Bicycle Mechanics - 120 psi too much for old rims?

I have some new Vittoria tires for an old 27" X 1.25" wheels on a '70's vintage Peugeot PX-10.

These tires can take 120 psi.

Of course, the rims were made when most road clincher tires were around 90 psi.

Is it likely that the 120 psi tires will put too much pressure on these rims?

Mike, years ago i put ~150lbs into a mtn bike tire for a skidding contest, the tire blew after a 500+ foot skid, i still have the rim, and have not noticed any problems. This was on a cheap LX rim, i dont know if the rim itself has a PSI rating.

I guess that didnt really answer your question, i personaly wouldnt trust an older rim with a too high of a PSI, however I think most rims would beable to hold well over 120psi.

Originally posted by Joe Gardner
Mike, years ago i put ~150lbs into a mtn bike tire for a skidding contest, the tire blew after a 500+ foot skid, i still have the rim, and have not noticed any problems. This was on a cheap LX rim, i dont know if the rim itself has a PSI rating.

Joe, that story ROCKS, Man!

If it is a hook-bead style rim, rather than staight-walled, it may be able to sustain the higher pressure. Most of today's tyres require a hook-bead setup, which is one key to their high pressure capability.

Originally posted by John E
If it is a hook-bead style rim, rather than staight-walled, it may be able to sustain the higher pressure. Most of today's tyres require a hook-bead setup, which is one key to their high pressure capability.

I suppose I should know this, John, but what do you mean by hook-bead style rim?

Put on some industrial safety goggles and leather gardening gloves, and proof test your new tire/rim at 150psi.
If it can survive that without rim failure, you should be OK.

Many modern rims can fail if the braking surface is too worn.

If they aren't super-lightweight rims, and aren't badly worn, I would expect they could handle the additonal psi. One caveat, make sure the rim tape is up to the challenge.

Originally posted by roadbuzz
If they aren't super-lightweight rims, and aren't badly worn, I would expect they could handle the additonal psi. One caveat, make sure the rim tape is up to the challenge.

Good point about the rim tape! I forgot about that. I better replace the old worn stuff with better rim tape.

Originally posted by John E
If it is a hook-bead style rim, rather than staight-walled, it may be able to sustain the higher pressure. Most of today's tyres require a hook-bead setup, which is one key to their high pressure capability.

Once again, JohnE was spot on with his advice.

I learned not only from John's advice and two other bicycle sages, but also from the experience of EXPLODING:eek: two new tubes in the process of learning.

Before about 1973, some/many bikes had rims with a smooth inner wall. No matter what tire you put on these, the maximum pressure the rim will allow is about 70 psi. More than that and the tube lifts the tire off the rim an KABLAM! it explodes with a tremendous blast.

After 1973 many/most rims had an inner flange that would hold the tire bead onto the rim even with high pressures.

Since most people on this forum don't ride older bikes (what a shame), this may be mute, but it is good information for reference anyway.

Well, you and John E know more about this than I do, at this point, but that never stopped me from throwing in my $0.02 before! My experience is with a newer rim, ca. '92, that didn't have a hook bead, so take it with a grain of salt...

If you're willing to live dangerous, and carry a couple of spare tubes since "blow-offs" can't be repaired... some tires will probably work. I don't know about your Vittorias, but you can rule out any foldables/kevlar beads... the bead will stretch. And there's no guarantee that all steel beaded tires will work. Find one that's hard to mount (and send me the Vittorias ;)).

Good luck!

Roadbuzz, the tires I mounted had wire beads and they still blew off. One thing I should point out is that I had coated the tires with soap water to make them correctly when mounting. That probably contributed at least a little to the blow-off.

I like your suggestion, by the way, about checking the rim tape. That was smart thinking.

Even in these days of ISO standards, rim outer diameters and tyre bead inner diameters do vary. Be suspicious of any tyre which mounts too easily onto your rim, or which can be removed without using a tyre lever (unless you can tear a phone book in half -- I definitely cannot). Also, it does not hurt to inspect your tyre sidewalls periodically; look for deterioration as well as for traces of bead showing above the rim wall. Finally, make sure your tyre width is compatible with your rim width (see Sheldon's chart, which is perhaps a bit too conservative).

Originally posted by John E
(unless you can tear a phone book in half -- I definitely cannot).

John, since you have given me such great tips over the years, I will give one to you:

How to tear a phone book in half (and impress your friends):

Put a nice, thick phone book in the oven on very low heat (bread dough raising temperatur) for about an hour. The idea is to dry out the phone book.

Let the phone book cool.

When you go to tear the phone book in half, grip the spine (binding) of the book. Snap the binding quickly and tear the book in half.

It works. It looks cool. You can get chicks at parties with this trick (and two pints of rum).