Imdomina

Replaced 19" factory cavos (had 255/19/35 Contisports) with new rotary forged 20X10s with Pilot Sport 4S 275/20/30s. Grip has increased and handling on perfect pavement is outstanding.

When going around a bend in the road on uneven pavement with the cavos, the car and wheels felt like they were tracking together all heading in the same direction. On the new wheels, it feels like all 4 corners are heading in different directions as the wheels deflect or flex as each crosses over their own particular crack in the road. This effect is particulary unnerving on a wet road.

It seems like the factory wheels were more "solid" where the new RF units are flexing and prone to get rung like a bell when hitting imperfections in the road.

So two questions: 1) does this make any sense to anyone and 2) would monoblock forged wheels likely not deflect and flex like the RF ones? It would be one heck of a gamble to fork over $4K plus for forged wheels only to have the same characteristics.

For reference, the RF wheels are made by one of the more popular manufacturers. Not trying to throw shade, so not naming the company. Set of 4 were $2500 and that was a good price. RF wheels are 4 lbs heavier per wheel than the cavos (edit -> also have ECS 2 piece rotors in 4 corners reducing weight ~4 lbs each. Unprung should be close to stock) . OD is basically the same.

Burrcold

There's a lot to unpack here. Going from 19 to 20's will change the characteristics on their own, let along going from a 255 to a 275 wide tire. Then you are adding in a change in unsprung mass, and a completely different tire. All of that being said, you shouldn't notice such an unsettling feeling, especially since you stayed within the OEM(ish) specs for a wheel setup. What tire pressure are you running with the new MPS4s's? Did you get the alignment done? Both important factors.

Imdomina

Thanks for the quick reply. Yeah, tried to stick to OEM specs, knowing a 20" wheel with 265/30/20 tires is a factory option. With a 275 tread, just barely wider than OEM.

Tire pressure around 38 in all 4. No alignment but tires are wearing evenly (it's been 5 months) and the car tracks perfectly straight with hands off the wheel.

Overall impression is the RF wheels flex and bend under stress and the cavos didn't. Running over cracks often feels like the wheels are getting rung like a gong. Wondering if monoblocks would be a big improvment.

Miss my R8

Tramlining - I'd also drop the pressures a bit!

JohnEnglish

Also, don't forget that the face of rotary forged wheels are still cast.

Imdomina

Yep I know. It's like the face is secure against the hub and the huge ring of aluminum is flexing on imperfections in the road. Really wiggles around bends with uneven pavement. Will get an alignment now but don't have my hopes up.

superswiss

To be honest, I've never experienced what you are describing, but I have to say $2500 for 4 forged wheels is a cheaply wheel. Good forged wheels will run you that per wheel. When it comes to wheels, you get what you pay for. One of the main points of going with forged wheels is reduced unsrpung weight. You've gone the opposite direction with your new wheels being heavier than the old cast wheels, and the bigger, fatter tires added even more weight. Because of the increased strength of forged alloy, they require less material for the same strength as a comparable forged wheel and the result is that they are lighter which is what you want. However, keep in mind that the suspension of the car was tuned for the original wheels, so a lighter or heavier wheel will affect how the suspension handles.

Imdomina

They're rotary forged and I'm considering (based on feedback) spending the extra money for forged.

Forgot to add I put ECS 2 piece rotors on all the way around reducing unsprung by about 4 lbs each. New tires same weight as old Contis. Unsprung weight and OD (with skinnier sidewall) are very close to stock.

superswiss

Rotary forged is the same as flow formed, hybrid forged or a bunch of other marketing names that are used to described them. They are a slight improvement over cast wheels, but not nearly at the level of forged wheels. Not only is true forging a much more involved and controlled process, but forged wheels typically use aerospace-grade alloy, but as said, you pay for it. You are looking at upwards of $8k for a full set of properly forged wheels. Anything below will be imitation.

Burrcold

Maybe OEM forged, but there are several good brands that you can get a fully forged, good quality wheel from (Ex. Apex forged wheels in 20 inch diameter are roughly $3.5-4k depending on the model.