g/s bevel to wheel play

[steveo]

i have noticed a small amount of play when i grab the rear wheel top and bottom, spoke to jim cray and and he can replace the bearings (about £300) so i have removed the wheel and bevel, however with the wheel flat on the ground, a knee on each side i can only detect a tiny amount of movement when i rock the bevel, same with the wheel removed and i grab the drive inside the bevel.
i do understand that the diameter of the wheel will accentuate this movement.but im at pains to spend 300 squids for such a small amount of movement.
one other thing i did notice is that the coned spacers/locators under the wheel nuts have alot of play on the wheel studs, should they not be a snug fit on the studs, the hub itself i bought new a few years ago as it was cracked from po s over doing the wheel nuts

 

[Richard A]

I haven't got the figures to hand, but the 3 bolt G/S (and ST) monolever setup does allow a detectable amount of play when rocking at the rim. I believe (although I'm not 100% certain having not rebuilt one) that the bearing design on the 4 bolt GS (et al) setup is such that there is no detectable rock if it's in good condition.

I know the above because after I bought my two prev owner 4 year old, 20K mile ST back in 1989, a (new) BMW dealer in Bristol failed it on rear wheel rock (Bath Road, I think it was), even though the figures were within the tolerance given in Haynes. I even wrote a letter to BMW UK who confirmed that those tolerances were correct. I didn't go back. From then on, I took my bikes to Difazio's for MoTs. After another 40K, the rock is still the same.

The conical spacers do have a certain amount of play when initially placed on the studs prior to refitting the wheel, but their design is such that they should tighten snugly into the corresponding conical rebates in the wheel boss casting. I don't think different conical profiles were used (surely not), but I suppose that would be something to check.

Do you mean that you bought your current hub to replace the previous one that was cracked from overtightening?

 

[Beemerboff]

Same storey on my G/S - slight play for 60,000 km, not getting any worse.

The bearing is a loose tolerance C3 bearing which is supposed to be shimmed up, so the play may only be incorrect shimming, not wear on the bearing.

But as you have a 3 bolt drive check it regularly - they are scarce second hand and parts are scarce and expensive, so you wouldn't want to let it go too far and damage it.

 

[steveo]

Do you mean that you bought your current hub to replace the previous one that was cracked from overtightening?[/QUOTE]

thanks guys, yes , thats why i bought a new wheel hub, looked like it was ready to explode with cracks coming out from each hole now i dont know weather to see if some one can shim it up for me ( sounds alot cheaper than £300 ! ) and maybe buy some new conical spacers, the bike is a very early g/s, 1980, one of the first and has done god knows how many miles. i know the spacers dont revolve but might have incured some wear or miss shaped over the years.
any thoughts, or clues to someone who could look at the shiming would be greatly appreciated as its a bit of a worry, tho i have been told that these bevels are bullet proof and would give good warning before letting go. im in the brighton area.
thanks again . steve

 

[Canuck]

If in doubt contact steptoe! send him a pm or ring the gsshop!

 

[stuart jenkins]

Hi Steve,
Thought my bearings had play, turned out it just needed to be re-shimmed, iirc shims were about £14 each + the cost of a gasket (that was some years ago).
I live near Brighton, if you want to check out me rear wheel play, to see if yours is more or less, feel free.
If Jim Cray saw your bike in the flesh, and said it was the bearing, i'd trust him with the diagnosis, you won't get anyone with as much old airhead knowledge in the south-east as him, top bloke, well respected .
Stuart

 

[steveo]

Hi Steve,
Thought my bearings had play, turned out it just needed to be re-shimmed, iirc shims were about £14 each + the cost of a gasket (that was some years ago).
I live near Brighton, if you want to check out me rear wheel play, to see if yours is more or less, feel free.
If Jim Cray saw your bike in the flesh, and said it was the bearing, i'd trust him with the diagnosis, you won't get anyone with as much old airhead knowledge in the south-east as him, top bloke, well respected .
Stuart

hi stuart, i would like to take you up on your offer , jim did nt see the bike but was very helpful and will use his services for whatever is needed, not sure you can pm me as due to austerity measures my membership has lapsed , my e mail is [email protected].
many thanks , steve

 

[dr nosh]

one other thing i did notice is that the coned spacers/locators under the wheel nuts have alot of play on the wheel studs, should they not be a snug fit on the studs, the hub itself i bought new a few years ago as it was cracked from po s over doing the wheel nuts

I think that if the wheel nut cones are loose this is a seperate problem from the overall diagnosis.

Suggest that you remove the wheel and :

Clean the 'countersinks' in the hub where the cones sit - no burrs or dirt or similar.

Clean the cones, especially the ;'mating' face.

Clean the wheel nuts, especially the internal threads - degreaser, airline, small tooth brush.

Clean the 3 studs, especially the threads.

Check that the cones do slide up over the studs - No burrs etc.

Copperslip the 3 studs and ensure each nut will go to the end of the thread by hand, no burrs or damaged threads.

