Kevlacat 5.2 trailer problem.

[Maccas]

Hey guys,

I've got a problem with my trailer for my Kevlacat 5.2. It is a galvanized steel one made by Marlin Trailers with tandem axles with single slipper spring assembly fitted with 13inch light truck radials. The problem it gets a bit of a sway up if you go faster than 90km/hr. I have slid the axle assembly back 125 mm which made it better but still sways a little at 100km/hr:( It appears to have plenty of weight on the tow hitch but I haven't measured it.
The thing is I will be going on a long trip soon so I need to sort it out. My last boat was a Sharkcat 500 Sportsman which had the same problem but was sorted by sliding the undercarriage back and would tow at 120km/hr no problems( only did that to pass roadtrains).This trailer was similar except that it had rocker axle assembly(rides better) and had a longer drawbar. What I want to know is whether the changing to a rocker axle assemby will help reduce sway and how far back other KC 5.2 owners have the axles on their trailers. I'm thinking that a measurement from back of boat transom to the rearmost axle would be the most useful distance.

Cheers,

Maccas

[Mr__Bean]

For interest, what tow vehicle?

- Darren

[Spaniard_King]

maccas.. have you checked to see if the axles are square to the tow point???

[finding_time]

Also Maccas

Look at tyre pressure has this can have a big bearing! I had my kc get a sway up one day and all i can find that was differant was that one of the tyres was down on pressure. I always have the tyres at 60 psi now ( 8 ply light truck) and have never had the problem reappear even when passing at 120 km's.

ian

[Antony]

I have a KC 2400, it is toed with a 2003 land cruiser with BF Goodrich all terrain on and it toed beautifully 110klm no worries, about 6 or 7 weeks ago I put a new set of tyres on, I thought I would save some money and put a less expensive tyre on BIG MISTAKE, all over the road at 90klm on trip to 1770 very dangerous got back home and had BF Goodrich put back on, it toes like a dream again.

Moral of the storey, don’t conclude that it is your trailer that is causing the problem it could be your toe vehicle’s tyres , also don't take the word of tyre sale rep's

Anthony

[skipalong]

check all the pressures

[Mr__Bean]

Also, have a look at your towball height.

If your towball is too low for the trailer setup then (being slippers) it will increase the load on the front axle in the same manner that having the load too far forward does.

Having rockered springs compensates for this on a tandem and makes it less critical.

- Darren

[Maccas]

I tow it with a Mitsubishi Triton 2.8 Turbo Diesel dual cab ute normally but when I checked it after sliding the undercarriage back was a Toyota Landcruiser diesel tray back ute. I think that there is about 40psi in the trailer tyres cos if you pump them up really high the ride gets rougher for the boat but maybe I'll have to do that. Does any one know whether the single heavy spring on each axle is more likely to induce sway than multi-leaf springs. what about rocker assembly vs slipper spring assemby.

[Maccas]

Spaniard King

I have checked that the undercarriage is square with the trailer frame as each sideis equidistance from the front of the trailer frame but if the trailer frame is not square then the axles would not be square. I don't think that would be the problem as the tyres were not worn uneven when I changed them to light truck radials.


Finding Time

What sort of springs do you have on your trailer and how far back are they.

Cheers,

Maccas

[Dean1]

Maccas I had the same problem as you, mine swayed and jumped up and own on the towball. I slid the whole assembly back as you stated and has fixed the problem. Are you sure you have slid it back eough? I have alko axles. I can measure lenghts etc if it helps. Deano.

[Maccas]

Dean

I slid it back 125mm which is more than what you slid yours back as I thought that you slid yours back about 100mm ( I read your thread a while ago about your trailer problems). A measurement from the back of your boat at the bottom (not including pods) to the rearmost axle would give me a good comparison thanks . I wonder whether the fact that I have a hardtop has anything to do with making it sway.

If other KC 5.2 owners could do the same measurement it would really helpto work out the best place for the axles.

Any other ideas that might help would be good.

Thanks,

Maccas

[Noelm]

sort of easy to see if it is an axle position problem, just move the axles way back and test it! that will tell you if moving them will rectify the problem, if not, then look elsewhere, tyre pressures can cause this as well, and is probably the easiest test, involves nothing more than a trip to the Garage, or not even that if you have a compressor at home.

[Maccas]

I have decided that I will probably slide the undercarriage back some more but as I can't do it till the weekend I was hoping to get measurements from other KC 5.2 owners to save a bit of time as I will now need a longer cable for the brakes. I am also looking at changing the slipper spring set up to a rocker assembly with a conversion kit.

Cheers,

Maccas

[Dean1]

Maccas yeah i slid mine bout a 100mm, ill measure up as you asked for tommorow in the daylight and post it here bud. Cheers.

[Dean1]

From the rear of the hull(not pods) to the 'centre' of the rear wheel is 1080mm. And from the rear to the centre of the axle is 1220mm but centre of wheel is what matters. Wheel centres are 700mm. My axles are offset if you have same setup. Hope this helps.

[Maccas]

Dean,

By offset does that mean the centre of wheel is behind axle. I presume you have ALKO suspension then. Thanks heaps for the measurement. I should be able to shift it back only once more to get it right. What do you reckon about the ALKO suspension vs rocker spring assembly?

cheers ,

Maccas

[Dean1]

Dean,

By offset does that mean the centre of wheel is behind axle. I presume you have ALKO suspension then. Thanks heaps for the measurement. I should be able to shift it back only once more to get it right. What do you reckon about the ALKO suspension vs rocker spring assembly?

cheers ,

Maccas Yeah mate centre of wheel behind axle. I wasnt keen on the alko setup at 1st but its proven to be fine for me I wouldnt change it. Ive had heaps of spring trailers the alko does what they do so yeah happy with it.