The GTM Supercar Build Log

Archive for the ‘Suspension’ Category

Front Shocks Flipped

Thursday, December 15th, 2011

Factory Five issued an official update recently that informed GTM owners that we need to flip our front shocks from their inverted state, to running ‘body down’. I’m not sure why FFR’s manual had us install the front shocks upside-down to begin with, but it turns out that the Koni shocks provided with the kit must be installed body-down. Failing to do so can cause them to, over time, operate as if there was no oil in the shock cylinders. I think this explains why the front of the GTM is so sensitive.

After removing the shocks I had to disassemble them so I could do a ‘reset’. This involved holding the shock upside down, compressing the shock, then flipping it over and manually extending the shock. This was repeated until the shock offered resistance through the whole range of motion. The first 4-5 times doing this the shock would compress half way, then suddenly snap to the top/bottom of its range of motion. Essentially, the shock, while running inverted, was offering no dampening once it got around half-way compressed. Not good.

Now I just have to wait for spring to arrive to see how much the ride handling will be improved.

More Ride Height Adjustments

Thursday, September 29th, 2011

I recently ordered a Koni spanner wrench in hopes that I could get the rear coilovers adjusted further to increase the rear ride height.  Despite the coilovers being Konis, the spanner didn’t fit ‘as is’ so I had to modify it quite a bit to make it suitable.  With the spanner usable I was able, with the use of a lot of elbow grease and a strap wrench, to get the coils dialed up a handful of turns, raising the ride height 1/2″ further. After settling the front height is now at 4 3/8″ and the rear is at 4 5/8″.

Driving feel is much improved; it’s amazing how much of a difference 1/2″ can make. I would say the improvement with this adjustment is as great as when I adjusted the height earlier this year. Handling and stability is excellent and the car doesn’t react to the road surface nearly as much.

FFR Rear Shock Mount “Recall” Install, Ride Height Tweaks

Sunday, July 3rd, 2011

I recently got around to working on the rear suspension a bit – this included tweaking the ride height further, and installing FFR’s rear shock mount support braces to prevent cracking issues some had with the shock mount brackets.

Ride height is now set at 4.5″ on the drivers side, a hair under that on the pass side. I want to get both sides to 4.75 or 5″, but the pass side coilover is at its max adjustment (spring needs to be compressed to get more turns out of the spring perch collar). As a result I will probably be upgrading the rear springs to 800# springs to get a few more turns out of the pass side. The same coilover ‘height’ with the stiffer springs should allow the rear to sit a bit higher…we’ll see.

The FFR shock mount brace is a straightforward install. Unbolt the shock, unbolt the rear shock mount bolt, slip on the brace, rebolt it up.

Shock Mount Support Brackets Received

Thursday, October 7th, 2010

For quite a while there has been concern in the GTM community over the rear shock mounts, as there have been a handful of incidents where the mounts have started to crack, both under racing and street conditions. FFR has been pretty quiet about this issue, but today I received shock mount support brackets from them in the mail. I would assume that all other customers will be receiving these as well, as I never contacted FFR about the shock mount issue, etc. Here are some pics. The brackets are designed to slip over the top of the shock mount and lend some support.

Coilovers, tie-rods, heat wrap

Friday, December 5th, 2008

I finally got the backordered front coilover mounts in the mail so tonight I installed the front coilovers.  Afterwards the rear tie-rods were installed, but still need to be torqued to spec, as I am lacking a very large wrench to hold the tie-rod end in place to torque the frame bolt down. I also wrapped the hard-line coolant tubes with Thermo-Tec heat wrap, available from Summit.

Rear suspension installed, Fuel cover panels riveted

Friday, November 28th, 2008

After getting the steering setup the rear suspension was installed. This was a real bear, as the brackets on the frame are very tight. After much pounding, swearing, and prying, the arms went in and were bolted. Th e-brake cables were then connected to the main e-brake bracket.

The fuel tank aluminum panels were also riveted into place as well.

Front Steering Rods Cut, Spindle bearings installed

Friday, November 28th, 2008

As I mentioned previously, the steering rods needed to be cut so that the spindle bearings could be lined up properly with the front suspension knuckles. An inch was trimmed off each side (little more on the driver side) to get them to line up decently – I might have to trim off more later for a better alignment, as the rods do not have much adjustment right now. With the rods cut the tie rod sleeves were reinstalled and the spindle bearings with the bump steer washers were installed into the knuckles.

After that, I mounted the brake line brackets that go on the rear upper control arms of the front suspension. I did not do this yesterday because I simply could not find the brackets.

Lots of Rivets + Front Suspension

Thursday, November 27th, 2008

Pretty productive day today on the car. The black rivets came today so I was able to get things rolling. First, I have to complain about the rivets. They are GM specialty rivets I picked up from They look nice, but the paint chips off very easily – at least the paint on the first box of rivets did. I will probably go over the first rivets I used later with black touchup paint and make them look a little cleaner. The 2nd and 3rd boxes looked alot better, though.

Anyways, before riveting any panels to the frame you need to put down some silicone sealant – incredibly messy stuff, and it gets over everything. Don’t sweat it though, because once it dries you can just ‘rub’ it off easily. Today I set and riveted the front and rear splash guards, front and rear inner wheel wells, lower radiator tray, and finished up the footboxes. Everything is extremely solid. I used a 2″ spacing anywhere I am riveting to the frame, and 1.5″ when riveting to another aluminum panel.

Once the panels were set I mounted the front suspension – it is useful to have two people for this. My coilover mounts for the lower arms are on backorder, so mounting the coils will have to wait for now. The steering rods that connect to the front suspension are about 3/4″ too long so those will have to be trimmed. This is typical and mostly everyone has to do this.  The suspension install is pretty simple and straight forward – just make sure the lower arm cam bolt washers stay in their ‘grooves’ on the frame so you can torque the bolt down to its tighest fit. You can do the footboxes before doing the suspension too, even though the manual has you do the suspension first – you can still get a wrench in there to hold the bolt to torque it to spec.

Next up is the rear suspension, riveting the engine panels, and radiator install.

E-Brake and Coil-over mounts Installed

Friday, November 21st, 2008

The e-brake is now installed, and it required no rivnuts. I also fitted the coil-over mounts to the rear suspension arms.

Body Removed, More Aluminum Prep, Steering, and Coil-overs

Monday, November 17th, 2008

Today we removed the body, drilled out all of the aluminum panels, installed the steering rack, and assembled the front coil-overs. The steering rack went together quickly and was an easy install. I wanted to do the entire steering shaft install tonight, but it seemed impossible to get the flange bearing down the steering arm. Sounds like a job for the Dremel tomorrow. The rear springs are on backorder so rear coil-over assembly will have to wait. These Koni coil-overs look pretty nice.