Axle Hop

[skylinecouple]

Just wandering if anyone has experienced severe axle tramp where it feels like the rear end is going to rip out alltogether.Have harder springs and camber bushes and pineapples but no matter what I do I still have it.It seems to be worse in the rain but I think that would be because the wheels start to spin earlier.I only have two ways to launch, control the revs with my right foot, or smoke the tyres hard enough to keep it smooth.The latter may look impressive but not exactly the quickest way to get going.

I have:8" rims with Hankook k104 tyres.

Drift R rims(shouldn`t be too heavy).

King standard low springs.

Whiteline upper camber bushes

Excel-g gas twintube shocks.

Pineapples in neutral position.

The very second I accelerate or drop the clutch it feels like the wheels are only making contact with the road every 100mm.In fact if I find a nice fresh patch of road you can clearly see the rubber only makes contact every 100-150mm.Car has never been in an accident and does not appear to have any worn bushes, just 220rwkw I can`t use to my advantage below 4500rpm.It is at the stage where I am trying to design a traction bar or tramp rod system but no matter which way I look at it the suspension will be limited in it`s movement.

Any ideas?

[Trust33]

Take out the pineapples....I think they are part of ur problem...Before i put those in the car would spin without it all the time...

But still its only on the occasion that it does tramp.really if the brake is applied and i start a burnout in first gear it does it. but for plain drift it is good with them

[skylinecouple]

That is why I put them in,to try and stop it.It feels as though there is no difference one way or the other.I`ve seen hot rods,street machines,skylines and all sorts of cars that don`t do it.WHY MINE !! Now I know I`m not the only one so has anybody done something where the hop just stopped? Super stiff shocks ?, rock hard coils?, slushy suspension?,replace springs with solid steal rods?I don`t care just give me ideas.

[Thunderbolt]

I used to have severe problems in my 180sx, even after the alloy pinapples. I also had brand new coilovers too, so that wasn't the problem. At that stage I was running Bridgestone Potenza GIIIs in 215/ 60/15 on stock 6" rims. The grip was awesome, but it would tramp pretty bad. Since replacing the wheels with R32 wheels and tyres Dunlop 205/55/16, the tramp is a lot improved now.

[gtst1976]

skyline couple i have the same problem. Thought it was my shock absorbers replaced them and it still does it. I do have the same tyres as you (Hankook 104), so that could be the prob.

Edited August 7, 2006 by gtst1976

[skylinecouple]

Ok, seems like I will have to put the stock rims on and some really crap rubber then skate around like on ice.I know,I`ll only take off in second and just smoke em up EVERY SINGLE TIME I LAUNCH !!!

Sorry,I`m alright now,just having a sarcastic moment.Just a little observation; when somebody mentions TURBO, we get a minimum of 20 answers.Type up injector,exhaust,BOV, or pod filter and we get the same result.We are so focused on power that we forget to work out a way to put it to the ground.

Now somebody mention braking, we would be lucky to see three answers.We kid ourselves we have cars faster than a Porche or M3 BMW but having driven both I can`t recall the owners complaining of axle tramp.Having dropped the clutch of a wide body sc carrera many times, na,no tramp.Thankyou to the two people who tried to help but we are obviously the only ones with this problem.

[Sydneykid]

10% of the time it’s tyre pressures, the sidewall flexes and releases. Try pumping the tyres up and see if the axle tramp stops and/or gets less.

5% of the time it’s worn subframe bushes, since you have fitted a rear subframe alignment kit (pineapples) I suspect that isn’t the problem in your case.

25% of the time its drive shaft angle, the car is TOO LOW and the angle of the universal joints are winding up the drive shafts. If your car is lower than 345 mm centre of wheel to guard on the rear, then try raising it up.

60% of the time it’s incorrectly matched spring and shock damper rates. The rebound (extension) damping is not sufficient to control the oscillations of the springs. Standard springs with worn shocks get this problem. BRAND NEW aftermarket coil overs get this problem where the spring rate is too high for the shocks to control.

