Welcome to Manins' truck camper project

Wheels — Rims, Tyres, TPMS

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TT30 ran on standard rims and 9.5R17.5 (32") Michelin XZY on-road tyres for the first year to explore brake issues and steering issues without any confusion due to larger rims and tyres. At 24,500km, now both rims and tyres have been changed and the TPMS fitted.

Rims

The rims are 17" x 9" steel with six cooling holes and an offset that does not require wheel arch flares. Supplied by TravelTrucks, they come from GoannaTracks.

Tyres

The tyres of choice are Hankook Dynapro MT (RT03) 37x12.50R17 LT. These are an 8-ply Light Truck tyre with 2 ply walls, rated to 124Q (i.e. 1600 kg at 160 kph), and when new are 36.8" diameter with a tread depth of 16.7 mm.

When fitting the tyres to the rims with TPMS in place, 131gm of Checkered Flag Ceramic Compound Tyre Balance Beads were added to each. The tyre shop then proceeded to balance the tyres with external weights but this is surely an error and I have removed all the weights. I had well over a kilogram of lead in the bucket.

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5000 km later and experiencing out of balance issues resonating at 92 kph, I went back to the tyre shop. The first wheel they tested showed the out of balance in the photo. Similarly for the others except the one used as the spare, which was much better. Each wheel was out of balance by approximately 200 gm despite the presence of the balance beads. One obvious reason is the GoannaTracks steel rims, made by Dynamic, are not all that round. They have a fair bit of wobble. The other is the Hankook tyres. They are not all that well balanced either - a test of turning the tyre 180° on the rim almost doubled the out of balance!

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All wheels have now been rebalanced. Much less lead has been added than was initially. I am not sure whether that is due to tyres settling in or that the tyre shop took more care. Now they are balanced to within 10 gm. But this is not stable, probably due to balance beads taking time to move around at the low rotation speed of the balance machine. An expensive exercise and lessons learnt.

20,000 km later after driving for thousands of kilometres on dirt, gravel, mud and rocky tracks and roads, severe out of balance was felt when for the first time we exceeded 80 kph! Evidently some of the lead weights had been knocked off and the balance beads could not correct.

At 47,200 km I had the front tyres rebalanced after removal of the balance beads. They are nothing but trouble on these heavy tyres and rims. I will remove the balance beads in the rear tyres when it is convenient.


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TravelTruck had already relocated the diff. lock pump/mechanism to between the chassis rails so there is no interference problem caused by the wider Hankook spare.

The tyres weigh 38 kg each, and fitted to the TravelTrucks rims, weigh 62 kg each. This is an increase of 13 kg per wheel compared to the OEM street tyres and rims.

With the new 37” Hankook tyres the Iveco speedometer now reads 2.0% slow and the odometer now reads 8.15% too short a distance. At 46,000 km (21,500 km on the Hankook tyres) a check over 600 km showed the odometer now reads 8.1% too short a distance.

** Wheel nuts for steel rims need to be tightened to a torque of 305–375 Nm. For added safety, GoannaTracks supplied a set of Wheel Nut Indicators (27 mm) for quick visual checks.

Tyre Pressures

TravelTrucks recommend running pressures across a variety of terrain as 45psi on road, dirt tracks 35 psi, sand tracks 30 psi and extremely soft sand down to 20psi. These agree with the calculator on the GoannaTracks' Website for SuperSingles. I have made my own version of the calculator which can be used to vary loads. Click on the example here:

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Tyre Pressure Monitor

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I think the cost of a pressure monitor is well worth it. A tyre blowout on my previous camper was expensive to repair. I also found an external screw-on type very unreliable so I have gone with an Inawise TPMS-201 Tyre Pressure Monitoring System. Bought from Travel Trucks, it is the two-wheel-drive version with five sensors. The 4WD version has the ability to store on-road and off-road pressure sets but this is no advantage since I vary off-road pressures quite a lot and it is a simple matter to have the 2WD monitor accept these settings.

To change the TPMS settings, inflate/deflate the tyres to the new base pressure and press the "SET" button on the back of the display for 8 seconds until a beep is heard. The display will update during the next several minutes to the new settings.

The "user and installation guide" is available from Inawise and is here (4.56MB download) for reference.

The monitor is installed in the Daily ashtray. A hole was cut in the back of the ashtray and the cables passed through. It is connected to a distribution block "always on" point with a 1 A fuse. Power consumption is less than 20 mA.

The antennas were threaded across the dash and down the door pillars to the entry steps where the active ends were poked through a convenient hole to under the vehicle. The area was sealed with a urethane adhesive/filler.

The TPMS monitor is in the Daily ashtray.

Passenger-side antenna in the entry step.

The active end of the antenna is below the entry step.

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I fitted the sensors to the rims for the new Hankook MT tyres. Driving just a few kilometres was enough to activate the sensors so that the display showed the pressure and temperature in each tyre.

The photo shows pressures on the monitor screen. My pressure gauge says both front tyres are at the same pressure of 36.5 psi and the rear tyres are at 46.5 psi, so there is some uncertainty between TPMS sensors and between them and my pressure gauge. I will continue to set the pressures using my gauge and monitor them with the TPMS.


Tyre Rotation

Tyre rotation is done every ~10,000 km following a pattern that attempts to keep tyre wear even and uses the spare as well. We start with a tread depth of 16.7 mm at 24,500 km.

The left set is at 36,000 km (11,500 km on the tyres), and the right set is at 45,800 km (21,300 km).

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The left set is at 55,000 km (30,500 km on the tyres). Right is the latest rotation.

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The tyres have have been used (f = front, r = rear, s = spare):

  • A fsrr
  • B frsr
  • C rfff
  • D rfff
  • E srrs

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