Shuddering at 55 km/h NB8A

[Shambler]

Hi guys,
Just thought I'd ask the question before I get someone to look at it, I've had my MX for a few weeks now (1998 NB8A) and have noticed that at around 55 km/h the car shudders, and will keep shuddering until you pass 60km/s. This is actually quite an annoying problem, as I tend to stay a few under 60 on a lot of the roads around my house. Is there something obvious I should be checking for? My mechanical experience is sorely lacking, which is a pity as I don't really have the money to pay a service centre to have a look!

Any suggestions would be greatly appreciated!
Thanks,
Sam

[StanTheMan]

on an NB8A check all the bracing make sure they are secured
I'd look at a wheel ballancing & allignment if all the suspension bracing is tight.

[fattima]

I just picked up a 99 NB8A from the hail damage auctions here in Melbourne and it does exactly the same thing. As Stan mentions check the front end alignment as I know it is out on the car I purchased.

Where are you located? I ask because you are best getting the alignment checked by someone who knows MX5s not your local K-mart service centre.

[Col]

Cold tyres can cause this, more so if the car has been parked for a reasonable period and worse still if the tyres are getting a few years on them as the rubber continues to cure [harden] with time. Your tyres develop a flat spot which pretty much disappears when the tyres heat up.
Wheel balance and/or alignment, like the other guys said is also a major cause of what you describe.

Col

[Shambler]

Hi guys,
Thanks for the responses! I'll have a look at the bracing with my trusty downloaded workshop manual!
I think I'll probably go for the alignment anyway, any good places around Sydney to get that done? The whole car badly needs a service,
so if I could get them done both at once that'd help a lot!
The tires don't appear to be that old, but I'll look for that over the weekend. It doesn't appear to be reduced after an hour of driving though, so I'm not sure.
Probably got a few more questions as I'm new to all of this, I'm assuming I should try and keep the questions to this one thread rather than spam the forum?

Thanks for the responses, this is a great community!
Sam

[manga_blue]

I just picked up a 99 NB8A from the hail damage auctions here in Melbourne and it does exactly the same thing. As Stan mentions check the front end alignment as I know it is out on the car I purchased.

Where are you located? I ask because you are best getting the alignment checked by someone who knows MX5s not your local K-mart service centre.

So can you tell us how many MX5s you've got now, Bruce. Just a ballpark figure would do.

[fattima]

Why do you want to buy one

[StanTheMan]

....I think I'll probably go for the alignment anyway, any good places around Sydney to get that done? The whole car badly needs a service,
so if I could get them done both at once that'd help a lot!


Sam

Daniel at Spinning wheel. Don't settle for anything less.

mechanical work? not sure if I'd let a suspension place do that. I'd be taking it elsewhere.

[sliq]

Hi guys,
Thanks for the responses! I'll have a look at the bracing with my trusty downloaded workshop manual!
I think I'll probably go for the alignment anyway, any good places around Sydney to get that done? The whole car badly needs a service,
so if I could get them done both at once that'd help a lot!
The tires don't appear to be that old, but I'll look for that over the weekend. It doesn't appear to be reduced after an hour of driving though, so I'm not sure.
Probably got a few more questions as I'm new to all of this, I'm assuming I should try and keep the questions to this one thread rather than spam the forum?

Thanks for the responses, this is a great community!
Sam

spinning wheel or heasmans.

[Shambler]

I might give them a call then! What would be a ballpark figure on how much it would typically cost?

[StanTheMan]

$80-$90 for a 4 wheel allignmnet
not sure what they charge for a ballance

[Shambler]

Excellent! Thanks for all the replies, gives me a lot to work with

Sam

[Tony]

Hey Sam.

I had something similar in my NB8A, but it occurred at around 110 kph.

I checked the usual things; spanner check of underbody bracing, wheel bearings, shocks, bushes, wheel alignment and wheel balance. Nothing I did seemed to help.

Then I changed the tyres!

They were dodgy Sumitomo crap and even though they were less than half worn, I fitted some s-spec tyres for club days.

It was like a brand new car!!

It turns out that the old tyres, even though they had been re-balanced, introduced a harshness and low frequency vibration into the car at about 110 kph; when the roof was up the heavy glass rear window was shaking about like a junkie looking for a fix. This in turn created a booming noise in the cabin in much the same way as a loud speaker works. This shock wave effectively made the car feel as though it was shuddering with a chronic case of scuttle shake. It was however reduced slightly with the passengers window about half way down.

Once the new tyres went on it was as smooth as silk. I don't know if you share any of the same symptoms, but it may pay to either go for a run with the top down, or swap the wheels and tyres over with a mate and see if that makes any difference.

Best of luck!

Tony

[StanTheMan]

yes that is supposed to be Stu. Not Daniel

My apologies.

[MX5CHIC]

Had the same problem, took it for a wheel alignment and balance - twice, still had the same problem I began with, which was a vibration from 95 km/h through to 110 km/h.
Went back for a third wheel balance / alignment and decided to watch them at work - sure enough the dummies ignored the fact that one rim was buckled
New rim and vibration solved.

Lesson learned was to never take my car to K-Mart Auto Services.