Ted Lathrop Explains the Fast Cars Front Suspension for MGB
British V8 2006 Tech Session: MGB Front Suspension Upgrade
as published in British V8 Newsletter, Volume XIV Issue 2, August 2006presented by: Ted Lathrop of Fast Cars Inc.
coverage by: Curtis Jacobson
Ted Lathrop began his tech session by warmly endorsing the theme presented by Bill Guzman in the preceding tech session: "Keep it simple!" Ted further expressed two common feelings among our community: British sports cars were built to be fun and they were built to be driven. Modifications we make to them should be completed with those goals firmly in mind.
The Fast Cars Inc. independent front suspension ("IFS") could be perceived as a very simple and straightforward way to dramatically upgrade an MGB's handling to a higher, more modern standard. After all, the IFS comes as one complete unit and installs with just four bolts. Installing it seems so much easier than rebuilding a worn stock suspension! But of course, the paradox is that engineering a front suspension is serious work. The purpose of Ted's tech session was to walk us through his design process and to explain the theory of operation behind his resulting design so that we might appreciate its potential benefits.
Please support the sponsoring companies who make BritishV8 possible, including:
There's no better visual aid than actual parts. Throughout the tech session we were able
to examine the front suspension that will soon be installed under Rob Ficalora's
Ford-powered MGB.
According to Ted, the first priority of his design was to reduce un-sprung weight. ("Un-sprung weight" is the weight of all components from the suspension springs down and outboard to where the tires contact the road.) Whereas any weight reduction will make a car quicker, reduction of un-sprung weight particularly improves ride quality. Ted didn't digress into a component-by-component weight comparison with the stock suspension, but he did claim a dramatic savings of eighty pounds in total!
Another design priority was accommodation of bigger, stronger brakes. The Fast Cars
IFS comes with 11.75" Wilwood vented rotors and robust four-pot Wilwood "Dynalite"
aluminum brake calipers. (Fast Cars also offers an 8" Ford-based rear axle assembly
for MGB that utilizes Wilwood disc brakes.) The size of these brake components obliges
users of the Fast Cars IFS to fit 15" wheels (or larger) in lieu of MGB's original
14" wheels. Ted prefers fifteen inch tires anyway because they tend to iron-out the
road surface in terms of perceived ride quality. The relatively high volume of the
four piston calipers requires installation of a residual pressure valve in the brake
system, but that installation is relatively cheap and easy.
A third design priority was to further improve ride-quality and handling by better placement of the lower spring mounting point. The Fast Cars IFS incorporates coil-over shock absorbers, and the coil-over shocks are mounted quite far out at the lower end, so that the spring compresses relatively far for a given wheel displacement, which in practical application means that 200 pound per inch springs can be used instead of (the stock) 400 pound per inch springs. This geometry also increases travel of the shock absorber's piston for any given bump, which is advantageous.
Of course, coil-over shock absorbers have inherent advantages of their own. For one, they facilitate very simple ride height adjustment, and even potentially the tuning of "corner weights" so that the weight of the car is better balanced over the tires while driving. Fast Cars utilizes lightweight Carrera aluminum-bodied shock absorbers. Shock valving has been selected specifically for this application, so there's no need for the valves to be driver-adjustable.
The original MGB suspension was designed for bias ply tires. (Remember those?) It had about seven degrees of caster angle, which means that with modern radial tires steering effort is relatively quite high. (Caster angle is the relative angle of the kingpin or "steering pivot axis" to a vertical line as viewed from the side of the car. Seven degrees was a lot, even by 1960's standards. The only good, practical way to reduce a stock MGB's caster angle is to fit wedge-shaped shims between the front suspension assembly and the rest of the chassis.) The Fast Cars IFS has a nominal caster angle of three degrees, and like modern cars the caster can be easily fine-tuned during alignment. The adjustment range is 2.5 to 5.0 degrees. One characteristic of the Fast Cars IFS is very light, precise steering.
According to Ted, the first priority of his design was to reduce un-sprung weight. ("Un-sprung weight" is the weight of all components from the suspension springs down and outboard to where the tires contact the road.) Whereas any weight reduction will make a car quicker, reduction of un-sprung weight particularly improves ride quality. Ted didn't digress into a component-by-component weight comparison with the stock suspension, but he did claim a dramatic savings of eighty pounds in total!
 |
 |
|
| Lightweight components and fabricated 4130N spindles | Nylatron GS bushes and lots of Zerk grease nipples! |
A third design priority was to further improve ride-quality and handling by better placement of the lower spring mounting point. The Fast Cars IFS incorporates coil-over shock absorbers, and the coil-over shocks are mounted quite far out at the lower end, so that the spring compresses relatively far for a given wheel displacement, which in practical application means that 200 pound per inch springs can be used instead of (the stock) 400 pound per inch springs. This geometry also increases travel of the shock absorber's piston for any given bump, which is advantageous.
