Drilling My Fatbike Rims…

15 05 2012

Sharon’s front Pugsley wheel…

I’m [slowly] working on building up Sharon’s Pugsley from the parts Kurt gave me. The frame has been powder coated and new headset installed. The next move was cleaning and drilling out her Surly Large Marge rims. These Large Marge DH rims are heavy – very heavy, but they are paid for so rather than replace them I decided to drill them out.

Just a reminder where we started…

I’ve got Sharon’s front wheel drilled out and looking back I gotta say this is not a DIY project I would recommend unless you are totally motivated to get ‘er done. It’s noisy, messy [you’ll be covered with tiny metal shards] and you can potentially trash your rim. If you own some fat rims and want to drill them fair enough. I’ve warned you!

I’ll finish her rear rim, but I won’t drill out my Surly Large Marge DH rims. I have enough leg power that it’s not vital and when the time comes I’ll just buy some new single walled Surly rims that are already cut out. When I can afford it the price will be worth the hassle I’ll save plus I’ll use light weight hubs for a really killer weight savings and keep my old Pugsley wheels for heavy duty use.

Sharon won’t throw money at bikes like I do [silly!] so one set of wheels has to do it all.

The hole saw – your friend…

I have very few powered tools so here is what I drilled out the rim with:

  • electric drill
  • small drill bit for pilot hole
  • 1.5″ hole saw attachment
  • marking tool
  • ruler
  • dremel tool with grinding bits
  • needle nose pliers
  • eye protection
  • 6 ice cold Mexican beers and a fresh lime


This wheel has been used a lot over several years so I gave it a once over only to discover the aluminum spoke nipples are corroded to the point of self-destruction. I replaced a few with bronze nipples, but at some point this wheel will need to be totally rebuilt.

Oh well. You aren’t riding hard if you aren’t breaking things…;)

Measure and mark…

First thing I had to do is pull the tire, tube and rim tape. Then I marked halfway between the spokes along the centerline of the rim.

Drill pilot holes…

Next up drill a pilot hole at each mark.

Test fitting the hole saw…

I had room for a 1.5″ hole between the spokes.

Raw hole cut into rim…

Start the less than fun process of cutting out holes. This will generate a ton of tiny metal fragments so do it outside if you can or at least not in the living room on your lovely deep shag carpet…=-) I braced the wheel up against the steps of my deck while cutting out the holes. You can use a wall or work bench. Other folks have built jigs to hold the wheel or put the wheel into a fat bike frame that was secured to something else.

Upgraded hole saw…

I foolishly bought the cheapest hole saw at my local hardware store when I started this project. It lasted about halfway through the first rim before it was toast. So I went back and got a better quality hole saw which should get me through the second rim. As soon as you notice the cutting performance of your saw changing swap in a new one.

Holes cut…

Cutting the holes is not tragically hard, but I’ve done more fun DIY bike projects.

Rough edge…

Once the holes were cut I used a dremel tool to smooth out the rough edges. I may use a round file for wheel #2 as it was hard to maneuver the dremel around the spokes.

Smooth edges…

These rims are old and this bike will actually get ridden so I didn’t waste a lot of time trying to make it look bike show perfect. Note the self-destructing middle spoke nipple.

Weight savings = ~200g…

I collected all the big bits of metal and weighed them as 195g say ~200g savings for both rims with all the smaller bits included.

Truing the wheel…

After all the cutting and grinding was done I replaced some corroded nipples and gave the wheel some love. I’m not looking for perfection. I just don’t want the wheel to exploded mid-ride.

I should note that given the double wall construction and amount of material used in these Large Marge DH rims I don’t think the drilled out holes will compromise their strength in any meaningful way. Big guys are rocking the single walled cut out Surly Marge Lites so we shouldn’t have an issue.

The purple pugsley starting to come together…

It took me a solid afternoon of futzing with this one wheel to get ‘er done. I’m not fast at these sorts of projects so you may do better.

I threw some white duct tape in the rim to cover the new holes so I could mount the tube and a skinny 3.8″. Sharon will probably come up with something a bit more “pretty” at some point.

Front done…now for the rear rim…

So a few warnings:

  • don’t hurt yourself [wear eye protection]
  • don’t mistake the valve hole for a pilot hole and cut it out
  • don’t get too enthusiastic pressing down on the hole saw or you can take out a couple spokes



22 responses

15 05 2012

I am really curious, what made Sharon wanting a Pugsley? Is it riding in Hartland, or do you plan some sand riding?

15 05 2012

@Misha – Sharon wasn’t dying to get a Pugsley. I gave my friend an old 4×4 truck for free and he decided to give me am old Pugsley he wasn’t using which was Sharon’s size.

