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PostPosted: Fri Jun 15, 2018 5:33 pm 
Old School Grand Master
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Joined: Sun Mar 14, 2010 2:33 am
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Location: daaan saaaf
I have a set of wheels and the rims don't look overly worn, but when braking, I get a pulsing through the brake lever on the front wheel as if there were a fat, or possibly thin section on the rim. I can't see anything or feel anything if I run my hands around the rim.

The spokes and the hub are fine, so I was considering just replacing the rim. The original rim is an Araya RM-20 with an ERD of 547mm. RM-20s do occassionaly show up for sale, but if I can't get hold of one, how close do I have to be with the ERD, can I use a rim that is a milimetre or so larger or smaller with the same spokes?


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PostPosted: Fri Jun 15, 2018 5:39 pm 
King of the Skip Monkeys
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Yes.


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 Post subject: Re:
PostPosted: Fri Jun 15, 2018 5:55 pm 
Old School Grand Master
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Location: daaan saaaf
Cheers!

How close do I have to get?


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PostPosted: Fri Jun 15, 2018 6:11 pm 
King of the Skip Monkeys
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Well, try it first, most spokes have a good 3 to 4mm leeway anyway


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PostPosted: Mon Jun 18, 2018 6:27 pm 
Old School Grand Master
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Location: daaan saaaf
This is turning out to be a bit of a pain in the butt, it seems 26" rim brake rims are now as rare as hens teeth to start with and finding some with a similar ERD all but impossible.

Those that are available are super heavy duty trekking, or E-bike rims, and correspondingly lardy. I'm not a weight weenie, but I don't really want to use rims that 100 to 150g heavier, per rim, than my originals.

:(


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PostPosted: Mon Jun 18, 2018 6:50 pm 
King of the Skip Monkeys
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Joined: Wed Nov 07, 2007 4:34 pm
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http://freshtripe.co.uk/velo-orange-diagonale-rim-26/

http://www.chainreactioncycles.com/mavi ... prod140776

https://www.sjscycles.co.uk/rims-tape/3 ... im-silver/


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PostPosted: Mon Jun 18, 2018 6:52 pm 
King of the Skip Monkeys
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Posts: 29472
https://winstanleysbikes.co.uk/componen ... ne-mtb-rim


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 Post subject: Re:
PostPosted: Mon Jun 18, 2018 7:40 pm 
Old School Grand Master
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Location: daaan saaaf
Thanks LGF.

Playing it safe, I was looking at rims with an ERD in the range of 543 to 551, 4mm either side of what I have, although very few seem to be more than 547.

Other than the Velo Orange rims they are all a bit under 543mm. At £55.00 a pop, the VO rims are just too expensive, I could get a whole new set of wheels of a similar quality to the originals for just a few pounds more; Deore LX hubs, Sapim plain guage spokes and Mavic XM117 rims came in at £115.00.

The XM117 look to be ideal, but I've no idea what the ERD is, I've seen it listed at 540mm at the low end to 545mm at the high end and a couple of measurements in between. Mavic's web site is no help and doesn't specify it.


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PostPosted: Tue Jun 19, 2018 7:45 am 
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Joined: Mon Feb 11, 2008 9:42 am
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Mavic quote ERDs different to everyone else, check on an online wheelbuilding tool for the actual ERD.

Also, check how long the current spokes are. i.e. how far they come through the nipple. Might give you more of an idea where to aim with your replacement ERD, as i've found much more than a 2 or 3 mm out from the "ideal" length you start to get into problems down the line. Too short and you might start to fail nipples early (as the spoke thread doesn't go far enough through the nipple) too long and the threads bottom out if you need to true the wheel.

And if it's just sapim plain gauge spokes, buy some new ones to suit whatever ERD rim you buy. Sapim leaders are only ~25p each.


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PostPosted: Tue Jun 19, 2018 3:03 pm 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
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Location: New Forest, UK
Agreed, take Mavic's number and add around 3mm for the ERD.

I had exactly the same pulsing symptoms on a Mavic 317 - it turned out to be a light rim dent.


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