Center Gravity

A busy day for the TVR planned – a suspension health check at Center Gravity followed by a trip to TVR Power for some rolling road time.

The health check is not a full setup, but a series of checks / tests to see what state a car is in and decide what to do next.

An early start up the M6 and M42 but it is an easy drive and I arrive around 08:30 for opening time.

After a coffee and a chat Chris takes the car for a test drive with me in the passenger seat. This cover a range of road types, speeds and manouevres. The bumpy B road is quite hard work, and a rear tyre rubs on the wheel arch on one bumpy bit. The car seems to ‘thrust straight’ under power and manages 27mph on the calibration roundabout before the front starts to run wide. Chris thinks that, with a refined setup, it could manage a little more. The turn-in is described as ‘rip your face off’, which I take to mean fairly aggressive.

After the drive tyre temperatures are taken (even across the tyres), pressures checked (Chris thinks the rears should go up by 2 psi) and it goes on a damper test rig which works through a range of amplitudes and frequencies. The knocking sound which we had also heard on a cobbled road turns out to be a corner of the bonnet (later fixed with a stick foam pad).

Damper test video

All the dampers seem to have a good response that is matched across the car. I am given some printouts from the computer with these plots. The test rig also measures the car’s weight as 1078 kg.

The car goes up on the ramp and the ride heights are measured off the outriggers. These are:

Front Driver’s side = 160mm    Front Passenger side = 157 mm

Rear Driver’s side  = 171 mm     Rear Passenger side  = 171 mm

Chris noted that the track rod ends were different lengths and questioned whether the rack was centred. Adjustment was 18mm passenger side and 31mm drivers side. He also noted what I had seen when the tyres were changed, the inside of the passenger side wheel has been ‘machined’, as if it has rubbed on steering lock.

Of concern was the rear damper travel when the suspension was laden. In terms of piston travel before the bump stop (which is 5cm and quite soft) there was only 15mm on the driver’s side and 20mm on the passenger side, and the piston was shiny, so that travel is being used. The front suspension had much more piston visible, and it was clear that it was not reaching the bump stop as there was a short dirty section of piston.

All bushes looked ok. It was noted that the rear drive shaft gaitors were rubbing on the anti-roll bar when the suspension compressed.

Damper settings on the Gaz Gold Pros were inspected. Chris measures settings from fully-stiff, whereas I had been setting from soft (as others seem to do). Settings were:

Front Driver’s side = 7 from full stiff (of 21)    Front Passenger side = 9 to full stiff (of 20)

Rear Driver’s side  = 10 from full stiff (of 20) Rear Passenger side  = 9 to full stiff (of 18)

Chris suggests that damper adjusters should be exercised through their range occasionally. The fronts are ok, but the rears start leaking oil from the adjuster seals when this happens. It stops after adjustment, but shouldn’t be happening.

Chris felt that the rear was bit too stiffly damped compared to the front. I had upped the rear damping slightly before going on the road trip to help avoid tyre rubbing issues. Chris backed the rear dampers off by a couple of clicks.

The wheelbase was measured as 8mm longer on the passenger side than the driver’s side. This could be due to adjustments made to cope with an off-centre steering rack.

The car was put on corner weight scales, and weighed 1124 kg with a full tank of fuel. If I rempved the fire extniguisher and bits in the glove box it would probably be 1120 kg. Not bad for an aircon-equipped car fully fuelled.

The car had a 50/50 front/back distribution when loaded with driver weight, but the cross-balance was a bit off (46.8%), and could be improved.

Rear springs rates were checked and found to be 325 lb / inch. They should be 350 and we discussed changing them to 375. That should help with running out of suspension travel. Chris was also going to check with Gaz to see if there was a short-bodied damper that could be used, although it was noted that the setup already allows the wheel to touch the wheel arch in some conditions so more compression would not be beneficial.

I left at 11:30 for TVR Power. It had been a long and busy session: we set off for the test drive at 08:50, so have got 3.5 hrs of time for the £146 cost, and it has been informative.

Chris promises to send out the report soon, and we can make a plan for getting the car how I want it.

On the ramp
More checking
Rear wheels on damper test rig, taking things out of the boot.


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