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Date: 25 Nov 2002 04:41:35 -0800
From: alancemornopsamo.com (Lance Morgan)
Subject: Re: c900 harmonic droning?


>Someone who looks an awful lot like Lance Morgan <alancemornopsamo.com> wrote: >> I recently purchased a 91 900S (briefly had a 86 900T years ago), and >> am really enjoying it. >> I've noticed something I'd appreciate comments on: a harmonic type >> droning - always starting at 70 mph up to at least 85 mph, and have >> also sometimes heard it ~ 45 mph in 3rd, albeit a slightly different >> tone. >> The noise is moderate in pitch and, at high speed, has a repetitive >> frequency of less than 1 second. It reminds me of riding in a twin >> engine airplane >Tires maybe? If it's the kind of noise I think you're describing, >it's usually caused by two things that are almost, but not exactly, >at the same frequency. Two tires that are just a *bit* different >sized (could be just inflation pressure) might make the noise you >describe. Never heard it myself, but I'd be interested to know if your tires >are all the same size and pressure. >> The noise completely abates when I push the clutch in, coasting >>at high speed. >Ah, well that shoots *that* theory down, I think. I was thinking engine, tranny, and/or drive axles - either independently or some adverse interaction of the two or three (and I meant to say 'twin engine "prop" airplane'). >> Probable cause? >>Is there a twin engine airplane following you, except when you >>push in the clutch, by any chance? Unlikely, I know, but... Heh. That used to happen when I had the 900T ;-) >> Thank you, >> Lance >> 5 spd 3dr 125K >Hm. Pretty young for it to be inner drivers, which could be >another possibility. How are the front two tires for match and pressure? I've discounted the tires, given that the noise goes away when coasting. But they are very high treadwear Cooper somethings (seemingly steel belts w/o rubber plies, with a rating of 640!), which I'll be replacing shortly [likely will change from the (all) 185/65s to 195/60s)] The fronts were within 2 lbs of each other Return to Main Index
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