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Lightening rims

2217 Views 11 Replies 9 Participants Last post by  Max
I had a friend (who used to be a race team mechanic for SC, I think) tell me that they used to lighten rims for racers by drilling holes on the inside surface between the holes already there for the nipples.. Anyone done this? Will this lead to unexpected and catastrphic rim failure?


Oh, by my best rough guesstimation, it'd save maybe 40grams/wheel (3/8" holes)...
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Actually on trials bikes its common to drill holes straight thru both the walls between the spoke holes. No it won't make a difference in wheel strength.
You'd save less, 40g a rim, that's 10%. If you look at a rim in pieces the length between 2 spoke holes, 10% off that is a LOT. I've been thinking about this somewhat as well. I'd see more in sanding down the spokebead and sidewalls. Drilling is step 2 :)
old trackie trick

yeah when I started racing track with the ABLA, later USCF, that was a fad, to drill the inner rim bed in between the spoke holes. Nisi, and others, even offered lightweight sewup rims that were factory drilled. I still got a front wheel with a 280 gr. Nisi Sludi like that, only it's not factory drilled clear thru, but there are deep dimples between spoke hole where the rim bed was ground down. Good rim, it's 20-plus years old and still rideable.
Eddy Merckx's hour record bike got that treatment.
Maybe makes sense when you're starting with a 300 gr. track sewup or time trial rim. I would say losing an ounce or two on a pair of mtb wheels by drilling the rims would be a total waste of time, as the slight gain in acceleration from a lighter rim mass would only make a difference -- a small difference at that -- on a smooth surface. On trails, I seriously doubt one could measure, let alone feel, any difference. But hey, got a drill, go nuts, doesn't bother me if you do.
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mongoose bmx rims called pro class which were Araya 7X rims drilled through and had color rim (mylar) rim strip to cover the holes and kept the inner tubes from popping out.

dirt diggler

I did this trick on my M*avic 317s and it's still pretty strong, but I weighed the before-and-after thing..... I saved 4 grams on each rim, which is not a lot. I was thinking of drilling two holes between each spoke hole, but I tried to keep the strength of the rim. Maybe it would be strong anyway.

Don't worry about the strength of your rims after the drilling, it will hold up !



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Funny, I did the exact same thing and saved 5 grams! :) I drilled an X317 that was pretty much ready for the trash bin (lots of dings) so I didn't have anything to lose. I was hoping for at least 10 grams. Oh well. I really doubt the strength will be affected as long as the holes are clean (no sharp edges to start cracks). It took far less time than I thought (maybe 15 minutes tops with a drill press including center-punching each hole). I didn't drill a hole at the weld area. I figured that was asking for trouble and, besides, leaving that material helps balance out the valve stem on the opposite end! :)

Now I wonder if it would be worthwhile & safe to drill my Stan's rims.
this drilling trick works really well for trials rims because they are wide (for stability). The wider the rim, the larger hole you can put through it.

compare those big holes to the nipple holes. I have one of these rims and there's no noticeable strength difference, but a big weight difference. As liberal as I am with the drill though, I wouldn't drill any rim less than 23-25mm wide, there isn't enough width to have any deadweight material, on thinner rims all the material is needed to keep its structure (I'm sure some engineering type can elaborate on this, it's the same principle that allows shimano to have hollow cranks without much strength loss). I've got a rhyno lite on the front of my 26" trials bike which has half inch holes through the outer wall as well as having the whole inner wall dremelled out and taking around a third of the brake wall thickness off. This was more of an experiment with an old rim - I dropped about a third of the weight and it's been running with no problems for over a year now.

- Joel
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Only 4 grams? Man, how thin is that web anyway? Oh wait, my bad.. Last time I calculated the estimated weight loss I most have put the decimal place in the wrong spot.. I just re added it up and came up with 4.8 grams if you drilled 32 3/8" holes in .03" think aluminum... You guys are right, that not a whole lot of weght to loose for the effort involved...
did the same thing as jean-seb did to his rims, but only the side where the rimstrip is seated. didnt want do have dirt etc. get inside my rims. used a 8 mm drilling bit. saved 6 g each..... not worth the time wasted by drilling IMO
I didn't drill both walls... ?

:) you can see through only at the valve hole :p .

I didn't want the dirt inside either.


jean-seb said:
:) you can see through only at the valve hole :p .

I didn't want the dirt inside either.


sorry, just came back from a 6 hrs car ride at 30° and my head felt like an egg boiled for 3 minutes only :-/

i took only a quick look at the rim

btw: i raced the national hillclimbing championships this weekend. what a WW event :)
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