Alex-Mitchinson Posted April 23, 2008 Report Share Posted April 23, 2008 (edited) Had my rear Dob rim for about a month now and I've never been able to get a nice sharp grind on it. I've always had a really noisy back brake with a med sharp grind but since I got this mag rim the sharpness is just non-existent! The grind also wears down pretty quickly which I suppose would be expected as it is a softer metal, but even so, for the short amount of time where it isn't worn down...it should be sharp. Pads have always been setup perfectly, perfect bleed and pads aren't worn at an angle. When grinding I normally have the grinder at a 90 degree angle and I recently put a new disk in it which has made a bit of a difference but not as much as I would like.I have used coust pads, worn plaz and worn snowy's on it and all have been much the same, going to be ordering some Neco pads soon so I'll see how they are but in the meantime....Is anyone else having this problem? Is it purely down to the fact that the metal is softer? Edited April 23, 2008 by Alex-Mitchinson Quote Link to comment Share on other sites More sharing options...
Bionic Balls Posted April 23, 2008 Report Share Posted April 23, 2008 i would say yes...that's exactly why...cos it's softer..!unlike other alloys used for rims...i don't think this is precipitation hardened (heat treated)....making it softer... Quote Link to comment Share on other sites More sharing options...
Luke Rainbird Posted April 23, 2008 Report Share Posted April 23, 2008 Yep, softer material means it won't grind/hold a grind so well.Ideally the rims seem to be aimed for a smooth rim, or comp use only (so infrequently, meaning the grind should last long enough for a comp, then be re-ground I would imagine) Quote Link to comment Share on other sites More sharing options...
LauraPalmer Posted April 23, 2008 Report Share Posted April 23, 2008 I used a 1,5 mm cutting disk(would fly around my ears at a standard rim) to grind my dob rim - got an excellent grind! - i use it with white heatsinkpads and my break is unexpected excellent! it´s better than my harsh grinded TryAll was with coust pads. cause of the softness of the white heatsinks, it seems the grind doesn´t go down quick - i have that setup for a few weeks now and didn´t even think about tar or bitumen... the only thing i hate about it is that squeeking noise - sounds like a pig getting slaughtered, never had such a loud noise before... Quote Link to comment Share on other sites More sharing options...
Phatmike Posted April 23, 2008 Report Share Posted April 23, 2008 Just count yourself lucky it's lasted a month. Quote Link to comment Share on other sites More sharing options...
Alex-Mitchinson Posted April 23, 2008 Author Report Share Posted April 23, 2008 I'm using heatsink snowy's at the moment and they are completely silent! My grinding disk is at least 1.7mm so could give a 1.5 a go. Quote Link to comment Share on other sites More sharing options...
LauraPalmer Posted April 23, 2008 Report Share Posted April 23, 2008 Just count yourself lucky it's lasted a month. i used washers to prevent the nipples coming out - i did it because i read from you, it only took you one week to kill it Quote Link to comment Share on other sites More sharing options...
Gandalf the Yellow Posted April 23, 2008 Report Share Posted April 23, 2008 i managed to get myself a 0.8mm disc. AWESOME, its nice and sharp and im using it with heatsink 08/cnc, nice noise and bite.i'd advice you to wear safety goggles and a mask if you have 1, as loads of crazy bits fly off, its quite a dangerous grind.. especially magnesium sparks.steve Quote Link to comment Share on other sites More sharing options...
Jason222 Posted April 25, 2008 Report Share Posted April 25, 2008 I've had a few dob rims grinded up now. The first time I used a sanding disc, the grind looked terrible, but it worked great, and very loud. Then I changed the pads, and it didn't work. lol So I regrinded with a grinding disc, worked okay...but the grind doesn't last long(1.5 weeks?)...On another rim I had, I did both as well, but it only lasted 1/3 as long(maybe 1-3 days)? So I would assume the rims are all different as far as how soft the metal is. I'd imagine that they'd be fine for comp use, grind once, use for the comp...but not much more than that...Mine you they're relatively sturdy considering the weight. Harder to flat spot than an echo rim in my experience? Quote Link to comment Share on other sites More sharing options...
Shaun H Posted April 26, 2008 Report Share Posted April 26, 2008 Mine you they're relatively sturdy considering the weight. Harder to flat spot than an echo rim in my experience?100% agree about the flat spotting thing.However they buckle sooooooo easy, spokes pulling through is not happy time either. Which is why I'm now back on a V!Z rim for the rear and not looking back.DOBs are however, mint for front wheels Quote Link to comment Share on other sites More sharing options...
Jason222 Posted April 28, 2008 Report Share Posted April 28, 2008 DOBs are however, mint for front wheelsYep! I'm running a DOB on the front, and a META rim on the rear(same as try-all but with harder alu). No problems at all with the front dob rim. I havent had any of my rims have the spokes pull through though...I've heard many times that they go discoloured when grinded (oxidized?) and I think that's a total myth. I've used two rims in the last 2 months, each grinded. No discoloration. Quote Link to comment Share on other sites More sharing options...
Gandalf the Yellow Posted April 28, 2008 Report Share Posted April 28, 2008 I'd imagine that they'd be fine for comp use, grind once, use for the comp...but not much more than that...its worked much longer than that for me with me 0.8mm grinding disc, had it for about 3 weeks now, get one and give it a go, it really does work.sharpness goes away quickly but because of how thin it is the disc cuts a deeper groove, maybe im not great at grinding i don't know, but for how 'smooth' my dob rim is at the moment its still offering a lot of bite.steve Quote Link to comment Share on other sites More sharing options...
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