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I’m looking to build a mid engined race car for racing in the Sports car class in New Zealand.
Every one locally I have spoken to has said that light weight al uprights are needed.
Car would weigh about 550kg and run 200-220mm wide front slicks.


I have been looking at a few options.
1) design my own
2) get something off the shelf. Like http://www.ekmpowershop9.com/ekmps/shop ... -350-p.asp
3) Modify something like a Midget or sprint car upright. By adding some kingpin extensions.


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I have read a few different posts on the site but would like some advice on what some other people would do.

I ended up designing my own upright and hub..

I based the design on a ford fiesta hub and bearing... however, If I had to do it all over again, I might use something else.. In other words if you have some downforce and large slicks, you might opt for larger bearings..

The main question is the price you are trying to design to.. With lowering prices for CNC machining, and some care in the design, to have less trouble when machining, you might just as well design your own..

I would run Toyota Hi-Ace/Hi-Lux uprights, lighter than you think, can make your own steering arm to suit and darn decent size brakes on them as well as common PCD 5 stud.

You can always go to something trickier and more expensive later if you're looking competitive enough to justify it, otherwise go and have fun.

To answer your choices, the Midget/Sprintcar uprights is a very viable choice and I'm amazed more builders don't visit Speedway shops for components.

I think the traditional Spitfire uprights are a good choice for you. They are several pounds lighter then other stock type units. They are very common on older formula cars so I think many designers went down this road. The kingpin upright you gave a picture of makes me wish us homebuilders and road racers could generate enough market for our own parts. It's only something like half the height of a Spitfire or normal modern front upright. When you add the parts to adapt it you will lose any advantage and it will weigh what other units would.

I couldn't find the other part you pictured, what is that for? Does it adapt that upright you pictured?

The upright you pictured is used on dirt track oval cars, I'm not sure it's used on pavement cars? So that snout is used on "Wide 5" hubs which I think are also only used in dirt cars. I've been meaning to talk to people that know about oval track cars to confirm this. Does anyone know? There are many fabricated uprights to mount this stuff - although many of these are different heights on the left and right side. You can buy little steel inserts for the ball joint and snout mount to weld up your own.

This brings up a question I have had for a long time and that is: is the wide 5 as used by the circle track guys the same as that used by early VWs ie 5 studs at 205mm dia ? if they are the same there is a ton of VW custom and standard stuff out there.

Sorry, I don't know the bolt circle diameter, but dirt track 'wide five' hubs use the bolt circle diameter from a late 1930s (American) Ford. Safe to say that if it's metric it's purely accidental!

I doubt they are a common thing in NZ. Personally I would stay away from anything that is so old now when better new and common stuff is available.

explode64, look at Pook's build's using Solstice aluminium uprights, they may be what you could use too and you can adapt bigger Corvette brakes to them as well if required (I put a link to that conversion in one of Pook's threads).

with regard to the wide five pcd, we in england used to fit vw wheels to the E93a ford anglia to get more rubber so i think they are the same, or close enough.

if wide five are 8.0" and vw are 205mm then all we have is a 1.8 mm discrepancy, now if the stud dia is smaller on the wide five than the vw, they will go on, (this is just over a 1/16" for "inch" people)

I have found some Ford Cortina Al uprights. the king pin angle is only about 4.3 deg so when hooked up to a set of formula 3 tyres and 0 offset rims will result in a 119mm scrub radius.
Is this too much?
This isn't helped by having a 140mm spindle.

Lots of scrub will give you light steering for AutoX etc. (100mm+ was quite common pre-power steering) but on faster, rougher tracks you may get a bit of kickback and unstable braking.

Why '0' offset?

wide five versus vw, no they are not the same at all.

designing your own uprights is very covenient way to go but to make it usful, you must make it somewhat universal,

1. the uprights must suit both left and right applications.
2. if they could also be used for the rear, that would be a plus.
3. the size of the brakes must leave you with a choice of rotor/ calipers for different weight cars.
4. the top and bottom ball joints, you should use some sort of insert for the tapers that is offset to allow for camber/caster changes and different ball joints.
5. the spindle should be removable to allow for different off the shelf spindles/hubs and the option to move the spindle forward or rearward, up and down like on an eccentric, it would also benifit from being able to move the spindle in and out for adjustable scrub radius
6. the steering arm location, this should have at least two locations provided in the upright, preferablly three, top middle and bottom.
7. caliper location should be provided on the upright without the use of special brackets if possible, due to the weight of brackets and fixings, and three locations, front top and rear.
8. clearence should be provided for a park brake caliper cable.

i'm shure all of this could be done if you start with a blank sheet,

anyone else like to add?

How is that, when the power for scrubbing the center of the contact patch about the steering axis comes from the driver.

I can see how in some conditions the momentum of the car could aid in turning in the desired direction, but as you alluded to, seems dicey under other conditions.

This was more common before almost all cars had power steering. If you have a lot of scrub radius, the tire rolls forward and backward when you move the steering wheel and you are still or going very slowly. It doesn't work if your foot is on the brake. Some of the scrub is replaced by rolling.

I was trying to figure the geometry on some Pinto uprights and they had nearly 3" of scrub radius. That would put almost the entire tire outside of the steering axis. They didn't have power steering.

Got a pen or pencil in front of you?

Hold the pen at both ends with your thumbs and forefingers and press down hard on your desk pushing one end back and forth with your left thumb and finger pivoting around your right thumb and finger.

Now do the same but move your right thumb and finger to the center of the pen/pencil (remains as the pivot).

If you can feel the difference between 100mm and zero scrub pushing down on a pen/pencil, imagine 1000 pounds pushing down on 2 grippy tyres.

Ah, got it, thanks.

cheapracer, not sure I understand your example; does it basically go along with what Marcus said?