Wobbly Wheels

[j.fernie]

My roadster exhibits front wheel shake at speeds of around 60 mph. A search of the forum has shown that this is not a unique problem. I have played with tyre presuures and this has improved the situation, but not cured it.
One thread in August 2006 refers to an article in that month's Pitstop about NRX suspension improvements. I inherited a number of back copies with the car, but of course not Aug/Sept 2006.
Does anyone have a copy of this article?

[h_m_cumming]

Re: Wobbly Wheels

Hi Jim, here's copies of the article, although whether it applies to your car you'll have to see. I presume you've had the wheels balanced and there's no slackness in the wheel bearings as wobble around 60/70 is usually a sign of wheels out of balance. What size wheels and tyres are fitted and are there any spacers on the hub? This can also throw the setup out and cause a wobble.

[h_m_cumming]

Re: Wobbly Wheels

Here's the copies

[KitCarGirl]

Re: Wobbly Wheels

I'm about to get my wheels balanced having swopped the front and back around. I get wheel judder between 60 and 70 and it is certainly the balancing that has caused it.

[j.fernie]

Re: Wobbly Wheels

Hugh,
Thanks for the prompt response.
It seems the old Pitstop article isn't directly applicable as my car is Marina based.
I had already considered wheel balance as the most obvious culprit, but a set of new tyres (required anyway) plus balancing made no difference.
I replaced the steering rack last w/e, because there was some vertical play at the nearside end, but to no avail.
I have reset the wheel bearings in accordance with Haynes. This has left some movement on the nearside hub, so I will try re-greasing and tightening again.
The car has what I suspect are the original Compomotive alloys with 185/70 x 13 tyres. There are alloy spacers on the front wheels, about 1/4 inch thick. How do they influence wheel vibration? Aren't they sufficiently close to the centre of rotation to have minimal adverse effect? I'll try without them anyway.

[h_m_cumming]

Re: Wobbly Wheels

Hi Jim, depending on the offset of your wheels you may foul the calipers if you take out the spacers. I have 1/4" spacers on the front and it doesn't affect the balance. As to the slight play on the N/S end of the rack, they all have it as the "bush" at that end is a felt sleeve. As far as I am aware this has never been a source of wheel wobble unless it has completely given way.Your tyres are the same as mine so shouldn't be causing the problem. Have you checked your toe-in? Should be 1.5 to 2 mm on the rim. What pressures are you running? I'm on 19/20psi. Just a thought, are your front dampers OK?
Keep at it, Hugh.

[j.fernie]

Re: Wobbly Wheels

Hugh,
I'd wondered what the spacers were for! I shall be more circumspect next time I consider changing something.
I have checked the tracking recently and had 1 mm at the front edge of the tyre. Although that will give me less at the rim, it shouldn't be enough to create a wobble. There is no wear on the tyres.
Tyre pressures have just been raised from 18 to 22 psi. this moved the start of the wobble from 60 to 65 mph. This suggests that raising them again might push it beyond my usual max speed, but with such a light car excessive tyre pressures could be detrimental to handling - and probably make it bumpier on the road.
I guess a thorough strip down is required to locate the culprit. Everything is coming apart during the winter as I'm planning to fit an overdrive box, so I will look at a suspension overhaul at the same time.
Thanks for the advice
Jim

[b_caswell]

Re: Wobbly Wheels

Hi Jim, If your car is using the ribster Marlin wheels, check the are actually tight when the nuts are done up. Some of these wheels suffered from the inserts bottoming out and coming loose in the wheel even though the nut was tight.

[stevejgreen]

Re: Wobbly Wheels

As far as I recall the spacers were fitted on Mk2 Marina models. The clue is also a change of stud size. 3/8" on Mk1 to 7/16" on Mk2. I think this was done to improve the Marinas handling including the fitting of an anti roll bar. I think there were some geometry changes as well.
I had some rear wobble once, caused by an established garage fitting oversize headed countersunk screws to secure the drum after halfshaft bearing replacement. There is a similar screw intended to hold the front spacer in place. Neither of these screws have a function when the wheel nuts are tightened.
Good luck!

[j.fernie]

Re: Wobbly Wheels

I may have located the culprit - play on the lower trunnion link pin. I think new bushes are in order.
Thanks for all the advice.