IRS knuckles

[RuffIndustries]

Hey guys, so i'm here to pick some brains. I'm currently working on an automotive project that will require me to put together a double wishbone rear suspension. While in search for components I came across this forum and the use of the T-bird IRS uprights/knuckles. I see the knuckles are still available for purchasing new. My concerns are the knuckle being to large for my application and the hubs being a ford 5 lug. My plan is to use a 13" wheel with honda bolt pattern and brakes setup. The car will also be FWD so I wouldn't utilize the shaft holes. Would anyone have any information on someone using these for a universal setup?
knuckles_standard_after.jpg

Few issues id have to hash out.
1) finding a source for a hub i could use with a 4x100 bolt pattern
2) getting a honda caliper mounted to the knuckle
3) finding the measurements to make sure its not to large.
4) producing a lower and upper arm for my application.

[Bob Cowan]

Have you considered Miata Components? Much smaller, and with the correct hub size and bolt pattern. A Mazda Rx7 rear spindle is similar, but beefier.

Consider this, though. The bearing is essentially held in place by the axle stub. Without the axle bolted in place and torqued to spec, the bearing will wobble until it destroys itself. In about a block - a short block. So you'll have to cut off an axle stub.



Have you considered using a front spindle from a rear drive car? Like a Miata or Rx7? Use the tie rod to control wheel hop and adjust toe in.




Shouldn;t be too hard to fab a bracket for the Honda caliper. Would be pretty easy to use a Miata or RX7 caliper and bracket. Or upgrade to Wilwoods.

[2bking]

The smallest wheel these knuckles will clear would be the wheel size used on the T-bird and the bearings require the axle shaft from the CV joint to load them thus you can't leave the hole unused. In your case you could cut the CV joint off the axle stub leaving the shoulder that bears against the inner bearing. I think you can get blank hubs and drill the lug pattern to suit the wheels you want to use or get 4 lug hubs and redrill them to your pattern but the rotor for the disk brake will need to have the same. The application they were designed for required 200+ ft-lbs of torque on the axle nut for preloading the bearings and keep the nut from walking back off. Since you are not driving any torque through the axle a much lower nut torque would work.

The picture shows a 17 X 10.5 wheel over the knuckle and the brake disk is a Wilwood 12.2 inch diameter and caliper. It is a close fit.
DSCF4504cd.JPG

[RuffIndustries]

Have you considered Miata Components? Much smaller, and with the correct hub size and bolt pattern. A Mazda Rx7 rear spindle is similar, but beefier.

Consider this, though. The bearing is essentially held in place by the axle stub. Without the axle bolted in place and torqued to spec, the bearing will wobble until it destroys itself. In about a block - a short block. So you'll have to cut off an axle stub.



Have you considered using a front spindle from a rear drive car? Like a Miata or Rx7? Use the tie rod to control wheel hop and adjust toe in.




Shouldn;t be too hard to fab a bracket for the Honda caliper. Would be pretty easy to use a Miata or RX7 caliper and bracket. Or upgrade to Wilwoods.

Bob, Thank you for the great information. I have at one point looked into the Miata parts. At that time I wasn't able to locate a source to purchase new components. I'll have to do a little more searching to see if there are companies manufacturing the knuckles and a arms. do you have any images where someone did a setup with the tie rod setup for adjustment in the rear? thanks again

[RuffIndustries]

Bob, Thank you for the great information. I have at one point looked into the Miata parts. At that time I wasn't able to locate a source to purchase new components. I'll have to do a little more searching to see if there are companies manufacturing the knuckles and a arms. do you have any images where someone did a setup with the tie rod setup for adjustment in the rear? thanks again

[RuffIndustries]

King, the picture definitely puts things into perspective. As feared the setup looks way to large for my application!

[Bob Cowan]

I believe you can get new spindles from Mazda. The early 90's parts are no longer available, but they are for cars built in this century. You can also buy billit aluminum drop spindles, if you want to spend the big bux. I have not seen pictures of people using Miata front spindles in the rear.

[RuffIndustries]

So a little update on information I've been gathering. After speaking with a few miata specialists it looks as if I can go either way, front or rear knuckles. If i go with the rear i would have to do what King said with the shaft so I can torque the hub. If i go front knuckle I would have to figure out a way to keep it straight, prob some kind of rod attached to the tie rod. I guess a downfall for the front is the issues they have with the hub bearings. The way they are designed they wear out fast.

I think what I'm going to do is purchase the rear knuckles, hubs and stock a arms. Once I have those i can gig up and try to produce tubular a arms and subframe using the measurements and geometry of the stock setup. I have no background in designing or manufacturing anything like this but with attention to details, taking my time and making gigs I think i can make it happen. Any information or advice to help me alone would be great! I'll check in as I can. Thanks guys

[CHOTIS BILL]

The suspension design is one of the most important features of a cars design. It can make the car a ball to drive or can cause evil handling. Using the measurements and geometry of the stock setup can get you going but you need to get accurate measurements because while some location points aren’t all that critical others are. For instance the location of the steering rack is very important and a small change in height will make a big change in bump steer. Another issue with using the measurements and geometry of the stock setup is you don’t know what design criteria was used when designing and there might be a benefit to making changes in the design it make it more suited to your project. I don’t want to discourage you just make you aware of things to be watch out for. There are many books that cover suspension design and how to do a basic layout by hand that might help you understand what the relationship of each part is to the others and how they interact. If you are interested in getting that involved with suspension design I can send you a list of design goals that may help. E-Mail me and I will send you the list.

Good Luck,

Bill Lomenick
[email protected]

[RuffIndustries]

Thank you so much Bill, and I do understand your points! Email sent

[CHOTIS BILL]

Something must have gone wrong I didn’t get you e-mail try sending it again

Bill Lomenick

[RuffIndustries]

Bill I sent again, maybe check your spam? [email protected]

[RuffIndustries]

I came across a setup exactly what Id like to duplicate in my project. Id be building with 1.5 tube but the suspension is what id like to see. Pushrod with the small coilovers. This will leave room in the frame to place the fuel cell.

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