Fetch Carry Posted August 7, 2007 Share Posted August 7, 2007 1996 Hymer B534 on Fiat Ducato 2.5TD This is a strange intermittent wobble that I am experiencing, let me explain. I get a wobble through the steering wheel as though the wheels are being forced left and right, and also a slight rubbing sound, the first time it happened I thought I had a flat tyre, but it wasn't and as I had been travelling along the Dorset coast up and down the hills I then assumed it was the brakes getting hot and sticking. Now last weekend I was going up a long steep hill towards the M62 from Sowerby Bridge and it started doing it near the top of the hill, not touching the brakes? I can go a thousand miles or so without this happening, and then it will do it again, and sometimes it just gives a little wobble and the stops. Any ideas? Link to comment Share on other sites More sharing options...
johnsandywhite Posted August 7, 2007 Share Posted August 7, 2007 8-) I think you may need to check that the Tyres do NOT have any bulges in the side walls (inside). Or it could be uneven wear on the treads. It may be speed dependant on when it happens? ;-) Link to comment Share on other sites More sharing options...
Fetch Carry Posted August 7, 2007 Author Share Posted August 7, 2007 It's had five new tyres fitted and balanced at the beginning of this year, it doesn't seem to be down to speed, it's more like certain circumstances is setting it off. Also doesn't make any differance if you brake while it happens. Last time I was holding a steady speed just under 50mph, but have also had it around 40mph. Basically thinking about it, had it happen 5 times since April, and we have done around 4,500 miles since then, so you see its very intermittent, and it feels just like having the wheels waggled. Link to comment Share on other sites More sharing options...
johnsandywhite Posted August 7, 2007 Share Posted August 7, 2007 8-) Whatever it is? It definitely needs further investigation. It could mean yours and others lives. May even be a wheel not put back on correctly. :-( Link to comment Share on other sites More sharing options...
Vernon B Posted August 7, 2007 Share Posted August 7, 2007 Hi F&C This sounds like "torque steer" to me. It's something that can occur with front wheel drive vehicles when a combination of the incline, road surface, rear end loads and grip are such that normal traction is lost. Under extreme conditions of gradient, front to rear, and side to side loading the normally balanced forces from each wheel become unstable possibly setting up oscillations. In some extreme instances it feels, and sounds, as if the front wheels are coming off. One of MMM experts gave a good account of this in the mag about 2 years ago and I feel sure you'll be get more technical info as a result of this post. I've experienced this myself and found that the only remedy is to be very, very careful that you don't overload the rear end, especially if you have a 'van with a garage. Having said that it might still be worth getting your Fiat dealer to check the steering and front wheel geometry. Vernon Link to comment Share on other sites More sharing options...
johnsandywhite Posted August 7, 2007 Share Posted August 7, 2007 Vernon B - 2007-08-07 12:12 PM This sounds like "torque steer" to me. :-S You're right. I didn't consider that. I am so used to driving our rear wheel RV as opposed to our front wheel drive Dethleffs. It does occur as you say. :-S Link to comment Share on other sites More sharing options...
Fetch Carry Posted August 7, 2007 Author Share Posted August 7, 2007 Having done some more searching I think torque steer could well be the answer here, as last time was a steep hill with a sharp turn at the top, we do have a large storage locker in the rear end as its a rear lounge van, and thinking about it all the times it has happened it has been on hills and once coming out of Todmorden where the road cambers all over the place. It starts occilating and it needs turns or slowing/speeding up to get it to stop. Link to comment Share on other sites More sharing options...
martin r c Posted August 7, 2007 Share Posted August 7, 2007 Torgue steer only happens under accelaration,as the engine power though the front wheels trys to staighten it up.commen with poweful small cars.not with diesal vans so much.I would make sure your wheels arn't loose. failing that, worn track rod ends/or other steering/suspention parts or incorrectly inflated tyres.would be something to check martin Link to comment Share on other sites More sharing options...
Fetch Carry Posted August 7, 2007 Author Share Posted August 7, 2007 Tyres have correct pressure and the wheels are torqued up correctly, suspension parts were checked 2 months ago by garage. I can't see how it can be some mechanical failure as it only appears now and then and goes away again. Last weekend we travelled from Northamptonshire upto Burnley and back and it did it on one 100 yard bit of road, that we have been up 5 times this year and not had it happen. Link to comment Share on other sites More sharing options...
martin r c Posted August 7, 2007 Share Posted August 7, 2007 Your not overloaded are you (?) Link to comment Share on other sites More sharing options...
johnsandywhite Posted August 7, 2007 Share Posted August 7, 2007 B-) This might help? Picked up from another Forum:- http://en.wikipedia.org/wiki/Torque_steering Link to comment Share on other sites More sharing options...
