Wilwood ProSpindle

I know this would be much better with pictures, but I've been unable to upload any because my internet connection is too slow (satellite sucks!). They just time out.

Anyway, I've been working on redesigning my front suspension using the new Wilwood ProSpindle. I don't think I would have tried this had I realized just how invloved it would become, but I'm close to getting the car on the road, so I wanted to give a write up on how it has gone so far.

The design goal was that this had to be bolt in, no cutting and welding. Using the stock pick up point for the LCA, a Moog 772 (OEM Mopar) upper ball joint and a ride height that is lowered approx 1.75 from stock, the drop spindle results in a roll center of 7.75 inch. This is OK for normal cruising on the streets, but not ideal for a corner carver. The wheel rate using a 400 lb/in spring came out to be 205 lb/in.

In order to get the RC in the sweet spot (2 to 3") I will have to lower the pick up point for the LCA 2.5" and use adjustable upper ball joints to raise the upper ball joint pivot point about a 1/2". Lowering the LCA pickup 2.5" will require a new centerlink and possibly a new centerlink adapter to keep the bumpsteer in check. The good news is that this would virtually eliminate the moment arm acting on the rack and pinion so I shouldn't need any kind of anti-torque guide.

I'm using a prototype -10 degree steering arm right now, which required a 1/2 inch wheel spacer to clear the ('94-'04) 17x8" wheel. I'm going to try a new design with a -12 degree ackerman and just a little less length in order to clear the wheel better. The use of a wheel spacer resulted in a 3.25" scrub radius and a track width of 58.125".

An 18 inch (even an 18x9") wheel would clear no problem, but I don't like the look of an 18" wheel on the early cars. I accept the look of a 17" wheel as I feel form follows function, and a 17" wheel provides the perfect balance of weight and tire aspect ratio IMO. I might use 18" wheels at the track once I correct the roll center as I could get rid of the spacer to shorten up the scrub radius. With a P275 tire on a 9" rim I would need to use some sort of wheel stop to prevent the tire from contacting the frame in a full lock turn (not something that's required on a road course anyway) so I would only use them at the track.

The main design goal for using the drop spindle in the first place was to utilize a shorter steering arm to improve the turn radius, and a secondary goal was to fit inside a 9" wide wheel. I haven't driven the car yet with the new suspension, but judging from the angle of the wheel at full lock the turn radius will be excellent, on par with any modern car.

Wilwood also has a non-drop spindle that uses a bolt on steering arm that would be much easier to adapt to the early Mustang chassis. I will just have to give up on the 9" wide wheel.

I will post pics as soon as I can.
 
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I know this would be much better with pictures, but I've been unable to upload any because my internet connection is too slow (satellite sucks!). They just time out.

Anyway, I've been working on redesigning my front suspension using the new Wilwood ProSpindle. I don't think I would have tried this had I realized just how invloved it would become, but I'm close to getting the car on the road, so I wanted to give a write up on how it has gone so far.

The design goal was that this had to be bolt in, no cutting and welding. Using the stock pick up point for the LCA, a Moog 772 (OEM Mopar) upper ball joint and a ride height that is lowered approx 1.75 from stock, the drop spindle results in a roll center of 7.75 inch. This is OK for normal cruising on the streets, but not ideal for a corner carver. The wheel rate using a 400 lb/in spring came out to be 205 lb/in.

In order to get the RC in the sweet spot (2 to 3") I will have to lower the pick up point for the LCA 2.5" and use adjustable upper ball joints to raise the upper ball joint pivot point about a 1/2". Lowering the LCA pickup 2.5" will require a new centerlink and possibly a new centerlink adapter to keep the bumpsteer in check. The good news is that this would virtually eliminate the moment arm acting on the rack and pinion so I shouldn't need any kind of anti-torque guide.

I'm using a prototype -10 degree steering arm right now, which required a 1/2 inch wheel spacer to clear the ('94-'04) 17x8" wheel. I'm going to try a new design with a -12 degree ackerman and just a little less length in order to clear the wheel better. The use of a wheel spacer resulted in a 3.25" scrub radius and a track width of 58.125".

An 18 inch (even an 18x9") wheel would clear no problem, but I don't like the look of an 18" wheel on the early cars. I accept the look of a 17" wheel as I feel form follows function, and a 17" wheel provides the perfect balance of weight and tire aspect ratio IMO. I might use 18" wheels at the track once I correct the roll center as I could get rid of the spacer to shorten up the scrub radius. With a P275 tire on a 9" rim I would need to use some sort of wheel stop to prevent the tire from contacting the frame in a full lock turn (not something that's required on a road course anyway) so I would only use them at the track.

The main design goal for using the drop spindle in the first place was to utilize a shorter steering arm to improve the turn radius, and a secondary goal was to fit inside a 9" wide wheel. I haven't driven the car yet with the new suspension, but judging from the angle of the wheel at full lock the turn radius will be excellent, on par with any modern car.

