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Mukluk, Enabler, Mukluk Ti and Surly’s Big Fat Larry

Our friends over at Surly have just raised the bar in fatbike "fatness" by releasing the 4.7" wide Big Fat Larry tire. We know many of you are wondering if this new meat will work in a Mukluk frame and Enabler fork. Short answer is YES. Long answer is YES, BUT.....

Mukluk 3, 100mm rims, and Big Fat Larry tires...

ENABLER FORK AND BIG FAT LARRY

Lets start up front with the Salsa Enabler fork which is sold with all Mukluk and Mukluk Ti framesets, and is also available separately as an aftermarket fork.

The Enabler fork has 127mm of clearance across the fork blades around the knob area.  

The BFL (Big Fat Larry) mounted to an 80mm rim has about 10mm of clearance from the knob to the fork blade and 9mm of clearance from the widest part of the casing to the fork blade.

Enabler fork, 80mm rim, and BFL...

On a 100mm wide rim, the knob clearance per side is about 10mm and the casing clearance is about 7mm. On a 100mm rim, a little tire squeezing needs to happen to get it past the front brake caliper, but it's nothing given the single digit pressures most people run.

Enabler fork, 100mm rim, and BFL...

We've only been using the BFLs on 100mm rims in the Enabler for a short time now, but have not had any problems with handling or mud clearance.

MUKLUK FRAME AND BIG FAT LARRY

Moving on to the Mukluk frame, what is shown below holds true for all current Mukluk frames out there, as well as the new Mukluk 2 and Mukluk 3 frames for the coming winter season. There were no changes to the chainstay forming and shaping between model years.

The BFL mounted to 80mm rims has roughly 9mm of clearance at the knob, and about 6mm clearance at the widest point of the casing to the chainstays.

Mukluk chainstay, 80mm rim, and BFL...

The BFL mounted to 100mm rims has roughly 9mm of clearance at the knob, and about 5mm clearance at the widest point of the casing to the chainstays.

Mukluk chainstay, 100mm rim, and BFL...

For both rim widths, tire clearance across the seatstays is ample (9mm knob, 7mm casing).

Mukluk seatstays, 100mm rim, and BFL...

Note that Joe Meiser has run the BFL in the alloy Mukluk, but he had to make some heavy drivetrain modifications to eliminate chain rub on the tire.

MUKLUK Ti AND BIG FAT LARRY

Lastly, we've got a new version of the Mukluk for 2012: the Mukluk Ti. The Mukluk Ti features Alternator dropouts for adjustable wheelbase and tire clearance, plus singlespeed capability. The clearance across the chainstays in the knob area is designed to be 118mm in the full-forward position. This number wasn't just pulled out of thin air. It was a compromise of getting the most tire clearance possible while still being able to manufacture a titanium frame with the strongest, most reliable chainstays. Depending on manufacturing tolerance, there is either very little clearance or just a slight amount of interference with the BFL at the full-forward position. However, pulling the Alternator dropout back creates more clearance.

The pictures and measurements reported below were collected with the Alternator in the full-rearward position. Our three Mukluk Ti prototype frames we measured were a little slim on the chainstay tire width spacing, so the actual production numbers should look a little better than what we are reporting here. 

The BFL mounted to 80mm rims has roughly 8mm of clearance at the knob, and about 6mm clearance at the widest point of the casing.

Mukluk Ti, 80mm rim, and BFL...

The BFL mounted to 100mm rims has about 6mm of clearance at the knob, and about 5mm clearance at the widest point of the casing.

Mukluk Ti, 100mm rim, and BFL...

For both rim widths, tire clearance across the seat stays is ample (10mm knob, 6mm casing).

Mukluk Ti seatstay, 100mm rim, and BFL...

Similar to Joe's setup on his alloy Mukluk, using a BFL in the Mukluk Ti would require some cassette truncation and chain line modifications to reduce/eliminate tire-to-chain rub.

 WHAT'S IT ALL MEAN?

The most important things to note and take away from this blog post as you run off to the LBS to get your super fat tires are this:

1)  If you intend to run a Surly Big Fat Larry in the rear of your Salsa Mukluk or Mukluk Ti frame, YOU WILL HAVE TIRE-TO-CHAIN RUB ISSUES!

 

2) If you intend to run a Surly Big Fat Larry in the Salsa Enabler fork, go for it! What are you waiting for?

 

 

A COUPLE LAST THOUGHTS BEFORE WE LEAVE YOU TO YOURS

Currently, the only solution available to eliminate or reduce tire-to-chain rub is to truncate the rear cassette and not use the granny ring up front. Through a couple conversations between Surly engi-nerd Thor and myself, Salsa has learned that the Surly Mr. Whirly Offset Double (MWOD) will potentially be another future option to solve/reduce chain rub for those looking to run 4.0" tires on 100mm rims, or 4.7" BFLs in the rear on Mukluk frames. As to what this is, how it works, and when it will be available, we cannot say at this time. When we've had the opportunity to spend a bit more time with a BFL we will do another post investigating the precise drivetrain modifications needed for Mukluks and BFL tires.

