Wheel upsizing (wider tyres + larger rims + wider offsets) and ride lowering are very commonly seen vehicle modifications. Many do so primarily for aesthetics and do not understand how these modifications affect handling. They think or hearsay they are improving their vehicle handling, but they are not.
When tyre widths and wheel offsets change, suspension geometry is altered. Handling can be, and is almost always (if done cheaply) affected negatively — unless the manufacturer had set up the suspension poorly to start with.
Price, size or performance? Choose two.
Wider tyres can provide more grip but hurt fuel economy. The fact is that most people barely drive their vehicle to its limits. Worse even, some upsizers may compromise with cheaper tyres as larger tyres are significantly more expensive, so the effects of wider tyres may be completely negated by cheap tyres.
Adding on to the list of grave mistakes, many actually ditch their heavy but sturdy stock wheels and opt for cheap wheels that are touted to be light, hence fuel economical. Little did they know these cheap lightweight wheels may crack easily. Good quality forged wheels are extremely expensive.
Assuming all goes well and high quality rims and tyres are purchased, the list of mistakes do not end here.
The usual theory goes: wider track and lower car = better handling, right? Not entirely correct.
Here’s why.
1. Wider track causes softer suspension. When wheels (offset) go further outboard, load on the suspension increases and as a result the ride becomes softer. To compensate, stiffer shocks and springs are needed. BMW, for example, would sell cars with staggered and non-staggered wheels. When opting for a staggered setup, the rear track becomes narrower because the staggered rear wheels are heavier. This compensates for suspension loading and also reduces understeer (wider front track = less understeer). Unknowing BMW drivers who opt to use spacers on the rears instead of installing proper staggered wheels are actually making their handling worse.
2. Lowering springs? Need new shocks. When lowering springs are used without matching shock absorbers, the shock absorbers will wear prematurely and not perform optimally. Shock absorbers are designed to work within a nominal ride height and lowering causes it to work outside of its designed parameters. Lowering springs are also typically stiffer to prevent the lowered car from bottoming out easily. Shocks and springs that are mis-matched will result in a bouncy or unsettled ride. Again, this negatively affects handling.
3. Rubbing fender? Too low! Wider offsets and excessively lowered rides may cause wheels to rub against fenders. When most people experience a rubbing problem, they tend to return to the tyre shop. The solution offered is usually a recommendation for lower profile tyres or sometimes even narrower tyres resulting in stretched sidewalls. Doing so affects the speedometer, odometer and fuel economy readings. The right thing to do is to raise your ride height and get a proper set of coilovers.
4. Bottoming out? NEVER use spring stiffeners! Excessive lowering and poorly set up suspension will cause the vehicle to bottom out easily. That’s because most lowering springs are not very much stiffer than stock springs and cannot cope with the extra load and reduced travel. I have heard of “spring stiffeners”. These are basically blocks or “retainers” sitting in-between several coils of springs preventing them from compression. Doing so is NOT recommend — for your own safety! It will cause uneven stress across the spring and a broken spring can be disastrous. Get a proper set of coilovers!
5. Lowering can actually lead to more roll. Most people do not understand the relation between roll center, instantaneous center and CG. When a vehicle is lowered, the CG of a vehicle may be lowered but the roll center could actually move further away from the CG. This creates an increased lever effect making the car roll more even though it is closer to the ground. The result is sluggish handling. The easy fix is to install stiffer suspensions but that has an effect on tyre load. The ideal fix is to correct the vehicle roll center by modifying suspension arms.
6. Increased track? Steering and braking may be compromised. When track width is increased, scrub radius is reduced especially for FWD/McPherson strut vehicles with -ve scrub. A small change in scrub radius can significantly alter steering feel and braking stability. The change in steering weight or sensitivity (“twichiness”) is usually mistaken for better handling. Most will never realize that they may have also compromised braking stability because it is never tested.
7. Excessive lowering causes camber issues. Most road cars do not have adjustable camber in the front. Without compensating for the increased -ve camber when lowering, tyres are subject to premature inboard wear. Change in camber can also affect a vehicle’s understeer/oversteer character, especially for cheaper FWD cars with torsion beams in the rear — camber angles do not change at the back when lowered. Excessive lowering will even cause +ve camber gain on most vehicles with McPherson strut front suspension. This will cause cars to actually flip over in an aggressive corner. Here’s a video I found on YouTube showing how the camber changes across suspension travel.
Strut Suspension Camber Behavior.
To properly lower a vehicle and increase its track width, a lot of modifications are required and mostly requires a complete overhaul of the suspension components. For most people, it’s just not worth the money.
The cheapest way to improve handling on a normal day-to-day vehicle is to install a good set of tyres and proper brake pads. Most stock brake pads are too soft (adhesive type) because they are designed to work in cold (read: snow) weather. We do not have cold weather here in Singapore. Switching to a harder (abrasive type) pad will drastically improve braking performance. The only downside is that the brake rotors will wear faster and the brakes might squeal if not bedded in properly. Also ensure tyres are properly inflated — it makes a world of difference.
Tyre inflation tip: Add more pressure to the front tyre and reduce in the rear. Most cars, even RWD ones, are designed to understeer right out of the factory. A slight change in pressure (+/- 2psi) will alter its handling character.
I hope this has benefited you and saved you some money you should never have spent. Safe motoring!