Hey folks, just wanted to check in to let you guys know that I'll be here on the forums quite often to post updates and let you guys know what we are doing in all things Mustang!
A bit about myself:
At Hotchkis I wear more hats that I care to count, but I test drive, instruct, prototype/R&D, Test Car building/maintenance, do the road shows and events as well as monitor several forums as a "Tech Guy".
Over the last 2 years we have been steadily evolving our early Mustang program. One of our first test cars was a 65 Coupe owned by a friend of ours. Our offerings at first were pretty modest with just a spring/shock and sway bar combo that netted HUGE gains over the stock suspension. I personally drove that car to a half dozen wins at Regional SCCA Autocross events.
Since starting our Mustang program, we've all taking a bit of a liking to the chassis and have started building two shop cars that I'll post updates on as the projects evolve. Our first one that I'll be starting on final assembly as soon as we get the drivetrain will be a "Bullit" car and will feature the latest of our product line, which includes Subframe Connectors, Upper Control Arms and Adjustable Strut Rods. We were able to collect a lot of data after racing the two test cars over the years and this latest offering will allow the user to really balance the cars performance between Road Racing, Autocross and Cruising the Boulevard.
Thanks for the replies guys. I'm at the Good Guys Show/Autocross in Scottsdale right now, so my replies may be limited until Monday.
We will have a press release about the new Control Arms, Subframe Connectors and Adjustable strutrods by the end of the month. But I can tell you know, this stuff is really nice.
To be honest its all of the above. The best part about our package is the car will maintain a very high level of cruisibility while still having enough adjustability to handle light to serious work on the Road Course and Autocross. Our shock program is on par with guys at Penske, and we use the same equipment as F-1 and NASCAR guys to tune and develop our shocks. I'll post a video about that later. To that point though, it really the shock that allows us to get way with so much.
Since Dan has not come back to give any details,
They introduced a new strut rod that looks pretty much exactly like Shaun's SoT unit and upper arms that look like the Global West +3 arms. http://image.hotrod.com/f/85315942+q80+re0+cr1+ar0/hotchkis-mustang-springs-and-sway-bars.jpg
I assume the pricing will be high also. On summit, their GM arms range from $650 to $700 bucks.
Sorry about the delayed response. I was on vacation and did have reliable access to the internet.
That said, we are continuing development on our new Uppers and adjustable strut rods. We installed them on the Mustang I posted on the top of the post and we are doing road testing right now. We'll be taking them to the track later this month for before/after testing on the skid pad/slalom and road course. I can tell you now the general feel and control are phenomenal. Before it was really good, now it's awesome. We are running 8* of Caster with 1.5* Camber. I'm waiting for our media guys to put together an official press release I can share pricing and availability. These are 100% made in the USA and use the highest quality components. They'll be on the upper end of the price market, but worth every penny.
Without writing a novel; increased caster allows the tire to remain flatter(or at a desired camber) to the road surface at increased turning angles. Less caster will result in more positive camber at larger turning angles, making the tire knife-edge. Modern tires have much stiffer sidewalls and lower scrub/slip angles leading to more control.
A really good example of the effects of not enough caster can be seen while watching cars turn into and out of parking spaces. Watch the inside tire. Performance cars will maintain a flatter tire profile and contact patch, while more pedestrian cars will knife-edge the tires really badly.
???
I'm scratching my head on this one a little. Adding too much caster increases knife edging not to mention tire scrub.
It also creates jacking/loading of the suspension in some instances.
Am I missing something? Or have I been up too long? And why isn't there a degree symbol on my keyboard? Seriously we are always using the *. Why no degree symbol?
Riley, zero caster would only keep your tires flat if you had ZERO body roll or tire deflection when cornering (which is the case in both of your pictures. The first one is static and the second one is a drift, so there is body roll in the WRONG direction!). Assuming your car has suspension and the tires aren't made of bricks, that will never be the case. You need the tires to NOT be flat (aka, negative camber) to compensate for body roll and tire deflection in a corner.
At the same time, you DO want the tires to be flat when braking in a straight line. Thats the problem with adding lots of static camber... it helps cornering but hurts braking.
That's where caster comes in! Higher caster adds negative camber only as the wheels are turned. That means for maximum cornering grip you don't have to run as much static camber as you would otherwise. So you get better cornering grip AND better braking grip.
More caster also gives better feel through the steering wheel.
The first example I posted is static as you said but still illustrates too much caster. The tires are knife edging and the suspension is being jacked/loaded just turning the wheels at rest.
