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What size bit to use to drill valve stem

  • Thread starter Thread starter londongs400
  • Start date Start date
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londongs400

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Hello everyone, after a recent incident I've decided to switch my tires over from currently tube to tubeless (basically have the current punctured tire patched from the inside by a tire shop). I have read numerous posts about drilling out the valve stem hole to accept the bolt type with nuts stem.

I went ahead and purchased this from a local napa in Canada.

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=NTH90416_0215255096

based on info I found in a thread.

My question is what is the common size drill bit I would use to drill our the hole? what size has everyone else used? I have tried searching but can't find the answer so any help would be appreciated. The tires will be going on a 8V 86 GS400S with cast wheels, currently has tubes installed.

Thank you.
 
The ad says:

Tire Valve Rim Hole Size : .453" Or .625"

Do they give you two rubber seals of different sizes?

Or the closest drill you have that the stem will fit through.
 
It's not just reaming out the hole, you need to provide a flat surface on the inside for it to seal against.

I believe the tool necessary is a "flycutter", but a machinist will have to verify that.

.
 
Don't drill the hole -- it's the right size (about 8mm, .315" or so) if you're using the correct motorcycle valve stems. Motorcycle valve stems are the same diameter all the way down. Car valve stems are much larger at the base where they go through the wheel. I can't say I'd recommend drilling larger holes in a GS wheel.

The valve stem you linked to is not the correct one to use on a motorcycle. Note how it gets bigger at the base. This style is for cars or for motorcycles with larger valve stem holes.

Here's one example of the correct valve stems -- you can get these at just about any moto shop: http://www.motorcycle-superstore.com/58583/i/bikemaster-valve-stem

You can also get or order metal motorcycle valve stems at Napa. I don't know the part number, and it's useless to ask the doofs behind the counter. Someone around here should have this info.


I use a 5/8" counterbore with a 5/16" pilot to face the inside of the wheel so that there's a flat place for the seal to seat. It takes only a few seconds with the counterbore mounted in a cordless drill. I got mine from an aviation tool supplier.



 
Last edited:
I have decided to order the proper valve stem which I believe to be 8.3mm. And to have my 2 month old (less than 1000km) tire patched from the inside and run them as tubeless.

My question is if this is safe to do as i currently don't have the funds to purchase a new tire and since they are perfectly fine other than a roofing nail. I should be good I assume. I don't ever go past 130km/h specially never with a passenger (max 90-100 km/h)...

Also what do I seal the actual rim with to make sure no air comes out thru the old mag wheels.
 
Let me put it this way: if you have the slightest doubt whatsoever and you are not experienced in changing motorcycle tires, do not convert tube-type cast alloy rims to tubeless.

A new tube is maybe $15 or $20, and is the easiest, fastest, cheapest, possibly the safest, and undoubtedly the factory correct way to go. In some countries, alterations like this can cause legal trouble, so be aware of that as well.

That said, lots of GS owners have converted to tubeless and are happy with the benefits.

If you still want to convert to tubeless, you normally must machine a flat area on the inside surface of the rim as shown so that the valve stem can seal. If your rim surface happens to be completely flat in that area (most front wheels aren't), you MIGHT get away without it.

You do not need to seal the wheel with anything. Suzuki cast aluminum wheels are not porous. You DO need to make sure the inside of the wheel and the bead sealing surfaces are clean and smooth -- old rubber and corrosion can cause issues with sealing and bead seating.

Another common misconception is that tubeless rims include a ridge on the bead area that helps retain the tire. If you examine the second photo I posted above showing how the counterbore works on a scrap wheel, you'll see that there is no ridge -- that scrap wheel is from a 1982 GS1100GL, and is marked tubeless tire applicable.
 
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