Smaller Trailer Wheels

[CPO77]

Hi All, Im looking to reduce the running height of the trailer for our 7.5m RIB, it’s currently sitting on a bunked SBS3500 that Ive converted with roller carriages.
Like a few others on the forum, its a bit of a pig to get off the trailer esp on shallow angle ramps where the boat isn’t completely floating. My last trailer was a Gyro Vanclaes and the boat rolled off that in 12” of water if you gave it as much as sidewards glance

Ive adjusted the trailer so the hull is sitting as far back as possible and as low as possible until the sterns just touching the keel rollers while keeping the bow higher. Because of the boat weight, I dont want to start messing about with ropes or extending hitches on the ramp.

Im considering experimenting with smaller wheels moving from a 13” rim and higher profile tyre to a 195/55 R10 - same 750kg load / speed rating. This would reduce the running height by just over 2.5”.

Other than slightly increased rolling resistance and premature bearing wear, what are the disadvantages of dropping wheel size? Ive no issues with ground clearance - my only real concern is the reduced cushioning of a slightly lower profile tyre.
Keen to get anyone’s thoughts and feedback!

[Pikey Dave]

Check that the actual wheels are load rated too.
I can’t help but think that this is a fudge for a trailer setup issue. It may bring its own set of problems. Will the 10” wheels fit the braked hubs? The wheels will rotate faster & heat build up on the tyres & bearings could be an issue.

[CPO77]

Originally Posted by Pikey Dave

Check that the actual wheels are load rated too.
I can’t help but think that this is a fudge for a trailer setup issue. It may bring its own set of problems. Will the 10” wheels fit the braked hubs? The wheels will rotate faster & heat build up on the tyres & bearings could be an issue.

Tks PD, Ive tinkered with the roller alignment so they are perpendicular to the spray rails, I could raise them further at the front but that’s counter productive to my issue? The hulls sitting on the rollers at the transom. On this trailer (as it’s a converted bunk) the cross members are straight to support the rollers which is a factor. On most native roller trailers the X-member is V shaped which would allow the boat to sit a tad lower.

The wheels are similar to Ifor Williams wheels and are suppled with tyres - they are used on 3T plant trailers so should be fine? It rains so much in Ireland the roads are naturally ‘cooling’ anyway

[Orwell boy]

Originally Posted by CPO77

Hi All, Im looking to reduce the running height of the trailer for our 7.5m RIB, it’s currently sitting on a bunked SBS3500 that Ive converted with roller carriages.
Like a few others on the forum, its a bit of a pig to get off the trailer esp on shallow angle ramps where the boat isn’t completely floating. My last trailer was a Gyro Vanclaes and the boat rolled off that in 12” of water if you gave it as much as sidewards glance

Ive adjusted the trailer so the hull is sitting as far back as possible and as low as possible until the sterns just touching the keel rollers while keeping the bow higher. Because of the boat weight, I dont want to start messing about with ropes or extending hitches on the ramp.

Im considering experimenting with smaller wheels moving from a 13” rim and higher profile tyre to a 195/55 R10 - same 750kg load / speed rating. This would reduce the running height by just over 2.5”.

Other than slightly increased rolling resistance and premature bearing wear, what are the disadvantages of dropping wheel size? Ive no issues with ground clearance - my only real concern is the reduced cushioning of a slightly lower profile tyre.
Keen to get anyone’s thoughts and feedback!

I have trodden this same path ,however i think you will do far better with 12" wheels as they may well have the stud pattern you prefer ,i bought 4x st500 12 wheels and tyres on 5x112 ,they are what the trailer manufacturers use on the 3.5 ton trailers (load rated to 900kg 102n ) my trailer is 1800kg on single axle . Overall diameter finishes at 52cm
Despite buying them i never fitted them ,i launch from a steep slip most of the time ,however when i have used shallow slipways i now find i can overcome by raising the suspension on my discovery 5,for my scottish adventure next week i have fitted a low roller on the front x,member so i can run the winch strap through the roller and back to the boat to winch the boat off

[CPO77]

Thanks - what’s the tyre profile on the 12” rims? 156/60 R12? The rims I’m looking at are in the correct PCD, I’m more concerned with the reduced tyre sidewall on 195/55’s translating to a much harsher ride…. I dont have any experience of running lower profiles on a trailer so not sure what to expect!

[beamishken]

Originally Posted by CPO77

Thanks - what’s the tyre profile on the 12” rims? 156/60 R12? The rims I’m looking at are in the correct PCD, I’m more concerned with the reduced tyre sidewall on 195/55’s translating to a much harsher ride…. I dont have any experience of running lower profiles on a trailer so not sure what to expect!

I run a 3500kg goods trailer on 195 50 13's so probably a similar sidewall profile to what you intend. These are inflated to 95psi so little to no give in them so ride in the tow vehicle does tend to be harsh unless roads are smooth, local Scottish roads tend to shake your teeth out. The tyres wear very quickly too, probably due to so little sidewall meaning the tyres scrub round corners rather than the sidewall deforming slightly.
I find if a particular boat is a bit reluctant to depart the trailer then backing down a little faster then a quick dab on the brakes at the appropriate moment usually encourages it into the water.