Reassemble wheel, cones, nuts, nip up, and torque up. (I'm at work right now, don't have a figure, but tight).

There should only be a very small gap between the hub and the adjacent face of the FD.
(Will measure this later and post up).

Once you know the wheel is fitted, secured correctly then concentrate on the FD play.

These are meant to have play (as previously mentioned), but again without checking mine I don't have a number. Again will post up later.

Good Luck.

 

[Richard A]

The data is somewhat buried (in the major service section) of my newer Haynes (I'm sure it was more obvious in the old one which I seem to have lost), but basically they say the following:

Check must be made when cold, with the machine on the centre stand, rear wheel clear from the ground and with a dial gauge (clamped to a convenient frame tube) on the outer edge of the wheel rim flange at the top of the wheel.

Grasp the wheel firmly at the top and bot and attempt to rock it from side to side about its centre.

On R80 and R80RT 1985 on, R65 1968 on, R100RS and R100RT 1987 on + all paralevers there should be no discernable play. On R80G/S and R80ST models a maximum of 0.5mm (0.02 in) play is permissible.

The latter is confirmed in the original BMW R80 G/S Reparaturanleitung which gives the Hinterrad-Kippspiel (literal trans. 'rear wheel turn over sideways play') as 0.5mm, again measured on the rim via a dial gauge.

 

[steveo]

blimey richard and the dr, many thanks for your advice ! i ll have a go over the weekend, i have a mate that prob has a dial gauge.
i spoke to mr cray again today, what a top man. a few things he pointed out: if the oil was still a golden color when drained then the bearing is prob not destroying itself.(my oil was good)
if i had to replace the hub due to PO s overdoing the wheel nuts then a possible stretch in the wheel studs.
i can remove the brake shoes, then there are two small threded holes into witch i can wind two bolts, this will pop off the plate and reveal a shim ontop of the bearing, this can be measured and replaced with the proper thickness .
lots to go on there too!
i think i would like to accurately measure my wheel studs first after a good clean up etc as you suggest. before i go for the shim option.
does anyone have an accurate stud length measurement that i can compare to? many thanks again for all advice.....steve

 

[dr nosh]

Did not have time to remove wheel tonight, but,

The wheel studs protrude 3.15mm from the outer face of the nut. Torqued to 63 lbf ft.

This is the gap between the machined edge of the hub and the inner face of the FD housing.

 

[steveo]

thank you Dr !! im going to try and make time today to get over to a mates fabrication shop to make some accurate measurements.
on another note , a friend suggested that if the bearing was eating itself, it would nt show in the oil or magnetic drain bolt as its stainless?? only the bevel gears themselves would produce magnetic swarf .......

 

[cookie]

bearings are not generally stainless IME.

 

[dr nosh]

Not familiar with this bearing itself, but very unlikely to be stainless. Possibly high chromium content giving the appearance of stainless more likely.

 

[dr nosh]

thank you Dr !! im going to try and make time today to get over to a mates fabrication shop to make some accurate measurements. on another note , a friend suggested that if the bearing was eating itself, it would nt show in the oil or magnetic drain bolt as its stainless?? only the bevel gears themselves would produce magnetic swarf .......

You can measure this gap with a good set of feeler gauges....good = no bent/buckled/twisted blades.

 

[Kenny]

Hardened steel bearing.

I've owned a few g/s's and some have a little play and some don't...all never got any different

 

[steveo]

right, well i cleaned up all the studs, cones etc, measured the studs
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and put it all back together, with the nuts done up to the right tightness there is no stud to measure, they are flush with the top of the nuts,the rock is still there, not able to measure as no dial gauge but along with a mate we recon there is about a mm of movement at the wheel rim which my mate recons would be reduced by about 2/3rds as you got to the hub, so aprox a 3rd of a mm.
strange tho....the rock is at its worst when you hold the wheel at 12 and 6 o clock(spin the wheel to any position and its the same).
hold the wheel at 9 and 3 o clock the is no rock !!
hold the wheel between these two and there is a very small amount of rock.
how does that bloody work???

 

[Richard A]

how does that bloody work???

Bearing physics/mechanics is a bit of a dark art and I'm only an amateur, but I think there will be an exponential tendency to wear more at the top of the static outer bearing surface, especially once things start to get a bit out of tolerance, because that's where the weight is being applied by the frame of the bike on the bearing race. The race itself and the inner bearing surface are constantly turning so the wear is evened out. Probably with a new, tight bearing, the transfer of weight to the axle is pretty evenly spread via the bearings, Hypoy oil film etc., but once a bit of wear develops the pressure will become progressively more focussed on the top of the outer fixed bearing race.

Actually, the main focus of wear on the outer static bearing, according to my theory, which I've just invented, is probably slightly forward of the top, to account for the thrust force when the bike is in motion.

(Signed Richard A, professor of engineering at the University of my Brain, particularly when I've had a beer or two and everything in the world seems to make sense.)

 

[steveo]