If the problem is new with the tires, I would look there. Typically tire vibration due to balance problems are frequency (speed) driven but the harmonic tends to be around 60-70 MPH on most passenger tires and critical speed increases with tire diameter. 45-50 would be a bit low but still worth checking balance - but FIRST I would jack it up and spin fronts and look for out of round tire or wheel. Best is probably to put a brick or some reference at edge of tread and see if distance changes as tire rotates - probably should be less than 1/8 inch variation. If fronts are good, you could swap rears to front to see if the problem stays same of changes and of course look for out-of-round before you put car back down. Then take it back to where tires were balanced and ask them to recheck - its possible they made a mistake or you threw a weight - but look for large amounts of weights as they tend to indicate tire / wheel problems. Its also possible tires rotated on wheel - the old 15's tend to fit looser than the 14's and I have seen it happen on race cars - typically when too much tire lube was used AND too much HP applied suddenly - but as I said the older wheels are looser fit and would be more prone to such a problem. . pennsy300@xxxxxxx wrote: > > > My 300D convert (with the new Coker radials) has a significant vibration, > but only between 45 and 50 mph. Above or below this speed all is just > perfect. My question: Is this characteristic typical of tire problems, > wheel > alignment, or something else? I sure would like to get it fixed. Thanx > for whatever help is out there. Terry McTaggart > **************Mortgage rates drop to record lows. $200,000 for $1,029/mo > Fixed. LendingTree® > (http://pr.atwola.com/promoclk/100126575x1222653866x1201461148/aol?redir=http:%2F%2Fwww.lendingtree.com%2Fborrower%2Falliance%2Ffrom.as > <http://pr.atwola.com/promoclk/100126575x1222653866x1201461148/aol?redir=http:%2F%2Fwww.lendingtree.com%2Fborrower%2Falliance%2Ffrom.as> > p%3Fwhereto%3Dpromopagev3%26promo%3D00279%26loan%5Ftype%3D2%26source%3D28895 > 60%26esourceid%3D2889560%26800num%3D1%2D800%2D289%2D3915%26AdType%3D2) > > [Non-text portions of this message have been removed] > > ------------------------------------ To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm For archives go to http://www.forwardlook.net/300-archive/Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Chrysler300/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/Chrysler300/join (Yahoo! ID required) <*> To change settings via email: mailto:Chrysler300-digest@xxxxxxxxxxxxxxx mailto:Chrysler300-fullfeatured@xxxxxxxxxxxxxxx <*> To unsubscribe from this group, send an email to: Chrysler300-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/