blue flow carbon wheels

Review: Blue Flow BF37/31 All Mountain Carbon Wheels

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Rachel’s been testing some value-oriented carbon mountain bike wheels from a UK-based company called Blue Flow Wheels. How did they hold up? Over to Rachel for the review!

I first came across Blue Flow when researching carbon wheel crash replacement schemes (see our ‘Ten Best Carbon Wheel Crash Replacement Schemes’ story). Based in Nottingham, it’s one of a few small UK companies that hand builds its wheels using sourced carbon rims and dependable hubs to produce competitively priced wheels.

blue flow carbon wheels
Blue Flow Wheels specialises in assembling mountain bike wheels with sourced carbon fibre rims.

The Hardware

Blue Flow’s component choice has been designed to provide a strong and reliable no-nonsense wheelset for a variety of difference riding styles. Rims are constructed from unidirectional Toray T700 carbon fibre and are available in 27.5in and 29in sizes, across four models:

  • BF30/24: 24mm internal width for tyres up to 2.2in wide
  • BF37/31: 31mm internal width for tyres 2.2-2.6in wide
  • BF42/35: 35mm internal width for tyres 2.3-2.8in wide
  • BF50/43: 43mm internal width for tyres 2.8-3.25in wide

All the rims are asymmetric to equalise spoke tensions, which increases the stiffness and strength of the wheel. When compared to an alloy rim the profile of the carbon rim is noticeably different. The 3.25mm thickness of carbon on each side of the hookless rim makes for a beefy looking and strong profile.

blue flow carbon wheels
We went for the BF37/31 wheelset.

Wheelsets are hand built to order onto Hope Pro4 hubs using either DT Swiss Competition or Sapim CX Ray spokes. Opting for the CX Ray will give you extra reliability and a weight saving of around 90g per wheelset but cost you an extra £70. Brass nipples are used as Blue Flow favour strength and durability over cost and a little extra weight. All that remains is for you to choose the hub width, its colour and the colour of your decals too.

Blue Flow BF37/31 Carbon All Mountain Wheel Specs

  • Rim // BF 37/31 (37mm outer width, 30.5mm inner)
  • Hubs // Hope Pro4 32h
  • Spokes // Sapim CX Ray
  • Tubeless // All rims come with Stans rim tape
  • Front // 15x100mm
  • Rear // 12x142mm
  • Total weight // 1704g (including tape)
  • Price // £825 (as built)
  • From //  Blue Flow
blue flow carbon wheels
All wheels are built around Hope Pro4 hubs, and a decidedly ‘normal’ spoke arrangement that most wheelbuilders favour.


Of course one of the big downsides of upgrading to carbon rimmed wheels is that if you do give it a mighty ding it’s not going to be possible to straighten it out with a pair of pliers. Given the higher initial purchase cost, buying a replacement will hurt that little bit more and puts many people off investing in carbon unless there’s access to some kind of discounted replacement.

Showing its faith in its parts and build quality Blue Flow offers an excellent crash replacement scheme that goes far beyond a standard two-year manufacturer’s warranty. If you do break your wheel, even if it’s your fault, Blue Flow will rebuild your hub onto a new rim for £180. This cover is offered to the original owner for the lifetime of the wheel and to subsequent owners at Blue Flow’s discretion. Alternatively, for £35 you can buy two years’ insurance, which covers the £180 replacement cost.

blue flow carbon wheels
The Blue Flow carbon rims feature hookless sidewalls and are tubeless compatible.

The Competition

The BF37/31 is priced well for a carbon wheelset, costing £755 for the base model with DT Swiss Competition spokes (rather than the Sapim CX Ray spokes tested).

The most apt comparison would be Sixth Element – a fellow UK brand that also offers hand built wheels using Asian-made carbon fibre rims laced to Hope Pro4 hubs. Sixth Element sells the comparable Classic SE38.32 wheelset for £977, so they are a little dearer, though Sixth Element does have a better best crash replacement scheme.

The other wheelset that sidles up against the Blue Flow BF37/31 is the Bontrager Line Pro 30, which costs more at £899 and goes for Bontrager’s own hubs rather than a set of blingy Hope Pro4s. However, it does have the excellent TLR tubeless system, along with the backing of a much larger brand (Trek). Check out the Bontrager Line Pro 30 review here.

blue flow carbon wheels
Carbon wheels cost more than their alloy counterparts, so warranty support is an important consideration.

Setting Up

Our test wheels were built to replace the stock alloy Rovals on my Specialized Enduro (non-boost, 650b). A discussion with Blue Flow Wheels’ main man Stuart confirmed my choice of the popular BF37/31 rim to accommodate the 2.3-2.35in test tyres. The internal width of the Blue Flow rims is only 2.5mm greater than what I had before, but it was enough to round out the shape of the tyre and stick the side knobs out further, to provide more grip when leaning into corners. Because my bike is non-Boost and is limited on clearance, I’ve not tried to run anything bigger than 2.35in, though the rims will accommodate a tyre up to 2.6in.

I was happy to see there was no choice but to have the excellent Hope Pro4 hubs. Though not the lightest, they are strong, reliable, easily serviceable with easy to source spare parts, and have end caps that are easy to swap out to switch between different bikes if necessary.

blue flow carbon wheels hope pro4
No surprises here from the Hope Pro4 hubs. Solid, buzzy, and easily rebuildable.

The wheels definitely look the part. The stealthy matt carbon rims with their subtle graphics, black CX Ray bladed spokes and nipples all laced to the shiny in-your-face red Hope Pro4 hubs really complete the bling look – I’m glad Stuart convinced me that black hubs was a far too conservative a choice.

