gerko Posted March 13, 2011 Report Share Posted March 13, 2011 Can anybody tell me how to test the suspension on a trailer, independent rubber bush type. My trailer seems to vibrate when driving. Not sure if the need replacing or its just how it is. (ps this is used trailer not managed to test it with my bike on but trials bikes are hardly heavy. Quote Link to comment Share on other sites More sharing options...
paul w Posted March 13, 2011 Report Share Posted March 13, 2011 If its getting on a bit and has small wheels its more likely to be a tyre that got a bit mis-shaped. On the Axles with the rubber bush check the suspension arms (the bit the wheel bolts to) the can rust and give way. (i know from experience) Quote Link to comment Share on other sites More sharing options...
gerko Posted March 13, 2011 Author Report Share Posted March 13, 2011 If its getting on a bit and has small wheels its more likely to be a tyre that got a bit mis-shaped. On the Axles with the rubber bush check the suspension arms (the bit the wheel bolts to) the can rust and give way. (i know from experience) They do look like there a few years old , Should you be able to move them by hand ? they seem solid Quote Link to comment Share on other sites More sharing options...
richt Posted March 13, 2011 Report Share Posted March 13, 2011 A few things; What trailer do have? Rubber suspension does bounce when trailer is unladen, What weight capacity are your units? for a single bike trailer you only need a 250kg pair (thats 125kg each side)so even by jumping on them they wont deflect much. You could use a suitable bar or tube to force them to see if they are free to move. They are supposed to be maintenance free but I have seen some badly rusted ones that have been seized up! Quote Link to comment Share on other sites More sharing options...
scoobydo Posted March 13, 2011 Report Share Posted March 13, 2011 (edited) Ok (from someone who used to manufacture trailers for bikes) there could be a number of reasons the trailer is vibrating. 1. Check condition of tyres and rims if appear ok lift off the floor and spin to check concentricity any wobble and the wheel is U/S and needs replacing (are the wheel nuts tight?) if ok then look elsewhere. But dont overlook the fact they wheel tyre may need balancing. Check tyre wall condition if any blisters or rips change immediatley. Trailer tyres are made as cheap as possible and can be sometimes so out of balance they can sound like a road drill ! If this is the case fit new and get balanced as a precaution. But also do this in conjunction with no 2 below. 2. Check condition of hub. with wheel off the floor check for smoothness as you turn slowly by hand - any amount of roughness and change the bearings. If they are taper bearings it is essential that there is end float - about 1mm on the hub (check with wheel removed so not to be confused by the magnification effect of the wheel). End float can appear to be like wear ( but its not). Not knowing what make of hub you have makes it hard to give precise advice here but - Make sure the hubs are smooth running and appear to be concentric in their diameter (I have seen hubs that have not been machined on their O/D and no amount of balancing will fix the vibration this causes !) If they are not turned take them off and have them licked in a centre lathe by an engineer- to a smooth diameter (dimension not critical - but onlt remove a minimum of material). 3.Trailer chassis - check for cracks or looseness - if found fix or scrap trailer if severe. (your trailer is an extension of your car and is viewed as such by the law - so its your responsibility to ensure its road traffic act compliant) 4. Suspension units - rubber cord units (indespension type) should move slightly when you jump on them (be careful though) if they have siezed then swap them. Also check condition of drop arms (from body to hub) these can corrode though and collapse - scrap both sides if in doubt of their condition & replace with new. As for weight ratings. Trailer static weight plus bike (total weight) to match as close to suspension units rating. These units run best under loading and are tested by manufaturers to 3 times plated rating. We used to use for single bike 150 kgs for trials, 250kgs for 2 bike 350kgs for 3 bike (trials bike ratings only NOT MX ENDURO or ROAD bikes) Go heavier than this and the trailer will not tow very well. I know this as I have carried out extensive testing of this - and sold finished trailers to Indespension themselves. If you have cart springs on your trailer then you are obviously a moron (and should be shot) change them for rubber chord units - as they are not suitable for a bike trailer as they have NO damping effect at all. 5. Tow hitch and ball - the most often over looked item. These do wear. (Always grease your balls chaps )Once had a customer insist of a vibration in his new trailer (and of course it was OUR fault!!!) he said he had checked everthing (yeah right yardy ya) Not happy - so came up to us (100 miles) with trailer - went for a test listen and Yup it vibrated - asked him if he had (as we has asked him to) run the trailer on another vehicle - yeah of course he had (not)So we put his trailer on our van - perfect. Now dont laugh - we measured his ball (tow ball ) and it had corroded / worn down size by 2mm on diameter. A new ball was fitted and he was a happy man. So what I am saying is dont forget to check your balls guys ! Hitches can also wear - harder to check - but if there is any amount of slackness up front you will get knocking / vibration. 6. The load on the trailer - ie your bike - This must be taut on the trailer with no movement whatsoever. If it can move - then this may cause vibration. Also the ideal situation for load distribution is to have the loaded trailer about 30-40 kgs nose (towball end) heavy. Under NO circumstances should the trailer be rear end heavy. 7. Your tow car - check the rigidity and integrity of the tow bar and the condition of the cars suspension and the balance of the cars tyres. Any / all or a combo of the above can cause towing problems. Remember no one ever maintains their trailer do they ? but expect it to carry ££££'s worth of bike at 'God I'm gunna be late type speeds' ! Give your trailer some TLC ! I hope this helps! Cheers GAW. Edited March 13, 2011 by Scoobydo Quote Link to comment Share on other sites More sharing options...
pete_scorpa3 Posted March 13, 2011 Report Share Posted March 13, 2011 Good advice! Quote Link to comment Share on other sites More sharing options...
gerko Posted March 13, 2011 Author Report Share Posted March 13, 2011 Good advice! Cheers guys , awesome advice. I will follow all the above and report back. My first ever trailer so its all a learning curve. Quote Link to comment Share on other sites More sharing options...
hrcmonty Posted March 14, 2011 Report Share Posted March 14, 2011 (edited) Blimey, didn't realise there was so much to a trailer. My Balls nice big and gresaed up, i know cause i check daily Superb write up. Cheers Edited March 14, 2011 by hrc_monty Quote Link to comment Share on other sites More sharing options...
petwar Posted March 15, 2011 Report Share Posted March 15, 2011 sorry to hijack your thread but i also need some info on a trailer. I have an old axle off a vw caddy van and was thinking of building a trailer round it. I would be using 14" wheels. I am wondering if I will need any form of suspension on it? would it be uncontrolable without it? Quote Link to comment Share on other sites More sharing options...
trialsmotopat Posted March 17, 2011 Report Share Posted March 17, 2011 a bike rack is soooooo easy in comparison to all this faffing around Quote Link to comment Share on other sites More sharing options...
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