66 replies to this topic

[phil hill]

I don't think anyone was misunderstanding your impressive work MontpellierVanMan's (Rory ?? If so Hi !!).

My only thought about those guys (Swifty and KC) comments, were they thinking about lowered cars, and therefore trying to get the steering arms and joint closer to "standard" settings once the car was lowered ?? Having said that, if they were then does that work in combination with lowering or some other special trick I wonder ??

Chris, my own experience with a 13" vented braked Mini was that the car was very "darty" around the straight ahead position until someone who knew what they were doing set the suspension up - but there was no suggestion that any bumpsteer correction was done, just setting up the usual adjustables.

I have also seen spacers of about 10mm with two sets of holes, one to attach to the hub upright, then another set equidistant to attach the steering arms onto, effectively moving the arms up and rearwards with respect to the hub.

I have no idea what difference this makes except it would make the lever of the steering-arm longer - if is that required or even necessary ??

Phil.

[MontpellierVanMan]

Hi Phil,

 

Interesting to hear about those extension arms - unless they were just designed to lighten the steering, with no thought regarding bump-steer consequences !

 

I had initially fitted a Quick-Rack (that right ? fewer turns lock-to-lock ?) but even with just 12" 4.5 rims the steering was heavy ; I went back to the standard ratio last month and it's still more than I'd want my daughter to park with.

 

Remember that my bump-steer measurements were conducted over full-bump to full-droop - was it 120mm in all ? - with just TINY variations in tracking, I can't see my info on the earlier pages as I type right now, so if the car had been lowered, say 25mm, the bump-steer shouldn't change much over small deviations.

 

I'd love to get an experienced Mini driver to compare their car with my modified Van - the precision and stability of the steering appears to be out-of-this-world to me, but I'm "almost from Barcelona" so ............

[Spider]

Phil - In theory - if the Bump Steer has been 'dialled out' then raising or lowering the car should have zero effect on the Steering, that's why after all we are correcting it

 

Going to a lower Profile Tyre, even from 10's to 12's does make these cars so much more sensitive to any suspension 'errors'. Certainly going to a 13 will do so even more so. While we run 13's on the Mokes, they aren't a low profile tyre by any stretch (80 to 100 series ), so we can usually get away with a lot.

 

Making the Steering Arm longer, if straight back, reduces the Ackerman Angle and so will also reduce Bump Steer.

 

I did find that ERA Parts listing and yes, they did fit that 10 mm spacer, thanks for the heads up on that.

[Ethel]

Rewind 1 year:

 

Metro hubs don't have nipples, the BJ's are sealed and have male threads to go in female threaded hubs. The taper on the pins also changed, so only early ones will fit in Mini arms.

 

The KPI is also different, but I'm not sure we ever got a definitive figure - it would be good to have all this data collected in one place.

 

I reckon Spider's right on the turning circle, weren't direct comparisons made with the Imp? There's certainly a 70's commercial to be found online making direct comparisons with the Fiesta and R5. They may have also had the capabilities of the drive shafts in mind and decided they could cope better than planned in '59.

 

Without resorting to pencil & paper, I'm trying to visualise if raising/lowering the subby (to alter the effective rack height) would be equivalent to spacering the steering arm? Could that make the rubber mounted subby your third mark of steering geometry?

[Spider]

Rewind 1 year:

 

Metro hubs don't have nipples, the BJ's are sealed and have male threads to go in female threaded hubs. The taper on the pins also changed, so only early ones will fit in Mini arms.

 

yeah, yeah yeah,,, we established that at Post #2 - best keep up mate

 

BUT

 

Now you mention it and on a very serious note.

 

If (for what ever reason) one is going to run with Metro Hubs *** CAUTION ***

 

Ball Joints for Metro Hubs are NOT all made the same.

 

On a Mini, the Ball Joint needs a minimum of 52⁰ swivel angle of the pin. Original Mini Ball Joints have 55⁰ of movement before lock.

 

The Austin Rover Boxed MKI Metro Ball Joints have 52⁰ of swivel movement, no issues there.

 

However,,,,,,

 

The ones that come out of Quinton Hazel boxes only have around 44⁰ of swivel angle. I haven't actually measured them exact as it was clear from the outset that they fall well short and will break if used on Metro Hubs fitted to a Mini.