Once you have eliminated 1, 2 and 3, then your problem is #4

cheers

Edited August 7, 2006 by Sydneykid

[R33S2]

What I read from SK's experienced knowledge is,

On the intial shock of the tyres biting in, the rear end ducks down, so springs and shocks compress and then release slightly, its when they release that the tramping starts, if the shock doesnt release as fast as the spring? it sets up a series of jolts that rebound off one then the other?

I'm learning here and just thinking out loud so to speak.

[Sydneykid]

What I read from SK's experienced knowledge is,

1. On the intial shock of the tyres biting in, the rear end ducks down

2. so springs and shocks compress

3. and then release slightly, its when they release that the tramping starts, if the shock doesnt release as fast as the spring?

4. it sets up a series of jolts that rebound off one then the other?

I'm learning here and just thinking out loud so to speak.

Almost;

1. Yep, you got it

2. Yep, that's it

3. Nope, not quite, what happens is the spring rebounds from the compression in #2. But the shock isn't "strong" enough to release that energy smoothly, the spring recoils too quickly. This rapid release takes the weight off the rear of the car, it springs upwards. So the tyre spins a little bit. When the energy of the spring is fully released (only takes about 1/100th to 10/100ths of a second) then the "upwards" stops. The tyre has weight on it, so it grips again, then the spring compresses, then the shock can't control it agians etc etc .

4. Yep, that's it, as per #3.

If you want to test #3, get a small spring and compress it with your finger onto a table. Then release it by slipping your finger off to the side, very quickly. The spring will jump off the table.

Then compress the spring the same, but this time leave your finger on it and let the spring decompress slowly. The spring doesn't jump up off the table. In the second example, you finger is a good shock absorber, it releases the stored energy progressively, hence the spring (and the tyre in a car) doesn't jump off the ground.

Cheers

Edited August 8, 2006 by Sydneykid

[skylinecouple]

I kind of thought along those lines myself.I am very reluctant to put the Bilstiens back in til they are rebuilt with softer valving on the initial movement.Gary, perhaps you could give me an idea what it would cost to rebuild and revalve 4 shocks.Also,I find if I run tyre pressures in the rear at 38lb the centre tread wears out before the side tread.What do people run in the rears for street driving,I always use 35lbs but will try a higher pressure if needed.On the front I use 38lbs and get perfect tyre wear across the tread.

Edited August 7, 2006 by skylinecouple

[OutoftheblueR32]

I used to have severe problems in my 180sx, even after the alloy pinapples. I also had brand new coilovers too, so that wasn't the problem. At that stage I was running Bridgestone Potenza GIIIs in 215/ 60/15 on stock 6" rims. The grip was awesome, but it would tramp pretty bad. Since replacing the wheels with R32 wheels and tyres Dunlop 205/55/16, the tramp is a lot improved now.

i'm running the same tires on my 180sx, getting heaps of tramp as well. happens when i chuck the clutch from a standstill. doesn't happen during a power slide. Suspension is stock as rock. so i was wondering whether it could be as SK said about the suspension.

[Sydneykid]

I kind of thought along those lines myself.I am very reluctant to put the Bilstiens back in til they are rebuilt with softer valving on the initial movement.Gary, perhaps you could give me an idea what it would cost to rebuild and revalve 4 shocks.Also,I find if I run tyre pressures in the rear at 38lb the centre tread wears out before the side tread.What do people run in the rears for street driving,I always use 35lbs but will try a higher pressure if needed.On the front I use 38lbs and get perfect tyre wear across the tread.

I never run tyre pressures over 30 psi cold.

PM me for prices on Bilstein revalving, I need to get a feel for how much you want to change it.

A Skyline typically weighs 60% front and 40% rear, hence why you CAN run higher front tyre pressure than rear and not suffer excessive over inflation wear. Or, it could be simply that the excessive caster wear is offset by the excessive tyre pressure. There is no caster on the rear to offset the excessive tyre pressure at that end.

Excessive caster wear can be caused by excessive caster (obviously) or by a driver who doesn't use the caster (ie; drives on freeways a lot and/or doesn't corner as fast as a sports car is set up for).

Are you saying at 38 psi the axle tramp stops?

