Evening all, I have a suspension / shock absorber issue and hope some knowledgeable folk can give me a few pointers. I'm just back from my annual road-worthiness test and have a suspension test imbalance of 37% on the rear axle (maximum allowed is 30%). I have no error lights to indicate a failure of the suspension components. The test results are as follows:- Front Axle Nearside 20Mm / Offside 21Mm / Imbalance 5% Rear Axle Nearside 12Mm / Offside 19 Mm / Imbalance 37% For reference my previous test results (a year ago) were:- Front Axle Nearside 21Mm / Offside 22Mm / Imbalance 5% Rear Axle Nearside 21Mm / Offside 23Mm / Imbalance 9% I'm not sure if the "Mm" equates to millimetres but imagine that it does. The results (and particularly by reference to the previous results) would appear to suggest that there's a problem with the rear nearside shock absorber. That would be the one closest to the kerb. I asked the tester if he could say whether the shock was over-hard or over-soft but he wasn't able to clarify. On the way home I drove along the motorway cats-eyes to see if I could discern any difference from side to side. It seemed to both my passenger and I that the bumps caused by the cats-eyes were considerably more pronounced on the offside of the car. This basic test would indicate that perhaps the nearside shock is a little soft/weak. The test (official test) was carried out with the suspension set in normal mode. I wasn't able to ask them to re-test with sport mode selected unfortunately as the vehicle had already been taken off the test equipment and there's no going back through without a re-test appointment and fee. Any thoughts or diagnosis suggestions gratefully received.
Interesting and something the MOT doesn't test for. Have you got any info on how the test works? I guess the first step would be to visually inspect the shock and then perhaps get an SD2 plugged in. The suspension ECU actually monitors and tests the system and stores the results - I believe the SD2 can access this data.
if this is done will driving over a friction table are you sure this is not an alignment concern? Judging by the description I think you may have a toe setting issue on the rear of the car which would be much more common then a shock malfunction. To be honest I am not very familiar with your MOT procedures.
Don't know how MOT's are conducted in Ireland as opposed to u.k...Is it done by DVLA or do you use normal MOT stations? If it was done on a vibrating tester, i'd be shocked if it could detect such small margin of error on such a stiffly-sprung car. If there was a problem with the internal variable valve you would have a suspension error and consequent light on the dash. Unless it's leaking or there are no logged errors i guess all you could do is pull both the rear shocks, take off the springs and compare them. Otherwise, try another test station?
Thanks for the replies so far guys, appreciate the input. On most road cars this is just an inconvenience, fail the imbalance, go out sling in a couple of Monroe (or other) replacement shocks for a couple hundred quid and you're boxed. The F car replacements are US$1800+taxes+carriage so it's not "throw away" money (and one must replace in pairs too!) It's not an alignment issue, that was passed clean despite a aggressive set-up with nearly 3 degrees of negative camber and front toe set to OUT rather than IN. They also test on a vibrating plate - my guess is that this is to help identify loose or failing components like ball-joints, bushes etc. No problems with that test. Our car testing here is done by NCT (National Car Test) in dedicated test centres. Information on what they actualy test for is vague and I have yet to find out for certain whether a low number (12 above) means an over-hard or over-soft shock. I believe this particular test is a "bump" style test but reliable information is proving very hard to gather. This looks like it might be the type of test used ......... (I believe only about three EU states are using this, the balance being visual inspection mostly)....... Altesco Announces Revolutionary New Automobile Safety Testing Equipment "Suspension The Altesco suspension plates compares the amount of “bounce” in each of the wheels of your vehicle, left versus right and front versus rear. The digital processing console analyzes bounce data, and if results are not within normal ranges, this indicates that there is a problem requiring a visual inspection. A vehicle that shows measurements outside specifications may have suspension parts in need of adjustment or suspension parts that have reached the end of their life expectancy and need to be replaced. Replacement of worn-out suspension parts is the only repair you can make that will actually make a huge difference in the way your car rides and feels." Initially I was thinking that perhaps one of the shocks was stuck on "Sport" and the other on "Normal" but I'm beginning to doubt that now. I appreciate that the ECU should be monitoring the shock valve adjustment and flag a problem if there is one but does anyone have a diagnostic method I could try myself? Yes, Eddie, I was thinking maybe that's about all I can do on a DIY basis is strip out the two shocks from the rear, remove the springs and see if there's a noticeable difference between them. Another question. Does anyone know if there are rebuilding services available? Ireland/Uk/Europe preferably but USA considered if necessary. I know I've seen posts in Bradon service threads where they refer to rebuilding shocks but from recollection those threads related to 355 or older vehicles. On the upside, if one of the shocks IS knackered I'm not too cut up about it 'cos I know it will be WAY better when I get it fixed! I just don't need the replacement parts cost and I particularly do not want to incur those costs unnecessarily. As ever guys, thanks for reading and your responses, any input very welcome.
