[ZPrime]

See subject...

I have an LCI / N55 car, factory software, only mods are a charge pipe and bigger FMIC. Tire setup is slightly embiggened with 275/35 rears, running PS4S currently.

Today it was wet & rainy (not a downpour, but definitely wet road), I pulled away from a stop gradually but then gave it a good bit of throttle. Slight wait while boost loaded and then suddenly tons of wheel hop.

It seems like the moment the wheels try to break loose on this car, rather than simply spinning and/or making smoke, I get fairly violent wheel hop.

I've tried to search but not getting a lot of hits for "wheel hop." Is there a solution to this? Will different suspension help? Some sort of rear subframe brace? It's really kind of ridiculous and also a bit embarrassing...

[NEWTRON]

Are you sure it was wheel hop and not just DSC kicking in? Press and hold the DSC off button for 10 seconds to completely turn it off.

[ZPrime]

It's hop, it happens before the car has yawed at all so DSC wouldn't have any reason to kick in, and I'm not getting any flashing stability / traction indicator on the dash.

I know what DSC intervention feels like, as I regularly drive in snow. DSC braking is way less violent than the wheelhop I get when trying to accelerate hard on low traction.

[David.m]

It's an an issue experienced by many F8X owners though gets more of a mention on the F80/82 forums and most I've read relate to DCT launching from standstill. Common theme is the cause is the diff rotating under load and the fix is installing the diff rear dual mount bracket/mounts. The subframe has provision for the dual mounts but BMW decided to fit just one, no doubt to save $.

I don't do 'launches' (have 6MT) but used to have the wheel hop (& accompanying terrible drivetrain backlash/noise) most notably on climbing tight corners where I'd be modulating throttle to max exit speed (& minimise wheel spin), as the inside wheel lifts and continually looses/regains traction the hop/backlash would happen forcing you to back off in sympathy!

Then at 100K km I had a leaking diff pinion seal so had all three diff seals replaced (leaking driveshaft seals are another known issue) and while there had the shop install the dual mounts. Now in those tight climbing corners I don't get the hop/backlash, the transition between losing/gaining traction in the rear is way smoother and I would guess overall there is more traction.

I went with the Powerflex purple poly bushings/mounts (4 front/dual rear) which did introduce diff whine when cruising 95-105kph. The noise free option is to just add a dual mount bracket & 2nd oem mount (making sure it's the 2018 updated solid rubber one & not earlier oil filled version).

[///MPhatic]

It's common, and will come and go depending on the temp, the tires, the tire wear, precip, etc.

Dual mount bracket for the rear with dual updated OEM black bushings is the most common fix, and introduces no additional NVH, the diff just works properly.

[sdhasher21]

Rear toe arms with eccentric lockout will help and is relatively low cost. Have an f82, but definitely helped settle the rear a bit.

[OG Shark]

Originally Posted by ///MPhatic

It's common, and will come and go depending on the temp, the tires, the tire wear, precip, etc.

Dual mount bracket for the rear with dual updated OEM black bushings is the most common fix, and introduces no additional NVH, the diff just works properly.

Fan of the bracket here as well - but I prefer stiffer bushings so you can enjoy that faux straight cut gear whine

[///MPhatic]

Originally Posted by OG Shark

Fan of the bracket here as well - but I prefer stiffer bushings so you can enjoy that faux straight cut gear whine

It's a glorious sound indeed! But just in case I do swap for a 458 in the future I want the sale of my F87 to be a bit easier, which means black OEM bushings.

[OG Shark]

Originally Posted by ///MPhatic

It's a glorious sound indeed! But just in case I do swap for a 458 in the future I want the sale of my F87 to be a bit easier, which means black OEM bushings.

Indeed one must always keep their priorities in mind when making these kind of decisions - the sale of an F87 should never get in the way of a 458 purchase

[ZPrime]

Originally Posted by David.m

It's an an issue experienced by many F8X owners though gets more of a mention on the F80/82 forums and most I've read relate to DCT launching from standstill. Common theme is the cause is the diff rotating under load and the fix is installing the diff rear dual mount bracket/mounts. The subframe has provision for the dual mounts but BMW decided to fit just one, no doubt to save $.

So is this second mount an OE part, or...? [edit] Looks like Powerflex makes a kit... Turner does too, but I'm not giving ECS/private equity my money (for those who don't know, Turner was bought by ECS Tuning a while back, and that whole hydra is owned by a private equity company).

I don't do 'launches' (have 6MT) but used to have the wheel hop (& accompanying terrible drivetrain backlash/noise) most notably on climbing tight corners where I'd be modulating throttle to max exit speed (& minimise wheel spin), as the inside wheel lifts and continually looses/regains traction the hop/backlash would happen forcing you to back off in sympathy!

I have also never "launched" (mine is also 6MT). If anything, I am paranoid about clutch wear to the point where I probably am too gentle with it; I've never been able to get what I feel is a "smooth but powerful" start with this car. I blame some of this on the stupid clutch delay valve, which I haven't dealt with yet, because I don't have a nearby shop that will do it, and the car is my daily driver so it's hard to be without it so someone can handle that for me.

I notice the hop basically any time I floor it in 1st from lower speeds after doing a brief rollout from a stop. I suspect some of this is because the weight transfer needed to help keep the rear down isn't happening in a "non-launch" scenario.

