Rear tire Hopping at high mph

[Goatkart]

So, after putting the aftermarket swing arm on, which is a stock swing arm extended 4 inches...

I also installed the progressive suspension 465 shock....


Now at high mph, around 110-120 + mph i get what feels like an unbalanced tire...

I think its generally when under throttle... though its hard to tell, with the turbo i have to get out of it pretty fast or ill be running cars down...

Anyhow...

I just checked the rear tire, and it balanced out perfectly (using dynabeads in the tire as well)..


My first idea was that i might be getting pogo from the progressive spring, so i added a couple turns to the spring to increase preload...


Now, it seems like my tire hop got FASTER at high mph?



SO i think i have a suspension setup issue, so i'm looking for the pro's to maybe point me in the right direction....

 

[sixpack577]

Are you sure it's just not trying to break traction?

 

[Goatkart]

Are you sure it's just not trying to break traction?

The thought had also crossed my mind.... So, short answer I-dun-o






To increase traction at the rear tire under load, would i want to stiffen up the spring, or soften it to allow more transfer....


suspension is something of a voodoo to me..

 

[Goatkart]

internet research suggests i should reduce dampening.... i have it at 3 the default middle of the road setting...

not sure if this is accurate or not LOL

 

[sixpack577]

The thought had also crossed my mind.... So, short answer I-dun-o






To increase traction at the rear tire under load, would i want to stiffen up the spring, or soften it to allow more transfer....


suspension is something of a voodoo to me..

It burns my brain trying to explain the little I know about suspension, but I seem to have good results when I'm hands on with it.
Since you stiffened the spring, if you were breaking traction, it would make sense that the problem got worse.
I'de purposely go too soft, ride it, and slowly stiffen it back up from there. With it overly soft it would make it easier to notice if you were breaking loose though.

 

[Goatkart]

Right on... I'll grab the spanner and try and soften it up tomorow then...

With this progressive spring, its got me nervous that i'll end up with a bad pogo effect instead....

 

[afterhours]

what tire are you using and what is your PSI?

 

[Goatkart]

what tire are you using and what is your PSI?

Mich Power Pure 2ct 190/55

psi honestly, this sounds dumb, but i havent checked it since i finished the build.... i know i know.... just with all the excitement it never occured to me...


it WAS at 42 psi (or what ever the oem man rec is) i didnt know people ran them a bit lower till the other day... so i always filled it according to the sticker thingys recommendation...

 

[Rainbow7]

Sounds like tramping, to me.

 

[afterhours]

Mich Power Pure 2ct 190/55

psi honestly, this sounds dumb, but i havent checked it since i finished the build.... i know i know.... just with all the excitement it never occured to me...


it WAS at 42 psi (or what ever the oem man rec is) i didnt know people ran them a bit lower till the other day... so i always filled it according to the sticker thingys recommendation...

at that PSI, the tire is really hard,unable to absorb any small bumps on the road....also at that PSI the contact patch would be really small, which could add to the problem.

drop the psi, see if it helps.

 

[Goatkart]

at that PSI, the tire is really hard,unable to absorb any small bumps on the road....also at that PSI the contact patch would be really small, which could add to the problem.

drop the psi, see if it helps.

K, will try that as well...


I had heard the power pures didn't respond well to lower psi's due to the lightweight carcass design... not sure how true that is or not however...

 

[sixpack577]

K, will try that as well...


I had heard the power pures didn't respond well to lower psi's due to the lightweight carcass design... not sure how true that is or not however...

I would agree, I got alot more wobble from the rear at lower psi on high speed wheelies with them. That's normal, just alot more noticeable with that particular tire. They stick well in curves still at lower pressure though, as they should.
High tire psi, hard suspension, alot of building boost and power, still seems as if it was trying to break traction and causing a rough ride.

 

[Goatkart]

So checked my air pressures...


i was sitting at 41R/35F (good thing i checked holy leak down in the front)


I set the rear at 40 even, and will be airing up the front to 41... i believe thats how thats supposed to work (air front slightly higher than rear)...


The rebound dampner had shifted off 3 where i had it set, down towards 2 (less dampining) so it seems likely i had some problem from under dampening... so i set it to 4, assuming i still had problems when it was 3...


lastly, i back off the preload a smidgen, since that adjustment seemed to make everything worse...

I know its a lot of changes (dumb move) but i am trying to get things back to a square one again, since things were all shifting from what i thought baselines were...