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 Post subject: Upright/Spindle Question
PostPosted: Sun Jan 18, 2015 4:54 am 
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Hello all,

First, this forum is awesome - great information. I want to build a 1000cc two seater for track/street. I competed in Formula SAE for Univ. of Colorado 2005-2009.

Now, I want to start designing but the whole build really revolves around the wheel assembly. From what I have read, fiero/chevette spindles for the front are the best option, however they run 5x100. If I wanted to match up with 5x100 in the rear, which uprights would I be able to use? Subarus run odd geometry in the rear that isn't conducive to double a-arms.

Other option is to run miata all around, but the miata spindles do have some weird angles on them I'd rather avoid.

Plan is to run rod ends/sphericals everywhere, fabricate my arms, and run inboard dampers.

Last option is to mismatch bolt patterns front and rear, however that makes sourcing a used wheelset very difficult.

Thanks in advance for any opinions!


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PostPosted: Sun Jan 18, 2015 11:34 am 
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Go to speedway motors and look up pinto spindles . They are available with hubs for more common bolt patterns and there are many brake options also. It may not be what you are looking for but at least have a peek.

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PostPosted: Sun Jan 18, 2015 12:54 pm 
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Thanks. Cool site. It looks like you can get the mustang II/pinto 2"drop spindle and 5 x 4.5 hubs/rotors there. I will check into rear upright options which run 5 x 4.5 (114).


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PostPosted: Sun Jan 18, 2015 1:10 pm 
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A typical rear upright for this route is the Ford Thunderbird IRS unit. It is available in junk yards and also from Ford Motorsports new. If you buy it in a junk yard you get a 4.25" bolt pattern, but then you swap in the Mustang axle stubs I think.

The Pinto front uprights/spindles are available in at least 4 flavors. Generally you need to try and find wheels with a lot of offset to reduce the scrub to a moderate number.

The Miata front upright has a 30 degree angle on the bottom Ball joint mount, but you can put that into a fabricated arm or bolt on the stock ball joint etc.

I thought the rear Subaru upright was usable but didn't pursue it very far, do you think it is too short in height or something?

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PostPosted: Sun Jan 18, 2015 2:22 pm 
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Thanks for the info. I will look into the t-bird uprights.

I agree, I was trying to avoid that lower angle included on the miata spindles.

As for Subaru, the front runs a strut, so you would need an adapter to center up a rod end. Here is a photo of what factory five does on the 818 to make it work with a balljoint.

http://i.imgur.com/2pSbKJf.jpg
Image

As for the rear, it runs trailing arms, so the mounting points don't really work out at least as I am looking at it, for a double a-arm setup.

http://www.chargespeed.com/photo/imprez ... ts/top.jpg
Image


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PostPosted: Sun Jan 18, 2015 2:35 pm 
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I just found that some rx7's run 5x114.3. Inspiration from blue devil's excellent build.

http://www.vehicle-bolt-pattern.com/maz ... guide.html

One possible combo could be the mustang II front spindle 5x114.3 with 2" drop and the rx7 rear uprights.


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PostPosted: Sun Jan 18, 2015 4:53 pm 
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Quote:
One possible combo could be the mustang II front spindle 5x114.3 with 2" drop and the rx7 rear uprights.
Whoaaaa! There are much better rear uprights than the RX7. I did it, but would not do it again. Nor would I recommend it. The one lower pickup point is not an easy one to deal with.

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PostPosted: Sun Jan 18, 2015 7:43 pm 
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Quote:
As for the rear, it runs trailing arms, so the mounting points don't really work out at least as I am looking at it, for a double a-arm setup.


Wishbones and wishbones with trailing arms are sort of the same thing. At least sometimes. One method provide fore and aft strength directly with the trailing arm, and I think that's a good thing. The other means you have to build that same strength into the wishbones, but they mount to the upright the same way. I'm using trailing arms on my car ( with the T'bird uprights ) and I think they will work well. The only Seven I've seen pictures of from the factory with IRS used trailing arms too.

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PostPosted: Sun Jan 18, 2015 9:20 pm 
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rx7locost wrote:
Quote:
One possible combo could be the mustang II front spindle 5x114.3 with 2" drop and the rx7 rear uprights.
Whoaaaa! There are much better rear uprights than the RX7. I did it, but would not do it again. Nor would I recommend it. The one lower pickup point is not an easy one to deal with.


Thanks for the input. When you say there are much better uprights, which ones did you have in mind. Also, why did you find the lower pickup point difficult to deal with? I was planning on just running a grade 8 bolt through it and use spacers to center the rod end where I want it. It seemed much simpler then other options I have seen.

Here is an example of what I wanted to do, except I would run the stock toe link instead of running an extension off the lower pickup:

download/file.php?id=7558&t=1
Image

Quote:
Wishbones and wishbones with trailing arms are sort of the same thing. At least sometimes. One method provide fore and aft strength directly with the trailing arm, and I think that's a good thing. The other means you have to build that same strength into the wishbones, but they mount to the upright the same way. I'm using trailing arms on my car ( with the T'bird uprights ) and I think they will work well. The only Seven I've seen pictures of from the factory with IRS used trailing arms too.


