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Schumacher Mi4

Old 03-12-2012, 02:27 PM
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Originally Posted by olhipster1 View Post
To solidify the weight question...the CXL can make weight easily.

car came in at 1393 with body on car, ready to race and a 5600 pack (not in pic but heavier)

could of drooped it easily to 1380....had the optional battery brace on...and body was at least 8 grams overweight ( I sho-goo'ed the inside wheels heavily, 1/4 tube )

Thanks to CRgraphics (CRgraphicsonline.com) for the new paint scheme.
I'm at 1366 ready to run w/ 5000maH battery.
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Old 03-12-2012, 02:41 PM
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Originally Posted by cuttingedge View Post
Schumacher Shock tops are drilled as standard to let the air out when building , Martin is doing something slightly different which I am sure he will explain .
their not talking about the hole in the side of the cap, but rather one on top.


Rich, I've drilled the hole before, it takes less then a minute each and its not big a deal, but to be honest I couldn't really tell a difference in back to back testing with two set of shocks with one set drilled.

when i build the shocks, I take two 2mm clip on spacers for the hinge pins and place them on the shaft, slowly push the shock shaft up while holding the bladder down in the center so the oil can ouzzz out around it and screw the cap down. the shock shaft shouldn't have much rebound up or down.

hope that helps.

btw, Arron showed me the clip trick, if hes around still, maybe he can show you in person
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Old 03-12-2012, 03:19 PM
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Originally Posted by skypilot View Post
their not talking about the hole in the side of the cap, but rather one on top.


Rich, I've drilled the hole before, it takes less then a minute each and its not big a deal, but to be honest I couldn't really tell a difference in back to back testing with two set of shocks with one set drilled.

when i build the shocks, I take two 2mm clip on spacers for the hinge pins and place them on the shaft, slowly push the shock shaft up while holding the bladder down in the center so the oil can ouzzz out around it and screw the cap down. the shock shaft shouldn't have much rebound up or down.

hope that helps.

btw, Arron showed me the clip trick, if hes around still, maybe he can show you in person

Ritchie, you showed me that trick last year...i know it works. I just wondered why it was done and what benifit it gave.

Thanks,

Rich P.S. did you send the letter?
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Old 03-12-2012, 04:00 PM
  #3409  
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You are absolutely right.

On tarmac tracks in general it is very common to drill holes in shock tops not only on our car but on almost everyone.

It will make the car roll a bit more, generate more steering (which is always necessary on tarmac) and just give more corner speed.

I have found that on bumpy tracks (UK!) more rebound is better as there is more contact between tires and surface :-)

The way you drill the hole is explained below.

Why do you drill hole:

we'll to be honest, it's not exactly drill because it makes building the shocks less necessary every other run (as mentioned below) but rather to make the shock work in a different way.
When you have no hole, the bladder seals a air volume between bladder and shock top. This acts like a spring -> that's the rebound you get when building your shocks the regular way, even if you push the shaft all the way in.

Furthermore, even if you build your shocks with the least possible amount of rebound (undrilled still!), the shaft will be sucked back into the shock when it gets pulled out also known as "suck back".

This suck back effect is inevitably and does not harm the cars performance. In fact, it makes the car very reactive around neutral when you run low rebound / a lot of suck back, as the suspension "wants" to compress immediately.

Both effects, the little bit of rebound you always get and the suck back are desirable on carpet but not perfect for handling on tarmac, as on tarmac you aim to have a super smooth and more linear suspension operation.

therefore you drill the shock tops to get rid of both described effects, as with no sealed air volume, the only thing that can cause suck back or rebound is the bladder itself, which generally is quite soft.

Please note at this point: even when you get near no rebound with drilled shock tops even when leaving the shock shaft out all the way during the build, it still makes a difference, where the shock shaft is, when you screw the cap on.

When I run drilled shock tops, I always have the shocks haft stick out of the shock body by 6mm. This is about the neutral position when the car is running -> the bladder is neither being sucked in or pushed out. When you push the shock shaft further in during the build the dampening gets slightly softer , having it stick further out will stiffen up the dampening, even though you use the same shock oil! The difference is not to be left aside!

Well that was a longer entry than expected about drilled shock tops now :-) Sorry for the long read, but shocks are maximum important to make sure the car handles well.

I barely ever change the "setup" of my car (shims, camber link plates, roll bars) but rather mess about with rebound, shock oil and springs.. The balance of the car is always good. The aggression / feeling of the car can be set with shocks alone.

So long.

Martin.

oh almost forgot: @ cutting edge : I had a look anyway, hope you don't mind :-)
Very nice review, especially as you build it as per instruction first and then start to modify it.
as for the steering: the kit CXL one is purple and spot on in terms of geometry. I did a blogentry about how to shim it when you flip it upside down.

The corally motor is bonkers but hardly legal anywhere. The german rc association allows it in Stock including full grown speedos. That's why I prefer to call it "mature stock" as on most tracks the difference to modified is very small.


Originally Posted by grippgoat View Post
I'm not Martin, but I can give you a bit of info.

If you drill a hole in the center of the shock cap, right by the flange where it mounts to the shock tower, it lets the air escape when you compress the shock. This removes most of the rebound from the shock.

It's a bit of a PITA to make the holes. A pin vise, a small bit, and a lot of patience. You want the hole to come out on the inside well clear of where the bladder seats.

To get a low-rebound setting on the shock, I much prefer the caps drilled, as every time I've screwed the cap down with the shaft compressed, it seems to very quickly pull air into the shock. With the cap drilled, you can screw the cap on with the shaft all the way out, and it'll still have almost no rebound.

