spindle ?

[deebert]

I was wondering if anybody is changing there spindle inclination on there spindles. If so what is the degree you have found that works best?

[Ron Sutton]

I was wondering if anybody is changing there spindle inclination on there spindles. If so what is the degree you have found that works best?

There are variables that I take into account ... like scrub radius & if we have any caster limitations.

If the scrub radius is already high ... and I can't get it down ... I don't want to make it worse by reducing the KPI. But if the scrub radius is decent, I'll lower the KPI on new spindles ... which allows us to run less aggressive camber.

I can't suggest a specific KPI number without knowing quite a bit about the car ... like scrub radius, caster, camber and front roll angle.

[deebert]

Well I got a 71 c10 and I have been doing a lot of measuring on it. The original spindles are 6.5 degrees. I plan on running a grand national hub so I will run fabricated spindles. The company I have been talking with recommends a 10 degree but that seems a little stout. I think it needs to the other way like a 5 degree but I'm no rocket scientist.

[Ron Sutton]

Well I got a 71 c10 and I have been doing a lot of measuring on it. The original spindles are 6.5 degrees. I plan on running a grand national hub so I will run fabricated spindles. The company I have been talking with recommends a 10 degree but that seems a little stout. I think it needs to the other way like a 5 degree but I'm no rocket scientist.

I suspect you're talking to a stock car racing company about the spindle. The rules in stock cars allow for a wide track width but don't allow for long control arms. So the scrub radius in those cars is huge. That's why they run 10° KPI spindles. On ovals, you'll see a hundred different combinations of KPI from left to right, but common variations are 5° on the right & 10° on the left. On road courses, most stock cars run the same KPI on both sides ... of course. I've seen every combo here from 5° to 12°. Another thing to look at is the steering angle length & tie rod end offset for ackerman. Because most stock cars run steering boxes with center links, it is easier for them to get Ackerman. If you're planning to run a rack & pinion, you'll need to make sure you have a lot of offset in the steering arm to get anywhere near the optimum amount of ackerman.

But in road racing & autocross, where the rules allow track width & control arm length combinations that end up with low to zero scrub radius, you don't see those high KPI numbers. 3° to 5° is most common. I build my Track-Star front suspensions & Track Warrior cars with zero scrub & 5° spindles.

Also ... I don't think your spindle measurement is correct. Most GM spindles, including the C10 trucks, have 8.75° KPI. If you're going to end up with a scrub radius above 2" ... I'd stick with 8-8.75° of KPI. If you can get your scrub radius in the 1-2" window with a 7° spindle, that's what I'd suggest. I'd only go down to 5° if you can it under 1" or as close to zero scrub as you can.

You may find the Grand National Hubs & stock car fab spindles produce too much scrub radius. A quick check is to measure the center of the LBJ (lower ball joint) to the WMS (wheel mounting surface). Most of the stock car stuff is over 5". Most production cars are under 5". C6 spindles with hats are around 4.5" +/-. I offer my Track-Star brand of spindles & hubs (my design) for ProTouring, Track Cars & Road Race cars that are only 3-7/8" from LBJ to WMS. This makes it easy to acheive low to zero scrub radius, while running a much stronger spindle & hub with large bearings. My Track-Star spindles & hubs use the same massive bearings that the Grand National hubs do. But the whole package is narrower. Plus my Track-Star spindles use slotted steering arms for quick ratio changes & I offset the tie rod end outward close to the rotor for ortimum ackerman with R&P.

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[sccacuda]

...I offset the tie rod end outward close to the rotor for ortimum ackerman with R&P.

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Ron, just curious on this. What is the reason for bending the steering link? Isn't it still a straight line from the attach point on the rack to the attach point on the spindle? It shouldn't matter if it was "s" shaped, if the the ends were still at the same attaching points?

[ace_xp2]

Wow, those spindles look awesome for the price, is there any chance you can build them with a 5x4.5 wheel pattern? Are those steering arms removable? And if so, could I buy a rear steer to start and then buy a new arm from you for front steer in the future?

