Check Your Wheel Bearings!
Discussion
The lack of grease may not be a surprise if it has got very hot. The post suggests that the stub axle went blue so some very high temperatures there! I think a little more forensic analysis as to the cause would be wise. It should be a regular service item and definitely in the first service IMHO.
I would dismantle, clean, and repack the bearings. Personally, I would also run a slight pre-load (8 NM on the nut) although I accept that many people don't like doing that. The main reason for cleaning at the first service is to remove the running-in debris. Once you've got a good bearing with clean grease it'll go on for many thousands of miles. Track cars that generate high brake temperatures may need more regular checks/cleaning/repacking.
There have been a number of such 'failures' reported, and Chris at The 7 Workshop has repaired a number of such failures, as well as preventing many by re-packing the bearings.
It most definitely IS a lack of grease.
The overheating of the stub axle was caused by the failed bearing, not the other way round.
You can see just how bad the bearing failure was in the images.
It most definitely IS a lack of grease.
The overheating of the stub axle was caused by the failed bearing, not the other way round.
You can see just how bad the bearing failure was in the images.
Eugene7, I would be very surprised is if it's a lack of grease despite what you may have heard from other sources. For it to be a lack of grease there would have to be almost no grease what so ever in them. Remember you only need a minute film thickness to prevent asperity tip contact between the rollers and race surfaces. The grease's roll is predominantly as a lubricant to separate the roller and races rather than for any cooling, if it had been oil lubricated it would have been different. Also modern cars with sealed bearings manage to complete many thousands of miles with only the tiny amount of grease contained within the sealed for life unit, they do however have the correct clearance set in them during manufacture.
In a back to back tapper roller bearing configuration as per that used in Caterham front hub bearings the outer nut sets the clearance between the rollers and races. Over tightening of this nut is a much more probable way of causing the failure you have suffered. This is why you are told to "nip" up the nut and then turn it backwards to get the split pin the through the next previous hole allowing for a degree of play in the bearing since a slightly loose fit is prefferable to an over tight fit. It would be very easy for someone untrained or uncaring to have carried on nipping it up to get the split pin aligned with a slot on the castle nut thus resulting in a situation where the bearing has insufficient clearance. This would then lead to the bearing running hot and potentially melt out any grease expediting its failure.
Having said this, without seeing the parts and a forensic disassembly it is difficult to offer an opinion with a high degree of certainty. This is from someone who inspects industrial gearbox and bearing failures for a living.
edited - Since I cant spell
In a back to back tapper roller bearing configuration as per that used in Caterham front hub bearings the outer nut sets the clearance between the rollers and races. Over tightening of this nut is a much more probable way of causing the failure you have suffered. This is why you are told to "nip" up the nut and then turn it backwards to get the split pin the through the next previous hole allowing for a degree of play in the bearing since a slightly loose fit is prefferable to an over tight fit. It would be very easy for someone untrained or uncaring to have carried on nipping it up to get the split pin aligned with a slot on the castle nut thus resulting in a situation where the bearing has insufficient clearance. This would then lead to the bearing running hot and potentially melt out any grease expediting its failure.
Having said this, without seeing the parts and a forensic disassembly it is difficult to offer an opinion with a high degree of certainty. This is from someone who inspects industrial gearbox and bearing failures for a living.
edited - Since I cant spell
Edited by 
boy on Monday 22 July 12:31
boy on Monday 22 July 12:31I'd agree with boy. Every engineering reference you look at suggests excessive pre-load or overload for this kind of failure. Lack of lubrication seldom leads to the catastrophic failure as seen in the photos - there's simply too much noise and warning to let it get that far. I'd guess this was a relatively sudden failure (on the right hand side?). Possibly the inner races were rotating on the stub axle - eventually overheating and partially seizing to the spacer/nut and increasing pre-load further. I'd like to know what state the split pin was in!
Only an opinion mind - happy to be proved wrong!!
boy. Every engineering reference you look at suggests excessive pre-load or overload for this kind of failure. Lack of lubrication seldom leads to the catastrophic failure as seen in the photos - there's simply too much noise and warning to let it get that far. I'd guess this was a relatively sudden failure (on the right hand side?). Possibly the inner races were rotating on the stub axle - eventually overheating and partially seizing to the spacer/nut and increasing pre-load further. I'd like to know what state the split pin was in! Only an opinion mind - happy to be proved wrong!!
Chris at The 7 Workshop has forgotten more then most of us will ever know about such issues...
I will go with his findings on various car's he has serviced - a lack of grease was to blame.
He's says he has seen this numerous times on recent 7s (from the past few years).
And as the OP on the linked to story states, there have been folded over seals as well...
All very poor
I will go with his findings on various car's he has serviced - a lack of grease was to blame.
He's says he has seen this numerous times on recent 7s (from the past few years).
And as the OP on the linked to story states, there have been folded over seals as well...
All very poor
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