| Over 60 mph the car had a judder which felt exactly like the wheels needed balancing. As the old tyres were pretty worn, I had new tyres fitted all round and the wheels carefully balanced (I watched the guy do it). Judder just the same as before. During balancing, it was noted that 2 of the wheels are running very slightly out of true. Is this likely to be the cause of the problem, or are there other possible transmission items I should check out before splashing out on new wheels? The wheels are really light 8-spoke alloys, 6x14 inch which the car came with, and don't appear damaged at all under visual inspection. Tyres: Yokohama A539 185x60. (1/01) |
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You shouldn't need new wheels, at least if the very slightly out of true is really only very slight. It might be worth borrowing a set of wheels (or just two?) before you buy new ones. It's also worth checking the prop shaft for balance and possibly running out of true - I suppose it's possible it's got bent (although I've never come across that). I drove a Sierra once that had a badly out of balance shaft though - it had to be replaced. It might also be a good idea to get a geometry check done, although that again shouldn't really cause judder. (1/01) |
| I did hear from a canadian miata driver that the 5 does this at about 100kph. I'm told that it dissapears when you get up to 110kph. It is a well known effect. I have not noticed it on mine as I've had the hard top on since I bought it. (1/01) |
| Over 60-70 MPH won't be balancing as this is more around 30-50 MPG. Get a 4 wheel track or propper 4 wheel aligments done which should sort the problem. (1/01) |
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I did hear from a canadian miata driver that the 5 does this at about 100kph. I'm told that it dissapears when you get up to 110kph. It is a well known effect. Yeah - they talk about it all the time on the US list and miata.net. But they shouldn't do it (ie the cars shouldn't judder). Mine doesn't. If everything is set up correctly, they don't. Tyres, wheels, balance of them, wheel geometry, suspension, prop shaft, chassis rigidity probably all play a part. (1/01) |
| The other trick in the manual is the dimension from PPF (power plant frame) linking gearbox to diff .. and the bottom of the chassis rails .. this dim adjustment has been know to help. (1/01) |
| Did I once hear of something on the Miata list known as the "Miata shimmy" but IIRC that was at about 50/60mph...? (1/01) |
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Balancing problems can show at any speed and in very small speed bands. You can not say that it will not be balancing because it happens
at a certain speed. In this case, it sounds as though it isn't
balancing as they have all been done, BUT |
| In the Miata.net forum, search for the word "shimmy". This should pull up a good number of threads relating to this problem. (1/01) |
| Mine still does it, though fitting the cockpit brace has helped. Balanced wheels, 4 wheel allignment back to factory defaults and the fitting of a Moss front chassis brace made no difference though. I was planning to see if a strut brace also helped before going any further. It's definately a 60 - 65 MPH thing though. (1/01) |
| I had this problem as well. Tyre walls were cracked. But, new tyres and balancing fixed it. I can now drive in comfort without having my cheeks shake as if I was in a gravity experiment. I reckon they cocked up the balancing, take it back and have them check it. And get the wheel alignment checked at the same time. (1/01) |
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Thanks to everyone who replied to my question about judder at 60mph plus. The car did have 4-wheel alignment done when I bought it, paid for by the dealer when we both saw the 2 old front tyres were badly scrubbed on the outside... I've got a full 'before & after' printout of the various adjustments made, but as this point things get complicated because car's previous (Japanese) owner had lowered the suspension drastically (2-3 inches?). Are the standard recommended suspension settings applicable to a lowered car? I've got no complaints on the car's handling, but ground clearance is a big challenge on Argyll roads... The Eunos already has stiffening braces (one over the engine and another between the seatbelt mounts), plus a big, steel 4-point-mounting roll cage. So I don't think I can do anything further in that direction! A return trip to an alignment place looks on the cards, because I like this car more everytime I drive it, and I'm determined to sort the problem. (Trying not to think about cost of replacement propshaft). (1/01) |
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You will not get stock alignment with that much lowering .. just aim for 1.5 deg or min camber on the rear .. remove 0.5 degree for the front (so aim for 1) ... set toe in at rear as stock, set toe at front at zero or little in .. and castor max.. .. and you have not seen the road I got my car up in Italy .. makes forestry roads in Argyll seem tame (two brothers live down 2-7 miles roads .. passed with 2" lowering no probs ..just 5-10 mph!). The Italian road was a public road .. just had 8" gullies washed out of it! (1/01) |
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I'd consider trying to get it raised a bit. 35mm or so lowering is OK, but for road use you start to run into problems if lower. Also you are just not running the suspension in the designed configuration, and that's bound to lead to various problems, of which sleeping policemen are the least! (I sometimes touch the stupid "cushions" around here with standard suspension - I always try and get one side's wheels on the flat bits.) The standard alignments need modifying to take lowering into account. Camber needs reducing the lower it is (quite significantly) and caster needs increasing (if possible) Has it been lowered with short springs, or has it got serious shock absorber mods? I think I'd be looking at replacing the springs with standard ones, or getting a complete shock absorber/spring pack (eg from Moss). (1/01) |