SR Coupe rack and pinion steering

[turbora28]

I'd need to confirm this, but from memory the KE70 one is 590mm inner tie to inner tie.

[crispy'86]

What i was referring to shortening was not exactly shortening it physically, sorry. I should have said, and this may sound bloody ridiculous but if the rack ends could be wound in like it was going to be adjusted for a wheel alignment, to give it more toe out on both sides,
Joe, i will measure the distance from knuckle to knuckle relating to the distance between the bolt holes for the lower control arms and get back to you if i get stuck or even to see what it comes to in difference

[fangsport]

Chris, pulling the tie rod ends closer to the rack won't fix your problem, it will amplify it. not only will you have massive bump steer, but you also massive toe out as well. i'll measure the escort rack tonght and report back

[turbora28]

Sorry I made a mistake in measurements...

The RA28 celica, control arm pivot points are 590mm apart.

The KE70 rack inner tie rods are 620mm apart.

So at that point the rack is 30mm too wide for my car cuasing bump steer. Also if you take into effect the ackerman angle designed into the steering knuckles, this is around a 15mm offset from ball joint to outer tie rod.

So this makes the rack somewhere around 30mm too long each side.

I am going to be fitting some AE86 power steering knuckles/steering arms which are around 15mm shorter than the RA28 items. This will make steering heavier but will give slightly more turn and also enable me to lengthen the tie rods by 15mm each side (might need longer tie rods to ensure enough thread).

So yeah, after that will still be 15mm or so too wide. So a shorter rack would be good otherwise might be able to shorten the KE70 this 15mm.

Cheers
Joel

[crispy'86]

Good point joe, i will be neasuring the rack today to compare it to my crossmember. If i get stuck surely there will be something a bit shorter if needbe.

[AE25]

confused here... how does adjusting the tie rods change the bump steer? tie rods are adjusted to give the correct toe angle. and how does the ackerman affect it also? as i understand if the inner tie rod ball joints are same width as the control arm pivots then the toe angles will not change when suspension travels up and down. having shorter steering arms will not change the fact that the rack is wider than the control arm pivots. please explain... im learning

[fangsport]

Mark, you understand good .

[AE25]

heres some basic steering info
http://auto.howstuffworks.com/steering.htm

[turbora28]

AE25 - you are right in saying tie rods are primarily adjusted to set the toe. But I am more refering to the total length of the tie rod (inner tie to outer tie) vs. the length of the control arm pivot point to balljoint.

Lets say the control arm pivot points are 300mm apart, then you have a tierod length of 270mm, there will be bump steer.

Now you cant just go and lengthen the tie rod another 30mm or you'll have huge amounts of toe in. But, if you can shorten the rack 30mm, that means you need to lengthen the tierod/steering arm 30mm. Which then makes the control arm and steering arm the same length.

In my case, i'm going to put a shorter steering knuckle on, which for the tie rod to reach it will need to be extended, so the tie rod length will be getting closer to matching the control arm length.

This doesn't really affect the ackerman much. But I mentioned it as the steering knuckles are mainly what creates the ackerman effect, and when measuring this all up you need to take that into account.

Its like you cannot just make the inner tie rod on the steering rack sit perfectly inline with the control arm pivot point because at the other end (ball joint & outer tie rod) they are not inline due to the offset, ackerman, in the steering knuckle.

In the RA28 there is a 15mm offset in the steering knuckle, so ultimately the steering rack inner tie rod needs to sit 15mm inbound of the control arm pivot point.

I hope that makes some sense! Hard to explain...
Cheers
Joel

[crispy'86]

Yes you are right, i am getting to grips with this. Doing an app. i am going to have to learn all this.

[crispy'86]

so far i have only measured the crossmember bottom arm pivot bolts, haven't had time to measure rack inner. Crossmember bolts are 560mm centre to centre

[fangsport]

looks like you need to shorten the rack then. i'd have to have a look at a spare *E70 rack and see how hard it is to do.

nothing is impossible, just some things are impractical.

Chris, if you have some time up your sleeve, go to a wrecker and measure up some different racks, maybe some like a (dare i suggest it )honda city or a suzuki alto or similar might be narrow enough.

[crispy'86]

Alright thanks Joe, will have a look at a few "OTHER BRANDS" and see what i come up with

[fangsport]

Chris, what about the FXGT, might be worth a quick flick with the tape.

[gdsup]

jess from boosted performance used a kp60 rack in his yellow 4ag turbo ke26, using original crossmember and fabricating brackets and ke30 colum, not sure as to how this would affect bump steer etc, if you feel the need you can contact him bussiness hours 09-532-8950

[crispy'86]

yeah that's a point joe, i got a spare rack with the fx too just gotta dig it out of the boot, could be worth a look all the same. Haven't had the chance to look at racks etc as yet, still trying to get this engine sorted as in fuel pump wired up check for any fuel leaks in system fit fuel filter then crank it over and see what it does. That ke26 idea may be worth a look but bump steer is a big issue

[turbora28]

I'd really like to hear how wide these KP60 racks are.. We don't get them here in Australia.. So keep me posted guys!

Cheers
Joel

[AE25]

came across another ke20 with a starlet rack this time on www.club-k.co.nz
emailed him and he's replied with these details
his car pics here
http://f2.pg.photos.yahoo.com/ph/headdavey/album?.dir=/91a9&.src=ph&store=&prodid=&.done=http%3a//f2.pg.photos.yahoo.com/headdavey
he probly cant say much more than this...

The bottom arm is off a ke30, hes made up a custom crossmember and put in adjustable camber bolts.
ill try and take some close up ones with the wheel off
Steering rack is out of a starlet,not sure what model sorry.
starlet tie rods and just ke30 struts
not sure what model sorry
he used the whole steering column
he just mounted it on the cross member
not really too sure on the technical details, as most of the work has been done when im not there

[crispy'86]

hmmm seems he made a template up and mounted the rack onto that. not long till i can drive car on road and serioudly nutting this out i.e. putting design on paper to practical use