Motorcycle Modifications: Wheels of Change
Whether for cosmetic or dynamic reasons, changing the wheels on your motorcycle can be one of the most rewarding experiences. Both in the way that it makes the bike look, and in the way that it rides too.
In as far as performance gains are concerned, aftermarket lightweight wheels or, indeed, later model factory fitment wheels can give gains in acceleration, quicker turning and improved suspension performance. Remember, modern wheels are significantly lighter than those produced even a handful of years ago.
And, for older models, they also give the opportunity to fit gripper and stickier and, perhaps as notably, popular (i.e. easily available and more competitively priced) rubber.
And this is the very reason why we see later model cast (or forged) aluminium wheels fitted to bikes such as big air-cooled Kawasaki and Suzukis. But we mustn’t ignore the fact that many people opt for different wheels for stylistic reasons. A bike from the Eighties, with an eighteen or nineteen inch front wheel, and maybe even a fifteen or sixteen inch rear (certainly on ‘factory custom’ bikes) will not only benefit from the improved traction of modern seventeen inch radial tyres, but also look a damn sight cooler with the newer wheels and rubber. And a set of contrast-cut, anodised and polished rims add as much style and poise to a factory cruiser as carbon fibre or magnesium race wheels do a race-rep.
But a wheel swap, despite its advantages, isn’t without its issues.
Starting with the simplest and easiest – although not necessarily the cheapest – we have bikes with spoked wheels that can simply have a different rim laced on to the hub. This is the principle behind most supermoto conversions in which a motocross, enduro or trail bike has it’s off-road sized wheel rims (normally 21” front and 16” rear) replaced with slightly wider 17” diameter rims.
As the standard hubs are retained, the standard brakes, whether they’re drum or disc, are still used, and the only real issue is whether there’s enough chain clearance at the rear, as an ex-dirt bike will usually only have just enough room to squeeze in a 150 section tyre, although occasionally a 160 section will fit.
The end result of a supermoto conversion is a bike that has a lower seat height, has quicker steering, and enough cornering grip to create some serious footpeg / tarmac interference issues. And is more fun than a weasel in gym socks.
The extremest form of upgrading in the tyre width stakes is one that is especially popular on the other side of the Atlantic, and also has a few followers in Europe too – that of the fat-tyred sportsbike. A 240 section tyre is common and thought of as being the sportiest option, although 300 or even 330 section tyres are being used. Occasionally a 360 section ring will be fitted, but they’re really not recommended for anything with a power output capable of pulling the skin off a rice pudding.
Although tyres wider than those on an average saloon car can be used, it’s the radical ‘wagon wheel’ hoops that’re currently proving popular in the US of A, particularly in the current fad of baggers. They’re not especially wide in section, but boy are they tall! Wheels as large as thirty inch diameter rims are being used at the front, which means that, even with off-the-shelf bolt-in wheels, there are further issues in the form of clearance between the wheel and bottom yoke, meaning that some suspension modification will also be necessary.
While actually fitting different wheels into the standard forks and swinging arm isn’t generally much more fuss than changing the bearings to suit the axle, or using spacers to account for any difference in size or width, further issues can occur, for example at the rear thanks to swinging arm clearance, and chain alignment and clearance.
The internal width of a swinging arm is only really going to be a problem if you’re attempting to shoehorn a 180 section rear tyre into a skinny single cylinder bike. Chain clearance is far more likely to be of concern. Offset drive sprockets can be acquired, and rear wheel cush drives / sprocket carriers can be machined to suit, but you also have to be aware that the lower rear frame rails may be in line of the intended chain run too. It’s something of a juggling act, but far from an impossibility for anyone with a engineering bent!
There’s also the factor of brake discs. If the standard forks are being used, standard discs may not fit the new wheel and, in turn, the standard calipers probably won’t fit either. It’s not so much of an issue at the rear, as a standard caliper hanger can be modified to suit, or a bespoke one fitted.
At the front it’s rather more complex, but it can be resolved by using bespoke caliper brackets. Although, of course, it is an issue that doesn’t exist if you happen to be fitting a complete front end, which is something that we’ll be looking at next time…
IMPORTANT NOTE: It’s essential to speak to your insurer before you make any modifications to your motorcycle so you can understand the policy implications. Some modifications will dramatically increase your premium, and other modifications might make it very difficult for you to find a company that will insure you at all.
Failure to disclose any modifications can also result in your insurer refusing to pay out on a claim, especially if the modification contributes to the claim. Check our extensive guide to modifications and accessories, how they can impact your insurance and much more.
Always do your research properly, consult an expert, speak to your insurer and make sure you’re fully informed of the risks involved of your proposed modification. Modifications should always be done to a professional standard and maintained appropriately.