Hi all.
I had to get my Kendo NC M.O.Td last Monday. I took it to my local Toyota dealer as it’s just down the road & they look after my wifes car & I’ve used them for my other car. I trust them & never had an issue with them, very professional.
Usually I take my MX5 to the Mazda dealer I bought it from if any work is needed, however I’m in Bristol & they are in Oxford & during these covid times etc. hence taking it to the Toyota garage.
It failed the M.O.T. because the rear passenger side shock was leaking oil. I instructed them to fit the new shock, which they did & re-M.O.Td it. They told me the rear tyres were on 3mm (fronts were 5mm).
and would recommend new tyres. I declined to have them fitted as the bill was already creeping up, so kept the old ones for the time being (have since ordered new ones).
Now here’s the thing. Twice since picking the car up I have accelerated out of a corner only to find the back sliding out! something that has never happened before!
Now I don’t know if I’m just being paranoid, or whether it’s just a combination of the cold weather plus low tread or something else.
I suppose my real question is, would anything they would have done when changing the rear shock affect the power down to the road? I’m primarily thinking something to do with the slip diff.
Hopefully I’m being paranoid and it is down to the tyres & weather.
Many thanks for any insight in advance
Cheers my fellow MX5ers
Jeff.
They fitted a new shock, but you didn’t pay for an alignment afterwards. Any work on suspension will affect alignment. Plus you’ve let your tyres get down low.
Not their fault. Check it in to Kwikfit etc. Its worth doing anyhow.
Thanks for the quick reply. A couple of things.
The alignment was done and noted. I’m really not trying to blame anybody just trying to figure if this down to the tyre & my driving. But also am I right in thinking the slip diff wouldn’t any bearing on this? New tyres are on the way.
p.s. Our local Kwikfit is a rip off merchant and wouldn’t take it there ever again, got caught twice 
Many thanks for your reply. 
Post the alingment numbers
Do you think that is what it is??
One shock only? Recommended to do them in pairs, and a competent alignment check too.
I’d better start saving then. 
When replacing a shock absorber it is preferable to replace both on an axle so you have matched pairs with the same damping characteristics. If you only replace one then you need to make sure it is the same make and type as that fitted to the other side. Shock absorbers from different manufacturers will have different characteristics as each manufacturer will use their own valving arrangement.
If the garage “did the alignment” and noted, then you should have received a printout with the measurements made.
Otherwise its impossible to say whether your cars handling is down to poor alignment, a dying other shock, substandard tyres or the weather.
Think perhaps when we are allowed out again I’ll give my Mazda garage a call.
Many thanks for you advice
p.s. forgot to mention that the car has also been BBR’d so a bit of extra oomf coming out of the corners. 
Hmm, performance MX5 and skimping on maintenance (tyres, shocks). Garages are open for repairs. Mazda garages in Bristol can also fix MX5s.
The tyres might have been technically legal, but you were sailing close to the wind.
Skimping!!!
Tyres are fine, if a little low, & didn’t know about the leaking shock until the MOT
I can assure you I don’t ‘Skimp’
When one of my rear shocks blew out during a drive down to Cornwall years ago, I knew all about it very quickly. I had Protec shocks, so when I get home, I took both rears off (one had blown) and had them rebuilt back to new.
Sorry, when I read your original post, and you said you didn’t get new tyres because of the size of the bill, I thought…
Yes, went in for it’s MOT - expecting £55, they came back with ‘needs a new shock’ £330, so we’re at
£330+
£55+
£250 - 2 new tyres
so I’m thinking …‘■■■■■■ £650 - £700…not sure I’ve got enough in my account at the moment…perhaps i’ll hold fire on the tyres for the time being’
As I said, I’ve since ordered them.
What tyres have you got on ATM?
Avons ZV7s but have ordered Dunlop Maxx sport to replace the rears, will order 2 more for the front in a month or 2.
I had those on mine when I first had the car, ok when fresh and plenty of tread, not so when they got low on tread. Like many I suspect, they go off when they get hard etc
One more query, the pressures, have they been altered during any work done, sometimes over inflation can cause problems like you mentioned.
Don’t think I’d be happy having just one shock changed though, do them in pairs, ie both rears.
Your experience is not unique. My wife’s 2016 Mazda2 went in for an MOT. That should be cheap I thought as it had been serviced about 9 months earlier.
The MOT identified both front tyres needed replacing because tracking had caused uneven wear to the limit. Rear tyres we’re starting to have side wall Pershing. Front disks were badly corroded. In the end it cost over £600.
That’s on top of the new battery I had to buy a few months ago.
Personally and it’s recommended for safety to replace an axle pair, as others have said.
IF the car is relatively new then you can get away with just the one.
Fitting a new shock on one side and an old one on the other can make it handle badly and affect the safety in my opinion.
As a comparison you wouldn’t just change one disc brake and leave the other side with an old one on.
And yes a good 4 wheel alignment would also be needed.
The MX5 does seem to be very much affected by the state of the tyres. Aged or worn tyres make the rear very loose and quite dangerous.
I have Michelin Pilot Sport on mine and it’s almost impossible to get the back out.