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M8 Carbon Fibre Conversion

This Modification Is Truly Amazing

Doc Robinson Associate/Technical Editor Heavy Duty magazine (Australia)

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I’m struggling. Because it is difficult to portray in words how the rider, who’s fitted carbon fibre wheels, can instantly feel changes in unsprung and especially rotational weight. How can I describe how much better the brakes suddenly work? Or how much dramatically lighter the bike feels around corners? How the suspension suddenly feels smoother over small bumps, while feeling more controlled and responsive over larger ones?
I’m also struggling to keep the crazy shit-eating grin off my dial every time I roll out of my driveway. You see every curve and corner is a delightful experience, as I swoop through them with a flickability and stability never previously experienced on a 353 kg (778 lbs) bagger. Or any Harley for that matter. Like wow! This modification is truly that good.

But the incredible transformation in the handling of my bike is contributed to, in no small measure, by the Brock Performance alloy swing arm, a beautifully machined unit that is both aesthetically pleasing and superbly constructed; a mechanical work of art that has managed to combine form and function seamlessly.

Of course, I had been aware of the benefits of reducing unsprung weight for a long time, but it wasn’t until Sturgis 2019 that I became aware of the very fast growing popularity of performance baggers, bikes ridden hard and fast for big miles.

And, in one of several chats with Brock Davidson, head honcho of Brock’s Performance in Ohio, it was explained to me how his interest in becoming involved in performance products for Harley-Davidsons came about, after years of focussing on high performance Japanese models.

It seems that some of his buddies were stepping off their Yamahas, Suzukis, Ducatis and so on and throwing a leg over Harleys. And while generally happy with the Motor Company bikes’ comforts, were very dissatisfied with the performance. Which led to many requests that Brock put some effort toward helping Harley riders to take their riding enjoyment to another level. Which he has done in fine style, and now offers a brilliant range of products from his own extensive range as well as from leading manufacturers.

There are some great guys in the Harley aftermarket industry and Brock is one of them, who’s impressive drag racing history includes becoming the first rider of a street legal motorcycle to run into the seven-second zone (quicker than 8.00 seconds) over the quarter mile. I was fortunate enough to sit with him at the annual Hamster Dinner at Spearfish last year and over several hours got a great insight into his mindset. It says something about him that he trademarked the term ‘Stupid Fast.’

By the end of the night we had worked out a deal where he was going to supply me parts for the Milwaukee Eight bagger that I had recently purchased from Brumby. These included BST carbon fibre wheels, which don’t come cheap, but the benefits are amazing. As one leading Aussie bike journo said after fitting them, “the benefits are so great and varied, affecting so many aspects of the bike, that they are worth every cent”.

Blair Freeth’s Adelaide Harley-Davidson Bike Works was my choice for the fitment of these items and long time Harley-Davidson technician Craig Carling got the task. After removing the stock exhaust, rear wheel and stock swing arm he prepares the BST rear rim for tyre fitting.

And now fits a new tyre to the BST rear wheel.

The new swing arm fitment begins.

With the wheel now in place, Craig inserts the new axle.

After having adjusted the belt tension, having snugged up the axle nut it is time to approach fitting the front wheel. Before doing so, however, Craig weighs it, as we did earlier with the rear wheel. The stock front wheel weighed in at 10 kgs, whereas the BST was only 6.5 kgs - a substantial saving. The stock rear wheel came in at 8.5 kgs with the BST at 6.5 kgs. The stock swing arm weighed 10 kgs whereas the Brock unit was just on 5 kgs. In total that added up to a substantial 11.5 kgs (25.3 lbs) in unsprung weight.

At the time of fitting these wheels the bike was still registered in Victoria and to get it re-registered here in South Oz I had to present it for a numbers inspection, which necessitated fronting up with stock mufflers. Which caused a minor problem, as the stock mufflers were a touch wide.

So with the aid of an oxy torch and a hammer a minor modification was made. And after successfully passing the government inspection an aftermarket pair of mufflers was refitted.

As I stated in the first paragraph, the ride is now sensationally improved. For bagger owners wanting more performance, I would put fitting these wheels and the Brock swing arm ahead of any engine mods. Seriously.


Now Brock highly recommended World Wide ceramic bearings for these wheels and there is a considerable amount of great information on these bearings on Brock’s web site including a torture test video well worth a look. In summary, these ceramic bearings are some 60 percent lighter than conventional bearings and exhibit 40 percent less friction. Technically, they are a hybrid, with steel outer and inner races that contain the ceramic ball bearings. A normal steel bearing can fail at around 300 degrees F, whereas these can take up to 2000 degrees F. They are 30 percent denser and thus can take more load and have a lifetime of between three to five times that of conventional steel bearings.

Brock Swing Arm
Normally motorcycle swing arms are far from being viewed as objects d’ art, with their design and manufacture generally putting function well ahead of form. But for this Brock beauty, I make an exception, seeing well above average aesthetic beauty in its design and construction. And as for function, it’s a bloody ripper!

I thought it worth sharing a little of the engineering that goes into its construction.

Betty’s Back!
Long time readers will remember that beginning quite some years back I named all my baggers “Betty”. This began when the song Black Betty was hot on the airwaves and I named my first bagger “Black Betty”. Then along came an orange CVO that naturally became Orange Betty. Betty da Silva followed and then Ugly Betty. This latter name was conceived as my bike was the first Road Glide to be imported into Oz and there was resistance against the look of the shark nosed fairing. But I had fun with the various Betty’s and now - having taken this one over from Brum - I’m renaming her Betty Redux.
This is our light breathable ballistic Nylon vest with leather trim. Click and check it out and all our cool leathers.
This is our light breathable ballistic Nylon vest with leather trim. Click and check it out and all our cool leathers.

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Reader Comments

Great stuff Doc.

Thursday, October 22, 2020

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