eunique

iTrader: (3)

Make sure your belts are not on too tight...it doesnt need to be...so maybe loosen some slack on the tensioner. Make sure also that the bearing holders are alugned properly.

eunique

iTrader: (3)

Just to make sure...you need this for the KPI mod, correct?
Here is plastic part number SD-008UC
http://banzaihobby.com/index.php?mai...ducts_id=13670

eunique

iTrader: (3)

I do have full options on my D3 and love it.

For the belts...the stock ones are fine and very durable. 1st one i had to replace was front..but i think it had other stress factors into it since i initially ran it solid axle until i got the FOW and also a lot of chatter until i upgraded steering and CVDs. And then center belt just recentlywent back to smaller 13T pulley (used 14 before to lower CS ratio which left more slack) and i hadnt been using the belt tensioner (carbon chassis has better stock tension over stock chassis for some reason)...so i guess it was skipping teeth due to loose belt and ended up shredding a bunch of teeth.

I believe i am still on the stock rear belt and i have had this chassis since it came out for public release August 2012.

I do keep spare belts now just in case so i have less downtime...but not really worried and replacement belts have been good.
On that note...as the center belt loosens over time, i will be putting back my belt tensioner...and maybe buy the new rear bulkhead with built in tensioner.

FoiVoS_

Ace i am in the same stage with you with the build and i noticed that stiff turn also ! I thought that it was the bearings but as it turns out if you lower just a litle the rear belt tension the stiffness will go away ! I am trying to find a balance between the tension and the resistance of the belt system.
As it is my first chassis and build i was quite amazed by the resistance that it provided but as it turns out we are ok
Also what bearings did you buy and from where ?

FoiVoS_

What exactly do you mean by saying to check if the bearing holders are aligned ? In what way ?

eunique

iTrader: (3)

For example...if your front bearing holder on the left is at position 2 from the bottom..make sure the right side is also at position 2 from the bottom.

Caseymacgyver

Thanks! I hadn't started out with all of it in mind though (said the junkie). But, I've enjoyed the process and I'm still enjoying the hell out of this chassis. I'm sure you will too no matter what you end up doing to it.

Getting the rear belt tension right on this car can be a bit tricky. The rear post tensioner is difficult to access and you have to basically guess the height of the idler bearing before using the eccentric axle bearing holders to get it just right. The tension on the main belt can also pull the rear belt too tight, especially with the stock chassis, so I always set the main first.

A couple of tips for setting the rear belt tension:

• Ensure your rear axle bearing holders are installed correctly ('A' on the left, 'B' on the right), with the groove seated all the way around the bulkhead.
• Loosen the rear bulkhead covers just enough to rotate the rear bearing holders to their lowest tension position (Arrows pointing down).
• Set your main belt tension by the method of your choosing first, with zero tension on the rear belt.
• Set the idler bearing height on the rear tension post to just barely allow the rear belt to be rotated on/off the 22T pulley (Like putting on a bicycle chain). You can loosen the tension post mount from the underside of the chassis a couple of turns to allow rotation of the post and better access to the idler adjustment screw, without having to remove the post. Despite the alignment pin on the post, make sure the idler bearing is in plane with the belt when you tighten it back down.
• Rotate the bearing holders up 2-3 holes, making sure both sides are the same.
• The rear belt does not need to be taut to prevent skipping; it's not a fan belt. Just enough to keep the belt from hopping off the idler bearing. About 1/8" of free play (Not elastic deflection) seems tolerable for the rear belt.
• Rotate the bearing holders more/less as needed, then tighten the bulkhead covers. Double-check the rear belt tension before re-installing the little screws to lock the bearing holders.
• If you ever hear a pop or a sudden surge, or a dull grinding sound, that means a belt skipped. If you stop immediately and find/fix the applicable tension, you may be able to save the belt and/or pullies. Driving until the belt finally shreds out, or over tensioning a badly skipping belt, will very likely round off all of your plastic pulley teeth, thus accelerating the same failure in your next belt.

The front belt tension is a bit easier to set, since it's all locked in the front bulkhead. However, the close spacing and relatively large pulley size differential (13T to 38T) means that fewer teeth are able to be in contact with the belt on the 13T pulley. This puts more importance on the belt's tension, which needs to be tighter than the rear, even at the cost of a potential increase in parasitic loss in the drivetrain. The front belt needs to have nearly zero free play, with as little elastic tension as possible.

It can be misleading to gauge belt tension by the rolling resistance. With the CS and final drive ratios on this car, especially in the rear, turning the rear wheels by hand, with all belts and the motor installed can make it all seem quite stiff indeed. I'll usually test mine by pinching the top stretch of the main belt towards the front with 2 fingers and pulling it toward the rear as fast as I can and letting go. At that point, everything should freewheel for just a moment. If I feel any inconsistencies during the pull, hear and ticks or creeks, or it stops dead when I let go, that tells me that something is not right.

slyts6

iTrader: (37)

Yeah it's for the kpi mod! The plastic version looks very different to the aluminium version... Do I need to drill holes for the lower shock mount?

