fork vibration on Sherpa

[Danneaux]

i'm not using the CSS rims, just the normal ones.

Okay! That helps a lot; thanks.

the pads i started out with were shimano pads that are fitted as standard on the Sherpa. i changed to a cheap set bought from Asda

I would definitely suggest a change to Kool-Stop Salmon pads as the next step to try. If you're using (or still have) the Shimano pad holders, Kool-Stop make a Salmon cartridge pad insert that slips right into the same holder, replacing the original Shimano pad. Much nicer to carry only the cartridge inserts on-tour, as they require less space in your kit. Given their low rate of wear and how "kind" they are to rims, they will last you a long time, so are a good value for the money.

with regard to the lighter Mavic rim , which is about 100grams lighter than the Rigida Grizzly's , would that make a difference in this case ? in other words, would they be too light a rim for the spokes that came as standard with the bike ?

Yes, I would probably go to a 15ga (1.8mm) spoke with the Mavic instead of the 14ga (2.0mm) spokes used on the Grizzly.

But first, I would have a good talk about your intended use, your own weight, the weight you intend to carry, and the roads you'd be using the bike on. The Mavics would simply build-into a lighter wheel overall, and that is a huge consideration. Those are all things I would want to know before building a set of wheels for someone -- and the same questions I ask myself when building my own.

But wait...there's more!

It doesn't appear possible to do a simple "rim swap", as the ERD (Effective Rim Diameter) of the two rims differs. ERD is "...the rim diameter measured at the nipple seats in the spoke holes, plus the thickness of the two nipple heads. The E.R.D. is needed for calculating the correct spoke length" (ref. Sheldon Brown, http://sheldonbrown.com/gloss_e-f.html ).

According to SJS Cycles ( http://www.sjscycles.co.uk/mavic-xm317-26-%28559%29-mtb-all-mountain-rim-silver-prod10607/ ) the Mavic XM317 has an ERD of 539.5mm (for the rim-brake, non-disc version; SJSC carry only the 32-hole version at present).

SJS Cycles say the Rigida Grizzly has an ERD of 534mm ( http://www.sjscycles.co.uk/rigida-grizzly-26-%28559%29-mtb-rim-black-36-hole-prod18844/ ).

[Please note: The ERDs listed for these two rims vary widely depending on vendor and spoke-calculator listings; be sure to check the ERDs are all for rim-brake versions.]

According to SJSC's listings, the spokes used to build the Rigida wheel would be too short for re-use in the Mavic. The thought of a direct rim-swap may not have crossed your mind, but I thought I'd mention it, since you had rebuilt the Felt wheels reusing the same rims.

Best,

Dan.

[Danneaux]

A possible ready solution to your problem might be here:

http://www.thorncycles.co.uk/forums/index.php?topic=4509.msg21890;boardseen#new

...a 26'' Rigida Grizzly MTB front wheel for sale by a new member in our Forum's Bike Bits/Accessories For Sale board. Handbuilt by Thorn for a Sherpa, minimal mileage, same kind of wheel, but evidently working well for the seller (Disclaimer: I have no interest in the sale).

Best,

Dan.

[bikerwaser]

wow !

thanks for the info Dan.

[bikerwaser]

fork vibration gone now after 2000 miles. it would seem that my initial thought was right about the rims being the issue. after they get ground down the surface becomes smoother. only thing is it was a bit frustrating having to wait 2000 miles until i got rid of it. my only thought now is when i want to replace my front Rigida Grizzly do i go for another one ( because i like the wheel ) and put up with another 2000 miles of "bedding in" or try a different wheel with machined rims?

[Danneaux]

Wonderful news, Warren, glad the vibration is gone! Followups like this are really helpful to others with similar problems; thanks!

As for what next...that's a tough question. I have sometimes seen individual differences between rims when building. You might not have the same extended break-in period the next time around. The Grizzly is a popular rim, and the vibration problem is not widely reported, so you might have gotten a bad example.

It would be interesting to see if swapping brake pads now made a difference. I doubt it would, or would be worth the effort, but it would tell you for sure if the problem was the rim or the pads.

Me? I'd leave it alone now it is working fine! 

Best,

Dan.

[bikerwaser]

HI Dan

changed the pads recently and still no vibration. so it all points to the "bedding in" of the rims.

Bikerwaser

[Danneaux]

changed the pads recently and still no vibration. so it all points to the "bedding in" of the rims.

Oh, this is grand news; wonderful!

I've flagged this topic for future reference in the event others report similar problems. It is a matter that arises from time to time on other bike-related Fora but seldom is there any sort of long-term followup, so it is hard to pinpoint a definitive causality.

In this case <nods> yep! Sure does seem to be a case of the rim bedding in; your initial thought was right indeed. If it helps as an additional data point, the non-CSS Rigida Andra rims on my Nomad now have a darker gray "braking track" where the Kool-Stop salmon pads have been in contact, so some sort of deposition/oxidation is occurring. I can't put it down to any significant rim wear, as the machined ribs are still there to catch my fingernail and I really can't measure any loss of aluminum compared to new. Similar effects have occurred with rims on my other bikes, so yes, "bedding in" sounds like a reasonable explanation.

Thanks for the followup; best wishes for many troublefree rides ahead,

Dan.