To be Honest Greg, I've only had to replace due to internal valve issues, even on high mileage cars they ar very robust. If there is no sign of leakage and the internal valve is working I'm surprised they managed to produce this result using that method....
Cheers Eddie, that's good to know. Irish roads are notoriously hard on suspension components it has to be said! Even more so with the economy in tatters, the pot-holes are multiplying like frog-spawn these days. At the very least I certainly will swap the components left to right and avail of my cheap re-test on this one fail issue. If that's all I do it will be very interesting to see does the problem move side to side. I did see the testing chap going off and getting an accurate tyre pressure gauge and testing both sides before repeating the test so he gave the car every chance. It's also possible of course that the test equipment is not reliable or not calibrated. Is the wee servo for the valve serviceable at all do you know?
Hmmm, now that you mentioned tire pressure, I wonder if it would help if you "tweak" the tire pressure (ie. one side way more inflated than the other) to your advantage to try and even it out? I seems like it is very close to passing, and that may work. However, it seems like you will have to make a proper correction before next year.
Chris, don't think for a minute that thought didn't occur to me! Seriously though, if there really is something wrong I'd just as soon repair or replace and get it right.
looking at the data in the original post, I am left wondering if the problem is that the springs have compressed over the decades, and that all you really need is a ride hight adjustment, corner weighting, and an alignment. Also note, the 360 (and a couple of other cars from that era) have insufficient "structure" at the chassis point where the shock and spring loads are transmitted to the chassis. My mechanic has had several 360 that need some structural work there (mainly at the front.) F355s used on track also suffer from this, and challenge cars have beefed up chassis pick up points. I would be surprised if the problem is the shocks themselves.
Where did you get the car tested?, if it was Deansgrange I had the same issue.... I told them it was Boll!x. I insisted they to run it through another lane..... presto no problem (it was the test machine), they also told me slip slide failure - the suspension bushes had less than 1000 miles on them. Different lane no problem. Lane 3 was the problem from memory. Bring the car to another garage, from memory there is an AA Pitstop on long mile road with machine for testing shocks - see what result you get there before doing anything.
Actually Mitch, the tester WAS referring to springs rather than the shocks as it happens so you could well have a point there. Tom, SNAP! YES, it was Deansgrange and YES it was LANE THREE! How long ago were you there? Is it the Advance Pitstop Garage that has the equipment?
Disturbingly June 2012 - Well now there is a good revenue driver if I ever saw one. Most people don't question, I knew it had to wrong so I was a bit of a .....you know what... when they gave me the results.... Yes I think it is Advance - Ring them to confirm they still have it.