Ok im lost... are these uppers to replace my upper turn buckles? If so... What plastic part do I need to do the lowers?

eunique

iTrader: (3)

Yes the Yok Type C are to replace the upper turnbuckles.
The lower arms...you cut the off, drill a hole and thread 3mm to use a long set screw and use a ball end to complete the lower arm

Caseymacgyver

Yeah, the KPI topic has gotten a bit muddled, which I'm sure that I contributed to. I'll try and consolidate some of the info here in hope of clarifying:

The KPI mod is a complete and fundamental change of the D3's front suspension. It swaps out the steering knuckles and CVD's, deletes the C-hubs, replaces the upper double-ball links with vertically constrained arms (Yokomo Type C) and modifies the lower arms (Chopping and drilling) to attached ball cups for the lower link. In essence, all of that is to convert the upper and lower steering knuckle pivots to simple ball joints, with fore/aft stability coming from the upper and lower arms themselves, rather than the C-hubs.

The real key to being able to do KPI is using steering knuckles that have the ability to offset the steering axis from the wheel axis normal. MST is one of the few companies that currently offer that. So to be clear, the "KPI" part of the mod comes from the knuckles, and only the knuckles. The other steps are just prerequisites, with other worthwhile benefits.

The most common method uses:

1. Yokomo Type-C 'Parts' Upper Suspension Arms - part number SD-008UC Banzai Hobby
   
2. MST I PARTS-wheel hubs 210008 (Plastic) OR MST Short Arm Steering Hub, 210239 (Aluminum) - Ebay
3. MST CVA wheel axle (2 PCS) 310006 - Ebay
4. SQUARE Universal Shaft 46mm:OTA R31 from Broadtech.hk, Banzai, RCMart, etc...
5. (2) 20mm set screws
6. (2) 10X15X4mm bearing (same as the large diff. bearings)

The Yokomo arm really just replaces the inner ball stud and ball cup of the upper link. The turnbuckle threads into it, with the outer ball cup still attached. You cut/file a nice tight slot through the pivot of the Yokomo arm so that it forks around the front shock tower. You then use screws or a hinge pin through the holes in the Yokomo arm and your preferred roll center hole (existing) in the shock tower. The arm should be tight fore/aft, but free to pivot up/down.

The lower arms get cut off square at the crossbar, about 1/3 of the way inboard. You then drill a 0.100" hole roughly in the middle. The location depends heavily on where you cut the slot in the Yokomo arm. Fore/aft on either changes the caster. Do the Yokomo arms first, both at the same time if possible, and install. Then decide where you want to drill the lowers, and do them both at the same time as well. With the hole drilled, you then thread in the 20mm set screw, screwing a ball cup to that. Again, do both at the same time, holding them side-by-side. Make sure the cups extend the same distance and point in the same direction. Once you put them back on the car, count how many turns you make when finalizing the trackwidth then match on the other side.

Cutting the lower arms as described above will eliminate the outermost shock mounting position, and most likely make the 2nd outermost unusable (Chops right at the edge). This is not generally a problem, as with the significantly increased steering angle enabled by the other aspects of this mod, those 2 mounting positions become unusable anyway because the wheels would hit the shocks. The 3rd (innermost) mounting hole is unaffected by the mod and presents no interference issues. However, the increased leverage to the spring will require something correspondingly stiffer (Blue or Purple).

Caseymacgyver

Yep, what he said

DMSewell27

iTrader: (4)

I recently replaced my rear 13 and 22 tooth pulleys to a 14 and 18 tooth, respectively, to get a milder CS ratio of 1.63.

As with everyone I experienced a lot of slop on the both the long drive belt and rear belt. Instead of using spacers and what not I decided to find the proper sized belts to remedy the situation. I found some new old stock belts at my LHS and they let me test fit things until I got it right. For the long drive belt you are looking for a 3x516mm and for the short rear you are looking for 3x177mm.

The Tamiya part numbers I found were 54143 (middle) and 53707 (rear). If you can't find those, it looks like the new Sakura XI will be using those same belts out of the box. I can not confirm that from experience, but from what I see online they should work.

I hope this helps, and keep the great posts coming guys. This is one of the most informative vehicle specific threads I have seen.

DMSewell27

iTrader: (4)

Thanks for putting the KPI mod in black and white.

But, I would like to know a little more about the horizontal shock you have mounted behind your front shock tower. from what I can see it offers some more adjustment to the KPI, but in truth... I am befuddled.

slyts6

iTrader: (37)

+1

slyts6

iTrader: (37)

I agree the help on this thread is fantastic!

I'm currently using a 516 off an XI and I personally feel its too tight. I'll be switching back to a new stock with tensioner and I will possibly change my pulleys to make the CS a little less and take out a bit of slop.