308 Tire Stem Mounting question

Rob
I think you've been given good advice by the Permatex guy. Also, I don't think any part of the rubber will come into contact with the sealant. Usually when it tacks up, it stays put.

By the way, I have two sets of three piece wheels. One set (BBS) has had to be pulled down and resealed a couple of times a year over the last couple of years. The other set has a thick band of sealant filling the void where the two rim halves meet the center. No issues with maintaining pressure. Given I change tires a couple of times a year I wouldn't see any degradation of the rubber from a reaction with the sealant but I'd be amazed if this was an issue.

Good luck
Philip

 

Hello,
Anyone have experience using the std Ferrari 308 valve stems w/Superformance wheels?

Last night I installed the std Ferrari valve stems on my new Superformance wheels. The o-ring on the inner flange seemed to seat well on the wheels after I removed some burrs from the openings. I found the burrs by touch before trying to install the stems, so no chance the o-rings were damaged. I used a thin layer of Loctite 515 to ensure a good seal, & tightened them until the rear flange was firmly in contact with the inside of the wheel's stem opening.


BTW, the inside of the stem openings was not machined, but did seem to be flat enough so that the stem would seal.

Just got a phone call from my son at the shop installing the tires. He can't get the stems to stop leaking on the 1st 2 wheels. He tried loosening & re-tightening the outer nuts on the stems. They still leaked noticably after being tightened as much as he dared torque them down.

I asked them to hold off until I got some help from FChat.

 

Hi Verell,

What stems are you using?

Regards,

Carl.

 

As I posted earlier, they're the std Ferrari stems, all metal.

Stem is threaded with a flange on the back that holds an o-ring to seal against the inside of the rim around the hole. A long nut with a small washer threads over the stem to clamp the outside of the hole.

Best Idea I've come up is to get a rubber fender washer about the diameter of the flange & punch a larger hole that the stem just fits thru.

Would like to know if this is a general problem with the Superformance rims tho.

I'm sure a conventional all rubber stem would work, but paid $50 for the Ferrari stems from TRutlands, so would really like to use them.

 

there are several stem sizes to match the rim holes such as 0.453", 0.625", 9.7mm, and you do not use sealant on those types of stems. They are designed to seal just by the jam nuts. Sometimes the stems have a plastic gromet that spaces the for 0.453 or 0.625 holes. If the rim hole is thinner than the plastic spacer you will not get a good seal.

 

Robert,
Tnx for the pic. That's the same type stem I've got.

Had thought of a thicker o-ring, Monday will see if I can find some.
Plan B: Picked up some neoprene fender washers at the local hw store. If I can't come up with an o-ring, will punch a larger hole in them to fit the stem. In conjunction with the original o-ring they should do the job.

The sealing surface seemed to be quite smooth once I scraped the burrs off. Haven't had time to get to the shop to see if I can spot anything. I think there may be a slight curve on one side of the sealing surface. Maybe just slightly more than the std o-ring can handle.

 

Just got a call from my son, he rummaged around this AM & found some thicker o-rings that sealed up just fine.

My impression was that the original o-rings had less surface exposed than Robert's picture. They only had about 10% of their cross section extending above the flange. Not much margin for complying with a mating surface. That's why I used sealant the first try, to handle the case where pressure on the o-ring wasn't sufficient for a good seal.

 

Finally got my new wheels installed last night!

Funny thing with the wheels, on the driver's side, 3 of the wheel bolts were about 0.5mm too long. They jammed in against the rear bearing mount.

Luckily I always turn the wheels by hand to make sure they turn smoothly before torqueing the bolts down. Was surprised when this wheel was solidly locked up!

Had to chuck them into my lathe & trim them down. The ones that were too long measured ~62.5 to ~63mm. Took ~1.5mm of their ends & all is fine. Probably 1mm would have been sufficient.