[Ron Sutton]

Hi Craig!


Ron, just curious on this. What is the reason for bending the steering link?
Just for inner wheel clearance when the wheel is turned hard ... over 20°. This is from a long arm, zero scrub Track-Star suspension (see photos) ... so the hubs & control arms go deep into the wheel.

Isn't it still a straight line from the attach point on the rack to the attach point on the spindle?
Yup!

It shouldn't matter if it was "s" shaped, if the the ends were still at the same attaching points?

You're correct. The curved tie rod tube is just for inner wheel clearance down at the lower part of the wheel.

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Note: Anytime you make a curved tube, it needs to be beefier than a straight tube. Where most straight tie rod tubes in racing are 7/8" OD x .083" wall thickness ... for our curved tie rods, we use 1" O.D. x .156" wall thickness DOM (1026 Steel) tubing.

[Ron Sutton]

Wow, those spindles look awesome for the price,
Thanks! They are super strong for high g-forces from road courses & cutting edge geometry.

is there any chance you can build them with a 5x4.5 wheel pattern?
Yes, we can do 5 x 4.5" for a small upcharge. 5 x 5" & 5 x4-3/4" are standard. But I suspect you're trying to keep a set of wheels ... and that probably won't work. These spindles & hubs are the strongest available on the market that don't push the wheel farther out. I do them two ways:

Full Custom: Just about ANY KPI, height, ball joint placement, hub width, steering arm length, arm offset, arm height, slotted steering arm option, etc.
Track-Star Style: Same as my Track-Star Front Ends with super narrow LBJ-to-WMS dimension of 3-7/8" for easy to achieve "zero scrub radius" (about 5/8" narrower than C6 spindles), 5° KPI, Slotted Steering Arm (4.25" to 5.25" range), Special tie rod offset for optimum ackerman with R&P, etc. But I still customize the distance of the ball joint placements for each application.

I attached a photo below of the Track-Star bearings along with common bearings. That small bearing on the right is a standard outer bearing for 60's & early 70's GM muscle cars ... A-body, F-Body & X Body ... rated at 917# thrust load. The second one from the left is a Pinto/Mustang II outer hub bearing rated at 922# thrust load. The 3rd one from the left is a outer hub bearing for GM B-Body/impala/C10 truck hubs, rated at 1130# thrust load. The large outer bearing on the far right is what I use in my Track-Star hubs. It is rated at 1800# thrust load ... and is the same bearing used in Grand National Hubs (like Deebert is going to use) on a lot of NASCAR race cars for short & intermediate sized tracks, as a well as GT1 Road Race cars, Trans Am, etc.

For that big bearing to fit in the snout of the hub, the snout needs to be 3.06" ... same as an Impala/C10 truck, same as Grand National hubs & same as Speedway Floater hubs. This snout is called the centric. The centric on most passenger car hubs is smaller. If the wheels you have were made to fit snug on the centric ... some are & some are not ... then they will be too small. Most GM cars passenger cars have a 2.75" centric ... so many wheels have centric bores of 2.77-2.79". The options are to have a machine shop open up the centric hole (providing there is plenty of material there) by .150" (.300" total).

When we're doing projects that are getting new wheels ... it's easy to order wheels with the correct centric bore size.



Are those steering arms removable?
Yes.

And if so, could I buy a rear steer to start and then buy a new arm from you for front steer in the future?

Yes. We have changed steering arms for a variety of reasons ... switching from rear steer to front ... shorter arms for quicker steering ... additional ackerman ... etc.


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[ace_xp2]

Any chance you've tried it (boring out) with say a set of c5/c6 corvette rims? Not the end of the world if I have to go more expensive, but cheap is awesome:) I was hoping to keep 4.5 purely to work with the cobra irs that's on the back of the car, plus there is a set of 17x11 size rims in that bolt pattern cheap. Going to Corvette take offs wouldn't be the end of the world though, just need to see if I can get that 4.75 to work on the cobra hubs.