Blow outs and gear shifting.

Buttie

Afternoon all,
Two questions for the techies out there.

First off, the bike - Cube Hooper (Alfine 11-spd), Schwalbe Marathon Plus 700 x 28mm tyres. (80psi)

Blow-outs.
Last Thursday commuted as usual, got home no problems. Saturday morning went out to rub beast down with a oily rag to find the front tyre off the rim on one side of wheel by 150mm or so. Shock-horror.
Removed tyre to find small tear and 50mm split in tube, and in same region two areas (each about 75mm) of damage to tyre beads, the rubber covering over bead was hanging off.
Now I am not a complete novice and have changed many tyres and tubes with no problems, but the only explanation I can think of is that a) I pinched the tube and at the same time b) damaged the beads in the effort of getting these rather stiff tyres onto the rim. Bad day that must have been.

Ok put my hands up, but what I really would like opinions on is the whole issue of a popping tube blowing the tyre off of the rim, at rest in my garage. Is it possible, does it happen?


Second question about Alfine hub.
After fixing above tyre issue gave the bike an extra dose of TLC when I noticed that for an 11-spd hub there are only 8 'clicks' between indicated 1st and 11th speed on changer and the physical limits of the hub changer, i.e. with the cable detached at the hub plate there is no more positional movement either way up or down than with cable attached. Yellow markings line up perfectly in 6th.

I know the Alfine changer has a 1 or 2 gear changing option but have been very careful to ensure only 1 selected up or down. Does this mean I have been using only 9 speeds or have I got hold of the wrong end of a large and stupid stick?

Cheers for any thoughts,
Buttie.

supersonic

Yep, I've seen tyres seemingly blow out for no reason when unnatended! One reason is temperature change and a present weakness.

I am not too familiar with the Alfine shifter, but there should be 10 distinct clicks for the 11 positions. If you completely remove the cable, how many clicks at the shifter now?

Buttie

Like your diagnostic logic Supersonic re removing the cable, so I just have - 8 'clicks' only up and down.

I am going to have to delve deeper with this as I am finding it an annoying itch. Over the year I have had the bike I have noticed that there appeared to be a mis-match between the number of times I changed gear and how quickly I went through the gear range, I seldom seem, if ever now I think about it, to be in the physical gear ratio the clicks would lead me to believe I should be in, I seem to get through them with less clicks than expected. I have put this down to either me just not getting it right or some aspect of the Alfine operation that I am not aware of, rather than a mechanical fault with the hub.

I'll keep you posted.
Buttie.

cycletech

Hi Buttie

How are you fitting your tyres?

The tube can get pinched between tyre and rim! Also make sure rim tape is fitted correctly.

keef66

A tube cannot explode inside a properly seated intact tyre. For the tube to explode either the tyre must suffer a structural failure like a cut, or become unseated from the rim.

From your description I suspect the latter. The damage to the beads probably happened when you were riding as the tyre was not properly seated.