hpi sprint 2 sport questions (parts interchange or upgrades)
 

I have searched here and online (with no luck) looking for someone who could tell me some better quality knuckles and c hubs that will not wear out for this car. I was wondering if one of the better manufacturers parts would interchange from other cars. I currently run this car in vta and it fits the bill. I know their are better cars out there but i didn't know if i would like on road that much so i'm starting here. I see on ebay that gpa has full alum upgrade kits with arms, knuckles,C hubs and one piece shafts. I just don't want to add that much weight especially for vta. I was thinking about the one piece shafts and the alum knuckles and maybe some rpm ball ends so they wont pop off. I put a faster motor in this weekend and did some club touring car racing and the camber link ball ends kept popping off and the tie rod ball ends and then finaly the knuckle just plain wore out where the screw goes up through it.That caused the axle to pop out constantly. I had fun though. I was hoping their was some better interchangeable parts from some other car i could upgrade with. I dont plan on racing sedan with it but its fast pace showed me its weak spots that i need to beef up to stay in one piece for vta. Any help would be greatly appreciated. Thanks.

HB Cyclone/TCX or Tamiya 416 hubs & C's can be used. But the stock parts are just fine for VTA.

I good upgrade is the ball diffs, CVDs and adjustable shocks.

Ron, I have been racing this chassis for the last year in VTA with much success. I have changed to the Associated ball studs and link ends off a TC5. It has helped reduce slop and they fit inside the HPI wheels where the RPM pcs do not. The biggest upgade I recommend is the ball diff, set tight, for the front. I also use the CVD axles in front since the dogbones fall out when used with the new diff. I have not lost or broken any parts on this car after a year worth of use. It is suited fine as a VTA racer.

Good deal keep the tips coming. Any other parts worth upgrading or keeping on hand? I just want a good durable vta car.

I see several size ball studs. Wich size are they? What is the ball diff and where do you get it? What brand cvds are you using? Are the diffs fluid filled? If so how often do you service and what weight?

Hpi hosts a bunch of option parts for this chassis http://www.hpiracing.com/kitoptions/708/ . The diff is Hpi#86040 and the CVD is Hpi#86198. The Associated ball ends are assoc#6274 and the studs assoc#31281 or31282 (cut and space as needed). I am also using Assoc#3942 silver springs front and rear on the supplied shocks with the Hpi 68 or 69 Camaro body for asphalt racing.

Good deal. So no fluid in the diffs? What weight you running with those springs on the shocks?

If you run the ball diff in the front just tighten it to mimmick a loose slipper spool. Leave the rear diff alone. Use the lightest oil you can on your track. Too thin it will be bouncy but too thick will make it respond slowly. Start with a fresh fill of 25 or 30 wt.

Do you stick to the 3.5 fdr rule? If so what pinion spur ratio do you run?

so the diffs are not fluid filled? I have yet to take them apart to find out but need to know before i do.

The stock diffs are filled with grease. I tried to fill the front with fluid but it is not able to keep sealed and the fluid leaked everywhere. That is why I went to the ball diff. It can be tightened with a screw. As for the fdr's. I race with a 17.5 that requires a 4.0 fdr as per the motor mfgr and the temps that results. The VTA rules you are trying to follow require a fdr as per the motor they expect you to use which is a 21.5 or a 25.5. Different windings on the stators result in different usable fdr's. The best way to find the best gearing for a motor is its temp. Use the motor your racing class requires at your track. Wrong gearing / motor combos lead to motor failure.

are the ball studs a really needed upgrade? I just want to know if the associated ball ends will fit snug enough on the stock ball ends or should i get the associated studs so it will be a better match? If the associated studs are the better way to go should i get the 8mm ones or the 10mm ones.They are like 10 bucks per 6 so will be about 30 dollars to replace them all is the thing.

I would use a spool up front if you can find one and put the ball diff in the back, not to tight back there. Build it good and smooth.

I would not go with too much aluminum anyway. Remember if you stress it too much plastic will break and aluminum will bend. So aluminum will leave you with a warped misperforming part. The broken plastic gives you a visual indicator of what needs to be replaced. The aluminum will lie and say that nothing is wrong, when in fact it is no longer shaped the way it should be. Hub carriers are fine in aluminum. Small stout parts are usually fine in aluminum, but I would stay away from long lean parts like arms. Stay with stock on them. Or something like RPM if you can find them.

Thats the thing about VTA even if you bust it, the damage is not likely too bad. The wear and tear is not so bad. The fun is still there if not more so. You never have to take your car home in a bag. Not so with touring.