I AM AN ENGINEER SO YOU AREN'T GETTING AWAY THAT EASY

What many people don't realize is that the current "standard" fatbike chainline obtained through 100mm BB, standard MTB triple crank, and a 170mm non-offset wheel (or the equivalent 135mm x 17.5mm offset wheel), when in the granniest of gear combinations, only allows adequate chain-to-tire clearance when a 4.0" tire is used on a 65mm rim. It's no mistake that the original Surly Endomorph tire and Large Marge rims were these sizes. In the name of greater floatation, 80mm rims reduced this adequate clearance down to "very litte to none". The advent of 100mm rims and the Surly 4.7" Big Fat Larry blows past this limit with wreckless abandon and creates the need for a totally new chainline to allow use of standard 8, 9 or 10-speed cassettes in combination with granny rings.

In plain English...bigger tires and wider rims don't make anything easier...except riding across soft surfaces.

This post filed under topics: Fatbike Mukluk New Product Pete Koski Tech

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ABOUT THE AUTHOR

Pete Koski

Hi, I'm Pete and I am a product development engineer for Salsa. I like all kinds of riding from commuting to dirt jumping. I think flat pedals make you a better bike handler, that the thru-axle is vastly superior to the quick-release for off-road applications, and that moving through the world on bicycle allows one to see things they might not otherwise. I suffer daily from hunger-induced anger, also known as hanger. Outside of work and riding, I enjoy kiteboarding, traveling, and watching hockey.

COMMENTS (15)

MC | August 31st, 2011

Enquiring minds… What happens if I want to use an Alfine 11 hub? How’s the chainline there?  ;-)

Mike_AK | August 31st, 2011

The question you did not answer is how does a Big Fat Larry on a 65mm Large Marge compare to a Fat Larry on an 80mm rim?  I’m wanting to ditch the weak Graceful Fat Sheba rims on my Mukluk and replace them with the stronger Large Marge without giving up any flotation.  Will the Large Marge/BFL combo fit that bill?

Sean | September 1st, 2011

MC - Alfine is 135mm OD, rear of Mukluk needs 170mm OD hub.  So I think all IGH hubs (Alfine, Rohloff) are a non starter on Mukluk.

Unless these new dropouts on the Mukuk Ti change that paradigm

O'bie | September 2nd, 2011

Is there a internal geared hub that will work or is the simplest solution is to go single speed and grin and grunt! The bike would be great for cruizing the shoreline in the off season and also bombing through the state parks all winter.I’m vertically challenged so finding a frame my size is cool.

Sean | September 6th, 2011

Vincent:

That will work with a 135mm IGH if it has a QR axle.  I know the Alfine and Nexus hubs use special washers and threaded axle nuts, so unless it’s possible to change the axle on the Alfine to something more in the 170mm length so the non-drive nut and washer is on the outside of the dropout (instead of inside of the dropout) I don’t think it would work.

I’m not brave enough to crack open that Alfine and try to change the axle.  The innards of that hub are a watchmakers nightmare.

Craig Smith | September 13th, 2011

Awesome!!! So, if you upsize your Mukluk with 100mm rims and Big Fat Larry tires, does it become a Moon Boot?

Mike Jura | November 16th, 2011

Looks great. Now when can I get my hands on a mukluk 2? When might they be available again?

Kid Riemer | November 16th, 2011

Mike Jura - Contact .(JavaScript must be enabled to view this email address) and they will help you find one. Thanks for your interest in the bike.

Lars | January 6th, 2012

So if I want to go with a BFL rear tire on a 100 mm rim, a triple crank,  8 cogs in the rear, and a Phil Wood BB, how wide does the BB spindle need to be?

Filip | February 29th, 2012

Which rims would you recommend to use with the ‘H?sker D? 26x4.0?’ tires on a Mukluk Ti?

Kid Riemer | February 29th, 2012

Filip - You might get multiple answers to your question as there is no correct answer to this question. Also, I don’t have personal experience on the Husker Du tire yet.

Personally, I would choose the 80mm Surly Rolling Darryl rims. I think that rim size offers the most bang for the buck. It works well with the 3.8” tires, but the rims also work well with the larger Big Fat Larry tire…just in case you ever choose to go that route.

Filip | February 29th, 2012

Do the rolling Darryl causing any concern with chain rub and a triple crank (eg. E13 XCX+ triple)?

(Still need to find a way to get hold of a XL Ti frame…)

cherokee | March 10th, 2012

I have a moonlander and if does it all

Filip | July 24th, 2012

With the BFL already given this issue, I’m sure the new 4.8 Bud and Lou will cause even more problems but that is not my questions.

Will the Mukluk models (got a Ti) fit the Knard/Rabbit-hole combo?

regards

Filip

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