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Dura Ace WH-7801 SL....Help Please!!

Posted: Sun Mar 10, 2013 6:33 pm
by rebilda
A friend of mine dropped her bike around, for me to check over prior to us heading out for a ride next weekend.

The bike has Dura Ace WH-7801 SL wheels on it (Nice wheel set!!) with an asymetrical rear rim. I've not seen this before. There is (obviously) a flat side and an angled side in the profile of the rim extrusion.

My trouble is - the rim 'Looks' like it is fitted the wrong way around!

Can anyone tell me, without any uncertainty, which side of the rim should be on the drive side of the wheel?

Re: Dura Ace WH-7801 SL....Help Please!!

Posted: Sun Mar 10, 2013 7:07 pm
by biker jk
Angled side of the rim on the drive side (right). The spoke holes are offset to the left side of the rim which increases the bracing angle of the drive side spokes and also allows for more even spoke tension between the drive and non-drive side. How could the rim have been installed the wrong way from the factory? Hard to believe.

Re: Dura Ace WH-7801 SL....Help Please!!

Posted: Sun Mar 10, 2013 7:17 pm
by toolonglegs
Very unlikely if it is built the wrong way round... the tyre would probably rub the frame on one side if someone managed to build it up like that.

BTW if anyone reading this has a trashed one of these wheels let me know... I have a brand new rim on a hub with a broken axle ( common fault on the poorly designed hub... well common fault for me that is! )... I am after an old hub.

Re: Dura Ace WH-7801 SL....Help Please!!

Posted: Tue Mar 12, 2013 5:21 pm
by rebilda
Thanks for the feedback.

Just to explain my concern - The bike was dropped off to me to "go over it" before I take a friend of mine out for a ride on the weekend. She hasnt ridden for some time, but prior to her Hiatus, was riding Tri's and has also ridden Track.
She told me that the last time she was riding, she was hit by a car on this bike, and hasnt really ridden since - this was about 2 years ago.

When I was cleaning the bike and checking the components, I innitially saw the asymetrical rear rim and was quite intrigued. Then I noticed that the wheel was sitting over to the drive side (Tyre to frame relationship). This combined with the asymetrical rim immediately got my suspicions up that maybe the wheel had been re-built - back to front.

It is all good however - the rim is built correctly. It is either an alignment issue or a 'dishing' issue - will look closer at this tonight.

Re: Dura Ace WH-7801 SL....Help Please!!

Posted: Thu Mar 14, 2013 5:57 am
by rebilda
The frame is bent :(

Re: Dura Ace WH-7801 SL....Help Please!!

Posted: Thu Mar 14, 2013 11:52 am
by biker jk
rebilda wrote:The frame is bent :(

Surprise, surprise given the bike was struck by a car.

Re: Dura Ace WH-7801 SL....Help Please!!

Posted: Thu Mar 14, 2013 4:48 pm
by rebilda
Actually, I have no evidence that the bike was hit. There is some road rash here & there, and my friend said that "She" was hit by a car. The bike has hit the bitumen, yes, but It would be specuating to say that the frame has been hit, or suffered a huge impact as a result of this. As far as I know, she wasnt hospitalised or anything. I believe she just dropped into her LBS with the instruction to get it ready for a race on the weekend.

In any case I have set the frame up over a centreline and the discrepancy of the dropout positions against the centreline is only about 2mm, to the drive side. I was surprised that it was only 2mm given the issue I have seen in the driveline, but there it is. I innitially had real conserns that there was some issue with the rear wheel. It hadnt occurred to me that there would be any allignment issues with the frame, as it all looks pretty good.

I will re-assemble it, do what I can with the chain line and tell her to enjoy riding it. At worst, the rear wheel will need to be re-dished if she transfers the wheelset to another bike in the future. (I just centred the rim to the chainstays, to get the tyre away from the frame)

Re: Dura Ace WH-7801 SL....Help Please!!

Posted: Fri Mar 15, 2013 5:43 pm
by rebilda
Final chapter in this story.

The chain fitted to the bike was a CN-HG53, 9 speed, Shimano Chain (their cheapest line I think). It is pretty similar to one that came on a new mountain bike when I bought it a couple of years ago. That Chain broke, out in the bush.
I removed this abomination of a chain and fitted a used 10 speed 6701 Ultegra chain that I had kept from the last service I did on my road bike (it was worn, but not worn out).

This has made all the difference! The old chain was vibrating about in top gear, because the side of the chain was actually dragging on the next sproket up, on the cassette. The drive line having been shifted across by 2mm was only magnifying the problem. As the 10 speed chain is a little narrower, there was no interference at all. Shifting is now smooth and reliable.

My friend came over this afternoon and picked the bike up, so we went for a short ride to test it out - all good!