the rain bike i`m making up has 27" wheels , old shimano 105 hubs & narrow alloy rims:
Q1: no thin 27" tubes with presta valves avl. here , 700 tubes should be OK **********.

Q2:the old 105 hubs have a lube. drilling in the centre with a sliding cover.is this for oil or grease ???
thanks

Greywolf, don't use 700 cm tubes on a 27" wheel. The tube will fold inside the tire causing uneven inflation and unbalancing of your wheel. Keep looking for 27" with prestas.

Post what you need in the "Wanted" part of Bikeforums.com. Go to oldroads.com and post a "wanted" in the classic lightweigts topic threads. Since you are in New Zealand, the shipping might cost you a bit, but a couple of tubes will last you a long time.

Presta valves on 27" are a bit unusual in the USA, but not uncommon elsewhere.

Have you called around to the older established bike shops in New Zeland and maybe Austrialia? Talk to the old timers. Somebody must have what you need.

700c and 27" can use the same tubes. In fact, many tubes say this in the sizing specs.

There are others more experienced who can confirm this, but I am pretty sure that fitting is for grease. The idea is that you stick a grease gun on that fitting and pump grease in, squishing water, dirt and old grease out of the bearings, replacing with the fresh, clean grease.

FWIW, there is not a lot of difference between 27 and 700c wheels. 27" rims are 630 mm in diameter, 700c are 622 mm. This means that you only need to be able to lower the brake pads 4 mm to be able to use a 700c wheels. Most older brakes had plenty of adjustment available.
Regards,
Raymond

actually,700 C is a bit smaller than 27". The 700c has to stretch a bit.they are often used interchangably and are marked as such. If the 27" rims were drilled for shrader valves,get the gromtet type adapter to use with 700c prestas if you go that way. The hole in the hub is a grease port.but hubs should be taken apart periodically and bearings cleaned and serviced anyway.

Actually, I am pretty sure the "port" on the hub is an OIL port.

Garden variety bike grease is just oil and soap. The oil provides the lubrication, the soap makes it stay around. Soap, though, can absorb water, which can cause problems in bearings. Waterproof greases are different. In either case, grease takes force to flow very far and get pushed into small spaces, like between ball bearings.

Years ago (well, 30 years ago, when I got out of the Army and into bike riding and probably way before that) Campy was making it's racing hubs with oil holes -- p[robably long before that, too.

You have to oil more frequently (like weekly), more often if rainy, compared to rebuilding the hub with grease, but oil will flush out the bearings so you should be able to go longer between rebuilds, if you re-oil frequently. If you wanted, you could ignore the oil hole and grease them as with any hub without an oil hole.

Trying to force grease into the hole in the hub would not accomplish much unless it has a "zeek" fitting where you would use a grease gun to force grease into the hub and _through_ the bearings under pressure. Otherwise, the grease really won't go anywhere except into the voids around the axle.

So, you can grease the bearings, as most people with rebuildable bearings do, or clean them out and convert to oiling them every few days through the hole.

A couple people I knew in my early cycling days would convert their non-Campy hubs to use oil bu drilling an appropriate hole and buying a Campy (or other?) spring clip that would go around the hub and plug the oil hole against contamination.

Yes, that is definitely an oil fitting.

One can probably reduce a wheel bearing's rolling friction somewhat by using oil instead of grease, but, as the others observe, it is a maintenance headache.