Bicycle Mechanics - Groove in Rim: Another What's-It Inquiry

On my Mavic rims, there's a groove about 6mm from the circumference, maybe 1mm deep. It’s on both sides of the rim. The groove bisects the plane that the brake pad contacts the rim when brakes are engaged.

All I can make of this is that it’s a rim wear gauge. If so, it just seems that there’s a whole lot of potential brake friction acreage taken up with “mere” measurement.

So. . .what IS this thing?

Anyway, I’ll bet someone out there in BF Land knows th’ answer. . .as usual Mercy Buckets [as my ancestor Clovis said when the Bloody Revolutionaries spared him from the Gilly-Tene].

this is a channel for water to escape when braking in wet conditions. it works pretty well and it maybe even reduces 3 grams of the wheel weight.

It's a wear indicator. When that sucker bottoms out, it's time for new rims. Some other manufacturers just use a little dot.

It's a wear indicator. When that sucker bottoms out, it's time for new rims. Some other manufacturers just use a little dot.


yup, Langolier is correct.

mavic says it is a wear indicator

http://www.mavic.com/ewb_pages/p/piste_produit_jante_OPEN_SPORT.php?gamme=route

wow my lbs has given me a lot of bad info. i was used to flat rims and when i bought my 05 Rockhopper they said the groove was for better braking when wet. i dont know what to think about that lbs.

People think that because that's how car tires work. It almost makes sense, but with no radial channels how is the water suposed to move into the grove other than by the radial channels on the brake pad, and why would you want it there anyway when centrifugal force is just going to spin it back out onto the outer half of the rim?

No offense to the good bike salemen out there (I know a few), but often in a shop those who do not know enough to fix bikes are the ones selling bikes.