We go to Baja every winter and when I drive I take down my Puglsey and I’ll take the 2nd for Sharon. We’ll ride them on our MTB trails locally, we’ll do some sand riding at the OR Dunes.

It’s not a bike we would have paid full price for given our budgets at this time, but it will be fun.

15 05 2012

I’m curious why a fat bike wheel would ever have been built with aluminum nipples, especially in combination with a rim as heavy as the Large Marge. I know these aren’t exclusively Winter bikes, but even so…..

15 05 2012

@Robert – that wheel was built back when fat bikes were new and the guy building it probably didn’t even think about the saltwater and road salt it would be subjected to. It has lasted 4yrs so they didn’t cause any issue so far, but in the long run they’ll need to be replaced.

15 05 2012
All Seasons Cyclist

I love it! I’ve wanted to drill out the Rolling Darryl Rims on my Surly Necromancer Pugs, but just can’t bring myself to start cutting on those rims — on screw-up and I’m out of a lot of money! Congratulations on a job well-done!

15 05 2012

Thanks. It’s not a fun job so unless you are highly motivated by the weight savings I’d stick with the stock Necro wheels.

16 05 2012

Hey Vik
Get yourself a hole deburrer as it makes easy work on those sharp hole edges.

Also marking out using a dot punch will make for accurate pilot hole positioning. I have to say that those holes look real close to the spoke holes but it’s your project. nice jiob.


16 05 2012

You are a very brave man!

17 05 2012

@Ian – the holes are fairly accurate as there is a groove along the inside of rim the drill sits in when starting the pilot holes. So you only have to control the movement in one direction.

When you consider the cut out Surly rims are single walled and are suriving 200lbs guys riding them on rocky MTB trails I have no concern at all that these rims will be fine for Sharon. Especially when both are rear wheels with minimal dish [IGH and SS rear hub].

24 05 2012
Bethany Frerichs

I’ve wanted to do this with mine, but I’m lousy at power tools and would ruin the rims. Plus my husband would probably not be happy. Yours look great.

24 05 2012

@Bethany – you won’t ruin the rims, but you could mangle a few spokes….don’t ask me how I know that…;) Maybe buy your husband a 6 pack and ask him to drill out the wheels for you?

31 05 2012

I have to ask: what is the strapping (or wiring or etc.) running through the holes in the front wheel cog?

31 05 2012

@JRZ – that’s spectra cord. You couldn’t get a Surly disc FG hub when I built that bike so I used a SS hub and thread locked and “wired” the FG cog on. By now it’s probably corroded on permanently!

26 11 2012
Cheering up « OUT SOMEWHERE

[…] plus/minus two kilograms anyway? Well, if it bugs me long enough I’ll  do it like Vik. Conclusion: If you like to experiment, get it 32 hole when building […]

31 05 2013

Was the ~200g savings per wheel?

Also, how does this affect wheel strength. They say it doesn’t affect torsional strength but I’m not an engineer and don’t know what that means. I want to ride this all year on ruff trails and smooth snow so I want to be sure to not sacrifice my rims on the bumpy stuff.

And thanks for the instructions!

31 05 2013

@John – weight savings was 100g per rim

– these are super burly double walled rims there is no impact on strength

– consider all the 200lbs+ guys riding Surly’s cutout single walled rims on dirt/rocks with no issues

– by comparison these rims are tanks even with cutouts

31 05 2013

@John – you can also easily save more than 100g per wheel using lighter tubes and well over 100g per wheel on lighter tires.

If you measured 10 of the same model/make of tire there will be a significant variation that can save you a lot of weight.

31 05 2013

Cool. Thanks.

10 04 2014
Elijah Donat

I was thinking of doing this cause I also have the single wall marge lite on a 907 and it’s much lighter/faster. The double walled large marge as pictured here is same as on my pug. If drilled out seems it would be very bad for water and sand which is what I use mine for in AK. Seems pretty questionable cause loose material that will pack into the double wall cavity.

10 04 2014

@Elijah – we’ve used the drilled double walled LM rims in Baja with no sand accumulation in the holes. We’ve used them in the PNW with no rocks or mud building up in the holes. We haven’t tried them in any snow.

10 04 2014
elijah donat

Alaska has big 20 foot tides so we ride at low tide year round in estuaries and along intertidal zones. Lots of wet sand and water crossings. Large Marge drilling was attractive till I saw the double wall cavity. Water will fill and weight rim. We ride Katzahien and Chilkat rivers. They are glacial so very big and all the crossings are under 2 feet. Have you used the drill out in water?

10 04 2014

@Elijah – we haven’t used our drilled out rims in the conditions you describe.

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