Clearance for fenders? (update 4-9-13)

[les45]

(Finally installed new tires and modified fenders; see later post below)

After reading several related posts on upgrading tires, I've been convinced to stick to my original plan to upgrade to 13" tires on my 5X8 NT trailer. This will mean raising my existing fenders and making them wider and longer to cover the larger tires. The 13" tires will come to the bottom of the lip on my existing fender as shown in the pic below. I want to keep the flat fender theme for my weekender so my thoughts are to cover the existing fender with painted wood to make it wider and longer. My only question then is how high to raise the fender without going too far. As you can see, I left plenty of safety factor for the existing 12" tires but part of that was in making the fender lines flow with the lines of the frame. Does anyone know how to tell how much vertical clearance you need for the fenders on the1,700 lb NT trailer?

[absolutsnwbrdr]

Measure the distance between the top of the axle and the underside of the leaf spring bracket. That will tell you how much your max travel could ever possibly be. But since your trailer is probably only weighing in at half the rated weight, there's a 99% chance you'll never bottom out. If you somehow manage to do so, you'll probably have bigger problems than just a tire rubbing on your fender.

You have MASSIVE amounts of clearance right now, so you most likely wont even have to move your fenders. Heck, you could probably move them down even after you get 13" tires. Increasing the wheel and tire size by 1" is only going to move the top of the tire about 1/2" closer to the fender.

For what its worth, I only have about 2-1/4" above my tire, and have never had it rub. My trailer weighs about 1300-1400lbs loaded, and its on the HF 1720lb trailer (same thing as the NT, but only 4' wide). I travel bumpy dirt forest service roads quite often.

[TPMcGinty]

I'd have to agree with Zach. You probably won't need to do anything. I'd put the new tires and rims on and see where you stand.

[les45]

You have MASSIVE amounts of clearance right now, so you most likely wont even have to move your fenders. Heck, you could probably move them down even after you get 13" tires. Increasing the wheel and tire size by 1" is only going to move the top of the tire about 1/2" closer to the fender.

Thanks,Zach, but according to the charts, the narrowest profile 13" tire (needed to clear the frame horizontally) is 24" tall. That's 3 1/2" above the top of my 12 inchers and right at the lip of the existing fender. The top of my springs to the frame is 4" which is even more clearance than what I have now. I was hoping that I could keep the clearance down around 2" so that the fenders don't look too high when I move them up. I guess I could put a 2" bumper pad on top of the springs to limit their upward travel just in case.

[absolutsnwbrdr]

Wow I didnt think a tire for a 13" wheel would be that much taller. I wouldn't go through the hassle of installing bump stops though. On the rare chance that you may compress the springs the full 4", your trailer is either grossly overloaded, or you hit a hell of a pothole - in which case you would probably bend the axle.

As I said, I've been fine with 2-1/4" clear, and I'm not gentle on the thing.

[TPMcGinty]

My 13" tire isn't that much bigger than my 12" tire. I'd take the 12" tire into a tire shop and ask them to pull out a 13" tire to compare with. You might be surprised.

[angib]

Thanks,Zach, but according to the charts, the narrowest profile 13" tire (needed to clear the frame horizontally) is 24" tall. That's 3 1/2" above the top of my 12 inchers and right at the lip of the existing fender.

I think you forgot to divide by two - half the extra diameter of the 13" tire will be above the top of the current 12" tire, but half will be below the axle, increasing the ride height of your trailer.

[les45]

I think you forgot to divide by two - half the extra diameter of the 13" tire will be above the top of the current 12" tire, but half will be below the axle, increasing the ride height of your trailer.

By golly, you are right. I'm sure glad there is a mathematician on the Forum. I had forgotten the fact that the axle will be raised by half the difference in height. I just might be able to fit the 13's under the existing fenders without moving them. I'll still have to modify them to make them longer and wider to cover the new footprint but that's just part of the never ending work on a TD.
Thanks,
Larry S.

[LarryJ]

I bet if you tacked a stiff piece of rubber off the back of your existing fender - extending it a few inches - you wouldn't have to change a thing.

[les45]

I bet if you tacked a stiff piece of rubber off the back of your existing fender - extending it a few inches - you wouldn't have to change a thing.

If you have followed my journal and other posts, you would know that I have a bit of OCD when it comes to how things look. I also tend to overbuild. Form is as important as function to me. When I finally figure out which tire and wheel combination to use, I will totally cover the old metal fender with enough wood to extend out beyond the footprint of the tire in both directions. I will fill all the joints and sand and prime it until it looks like one piece. Also, I will waterproof the wood just like I did my main cabin and paint it black. But that's just me.

[les45]

Finally completed my tire upgrade and fender modifications on the "Super Bee". I went to 175-70R13 General passenger car tires and kept the white spoker look with the wheels. Bought the tires on Amazon.com and the wheels on Ebay (none of my local stores had tires or wheels in the size I needed). I wanted to keep the flat fender theme to match the weekender lines so I simply took the old HF fenders that I was already using (see pic in my original post above) and covered them with 3/4" plywood on top surfaces and 1X3 on the outsides. Filled all the cracks with epoxy and then covered all exposed surfaces with fiberglass cloth and three coats of Aeromarine layup epoxy. Then primered and spray painted with Rustoleum gloss black. I ended up raising the fenders about 3/4" to clear the trim board that covers the edge of the floor deck plywood. That allowed me to use one continuous piece of trim board for the full length instead of two shorter pieces. At first glance, you can't really tell a lot of difference, but the new tires ride so much smoother than the old ones. I think this is mostly due to the lower tire pressures (35 psi). Also a little relief not having to worry about the original Chinese tires that came with the trailer. I did keep them for spares.

[TPMcGinty]

Looks great! At first I didn't like your idea of getting white spoke rims, but they look REALLY good on your trailer.

[les45]

Looks great! At first I didn't like your idea of getting white spoke rims, but they look REALLY good on your trailer.

I know that some people have concern over them rusting, but they will be kept in the garage and cleaned and waxed regularly. I like the spoker wheel look with the Super Bee theme. I used to use these on all my pickups back in the good old days. I do think that the conventional rounded teardrops look better with even larger tires and some sort of alloy wheel or hubcap look.

[TPMcGinty]

I know that some people have concern over them rusting, but they will be kept in the garage and cleaned and waxed regularly. I like the spoker wheel look with the Super Bee theme. I used to use these on all my pickups back in the good old days. I do think that the conventional rounded teardrops look better with even larger tires and some sort of alloy wheel or hubcap look.

If they rust later you can always have them powder coated.

[Oldragbaggers]

Looks great. You came up with a very nice solution.