Of course, coil-over shock absorbers have inherent advantages of their own. For one, they facilitate very simple ride height adjustment, and even potentially the tuning of "corner weights" so that the weight of the car is better balanced over the tires while driving. Fast Cars utilizes lightweight Carrera aluminum-bodied shock absorbers. Shock valving has been selected specifically for this application, so there's no need for the valves to be driver-adjustable.
The original MGB suspension was designed for bias ply tires. (Remember those?) It had about seven degrees of caster angle, which means that with modern radial tires steering effort is relatively quite high. (Caster angle is the relative angle of the kingpin or "steering pivot axis" to a vertical line as viewed from the side of the car. Seven degrees was a lot, even by 1960's standards. The only good, practical way to reduce a stock MGB's caster angle is to fit wedge-shaped shims between the front suspension assembly and the rest of the chassis.) The Fast Cars IFS has a nominal caster angle of three degrees, and like modern cars the caster can be easily fine-tuned during alignment. The adjustment range is 2.5 to 5.0 degrees. One characteristic of the Fast Cars IFS is very light, precise steering.
There are two other basic alignment specs: camber and toe-in. The Fast Cars IFS
is designed to have very little static camber... somewhat less than the MGB stock
suspension's nominal one degree spec. (Camber is the relative angle of the steering
pivot axis to a vertical line as viewed from the front or rear of the car, and of
course it changes with body roll as a function of suspension geometry. When a
suspension is designed to work well with lower static camber, it typically will
also benefit in better tire life and straight-line braking.) Ted recommends very
little toe-in on radial-tire equipped MGB cars: just one thirty-secondth to one
sixteenth of an inch.
As briefly alluded to above, the relative location of suspension pivot points defines the characteristic way tire/wheel camber changes in roll for that suspension. That's very important, but the pivot point locations do more than just that. For example, by virtue of the relative placement of A-arm attachment points, the Fast Cars front suspension has some "anti-dive" built in. "Dive" is the tendency for the front end of a car to go down when brakes are applied. Stock MGB suspensions dive quite noticeably, as do all other cars of their era. In more modern cars it's typical to arrange the suspension geometry so that the upward force of brake torque reaction opposes the downward force of load transfer, at least to some significant extent (like maybe 25 percent). This characteristic has become common in modern cars because it makes the cars a little more pleasant to drive. (The Ford "Mustang II" front suspension introduced anti-dive to hot-rodders, and anti-dive has been a popular feature on hot-rods ever since.)
Another interesting characteristic of the Fast Cars front suspension geometry, as Ted explained it, is that the "roll center" for the front suspension is significantly higher than for the stock MGB front suspension. I don't know if I can explain properly, but I'll try. The front and rear suspensions on a car have two different roll center heights. The rear suspension of a leaf-spring rear-suspension car, such as an MGB, has its roll center location at axle height (unless extra links such as a Panhard rod have been fitted). If you draw an imaginary line from front suspension roll center to rear suspension roll center, that line defines a "roll axis" for the car. The roll axis of a car is the imaginary axis around which the body (or rather the "sprung mass") of the car pivots as the vehicle corners. Ted explained that he deliberately placed the front roll center substantially higher than stock to level the roll axis.
The Fast Cars front suspension accepts the same anti-sway bars as the stock MGB suspension.
The rack-and-pinion steering gear that Fast Cars uses is custom-made for their IFS.
It requires an intermediate shaft and u-joints to connect to the MGB steering column.
Customers may fabricate their own, or buy a custom-made intermediate shaft from Fast Cars.
New this year! Ted announced that he is now offering the IFS with motor mounts pre-installed for easy installation of Ford 5.0 engines. He is also offering the IFS in a second, two-inch wider track width for customers who are fitting fender flares. Finally, the IFS may be ordered pre-painted to match the car. (Rob's suspension demonstrated the Ford motor mounts and custom paint options.) Do you have any other special requests? Fast Cars would like to work with you.
Other new products that Fast Cars Inc. is now offering include a cross-flow aluminum radiator for MGB and nifty stainless steel block-hugger headers for Ford 5.0 V8 conversions. (The left-hand and right-hand headers are slightly different to provide extra clearance to the motor mounts.)
Ted also announced that a three-link rear suspension for MGB is in development.
