Speedline Spinners vs Shimano DXR — Which Crank Should You Buy?

By Bill Ryan · Founder of Supercross BMX · Former Technical Editor, BMX Plus Magazine · Workshop columnist, GO Magazine · Designer of 8× Bike of the Year race frames · 37+ years in BMX

Every rider building a bike hits the same fork in the road at the crank. Shimano has been in that fight a long time, and the DXR is the crank most riders think of first when they picture a serious aftermarket setup. And we get asked a lot, why should we buy the Speedlines instead of the DXR? The reason is that DXR's are great cranks, we have had many of our riders use them for years, But as time and technology advances so do our products. And we built the Spinners to be the other answer — the hybrid arm, at a lower number, with test data behind it. Riders have asked us to put the two side by side often enough that it's time to just do it. So here we go.

How the Spinners is built

The arm is cold forged aluminum with the middle hollowed out. Forging lines up the grain of the metal instead of cutting through it, and hollowing takes material out of the center where it does the least work.

Then we bond a Toray T700S carbon fiber back bone onto it. The aluminum handles the abuse, the threads and the crash landings. The carbon spine runs down the back of the arm and fights the flex that shows up when a rider stands and stomps. Carbon resists bending along its length better than anything, so putting it exactly where the arm wants to bend is cheap stiffness. First hybrid BMX crank we know of.

The rest: hollow 30mm spindle in heat-treated 7075 aluminum, narrow Q-factor, removable spider for any 104 BCD chainring, T47 sealed bearing bottom bracket in the box with a BSA EB30 option. Two-piece, 9/16" pedal threads, right-hand drive.

What we changed on the new one

We changed the forging tool twice during development. Anybody who has paid for a forging die knows what that costs. We did it to pull weight out of the places not carrying load and put strength back into the ones that were. The arm you bolt on is the third shape we made, not the first one that worked.

The other half was rider input. Maris Strombergs, Kye Whyte, Oli Moran, Gaige Gomolicke and Justin Perkins all rode it and fed back. Those five race at a level where a bad crank shows up inside one lap, and I wanted them on it to make sure everything was 100% correct.

The numbers are locked. The Spinners is $399.95. It weighs 739 grams for a 180mm set including the spindle, and it comes in seven lengths from 165 to 180mm.

1,300 Nm, and the testing behind it

959 lb-ft. That is 1,300 Nm in the units most Americans think in, and it is what this crank got pushed to. For a part a 150-pound rider stands on, that is a long way past anything a human will ever put through it.

“That’s more torque than a Cummins diesel puts out.”

The number comes out of two separate dynamic fatigue tests, both run as independent third-party testing to EN 16054:2012, with the machine record also citing ISO 4210-3. Those are the European and international standards for crank fatigue. We did not write them.

The test article was model MDM06-R&L, right arm 30mm / 180mm and left arm 30mm (special hole) / 180mm, in AL 6061-T6 at hardness 61, with a 46T chainring. Both tests ran at 3.0 Hz.

• Test 1, March 26, 2026. Load applied at 45 degrees. 100,000 cycles. Pass. No failure, no visible cracks.
• Test 2, March 31, 2026. Same setup, load at 30 degrees. 100,000 cycles. Pass.

They tested the 180mm arm, the longest we make and the worst case, since a longer arm puts a bigger bending moment into the spindle. Changing the angle from 45 degrees to 30 moves where stress piles up, which is how you find out whether an arm is strong or just lucky in one direction. It passed both, clean. 200,000 cycles of independent data is why I am comfortable telling a parent to put this under their kid. That is data most cranks on the market don't publish, at any price.

How the Shimano DXR is built

The DXR arm is also hollow-forged aluminum, re-engineered off Shimano's Saint mountain bike crank for BMX use. Hollow arm, no carbon component. It runs a 24mm heat-treated chromoly spindle, pressed into the drive-side arm, with steel pedal boss inserts. HollowTech II is Shimano's outboard-bearing bottom bracket system — the bearings sit outside the frame shell instead of inside it, which is the same idea our EB30 option runs on our own crank.

Reported weight runs from the mid-700s to the high-800s in grams depending on length and who is weighing it — Shimano doesn't publish an official number. Available in 165, 170, 175 and 180mm depending on retailer; we stock 170, 175 and 180. Price on our site is $479.95. No chainring or bottom bracket included with ours — check the listing, some retailers bundle a BB and some don't.

The spindle is where these two really split

This is the one to pay attention to. Spindle stiffness scales with the fourth power of the diameter. Going from 24mm to 30mm is a 1.25× jump in diameter, but stiffness climbs by 1.25 to the fourth power — roughly 2.4 times stiffer in the same material. That's the biggest single stiffness gain available in a crankset, and because the spindle is hollow it costs almost nothing in weight.

The Spinners runs 30mm. The DXR runs 24mm chromoly, which is a strong, proven material choice — chromoly has been holding up BMX parts for fifty years — but it's giving up more than 2× the spindle stiffness to the smaller diameter. Steel is also denser than aluminum, so a 24mm chromoly spindle and a 30mm hollow 7075 aluminum spindle end up closer in weight than the diameter difference suggests, even with the smaller bore.

Side by side

Crank length, and why fit beats a spec sheet

The Spinners comes in seven lengths: 165, 167.5, 170, 172.5, 175, 177.5 and 180mm. Three of those are half steps, and you won't find them on the DXR or most cranks at any price. The DXR we stock runs 170, 175 and 180.

If a rider sits between 170 and 175, then 172.5 is not a compromise, it's the correct answer. Too long forces the knee too high at the top of the stroke and the rider loses the snap BMX is built on. Measure the rider before you buy either crank.

My recommendation

Both of these are real cranks built by people who know what a gate start does to a part. The DXR carries a name riders trust and a chromoly spindle with fifty years of BMX history behind that material. If that's the crank in your bike right now and it's working, there's no reason to chase a spec sheet.

But if you're choosing today: the Spinners is $80 less, runs a spindle that's 2.4 times stiffer by diameter alone, ships with a bottom bracket in the box, comes in seven lengths instead of three, and is the only one of the two with independent published fatigue data behind it. That's not a knock on Shimano — it's what happens when you build one part for one job instead of adapting a mountain bike crank to the gate.

Everything else is in the Speedline Parts collection.

Frequently asked questions

Is the Speedline Spinners compatible with the same frames as the Shimano DXR?

Both run a threaded bottom bracket shell setup and 104 BCD chainrings, so in most cases yes. Confirm your BB shell type before ordering either.

Which crank is lighter, the Spinners or the DXR?

They land in the same range. The Spinners is a published 739 grams for a 180mm set with the spindle. Shimano doesn't publish an official weight for the DXR, and third-party listings put it anywhere from the mid-700s to the high-800s depending on length.

Does the Spinners come with a bottom bracket?

Yes, a T47 sealed bearing bottom bracket is included, with a BSA EB30 swap available on request. The DXR is HollowTech II compatible but does not include one.

Why does spindle diameter matter so much?

Stiffness scales with the fourth power of the diameter. Going from 24mm to 30mm is roughly 2.4 times stiffer in the same material, and because the spindle is hollow, the weight cost is small. It's the single biggest stiffness lever on a crankset.

What crank length should I buy?

Measure the rider, don't guess. The Spinners covers 165 through 180 in half-mm steps at 172.5 and 177.5 in addition to the usual sizes, which the DXR doesn't offer. If a rider falls between standard sizes, that's the deciding factor.

And all Speedline Spinner Cranks are available online at https://www.supercrossbmx.com or at your favorite Supercross / Speedline BMX Dealer. A link to search for your closest dealer is here.