Trailer tires: bias + radial mixing

Here's the situation: My trailer currently has two old worn bias-plhy tires (on the braked axle) that I plan to replace. On the other axle is a Goodyear Marathon (radial) that was replaced right before I bought it (so, it has a couple thousand miles on it now, max), and on the other side is a bias-ply Kenda that we put on to replace one of the old flatspotted tires when we got the trailer.

So my situation is that I have to replace two tires, and the other two are both pretty much new - but one is bias and one is radial. I'll note that the trailer has towed various cars to VIR, Watkins Glen, and several other trips with no issues, no flats, etc with this setup.

I've always read that you shouldn't mix bias and radial tires on a trailer, but for the life of me I can't really understand why. I'll drive the same speed and have the same load regardless of which is on there, and since the tires don't physically interact with each other I can't see why having a mix of them will affect much of anything (at least on a trailer, where performance isn't a concern).

So, is there some logic behind this, or is it just there so that tire manufacturers can tell you to replace all your tires at once?

I'll caveat by saying that most things I read just say mixing the types will result in increased wear and "affects ride quality," not that it is "dangerous" per se.

Also that as long as each axle has the same type on both sides, it is ok to run a mix (e.g. radials on front axle, bias on the rear axle).

Bias can flat spot on parking... Had a friends jeep with Bias ply TSL's.. It took a few miles for them to "round out" again.

I meant that it was flatspotted by someone locking up the brakes (previous owner). That won't round out ;)

Bias ply tires deflect more, and wear much more quickly as a result. I've mixed bias with radial when upgrading not really an issue with handling form my experience.

Turns out Tire Rack has the Goodyear radial trailer tires on a good sale, so I just go tthree of them to match the one already on there. $80 per tire in 15" is a decent deal.

last two times I've needed tires I've ended up buying them already mounted for $5-$10 more then just the tires... I hate white spoke wheels but there cheap with tires. Trailer parts supper store has a big tire sale right now. http://www.easternmarine.com/

Actually looks like they're about $12 more per tire than TR for the particular ones I got. I have a buddy to mount them up for cheap and I realy like my gunmetal wheels anyhow ;)

But yeah, my parents own a marina so I'm very aware of that site