Then at 100K km I had a leaking diff pinion seal so had all three diff seals replaced (leaking driveshaft seals are another known issue) and while there had the shop install the dual mounts. Now in those tight climbing corners I don't get the hop/backlash, the transition between losing/gaining traction in the rear is way smoother and I would guess overall there is more traction.

I have about 62k miles, and I was told that at least one of my axle seals is "weeping"... I figured if we are doing one we will probably do them all, and if the diff has to come down, we should see if anything can be done about the hop. Hell, maybe the hop is part of what causes the weeping??

I went with the Powerflex purple poly bushings/mounts (4 front/dual rear) which did introduce diff whine when cruising 95-105kph. The noise free option is to just add a dual mount bracket & 2nd oem mount (making sure it's the 2018 updated solid rubber one & not earlier oil filled version).

Normally I don't mind a little bit of NVH, but since the car is currently my DD, I don't think I want to go to something that will add constant noise (a lot of my driving is highway speeds, 60-80MPH).

[///MPhatic]

Originally Posted by ZPrime

I have about 62k miles, and I was told that at least one of my axle seals is "weeping"... I figured if we are doing one we will probably do them all, and if the diff has to come down, we should see if anything can be done about the hop. Hell, maybe the hop is part of what causes the weeping??

Here's the thing, some gasket areas on this car are known to weep, and it's perfectly normal, like the oil pan gasket. However, other parts, like the oil filter housing gasket, or the diff shaft seals are NOT supposed to weep, and are actually leaks. Some dealers replace them under warranty when they are barely leaking (called weeping, but not actually weeping), some wait until there are drips on your driveway, but all have to be replaced at some point, it just is what it is. The dealers that wait are probably waiting for the car to go out of warranty...

Originally Posted by ZPrime

Normally I don't mind a little bit of NVH, but since the car is currently my DD, I don't think I want to go to something that will add constant noise (a lot of my driving is highway speeds, 60-80MPH).

The dual carrier with the OEM 2019+ black bushings is the way to go, zero additional NVH and vastly less wheel hop. However, understand that it's a tire grip/surface/temp thing, so there are still times when you can have a bit of hop with the dual-mount, but it'll be drastically reduced.

[ZPrime]

Originally Posted by ///MPhatic

Here's the thing, some gasket areas on this car are known to weep, and it's perfectly normal, like the oil pan gasket. However, other parts, like the oil filter housing gasket, or the diff shaft seals are NOT supposed to weep, and are actually leaks. Some dealers replace them under warranty when they are barely leaking (called weeping, but not actually weeping), some wait until there are drips on your driveway, but all have to be replaced at some point, it just is what it is. The dealers that wait are probably waiting for the car to go out of warranty...

The "weep" was caught during a brief visual inspection by an independent BMW/German specialist shop about 900 miles from home, who got me out of an unrelated bind during a trip down to the Dragon. I was under the car with them, and I didn't really see anything obvious (looked like general road grime to me), and the car has never left a dot of anything on the garage floor at home... yet. But given how sensitive the diff is (at least based on BMW's insistence that the cooling fins on the housing never be coated e.g. with FluidFilm), I figure I'd be better off getting it taken care of before I see anything on the floor, assuming it actually is seeping.

The dual carrier with the OEM 2019+ black bushings is the way to go, zero additional NVH and vastly less wheel hop. However, understand that it's a tire grip/surface/temp thing, so there are still times when you can have a bit of hop with the dual-mount, but it'll be drastically reduced.

I totally understand there are other variables in play, and I'm not really a guy ripping burnouts everywhere. But the damn thing hops even on snow/ice with snow tires on it, sometimes.

Are the powerflex poly bushings really that bad? They have two sets, one of which they claim is "OE-like NVH"... And is it worth doing the diff front-mount bushings at the same time? (And if so, are the poly a bad idea there too?) Would my LCI car already have the non-oil/solid bushing in the factory location, or did that change not get introduced until the Comp? My car was actually built in summer 2017, delivered in October.

For a sense of tolerance - I ran VF Engineering aluminum + poly engine & transmission mounts on a 2008 VW R32. Had no complaints about those, except the poly failed pretty quickly, and I didn't want to be constantly replacing engine mount bushings. So I switched to DLI Technik, which are 100% metal, with giant springs on them. High frequency noise did make it into the cabin occasionally (mostly, accessory pulley sounds that made you think of supercharger whine), but for the most part they were not bad at all. OTOH, I think I probably only have another 3-5 years left with this car (I'd like to get into a 911 eventually), so I don't want to go too far down the "uncomfortable/performance" slide.

[///MPhatic]

Originally Posted by ZPrime

Are the powerflex poly bushings really that bad? They have two sets, one of which they claim is "OE-like NVH"...

IMO only OE is OE. They're trying to sell you on the fact that once the job is done and there is slight additional NVH you're going to be happy with the performance and live with the trade-off.

Originally Posted by ZPrime

And is it worth doing the diff front-mount bushings at the same time? (And if so, are the poly a bad idea there too?)

Sure, they last a lot longer though, 80-120K generally. As far as poly there, I'd think you're pretty safe with that, but with the OE lasting that long, why go poly?

Originally Posted by ZPrime

Would my LCI car already have the non-oil/solid bushing in the factory location, or did that change not get introduced until the Comp?

It's my understanding that the updated bushings were introduced with the S55 cars. It's easy to tell which you have, just go look underneath.