ASK THE EXPERT
Yours Mini questions answered by Keith Calver
Our tech expert Keith Calver answers all your Mini technical queries.
Q I’m struggling to get decent ball race wheel bearing kits. Is it possible to swap the roller bearings in a drum hub for Timken taper rollers? If so, what would the torque figure be? Toby
A Yes, you can simply fit the Timken-type taper roller bearings to both ends of your car, providing it isn’t a really early MkI. Up until around 1962 I think it was, the front wheel bearings were different, with a smaller bore. Consequently later ball race and Timken bearings would be somewhat baggy on the drive flange shaft.
I used to do this mod years ago, using Timken taper rollers ‘retired’ from my Mini Miglia in a couple of my road Minis owned at the time. Based on no more than my own application of general engineering practise, I used the drum brake torque settings. This is based on the fact that the majority of torque settings are devised for the fasteners and what they are fitted to rather than the other components in the assembly. The torque settings given for the CV nuts on a Mini are more to do with the stretch and load of the CV nut, taper washer and thread on the end of the CV than the bearing/hub assembly. The bearings and associated spacers are made from high strength, hardened steel so do not collapse further under greater torque pressure. I never had any problems running them like that.
As an aside, but pertinent, I have heard way too many folk suggest that taper roller bearings are ‘adjustable’ by simply tightening the CV nut up more. They may be for certain applications that use shims to achieve a specific amount of ‘play’ where a ‘finger tight’ approach is used in assembly, typically on low-load applications. But in applications where high loads and specifically high torque settings are used to clamp the assembly together, they are extremely unlikely to be ‘adjustable’ by increasing the clamping load over that recommended. Again, the hardened high-grade steel components of the bearing assembly will not crush down any further. All you are doing is over-stressing the threaded end of the CV joint. That can be disastrous as it may cause the end of the CV to shear off, and the mayhem that implies.
Q I plan on having a gearbox rebuilt for my Mini Mayfair, which will mainly be used for weekend fun and trips to shows. It’s going to be 1330cc with a 276 cam and a Stage 3 head. I know a four-pin diff would be useful and I’m planning to fit a centre oil-pick
“The question then revolves around whether you are desperate for that distinctive whine or not...”
up pipe, but should I fit straightcut drop gears? A friend has a set for sale and I’m led to believe they will help to cut transmission power loss. Is the extra cost worth it? Dieter The straight-cut drop gears are the components that give many a racing Mini, and for those that want it on the street, that distinctive whine in use – a noise that can become extremely irritating on long runs. The ‘power’ gained is not in terms of tens of BHP; not even half that in reality. As a whole the difference between a complete straight-cut transmission assembly, from drop gears to final drive, only gains around 5-6bhp at best against a decently-built helical set-up. And ultimately the helical gears are far better quality and therefore longer lasting and more reliable. So the question then revolves around whether you are desperate for that distinctive whine or not.
Q I’ve got a ‘94 Mini Mayfair and the tyres are wearing out on the inner edge. I’ve looked at the tie-rods and they appear to be bent. Could this be causing the problem? What else might cause wear on the inner edges? Is the tracking out? Ronnie A Wear on the inner edges of tyres suggests it could be two causes – either excessive negative camber or excessive toe-out tracking. The bent tierods will be giving the geometry increased caster angle, but this is not generally the cause of the tyre wear you are experiencing. The bent tie-rods are not likely to be helping the situation, or the car’s handling in terms of straight line running. They should be replaced as a matter of course. Negative camber is where the top of the tyre, viewed head on, leans in towards the centreline of the car, causing the tyre to run on its inner edge more. Toe out is where the leading edges of the tyres are pointing outwards, away from the centreline of the car. Again, this causes the tyre contact patch to be more on the inside edge. In both instances premature tyre wear on the inner edge is the result.
The question is, which is it? With no further details of the car given, I can only presume the car is running all standard suspension components and geometry. In which case the most likely cause is incorrect tracking, so get this checked and re-set. Excessive negative camber on a standard car is highly unlikely unless the suspension has literally collapsed so it is sitting on its bump stops. The give-away here would be the tyre scrubbing on the front wheel arches over every bump and dip in the road. There should be at least 1.75 inches between the top of the arch and the top of the tyre.
Taper roller wheel bearings can be used in place of the ball bearing type.
Straight-cut drops can be noisy.
Too much toe-out can cause excessive tyre wear.