[Ethel]

The defence submits we only established them's Mini hubs in post 2. The OP beat me to stating the differences in post 44   .

 

Glad I posted though, didn't know that about QH balls. Aren't there some exotic Mini "race" hubs using Metty BJ's, so a point worth considering stil.

[Spider]

The defence submits we only established them's Mini hubs in post 2. The OP beat me to stating the differences in post 44   .

 

Glad I posted though, didn't know that about QH balls. Aren't there some exotic Mini "race" hubs using Metty BJ's, so a point worth considering stil.

 

I can't recall if it was mentioned somewhere else that also with Metro Hubs the King Pin Angle is 10⁰, so another reason not to use these on a Mini. They also give a further increased scrub radius,,,,,

 

And yes, I think KAD and others use Metro type Ball Joints in their Mini Hubs.

[tiger99]

Isn't the Metro scrub radius negative, as it must be with ABS braking or a diagonally split system to avoid severe instability? Makes me wonder how the Minis made in the short time that a diagonal split system was used would have behaved if one circuit failed. I don't have to wonder very hard about why they dropped it.

I have a MK 2 Metro manual lying around and it shows one externally threaded ball joint at the top, the other being built into the bottom wishbone with a pinch bolt connecting it to the hub.

[tiger99]

Thinking about that some more, the MK 1 Metro as far as I know has twin circuit calipers with two hoses. That would be to avoid nasties by keeping the front braking symmetrical in the event of a failure. So presumably the MK1 Metro has positive scrub radius?

[Spider]

The MKI Metro has a split front / rear braking set up, but the front callipers are also split and are twin circuit in themselves.

 

It does have a positive scrub radius, but not from suspension arm or hub design, it's from the wheels, they have a heap of positive offset, to the point where the mounting face is about in line with or possibly outside the outer mounting flange of the rim.

[mini13]

interesting,

 

obviously I have done a full bump/droop check on my metro hubs on mine when fitting and they were fine, but will make a point of doing it again if I change the balljoints. one thought, could it be you checked the later 1984 onwasrds jonts with the fatter pin? which dont fit mini arms anyway.

 

 

 

Rewind 1 year:

 

Metro hubs don't have nipples, the BJ's are sealed and have male threads to go in female threaded hubs. The taper on the pins also changed, so only early ones will fit in Mini arms.

 

yeah, yeah yeah,,, we established that at Post #2 - best keep up mate

 

BUT

 

Now you mention it and on a very serious note.

 

If (for what ever reason) one is going to run with Metro Hubs *** CAUTION ***

 

Ball Joints for Metro Hubs are NOT all made the same.

 

On a Mini, the Ball Joint needs a minimum of 52⁰ swivel angle of the pin. Original Mini Ball Joints have 55⁰ of movement before lock.

 

The Austin Rover Boxed MKI Metro Ball Joints have 52⁰ of swivel movement, no issues there.

 

However,,,,,,

 

The ones that come out of Quinton Hazel boxes only have around 44⁰ of swivel angle. I haven't actually measured them exact as it was clear from the outset that they fall well short and will break if used on Metro Hubs fitted to a Mini.

 

[mini13]

I'll split this into a seperate post as it diverges from what I put above,

 

is the 10 deg KPI a bad thing? obviously there is a fair amount of geometry cjhanges anyway and the metro hub should not be considered a direct replacement, but with a bit of fiddleing they can and do work.

 

somethig Ive already alluded to befor is suspesion is a very dynamic thing, if it wasnt we would all be running zero camber and zero toe, bump steer is always present just to differing degrees, and as the OP has done its a good idea to minimize this over the working range. somthing overlooked when fitting the metro hubs is that you should use the metro steering arms, the inboard suspension arm points are in a similar position to the mini ( i have a feeling they cut and stretched a mini subframe in the factory as a starting point) so if you use the steering arms and lengthen the bottom arms to reset the camber you get close to a workable setup, also the longer metro arms act as steering rack limiters, and as a "slow rack" which  again helps feel IMO. also it moves the ackerman closer to zero, not great in a car park, but arguabley better on the move.

