Piston Slap: The Fallacy of Aftermarket Performance?

Sajeev Mehta
by Sajeev Mehta
piston slap the fallacy of aftermarket performance

Evan writes:

Hi Sajeev!

How do people get your name wrong when it is in your email address? But that wasn’t why I was calling. My question: are aftermarket parts for brand spanking new cars sensible?

For instance, I’m picking up an Audi SQ5 and there are these ‘x-brace’ things and mount inserts. Why would Audi not have engineered it well enough in the first place? Money savings? They didn’t think whatever attribute x-braces add was ‘for’ the SQ5 demographic?

Or are companies selling mount inserts and eXtra bracing to people with $60k sport-crossoverUVs selling snake oil?

Thanks for the insight!

Sajeev answers:

You can’t make generalizations — except about the horrible people calling me Sanjeev even though my name’s been plastered all over TTAC since March 2006…but I digress.

Vehicles are designed to a certain expectation of performance, ride quality, cost constraints, and acceptance to a wide variety of consumer preferences. Aftermarket performance modifications can do better than factory stuff.

But some are worse than other aftermarket alternatives, especially against those of a creative and grassroots racer nature. Sadly, many (either by themselves or in a package) only make a difference to the owner’s perception of vehicle performance and some parts are worse than what came from the factory (i.e. oversized throttle bodies on a naturally-aspirated motor). Take it from the guy that loves tweaking RWD Fords: every scenario above is true.

It’s like walking through a metaphorical minefield: keen research, trusted advisers with years of hands-on experience, and hours of internet forum digging are mandatory to sort fact from fiction.

So, shut up and tell us, what’s the scoop on these SQ5 bits? Well, I’ve never driven said vehicle…

However, I rather like those billet aluminum bushing inserts, even though billet and anodized finishes are often overpriced flash. Yes, many forms of motorsport require such fancypants materials, but that doesn’t apply to the SQ5. Flash doesn’t sell me; tangible improvements in performance does. To wit, these babies likely improve performance out of the hole, especially with an aftermarket computer tune bumping up performance, reducing torque management and perking up throttle response.

Yet I wonder if there’s a universal fit, solid (rubber or invasive polyurethane) bushing you can buy from a catalog (or from another VAG product) — which might be like, waaay cheaper, son.

And since a new Audi is far from the flexi-flyer chassis of my beloved Fox Ford products, I question the value of any chassis improvement on a higher dollar luxury car, much less a billet aluminum one. Does it stiffen the chassis and improve feel enough to matter? Maybe it helps NVH control. Perhaps handling is more confident with other modifications. Odds are, though, it won’t make the SQ5 any quicker on a track.

Consider, if you will, improving the factory part: adding metal (perhaps triangular sheetmetal between the weak points?) welded it up by someone familiar with roll cages. Perhaps that aftermarket part is a good template. That’s more labor and it won’t be billet aluminum pretty…but, right or wrong, it’s the other side of this coin.

Don’t forget one other important fact: modifications are worth pennies on the dollar in the vehicle resale department. Many will lower the value as stock vehicles are preferred at trade-in time. The SQ5’s bits add curb appeal for buyers motivated to get on their hands and knees to see them, which amounts to precisely nobody in the used car market.

Don’t get me wrong, I love modifying cars with cool aftermarket bits, but it boils down to two words: buyer beware.

[Image: Shutterstock user Dezay]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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3 of 76 comments
  • Shappy Shappy on Aug 01, 2015

    One factor that I don't believe has been mentioned is that of crash safety. Most vehicles are now designed to absorb energy in a holistic manner. A little give here and there throughout the vehicle can add up to a lot of energy absorption during an impact. If you remove some of that give with stiffer braces and/or bushings, you might end up transferring more forces to the passengers, in the event of a crash, resulting in a greater chance of injury.

    • Rpn453 Rpn453 on Aug 01, 2015

      The scale of the changes being made compared to the strength of the related structures and components is miniscule. It's like adding a hundred pounds of piping to the underside of a structural beam supporting 100,000 pounds of equipment. No detailed engineering is necessary.

  • Ronnie Schreiber Ronnie Schreiber on Aug 01, 2015

    The stock US market Audi SQ5 handles very well, remarkably so for something so high off of the ground. The suspension is good enough that Porsche pretty much uses it as is on the Macan platform mate. I thought it handled better than the A6 that I drove back to back with it. I'm enough of a boy racer that I put sport springs on my Saturn but I see no reason to mess with the SQ5's bits that keep it on the road.

  • Aidian Holder I'm not interested in buying anything from a company that deliberately targets all their production in crappy union-busting states. Ford decided to build their EV manufaturing in Tennessee. The company built it there because of an anti-union legal environment. I won't buy another Ford because of that. I've owned four Fords to date -- three of them pickups. I'm shopping for a new one. It won't be a Ford Lightning. If you care about your fellow workers, you won't buy one either.
  • Denis Jeep have other cars?!?
  • Darren Mertz In 2000, after reading the glowing reviews from c/d in 1998, I decided that was the car for me (yep, it took me 2 years to make up my mind). I found a 1999 with 24k on the clock at a local Volvo dealership. I think the salesman was more impressed with it than I was. It was everything I had hoped for. Comfortable, stylish, roomy, refined, efficient, flexible, ... I can't think of more superlatives right now but there are likely more. I had that car until just last year at this time. A red light runner t-boned me and my partner who was in the passenger seat. The cops estimate the other driver hit us at about 50 mph - on a city street. My partner wasn't visibly injured (when the seat air bag went off it shoved him out of the way of the intruding car) but his hip was rather tweaked. My car, though, was gone. I cried like a baby when they towed it away. I ruminated for months trying to decide how to replace it. Luckily, we had my 1998 SAAB 9000 as a spare car to use. I decided early on that there would be no new car considered. I loathe touch screens. I'm also not a fan of climate control. Months went by. I decided to keep looking for another B5 Passat. As the author wrote, the B5.5 just looked 'over done'. October this past year I found my Cinderella slipper - an early 2001. Same silver color. Same black leather interior. Same 1.8T engine. Same 5 speed manual transmission. I was happier than a pig in sh!t. But a little sad also. I had replaced my baby. But life goes on. I drive it every day to work which takes me over some rather twisty freeway ramps. I love the light snarel as I charge up some steep hills on my way home. So, I'm a dyed-in-the-wool Passat guy.
  • Paul Mezhir As awful as the styling was on these cars, they were beautifully assembled and extremely well finished for the day. The doors closed solidly, the ride was extremely quiet and the absence of squeaks and rattles was commendable. As for styling? Everything's beautiful in it's own way.....except for the VI coupe....it's proportions were just odd: the passenger compartment and wheelbase seemed to be way too short, especially compared to the VI sedan. Even the short-lived Town Coupe had much better proportions. None of the fox-body Lincolns could compare to the beautiful proportions of the Mark V.....it was the epitome of long, low, sleek and elegant. The proportions were just about perfect from every angle.
  • ToolGuy Silhouetting yourself on a ridge like that is an excellent way to get yourself shot ( Skylining)."Don't you know there's a special military operation on?"