-Mike
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Old 03-12-2012, 09:18 PM
  #3410  
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Great post Martin H , off to order some shock tops to drill out and do some testing

Originally Posted by Martin Hofer View Post
You are absolutely right.

On tarmac tracks in general it is very common to drill holes in shock tops not only on our car but on almost everyone.

It will make the car roll a bit more, generate more steering (which is always necessary on tarmac) and just give more corner speed.

I have found that on bumpy tracks (UK!) more rebound is better as there is more contact between tires and surface :-)

The way you drill the hole is explained below.

Why do you drill hole:

we'll to be honest, it's not exactly drill because it makes building the shocks less necessary every other run (as mentioned below) but rather to make the shock work in a different way.
When you have no hole, the bladder seals a air volume between bladder and shock top. This acts like a spring -> that's the rebound you get when building your shocks the regular way, even if you push the shaft all the way in.

Furthermore, even if you build your shocks with the least possible amount of rebound (undrilled still!), the shaft will be sucked back into the shock when it gets pulled out also known as "suck back".

This suck back effect is inevitably and does not harm the cars performance. In fact, it makes the car very reactive around neutral when you run low rebound / a lot of suck back, as the suspension "wants" to compress immediately.

Both effects, the little bit of rebound you always get and the suck back are desirable on carpet but not perfect for handling on tarmac, as on tarmac you aim to have a super smooth and more linear suspension operation.

therefore you drill the shock tops to get rid of both described effects, as with no sealed air volume, the only thing that can cause suck back or rebound is the bladder itself, which generally is quite soft.

Please note at this point: even when you get near no rebound with drilled shock tops even when leaving the shock shaft out all the way during the build, it still makes a difference, where the shock shaft is, when you screw the cap on.

When I run drilled shock tops, I always have the shocks haft stick out of the shock body by 6mm. This is about the neutral position when the car is running -> the bladder is neither being sucked in or pushed out. When you push the shock shaft further in during the build the dampening gets slightly softer , having it stick further out will stiffen up the dampening, even though you use the same shock oil! The difference is not to be left aside!

Well that was a longer entry than expected about drilled shock tops now :-) Sorry for the long read, but shocks are maximum important to make sure the car handles well.

I barely ever change the "setup" of my car (shims, camber link plates, roll bars) but rather mess about with rebound, shock oil and springs.. The balance of the car is always good. The aggression / feeling of the car can be set with shocks alone.

So long.

Martin.

oh almost forgot: @ cutting edge : I had a look anyway, hope you don't mind :-)
Very nice review, especially as you build it as per instruction first and then start to modify it.
as for the steering: the kit CXL one is purple and spot on in terms of geometry. I did a blogentry about how to shim it when you flip it upside down.

The corally motor is bonkers but hardly legal anywhere. The german rc association allows it in Stock including full grown speedos. That's why I prefer to call it "mature stock" as on most tracks the difference to modified is very small.
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Old 03-12-2012, 09:28 PM
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Martin, could you please show us a pic?

thanks,

Rich
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Old 03-13-2012, 03:29 AM
  #3412  
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There is also different density foam spacers which can be placed on top of the bladder between the lid.

They also change the effect and feel of the shocks.

Great stuff to mess around with spent many many days playing with this on a low grip bumpy track years ago.
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Old 03-13-2012, 11:57 AM
  #3413  
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The purple Mi3 shock caps (U3000) are "double drilled", once from the side and once on top above the bladder.
I think they are no longer available at Schumacher but you might find them second hand or as new old stock at your local dealer.
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Old 03-13-2012, 02:38 PM
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Can you tell me if the CXL come with the full sway bar kit or do we have to purchase it separately?
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Old 03-13-2012, 06:29 PM
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Originally Posted by mymax View Post
Can you tell me if the CXL come with the full sway bar kit or do we have to purchase it separately?
it does come with two sway bars.

if you want the full sets the part numbers are
U3921 - Front set
U3922 - Rear set
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Old 03-13-2012, 06:56 PM
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Originally Posted by Magneto View Post
The purple Mi3 shock caps (U3000) are "double drilled", once from the side and once on top above the bladder.
I think they are no longer available at Schumacher but you might find them second hand or as new old stock at your local dealer.
The Mi4 LP and newer shock caps are "double vented". That just means it has one vent on the side where the threads are, and one on the top above the outer edge of the bladder where it seals against the cap. Both vent holes are sealed once the cap is screwed down all the way.

-Mike
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Old 03-14-2012, 09:05 PM
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Originally Posted by olhipster1 View Post
it does come with two sway bars.

if you want the full sets the part numbers are
U3921 - Front set
U3922 - Rear set
Thanks for the info .
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Old 03-18-2012, 05:47 AM
  #3418  
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Originally Posted by grippgoat View Post
The Mi4 LP and newer shock caps are "double vented". That just means it has one vent on the side where the threads are, and one on the top above the outer edge of the bladder where it seals against the cap. Both vent holes are sealed once the cap is screwed down all the way.

-Mike
These are the first shocks I've built that vent the bladder cavity, and what a difference it makes. Best shocks I've ever used.
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Old 03-18-2012, 04:58 PM
  #3419  
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Default 70T 48P spur gears

Anyone finding these a bit fragile/brittle?
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Old 03-18-2012, 06:16 PM
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Originally Posted by celt View Post
Anyone finding these a bit fragile/brittle?
I haven't found any fragile parts on the CXL
But I am using 64 pitch gears.
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