Rear tire feels unstable in turns

[gstam4]

hey all - seems my leaking-gas and other mechanical problems have been fixed, so i'm moving on to the next one on my list.

i have tires with plenty of tread, and the air pressure is good. they're a little on the old side (mid to late 2008), but don't show any signs of rot. if i decide to keep the bike past the summer, then i'll probably replace them.

when i take a turn with even moderate speed and lean the bike a little (i mean really a little - even if i'm doing a right-hand turn onto another street at 10 mph), the back end/tire feels 'unstable' - as though it's sliding, even though i know it's not. it's hurt my confidence in turns, because i'm worried the bike will slide out from under me. i don't have any stability problems riding in a straight line, other than getting blown all over the place by the wind.

assuming my tires have proper pressure and aren't themselves the problem, anyone know what it might be? i saw 'trail number' mentioned online somewhere, but not in relation to a gz.

[Water Warrior 2]

Trail numbers refer to front end geometry. You may have a faulty tire pressure gauge and are actually on the low side of the recommended PSI. I would however plan on new tires soon. After 5 years the rubber is harder and slippery even on the best surfaces. Be really careful during a rainy day.
A hint for better tire mileage is to run with 2-up pressures all the time. The handling will not suffer and there is slightly less rolling resistance from the rear tire.

[jonathan180iq]

I agree with this. I had a very similar feel and could not figure out what was going on until I got brave in a turn and just leaned out and over to see what the hell was going on. Turns out that despite what I thought, my air pressure was not accurate and my front tire was giving in turns. Have someone watch you or record yourself on video if you have to. (just find a cul-de-sac or something) All of your descriptions sound like air pressure. Even a hardened older tire won't give like that unless the road is wet or glassed from heat.

[gstam4]

thanks guys, i'll check with a gauge (instead of eye-balling and feeling with my hand) and see if that helps.

as far as buying tires, how do people do it? i think i remember reading on here that it's hard to find a matching set? any brand recommendations?

[jonathan180iq]

Whoa.

Definitely use a gauge. You can be off by double digits with the old hand test and not ever know it. Once loaded with your body weight, the way a tire feels is going to be very different from what you feel with your hand on the tire and no weight on the bike.

My issue was a faulty schrader valve. If that happens to be an issue, then I have a poor-man's method for swapping those out too.

[gstam4]

so, uh, apparently the front tire was at 44 psi, and the rear at 42. the bike is sitting in the 90-degree sun, but hasn't been ridden for about 2 hours. i tested my car's tires using the same gauge, and they were at about 33 psi, where they should be.

this is how the dealer (from whom i bought the bike, and who has had it back numerous times for repair, including about 2-3 weeks ago) inflated the tires for me. i haven't touched them myself.

bad?

update: i dropped both tires down to about 33-34 psi and rode around a bit. maybe it feels a little better, but i think i still feel at least some of the instability. time for new tires, or is there anything else it could be?

the tires themselves really look great. no center wear, etc.

[Water Warrior 2]

Ideally you should check the tires cold(unridden)in the morning and before the sun warms them.

[Cathy]

Qasual - Replace your tires, they're passed the lifespan of the average tire (4-5 years) also the tire pressure should be 28psi front and 30 rear (32 is two-up).

I'll take a picture real quick of the sticker. I may be off by 1 psi or two, nothing to worry though.

[gz4me +]

My sticker on bike and the manual says: Solo Riding- 25psi front 29psi Rear. Dual Riding 25psi front 33psi Rear. Hope this helps.

[gstam4]

thanks again.

trying to figure out what tires to buy to replace them, i just saw that while my rear is a 130/90-15 (which seems right), the front is a 120/80-16 (whereas the book says it should be a 110/90-16). is that a problem? can i buy either size as a replacement?