Dave Newell Posted August 7, 2007 Share Posted August 7, 2007 Its almost certainly torque steer which occurs when the drive shaft angles are uneven and carrying relatively high torque. When climbing a steep gradient it is not impossible for the wheels to lose grip momentarily and if this happens alternately from side to side then it can set up this oscillation you describe. The only true solution is to get more of the vehicle's weight onto the front wheels but as this is not always possible just ease off the loud pedal a bit. By the way the "MMM expert" who wrote about this about two years ago was probably me although I first wrote the reply detailing torque steer about ten years ago (possibly more) (lol) D. Link to comment Share on other sites More sharing options...
Fetch Carry Posted August 8, 2007 Author Share Posted August 8, 2007 Martin, as far as I know we are not overloaded, no bikes or the like, just got the hookup lead, four chairs and hose etc. back there in the locker, fair overhang from the rear wheels though, and of course there is all the internal stuff that is also rearwards of the wheels. Maybe try moving some of the stuff forward if we can. Dave, wouldn't mind knowing more when you have time. It just doesn't make sense that it is something mechanicaly wrong as there is no consistency to when it happens. Thinking about it more the wheels feel as though they are being pulled to the left and then back central, doesn't feel like being pulled to the right. The only consistent part is that it does seem to happen on some sort of gradient, and when using lower revs, which sort of ties in with being torque related, its just very un-nerving when it happens, makes you think there is something major wrong. Link to comment Share on other sites More sharing options...
Dave Newell Posted August 8, 2007 Share Posted August 8, 2007 Right now I've got a half hour spare. Torque steer is a phenomenon of front wheel drive and has several possible causes. It is called torque steer because the torque being transmitted by the driveshaft can cause a rotational force about the steering axis (kingpin in old terminology). With equal driveshaft angles the rotational force is equal on both sides and so no torque steer effect is created. If however the driveshaft angles are different then the rotational force will not be equal on both sides and torque steer will occur. The larger the difference between driveshaft angles the more the torque steer effect will be felt, likewise the higher the torque being transmitted at the time will create a stronger effect The first and foremost cause is unequal length driveshafts. As the vehicle moves up and down on its suspension the drive shaft angle changes, if the shafts are equal lengths then assuming the two sides go up or down by the same amount then no torque steer will occur because the drive shaft angles are the same for both shafts. On modern vehicles the drive shafts are designed to be the same length, usually by making the longer shaft a two piece unit with the inner section supported by the diff and an outer bearing. The remaining outer section of the long shaft is the same length as the shaft on the other side, in general the longer driveshaft will be on the UK offside. It will be seen that anything which makes the suspension on one side compress by more than the other will give rise to an unequal driveshaft angle and if the shafts are transmitting highish torque loadings then an unequal turning force about the steering axis will result and cause the phenomenon to occur. From the above you will note that there are two factors affecting torque steer, driveshaft angles and the amount of torque being transmitted. If, when climbing a hill for example, one wheel loses traction and starts to spin then it will be transmitting a higher torque than the wheel which is gripping, this variation in torque between the driveshafts again creates the rotational force about the steering axis and thus torque steer occurs. If the two driving wheels alternately grip and slip left to right repeatedly this can cause the torque steer effect to switch direction giving rise to the "wobble" you feel at the wheel. One other possibilty is when traction control is used. Modern systems often use the ABS braking system which monitors road wheel speed for all wheels. When a large speed difference is detected (as would happen when one wheel loses traction) the traction control system can apply the brake to the faster wheel thereby causing the diff to transmit the torque to the gripping wheel. Again when this occurs, if the grip/slip effect alternates between wheels then it can set up this "wobble" at the steering wheel. I have observed exactly this on my wife's Ford Focus and the traction control light comes on. Hope this answers more questions than it will raise. D. Link to comment Share on other sites More sharing options...
johnsandywhite Posted August 8, 2007 Share Posted August 8, 2007 8-) In other words? What it says here:- http://en.wikipedia.org/wiki/Torque_steering Link to comment Share on other sites More sharing options...
Dave Newell Posted August 8, 2007 Share Posted August 8, 2007 Yeah John, except for this bit " When the driveshafts have different length and excessive torque is applied, the longer half shaft flexes more than the shorter one, thus causing one wheel to momentarily spin more slowly than the other, resulting in a steering effect. So the equal length of the driveshafts reduce the torque steer effect. # Implement double wishbone suspension[3][4] or multi-link suspension[5]." Which is total twaddle. The longer half shaft does not flex significantly and the effect is NOT to make the wheel spin momentarily slower than the other. It fails to explain how double wishbone or multi link suspension can affect torque steer (which it can't anyway) and if you follow the link about multi link suspension it is all about rear wheel suspension which has absolutely no bearing whatsoever on torque steer. The only two variables involved with torque steer are the amount of torque being transmitted and the driveshaft angles. D. Link to comment Share on other sites More sharing options...
