SINGAPORE - Modifications made to motorcycle tyres and swingarms may look cool and unique but could be risky for road use.

It is now a trend for small motorcycles below 200cc to have an extended swingarm – a part that attaches the rear wheel axle to the motorbike’s lower frame. Some even argue that a lighter, narrow rear tyre combined with a long swingarm may boost acceleration.

But motorcycle road safety and racing experts have told The Straits Times that such changes are illegal, risky and untested for road use.

Mr Joseph Lee from SBR Trackdays said on Monday: “These are dangerous modifications (for road use). They have become popular only in the past few years, when Malaysia started doing Thai-style drag racing.”

Mr Lee, who organises motorcycle track days for superbikes at the Sepang International Circuit in Selangor, said he witnessed in 2022 two long swingarms break on road-going motorcycles.

“The problem is the (long motorcycle) swingarms are made of soft aluminium,” said Mr Lee. “If a heavy pillion rider sits on the motorcycle, the swingarm may break.”

Mr Aman Aljunied, an assistant manager at the Singapore Safety Driving Centre, said that using non-standard thin tyres may be dangerous as a result of reduced traction on wet surfaces.

“An extended swingarm is a modification of a (motorcycle) frame’s structure which may cause unstable handling in cornering and straight-line riding,” said Mr Aman. “Motorcycle manufacturers have researched and tested their motorcycles’ handling before production, therefore it is best to ride a motorcycle ‘standard’ as sold in the showroom for transportation use.”

The narrow tyres seen on illegally modified motorcycles are slightly wider than mountain bike tyres. Like the long swingarms, narrow tyres can be bought on e-commerce platforms and through Facebook groups.

Mr Norman Lee, owner of motorcycle workshop Race Werks Motor Sports, said such modifications will alter a motorcycle’s handling.

“Workshops should discourage motorcycle owners from doing such modifications because other than a cosmetic upgrade, there is no long-term benefit for the rider,” said Mr Lee.

“These are accidents waiting to happen, when the motorcycle performs poorly over bumps or crashes when going into turns.”

The extended swingarms can be easily bought and installed at late-night motorcycle workshops in Johor Bahru. ST understands that some workshops in Singapore also provide the service.

A motorcycle mechanic at Jalan Tebrau in Johor said he is seeing more young Singaporean customers wanting longer swingarms.

“For under RM600 (S$185), your newly modified motorcycle with a longer swingarm can be ready in a few hours,” said the mechanic, who did not want to be named.

The Land Transport Authority (LTA) said last Friday that it takes a serious view of illegal vehicle modifications, as they could pose safety risks to drivers, riders and other road users.

An LTA spokesman said: “Modifying the rear swingarm of a motorcycle is not allowed as it can affect the manoeuvrability and safety of the vehicle. When replacing the rims of a motorcycle, the size (width and diameter) of the installed rims must conform to the manufacturer’s recommendations.”

The most common types of illegal modifications for motorcycles involve exhaust and lighting systems, said LTA. In 2021, LTA issued 2,740 summonses for these types of modifications, with 1,927 summonses issued in 2022.

LTA also issued 757 and 755 summonses to motorcyclists in 2021 and 2022 respectively for improper or unsuitable tyres. In that same two-year period, 19 and 39 summonses were issued to motorcyclists for rear swingarm modifications.

Some motorcycles with swingarm and tyre modifications can be spotted at Housing Board multi-storey carparks, near late-night eateries and at motorcycle workshops in Jalan Besar.

A food delivery motorcyclist, whose motorcycle has an illegal swingarm modification, said he is currently the only one in his group with the unique swingarm.

“I look at where I’m going and I know how to take bends safely… I do it slowly,” said the rider, who gave his name only as Jasni.

But Jasni would also have to look out for the law as anyone who illegally modifies vehicles can be fined up to $5,000, imprisoned for up to three months, or both.

Penalties for repeat offenders are doubled. Repeat offenders convicted in court may also have their vehicles detained for up to three months, said LTA.

Editor’s note: This article has been edited for accuracy.