Roadster front suspension

[Harry]

Hello all, I know I've mentioned this before, but the front end on my Roadster has a tendency to wander left to right, I put it down to the old torsion bar suspension, I had the same problem with a 1300 Marina I had, but no cause was ever found although my 1800 Marina never did this although I know they did do so. Driving the Roadster in general is fine and braking is spot on, but if you are slowing down from 60 or more, braking or not, the car does a little - large sort of shimmy, especially on some downhill sections of road even I have alarmed myself driving this motor but my passengers colour drained faces tell that maybe I should sort this out, I cannot see a cause, the tyres are new and the air pressure is fine, the car is Polly bushed, the steering is very good and quite light all considered,, however there is some Trunnion wear but not much at all, in fact it has passed a few MOTs with this fact as an advisory ? I wondered if this little bit of trunnion wear is the cause. I would be grateful for any suggestions.

[b_caswell]

Re: Roadster front suspension

Is it possible its the diff playing up and the drive is favouring one rear wheel more than the other. Just thinking out loud.

[velovol]

Re: Roadster front suspension

Do you know what the degree of toe in or out is that you have ? Also how good are your track rod ball joints and any slack in the steering rack or loose mounting ?

[Harry]

Re: Roadster front suspension

Morning both, and thanks for replying, - I never really thought about the back end, but the diff appears to be fine and the rear suspension is in order as far as I have seen, in fact the front also appears to be in order, I have checked the steering and track rods several times and they seem fine, as I said, the only wear I can detect is a bit of trunnion wear and I will replace these before the next MOT. I have no figures for toe angle etc, but looking at the tyre edge's all seems fine. I wonder if the " Stig" would thrash it round that race track and tell me how he feels about it ?? I think I'll take yet another look at it tonight after work !

[h_m_cumming]

Re: Roadster front suspension

Check also that the rear axle is parallel to the front. If you sight along the front and read wheels so that both sides are the same and then measure the hub distance on each side they should be the same, give or take 5mm.
It's also worth checking the castor angle as most Roadsters don't have enough, which is a good reason to go for ball end tie bars so that you can adjust it. I found on mine that it made an enormous difference to the driving with less weaving under braking and better self centering.

[Gareth]

Re: Roadster front suspension

Hi Harry,
Just a thought, if you want to meet up some time, you can compare measurements with my car, and possibly solve the problem.
Gareth.

[dcunn]

Re: Roadster front suspension

Out of the blue I wonder about your rear axle location, is all tight on the U bolts ?
Presumably when you said "polybushed" you meant rear as well as front ???

Rgds DC

[Harry]

Re: Roadster front suspension

Hi Gareth, thanks for the offer, I may turn up if all else falls on it's face !

[Harry]

Re: Roadster front suspension

Hello, I should revise the Polly bushed statement to partially poly bushed ( I dived back into the garage for a look ) none used in the rear but that said, everything appears to be sound, I have a feeling that the few poly bushes used at the front end were possibly used to try and cure the very problem that I am chasing, I think I will make a start by replacing the slightly worn components in the front suspension, although not MOT failures I imagine it to be good practice to eliminate them before I go much farther ? I will however do the suggested measuring up and have a read about Camber settings etc !
Thanks.

[velovol]

Re: Roadster front suspension

Weaving under braking is a bit of a characteristic of toe in. About 2-3mm of toe out seemed right. Certainly worth trying to work in more caster angle I would think.

[ggrum]

Re: Roadster front suspension

My Roadster used to weave about a bit under braking but as soon as I replaced the radius arm rubber mounts with rose bearings (like Hugh) this weaving stopped completely. I think the problem is that as you brake the rubber mounts compress and you get a small reduction in toe-in. That's my theory anyway.

[velovol]

Re: Roadster front suspension

That sounds about right to me.

[Harry]

Re: Roadster front suspension

Hello and thanks for replying, My Roadster does the weaving act whether braking or not, as I said it's at it's weaving best on some down hill stretches especially if driven at 50 mph and over ( Same as my Marina's used to ) so I am collecting most of the Ball joint's and Trunnions from ebay over the next week or so, and I will replace everything that had been mentioned on the last two MOT'S ( They were not failures, just showing signs of slight wear ) I don't really think this will cure the problem as I have done this before, but the parts are quite cheap and I think it will be a sound start on the problem before I start tinkering with the geometry ( New area for me ! ) I was going to fit a top ball joint today by my Mondeo had a broken coil spring to attend to, and it turned into a proper dock yard job due to the rusty strut clamp bolt snapping off inside the clamp ( behind the hub ) and I had to drill it out in situ --- how a one hour job turns into a five hour job eh ?

[velovol]

Re: Roadster front suspension

Good luck with it as the weaving is very disconcerting and potentially dangerous. The Marlin to be honest when I bought it was probably the worst handling car I'd had since a Y Type Ford with beam axles and worn everything (pre M.O.T.s). A good investment would be the rose jointed tie bars.

[Harry]

Re: Roadster front suspension

Hello Velovol, Could you tell me where such bar's can be had as I cannot find any that are suitable, or do I have to have them made ?
Thanks.