tire is not the same size

[tf5598]

I just had one of four trailer tires replaced. The original tires were F78-14ST, and the tire company replaced the bad one with a Carlisle 205 75D14 (this new tire says on the side of it "replaces F78-14ST"). When I put the new tire up against one of the old ones, the new one is noticeably smaller (they are both off the trailer). Can anybody clue me in on this? Can I use a tire that is visibly smaller or am I asking for problems? Thanks.<br /><br />additional info posted 10pm c: both tires are C rated for 1760lbs with 50 psi cold. Looking more closely at the two, I noticed the old tire has 4 plies on the tread, and the new one has only 2 plies.

 

[DJ]

Re: tire is not the same size

hugh,<br /><br />Since each wheel spins independently, it won't cause any mechanical problems. I would however check the weight ratings of each to make sure the new one is at least the same, or better, rating.

 

[CBU]

Re: tire is not the same size

hugh g rection:I was just talking to a tire shop about the same thing for my muscle car and boat trailer.F78 tire are bias ply and your replacement is a radial-tire guy tells me bias ply tires sometimes have a bit different shape than equal radials due to construction.He says bias ply can be a bit more ballony and the radial will have straighter/tighter sidewalls/treadfoot.Ill credit him w/this info but,thought Id pass it along.Also I'm not certain but I believe some states don't allow and tire shops don't recommend mixing bias and radial tires-for motor vehicles anyway.Got to be some tire pros nearby!

 

[Boatist]

Re: tire is not the same size

Hugh<br />To start with both tires are Bias Ply tires. A radial would be ST205/75R14. Tire Might carry the same weight but I would not accept it as a replacement unless I was replaceing both tires on the same axel. The fact that tire is smaller in height means axel will be lower on one side. Since no way to adjust camber on axel both your Tires will run at a slight angle and have more weight on one side. Tread may wear on one edge quicker and also run hotter on one edge. It may be a small enough difference to not cause a problem but since both sizes are available and the same price in West marine I would not accept. If I did decide to keep I would at least make sure that it is not on axel with brakes.

 

[CBU]

Re: tire is not the same size

Hugh,<br /> Big whoops on me!-you probably realized that anyway.I stay up too late and skim too quickly sometimes.Just left tire shop w/my new radials for car and trlr.-asked tire guy and he says f78 tires are manufactured alpha-numeric and the p205 are made metric-says measured different when built but, equal replacements?He says difference should only be millimeters and wouldnt be noticed on a 2axle trlr.This is his opinion but,I'm kinda leaning toward Boatist because the f78 are readily available.Oh well

 

[Bondo]

Re: tire is not the same size

Replace your tires in Pairs.... Then keep the Odd one for a Spare......<br />If you must run different size tires, the shorter tire Should be run on the Left side... ALL Roads are Crowned... So the trailer will set as level as possible, because the left side of the driving lane is higher than the right side....