The total wheelset weighed in at 1,704g (front 794g, rear 910g including rim tape).

The wheels come with yellow Stan’s tape already installed but not valves; I used a set of Stan’s valves which nicely fitted into the valve hole without any leaks. Tubeless tyre set up was straightforward too and there was no need for superhuman thumb strength to persuade the bead of both Schwalbe (Magic Mary) and Specialized (Butcher and Slaughter) tyres onto the rim. With the addition of some Stan’s sealant and valves, inflation was achieved easily with a track pump.

blue flow carbon wheels
The weight wasn’t that much lighter than the wheels they replaced, but the acceleration was noticeably better.

The Ride

The first thing that struck me is how direct and precise the BF37/31 wheels felt. The overall stiffness meant they tracked accurately and predictably through corners and in the rough stuff, allowing me to push harder and with more confidence. Unlike some other carbon wheels I’ve ridden this stiffness was not overly done and so didn’t become uncomfortable or pingy over rocks. The more I’ve got used to this more direct feel the more I’ve been able to ride challenging lines through rocky trails that I wouldn’t have had the guts to do before.

Acceleration was loads quicker than on my alloy wheels. Interestingly, the weight between the two wheelsets is very similar, and I’ve also been using the same tyres. Instead, the improved acceleration boils down to the stiffer carbon rims and the overall wheelbuild, which sees less of your pedalling inputs being absorbed into the wheel. The increased zip encourages you to ride in a more attacking manner.

blue flow carbon wheels
The wider rim gave a great platform for the tyres I tested them with.

The enhanced tyre profile due to the wider rim meant I was also able to make more of the side knobs and get tonnes of grip in corners. Combined with the stiffness, I’ve been able to really push the bike in a way that’s previously alluded me.

However, it’s worth noting here that not every tyre will play well with wide rims. Anything that is already square in profile can become shorter and more square, bulging the sidewalls out beyond the width of the main tread. In my case though, the Specialized Butcher/Slaughter combo and Schwalbe Magic Mary tyres all improved with the 30.5mm rim width.

The wider rim does slightly increase the volume of each tyre, so I’ve been able to drop my tyre pressures by a good few psi to improve traction. Because the tyre beads have a wider anchor point though, the sidewalls are supported enough that the tyres don’t squirm around.

blue flow carbon wheels


I’ve had absolutely no issues with the wheels. Despite a good few rim-dings and an odd clumsy cased landing as I’ve played with the tyre pressures, they’ve remained true without any need to result to using a spoke key. If that day should ever come the brass nipples used in the build should ensure that the spokes will still turn and not be corroded as can happen with alloy nipples. And if things ever do go particularly pear-shaped, the crash replacement scheme is nice for the added peace of mind.


The Blue Flow BF37/31 is a well-priced, light and stiff trail wheelset. They have a direct-feeling on the trail with good acceleration, and their on-trend width will suit modern 2.3-2.6in tyres well.

Along with the solid Hope hubs, workaday build and warranty support, these are worth checking out if you’re looking to make the jump to a set of carbon hoops.

Want to see what other options are available? Then check out our group test of ‘6 Carbon Wheels Under £1500‘!

Review Info

Brand: Blue Flow Wheels
Product: BF37/31 All Mountain
From: Blue Flow Wheels,
Price: £825 (as tested)
Tested: by Rachel Sokal for 5 months

Comments (5)

    I’ve been running the wider i35 29inch versions of these for nearly a year and they’re running as true and tight as the day I got them. I bought these a second pair of wheel to run on my evil following MB and i ended up leaving them on. As the review says they strike a great balance between stiffness and damping, much less tiring and yet more composed than my other more expensive set. All the benefits in terms of acceleration and tracking without the vibration. The only negative I can think of is that they’re not the lightest wheels but this isn’t really a consideration for me when you consider the benefits they bring. Ive been running Hans Dampf addix 2.6 on the front and nobby nic 2.6 on the back at around 18-19pis and have yet to find a reason to try anything else. Great wheels and nice rider run company to deal with:)

    Also running these and love them, stiff and responsive. They have been utterly reliable for 2 years and I know would have destroyed a couple of sets of Alu in the time I have had these. I will never go back to Alu. Stuart is also a gent and is a pleasure to deal with. Couldn’t recommend the wheels or the company highly enough.

    Interesting that they say to use i31 rims for 2.2-2.6 tyres.
    I’m currently using 2.35 tyres on the i19(!) rims I have now. I’ve almost scraped together the bits to change to i23/i25 and am looking forward to seeing what difference that makes.
    I’m the total opposite end of the price scale though. I’m looking at less then £100 for rims, hubs and spokes, front and back!

    I’ll echo the above – Stu is a top bloke and really helpful.

    I ended up keeping my existing Hope Pro 4’s and getting him to build new wheels with his rims on them. I’ve been running them since the summer and so far, I can’t fault them. The quality of the build is really good – they’re still true and there was no in or groaning on the first ride out. They’re noticeably stiffer than my old ARC 30’s, especially in corners without feeling harsh. Not super light, but they seem tough so far and are pretty good value for money.

    I have a set of the 38/41 27.5s. Ran on my Mojo3 and now my Solaris Max. They’ve been to very rocky places, and abused on a weekly basis. Still in great shape with only a few spoke tweaks. Agree with review, direct without being unduly stiff.

    I’ll have another set of the 29s next year. Wish Stu didn’t something other than hope hubs tho.

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