As briefly alluded to above, the relative location of suspension pivot points defines the characteristic way tire/wheel camber changes in roll for that suspension. That's very important, but the pivot point locations do more than just that. For example, by virtue of the relative placement of A-arm attachment points, the Fast Cars front suspension has some "anti-dive" built in. "Dive" is the tendency for the front end of a car to go down when brakes are applied. Stock MGB suspensions dive quite noticeably, as do all other cars of their era. In more modern cars it's typical to arrange the suspension geometry so that the upward force of brake torque reaction opposes the downward force of load transfer, at least to some significant extent (like maybe 25 percent). This characteristic has become common in modern cars because it makes the cars a little more pleasant to drive. (The Ford "Mustang II" front suspension introduced anti-dive to hot-rodders, and anti-dive has been a popular feature on hot-rods ever since.)
Another interesting characteristic of the Fast Cars front suspension geometry, as Ted explained it, is that the "roll center" for the front suspension is significantly higher than for the stock MGB front suspension. I don't know if I can explain properly, but I'll try. The front and rear suspensions on a car have two different roll center heights. The rear suspension of a leaf-spring rear-suspension car, such as an MGB, has its roll center location at axle height (unless extra links such as a Panhard rod have been fitted). If you draw an imaginary line from front suspension roll center to rear suspension roll center, that line defines a "roll axis" for the car. The roll axis of a car is the imaginary axis around which the body (or rather the "sprung mass") of the car pivots as the vehicle corners. Ted explained that he deliberately placed the front roll center substantially higher than stock to level the roll axis.
The Fast Cars front suspension accepts the same anti-sway bars as the stock MGB suspension.
 |
 |
|
| Optional pre-installed motor mounts for 302 Ford | Specify any wheel-stud spacing you desire |
New this year! Ted announced that he is now offering the IFS with motor mounts pre-installed for easy installation of Ford 5.0 engines. He is also offering the IFS in a second, two-inch wider track width for customers who are fitting fender flares. Finally, the IFS may be ordered pre-painted to match the car. (Rob's suspension demonstrated the Ford motor mounts and custom paint options.) Do you have any other special requests? Fast Cars would like to work with you.
|
Enjoying this article? Our magazine is funded through the generous support of readers like you! To contribute to our operating budget, please click here and follow the instructions. (Suggested contribution is twenty bucks per year. Feel free to give more!) |
Other new products that Fast Cars Inc. is now offering include a cross-flow aluminum radiator for MGB and nifty stainless steel block-hugger headers for Ford 5.0 V8 conversions. (The left-hand and right-hand headers are slightly different to provide extra clearance to the motor mounts.)
Ted also announced that a three-link rear suspension for MGB is in development.
For anyone interested to see the Fast Cars IFS installed, the meet provided ample opportunity
for that too. Steve Carrick, Robert Milner, Pete Mantell, and Mikel Moor have all fitted
the suspension and this author managed to test drive three out of their four MGBs by the
end of the meet. This suspension really works! In this author's opinion, lighter
steering effort is the single most obvious difference from stock (at least when you're driving
someone else's car gently.) That's the first characteristic I noted in all four cars.
I drove the cars too gently to honestly evaluate other characteristics as I would have liked to
- and I'm not the keenest test-driver anyway...
But Mikel Moor has had the Fast Cars IFS installed now for over two years, and his comments were typical of what I heard: "I'm still totally excited over it! There's no bump steer, and (highway) expansion joints seem to have just melted away. At the Putnam Park race track I was able to just drive my line without fuss - FAST! - and without tire squeel. At lower speeds I really notice that the Ackerman angles seem to be worked-out better. The tires don't seem to be scrubbing at low speed and I notice that I've got more wheel-cut too."
I wish I'd had a pen with me when Robert Milner came down off "The Tail of the Dragon" - he was so pleased with his recently installed Fast Cars IFS that he was chattering and bouncing up and down like a kid!
Disclaimer: This page was researched and written by Curtis Jacobson. Views expressed are those of the author, and are provided without warrantee or guarantee. Apply at your own risk.
Photos by Curtis Jacobson. All rights reserved.
But Mikel Moor has had the Fast Cars IFS installed now for over two years, and his comments were typical of what I heard: "I'm still totally excited over it! There's no bump steer, and (highway) expansion joints seem to have just melted away. At the Putnam Park race track I was able to just drive my line without fuss - FAST! - and without tire squeel. At lower speeds I really notice that the Ackerman angles seem to be worked-out better. The tires don't seem to be scrubbing at low speed and I notice that I've got more wheel-cut too."
I wish I'd had a pen with me when Robert Milner came down off "The Tail of the Dragon" - he was so pleased with his recently installed Fast Cars IFS that he was chattering and bouncing up and down like a kid!
Disclaimer: This page was researched and written by Curtis Jacobson. Views expressed are those of the author, and are provided without warrantee or guarantee. Apply at your own risk.
Photos by Curtis Jacobson. All rights reserved.
