Cappra Tire Pressures

This seems to be a secret.  There are a number of you that know this secret but there are quite a few that don’t.  I was one that didn’t for a long time. 

I’m a rather large fellow.  I’m talking 250 lbs. plus.  I assumed that I would need a bit more pressure in the tires than were recommended by those that were the more successful racers (read lighter).  I beat myself up for about 25 years.  I built a 1973 VR and proceeded to slip and slide as I had always done and expected the magic of the VR to vault me into a trophy.  It didn’t happen.  No way.  I had been running around 20 to 24 pounds in the front tire and about the same in the rear.  I found myself being passed by better riders that were laying their bike down on the cases in passing me and then disappearing into the dust within a couple of turns.  The straight-a-way speeds were about the same.  It was the cornering speeds I couldn’t attain.  Mud was even worse.  I was slipping, sliding, and falling while being passed by novices racing on trials tires.

Now that I have got your attention, here are the facts.  Montesa provided recommended pressures for there MX bikes.  I started following them.  I found I was hooking up everywhere.  Only my weight was what was keeping me from success.  Well, that wasn’t all.  I’m blind in one eye and a lack of talent fit in there somewhere.

I checked owner’s/parts manuals for VR, 125 MX, 250 GP, LaCross, etc.  On dry and hard ground you put 13 psi in the front tire and 10 psi in the rear.  In muddy conditions and sandy conditions the pressure is 11 psi in the front tire and 8.5 psi in the rear.

There is some additional maintenance that you will have to perform.

Don’t lock the valve stem to the rim with that valve nut.  Snug it up finger tight against the cap.  This allows the tube to slip a little bit and not tear the valve stem causing a flat.

Your tires will creep around the rim.  Usually the rear tire will creep more than the front tire and you will have to adjust this tire more often. 

Add this to your maintenance before each race on the rear tire:

1. Secure the front of the bike.
2. Elevate the motorcycle. 
3. Deflate the rear tire.
4. Loosen the rim locks.
5. Pry the bead off the left side of the tire.
6. Work the tire back where it belongs.  Use of a dilute soapy water solution is helpful.
7. Remount the tire bead.
8. Inflate to about 20 lbs.
9. Tighten rim lock(s).
10. Deflate to 10 psi.

The front tire should have only one rim lock, the rear tire two.  You should figure out how to adjust the front tire on your own. 

If you think that soapy water will just let it slip more easily, it doesn’t.  I’ve tried tire mounting fluids and a mixture of snake oils.  It’s the rim lock that holds the tire, not mounting fluid.

Back to Rocky Mountain Montesa