mk1-forum.net

Could anyone tell me all the variations of the above, and the consequences of using the wrong ones?
E.g using mk2 drum / 7" disks ones on an S disk setup .. etc
Thank you in advance!

There have been a couple of queries on this subject John including one correcting the mistaken belief that S arms are made from a 'stronger/superior/better material. There's also a dimensioned drawing of the angles relating to Mk1 and Mk2 arms.

The long and short of it is that Mk1 steering rack = Mk1 arms. Mk2 steering rack = Mk2 arms and never the twain should meet.

But, alas, I'm not computer search savvy. But I bet someone who is will soon identify where the thread(s) are.

Peter Laidler wrote: ↑Fri Mar 29, 2024 1:51 pm There have been a couple of queries on this subject John including one correcting the mistaken belief that S arms are made from a 'stronger/superior/better material. There's also a dimensioned drawing of the angles relating to Mk1 and Mk2 arms.

The long and short of it is that Mk1 steering rack = Mk1 arms. Mk2 steering rack = Mk2 arms and never the twain should meet.

But, alas, I'm not computer search savvy. But I bet someone who is will soon identify where the thread(s) are.

What is the difference between the MK2 S arms and the MK2 'normal' ones Peter? And can you actually fit MK1 arms to a MK2 .. I mean I know all the angles would be wrong but will they physically go on ..

Hi John. I hope that someone comes on board to correct me if I'm wrong. But from memory, materially/metallurgically speaking, there is no difference between the supposed S steering arm and the normal steering arm. When I had use of the met. lab, we found that there were slight steel tolerance differences but they were well within the steel mix acceptable allowances. Like most steel mixes. Spider also found this too (?)

The geometry of the hub is the same so a Mk1 or Mk2 steering arm will fit to any hub. Likewise, you could fit Mk1 track rod arms to a Mk2 st rack. But IT MIGHT NOT BE THAT SIMPLE because the recessed ball-cup, fittings and springs in the rack might not be compatible with the balls on the ball-ends of your track rods

It gets a bit dodgy during the changeover period between Mk1 and 2 racks when there was a bit of a hybrid period.

To simplify it. Some track rods have a FULL ball while the earlier ones have an inner and outer ball of different diameters and therefore different ball seatings and springs. So take it carefully if you are building one rack from several. To be honest, I'd settle for the Mk2 peg-centralised rack and arms whether a Mk1 or 2 car. Visibly there's no real difference

No difference in geometry between MK2 normal and MK2 S?

Nope! It is this different Mk1 v Mk2 arm geometry and rack that gives the Mk2 a tighter turning circle.

Geometrically, this was the difference between the Arms;-



The consequences of running the wrong Arm / Rack combination is increased bump steer. Also, if running a MKI Rack with MKII Arms, and stock Rod Ends, the Rods ends will only be engaged by a few threads, dangerously so. The factory recommended a minimum 1/2" engagement of thread with these. If you still wanted to run this combination, you can use the longer HD type Ends, but as pointed out by someone on the forum here, these also have a lower ball centre that further messes with the steering geometry.

As Pete already mentioned, the all Arms are forged from the same grade of steel (EN16 from memory), however there were some Arms that were 'wider' than others, these are loosely referred to as Cooper S Arms, though, they were fitted to other models as well, however, as noted by Pete, they have the same geometry as the thinner arms of the type (MKI or MKII).

The 'Ears' appeared on the Arms to suit the factory disassembly tool that was introduced at the time.

There was actually about 7 different types of Arms used in production at various times.

Peter Laidler wrote: ↑Fri Mar 29, 2024 4:55 pm Nope! It is this different Mk1 v Mk2 arm geometry and rack that gives the Mk2 a tighter turning circle.

I ran a Mk2 rack with Mk1 arms. Good for autotesting ..... until the cv joint exploded on full lock

johnv wrote: ↑Fri Mar 29, 2024 2:08 pm

Peter Laidler wrote: ↑Fri Mar 29, 2024 1:51 pm There have been a couple of queries on this subject John including one correcting the mistaken belief that S arms are made from a 'stronger/superior/better material. There's also a dimensioned drawing of the angles relating to Mk1 and Mk2 arms.

The long and short of it is that Mk1 steering rack = Mk1 arms. Mk2 steering rack = Mk2 arms and never the twain should meet.

But, alas, I'm not computer search savvy. But I bet someone who is will soon identify where the thread(s) are.

What is the difference between the MK2 S arms and the MK2 'normal' ones Peter? And can you actually fit MK1 arms to a MK2 .. I mean I know all the angles would be wrong but will they physically go on ..

The hubs where the arms bolt on are the same, my mate had a bad handling 8 port rally car, I crashed it cone night testing, we fitted a Mk2/3 rack & arms, hey presto - a great handling car.
One of the things I did when I got my car home after nearly putting it through the hedge was fit a Mk2/3 rack & arms

this is as accurate as I can get .. pretty sure these are mk2?

johnv wrote: ↑Sun Mar 31, 2024 10:26 am this is as accurate as I can get .. pretty sure these are mk2?steering arm.jpg

John, they sure look that way.

Very interesting information. Does anyone know what arms you should use with the "quickrack" that MiniSpares sell? Mk1 or Mk2 arms?

I had a Quickrack on my Elf ~30 yeas ago and it suffered from appalling bump-steer.
I've subsequently read somewhere that the Quickracks are the original-original Mk1 rack which was ditched for making the car too twitchy for public consumption. If that's true, and Spider has mentioned bump steer above, then I'd be tempted to say the Mk1 arms maybe better than the Mk2s I had fitted.

I fitted a Mk2 rack on a Mk1 S many years ago to take advantage of the tighter turning circle. For reference I used David Visard's original "How to Modify your Mini".
For those who have a copy available the relevant information is contained on page 171 but for those who haven't in this section regards converting to S discs, of the rack/steering arms it reads:- ..........."but when you do so, be sure the steering arms you use match the steering rack. Let me expand on that. When the Mk2 mini came out, an alternation was made to the rack. The number of teeth were altered and also the effective length of the rack.This was done to achieve a tighter turning circle. To compensate for this, the steering arm was also made different.The Mk2 steering arm put the track rod end nearer the hub. If you have a Mk1 steering rack, the one with 15 teeth on it, then you MUST use Mk1 steering arms. If you are using a Mk2 rack, then you MUST use Mk2 steering arms."
There is also a picture of the 2 arms overlaid which shows the differences.

When I fitted a Mk 2 rack to my 1071 I also fitted the Mk 2 steering arms. A friend didn't bother with the Mk 2 arms. He claims he never noted any difference ... but he didn't actually compete...

I was told it had something to do with Ackermann angles...

Cheers, Ian