Category Archives: Suspension & Coilovers

Front/Rear suspension and coilovers


I’ve spent some time lately tweaking the coilovers in bowtie6.  Part of the fun of doing a conversion like this is debugging issues and improving the original design.  This is not because we didn’t do our homework.  Instead, once you get things running certain assumptions turn out different once exposed to the “real world” experience.  The coilovers are no exception.

Ever since I started talking about coilovers on bowtie6 both here in the blog and at car shows, I’ve been asked what coil rates I have used.  Folks ask me this expecting a straight answer but unfortunately there is no such thing!  This is a trial and error process that is highly dependent on factors such as suspension travel,  weight distribution and mounting angles of the coilovers – among others.

So when we put things on paper we factored fore and aft weight distribution and a general notion of the coilover mounting angles.  The best placement for a coilover is to mount them straight up.  At this angle the coil rating is 100%; the more tilted the less efficient the coil works.  However, it is very hard to get the coils straight up especially when you have “A” arms or the body in the way.  So this becomes a bit of a compromise.

As the suspension settled, I started noticing the front tyres scrubbing on the inside of the front fenders when doing some heavy cornering or when the car settled on a bump under heavy compression.  Not good.  So what to do?  There are several options…

Stiffer Springs

Coils come in a variety of ratings, such as 400lb coils for example.  What this means is that it takes 400lbs to compress the coil an inch.  This illustrates what I mentioned above about mounting efficiency.  The 400lb rating is with the coilover mounted straight up.  With the coilover mounted at a 20 degree angle, you would need a 454lb coil to give you the 400lb rating.

So just run stiffer springs, right?  Well, not really.  One can make the suspension too stiff and when that happens the suspension does not react quick enough to undulations in the road surface.  This can yield to poor handling.

Larger Swaybar

A larger swaybar can be used too.  However one has to be careful with this because with a stiffer swaybar the care will also react in unexpected ways under hard cornering such as oversteer or understeer depending whether a rear sway bar is used.  Careful matching is critical here.

Raising the Body

Another idea is to unbolt the body from the frame, make shims and bolt things back up.  Easy on paper but hard to carry out.  This could take a bit of time to figure out  Furthermore, a disadvantage to this approach is that the center of gravity will be affected and once again handling takes a hit.

Now What?

I am not an expert in this by a long sight, but after talking this over with several folks that know much more about this than I do, we decided on a stiffer set of coils (but not too stiff!).  I placed an order and a few days later (thanks to UPS) the stiffer coils arrived.  After opening the box and making a few measurements things got really interesting…

Turns out the coilover vendor from whom I bought the coilovers a year before, made a huge mistake.  For some reason they screwed up and sent me different length coilovers.  The rears are longer by 0.6 inches.  When my cousin Jim fabricated the frame and designed the mounting points, the calculations were based on the longer of the two pairs.  Thinking they were both the same all looked great on paper.  However, in reality the front ended up short by that 0.6 inch.

At any rate, we ended up upgrading the front coils with the new stiffer ones.  What a difference.  The tire scrub has been solved while retaining good handling.  Another “bug” solved.  Moral of the story?  just because a vender ships something you have ordered and it seems to be “correct” do yourself a favor:  measure and make sure all is correct and up to spec.  Especially on parts that might be not used for quite some time.

Coilovers on a TR6

When bowtie6 was built the first time, we used coilovers on the rear suspension.  A special bridge was made and welded to the frame to hold the top part of the coilovers and tabs were welded on the aluminium control arms to hold the lower part of the coilovers.  This was nice, the horrible “lever shocks” used on stock TR6’s were removed and all was good.

We thought about using coilovers up front but the way the original Triumph frame is constructed did not allow for a very good placement.  So instead, I used SPAX shocks with upgraded aftermarket “racing” springs.  This setup worked quite well – but with a huge shortcoming.  What shortcoming?

We all know factory Triumph TR6’s require the dreaded “spring compressor” to take the front suspension apart.  This in itself is not a big deal (provided one uses the correct type of spring compressor), however the constant tension from the spring loads up the front suspension something fierce.  This load forces the driver use great effort when turning the front wheels at parking lot speeds.  What??  Well – until you drive a TR6 with coilovers you will have to take my word for it.  With coilovers, one can turn the steering wheel with very little effort.  Huge difference.  Coilovers also allow the use of different spring rates.  One can tune the suspension to his needs very accurately.  Finally, one can control ride height very nicely with coilovers.