Guest peter Posted August 9, 2007 Share Posted August 9, 2007 martin r c - 2007-08-07 4:06 PM Torgue steer only happens under accelaration,as the engine power though the front wheels trys to staighten it up.commen with poweful small cars.not with diesal vans so much.I would make sure your wheels arn't loose. failing that, worn track rod ends/or other steering/suspention parts or incorrectly inflated tyres.would be something to check martinI agree with that 100% as I had a Renault 5 Turbo and if you wacked your foot down as you went round a corner, it just wanted to go straight on. Very disconcerting to say the least. Link to comment Share on other sites More sharing options...
davenewellhome Posted August 9, 2007 Share Posted August 9, 2007 Actually Peter torque steer usually has the opposite effect. i.e. it will turn tighter into the corner rather than try to straighten up. The effect you describe is more common in front wheel drive with a LSD. D. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted August 9, 2007 Share Posted August 9, 2007 If the problem is torque-steer then it ought to be possible to provoke it by deliberate heavy-footedness on the accelerator. Immediately lifting one's foot from the accelerator should normally cause the waywardness to stop. A common companion-symptom is that the steering 'stiffens' as the vehicle attempts to take control of the driver and my own experience with higher powered FWD cars is that any major imperfections in the road surface (ie 'tram line' grooves) can make matters considerably worse. A Corolla GTI I once owned could be pretty unpleasant under hard acceleration, but at least you always knew it would be badly behaved in such circumstances. Our present 1995 VW Golf Estate TDI is usually a paragon of road-handling virtue, except for once when I accelerated smartly (but not violently) out of a wet roundabout and the car headed violently (and very much smartly) for the shrubbery. Haven't forgotten that one as it quite scared me and earned some suitably pithy remarks from my wife. Link to comment Share on other sites More sharing options...
bob b Posted August 9, 2007 Share Posted August 9, 2007 Wheel bearing ? Link to comment Share on other sites More sharing options...
davenewellhome Posted August 12, 2007 Share Posted August 12, 2007 bob b - 2007-08-09 10:30 PM Wheel bearing ? No, torque steer and wheel spin! D. Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 12, 2007 Share Posted August 12, 2007 DaveIt couldn't be a dry (ish) outer CV joint, could it? (Or some other CV joint lubrication fault) Reading the original post, the description is of the steering wheel being pulled back and forth near the top of a long hill, accompanied by a rubbing sound. Torque steer surely tends to pull the steering back towards the "ahead" position, not pull the wheel back and forth?A poorly lubricated CV (or one where the grease has dried, or been contaminated by water) would begin to heat up and bind a bit after being asked to work continually at a larger than normal angle. As the road wheel rotates the resulting vertical forces would be resisted by the top and bottom pivots, but wouldn't the horizontal forces transmit to the steering as alternate, left - right, pulls on the steering wheel?Uphill, longish rear overhang, so more tail down and nose up on the hill, so CV joints continually working through an increased angle. More power being transmitted to mount the hill, so more work than "normal" (i.e. on the flat) running so, possibly - with poor lubrication - more friction, more heat and consequent binding. Just a thought! Link to comment Share on other sites More sharing options...
davenewellhome Posted August 13, 2007 Share Posted August 13, 2007 Not impossible Brian but my money still rests on torque steer and possibly a bit of wheel spin. D. Link to comment Share on other sites More sharing options...
Fetch Carry Posted August 13, 2007 Author Share Posted August 13, 2007 Just following on from this was back at Burnley for the weekend so was interested to see if I could re-produce this on the same bit of road, being the hill up from the bottom of Sowerby Bridge area up to junction 24 of the M62. Sure enough not far from the top where it gets steeper and then turns to the right it started to wobble, I immediately eased right off the go peddle and let the van slow a bit and it stopped wobbling, re-applied go peddle and carried on up. So sounds like this is possibly something along the lines of what Dave has suggested. Brian, you comments offer me another possibility to look at, although around that area there are quite a few long and steep hills which I go up without insident, it seems to be the right turn on this particular climb that triggers it, which I would imagine would lighten the r/h side wheel even more, and possibly triggering what is happening, I also noticed that the road is very rutted from HGV's at that point. Thanks all for the comments and help. Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 13, 2007 Share Posted August 13, 2007 davenewell@home - 2007-08-13 6:44 AM Not impossible Brian but my money still rests on torque steer and possibly a bit of wheel spin. D. Well, I hope you're right and I'm wrong Dave, because your suggestion isn't going to be expensive to remedy, whereas mine is! Link to comment Share on other sites More sharing options...
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