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Old 20-06-2018, 10:08 PM   #1
Big Al
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Default Minimising wheel hop?

It was in damp and cold condition but recently noticed when launching hard off the line I got wheel spin but also a lot wheel hop. I'm not sure how much of this was down to just the wheels spinning and struggling for traction and I was just being a bit over zealous with the fun pedal off the line, or if should be concidering upgrades.

First port of call was the engine mounts which have upgraded to harder group n mounts from sti...next bug stuff.

The mounts are tied into the frame horns, and they are tied into the roll cage so hope they should be pretty solid.

Gearbox doesnt have a front mount but has a solid top strap and berg style mid mount to stop it dropping, and tied to the scoob mounts through the engine so hopefully ok there. However considering adding an additional mount to replace the missing stock one to stop to any forward movement.

Springs are 944 so stiffer than stock to cope with extra weight and tbh I was supprised and not stiff they are at all with that weight difference. I daren't make these any softer as pretty sure I would slap the floor with the motor....again. read: sump 2. Lol

Dampers are KYB Gas shocks. Old but not had much use. Think modern replacement is KYB GP2 or sonething. I used to think these were pretty harsh but seem pretty good with extra weight at the back. Do you think a stiffer damper woukd help slow the short shock of a hop?

Ive 944 irs using cut down 944 springplates covers. I still have the stock rubber donuts. Would you think urethane are a good upgrade? Not something I've ever fitted and no idea how they will effect the suspension.

I can't think of anything else other than chassis movement I should be considering. Anyone?
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Old 21-06-2018, 10:16 AM   #2
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Got any pictures of how the cage ties into the framehorns? Sounds like your engine cradle uses the standard subie engine mount locations?
Is it a Subie gearbox?

I've never had to set a car up for drag racing so unsure if stiffer or softer springs would help keep the tyres on the floor. I mean the only thing trying to stop the rotational force of the tyre is the spring and damper along with the vehicle weight and weight transfer. Softer springs and damping would allow for more weight transfer and then dual adjusting dampers so the rebound is softer? Just some thoughts.
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Old 21-06-2018, 10:34 AM   #3
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I 'think' wheel hop is caused by the frame horns flexing - so you need to run something like a kafer cup brace or tie them into the cage/body, can't tell from what you've said if that's already been done
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Old 21-06-2018, 11:37 AM   #4
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Even with your frame horns tied into the cage your engine / gearbox will still have movement using rubber mounts - unless you go down solid mount route.

I think you'd be wise to fit a front gearbox mount to help limit movement further.

I found running a Traction bar helps - never had any wheel hop issues with one fitted.

If it helps...my rear set up : frame horns tied in/supported, urethane donuts, yellow rhino gearbox mounts, mid mount, traction bar, standard torsion bar and AVO coil overs.
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Old 21-06-2018, 01:22 PM   #5
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I ran a Berg bar under my engine on my 64, with a 1776. I never had any problems with wheel hop with stock shocks and mounts.
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Old 21-06-2018, 03:40 PM   #6
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Quote:
Originally Posted by psimitar View Post
Got any pictures of how the cage ties into the framehorns? Sounds like your engine cradle uses the standard subie engine mount locations?
Is it a Subie gearbox?

I've never had to set a car up for drag racing so unsure if stiffer or softer springs would help keep the tyres on the floor. I mean the only thing trying to stop the rotational force of the tyre is the spring and damper along with the vehicle weight and weight transfer. Softer springs and damping would allow for more weight transfer and then dual adjusting dampers so the rebound is softer? Just some thoughts.

Quote:
Originally Posted by bean View Post
I 'think' wheel hop is caused by the frame horns flexing - so you need to run something like a kafer cup brace or tie them into the cage/body, can't tell from what you've said if that's already been done
I think the horns should be ok. They are tied directly into the cage like so....



Before anyone mentions the front mount in this pic it's already had additional rubber support added to minimise vertical movement.
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Old 21-06-2018, 03:51 PM   #7
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Quote:
Originally Posted by JMP View Post
Even with your frame horns tied into the cage your engine / gearbox will still have movement using rubber mounts - unless you go down solid mount route.

I think you'd be wise to fit a front gearbox mount to help limit movement further.

I found running a Traction bar helps - never had any wheel hop issues with one fitted.

If it helps...my rear set up : frame horns tied in/supported, urethane donuts, yellow rhino gearbox mounts, mid mount, traction bar, standard torsion bar and AVO coil overs.
Don't really want to go the urethane route atm as just uogradd to significantly stiffer rubber mounts so going to give them a whirl. Really do feel physically harder so should take up some movement.

You know it's funny I have the mid mount but not really concidering a traction bar, which if was a bug engine would have done first. I'll get my fabbing head on and come up with sonething if possible as very little to mount to or rest on.

Some replacement for the front mount will need making. Again tricky as an 091 box in a bug and moved forward 2 inches.
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Old 21-06-2018, 03:52 PM   #8
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Quote:
Originally Posted by keekster64 View Post
I ran a Berg bar under my engine on my 64, with a 1776. I never had any problems with wheel hop with stock shocks and mounts.
That's 2 votes for a traction bar.

Tx for the ideas all
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Old 22-06-2018, 01:44 PM   #9
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hmm - as you say the horns should be ok!
I've reached the limit of my knowledge (guesswork based on experience - wheel hop is NOT fun!!) on what it could be but will watch with interest for any other ideas.

may be an idea to post CAL your LOOK query LOUNGE elsewhere to see if you get more ideas (not to downplay what you've had so far but a bigger net can only help)
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Old 22-06-2018, 11:44 PM   #10
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Any way you can get a good video of a hard launch on slow mo, then you can have a good old look at what is moving and when?!
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