 

another note on scrub radius... where is it? depends what the car is doing in terms of roll etc, I think of the scrub radius in terms of where the average load on  contact patch of the tyre is highest, rather than where the geometric points intersect, if you have a bit of negative camber the "scrub raduis" will effectivly move inwards reducing torque steer ect...

[mini13]

that said, anything you can do to directly move the geometric scrub raduis inwards is a good idea on the mini, eg no spacers, no low/negative offset wheels ect,

 

I started with the metro hubs with metro turbo flanges with 7x13's (-7et) and mini steering arms which was diabolical..... actally lethal when it came on boost. I ditched the 7x13's for 6x13's with a much larger et, and swapped to mini drive flanges, this moved the SR in by aprox 28mm, much better! but still felt strange, swapping to the Metro arms got t driving like a normal car.

[Spider]

 

interesting,

 

obviously I have done a full bump/droop check on my metro hubs on mine when fitting and they were fine, but will make a point of doing it again if I change the balljoints. one thought, could it be you checked the later 1984 onwasrds jonts with the fatter pin? which dont fit mini arms anyway.

 

Only last week I had my hands on the MKII Ball Joints. As they don't fit our Arms, I didn't take them off the counter, however they did very much appear to be the same in every way, except for a slightly thicker pin on the taper, as the MKI types.

 

The other 'thing' to check is that although the Metro Joints may (or may not) have enough swivel angle, if their fitted / mounted angle in the particular hub being used (Metro, KAD etc) is different to the Mini ones, then trouble will be encounter.

 

I'll also clarify, that in the interests of safety, I do these checks without the Bump Stop or Rebound Stop in place, so that if in use, one or the other (or both) get damaged, at least then the you won't find out when the ball joint breaks. Note that stock Mini Ball Joints will also work over this range without issue.

 

 

I'll split this into a seperate post as it diverges from what I put above,

 

is the 10 deg KPI a bad thing? obviously there is a fair amount of geometry cjhanges anyway and the metro hub should not be considered a direct replacement, but with a bit of fiddleing they can and do work.

 

somethig Ive already alluded to befor is suspesion is a very dynamic thing, if it wasnt we would all be running zero camber and zero toe, bump steer is always present just to differing degrees, and as the OP has done its a good idea to minimize this over the working range. somthing overlooked when fitting the metro hubs is that you should use the metro steering arms, the inboard suspension arm points are in a similar position to the mini ( i have a feeling they cut and stretched a mini subframe in the factory as a starting point) so if you use the steering arms and lengthen the bottom arms to reset the camber you get close to a workable setup, also the longer metro arms act as steering rack limiters, and as a "slow rack" which  again helps feel IMO. also it moves the ackerman closer to zero, not great in a car park, but arguabley better on the move.

 

another note on scrub radius... where is it? depends what the car is doing in terms of roll etc, I think of the scrub radius in terms of where the average load on  contact patch of the tyre is highest, rather than where the geometric points intersect, if you have a bit of negative camber the "scrub raduis" will effectivly move inwards reducing torque steer ect...

 

Bhahaha,,,, forgot to come back on this part!

 

10 degree KPI a bad thing?  Dunno, I haven't analysed it, but the location of the arm pivot centres and length of arms also come play here and off hand, I'll say that the design (and KPI) between these components is inter-related and so simply swapping and changing form one to the other isn't as straight forward as it may first appear.. I'll agree that the Mini and the Metro have similar pivot points, but given one has 10⁰ KPi and the other 8.5⁰ KPI, I can;t see that they would be 'the same'.

 

Another factor that screams out to me that the Metro is significantly different to the Mini is the wheel off-sets between the models, it's chalk and cheese.

 

Maybe too, I just over analyse this stuff,,,,,,,

Edited by Moke Spider, 28 September 2016 - 09:34 AM.

[Ethel]

KPI is always going to be added to, or deducted from, the caster, so it will always be compromise on the Mini geometry - not that it can't also be an improvement. It's just nice to have another option to get roll, caster, camber and offset working for you.

 

Thinking aloud again, how much difference will longer steering arms actually make? If the rack is in the same place, its axis will still intersect the steering arm in the same place, giving the same lever rate. Of course, it's much more complex given there will be differences in the other 2 dimensions.