Shimano DuraAce 7850 CL Wheels - health warning!

peter101cycle

Hi, have the 7850 CL wheels (C24 size to be specific) and while they are brilliant, I have found a bit of a design flaw that I thought it was worthwhile sharing.......

If like me, you are using the wheels solely with the bare blue plastic rim tape to protect the innertube from the wheels, here is the word of warning. Somehow, during their use and probably during the changing of tyres / tubes, the plastic rim tape can shift around the wheel very slowly / slightly. If this happens, there is a larger gap around where the plastic rim tape is positionded around the valve hole in the rim, which is exposed (and sharp) aluminium edge.

At the weekend, I had a puncture caused by the base of the innertube valve being cut like a knife on the exposed aluminium valve hole edge. Putting a replacement innertube on the rim without realising the problem, had the same effect - without getting back on the bike, instant punctured innertube again (cue lift from wife at this stage!) :shock:

I was lucky as had just been doing some fast descending on the wheels, could have been nasty if the tyre had deflated at this stage (but thankfully, the puncture is not instant deflation).

So, if you own these wheels, just be careful to check the positioning of the plastic rim tape is correct (it can be shifted around the rim with some pushing with your thumbs) when you change your tyres or innertubes

FransJacques

Wow, I thought the 3rd Japanese reactor blew up from your title.

You must be new to this cycling game because it's commmon knowledge that plastic rim strips move around, especially on the rear wheel and espectially after rain/getting wet.

An issue is that the variation belween spoke hole drilling on the bed of the rim varies widely which is why you need the correct size of rim strip to cover the edges of the holes. Velox solves a lot of problems because they come in many sized from 16mm to 22mm and because they have a sticky back. But eventually they degrade and in some cases rot.

If your rim strip is giving you a lot of problems and you need to ride urgently, packing tape or PVC insulating tape can work in a pinch (do at least 3 wraps) but don't expect it to hold up more than 3/4 rides depending.

Ritchey used to make some nice sticky dacron red tape that came OEM on some Ritchey MTB wheels I had, never seen that stuff again, but it lasted 10 years!

peter101cycle

Na, been cycling for a long time just never used this plastic rim strip stuff (I have obviously been living a sheltered life and never heard of problems with this stuff, honest!).....always used Velox cloth rim tape and never had any problems.

If the plastic rim strips always have this issue (in which case, why do the manufacturers use it?), I will rip it off and use Velox again.

Maybe a daft post of mine but I was quite surprised the stuff could shift as it did seem pretty robust.