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Old 11-14-2012, 01:37 PM   #151
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Marv, that's funny, I ended up doing essentially the same thing when I upgraded to the GPM parts. I noticed a lot of slop between the C-Hub, the bearing carrier, and the A-Arm so I used a few .5mm and 1mm shims I happened to have to clean up the slop. Worked great.
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Old 11-24-2012, 07:59 AM   #152
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Hello all on the Sprint 2 forum! I'm getting a hpi sprint 2 rtr-x 1969 mustang. I really love the look of the late sixtys mustangs, with that being said i'm already looking at hop-ups for this car ie: carbon chassis, carbon shock towers and i'm interested in the carbon upper chassis plate. Now this is where my questions come in. HPI states the upper carbon chassis plate requires use of a saddle pack, so does a saddle pack do anything for performance of this car? If not then is the upper carbon chassis worth buying? I read somewhere that the lower carbon chassis removes about 1/4 lb of weight, is this true? I guess I just want to know other than the upgrades that Marv has provided; is any of the other hpi upgrades worth purchasing. Let me know. I'll be watching this thread. Thanks!
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Old 11-24-2012, 09:09 AM   #153
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The top and bottom carbon plates will work fine with a stick pack provided you do a little modding. I'll detail what I had to do later if I can remember, it's not hard and really all you need are some straps or tape to hold the battery in. You can also add an extra post to make it work. I believe there are some aftermarket carbon chassis for the Sprint 2 that still allow use of stick packs without modification. But stick packs definitely still work fine.

That said, they do look and feel great. I also have the carbon front and rear shock towers and they look great as well.
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Old 11-24-2012, 09:59 AM   #154
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Thanks Vostok7! A list of carbon chassis other than hpi would be great! Can anybody confirm weight difference of stock lower chassis and carbon chassis? Btw.....I not really wanting to drift this car however it is getting a CC sidewinder sv2 and 5700kv motor. Any additional info on parts and mods would be helpful. Im looking to order some stuff so whats the very 1st. things to upgrade when getting car? thanks! :-)
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Old 11-25-2012, 04:24 PM   #155
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Well after some searching I have decided to cancel my order for the hpi 1969 mustang sprint 2. I really like the car but realistically where I live, onroad isnt a class that my local track races and not many people bash onroad or drift. Plus my LHS stocks HPI parts but not alot. Anyways thanks to all who helped to answer my question.
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Old 11-30-2012, 06:37 PM   #156
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Hi guys, long time reader, first time poster.

I have a HPI Sprint 2 that i'm converting to brushless. I used to actually race the original car this chassis was based off of, the HPI RS4 Pro 2. I am extremely familiar with it!

I found this page after a few searches for "HPI Sprint steering slop" and i have been moding my car with a lot of the great tips from here.
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Old 11-30-2012, 06:39 PM   #157
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I put all sorts of shims and ball bearings all over the car to tighten it all up.

Thank you for all the tips, and sizes, i have replaced all of my ball cups with RPM 4-40 heavy duty cups.

Took apart my diffs, and replaced the bushings with 5x8x2.5 sized bearings, and on each side i put 4 (!) 5mm 0.2mm thick shims to remove the slop from the drive cup, and from Marv's tip, there's a spring pushing on the dogbone.


Last edited by Cadman1981; 12-17-2012 at 12:12 PM.
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Old 11-30-2012, 06:43 PM   #158
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For the front C hubs, i put 4mm 0.2mm thick shims on the turning pins so it stops the wheel hop that the car had. The front wheels after 2 runs are still very tight, and the car is actually quieter and is more responsive and less twitchy.

I can't post pictures yet, but when i can, i'll share everything i've done. I ordered more RPM cups to tighten the suspension, and my main chassis is too weak and tweaked.