I will look into this option, its just that geometry is a bit outside my comfort level. I am very comfortable designing a suspension system around double wishbones.


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PostPosted: Sun Jan 18, 2015 9:26 pm 
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The RX7 IRS uprights aren't that hard to design control arms for. I took a different approach than Chuck did. I just left the single lower pickup to connect to an A-arm. I used a separate toe control link attached to where the stock one does. The uprights are aluminum and both upper and lower pickup points are double shear.
Note: the 5 x 114.3 comes only on the turbo 2nd gens (87-92) and all 3rd gens (93-95). But, the uprights and diffs are not the same between these generations. For your purpose, the 2nd gen would be better because it's smaller/lighter.

The picture you supplied is a 3rd gen, and yes, I agree with the use of the stock toe link pickup.


Attachments:
2nd Gen RX7.JPG
2nd Gen RX7.JPG [ 960.65 KiB | Viewed 585 times ]
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PostPosted: Sun Jan 18, 2015 10:11 pm 
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seven13bt wrote:
The RX7 IRS uprights aren't that hard to design control arms for. I took a different approach than Chuck did. I just left the single lower pickup to connect to an A-arm. I used a separate toe control link attached to where the stock one does. The uprights are aluminum and both upper and lower pickup points are double shear.
Note: the 5 x 114.3 comes only on the turbo 2nd gens (87-92) and all 3rd gens (93-95). But, the uprights and diffs are not the same between these generations. For your purpose, the 2nd gen would be better because it's smaller/lighter.

The picture you supplied is a 3rd gen, and yes, I agree with the use of the stock toe link pickup.


Thank you very much for this info. This is my next step, determining a combination of diff, halfshaft, and upright that will all work out. I believe I have some work to do. When you say lighter, you mean the upright is lighter or the diff is lighter?

Looking at the link I posted earlier (http://www.vehicle-bolt-pattern.com/maz ... guide.html), it also looks like the earlier models may have 5 x 114.3 as well. I need to look into this further. I have never reserached rx7's so all these generations and differences are new to me.
RX7 GXL,GTU 86-92 15 X 7 5X114.3


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PostPosted: Sun Jan 18, 2015 10:27 pm 
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The 2nd gen upright is smaller and lighter than the 3rd gen upright. The 2nd gen diff is lighter than the 3rd gen diff. The 2nd gen diff housing is aluminum, but the pumpkin is rather long. The 3rd gen diff is shorter but massive. I use one in a V8 mustang.


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PostPosted: Mon Jan 19, 2015 8:18 am 
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A good rule of thumb when sourcing parts is to get them off the lightest car possible. Typically they will be significantly lighter parts. I used a 1989 Toyota Supra as a Donor they weight 3800lbs so all my suspension, brakes etc weight a lot mote then I would like. They should prove to be bullet proof though.

Now the car is built and running I am tring to save some weight so I am replacing all the brakes will smaller units. Wheel size is also something you need to consider. 13" are a nice size but to get that you need really small brakes.

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PostPosted: Mon Jan 19, 2015 10:43 am 
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Sorry, I had not picked up on the fact that your build is a BEC. Thus, disregard any of the info re diff housings. Also, if you're not intending to use 13" wheels for racing slicks then the 3rd gen uprights acceptable.

Ron


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PostPosted: Mon Jan 19, 2015 12:20 pm 
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Quote:
The RX7 IRS uprights aren't that hard to design control arms for. I took a different approach than Chuck did. I just left the single lower pickup to connect to an A-arm. I used a separate toe control link attached to where the stock one does.
That is what I did too, using the FC upright. The 2nd lower connection is actually an adjustable toe link. I had 2 issues to resolve. 1st was the toe link connection at the upright. It was not very easy to implement. I created a "cage" that bolted to the existing upright bosses. Looking at it today (literally, today) it could have been a lot easier to just turn the heim 90 degrees. The "adapter" would have been easier to build. see the attached photo for the existing complicated "adapter".

The 2nd issue I ran into was the stock brake calipers interfere with the chassis. It was the emergency brake levers/linkage that I had to deal with. This required me to remake the brake cable mounting and engineer some new solutions and swap some internal parts between the left and right calipers. This would have been easier had I just swapped the entire upright assy's left to right, putting the brakes behind the axles. Not an issue at all if you just don't use the emergency brake at all.

From pics that I have seen on the 'net, the FD uprights might be a bit easier for the toe link connection. However you would have to dial out any bump steer issues, requiring more work at the chassis end. Those issues are non-existent using the FC upright.


Attachments:
FC rear upright.JPG
FC rear upright.JPG [ 141.3 KiB | Viewed 532 times ]

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