The downside is price.  Good quality, rebuildable coilovers are not cheap.  Sure, one can source coiloves from eBay or some half-quality supplier.  Good ones will run you about $400 a pair.  By the time you order the appropriate springs you can have $1000 a set.  But they are worth it!

The following gallery show some pics of my coilovers mounted on the new frame.  There are some pictures of the front as well as the rear suspension, with the solid axle.  One interesting note:  Take a look at the frame:  there is nothing that hangs below the frame line.

Oh and the coilovers, yes, they perform as nice as they look!

bowtie6‘s New Differential and Rear Suspension

bowtie6’s new frame gets a new differential.  In order to handle the power of the ECOTEC – remember boost is in the plans – we needed something that would not break.  Furthermore, one of my requirements for the new drivetrain is to have full posi-traction (and by this I mean the real deal and not viscous).

In the following gallery, you will see the following:

  • The rear axle is a narrowed 9″ Ford.  Yes, it might be a little overkill but again, this is all being built so we don’t have any unexpected “failures”.  The solid axle in this application will by far surpass the IRS as originally implemented.
  • The diff is a Motive full posi-traction unit.  It is set up with a 3.80 to 1 ratio – it is a bit tall in first gear with the Solstice’s AISIN gearbox but you have to remember this:  I am not building this to be a drag car.  With this ratio, the car is extremely quick and nimble at speed.  From the setup in my cousin Jim’s TR4, we have determined this rear axle ratio works fantastic with the engine in second, third and fourth gear; with fifth being even more fun at speed.
  • You can see in the pictures the special order Moser axles.  These were custom made with the correct length in order to handle the narrowed housing.
  • The rear axle is held in place as a four point suspension.  The control arms are fitted the special Heim ends.  These were quite pricey and come with special seals to keep dust and grit out.  Why Heim ends?  I’ll have an article about this later…
  • Finally, take a close look at the driver’s side axle:  the rear brake rotor is fitted.  Yes, we will be re-using the disc brakes we had previously used.
  • Not shown in the pictures is the all new, custom made brake lines.  We are using stainless tubing this time and it has all been hand made, and bent just special for this frame.  I’ll have a future article about this because the mounts that Jim made are real special.

Replacing bowtie6‘s Front Suspension Bushings

With the new custom frame finished, it is time to start putting things back together. Yesterday, the front suspension was fully disassembled and I found some interesting surprises. When I first put bowtie6 together, the front suspension was completely overhauled and of course, the a-arm bushings were replaced with what I thought to be high-quality state-of-the-art  components. Well, after 15,000 miles I have found the bushings deteriorated and they did so severely.

The bushings mounted on the lower a-arms survived fairly well. I did not take any pictures of them, since they damage there was not as dramatic as the top a-arm bushings.  Suffice to say there was a bit of slop and the bottom bolt did not fit tight.  The top bushings though, were in very bad shape.

Take a look at the images in the following gallery.  Basically these were taken before we removed the worn bushings and as you can tell, there is significant wear.  In addition to the bushings actually coming apart, there is quite a bit of deformation in the overall shape of the bushing.  Not what I have expected from these bushings, but then again such is life.

For replacements, I have sourced a different brand this time.  The new ones come from a high-performance supplier in the UK.  The new set was actually quite pricey but the design is far superior.  The bushings I replaced were of a two-piece design.  The new ones are basically one piece, but they are a bitch to put on.  It took two of us, a good vise and a bit of cursing to coerce the new bushings in place.  The new bushings are polyurethane and have a little bit more “give”.  I’m hoping this might help prevent them from breaking apart as severely as the others did.

The point of all this is for you folks thinking that these type bushings are the final solution – think again!  These things do wear out and in my case they did in only 15,000 miles.  Of course the high load that the compressed front spring puts on the front suspension is in part responsible for the wear, but nevertheless these bushings do wear out.  For you folks running V8’s (LT1, Fords or whatever) keep this in mind:  the V8’s weight is much higher than the original TR6 tractor engine or (in my case) the V6.