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…
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!
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.
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…
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.
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.
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.
Fall has arrived. Today’s weather was gloomy and rainy here in the Upstate of South Carolina. I decided to take a few days off from work and do some work on bowtie6. Today, after a year’s worth of work I had a chance to finally driver her home from my cousin’s shop. All I can say is the Ecotec is something else. The 3.4 V6 is so passe it is pitiful. The 2.4 Ecotec is so far superior!! This engine’s power band is amazing. The torque is amazing. I only had a chance to put a few miles on bowtie6, but I can certainly tell the difference:
- The new frame is stiff. I mean Viagra stiff. There is no flex, the car feels extremely solid. With the original frame, with no hard top… I could feel the body flex. Not so now. It is (as Bob Seger would say), “like a rock”. Amazing.
- Solid axle with PosiTraction – once you get a chance to feel what this is like, you will never go back to IRS. This thing is amazing. The “bite” is so different. There is not “squatting”. You hit the gas and there is no hesitation. It gets the job done.
- Coilovers – OMG!!! Now we have coilovers on all four corners. The rears are quite amazing, but the fronts have transformed the whole driving experience: at parking-lot-speed it almost feels like power steering. The effort to turn the wheels is almost non-existent. And… Remember, I am running 205/55-16’s up front. At speed, this thing is lightning quick. Point-and-shoot, baby!! This and the Ecotec has been the best money spent so far.
I’ll have pictures soon. I have to work on the interior, do some work under the hood and do a lot of “detailing”. There is still a lot of work to be done but in a few days I hope to have things back together soon… Stay tuned!