I understand what you are saying. Truly I do. Fortunately for us our cars were blessed with short arm long arm in front.
If the camber gain is proper (let's assume aftermarket arms designed for such a thing ,ect) then as the car rolls, the camber gain built into arms should keep the tire flat WITHOUT excessive caster should it not?(let's assume good camber gain/roll center for the sake of discussion).
I've run as much as -2.5* static camber and 5.5* caster on a Subaru sti(strut) and my front tires were still hot on the outside after autox on a short track with my tire probe. And yes braking suffered but for that track it was faster. With a strut car it's a different beast.
I guess what I'm asking is how much caster is too much? In a strut car it is different I I feel like your points have more validity in that situation. But at some point too much caster is just too much.
I feel that number is much lower in our cars than a strut application where you are relying on the steering angle to provide some camber gain as the wheels are turned Our cars can rely on camber gain more from rolling into the corner with or without a lot of steering angle.
I'm wondering what your guys' thoughts are? I've discussed with some at the track that feel the tire scrub beyond 4-5* caster negated any benefits.
What is excess caster on our cars? 8* seems excessive to me but I in no way have the experience some of you guys do. What do you track whores think? Do you like 8*? Do I need more? What is too much caster?
And nice work on the arms, hotchkis. Very interested in your shock program. Forgive me if I jacked your thread.
Don't forget King Pin Inclination, which also keeps your tires from "staying flat". KPI adds Positive Camber to the outside tire (bad) and to the inside tire (good). Caster adds Negative Camber to the outside tire (good-offsetting KPI effects) and Positive Camber to the inside tire (good, but probably too much when added to KPI effects). That's why the inside tire of a modern car "flops over" so much at full lock: the additive effects of KPI and Caster.
Both of these also create weight jacking effects with steer angle, increasing in magnitude with scrub radius.
That's only half of the factors in suspension design, lots going on with a steering "axle" !
This is some fun stuff to talk about. The cool thing about what we all can do is we can talk about it then put it into practice and see what really works. I have found every thing in moderation. I tend to do as much as I need but not take the approach of more is better. Dan and the crew at Hotckis are some of the few that base info on performance. Hats off to them for some good parts. In the pursuit of good competition, I can't wait to meet them again on the track then trade some malty beverages afterwords soon.
Riley, IMHO you are correct. The caster you should use is dependent on the amount of camber you run. A street car (unequal arm suspension) with very little camber can get away with 8 degrees. But as static camber climbs caster should be reduced. The amounts or limits to the settings are defined by many factors. Tire type and side wall, camber curve, spindle height...etc.
"I spent a day at Ron's seminar in Ft Worth last October and I found he will not make any blanket statements on set up or suspension settings without knowing the total design of the suspension including locations of ALL the pick up points. "
I agree completly !
"Our spindles have 7 1/2-8 deg. of KPI and doubling that to 15deg can add some negative handling characteristics including a "tucking under" effect from mid steering angles to the limits,its not good.'
Yeah, I got the "double" recommendation wrong.
"Ron does like what is called "high travel,low roll" setups"
I still have trouble with this concept, I grew up thinking the lowest possible ride height/COG is of primary importance. I tend towards his "tweener" philosophy.
Stephen
The high travel set up really isn't all that new,Herb Adams was doing this way back when, it is very much soft spring BIG bar . What I learned is the "tweener" set up is more realistic for our cars ,where we have several high rate springs easily available but not any real high rate bars beyond 1 1/8" solid and 1 1/4" hollow so to address front roll we use big springs and maybe a bar on the rear. A panhard bar out back has a HUGE effect on controlling roll couple.
Ride Tech is working on some very trick shock set ups that appear to go in a completely different direction for street , autocross and trackday events. The shocks have a huge adjustment range and the autocross setup pretty much allows the front end to go on the bump stops maximizing camber gain and lowering the CG,the rears slow the rebond in dive and let the rear squat under acceleration . After a 1 minute autocross run it took about 5 seconds for the car to return to ride height , it just slowly raised.
Anyway, IF fabrication is on the menu figuring out how to mount a strait anti roll bar up front would allow some very comfortable spring rates.
Remember if you have high travel the CG lowers dynamically , static means nothing its all about what happens when the suspension moves.
I get that, but it seems to me that will only be the case during braking, and trail-braking to the apex. My background is Formula Ford, where you rarely trail-brake, and take corners on-the-gas. In that case, it doesn't seem to me like the nose will be "pinned down", resulting in a higher COG while cornering.
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