Wheel Hop and Rear End Shake

[DriftQueen]

So I've been experiencing excessive wheel hop all year which has got progressively worse over the year. First had Indys, then Trefeos (which had it the worst) and now back to primacys which the wheel hop is still present. Got a 2018 BRZ Sport Tech with 27k kms. On top of that a wider wheel setup 17×9 tend to shake the rear end of the car as if the rear wheels are bent (wheels are fine, tried on other brzs no issues and have rotated them to the front with no issues).

I do want to do the whiteline bushing inserts but are the bushings too far gone to save them or they are fine to put inserts on? One shop says there is play in the rear end on the subframe bushings and that the bushings have indentations/ wear on where its been rubbing/compressed from wheel hop. Took it to one dealership and they said it's fine/ normal to have play in the bushings, no repairs are needed, and the reason for the wheel hop is because I don't have stock wheels on.

Is it mainly bushings that help reduce wheel hop? What are some other things I can do to reduce it without voiding powertrain warranty?

Any help or tips would be appreciated!

https://cloud.tapatalk.com/s/5fca02dc..._162140363.mp4

[86MLR]

I used MCA coilovers, MCA traction mod, subframe bushings and diff bush inserts to fix most of it

I did have the hardrace solid diff brace for a while but the NVH was horrible

My advice it to avoid wheel spin by increasing grip or throttle control

[DriftQueen]

Originally Posted by 86MLR

I used MCA coilovers, MCA traction mod, subframe bushings and diff bush inserts to fix most of it

I did have the hardrace solid diff brace for a while but the NVH was horrible

My advice it to avoid wheel spin by increasing grip or throttle control

Seems like gripper tires make it worse for me. Even gradually off a light just daily driving it tends to still hop when i had the Trefeos on. I guessing maybe I had too much grip for the suspension to handle?

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[icybrzzz]

Originally Posted by DriftQueen

Seems like gripper tires make it worse for me. Even gradually off a light just daily driving it tends to still hop when i had the Trefeos on. I guessing maybe I had too much grip for the suspension to handle?

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Stop missing 3rd and learn to drive

[Racecomp Engineering]

Do you have a better picture of the rear diff bushings? That's 27k kilometers?

- Andrew

[DriftQueen]

Originally Posted by Racecomp Engineering

Do you have a better picture of the rear diff bushings? That's 27k kilometers?

- Andrew

Yes 27k kilometers. Ill take a better picture later today and post it.

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[DarkPira7e]

In my opinion, there are 4 main contributors- the transmission mount allowing the transmission to hop around, the differential upper mounts, the subframe mounts, and the rear facing differential bushings. I also noticed once I stepped up to 200TW tires, if my tires spun in the rain I'd get insane wheelhop.

I don't know much about warranties, but if you can upgrade these with subtle aftermarket pieces that are also black ( Torque solutions and Whiteline both offer black bushing replacement options I think), and the STI transmission mount, I doubt anyone would be the wiser. The wheel hop is a culmination of things moving, and replacing one piece will only restrict the movement of another and accelerate wear. I hate to resort to all or nothing thinking, but it sometimes does more harm than good to only replace one piece of this puzzle.

With that said, my recommendation stands; Trans mount, upper diff/subframe bushings and rear facing diff bushing. That should provide equilibrium and cut out much of the wheelhop.

[strat61caster]

That bushing looks practically brand new. You're just seeing superficial surface imperfections from the casting and the other shop must be hungry for more work.

imho I added whiteline rear subframe poly inserts and then differential bushing poly inserts. As above it's a weird balancing act, I found much less hop on adding the subframe inserts and then about a month later adding the differential bushings actually brought back some wheel hop and harshness, maybe stiffening the trans mounts would help, but I'm more inclined to remove the front differential bushing inserts to allow that to move more freely and reduce the nvh from the diff gears meshing. I'd say try one set at a time if it's not too inconvenient to do so, install is fairly easy if you're dilligent but some people have fucked up the threads on the chassis so go slow and don't force it.

