Monday, 20 October 2025

Rake and Trail

 The windscreen wipers on my Fiat Panda judder and creak, even when you fit new wiper blades. My friend (who works in vehicle development) asked the very wise question, why do they judder on old cars, but not new ones? What has deteriorated? On Sunday I spent a fascinating hour in the rain with my car testing different theories and remedies.

 His theory is that the spring that holds the blade down onto the windscreen is weak.

 Some random chap on youtube says that the wiper arm is twisted and that the blade is contacting the windscreen ahead of the arm.

 The advice on the Euro Car Parts website is to change the wiper arms.

 I was interested in the behaviour of the wiper blade. In cross section it's shaped like a Christmas tree and it's supposed to flex at the "trunk" so that it follows behind the arm (kind of like the bristles of a paint brush) .


I didn't have new springs for the wiper arms, but I lubricated and exercised the hinge and the spring attachment points. I also added extra pressure to the wiper arm with my hand. This all affects the nature and frequency of the judder, but it didn’t solve it.

 My theory is clearly wrong because new wiper blades exhibit the same judder, but I cleaned and examined my blades. It made no difference.

 The random guy on youtube is right! My wipers only judder on the way up. I put a little twist in the wiper arm with two adjustable spanners so that the blade was a little bit further behind the arm and they started to work perfectly. My theory is that the arms haven't twisted over the lifetime of the vehicle, but that the hinges have worn asymmetrically and the twist I added to the arms is counteracting that. I think that buying new wiper arms would probably work even better, but cost more.

 Richard "North Plymouth Drizzle Laboratory" B

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