More rim questions

[Chris Land]

Ok, after about 6000 miles or so (not really sure but the cyclometer was somewhere around that when the batteries went) I have worn some fairly serious steps into the Sun Rhynos that my Nomad came with and need to replace them.

Question - should I get another set of Rhynos (probably black ones with indicator wear this time), or go for something like the Mavic EX721?  Can anyone compare the relative merits?

One thing I should mention. I have had a problem with squealing brakes on this bike that is a constant source of annoyance.  This recently meant that I ditched my drop-bars and went for some regular v-brakes, thinking that the cause was my avid Shorty-6 brakes.  They still squeal, but not as bad so I am now thinking that the rims might be partly to blame so, unless it is a sacrifice of quality, I am happy to try an alternative.

On the other hand, I have had no wobble on these wheels, despite some off-road touring and very heavily laden touring.  Brake wear is a priority as I tour fully loaded for camping with a kiddy trailer and two-toddlers...  Take ALOT of brake to stop that lot coming down a hill...

[Dave Whittle Thorn Workshop]

I doubt your Sun rims are wearing out after such a short distance, I have NEVER seen a worn out Rhyno and certainly never seen a Rhyno fail.  I wouldn't go for a EX721 as a replacement rim they arn't even half as thick and due to the hard Maxtal material Mavic now use very prone to cracking.

[Chris Land]

What is the best way to measure rim wear?  What is an acceptable thickness?  I took them down for the LBS to look at and they suggested a pretty prompt replacement.  They weren't trying to sell anything as they suggested getting replacements from SJSC and they would build them up for me...

I have to admit that they have worn faster than I expect, but my mileage estimate may be a little low and this has included winter touring where I haven't been as circumspect about cleaning my rims as I ought to have been, plus alot of riding with a very heavy load (kids in trailer to nursery most days on my commute, plus panniers of books and fully laden camping tours with kiddy trailer... stopping that lot really isn't easy.)

[Polar Bear]

Chris Juden did a great article in the CTC mag a couple of years ago about this.   You need a vernier gauge and an old or broken spoke.   You make a sort of U-shaped-pincer with hooked ends that sit flush with the rim wall and under the hooked lip on the inside.  You measure the overall distance using the vernier and then subtract twice the thickenss of the spoke from the overall measurement to get the thickness of your rim wall.   I know I've not explained it very well at all but I will try and dig out the article.   If I succeed I will scan it in and post it.  

[TonySmith]

Dangermouse, I'm disappointed to see your comments on the Mavic rims. I traded in a Nomad with Sun rims for a Raven a few months ago and accepted Mavics because SJSC were unable to get Sun rims in 32 hole.

[Michel Gagnon]

Chris,

It's hard to predict rim wear by mileage alone. On one extreme, touring -- even loaded touring -- on flat or gently rolling terrain is very smooth on brakes and rims. At the other extreme, commuting in nasty weather, especially with a loaded bike (cargo, kids...) is bad on brakes and rims. Downhill racers race in muddy conditions and tend to wear brake pads in very few races.

Living the other side of the ocean, I'm not totally familiar with your weather, but riding in light rain, mist or drizel is probably amongst the worst: just enough humidity to lift all the dirt off the road, but not enough to wash it away. Ditto for icy conditions with sand or rock on the road.

I have yet to go through the rims of my tourer, but I use one set of Kool Stop Salmon brake pads per year. There was lots of loaded riding and touring with trailercycle and child trailer, but most of it occured in good or half decent weather. No 60-km ride with the kids during a snow storm or at -20 C. On the other hand, my commuter is used year round (360 days per year, maybe), and the front rim which is 2 years and 6000 km old is about to surrender.

BTW, I always brake with the front brake alone; it's by far the most effective brake. I occasionnaly use the rear brake to slow down in long hills, but I use it so rarely that I don't wear these brake pads.

I'm also a firm believer of Kool Stop Salmon (or dual) brake pads. They don't wear down as fast as Shimano brake pads (how would you compare 1 month to 1 year?), don't squeal (not with v-brakes anyway), have an almost as good performance in foul weather, and I think they don't wear the rims too fast (no grinding noise anyway). No idea if they are sold in U.K. however, but given your weather and that of Northern Europe, they would be highly recommended.


Finally, in terms of rim wear, I read once a recommendation that you should look at the rim face to see if it is concave. If there is a depression of more than 1 mm (not a groove, but a smooth path where the brake pads rub), then you should change the rims.  I'd like a second opinion on that, however.

[John]

I'd go for the SUN rims having used them successfully on tandems. The 721 replaces the D521 which I cracked round the eyelets. Have you tried Koolstop yellow brake blocks?

I watched a mate crash when his worn out rim failed - the side wall of the rim folded out, the tube blew out and the back wheel locked coz the tyre caught in the brake. I also saw a brand new Spinergy fail in the same way with no serious consequences coz the bike was sitting in the bike park at a Triathlon - on a hot sunny day.