Difference in Steering Racks?

[ukminis]

Hi all,

Ive a 64 Cooper S, In fact it's the very first west midland Police Mini, it has some odds bits on that I am currently removing and replacing with correct. I'm putting all new brakes on as been in a barn for 20 years plus, all is very good condition but not period correct, so am fitting a complete disc kit, it didn't include the MK1 steering arms so I've ordered these separately and now thinking as its got later bits on it (Assume this was done when restores 20 plus years ago) It may have a later rack on also, is there anything visual to tell me this? I do know the turning circle differ but what it the number of turns mk1 vs MK2 on? I know theres a difference but don't know the exact numbers? Assume someoone will.

Thanks ins advance.

Samuel

[Peter Laidler]

There is quite a lot about the Mk2 steering racks and compatability with Mk1 arms in some interesting threads on the forum, including a totally UN-intersting thread that I wrote on overhauling the Mk2 racks and steering generally. If I was computer savvy, I'd point it out to you, bit I ain't!

To identify a MK2 steering rack, you will see a white nylon UNC threaded grub screw on the left hand/passenger/nearside alloy housing. That is the centreing medium.. Plastic 1/4" grubscrew = Mk2 rack. NO grubscrew, Mk1 rack.

You MUST use Mk2 steering arms with the Mk2 rack otherwise there will be insufficient thread from the rack into the track rod ends.

You can put a Mk2 rack into a Mk1 car but, as above, providing you use Mk2 steering arms. The part number is usually cast in to the arms.

IThere are arms for the Coopers and arms for the saloons. Quite what the differences are is a bit of a mystery to me. In the lab both came back the same spec or certainly within the bounds of the steel mix spec.

Number oof turns of steering wheel in Mk1 v Mk2 rack - can't remember but it is in the workshop manual. Hope this helps

[underkut]

I seem to recall that if you use a mk 2 rack with mk1 steering arms AND use triumph herald track rod ends, they are longer than the mini and you would end up with sufficient threads from the rack into the arms.
I really cannot remember if I did this myself or just read it somewhere, But it must have been written down somewhere first as I would not have thought about it myself, but I definitely recall it.

[ukminis]

Thanks very much gents, I will have a look tonight and report back.

[woodypup59]

Number oof turns of steering wheel in Mk1 v Mk2 rack - can't remember but it is in the workshop manual. Hope this helps

Mk1 2.7 turns lock to lock - Mk2 2.3 turns L-L I believe.

[1071 S]

I think its the other way round....

My 65 BMC workshop manual gives the L to L of the rack (Mk I based on the publication date of the manual) as 2 1/3 turns.

Parnell's book also states that the MK II rack increased turns from 2.33 to 2.7.

I changed out my (Mk I) rack decades ago when I was motorkhanaing.. (auto tests I think you cal them) as the MK II rack reduces the turning circle by something like 3 feet... (I think Parnell suffers a typo when he quotes the MK I turning circle as 37ft 7ins???). (Just noticed he quotes (what I believe to be) the correct dimension on Pg 40 as 31'7").

I have friends who have run Mk II racks with Mk I arms for years in blissful ignorance. I was told that the mismatch makes for incorrect Ackerman (sp?) angles ... but those with the mismatch reckon that they never noticed a problem. ??

Cheers, Ian

[Peter Laidler]

Ah, they won't notice a problem Ian as the problem, such as it is, is hidden. There are only approx 5 or 6 threads of the rack engaging into the track-rod ends. Fine if you're unaware of it as ignorance is bliss as they say!

[Peter1071]

Hi all,

Ive a 64 Cooper S, In fact it's the very first west midland Police Mini, it has some odds bits on that I am currently removing and replacing with correct. I'm putting all new brakes on as been in a barn for 20 years plus, all is very good condition but not period correct, so am fitting a complete disc kit, it didn't include the MK1 steering arms so I've ordered these separately and now thinking as its got later bits on it (Assume this was done when restores 20 plus years ago) It may have a later rack on also, is there anything visual to tell me this? I do know the turning circle differ but what it the number of turns mk1 vs MK2 on? I know theres a difference but don't know the exact numbers? Assume someoone will.

Thanks ins advance.

Samuel

Mk1 Cooper S steering arms are hard to find in used condition and, to my knowledge, have not been reproduced. Are you sure that the arms you have ordered are Mk1 ?

Peter

[Peter Laidler]

exactly WHAT are Mk1 S steering arms. How are they different from a standard set? Or is it something to do with a casting number or just aesthetics.. It's not the steel compound that's for sure!

[Rubber Sprung]

The main reason for using Hearld track rod ends was/is when using longer bottom arms you get a safe number of threads engaging on the tie rods .

[Ronnie]

exactly WHAT are Mk1 S steering arms. How are they different from a standard set? Or is it something to do with a casting number or just aesthetics.. It's not the steel compound that's for sure!

Discussed at length on this forum Peter with input from yourself. viewtopic.php?f=3&t=31167&hilit=s+steering+arms

[1071 S]

The previous discussion adds some opinions but not much of use ...apart from one photo that REALLY needs explanation.

When I fitted my MkII rack (about 35 years ago) the experts (including Minispares who sold them to me) told me I needed matching Mk II steering arms ...and that these are identified by the "ears" cast into the non hub end.