So I went back to the test centre today. The event probably raised more questions than it answered. First of all, let me clarify that this particular test involves putting first the front axle and then the rear axle on two separate vibrating plates. The left side is given a right good rattle followed by the right and the idea is to measure the performance of the suspension (presumably both shock absorber & spring performance) on the one side as compared to the other. Last week I had three results in a tight group 19~21 and one standing out at 12. I asked whether the odd one out indicated an over-hard or an over-soft or an over-damped or an under-damped corner. The test centre personnel were not able to answer that question at all. I asked what Mm meant. Was it millimeters or something else? The test centre personnel were not able answer to that question at all. What I was told this evening is that a typical Nissan Micra with "the shocks hanging out of it" might register 99 and 72 across an axle. That result would probably indicate that both shocks were knackered but with an imbalance of 27% it would pass the test. I was told that my shocks with much lower results (high teens / low twenties) probably indicate very well damped suspension but because the numbers are lower, the tolerance for imbalance (in terms of a raw number) are much lower. So, on with the re-test (Lane 4 tonight versus Lane 3 last week)......... The test results are as follows:- Front Axle Nearside 12Mm / Offside 17Mm / Imbalance 29% PASS Rear Axle Nearside 21Mm / Offside 20Mm / Imbalance 5% PASS For reference my previous test results (a week ago) were:- Front Axle Nearside 20Mm / Offside 21Mm / Imbalance 5% PASS Rear Axle Nearside 12Mm / Offside 19Mm / Imbalance 37% FAIL So, I've now got a pass and all is well in the world? Hardly! Tonight my rear suspension passed with flying colours but I almost fail my front suspension test? What's going on? I'm at a loss! All I did in the meantime was drive 5 miles in either direction! A cynical person might notice that it's almost as though last weeks rear results have magically transferred to the front axle and last weeks front results have similarly transferred to the rear axle. It does occur to me that level of fuel could have an important implication. My tank was near empty for both tests. I suspect that if one filled the tank it might cause the suspension to display greater movement to the input from the vibrating plates. More movement presumably resulting in larger numbers thereby allowing the imbalance figure (30% of the higher number) to be greater, thereby allowing a greater discrepancy between sides to be tolerated. Similarly, perhaps setting the tyres to higher pressure would also force the suspension to work harder, resulting in bigger numbers and again, a greater tolerance between sides. I dunno! Ok, I got a cert for a year but I really don't know if I have a problem or not! Frustrating. Anyway thanks for all the feedback (particularly that "gem" you threw in there Tom!). If anyone has any thoughts or knowledge of how this test works and what exactly is being measured please feel free to post!
Seems to me that any organization that tests the same car on different days and gets wildly different results has some explaining and apologizing to do, and in no case should be allowed to make measurements that have a legal consequence for its customers. Here in California we have no such stringent chassis testing requirements, just emissions, but were this to happen to me I'd file a complaint with the state government, try get my money refunded, and then go to a different shop.
What was their excuse for the problem transferring front to rear? Seem like a useless test based on the numbers you posted. Is it +/- 98% accuracy on their test equipment? LOL
Ordinarily I wouldn't ever suggest this but I would really consider writing a solicitors letter to Nct looking for a formal response and if I didn't get one in a reasonable timescale I would be making contact with a consumer shore on radio or TV there have been enough scandals with that organisation in recent times, the most generous answer is crap calibration of the machines, the most likely is fraud.
Yes, I would agree, the level of differential between test 1 and 2 appears scandalous. The car had been used for an all-day track event only 5 days prior to the first test (some of that time in the hands of a regular racing driver) and performed better than ever with absolutely nothing to indicate any problem whatsoever. The test is fully automated. The only human intervention which could (perhaps) effect the outcome is the locating of the wheels on the sweet spot (if there is one) on the vibrating plates. Outside of this my suspension is either reacting randomly and inconsistently to input or the test equipment is producing random and inconsistent results. The testing chaps weren't able to explain. They were complimentary of the condition of the car and somewhat apologetic about the variance between the two tests but no, they couldn't or wouldn't offer an explanation.
Incidentally, for anyone reading this thread in the future, I contacted Bradan who confirmed that they do indeed offer a rebuilding service. Not silly cheap and together with shipping and down-time it would have been quite an expense and inconvenience but it would have been a lot cheaper than purchasing new replacements.
