Tag Archives: coilovers

Refining the Stance

Back to bowtie6’s birthplace for a few suspension tweaks..

First a Little History

If you look at enough TR6’s as I have through the years, you will notice very few (if any) have consistent gaps between the fenders and doors.  To help solve this problem, factory workers at the Triumph factory, added spacers between the TR6 body and the frame.  Quality back in the UK in those days was not great and on top of that, after years of use the frame would sag and the gaps had a tendency to get really bad.  Next time you go to a car show, pay close attention at any “original” TR6’s and you’ll see what I mean.

When Jim and I worked on fitting bowtie6‘s body shell on the new frame, we took a long time carefully fitting the body shell, fenders, doors, bonnet and boot lid.  I remember we actually spent HOURS doing this.  The effort was well worth:  all body gaps came out very consistent.  The downside was we had to make thicker body-to-frame spacers for the rear half of the car.  This essentially slightly “bent” the body and caused the rear half of the body shell to come up and thus exaggerate the distance between the rear tires and the rear fender.

My first set of tires on bowtie6 consisted of four Kuhmo 215/55 tires mounted on those sexy Panasport wheels.  The rears fit just fine; however the edge of the front tires rubbed the edge of the front fenders. I really didn’t any body damage so I found a pair of matching 205/55 tires for the front.  This solved the rubbing problem.

But since building a custom car is not an exact science and one must make compromises, this resulted in the car having a bit of a “rake”.  Not too bad, but when looking at bowtie6 from the side, one would notice the rear tire and fender gap was not ideal.  As a matter of fact, I remember my friend Michael reminding me the rear suspension needed some tweaking.

“Drop it down an inch”, he said.  Yeah, umm-hu.

New Tires

As noted in a previous blog article, this summer I bought a new set of tires.  This time I ditched the staggered sizing in favor of a square setup:  I bought from The Tire Rack, four 205/55 Yokohama summer-only tires.  Well, with the different tire height (remember, we went from 215/55’s to 205/55’s) the rear fender gap got really bad.

Before… (for the “after”, see the last photo at the bottom)

See what I mean?  The rear gap was not quite right.  Well, I was not about to go digging out the body/frame spacers because this would throw the body gaps all to hell.  Fortunately, Jim was able to come up with a small but effective solution to the problem.

Solution and New Stance

When Jim modified the rear axle to handle the coilovers, he made vertical mounting pads for them to bolt on to.  You can see the outline of the pads in the photo above.  Today, we took all this apart and added an extender to the pad.  This extender basically moves the axle about an inch upwards.

And the result is amazing!

Before the tweak…


After the tweak…

And there you have it!  The rake is almost gone.  Jim and I measured the end result and there is about a quarter of an inch difference between the and of the front fender and the start of the rear frame along the center of the body shell.  The gap has been reduced dramatically and overall bowtie6 has a much more refined stance.

Before…


After…


After… (see above for the “before” version)

Rear Suspension Reassembly

In the last couple of posts I’ve described the reason for taking apart the rear suspension on bowtie6.  I had to send the coilovers back to the manufacturer for servicing and sure enough, after a few days they arrived back in as-new condition.  This morning, I started cleaning all the hardware and springs followed by a dry-run:  installing the coilovers on the rear suspension (without springs) and going through the entire range of motion of the axle using my jack.  I just wanted to make sure nothing was binding or out of alignment.  All checked out, so time to quit farting around and get down to business…

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Rebuilt Coilovers

The Man in the brown truck delivered a box containing bowtie6‘s rear rebuilt coilovers.  This stuff is like jewelry – too bad they are not in plain sight!

Needless to say I unpacked them and they are perfect.  Sure, there are a few scratches from wear and tear but overall they are mechanically back to as-new condition.  The rebuild price was not too bad:  $99.00 + shipping.

I can’t wait to get the springs assembled back on them and then mounting them back to the rear axle.  I’ll have a new post with pictures this weekend.  Stay tuned!  :mrgreen:

Coilover Repair

After nearly 25,000 miles on bowtie6 and countless number of rebounds the rear coilovers finally gave up the ghost; time for coilover repair.  In order to get them apart, I had to do a partial rear suspension tear down.  My cousin Jim designed all the mounts so they could be easily disassembled – “…remember, everything will eventually be replaced or serviced at one point or another”, he says; “…it doesn’t matter how nice it looks or how great it performs, if it is not easy to disassemble and put back together, it isn’t worth a damn!”.  Wise man, my cousin Jim.

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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.