Video - 25 mm offset decrease effects explained on our cars
 

I hope this wasn't posted, if so, sorry couldn't find it.

This popular guy explains some math of doing 25 mm spacers on our car.

[ame="https://www.youtube.com/watch?v=j8CCFF3kJPc"]Benefit Of Wheel Spacers On A Subaru BRZ - YouTube[/ame]

I think it is interesting. Any counterarguments from local suspensions gurus? :respekt:
Basically he says that the positive effect of 25mm spacer is negligible, only screws the suspension geometry.

Google on scrub radius. Bearings also may see more wear.

BUT! If someone doing that for 'flush looks', no arguments will convince him to not do it so any arguing is moot.

I had 15mm spacers on the front of my Gencoupe and 25mm rear spacers. I liked the look but not the heavier feeling steering. If you do it, do it for looks.

A 3% increase of track width isn't going to affect anything. And nobody installs spacers to make the car corner better; they do it for looks or to clear suspension or brake components. The only real difference spacers make is to the scrub radius, like churchx said.

I wonder if the video guy has the same opinion about low offset wheels. The very popular TSW Nurburgring 18x8+35 has exactly the same effect as a 17x7+48 with a 25mm spacer.

Nice theoretical argument, better to get "real" user experience with 25" spacers or 35 offset on 8" wheels

DINGDINGDINGDING! We have a winner!

It's almost like the engineers that built these things knew a thing or two about suspension geometries!

Invalid argument.
Car design is all about compromise. I am not suggesting that engineer's don't know what they're doing but they have to make decisions based on the design brief. That is, they have to design within the budget and goals set out for the car. It is not a case of "this is wrong"; it is a case of "doing this to the car introduces what other compromises?". Problems arise when people make modifications not realising what additional stresses are being introduced.

Your argument is suggesting one can't make any safe modifications to a car. (I am not making any specific comment on the use of spacers.)

I'm not suggesting one can't make safe modifications, and being an engineer I know all about compromises in design.

I however would make the claim that decreasing the offset on this car will only compromise the handling dynamics more through increasing the scrub radius. This is a very important detail in suspension tuning that most people overlook. Increasing the Scrub radius will manifest most immediately in increased steering effort, not necessarily a bad thing. However, the car will notably become more unstable under braking in a corner. The car will try to pull the steering wheel to the outside more in corners. The only benefit of the lower offset is increased clearance for wider tires. It's up to the driver to decide if the increase in ultimate grip is worth making the car more unsettled in the transitions

-Josh