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road shutter


Guest trofeo73
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Guest trofeo73

I am experiecing a slight road shutter at around 74 mph. It seems that the rougher the road is the worse it gets. I have a supsicion that the suspension may be to blame. The car has new tires on it too. My Trofeo has the FE3 suspension found on the Reattas right??? At 115 mph(yikes!!!) shocked.gif" border="0 It did'nt shake as bad. It could have been the road or the speed that caused it not to shake. Could warped rotors(mine are warped) or some other factor cause it to shake. It would be easy to pinpoint if it was all the time but it only shakes real bad depending on road conditions. Any ideas????????? frown.gif" border="0

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Noticable shake (not just light vibration) is usually caused by harmonics. If the tires/wheels are round (haven't been flat-spotted by hard braking) and balanced, the next place to look is the struts (shocks). Even one that is shock-bar can cause serious shudder.

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Guest trofeo73

well Padgett, the tires are brand new, however the rotors feel badly warped, the pedel pulses and the brakes make a loud squell. The dash seems to shake the most on my car too. I do notice that some times if I make a hard right turn I hear a squeel coming from the drivers side WITHOUT applying the brakes. confused.gif" border="0

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I also have a bad shudder in my convertible starting right around 50 mph. It becomes less noticable at 60+. I have new tires, just had the brakes done (including rotors), and also put new struts on the front. I decided it's either the ball joints or the bushings on the front end. I've ordered both, but haven't received them yet. I'll let you know if this helps the "waggle".

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115 mph? Wow. I don't think I'd trust the Reatta that fast.<P>My "old" 01 VW Jetta on the other hand was solid as a rock at that speed. smile.gif" border="0<P>(Yes, I know it's bad to go that fast. No, I do not make a habit of it.) tongue.gif" border="0

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Well 55-70 mph is the harmonic range for a 15 inch tire (larger diameter raises onset speed) so certainly sounds like what you are getting into. Would almost bet that if tires are new that you have a bent wheel (need to spin and measure runout.<P>Might also check wheel nut torque - is supposed to be 90 lb-ft and is what clamps the whole rotor assembly as well.<P>Myrule of thumb is that if you feel it in the steering wheel, it is front tire(s) - could just be one - if cowl shake but not in wheel, look to rear.<P>BTW the PROM appears to have a fuel cut off speed of 125 mph/restore at 123 so that would be it.

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Guest trofeo73

Thanks Paddget, I will check the nut torque. I may do new struts and suspension components all the way around. I havent checked the wheel bearings on the back, just the front. When I had it at that speed(115) that was all she would go. I had it to the floor on level ground. Of course the overdrive wasn't engaged either. My old sunbird convertable with the 2.0 liter turbo engine would do 135 to 140 with no problem. Of course I had a few modifications and steel in my balls too! Weighing in at 2500 lbs helps too. With close to 3400 lbs and me the Trofeo does all right for having 165 hp. I guess my 3800 with 110 k on it isnt as good as new but it does just fine around town and on the highway at saner speeds grin.gif" border="0

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I see you're in Ms, but it sounds like hub/rotor/wheel corrosion. There can become a stacked tolerance problem in the front wheel drive cars where the brake rotor hub gets rusty/deformed(sometimes from over-tourque of the lug nuts). Try new rotors(if you get them resurfaced, special attention has to be paid for this, some places only watch the braking surface) and clean the hub and wheel. Also, especially if steel wheels, watch for deformed(i.e. bent) rims.

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Have seen Aluminum wheels with excessive runnout as well. Generally can handle up to .060" lateral but even .030" vertical is bad news.<P>One other thing you might try is inflating the tires to 40 psi and see if there is a difference.<P>In any event a significant shudder/vibration needs to be checked out as it could be early warning of a tire that is separating or a suspension link about to let go.<P>*In general* you can hear a wheel bearing going.<P>BTW, torque is really more important that HP in determining top end in a particular gear (use HP to figure out what gears to use in the first place).<P>Waaaay back in 1973-74 I got into a rather heated discussion with Bruce Crower (he had a column in hot rod at the time) about different camshafts to use and for why. <P>One of the side elements was that at 60 mph most of the power of the current engines at 60 mph went to turn the engine (was not unusual to see 3,000 rpm at 60 mph in top) and that if you really wanted to see decent MPG out of a gas engine, you wanted really steep (for the time) gearing - like 2,000 rpm at 70 mph. Sonofagun 8*).<P>Bottom line is that while hp is rated at 4800 rpm, the torque curve peaks early and falls off pretty fast, dropping under 200 lb-ft at 4,000 rpm.<P>Haven't run the math but suspect 115 mph is right around there<p>[ 11-30-2001: Message edited by: padgett ]

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