But when you go down to 35 psi it reappears?

cheers

Edited August 8, 2006 by Sydneykid

[skylinecouple]

Will try running much lower psi on the rear.Maybe 30psi and see what happens.

[Pal]

ive had the same trouble for about a year and a half now (since upping the power on the car). i put adjustable dampening shockies in to try control the axle tramp, mainly at the drags where you get better grip and more tramp, is it better to set them softer or harder??

[skylinecouple]

Setting the shocks harder will limit tramp but will not allow squat to transfer weight of car onto back wheels for better grip.I tried running 34lbs this morning in the rear at 7.00am.( Tyres were very cold).After inflation went for a small drive to warm them up and then launched at 3,500rpm.Still hopped but not as bad.Tried launch at 4,500rpm,just dumped the ceramic clutch and a lot of wheelspin but smooth as silk.Needed to feather throttle but only a little.Did the same again but left it on the limiter and into second found alot more wheelspin.As slow as that sounds it actually felt quicker.I think by keeping my foot into it the boost built much faster.When I get to WSID I`ll try 5,000rpm and see how I go.

[R33S2]

Was that just a tyre pressure change and nothing else?

Was it a huge improvement in the axle hop?

[skylinecouple]

Just air.I realize now that the sticky tyres were causing the problem.Being mechanically sympathetic I didn`t want to over rev it so was causing the tyre to bite too much.With the harder launch the extra wheelspin gets me past the point of axle hop.I guess with every new change I have to adjust my driving style.By the way,when someone says adjust your pressures cold,they mean cold.I thought I had put 34lbs in the rears but when I checked in the driveway after a cold night the actual pressure was30lbs. 34lbs now though.Big difference.

[Taso84]

Almost;

1. Yep, you got it

2. Yep, that's it

3. Nope, not quite, what happens is the spring rebounds from the compression in #2. But the shock isn't "strong" enough to release that energy smoothly, the spring recoils too quickly. This rapid release takes the weight off the rear of the car, it springs upwards. So the tyre spins a little bit. When the energy of the spring is fully released (only takes about 1/100th to 10/100ths of a second) then the "upwards" stops. The tyre has weight on it, so it grips again, then the spring compresses, then the shock can't control it agians etc etc .

4. Yep, that's it, as per #3.

If you want to test #3, get a small spring and compress it with your finger onto a table. Then release it by slipping your finger off to the side, very quickly. The spring will jump off the table.

Then compress the spring the same, but this time leave your finger on it and let the spring decompress slowly. The spring doesn't jump up off the table. In the second example, you finger is a good shock absorber, it releases the stored energy progressively, hence the spring (and the tyre in a car) doesn't jump off the ground.

Cheers

So, if uve eliminated all the options and it must be this causing the axel tramp, what is a good way to fix it. Should i set the shocks to the hardest damper setting possible so that the shock resists the spring more?

[MerlinTheHapyPig]

if 4 is the problem, then shocks aren't working, you can try increasing the damper (particularly if your shocks have rebound damper adjustment), but it's common for blown shocks to cause axle tramp, you may need to replace or rebuild the shock absorber. the spring rate could also be too high, so you should also look into that.

it's possible to run ultra-high springrates without problems provided your shocks are up to the task!

[Taso84]

if 4 is the problem, then shocks aren't working, you can try increasing the damper (particularly if your shocks have rebound damper adjustment), but it's common for blown shocks to cause axle tramp, you may need to replace or rebuild the shock absorber. the spring rate could also be too high, so you should also look into that.

it's possible to run ultra-high springrates without problems provided your shocks are up to the task!

Well basically ive just installed pineapples and it hasnt fixed the tramp, So its either the tyres or the springs/shocks

I dont thing my shocks have rebound adjustement but they do have damper adjustement. To minimise axel tramp u think i should try increasing the damper, ie setting it to really hard?

Assuming the shocks are fine which i think they are, what springs do u reccomend?

I think tyres may also be contributing. I've got some really cheap brand called ANT tyre, that doesnt grip properly and is made of really hard compound. (Ie they hardly ever smoke, Ive had them a year and the tread is still 95%)