Wilwood also has a non-drop spindle that uses a bolt on steering arm that would be much easier to adapt to the early Mustang chassis. I will just have to give up on the 9" wide wheel.

I will post pics as soon as I can.

good write up

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I was finally able to load my new suspension pics on my Cardomain site. See page 5 for the full picture layout. I'll just hit the highlights here.
23871560091_large.jpg

This is the Wilwood hub assembly mounted on the spindle. The rotor is a 12.72x1.25 directional vane, also from Wilwood. The hat was custom made to my specs.
23871560087_large.jpg

Here the tie rod end is connected to the tapered slug, which fits in the foot that bolts to the leg that bolts to the spindle that's part of the suspension that Larry built.
23871560094_large.jpg

Here you can see just how little clearance there is between the driver's side tire (P245 on a 17x8 '03-'04 Mach 1 rim) and the strut rod at full lock RH turn. This combination provides the perfect balance of tire size, offset and turn radius.
23871560097_large.jpg

I'm also working on a package using the Ford Bullitt/Cobra PBR caliper with a 12.19x1.1 rotor. This combination will fit inside most if not all 16" wheels. The Vintage wheels won't require a spacer as they have the stock offset.
 
I set the UCA level which set the ride height. Fortunately the ride height was very close to where I had it previously. I don't want it to be too low as I drive all over the country, and some roads are pretty rough. With the UCA level, the LCA came out to be at a 10 degree angle, which is still very good. If I could design my own spindle from scratch I'd only give it a 1" drop, and set the LCA angle at around 5 degrees up.

Most chassis builders start by setting the LCA level (when designing an SLA suspension), and the UCA slightly angled down (when looking in). With one arm level at rest, the RC remains very stable when the suspension goes through compression. I just inverted the standard design. By starting with the UCA at a slight angle, the camber gain is greater (sooner) than if you start with it level. I still have a much better camber gain than the stock design, and a late model strut car has none.

I could buy a fancy program that makes nice graphs, but since I can just do some basic algebra and geometry for free, I check it at the limits of what I consider real world travel and don't worry about what happens in between. My rule of thumb is 1.5" of compression and 1" of extension covers about 99% of real world driving. If you hit a speed bump going 30 mph, or a 4" pot hole going 70 mph, you'll go outside of what I consider normal. I don't bother designing for those kinds of extremes or else I'd end up with a 4wd truck suspension.

I did the math for 1.5" of compression and came up with the same 7.75 RC as it has at rest. If I had set that as my goal I would have never been able to design it to be that stable. I just got lucky. A RC at 7.75" is still only 2/3 the distance to the centerline of the wheel, so it's plenty low. The approximate CG of the car (based on the CL of the cam rather than an actual measurement) is 19". That will make the roll angle very low.

I decided not to alter anything in an attempt to lower the RC to what other's have made work. I plan to drive the wheels off the car, and I hope to take my first HPDE this year. Here's hoping that 2010 will be a better year than '09!
 
Very impressive.

I looked at the prospindles and wondered if they would work to fit a 17 x 9" rim on an early mustang without flares. Do you think that the non-drop version would also work?

I notice that you are using customer rotor hats. Was this needed to get the maximum clearance for the calipers, without using wheel spacers? I ask because I would like to fit Brembo calipers, but to do this I need to find rotors with a deep hat offset.

Peter
 
Very impressive.

I looked at the prospindles and wondered if they would work to fit a 17 x 9" rim on an early mustang without flares. Do you think that the non-drop version would also work?

I notice that you are using customer rotor hats. Was this needed to get the maximum clearance for the calipers, without using wheel spacers? I ask because I would like to fit Brembo calipers, but to do this I need to find rotors with a deep hat offset.

Peter

I'm sorry I took so long to reply, I really need to check in here more often!

When you say an "early" Mustang, I can only say that it will fit a 69-70 with rolled fender lips and a P275 tire required a little massaging of the front valance where it forms part of the wheel opening. The best fit and turn radius was with a 3/8" spacer using 94-04 late model 17x9" wheels. I'm sure it won't fit a 65-66, and it may not fit a 67-68 fender. I haven't fit check the non drop spindle, but it's possible since it's slightly shorter and it has an 11 degree IA. I plan to do that in the spring or early summer.

I used custom offset hats to simplify the caliper installation. I made simple flat caliper brackets from 1/2" steel to attach the factory type floating calipers to the Wilwood spindle. Then I had to place the rotor to fit the caliper, and since the hub was fixed, the only place to make the adjustment was the hat.
 
Had this setup out yet? What do you think of it?

Just curious, with the spacer on a 94 rim your backspacing should be about 5.5" right? How much further in could you go before you hit the spring? Any chance you could head in another inch?

One more question, you mentioned your steering being as good as any modern car. Is it better than stock, or just as good as it was even with the extra backspace?