleed out easily after you've changed the cylinders.|
Most aftermarket cyls are pattern type (Italy?). I fitted 2 a few months ago which work fine but I needed to remake one metal pipe flare as it wouldn't reseal to the new cyl. Also I kept finding a drop of fluid on the bottom of one brakeplate. After much investigating (leaking rubbers? leaking pipe flare? leaking bleed screw?) it turned out to be the bleed screw which needed to be tightened very hard but did finally stop weeping.
A week later and the other side did exactly the same. Again, tightening the bleeder(!) did the trick. Been fine since but keep an eye on them after the work's done.
Note MGB and MGBGT cyls are different bore. They are physically the same but have the locating roll pin in slightly different positions so they won't go on the wrong backplate. I mention this as axles get swapped and if you have a GT axle and brakeplates on a roadster or vice-versa you'll find the correct cyls don't fit. Remedy is to elongate the small hole with a file and it will still do the job of locating.
Adjuster-wise, take them apart, clean and grease them if stiff, then refit everything with adjusters fully slackened, and re-adjust with drums back on (lock up then 1 or 2 flats back till wheel free).
|Just wating for the spares to do the job, it seems easy.|
|mgb roadster and GT rear slave cylinders are *not* the same! The GT has a slightly larger bore to apply more braking effort for the same pedal pressure, it can do this as the greater weight of the GT resists locking more than on the roadster. This is why the locating pins are in different places, not just perversity on the part of Abingdon. Call me pernickety, but I welded up and redrilled the hole (on the backplates that came with the axle off a GT that was going on my roadster) to prevent fitting the wrong item in future (by me or anyone else).|
The C-clips securing the slave cylinders to the back-plate are said to be a right pain to refit. I replaced mine with the back-plates off as part of other work, with screwdriver and hammer, it will be a pain on-car.
Put a thin smear of grease on every metal to metal contact point between shoes, backplate, adjuster, slave pistons and handbrake levers but not enough to get on the linings. Clean and lubricate the pivot on the handbrake levers, the clevis pin between cable and levers, compensating lever on the diff housing, and the cable itself (if it has a grease nipple which decent replacements now have back again, after being dropped by Abingdon)
Don't try and maintain the adjuster setting. With the new cylinders fitted and bled adjust both from scratch, then adjust the handbrake (adjuster by the lever) to get an appropriate number of clicks. I adjust by pulling and releasing the handbrake a few times, then pumping the foot pedal a few times (to simulate normal use) then tap round the drum with a mallet to seat the shoes (again to simulate normal road use). The drums should spin with minimal rubbing, and no dragging. But even then my V8 needs one click looser adjustment than the roadster or they bind, so after adjusting drive for a mile or so and feel the drums to make sure they are not hot. Just did all this yesterday as part of the annual service on my roadster and I can lock the rears with the handbrake.
|I decided while watting on new cylinders, to strip the old ones and the left one couldnt remove the pistons by hand, i use a vice an a hammer, totaly rust, the right one is rust but not acceptable, the emery paper would not clean the pit marks, i had to cut the copper pipes because the nuts would no turn.|
I have a set of brake pipes and flexible hose that came with a B LE i bought 3 years ago,(the guy wanted to get rid of it so bad that he gave me a whole bunch of spares), which iam going to use.
Already clean the adjusters and greese and refit.
About the cylinders a specified to the dealer that is a GT 67, hope to get the right ones.
cheers, nice weekend
|Cylinders received and replaced, works ok..,|
now the front clonk, must look into it now.
This thread was discussed between 14/04/2005 and 27/04/2005
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