Future mods:
EXOTEK Carbon fiber chassis, should get it next week.
and
Pro 4 suspension parts.
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Old 11-30-2012, 06:46 PM   #159
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Default Pro 4 suspension swap

Pro 4 Suspension Swap from
http://www.drccentral.com/old/hpi-sprint-rc-drift.html

What this will accomplish-
1) Higher graphite content makes the hubs stronger than stock
2) Allows for conventional turnbuckles to be used for camber adjustments
3) Bearings sit much more snuggly into the hubs, eliminating wheel slop due to the bearing sleeve being too loose or stretched
4) The car will be slightly lower with stock sprint dampeners after this swap
5) The Pro 4 hubs will actually increase the efficiency of the Sprint's belt drive (Spacers that come with the kit allow you to tourqe the wheel nut down without lateraly pinching or straining the inner races of the 5x10mm ball bearings)
6) Your turning radius will be greatly decreased due to the fact that the new steering setup will give maximum sweep compared to stock (refer to the picture at the bottom of the previous page on this thread)
7) Through the use of spacers that secure the hubs firmly and prevent movement along the length of the suspension pins that retain the hubs, you will be able to adjust the length your wheelbase by 5mm

What you will need-
1) Pro 4 Blocks (2 sets) (part #73507)
2) Pro 4 C-Hubs (1 set) (part #73518)
3) HPI Aluminum Washer 3x6x.75mm (1 set) (part #Z814)
4) HPI Aluminum Washer 3x6x2mm (1 set) (part #Z817)
5) HPI Steering Block Bushings (1set) (part # 75122)
6) HPI Sprint Suspension Pin Set (1 set) (part #85021)
7) Dremel tool with cutting wheel
Drill with 1/8 size bit, preferably something that will not mangle plastic but instead leave a clean hole (I used Bosch 1/8 titanium self tapping bit for this)

Last edited by Cadman1981; 12-02-2012 at 08:19 PM.
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Old 11-30-2012, 06:47 PM   #160
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I got these tips from drccentral.com

Step 1- Begin by disassembling your suspension and stripping everything off of your suspension arms. Even though you will be replacing your blocks and hubs it is advisable to hang onto all old parts anyways. Your phillips head suspension shafts that secure the blocks and hubs to the arms wil also be useless, b/c of the threaded section near the head. Measure the length of the stock phillips head pin, and make marks on your new plain shafts (refer to picture below), and cut the plain shafts to the length of the phillips pin with a dremel tool fitted with a cutting wheel (Wear goggles and be careful with your fingers!).





Step 2- Now we prep the new Pro 4 hubs. The suspension pins used in the Pro 4 to secure the hubs and blocks are smaller than the 3mm thick pins the Sprint uses, so it is necessary to bore out the hubs (refer to the pic below). The 1/8 size drill bit is slightly larger than 3mm, so there will be a small amount of play in the suspension shaft when installed into the hub- this will be corrected with setscrews (don't worry, the setscrew holes are already pre-drilled into the hubs and blocks, so no need to drill this too). Bore both the rear hubs and both of the front C-hubs as well.



*Note* You will notice in the picture that there are 2 spacers pictured, when you assemble your hubs with the bearings these spacers will be sandwiched inbetween the bearings inside the hubs- without anything filling the empty space between the bearings inside the hub, pressure is placed on the inner races of the bearings when the wheel nut is torqued down tight. What essentially happens is the inner races pinch the chrome balls against the inner edges of the outer races... you might have to read that a couple of times... and will result in added friction when the setup is assembled. In a stock Sprint, this is not an issue because the wheel axel is allowed to float, but what this amounts to is a large amount of lateral play within the wheels which will translate into twitchy handling and the car not wanting to track straight. The Pro 4 hubs will allow the wheels to be held much tighter and thus have less play, but at the same time not cause this pinching that will cause bearing failure, high efficiency.)

