11 replies to this topic

[austinmini1963]

Hi Everyone,

 

I have heard that you cant fit a mk2 or later rack on a mk1 over the years but never any solid reasons behind it.

 

Looking online someone said the mk1 rack has less travel than the mk2, along with that the steering arms are different. I guess the mk1 ones are shorter to get the extra turn, so if you have the mk2 rack on mk1 arms does it turn the hub too far?

 

Any thoughts?

[Spider]

You can fit either Rack to either MK. The difference between the Racks as you've touched on is the travel, the MKII racks having more.

 

However, you should also keep the right Steering Arms (the arms that bolt on to the hub) with the matching Mack, ie, there is MKI and MKII Steering Arms.

 

[austinmini1963]

Thanks for the response, I did a few calculations from your drawings and found that the length of the steering arm on the mk2 is 0.03 inches (0.77mm) longer than the mk1. Which wouldn't massively effect the amount the hub moves (less than half a degree).

 

The only other obvious difference is the mk1 arms bend further inwards towards the car, which might mean the mk1 rack is physically shorter than the mk2. Meaning the mk2 rack on mk1 arms might not give you the adjustment needed to get the track right.

 

I mainly asked this question as I un knowingly fitted a mk2-on rack to my mk1 about 4 years ago before I knew about the differences. I haven't yet had any issues with it which is why I wanted to find out why you shouldn't use it. I will try and find overall rack measurements and post them on here for peoples future reference.

 

Thanks for the help, Tom

[Spider]

I don't have the measurements to hand, but yes, a MKI rack is shorter than a MKII.

 

I've fitted up hubs that have had MKII Arms on Cars with MKI Racks and found there's not a lot of thread engagement in stock steering rod ends, so some care is needed. I also found that there is a lot more noticeable bump steer with this arrangement.

 

A MKI rack has only 15 teeth and a MKII has 25 teeth, however, to check by this method, you need to take the boot off.

[mini13]

as above, also there will likly be a difference in the ackerman angle, probably the m2 settup will feel better if its noticable.

[austinmini1963]

That's the difference then, the rack length, I don't think the ackerman angle will be affected as you are still moving each hub by the same amount. The only time this will be affected is when you have one mk1 and one mk2 arm on either side of the car.

 

Haha, I think the teeth amount only changes the turns lock to lock. The mk1 was probably less.

[GraemeC]

Mk2 arms on Mk1 racks will not have a safe amount of thread engagement of the TREs onto the track rods.
Mk1 arms on Mk2 racks will be OK (providing the TRE doesn't bottom out, which I doubt).

 

What Moke's diagram doesn't show is whether there is any difference in height of the TRE taper between arms - I don't think there is, but can't honestly remember.

[Spider]

The length of the main part of the rack between the rod end ball joints is longer on the MKII rack than the MKI and this makes a huge difference in the steering geometry.

 

austinmini1963, there is a change in the ackermann angle between the MKI and MKII arms, however, both were a compromise and neither ideal, however it is by making provision for the ackermann steering that also induces bump steer. In this regards, the MKI one is better than the MKII,,,,,,,,

 

 

What Moke's diagram doesn't show is whether there is any difference in height of the TRE taper between arms - I don't think there is, but can't honestly remember.

 

Taper is the same Graeme, between he MKI and MKII TREs and even the Ball Joints. Same in fact for around 80% of the cars on the roads that have tapered joints.

[johnR]

When setting up Ackerman on steering arms on the Toylanders I've built my research suggested the arms should follow a line to the centre of the rear axle/track - on that basis the Mk2 looks closer?

[GraemeC]

Taper is the same Graeme, between he MKI and MKII TREs and even the Ball Joints. Same in fact for around 80% of the cars on the roads that have tapered joints.

 

Not the dimension of the taper itself, but the vertical height of that end of the arm in relation to the top of the hub.  ie how far each bend down (rather than the bend 'in')

[nicklouse]

When setting up Ackerman on steering arms on the Toylanders I've built my research suggested the arms should follow a line to the centre of the rear axle/track - on that basis the Mk2 looks closer?

and very few modern cars use true Ackerman.

[Spider]

 

Taper is the same Graeme, between he MKI and MKII TREs and even the Ball Joints. Same in fact for around 80% of the cars on the roads that have tapered joints.

 

Not the dimension of the taper itself, but the vertical height of that end of the arm in relation to the top of the hub.  ie how far each bend down (rather than the bend 'in')

 

 

Ah, OK.

They are the same.