The new arms were noticeably thinner than the Mk I arms fitted to my S. The local experts pointed out that the new arms were pretty much the same thickness as ordinary MkI arms although the angles were different ..which is what mattered. The Mk I S arms had the same angle as "ordinary" MkI arms... I didn't have any Mk II "S" arms to compare.

In a later discussion with a VERY successful Mini racer he told me they always used ordinary Mk I arms. The logic being that. if they hit anything hard enough to bend the arm then that was fine. They didn't want a stronger arm that didn't bend but might transferr the shock to some other less obvious and harder to change component.

The issue that really needs resolution involves Spider's photo that shows two "eared" (and therefore presumably Mk II arms) that have different angles.

Australian Minis din't ever adopt the Mk II (UK) rack. Our racks were Made in Oz and remained the same til the end of local production. The only eared arms I've come across in Oz were deliberately fitted by owners who had fitted later UK racks. (And not being a professional like Spider I've seen very few).

So, whats the story??

Are all "eared" arms indeed Mk II arms?
Do all Mk II arms have the same angle?
Does Spider's photo show a genuine Mk II arm and and an incorrectly specified aftermarket item?

And, of course, is there a definitive answer as to why the MkII arm has a different angle? Is it steering geometry ..or just to increase thread engagement??

Cheers, Ian

[ukminis]

Hi all,

Ive a 64 Cooper S, In fact it's the very first west midland Police Mini, it has some odds bits on that I am currently removing and replacing with correct. I'm putting all new brakes on as been in a barn for 20 years plus, all is very good condition but not period correct, so am fitting a complete disc kit, it didn't include the MK1 steering arms so I've ordered these separately and now thinking as its got later bits on it (Assume this was done when restores 20 plus years ago) It may have a later rack on also, is there anything visual to tell me this? I do know the turning circle differ but what it the number of turns mk1 vs MK2 on? I know theres a difference but don't know the exact numbers? Assume someoone will.

Thanks ins advance.

Samuel

Mk1 Cooper S steering arms are hard to find in used condition and, to my knowledge, have not been reproduced. Are you sure that the arms you have ordered are Mk1 ?

Peter

Hi Peter, They were ordered from Motorsport and people have told me its to do with treads, I am totally stripping it now to have it painted so I will update with some photos in the next few days. Thanks Samuel

[Spider]

If I can add a little in addition to that thread that Ronnie kindly linked up, I've always found that when running a MKI Rack and MKII Arms the Bump Steer is very noticeable, shocking in fact. These cars have Bump Steer as standard (and I'm yet to see just why they did that), but I find on normal road tyres, it's hardly ever noticeable when running the matching arms and racks.

The inner of the MKII rack is shorter than the MKI type, so the Rod Joints are closer together, with the result being there's a difference in geometry between them. I have sat down and drawn out the MKI front end and looked at how it behaves but haven't yet had time to look at the MKII arrangement.

Only a guess here, but I think the front end suspension is designed to work around the MKI Steering parts. The MKII I suspect was a bit of a 'fudge' in a few areas to end up with something that turns tighter and gives acceptable handling result. I stress, this is only my guess, I've not yet examined it in proper detail.

Sadly, I know of no supplier for the MKI Arms and always on the look out for them as that's what out Australian made Racks were designed to work with.

The last run of our locally produced Mokes, from about March 1980 were fitted with UK Made MKII Steering gear, though even then, there was 52 Mokes built with UK MKII Racks and Aussie MKI Arms. The UK Racks were modified here with the fitting of Lock Stops to (supposedly) prevent the wheels rubbing in the arches, which they all did anyway.

[Nick W]

exactly WHAT are Mk1 S steering arms. How are they different from a standard set? Or is it something to do with a casting number or just aesthetics.. It's not the steel compound that's for sure!

Mk1 S arms are much thicker/ stronger and don't have the ears of later mk2 S arms. Same dimensions as mk1 850, just stronger

Nick

[MrNoo]

I have in the past heated MK2 arms and bent to MK1 angle, worked fine but guess some of the purists wouldnt agree with it. It does work though

[Nick W]

I have in the past heated MK2 arms and bent to MK1 angle, worked fine but guess some of the purists wouldnt agree with it. It does work though

Yes that's what I was contemplating
Looks like the new mk2 arm would easy bend to mk1 dimensions. What's the best method for tempering, after, seem to remember quenching in oil, in metal work lesons?

Images from top to bottom
Mk2 S
Mk1 S
Mk1 850

[goff]

Nick i would think you would let them cool naturaly , i reckon that's what happened when they were forged , stamped out , thousands made , even after machining i cannot imagin them heating and dipping , but i could be wrong , have one tested if you are concerned to see what they are made up of , carbon content ect .

Goff

[Polarsilver]

Why would anyone intentional bend a steering arm .. when new steering arms are available from our favorite supplier.
If you must make sure that arms are crack tested after your bending.
dipping the hot component into old oil is to "blue" the item & stop corrosion on the component surface.

[Nick W]

Why would anyone intentional bend a steering arm .. when new steering arms are available from our favorite supplier.
If you must make sure that arms are crack tested after your bending.
dipping the hot component into old oil is to "blue" the item & stop corrosion on the component surface.

Good point, but Mk1 S arms are not avaliable for my enquiries