project 32"

Sometime in May I built up a new tire to fit in a KH29 frame, freeing up the Triton frame for bigger and badder tires.

The new tire was built out of cheep 27x1-1/4" tires from wallmart. I thought that they had kevlar beads since they were folded up in a little box and said “KEVLAR” on them but the really had a kevlar flat protection belt and some sort of steel cable bead.

I built the tire in a similar fashion to the 24" tire I posted earlier in this thread but no stitching in the casing, only around the beads. I could not go through the beads so had to basically just wrap them tightly together. I glued up the joins (or at least I thought I did), glued down the flaps, wrapped some tape around them and inflated to let the glue set.

There was maybe a 1mm lump at each join from the double layer of re-enforced casing. I don’t think I ever took a picture of it while it was in one piece.

With the new thin tire it wasn’t even 31" so I sort of stopped calling it my 32" wheel and started calling the wheel size 700X*

Anyway the new tire was 32x700 and had 3-4mm clearance with a 2007 KH29 frame. Perfect as far as I am concerned.

I have ridden a 32mm tire before on a 27" wheel and it was pretty rough. It is still a bit rough on the larger wheel but definitely felt smoother. Perhaps we can get a way with skinnier tires on larger wheels.

Anyway I have been using the 700X for commuting off and on, basically when I didn’t have the 36 set up for the road. Played with pressure a bit and really felt that the tire needed more pressure than I use in other tires (duh). I would mostly ride around 80 PSI. Today when I got to work the tire felt a little soft so I went to the air compressor and put some more air in by sound. The big tank usually sits at slightly over 100 PSI so I filled until the air wasn’t really “rushing” anymore. Figured I had just under 100 PSI, the original tires were rated to 90 PSI, figured I should be OK anyway.

Rode the thing home for lunch, then rode back. When I was rounding a corner in the yard I hit a rock that I usually miss, fell off the front and BANG! the bead blew out at one of the joins. The steel cable bead had slipped at the join.

Latter on in the day I happened to look at the pressure gage on the air tank and it was sitting just under 130 PSI, I guess I put a bit more in than I thought. Probably at least 120 PSI.

When I got home I took the tire off the wheel and inspected the damage. I was surprised to find that the casings weren’t glued together on the join where the bead went, and there was no evidence it ever was glued.

I cut the threads that were wrapping the bead and peeled the tread off the join. The Marine Goop I used held the tread on very well and I actually left little bits of rubber behind on the glue.

Looking at the rim I was surprised to see how much stretch 120PSI inflicted in the fibre reinforced packing tape I used for a rim strip. I think I will do a double wrap next time I am using pressures that approach 100PSI.

The other join was still perfect.

I could re-build the tire with the chunk I have left from the original build but I don’t think I want to deal with a cable bead again.

Time to start looking for a nice Kevlar/Aramid bead tire in 32mm width.

*700C is 622mm BCD, 700X is 700mm BCD