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On my MOT brake test, one rear wheel locked up on the maximum force test at about half the reading of the other one, actually less than the force shown at that wheel for the handbrake. The front brakes were about as expected and the total force was still far above the required 50%. The shop guy was trying to convince me that the test was borderline because of the "imbalance", although the actual imbalance test only showed a 9% difference at the back and 1% at the front. Short of grease on the roller, what could cause one rear wheel to lock up at such low force?
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>>what could cause one rear wheel to lock up at such low force?
Sticky wheel cylinder?
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i would say the wheel cylinder is leaking
needs looking at yesterday......
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Here's the numbers:
Imbalance test:
Service F/N/S 65 kgf
Service F/O/S 64 kgf (1%)
Service R/N/S 107 kgf
Service R/O/S 97 kgf (9%)
Max Force Test:
Service F/N/S 113 kgf (L)
Service F/O/S 116 kgf (L)
Service R/N/S 137 kgf (L)
Service R/O/S 207 kgf
Parking R/N/S 155 kgf
Parking R/O/S 123 kgf
Does that help any?
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Bought wheel cylinders before from Unipart for £8-9 each.
Fit a new one to the side where the efficiency was low as per the Haynes manual.
They can either sieze or leak causing malfunction.
Once fitted make sure you bleed it.
The above is optional - but its the steP I would take considering how cheap theay are to buy.
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Check tyres, pressure and wear. Try changing the tyres over left to right and see if the other wheel locks up.
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Wheel cyliners, thought an 00 Elise would have disc brakes all round. If thats the case then chaging the brake pads normally does it.
You might need to wind back the calipers depending on the type of handbrake fitted
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Yes, discs all round, so not wheel cylinders as such. Pads are fairly new on all wheels, about 5,000 miles. Car had a full service a couple of months ago when the brake fluid was replaced. Brakes should have been inspected then but probably not tested except on the road.
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I've had a look at the calipers today and can't see any hint of a leak even after a good working over with the brake pedal. Could it be so insignificant that I wouldn't spot it? Certainly not enough liquid to form a drip either from the piston or the hose attachment.
The only slightly unusual thing was on the cable from the handbrake. The handbrake operates the same brake calipers, and on the nearside rear the wire where it emerges to go to the caliper is black just on the section which moves as the handbrake is applied. On the offside it is all silver. I don't know if that is grease, rust, or what. It is dry but slightly shiny.
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is there any noticeable difference in colour between the disc's, possible caliper binding (previosly) causeing one side to overheat/get warmer, causeing the disc/pad to glaze causeing your inbalance, looking at your figures they are not to bad however it may cause problems later, better to track it down now, the only thing that the tester could of failed it on at the rear would have been rate of increase/decrease, this would point to sticky pistons in the caliper as you have not said that he mentioned it then i would assume that it was okay,Regards TB
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The two sides of the disc are both shiny and look the same to me, although its hard to compare because the light is different. The shiny track on the inside is narrower because the two pads on the Elise are different sizes. I've checked the disc temperatures after a drive and there doesn't seem to be any difference.
The test result for increase/decrease was just PASS and the tester didn't say anything about it.
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is the offside different to the nearside i meant, sorry if i did not make it clear, Regards TB
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No, nearside and offside discs look and feel the same. The only difference I can see on the calipers is the little dark section of the handbrake cable where it emerges from its casing a few inches from where it is attached to the caliper.
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