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RockShox Bluto Fit Chart For Salsa Fatbikes

Chances are you've seen the news around the release of the new RockShox Bluto fatbike suspension fork.

The crew here at Salsa feels extremely lucky and grateful to have been afforded the chance to offer insight and direction to the Bluto project at the onset, as well as get a chance to test ride pre-production samples. We're ecstatic with what RockShox have achieved and we’re stoked that Salsa customers now have a chance to experience Bluto on their fatbikes, too.

Being on the front edge of any new product genre is risky; ideas and designs change and evolve quickly. What was the "standard" today can be obsolete tomorrow. Fatbikes are no exception, but the good news is Bluto works on a large majority of Salsa fatbikes sold to date. Below is a summary of Bluto/Salsa compatibilty.

The following frames use straight 34mm (1-1/8") headtubes. This type of headtube is not compatible with tapered fork steerers, which makes it impossible to run Bluto on these models.

2011 Mukluk (Aluminum, Blue)
2012 Mukluk 2 (Aluminum, Black/Red)
2012 Mukluk 3 (Aluminum, Blue)
2012/2013 Mukluk Ti (Ti, Brushed Finish)

If you have any other Salsa fatbike frame, we have good news: Bluto can be fitted to your frame. I'll now walk through each model grouping, as each has a few special requirements to make it work.

2013 Mukluk 2 (Aluminum, White/Green)
2013 Mukluk 3 (Aluminum, Orange)
2013 Mukluk Frame Only  (Aluminum, Black/Purple)

These frames can be fitted with a Bluto fork set to a maximum travel of 80mm by following the two steps listed below:

Step 1: New Headset
These frames use a 44mm straight headtube and came spec'd with a ZS44/30 lower headset cup and crown race to fit the stock 1-1/8" straight steerer Enabler fork.  In order to fit a Bluto to these frames, a new EC44 lower headset cup must be purchased and installed in the frame and the matching crown race installed on the Bluto.

Step 2: New Front Hub or Wheel
These bikes came with a front wheel using a Salsa Enabler hub, which is a 10 x 135mm quick-release hub and is not convertible to the 15 x 150mm thru-axle hub spacing the Bluto uses. Options are to build a new front wheel or re-lace your existing rim onto a new 15 x 150mm thru-axle hub. Salsa has created a front hub compatible with Bluto and it will be available for sale the same time the forks are. 

2013 Beargrease (Aluminum, Black/Blue)

These frames can be fitted with a Bluto fork set to a maximum travel of 80mm. No headset modifications are necessary. The stock 40mm nominal crown race can be carefully removed from the fork and reused. However, considerations for the front wheel must be made as described below:

Step 1: New Front Hub or Wheel

These bikes came with a front wheel using a Salsa Enabler hub, which is a 10 x 135mm quick-release hub and is not convertible to the 15 x 150mm thru-axle hub spacing the Bluto uses. Options are to build a new front wheel or re-lace your existing rim onto a new 15 x 150mm thru-axle hub. The Salsa Fat Conversion 150mm front hub that is compatible with Bluto will be available for sale the same time the forks are. 

2014 Mukluk Ti (Titanium, Green/Clear)
2014 Mukluk 2 (Aluminum, Gold)
2014 Mukluk 3 (Aluminum, Red or Matte Black)

These frames can be fitted with a Bluto fork set to a maximum travel of 100mm. No headset modifications are necessary. The stock 40mm nominal crown race can be carefully removed from the fork and reused on Bluto. However, one of the following wheel modificiation must be made:

Option 1: End Cap Swap & Wheel Dish

This option is only intended for wheels with Salsa Fat Conversion front hubs and rims with 12.5mm or less spoke hole offset. (NOTE: This includes the stock front wheel.) The Salsa Fat Conversion front hub is convertible from 9 x 135mm quick-release to 15 x 150mm thru-axle by changing the end caps. Salsa will have these end caps available around the same time the fork is. The end cap swap keeps the brake mounting surface aligned properly with Bluto, shifting the hub to the left side of the frame/fork centerline. In order to keep the rim and tire centered in the frame, the wheel must then be re-dished 7.5mm to the drive side. Warning - This option cannot be used for Surly Clown Shoe rims, or any other rim with spoke hole offsets larger than 12.5mm that is laced to a Salsa Fat Conversion front hub. The re-dish yields poor bracing angle of the spokes on the right flange and can result in an unstable wheel.

Option 2: New Hub or Front Wheel
Salsa is offering a 15 x 150mm Fat Conversion front hub compatible with Bluto and it will be available at the same time the forks are. This option is best for people who want to use rims with larger than 12.5mm offset spoke holes (like Surly Clown Shoe), or people who don't want to bother with Option 1 above. This option also results in a better tension-balanced wheel build.

