Spare tire mount leaking on back wall by bed

[John_S2]

After driving through some very heavy rains in KY recently we went to bed and I noticed that the head of the bed, which is on the backwall of our Class C was damp. I felt around and the metal plate on the inside wall of our unit was damp and causing the bedding to be wet.

I am in the process of removing the spare tire from the back and the plate that holds it to the Class C. Looks like 4 large bolts go through the wall to the metal plate by the bed.

It looks like clear silicone was used by the manufacturer (Coachman) and it did the job for the past 15 years. Should I just use clear silicone to seal it again. Figure I will caulk around the four bolts as they were caulked originally and also around the outside plate when I reattach it to the outer wall. Any suggestions from any of you more experienced RCv'ers out there? Any and all suggestions are appreciated. TIA

[John_S2]

Thanks for all the ideas and suggestions.

After removing the outside mounting bracket the silicone sealant looked pretty good. I am thinking it may have been just condensation after all.

I resealed everything with some new silicone sealant and think it should be great.

Will wait a couple of days before putting the spare back on to make sure it is well cured.

The plate on the inner wall and carriage bolts seem to be fine with holding the heavy tire.

[gotsmart]

I just used a tape measure on mine. There are no washers on the inside. They appear to be flat headed carriage bolts. Each bolt's head measures 1.5 inches wide. There is no deformation in the (inside) wall that I can see. I have only 2 bolts exposed behind the head of the mattress. The other 2 bolts are below the deck of the bed, in the compartment for the fresh water tank.

[wolfe10]

Yup, recommendations without knowing the extend of the problem probably won't do you much good.

As suggested, verify the problem-- how is the spare tire carrier mounted on the inside. Just fender washers? large backing plates? Are the bolt holes wallowed out? If so can you use larger bolts or do you need to fill and redrill.

The bottom line is that you don't want to just calk, you want to FIX the problem-- whatever it is.

[gotsmart]

Mocoondo wrote:

gotsmart wrote:
(This is me being a Schmar tas)

So I guess that when CA takes a MH that doesn't have a mounted spare, out of the rental fleet, puts it for sale to the public - and then adds a rear-mounted spare for the new owner....

Your vintage vehicle did have a spare back there. 2006 was the last year for the wall mounted spare. 07 was under the vehicle. 08 and newer is in a compartment in rear storage.

hehehe.....:B I was laughing 3 posts ago, when I wrote it.

You have to admit though... nice butt shot!


too funny...no wait...to stupid...no wait...what would Newman say?

[Handbasket]

As heavy as the spare is, I'd look for some other way to mount it. When the weight of that bounces up & down with the rear end on a rough road, it's applying much more force than its static weight indicates. All that force goes thru the bolts; evenly distributed in an ideal world, not likely in the real world.

Jim, "Bills travel thru the mail at twice the speed of checks."

[Mocoondo]

gotsmart wrote:
(This is me being a Schmar tas)

So I guess that when CA takes a MH that doesn't have a mounted spare, out of the rental fleet, puts it for sale to the public - and then adds a rear-mounted spare for the new owner....

Your vintage vehicle did have a spare back there. 2006 was the last year for the wall mounted spare. 07 was under the vehicle. 08 and newer is in a compartment in rear storage.

[gotsmart]

(This is me being a Schmar tas)

So I guess that when CA takes a MH that doesn't have a mounted spare, out of the rental fleet, puts it for sale to the public - and then adds a rear-mounted spare for the new owner.... it's not a good thing?

[j-d]

AMEN to Mocoondo's observations. Unless the manufacturer incorporated some really heavy duty support inside that rear wall (highly doubtful) that 70-80-pound assembly was supported by luan and thin fiberglass. If the bolt holes hogged out, the inner wall is deteriorated.
Our Jayco had a spare tire mount on the square tube bumper, and the motion of the spare cracked the bumper mounting brackets. I took it off and it's stored under the bed.

[Mocoondo]

Unfortunately, this is probably a leak, which is why many manufacturers have abandoned the spare tire on the rear wall concept and went with putting the spare underneath the coach or in a roto-molded compartment in rear storage. Quite a few have abandoned the spare tire all together.

Going down the highway creates forces on the spare tire carrier which ultimately elongates the bolt holes and eventually you get a leak. I would remove the spare tire carrier and investigate whether you have any water damage back there before deciding what to do next. Those that I have seen are usually pretty bad off before any evidence of water inside the coach is present. You certainly would want to repair any water damage as that would only get worse over time. You may want to consider an alternate spare tire mounting location going forward. Mounting on the rear bumper, under the coach, in rear storage or under the master bed are locations far superior to mounting on the rear wall.

[gotsmart]

There is a good chance it is only condensation. Here in WA it rains for 6+ months of the winter. I run a dehumidifier. I have a rear-mounted spare tire and in the winter I have to pull the bed away from the wall about 1/2 inch to let the mounting bolts be exposed to air.

The bolts transfer the cold temperature from outside to the surface of the bolt inside the coach and attract moisture to them. The temperature difference causes condensation to collect on the bolts. Leaving the air gap between the wall and the bed lets the dehumidifier nullify that.

This is only a problem when it is colder outside than it is inside the coach. It's a non-issue during the summer months.

[tatest]

I would seal the margins of the spare tire mount, and the bolt holes (likely place it is leaking) with putty tape. I've had too many bad experiences with silicone sealants, e.g. hold up forever but don't seal, or do stick to one side, not the other, and can't get them off.

[hershey]

After 15 years of use, I'd say that silicone is probably as good a sealant as you can get.
But...it the water is getting inside, then its also getting inside the wall too. I would suggest that you add a piece of plywood, just slightly larger than the hole pattern to reinforce the attachment of the tire. Then silicone the entire surface of the outside and inside mounting area along with the area of the bolts.

[Dusty_R]

It could be condensation and not leaking.

[1492]

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