Hi Alexei and
to the forum.
Unfortunately my rims are all 26" so it wouldn't be of much help to you if I were to measure one of mine.
You can either remove the cracked rim and measure it to find out what it's ERD is:
There are several ways to measure the ERD of a bare rim, but the simplest way is to place two spokes in the rim 180° apart and use an elastic band to pull their ends together in the centre of the rim. Then use a tape measure to measure the distance "A" between the two nipples. Simply add the length of the two nipples "B" to you measurement to find the ERD.
ERD = A + (2 x B)Unfortunately, rims are not always perfectly round, so the measurement should ideally be taken in three different positions around the rim and the average of the three readings should then be used.
Or:
You can measure the ERD without dismantling the wheel by simply removing the tyre and standing the wheel/rim on a flat level surface and then placing a straight edge across the very top part of the rim and measuring the distance between the lower surface of the straight edge and the level surface the wheel is resting on to find the Outer Diameter of the rim "OD".
The straight edge should be long enough to extend beyond the end of the wheel's axle to allow a nice straight run with the tape measure.
Dimension "C" can be obtained by placing the straight edge level across the small end of the lowest nipple and then measuring the distance to the level surface below.
If you have a vernier caliper with a depth gauge you can measure the distance from the outer edge of the rim to the head of the nipple and subtract it from "C" to find "B".
If you don't have a depth gauge, you may need to remove one of the nipples and simply measure it to find length "B".
ERD = OD - (2 x C) + (2 x B)I hope this helps.
Alan P.S. Whereabouts in Sunny Devon are you?
