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Continental tire keeps blowing off rim...help, please!!(6 posts)

Continental tire keeps blowing off rim...help, please!!DT
Sep 21, 2002 2:58 AM
I recently purchased a pair of Grand Prix 4-Seasons, size 700x23. I put them on a set of '99 Rolf Vector Pro rims, pumped them up to about 115psi, then had to wait almost a week before I could ride. Then, over two days, I rode 50 miles on them. All of a sudden, going downhill around a corner at about 30mph, I blew the front tube...the tire came off the rim, and I managed to keep my bike under control and came to a stop. Upon inspecting my wheel, the tube split length-wise, indicating the tire blew off the rim. My rim is now shot, as the lip of it folded over and cracked about 2 inches in length. After walking home, I tried to put the tire on an old Sun rim, the only spare I had. After pumping it up to the same psi (115), I noticed a bulge where it didn't look like it seated correctly, whereupon it blew again. I tried another tube. This time, I closely examined the rim tape to see if it was covering the lip of the rim up at all...it wasn't. I put the tire back on, pumped it up to about 40psi, rolled the tire around to help seat the lip, then pumped it up again to 115. I took the pump off the tire, and noticed a slight bulge again, then it blew for the third time. What is going on? I know it's not the rims...it can't be the tire, either, since continental tires are used so widely. I'm now very timid at the thought of doing my normal ride where I hit 50mph downhill...I'd hate to have another blowout at that speed! Thanks for your help.
I have only had a Conti blowoff...Lone Gunman
Sep 21, 2002 4:51 AM
of a rim once and strangely enough it was a Rolf Vector Comp rim and it was a new GP3000. You might try scrubbing the tire down with a degreaser as well as your rim and putting some baby powder on it to dry up any residue. There is a slippery slimy substance on the tires that seems to aid in getting the tire onto the rim but once on seems to aid in it coming off or it could be you have a defective tire.
I had the same problemAndy
Sep 21, 2002 6:24 AM
I had this problem with the GP3000's and Axial Pro's on my 2000 Rolf Vector Pro rims. The only way I could solve it was to inflate the tires to 105 psi and leave it at that. I'm not sure about the tire bead material but it may be that once the tire blows off a few times the bead becomes a little stretched (not sure). I know that when I first put my tire on it was a tight fit. After it blew off a few times I could easily put it on by hand without straining my fingers.

I am convinced the problem is the Rolf Vector Pro rims. I had two bike mechanics look at it and they both noticed the uneven machining on the inside of the rim where the bead is held in to place.

I have eliminated my problem by using a lower pressure but I'm not happy about it. I'm not rich and I can't afford to by a new set of wheels (just bought a house). So... in my case it came down to spending $500 - $800 for another set of wheels or inflating to 105 psi instead of 115 psi, I chose the latter.

FYI, I'm now using the Grand Prix 4-Seasons myself... at 105 psi. I can never again mount ANY tire on those "Pro" rims at full pressure with confidence.

I would try mounting a brand new tire on your Sun rim and see if it blows off. I was lucky that my tire never blew off at speed. Most of the time they blew off just after I pumped them up and was ready to ride - or they blew off while they were standing still while exposed to direct sunlight. Must have heated up and increased the pressure enough to cause the blowout. This spring I'm getting rid of the Rolfs.
I forgot to mention . . .Andy
Sep 21, 2002 6:30 AM
My problem started with brand new Michelin Axial Pro tires. I then tried a brand new Continental Grand Prix 3000 with the same results. So... it wasn't the tires.
Oh... one other thing to checkAndy
Sep 21, 2002 10:22 AM
Note the location of the bulge in the tire before it blows and mark it with chalk or something similar. Remount the tire so the marked area is on the opposite side of the rim. Inflate the tire again and see if the bulge is always in the same spot on the tire or if it is always on the same spot on the rim.

My problem was always at the same spot on the rim opposite the valve stem hole.
Go to...270bullet
Sep 21, 2002 4:34 PM
The conti gator skin. I had problems with the GP 3000 side wall rupturing or cutting on just about every 4th or 5th ride. The worst was on a descent at about 40 mph. The rear tire sidewall blew. I had them inflated to the max 120 psi like I always do. I still count my blessings for not going down.

I bought the Conti Gator Skins, inflate them to 120 psi every ride. I've not had a flat in about a year now. I ride about 100 - 150 miles a week.