So, this sort of thing usually gets easier with more variables nailed down. What do we have so far? I'm guessing you can fill in these blanks to some degree:
Doing a little math should get us your approximate "ideal" steering rack width, which we can then worry about packaging in a way that doesn't give you wacky bump steer or anything.
In reply to ¯\_(ツ)_/¯ :
Actually, I'm going to start with the strut tops, which will then dictate track width, and lower control arm length. Luckily, MR2s have adjustable eccentrics built into the strut mounts. I'll set that in the middle, and build to my target 1 degree negative camber. The front trailing link location is nailed down as in the stock X1/9 location.
There is rust, and crash damage at the stock Fiat LCA mount on the passenger's side, so I believe my plan is to cut til I can install a new square tube crossmember in the general area. This will be my datum to build off of.
Here's a comparison of the two car's stock specs:
X1/9 MR2
ground clearance 4.9" 5.7"
castor F 7 degrees+-1/2 5.38 (6)
camber F -1/2 degree+-1/2 +0.25 degree (1.0)
camber R -1 1/2 degree+-1/2 -0.75 degrees (-1.5)
toe in F 5/64 to 15/64 +0.06 (+0.12)
toe in R 5/32 to 15/64 = 0.41 (0.24)
Note, I believe the Rear toe in for the Fiat should be 5/64 to 15/64. Numbers in parentheses are a performance alignment I dug up on line.
So, yeah, I've got some building to do before I know the variables that will determine track width.
In reply to wheelsmithy (Joe-with-an-L) :
OK, in theory then you could measure (approximately) your strut top locations and give their height above the ground and we could work backwards from there instead. Basically I'm trying to see if we can find you some steering rack options that will give you more to build off of.
In reply to ¯\_(ツ)_/¯ :
Cool. I am working through this in the only way I know how. My background is largely as a fabricator, so I'm leaning on that. My thought was to get the crossmember installed, get a good centerline scribed, and start experimenting with tie rods. Once I can find a placement that looks good, I can measure for rack width and placement. In this car, I am leaning towards cutting the interior wall of the rack tunnel out so I can rebuild it strong with its new mounts.
Please feel free to correct me on anything I'm doing, or offer suggestions or insight. I clearly don't know what I'm doing. Hopefully I will before it's all over.
In reply to wheelsmithy (Joe-with-an-L) :
That's a totally valid technique for getting this done, my only real concern is that it might result in you getting a "perfect steering rack" measurement that doesn't match anything you can get on a challenge budget so my inclination is to try and get a ballpark number ahead of time and set the GRM hivemind to work on finding a rack that matches- mainly because that's something I know I can help with right now.
In reply to ¯\_(ツ)_/¯ :
Aaah, I see. The thing is I have a rack from the PT Cruiser donor. Right now, it is maybe < 1" longer than the LCA mounts are wide. The mounts I just cut off the car. My plan involves cutting this rack down because 1. no budget hit 2. I have it in hand 3. I can use the PTGT column, 4.I want to learn to cut down a rack.
I fully respect your approach. Keep the ideas coming.
My first front suspension on my V8 Firefly was to use all '88 Firebird parts. Except the struts wouldn't fit with a car nine inches narrower, and the lower arm wouldn't fit due to packaging.
The next version was fabricated lower arms using Firebird arm length, and S10 upper arms. Except the S10 uppers wouldn't fit.
The next version was fabricated lower arms with fabricated upper arms arms. Except the fabricated lower arms in Firebird length wouldn't fit AND give suspension travel AND to minimize bumpsteer, I would have had to shorten the Chevette rack a full 12" - that didn't leave much workable width. Much less brackets to hold it.
So I cut it all out, and designed a whole new suspension around the unmolested Chevette rack width. It ended up with shorter a-arms which might not be awesome, but compromises have to be made. Parts and Packaging will rule your design.
I figured basing it around a stock, available rack, mean easy servicability. I felt that it was easier to re-make a control arm, than to modify another steering rack.
I alwasy think "servicability" and "parts availability."
Ok so did a little digging. PT GT rack is 46" wide, let's assume you need a little narrower- here are some options that should be findable cheap in the GRM circle:
Ranger/B2300 44.25"
2001 Accord 41.75"
2003 Camry 43.9"
2003 Corolla 42.9"
1992 Tercel 44.25"
and just for fun, mystery manual rack from my parts stash: 25.5"
What matters is the width from inner pivot to inner pivot.
You need the tie rod end arc to match what the spindle is doing.
If -I- were doing all new suspension in an X1/9, I would switch to double wishbone and get a decent camber curve going.
Rules be danged - just move up a class. Or two.
One of the variables working against me here is Challenge budget. I haven't added stuff up, but it's going to be tight. The idea of double wishbones and factory racks is enticing, but these are the corners I chose to cut. Also, a stock X1/9 is considered to be one of the most sublime handling car of all time, struts, bump steer, and all. This car will be totally outclassed in sanctioned autocross. I'd be running with tube framed carbon fiber 1000 horsepower pro driven stuff.
The PT rack I have is about 26" inner tie rod to inner tie rod. It appears solid, as well, which makes it a simple cut and tap (I hope), and narrow the housing. It needs to be de powered, also, so it's getting some surgery anyway. As an added bonus, the stock outer tie rods appear to taper the same as my MR2 uprights.
Nonack, are all those rear steer? How about your mystery rack? 25.5 is pretty close to what I'll need
In reply to wheelsmithy (Joe-with-an-L) :
Not sure, I'm just going off of listed rack lengths on Rock Auto but something must be funky there given the listed length for the PT cruiser vs. your measurement. The mystery rack is really, really skinny and manual, you can probably orient it however you want. I can get pictures and measurements if needed.
The rack widths in the 20's are inside-to-inside.
The rack widths in the 40's are outside-to-outside.
In reply to ¯\_(ツ)_/¯ :
Measurements are cool, but it's still a part I can't put my hands on for a while(ninja edit for clarity), and as such, the point could be moot. If you're bored/motivated, post some pics get some measurements, and see which way the rack goes, if not, no worries.
You can't deny the allure of a mystery rack.
Oh, and I bet Skinny's exactly right on his guess.
Before using the PT rack occurred to me, I was looking at Geo Metros and Rabbits as they have similar rack widths, but thought they might be geared pretty slow.
To continue the conversation, I've got plenty of room for roll center adjusters.
And a picture of the PT rack.
Obviously, without tie rods.
A de-powered power rack should have a pretty quick ratio, if you didn't want to keep -power- steering.
In reply to SkinnyG (Forum Supporter) :
My thoughts exactly, and no, no power steering on this car.
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