2014 Beargrease XX1 (Carbon, Green/Yellow)
2014 Beargrease X9 (Carbon, Blue/Purple)

Beargrease carbon frames can be fitted with a Bluto fork set to a maximum travel of 100mm, but it is a little tricky depending on frame size. Carefully review size-specific info below. Wheel modification considerations are the same for all sizes.

Small:  Stock lower headset bearing is okay. A special Cane Creek crown race must be used in favor of the stock race in order to slightly lower the crown a few millimeters and provide adequate clearance between the blue compression knob and the downtube.  Without this special crown race, this knob will contact the downtube, and damage to the frame will occur. Salsa Customer Service (support@salsacycles.com) has coordinated to make these races available to owners of small Beargrease frames at a nominal fee through their local Salsa dealer. Wheel considerations must also be made, see below.

Medium: Stock lower headset bearing and crown race should be okay. On every Medium of this model we have checked, the blue compression adjustment knob on the Bluto fork cleared the downtube by 1mm. However, it is possible that due to manufacturing tolerances in both the frame and forks that some MD frame and fork combinations do not clear. If this ends up being the case, the special Cane Creek crown race required for the small can be used on a medium frame with lack of clearance to fix the issue straight away. Wheel considerations must also be made, see below.

Large & X-Large: The stock lower headset bearing and crown race are okay. Downtube clearance on these sizes is adequate. Wheel considerations must be made, see below.

For all size 2014 Beargrease bikes, one of the two wheel modifications must be made:

Option 1: End Cap Swap & Wheel Dish

This option is only intended for wheels with Salsa Fat Conversion front hubs and rims with 12.5mm or less spoke hole offset. (This includes the stock front wheel.) The Salsa Fat Conversion front hub is convertible from 15 x 142mm thru-axle to 15 x 150mm thru-axle by changing the end caps. Salsa will have these end caps available around the same time the fork is. The end cap swap keeps the brake-mounting surface aligned properly with Bluto, shifting the hub to the left side of the frame/fork centerline. In order to keep the rim and tire centered in the frame, the wheel must then be re-dished 7.5mm to the drive side.  Warning - This option cannot be used for Surly Clown Shoe rims, or any other rim with spoke hole offsets larger than 12.5mm that is laced to a Salsa Fat Conversion front hub. The re-dish yields poor bracing angle of the spokes on the right flange and can result in an unstable wheel.

Option 2: New Hub or Front Wheel

Salsa is offering a 15 x 150mm Fat Conversion front hub compatible with Bluto and it will be available the same time the forks are. This option is best for people who want to use rims with larger than 12.5mm offset spoke holes (like Surly Clown Shoe), or people who don't want to bother with Option 1 above.

Below is a chart that visually displays the information above.  As with any component upgrade, we strongly recommend you work with your local Salsa Dealer to get a Bluto fit to your Salsa fatbike. They have the knowledge, skills, and tools to do this correctly.

Click chart for full-size version

RockShox Bluto Salsa Fatbike Fit Chart

This post filed under topics: Beargrease Bucksaw Fatbike Mukluk 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 (5)

Brian | April 28th, 2014

Thanks for posting this information so quickly.  Planning to switch my bike over since I ride it all year round but have a few questions.

-If you stick with the recommended travel settings will it change the geometry any?
-Would longer travel just affect handling or is there tire rub / clearance issues in full compression?

PK | May 23rd, 2014

Brian,

Sticking with the recommended travel settings (aka fork lengths) does not effectively affect the geometry.  Like our other MTB hardtails, we design around a “sagged” suspension fork length and then make the rigid fork that length.  The Bluto at 25% sag in the recommended lengths works out to the same length (+/1 a couple millilmeters) as the rigid forks.

Tire clearance/rub at full compression does not change as fork length changes. Bottom out is the same for every travel length, it’s the initial starting point of the wheel that changes. That said, we cannot recommend or endorse using a fork longer than the stated travel amount.  Not only does it skew the geometry and alter the riding experience from out initial intent, using a longer fork also transmits higher loads to the frame.  We design and thoroughly test all our frames around a certain fork length.  We cannot guarantee or be responsible for the frames integrity when a longer fork is used, as we have not tested and certified it for those longer lengths.  Please note that using a longer fork length than recommended voids the frame’s warranty.

Michael | June 9th, 2014

Would the Bluto fit a 2013 Mukluk 3 (green frame)?

Sean | August 12th, 2014

I notice that the above fit chart for Rock Shox Bluto only says the 2013 Orange frame is compatible with the suspension fork. Not to split hairs but isnt the Green the same frame or does it have a different head tube. Just double checking, thanks.

Kid Riemer | August 18th, 2014

Sean and Michael - I think you are referring to the sort of Olive Drab, MIlitary Green color frame from 2013. Yes, the Bluto fits that frame (officially noted above as a 2013 Mukluk 2 frame).

For what it is worth, the Bluto is a marvelous addition to a Mukluk if you are using your bike on dirt a lot. You will not be disappointed in making that addition.

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