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HPI Cup Racer 1M

Old 10-16-2014, 08:43 PM
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My cup racer is apart for odd grinding noises in the rear. Also it keeps letting the right-rear drive loose at the hub. Has a Lancia body on it, so I assume that takes a toll on its reliability :-D *


*Daily drove a Lancia Scorpion for years. Great car once previous owners 'improvements' were removed.
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Old 10-17-2014, 11:13 AM
  #3302  
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Do you have the upgraded metal hub piece where the drive shaft connects to the diff?
It's been awhile since I've driving my CR (been focussed on other cars). But the stock piece is a 3 pronged plastic piece that has a tendency to break. When it does you'll have loss of power as the drive won't be engaging the diff (front or rear, same design) ...and you will have grinding noise. The metal replacement piece solves this.

Regardless you'll need to remove the top portion of the CR chassis, drive shaft and front and/or rear diff to find out what is going on. If you hvaen't replaced that plastic hub piece that would be my bet.
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Old 10-19-2014, 10:19 PM
  #3303  
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Originally Posted by eR1c
Do you have the upgraded metal hub piece where the drive shaft connects to the diff?
It's been awhile since I've driving my CR (been focussed on other cars). But the stock piece is a 3 pronged plastic piece that has a tendency to break. When it does you'll have loss of power as the drive won't be engaging the diff (front or rear, same design) ...and you will have grinding noise. The metal replacement piece solves this.

Regardless you'll need to remove the top portion of the CR chassis, drive shaft and front and/or rear diff to find out what is going on. If you hvaen't replaced that plastic hub piece that would be my bet.
Thanks for the advice, I bought this one second-hand from a member of this forum. I think both ends of the front-to-rear driveshaft are replaced (as i can clearly see the front hub is metal) and it would be daft to replace one and not the other, right?

It's finally time for that teardown :-)

Shocks also need a rebuild. I've put quite a few miles on this as my basher, so much fun. Too bad Mini racing is dead in my area, fun class.
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Old 10-20-2014, 03:48 PM
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If you haven't torn down and checked your diff's in awhile I'd go ahead and do it. I am a bit insane, but I rebuild the shocks (mostly just taking apart, clean, refill and re-calibrate) after every race day OR every 3 to 4 bash sessions. As for Diff's I usually tear those down at the end of every race season unless there is some reason to do so sooner. For bashing as soon as I sense or hear issues I tear it down.

I don't think the metal hub pieces came in sets, I think they are sold individually and are about $9 each. Since that part is prone to break, they may have just replaced the one broken piece? Hard to tell until you get it apart. ...but yes you can get a glimpse of them when everything is together.

Sorry to hear that the mini class is dead in your area. It is very much alive in my area, we have anywhere from 5-15 contestants each race day in the mini class, ...usually about 8-11 entrants. Although we only race Tamiya Mini's in our class. I did race my CR for 2 seasons, but "open" mini class didn't have enough entrants ...yet looks like there is more interest again so I may bring my CR out of retirement?

okay, let me know what you find after you take it all apart.
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Old 10-20-2014, 03:48 PM
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-----this was a double post----
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Old 11-08-2014, 08:15 AM
  #3306  
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Hey folks, what Lipos are you finding will fit into the OEM chassis, or what solutions have you come up with for it?
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Old 11-08-2014, 02:12 PM
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Okay, I found one in my LiPo collection that will work, although it is a 3s... It fits and I think I'll rock it!

It's a Nano-tech 3300 mAh, 3s. I was planning to run my Traxxas VLX 3500kv system and ESC on it, but the motor is a tight fit, and the ESC is on the larger size.


I test fitted a Tekin Redline Gen2 13.5T that may make this car scream on a 3s

3s 3300mAh LiPo


General Mock up of the parts


13.5 Turn


Too Much?
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Old 11-08-2014, 11:03 PM
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Lol 3S is a lot for this car. I just finished putting my 2s in from another car that is now running 3s. I'm trying to keep it somewhat drive able.
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Old 11-09-2014, 05:10 AM
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Originally Posted by firefoxussr
Lol 3S is a lot for this car. I just finished putting my 2s in from another car that is now running 3s. I'm trying to keep it somewhat drive able.
Yeah, in the back of my mind I'm feeling like its a bad idea, and may just pickup a 2s pack for this.

I was thinking it may make the car too unstable with that much power.
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Old 11-15-2014, 10:56 PM
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Originally Posted by ViperZ
Yeah, in the back of my mind I'm feeling like its a bad idea, and may just pickup a 2s pack for this.

I was thinking it may make the car too unstable with that much power.
I like the cup's sublime handling* so I'm lifting the SpeedPassion 21.5 from my ex-racer. Smooth, sensored and no worries. A little 2S leftover from my Vaterra which fits great with some velcro in the battery compartment (put toward the aft cuz it's short).






*I say sublime cuz it just handles a lot better than my old Sprint 2. Which was secondhand, who knows maybe it was messed up internally and I didn't know it.
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Old 11-16-2014, 06:34 AM
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Originally Posted by firefoxussr
I like the cup's sublime handling* so I'm lifting the SpeedPassion 21.5 from my ex-racer. Smooth, sensored and no worries. A little 2S leftover from my Vaterra which fits great with some velcro in the battery compartment (put toward the aft cuz it's short).

*I say sublime cuz it just handles a lot better than my old Sprint 2. Which was secondhand, who knows maybe it was messed up internally and I didn't know it.
Not a bad plan... This car should be set up for the fun scale aspect of it, not land speed records, we have other rigs for that

I may follow your lead with a 21.5 as well. I just installed a 21.5 in my VTA build. From what I've seen, that's fast enough for this cup racer.
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Old 12-28-2014, 10:43 PM
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I have a 17.5 for this if i can find a used one online. Anyone know if these things drift well?
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Old 12-29-2014, 10:25 AM
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Originally Posted by rudeboy03
I have a 17.5 for this if i can find a used one online. Anyone know if these things drift well?
yes, half of them sold were sold as drift models. the car has a ball diff in the back just to add to the RWD feel.

Originally Posted by ViperZ
Not a bad plan... This car should be set up for the fun scale aspect of it, not land speed records, we have other rigs for that

I may follow your lead with a 21.5 as well. I just installed a 21.5 in my VTA build. From what I've seen, that's fast enough for this cup racer.
I did it and it's slow/temps are really low, I think i have a 24 or 27 tooth pinion, need one that is taller. Any suggestions?
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Old 12-29-2014, 10:54 AM
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-getting my CR'r dusted off for its first racing season in about 5 years. ...our club is opening up an "open mini" class.
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Old 01-04-2015, 07:52 AM
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I have my 21 turn Speed Passion setup from my F103 installed, it's clearly under-geared.

I used the biggest pinion on my 48p collection, which is 24 teeth. Anyone run higher tooth count or smaller spur?
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