front and rear tire pressure differences

guitarbiker said:

I just got back from x-country mountain bike ride with the front tire about 35 psi and rear at about 50 psi. I'm using a 29er with Bontrager Jones ACX tires, (clincher). I felt like I was moving faster than if I pumped to tires to the usual 30 psi front and 30 psi rear.
Just wondering if there are disadvantages to running higher tire pressure in the rear. I felt like I skittered a bit on roots, but the climbs felt easier.
Thanx

Yes, higher tire pressures will lower rolling resistance to a point. However, too high and you actually slow down because of the loss of traction--as you experienced. Too high of a pressure also reduces comfort. The ideal pressure to ride depends on the tire, rider weight, and the riding surface. The smoother the surface, the higher pressure you can get away with.

Thanks for the info. I guess what I was really asking though is about the difference in pressure from front to rear. I've always had the same pressure in both tires on my road and mountain bikes. But I thought that since most of my weight is over the rear wheels it makes sense for it to be more inflated. Auto manufacturers recommend different tire pressure front and rear so..............
Thanks for any thoughts.

Quoted post said:

Auto manufacturers recommend different tire pressure front and rear so.............

........Not always. However, I think at least theoretically you are on to something. The reason some auto mfrs. recommend different pressure is the weight distribution. To really do it right, you need to figure out what percentage of your and the bikes weight is on each tire and then adjust the pressures accordingly. I suspect your current 35/50 settings are too far apart.

i agree, 35/50 is too much spread.

if you had good steering at 35, leave it there; try 45 in the rear, and see if the rear tire hooks back up. if not, go down 1-2psi at a time until it does. pain, i know, but it's part of dialing in the bike to fit you.

i personally can't run 35, even in front -- too mushy for this big guy; i'm closer to 48-50 in front, about 55 rear for dirt, add about 7-10 psi for pavement (i only have one bike, a dakar xlt).