Mazda rack?

[Francis Lucas]

Hi, since my scratch-built is going to get a whole new chassis built, I've been considering switching it to RHD. Currently it uses the Mustang II type suspension including the rack. I have access to a 3rd gen. RX7 RHD rack for free, is this a decent rack to start with and as it's a power rack can it be used in manual config? I may also be able to get the entire front suspension, would this be an improvement? I'm hesitant to ditch the MII set-up due to the huge aftermarket support it offers.

Suggestions?

Francis

 

[David]

If you're after powersteering I'd be tempted to go either RX-8 or GM/vauxhaul/Opel Corsa with any generic quick rack as they are electric systems and avoid having to add a hydraulic pump and loads of plumbing (not a problem when the engine is next to the rack, a pain when its 2m away!)

Otherwise you can run a electric pump (Citroen Saxo has one IIRC) to drive the hydraulics.

 

[Francis Lucas]

Thanks David, my intention is to keep the car with manual steering. I looked into this a little more and found a lot of the RX7 guys are converting their power racks to manual. Looks like a fairly straight forward procedure. Here it's demonstrated on a similar Miata rack: Flyin' Miata : Tech: 1.8 conversion

Now the question is to use thias rack with the MII suspension or use the RX7 setup?

 

[John Milmont]

It is popular to convert the power rx-7 racks to manual in the old FC rx-7. But, if you do this, you will not be able to run a parking lot auto-x with much success. A friend of mine had a turbo II with a manual rack and he was not even in league as my N/A FC with power steering on those tight courses.

You also understand that the pickup points for the steering rack are an integral part of the suspension geometry, and if its not right, you will get uncontrollable bump steer.

 

[Francis Lucas]

Thanks John, I've read mixed reviews on how much more difficult it is to steer with the conversion. I do understand that steering effort is quite high (but managable) at low speeds.

In terms of the pickup points of the rack. do you mean the mounting points in relation to the rest of the suspension? That's one of the things I need to review when I get the rack, I was thinking it should be installed such that the tie rods are identically located in all three planes as the current rack. Is this a correct assumption?

I'm also considering installing the entire front clip from the RX7 as it may be available and is already quite light, with large rotors/calipers and the 5 x 4.5" lug pattern I need. What is your impressions of the Mazda setup? I suspect it's likely better than the 1970's design of the Mustang II setup I have now.

Open to all options at this point and hope to avoid any "I wish I had" moments in the future.

Any and all input is welcome, thanks!

Francis

 

[David]

Francis, sorry my misreading of your original!

Anyway, you can't go far wrong by taking an existing setup and duplicating the locations of everything, either by using the existing subframe or putting the mounts in the same place.

If your don't you either need to spend some significant time with a computer (although can be kind of done with string and bits of card) working out how everything will work together and adjusting the suspension accordingly.

Although you can do the maths yourself if you're good (it can even be done in excel), there are some very good and not *that* pricey software packages out there for working out suspension, I'll check my 'library' later to see what is suggested.

 

[John Milmont]

There's a lot of information on setting this up on the internet. I remember there's really good wikipedia articles on how to do all of this.
You can actually calculate how much force will be required at the wheel to turn your car. If you do all the math, you can figure out if you need power steering or not!