7 flats in 7 weeks
 

It's been a long time since I've posted and I didn't want to start out this way but here it goes.
7 weeks ago I purchased a Motobecane Cafe Latte to replace a worn out Motobecane Elite FS. The Cafe Latte is a great bike except for the fact that I have now had 7 flats in 7 weeks since I bought the bike new. All on the rear. First thought it was the tires so I replaced the tires with a wider (31?) cyclocross tire after the second flat. Still had 2 more flats.Next thought it was a bad rim (Alex rim R500) so that was replaced, at no cost to me. Put liners in the tire, still having flats. Realized finally that they are pinch punctures on the side of the tube.so I took the liners out, still having flats. Recommended PSI is 35-70 and I check every time before I leave home using a digital gauge. I also check whenever I make a stop and get off the bike (coffee shop, bookstore, shopping, etc) using my ultra portable M1A1 highly calibrated thumb. I can feel it when the tire goes down and it happens mostly when I'm going around a corner. But not always, the last flat was in the side of the tube next to the rim. With myself and what I carry on the rack, figuring 70% of the weight is on the rear wheel, that rear is carrying no more than 200 lbs. Help! What the hey is going on. I'm averaging 1 flat a week. My Elite FS had 3 flats in 4 years. This has gotten to the point that I can't rely on the bike. Frustrating not only for me but the guys at the bike shop as well.:notamused:

the pressure recommendations aside, what are you actually inflating the tubes to?

70 PSI, check with a digital gauge.

check your rim tape.

then double check that you indeed have a new rim. if the LBS said they replaced it, they could have been mistaken.

according to your post you have eliminated all the obvious things, so more than likely it's going to turn out to be REALY bad luck or something off the wall.

Not the rim tape. It now appears the the punctures are occurring at different places. They have been on the side, next to the tire and next to the rim. The rim tape was removed and plastic electrical tape was put on. Still the problem persists.

Guessing you weight about 230 lbs and use 700 X 28 tires.
Your pinched flats sound like low psi.

I run 100 psi in my 700 X 28 tires.

Whenever I see someone having recurring flats not obviously caused by road hazards, I suspect it's related to the mounting procedure. With today's narrow rims it's really easy to get rim-side tears in the tubes.

There are two likely causes.

1- tube trapped under bead and damaged or torn when inflated. Usually this manifests within the first hour or so.

2- tube hyperstrethed in one area. To understand this, look at the cross section sketch here. (scroll down to it)

You'll see that the inflated tube isn't round, but has a bulge filling the rim below the gap between the beads (above in sketch, which is upside down to how I look at things). What happens is that the tire first inflates round until it fills the tire, then the section laying across the gap stretches more as it bulges into the rim. On narrow rims the problem is more serious because the gap between the beads is very narrow, so a small section has to expand 3-4 times to fill the rim.

There's no easy fix, except to get stretchier tubes (if they can be had) or at least better quality ones. But start with the largest tube rated to fit within the tire, ie a 28-32mm tube for a 28mm tire. This will need to stretch less as it fills the tire, leaving more capacity to blow down into the rim without tearing.

Cheap Bikes Direct OEM tires. I'd replace them with some nice tires from your LBS. BD gets weird tires from legit manufactures that aren't to spec. My buddy's Outcast came with cheap Kenda Nevgals, smaller and heavier than the ones I bought from my LBS. Rode like crap, ended up throwing them away.

OP mentions aftermarket CX tire installed then 5 more flats occured. Failed to mention brand/model though.

I think I'm with FBinNY's option #1 - damaged upon install or trapped under bead on install.

I've had issues with the Forte brand tubes from Performance Bicycle. They will develop holes in them with the bike hanging on the wall. I can go on several rides totalling 50-150 miles without a problem, then after hanging on the wall for a week, the tube will suddenly spring a hole. Other times it occurs while riding. Holes so far have been next to the rim or on the side. I suppose it could be improper installation, as mentioned above, but I'm pretty careful about seating the tire and haven't had the problem with better tubes, so far.

PJones, Anytime I read/hear about multiple flats with punctures near the rim I think of improper installation technique and/or improper inflation. You may simply need the rear tire inflated to a higher pressure. You can experiment with the present tire or buy a set of touring tires rated for higher pressure.

There are video articles on youtube that can show tube and tire installation techniques.

Brad