[Ohio Enthusiast]

Originally Posted by strat61caster

maybe stiffening the trans mounts would help, but I'm more inclined to remove the front differential bushing inserts to allow that to move more freely and reduce the nvh from the diff gears meshing.

I'd share my experience - I did Whiteline trans insert and rear trans mount bushing together. Then I did the rear subframe inserts. Then I did the rear differential inserts and finally the front differential inserts.
I felt that there was improvement in every step except for the rear diff inserts alone - the rear diff inserts alone didn't do much. Only once I added the front diff inserts did the drive train slop disappeared almost completely. I was actually surprised a little how much more noticeable the front diff inserts were than the rear diff inserts.
Wheel hop is still present if I try to accelerate hard from a stop in the wet, but not in the dry. Added NVH is mostly noise, but it's not bothersome for me.

[NoHaveMSG]

I still get hop sometimes with 200TW tires.

SPL solid mount subframe inserts
Whiteline outrigger bushings on diff
Cusco diff brace
RacerX LCA's with sphericals
Whiteline transmission inserts
STI Motor mounts

[DriftQueen]

Originally Posted by Racecomp Engineering

Do you have a better picture of the rear diff bushings? That's 27k kilometers?

- Andrew

It looks like only the one has some surface rubbing. The others are perfectly fine just has "play". The wheel hop only happenson the left side. Right tire grips or slips/spin while the left side hops.

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[DriftQueen]

Originally Posted by DarkPira7e

In my opinion, there are 4 main contributors- the transmission mount allowing the transmission to hop around, the differential upper mounts, the subframe mounts, and the rear facing differential bushings. I also noticed once I stepped up to 200TW tires, if my tires spun in the rain I'd get insane wheelhop.

I don't know much about warranties, but if you can upgrade these with subtle aftermarket pieces that are also black ( Torque solutions and Whiteline both offer black bushing replacement options I think), and the STI transmission mount, I doubt anyone would be the wiser. The wheel hop is a culmination of things moving, and replacing one piece will only restrict the movement of another and accelerate wear. I hate to resort to all or nothing thinking, but it sometimes does more harm than good to only replace one piece of this puzzle.

With that said, my recommendation stands; Trans mount, upper diff/subframe bushings and rear facing diff bushing. That should provide equilibrium and cut out much of the wheelhop.

Awesome. Going to go with the whiteline inserts. I still daily the car so just trying to find a good balance.

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[DriftQueen]

Originally Posted by strat61caster

That bushing looks practically brand new. You're just seeing superficial surface imperfections from the casting and the other shop must be hungry for more work.

imho I added whiteline rear subframe poly inserts and then differential bushing poly inserts. As above it's a weird balancing act, I found much less hop on adding the subframe inserts and then about a month later adding the differential bushings actually brought back some wheel hop and harshness, maybe stiffening the trans mounts would help, but I'm more inclined to remove the front differential bushing inserts to allow that to move more freely and reduce the nvh from the diff gears meshing. I'd say try one set at a time if it's not too inconvenient to do so, install is fairly easy if you're dilligent but some people have fucked up the threads on the chassis so go slow and don't force it.

I first did the diff bushings. It improved alot and was getting the Gear whine. 2 weeks later now did the subframe bushings, gear whine has become less noticeable but has brought back some initial wheel hop (different and more "softer" feeling then stock) is alot more planted when not hopping. Seems though now the transmission or gearbox moves more as its mostly noticeable in the shifter so going to try transmission insert next to see if that balances the car out again but so far major improvement. Love the stiffer ride quality.

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[Grady]

If you want to eliminate wheel hop you have to lock down everything front to back. I started at the rear Whiteline inserts in subframe and diff. This helped then when to transmission mount, not much difference. Then torque solutions engine mounts and all hop went away. To eliminate hop you will have to increase NVH a lot. In retrospect starting at the front probably would have eliminated more hop quicker.