Step 3- The Pro 4 hubs are slightly narrower than than the Sprint's stock hubs are, so once you do the initial mock up of the assembly the hub will have a good amount of lateral (from side to side) movement on the newly fabricated suspension shafts. To correct this on the front, you only need to use two 3x6x.75mm aluminum spacers on either side of the C-hub. The rear will require one 3x6x2mm spacer on one side of the hub (refer to picture below), and a 3x6x.75 on the other (refer to picture below). The spacers will provide a snug fit and may require a little sanding of the hub at the contact point of one of the spacers to assure a perfect fit (as it did in my case). Its important not to oversand, a snug fit will eventually loosen with regualr use of the car, and will eventually be the perfect tolerance). Also notice the set screws in the middle of the lower part of the hubs. The hub on the left in the picture below had to have the pre-drilled setscrew hole sanded down, due to the fact that there is a 'ring' that protrudes out and will contact the outside of the A-arm (the area that needs to be sanded is in the red circle in the picture below)




Step 4- Now that the suspension shafts have been cut to size and the hubs have been bored out and fitted to accept the spacers, mock up the hubs onto the arms with the suspension pins set in place and the spacers on. There are setscrew holes pre-drilled into the hubs that will secure the suspension pins, but to make sure the setscrews do they're jobs and firmly retain the pins during cornering, we will need to prep the surface that the setscrews will conact on the suspension shaft. With everything lined up the way it should be, stick a needle through the setscrew hole in the hub and scratch the suspension shaft so you will be able to tell where you will need to sand. After this has been done on each shaft, remove the shafts and either sand or notch them where you see the needle scratches. This assures that everything will line up for final assembly with the setscrews.

Step 5- Now that everything is completed (spacer in place beween the bearings inside the hubs, hubs bored out and sanded to appropriate width to accept spacers, and the suspension pins cut to the appropriate length and notched for the setscrews) you can assembled the arms. The last and final step is to insert the wheel axel, connect the dogbones, and screw ball studs into the new hubs for the turnbuckles. Congrats! Now you have a cleaner looking, completely adjustable and lighter suspension setup that will also improve your steering due to the fact that your hubs will now allow your bellcrank to turn the wheels to their limit!
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Old 12-02-2012, 08:23 AM   #161
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Hey Cadman good to hear that your S2 is coming along and thanks for posting the drccentral info =
Very good voodoo indeed!
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Old 12-02-2012, 08:25 AM   #162
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Just out of curiosity - Here's a few questions for you S2 drivers:
How many of you LOCK/SPOOL one or both of your diffs?
What method(s) do you use?
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Old 12-02-2012, 12:11 PM   #163
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I've read at a few places people can lock their spool with crazy glue. For a less extreme thing, just put a piece of metal or plastic so the gears dont turn.
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Old 12-02-2012, 12:16 PM   #164
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Spec R makes a diff locking block, but I don't know if it would work in the Sprint's diffs. You'd have to measure and see if another brand's spool would fit, there are several out there (Spec R, AE, X-ray, etc)
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Old 12-04-2012, 09:28 AM   #165
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Default Diff Locks

Quote:
Originally Posted by Vostok 7 View Post
Spec R makes a diff locking block, but I don't know if it would work in the Sprint's diffs.
You'd have to measure and see if another brand's spool would fit, there are several out there (Spec R, AE, X-ray, etc)
Thanks for the tip Cadman & Vostok for the link.

I checked the site and it doesn't appear that what they have would work.


However, I found these =

Wheelie King Diff Locks
HPI Sprint 2 Mods - Making a silk purse from a sow's ear.-me-010-2t.jpg



These diff locks will fit in the S2 diff case.

With a slot across the length of the locks, the E clips that hold the large OEM
spider gears can be easily installed to hold the locks in place.

With a little work =

HPI Sprint 2 Mods - Making a silk purse from a sow's ear.-dscn4540.jpgHPI Sprint 2 Mods - Making a silk purse from a sow's ear.-dscn4541.jpg

I don't know if I'll even use the locked/spooled diff, but its a "nice to have" just in case.

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