How does 3” rubber fernco cap protect airbag?

[Wmoater]

I was about to install my new airbag. Mine is totally shot with holes in bottom between the frame and bag. Shock is out, new brass elbow ontop of airbag. New 1/4 line and new brass coupler to fit into manifold. I was told since I live on gravel road and travel a lot of tarchip roads to put a 3” fernco cap under the airbag and buy a new bolt too. Am I missing something? The interior diameter of the 3 inch rubber fernco cap is 3.625 but the bottom of the airbag is only 3 inches exterior. Aren’t stones now going to be trapped and then sandwiched sideways now. This fernco is going to create a cup that will collect even more stones. I just double checked and on 4 other threads/ posts on spyderlovers say 3 in fernco rubber caps. What am I missing? Are others for sure using a 3” fernco cap? In order to make this work you’d need a 2.5 inch fernco which doesn’t exist. Can someone clear this up and explain to me how this will protect and not create a cup full of stones along the side of the airbag now and eventually warm under it again?

 

[Peter Aawen]

I dunno about the specific '3.625" ID rubber Fernco cap' that you've got, it sounds to be a bit bigger than those recommended/usually used?? Maybe it's the next size up?? Or possibly it's cos it's 'rubber' and not the Rigid PVC cap that I believe is the one most commonly recommended & used for this purpose here in Oz?? :dontknow:

But for all of these 'protectors' that I've seen here in Oz (all 3 & a tiny bit" ID Rigid PVC plumbing caps ) once the airbag is sitting in and bolted/secured into the upturned cap and the bag's inflated to anything more than about 5 psi, it pretty much fills the cap and there's very little likelihood of any stones or even fine grit getting in there! :shocked: It's a pretty tight fit once there's air in the bag, and when the pressure gets higher &/or load settles onto the air bag, it fills the cap even more tightly & stops ANYTHING from getting in, even water.... and I've seen some air bags with protective caps that've been in use for well over 100,000 kms without anything getting caught in the cap - not even dust! :shocked:

Mind you, I do a fair bit of gravel & dirt road riding, and I personally DON'T have one of these extra 'protective caps' fitted to my RT's air bag, nor do I have a belt guard for that matter, and I've never had any issues. There again, I might not wash & polish the brightwork & tupperware on my Spyder after every little ride (cos it gets washed whenever I ride in the rain anyway ) but I do generally check, inspect, and clean/blow out all the little nooks & crannies as well as the works & fittings underneath at least once every week that it's been ridden; including jacking the Spyder up & blowing out any dust &/or gravel etc that may've collected under the (naked) air bag, so there's not much chance for anything to be in there long enough to cause a problem... But still, wherever I can, I tend to use 'Preventative Maintenance' rather than relying on bolt-on bits or a/mkt added protection, and I'm gonna be down there checking the tire & belt & sprockets & bearings etc anyway, making sure that everything's in good nick & doing what it should be as it should be in preparation for my next outing, so there's no 'extra effort' involved & I KNOW that it's all rarin' to go at the drop of the flag. :thumbup:

Over to you... :cheers:

 

[Wmoater]

Rigid or rubber pvc would not matter. All 3 inch PVC plastic pipe is 3 inches interior. That us universal. The thickness of the pipe (outside diameter plus 3 inches) is 3.625. That’s the same on plastic and or cast piping. There is only 2 inch pipe which is 2.625 for cap/ or coupler or 3 inch pipe which is 3.625 for cap or coupler. Maybe when blown up with 5 psi it expands that 5/8 instantly which I can then see how the airbag would fill the void but just sitting there the gap concerns me. Maybe it does expand outwards that much. I guess that’s what I’d like confirmed.

 

[chipveres]

Perhaps you could pre-fill the gap with 3M 4200 or similar?

 

[DGoebel]

When the cap (or air bag cup) is installed in the bike with the air bag and bike's weight on it, the bottom of the bag seals the inner opening of the cup and blocks stones etc from getting under the cup. My '13 RTL had one of the original Roadster Renovations' Air Ryde Rock Armor air bag cups installed and never got a leak, I also added the "Missing Belt Guard" as I rode lots of MN to FLA gravel roads.

 

[larryd]

I have a new cap and a used air bag in the garage...I think I still have your number...Pictures on there way...larryd

 

[IdahoMtnSpyder]

You will find all the info you need in these two threads. Two items to be aware of. Doc's instructions are still on the 'net. The link in the post is good. Second, be sure to get the Fernco cap for Drain, Waste, & Vent PVC pipe, NOT for pressure PVC pipe which is usually schedule 40. They are not the same size. The air bag seals up tight to the Fernco cap by its expansion when it is aired up. The bag has to be deflated to fit into the cap.

https://www.spyderlovers.com/forums...phrey-s-Air-Ryde-Rock-Guard&highlight=air+bag

https://www.spyderlovers.com/forums...Air-Ryde-Rock-Armour-Part-1&highlight=air+bag

 

[IdahoMtnSpyder]

Perhaps you could pre-fill the gap with 3M 4200 or similar?

No need to do that.

 

[IdahoMtnSpyder]

Rigid or rubber pvc would not matter. All 3 inch PVC plastic pipe is 3 inches interior. That us universal. The thickness of the pipe (outside diameter plus 3 inches) is 3.625. That’s the same on plastic and or cast piping. There is only 2 inch pipe which is 2.625 for cap/ or coupler or 3 inch pipe which is 3.625 for cap or coupler. Maybe when blown up with 5 psi it expands that 5/8 instantly which I can then see how the airbag would fill the void but just sitting there the gap concerns me. Maybe it does expand outwards that much. I guess that’s what I’d like confirmed.

Uh, you better check that. For each nominal diameter pressure pipe is same OD regardless of wall thickness. DWV pipe is NOT the same size as pressure pipe. Schedule PVC pressure pipe is the same OD as Schedule steel pipe. And no Schedule pipe ID is the same as the nominal pipe size.

 

[Bfromla]

opcorn::hun::dontknow::dontknow: in theory anyway:thumbup:

 

[Bensonoid]

Here's what a 3 inch fernco looks like installed.