Stan Bradbury's Speedway Training Notes
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Very low pressures are used:
- FRONTS 2 to 1O PSIG
- REARS 8 to 22 PSIG or higher.
Bicycle 26" X 2" tubes will stand up quite well in the 23" front tire if you are unable to get the proper tubes.
If your rear tire walls shred inside, due to low pressures, an old inner tube can be slit around the inside and wrapped around your good tube to protect it.
Caution should be exercised when running tires at low pressures and such things as the weight of the rider plus the smoothness of the track must be considered.
The danger is that if the tire is too soft, it will be forced away from the rim as the rider goes through the turns and the rider may suddenly loose control as the rear wheel rim rides out of the tire and onto the track. Not only that, but forcing the tire away from the rim could result in the tube suddenly going flat due to being subjected to excessive abrasion which is not only dangerous, but also costly.
Security bolts can be used on both front and rear wheels or, the rear tube valve can come out through the tire wall instead of the rim. Tubes with cranked valves were available for this purpose or a regular tube can be twisted with no ill effects, so long as you put a locknut aid a washer on the inside as well as the outside of the tire wall. This enables you to adjust the valve stem so there is just enough protruding through the wall for you to attach an air hose. If you leave it longer, it will hit the rear stays or rear mudguard. When you reverse the tire to use the unworn portion of the tread, always plug the hole in the tire wall where you have removed the "through-the-wall" type valve. Two or three, layers of duct tape will do in a pinch. You must have the valve exit again on the outside (right) side of the tire so it is necessary to cut a fresh hole in the tire wall. If you do not plug the old hole, air pressure will force the tube partly through the hole and cause the tire to burst or chafe and leak air.
Some new tires are difficult to force out of the well of the rim to run true, when being installed. An easy way around this is to coat the bead of the tire with soapy water or hand cleaning material and then put extra pressure in the tire to get it to "pop-out." Up to 65 PSI seems to be okay, then let the tire back down to, a normal pressure.
Some riders secure their rear tires to the rim by putting a sheet metal self-tapping screw through the edge of the rim into the bead of the tires. A system which seems very reliable. Whichever method you choose, it is vital that the tire be securely fastened to the rear wheel rim. Front tire valves often rip out of the tube if you have no security bolt. I leave the locknut off the front tire valve and when I see that the valve has pulled to an angle of approximately 45 degrees, I take out the front wheel and put it back in the other way around. It will then pull straight before gradually going back the other way. New and well inflated front tires hardly move at all, but an old tire may have to be reversed before and during a race meeting.
I've seen some riders cement their front and rear tires to the rim successfully, but I don't trust cement and it can be a nuisance if you want to change a tire or tube in a hurry. The practise of cutting burrs in the wheel rim is a poor one for very low pressure speedway tires, as it can ruin the walls of the tire very quickly.
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