digest number 7630

[Devon Jarvis]

Airing down is a common technique to gain traction, used in all sorts of offroad racing, two wheels and four. I have gone as low as 8psi front/10psi rear using Dunlop D606. I used two rimlocks per wheel (this enables you to ride a flat for a great distance if necessary), and had fantastic traction. This increases your odds of a pinch flat, and "millerizing" (badly denting) your rim, but definitely made the bike more controllable. I would then air back up to the max pressures, and ride 100mi home at 75mph. I never had any ill effects, tire life issues etc from doing this. I would not go below say 15psi front/ 18 psi rear without rimlocks though. Too easy to spin the rim and rip the stem out of the tube. The purpose of rimlocks is to enable the use of low tire pressures. While more aggressive tires are sort of a "safe" alternative to airing down, aggressive tires are less safe on the street at ANY pressure. I thought the D606 were the best compromise for offroad and on-road handling. Assuming cost and tire life are not part of the equation. You are wise to be cautious, but riding a KLR650 offroad, you need all the help you can get. Devon

On Sep 27, 2006, at 9:37 PM, DSN_KLR650@yahoogroups.com wrote: > 1c. Re: gravel roads > Posted by: "kestrelfal" kestrelfal@... kestrelfal > Date: Wed Sep 27, 2006 8:10 am (PDT) > > Isn't the "absolute minimum *safe* tire pressure" > in the owners manual listed as: front 21 psi cold, rear 21 psi cold. > > And shouldn't the safe alternative to airing-down be a tires > with a more agressive tread (or slowing down and/or avoiding > conditions where the current tires are not suitable). > > Also, my guess is that rim locks are for racing bikes or racers > and not for airing down (even racing bikes should have a "minimum" > tire pressure ~ higher for racing no less). > > Airing-down might be what people do, but is it inherently unsafe > in that it could lead to possible unseen/internal tire damage and > subsequent failure (like going down the road at 70 mph). > > FWIW > > Fred > Brooklyn '78 SR500 '01 KL250 Super Sherpa