Stop wheel hop 1989 FC

[weezer]

Is there an easy fix for wheel hop in 89 convertible when coming off the line?

[weezer]

After owning 2 corvettes, I love my VX7 vert. Drove it out of curiosity and fell in love with the ride, handling and overall build quality. But the wheel hop is a disappointment. Struts and bushings are in good shape. has anyone else had this problem? Suggestions??

[josh18_2k]

i have all all quality crap in my suspension, and it still hops sometimes. not nearly as bad as with original bushings, but its not completely gone either.
there are a bunch of things you can do to reduce it, but it'll probably never go away:
solid rear diff mounts with collars (custom part- basically filling the gap between the crown and the diff on the rear mounts with a hockey puck or aluminum or whatever), subframe mounts, stiffer shocks, make sure theres no excess play in the diff

[weezer]

Thanks Josh. the differential mounts are the only thing I haven't checked. will do that ASAP. The design of the rear suspension isn't the brightest idea from mazda. It pulls the body down on acceleration, instead of pushing up to get more traction. On regular leaf springs I have used traction bars, but the way the RX7 is built, it doesn't look to be easily done.

[RXTASY]

The best thing to avoid wheel hop is sticky tires.

[My5ABaby]

The best thing to avoid wheel hop is sticky tires.
Or drop in an N/A 13b. :rofl:

[NoDOHC]

Actually, I have found that adjusting the rear shocks stiffer will actually improve wheel hop (I had serious issues with it before). Setting KYB AGX shocks at 8 seems to fix the issue almost entirely.

This is actually the opposite of the setting required for maximum weight transfer and minimum axle hop on a solid rear axle car.

I think that weight transfer is not as good with the stiff shocks, but the car still launches at >1g with factory size tires on it.

[RETed]

Thanks Josh. the differential mounts are the only thing I haven't checked. will do that ASAP. The design of the rear suspension isn't the brightest idea from mazda. It pulls the body down on acceleration, instead of pushing up to get more traction. On regular leaf springs I have used traction bars, but the way the RX7 is built, it doesn't look to be easily done.

Wow, calling a bunch of engineers "stupid" isn't exactly bright either...

The car wasn't made for drag racing.
Thinking it is isn't too smart on your part.

What I'd like to know is why the F*CK are you trying to drag a convertible, which has the crappiest set-up to do this in the first place?
(i.e. 3.90:1 stock rear end?)


-Ted

[Whizbang]

it might just be me (or physics) but isnt the downward motion of the body relative to MORE traction due to the weight transfer vectoring forces down onto the wheels?

[RETed]

Yes, if we're strictly talking about dynamic loading forces of the chassis while ignoring the dynamics of the rear suspension.
The reality is with the K-M hub design of the trailing link rear + the DTSS crap, you get additional changes in toe and camber, while is detrimental to getting as much traction in the rear on a hard drag launch.


-Ted

[josh18_2k]

lots of squat = good
camber gain with squat = bad

so it kinda evens out to being pointless. every suspension design is "stupid" compared to wishbones, but we get what we get.

[Whizbang]

+1 for FB? lol

[Lastphaseofthis]

Wow, calling a bunch of engineers "stupid" isn't exactly bright either...

The car wasn't made for drag racing.
Thinking it is isn't too smart on your part.

What I'd like to know is why the F*CK are you trying to drag a convertible, which has the crappiest set-up to do this in the first place?
(i.e. 3.90:1 stock rear end?)


-Ted
I tough all verts had a 4.1 because of the weight? even those with auto trannys, although the auto coupe's have a 3.909, or do i have it backward?
Sorry i'm to lazy to jack up the vert make some marks and spin the wheels...

[RETed]

All US-spec convertibles should have the 3.9 rear end.
The 3.9 compensates for the auto trans and increased weight to comply with CAFE mileage rules for Mazda.


-Ted

[Whizbang]

and they were all open diff too. I could have sworn i came across information about the convertible diffs for S5 models being 4.10s tho

[Rotary Evolution]

i'm not sure about the verts but the best bang for the buck to reduce wheel hop in the coupes is a pinion snubber, which costs about $7 and takes about 45 minutes to install, most of that spent removing the bins to get a drill into the center tunnel area above the nose of the differential.

this also helps keep your $180 differential mount from ripping under the stress of wheel hop.

[rotarydream]

The 91 convertibles came with a 4.10. Info direct from the 1991 sales brochure.

[project86]

....

[NoDOHC]

I found that reducing the negative camber on the rear wheels reduces tire spinning on launch dramatically and seems to improve wheel hop. Launch acceleration measurements:

Stock suspension height: 0.93 gs max
Lowered 0.9" (Eibach springs, -1.8deg and -2.7deg): 0.87 gs max
Lowered 0.9" Camber corrected to -0.9deg and -1.6 deg: 0.93 gs max

This is using the stock size tires on a similar day (obviously not the same day).

I can still get axle hop, but it is only if a drop the clutch abruptly with the engine at 2000-4000 rpm and the throttle partially closed. Without camber correction, the axle hop was a problem on a hard launch, now it just squats and goes.