Steering box to rack conversion

I'm doing one on my standard 10, If you look at the original system it should give you most of the lengths you need, the track rods need to be almost the same length as the bottom arm, that should deal with bump steer. This will dictate the length of rack, most manual racks can be cut down I used a escort mk2 item as the splines on input are the same as currently on car and the track rod ends are the same thread. I had to cut the shaft down by 60mm and the body by 55mm (the difference limits the travel of rack to stop my wheels hitting the inner wing)

The rack then needs to be mounted so the track rod lies at same angle as bottom arm. Most of time this layout is already there so it is just a case of finding/modifying a rack to fit.

What i'll be doing with my car to hook it up is I got 2 group 2 Uj's and a 400mm splined both ends connector rod thing (i'll shorten this), shorten the column shaft then join it all together.

Then you need some beefy brackets and a sparky gun.

planning this on my p4 over the winter.....thanks for the tips

^^ agreed^^

avoiding suspension inputs effecting your steering is about parallellograms, not outright level-ness.

what damien says about putting the trackrods at the same angle as your bottom arms will give a far better driving setup.

bumpsteer is caused by triangles of forces which happens because most steering setups are compromises and have components that move in a different arc to the suspension, leaving the forces inflicted by wheel movement with nowhere to go other than feeding back through the steering system.

front to rear placement of the rack is also pretty critical in avioding bumpsteer- too far back or forward and youll get the same thing happening.

You don't HAVE to achieve the desired geometry purely by rack position - it is possible to modify the hub to relocate the steering knuckle as well if you are reasonably competent at fabrication - e.g. if your steering arms are angled upwards when the lower wishbone is level, cutting the knuckles off and re-positioning them further down the hub will have the same effect as moving the rack upwards.

You may also find that you need to lengthen or shorten the steering knuckles to get the desired amount of steering lock per turn of the wheel - you can shorten simply by redrilling if the rod ends are not tapered fit. This obviously effects the weight of the steering as well - shorter knuckles (moving the point the rod end bolts in closer to the hub centre line) will give more lock per turn, but result in heavier steering.

I did this earlier but only just got round to posting it.



I did mine so when pointing straight ahead the rack is straight when viewed from above (red line). Thats the forward/back position sorted (this could be wrong but its what I did, most cars I looked at were like it so it must be alright). Then you'll need the track rods to run parallel to the bottom arms (like robinJI's illustration above), you'll need to know what track rods you are using for this as the height varies a bit. That should give the height the rack needs to be mounted at.

Once you have worked all of that out you can then work out the length of the rack, the inner joints should be aligned over the yellow lines going through top and bottom inner arm pivots.

Few more things now the kids are sleeping. Theres a aston martin powered p1800 that uses a tr4 steering rack. I don't know much about it but could be a good place to start. Shortening a rack is quite easy if you know someone with a lathe, extending track rods is straight forward too so most issues can be overcome fairly easily.

Another thing i forgot to mention although you might be alright looking a the pictures, you'll need a bearing to support the steering column where it comes through the bulkhead if you use UJ's, the one on the standard has a bearing under the cowl and the other end was only supported by the steering box as it was straight through with a little rubber coupling.