Schumacher Mi4cxl Build Review

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In December 2010 I did a review of the Schumacher Mi4cx (you can see the review here) – I was very impressed with the car then and the Mi4cxl is the latest incarnation of the car. Chris Grainger, Martin Hofer and the rest of the team at Schumacher UK have been working hard to tick all the boxes for the new breed of touring car. The new car is an evolution, not a revolution, in that Schumacher have built on the already great CX platform which built on the Mi4LP before that.

The major changes for the new car include;

  • NEW 2mm Aerospace carbon fibre “Soft Weave” chassis and long top deck with optimised flex. Easier to drive with more traction.
  • NEW Extreme lightweight 7075-T6 transmission housings.
  • NEW Anti-Roll Bar system, lightweight with a near linear response.
  • NEW Bridged layshaft mounting with quick release layshaft design for ease of maintenance.
  • NEW CNC alloy, 20 tooth layshaft pulley.
  • NEW Steering geometry incorporating centre point steering with forward facing balls to fine tune geometry. Fully adjustable Velocity Ratio, Ackermann Angle and Ackerman Rate.
  • NEW Stiff 3mm rear shock tower with more shock mounting positions.
  • NEW Carbon Fibre wishbones with moulded Roll Bar Ball, for increased traction, lighter weight and better impact absorption.

Some people did complain to a certain degree about the fact that the car was not completely new and Matt White, one of the Schumacher UK drivers, put a very good post on the Schumacher Forum addressing peoples concerns;

“When looking at the CXL I think it’s important to look at it in comparison to a standard CX kit. There are quite a few differences.

The chassis is the Soft weave carbon that we have been working on for quite a long time and has been available for a while. The chassis now has adjustable battery position., this is a valuable option, as we’ve found that moving the weight forward is a good thing. The top deck is now longer, and we know that this makes the car easier to drive.

The Roll bars are more consistent, when the old bars are all setup and installed properly, then it is quite possible to get the old bars working fine – but it is a lot harder, the new setup is much easier.

The alloy layshaft pulley, small change I know, but improves the reliability of the car.

New steering geometry, this gives the car more steering which is something that we found we were looking for a lot of the time.

There are quite a few changes, and it’s the culmination of development of the Mi4 platform. I don’t think there can possibly be any debate that as a kit it’s a big improvement over the Mi4 CX.”

I could not have said it better myself so on with the build…

After opening the box you are presented with a number of plastic bags, a nice bag of carbon parts including the chassis and the typical Schumacher manual;

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Also included is a decal sheet and some advertising leaflets showing the nice range of EDS tools etc. that Schumacher also distribute.

Each of the plastic bags, in turn, contains the parts for each of the steps that are decribed in the excellent manual;

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As you can see in the picture below Schumacher provide all the information in a really clear manual and if there is anything different about a step or possible options these are explained.  In the pages below the different transmission options are shown (i.e. which side the main belt is on) and the reasons why you would go with options 1 or 2 – I along with the team drivers went for Option 2 but, as described in the manual, if you have heavier electrics then option 1 may be the way to go. I use a Speed Passion GT 2 speedo and Sanwa receiver along with a short servo.

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As I said earlier something that Schumacher do very well is mark each bag for each step in the instruction manual. So, in the manual step 1 is screwing the rear bulkheads onto the chassis so in bag 1 you will find the bulkheads and required screws, no more, no less. When you are finished a step you do not have left over parts that are for another step. The picture below shows each bag for steps 1 – 10;

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This means that it is easy to follow and you only have the parts in front of you for the step you are working on… makes life very easy!

So let’s begin the actual build process by looking at the chassis and alloy bulkheads. The chassis and other carbon parts are really well made and as per all my other builds I started by sanding the edges of the chassis and sealing it with glue. I don’t do the other parts, just the chassis. The chassis supplied with the kit is the 2mm Aerospace carbon fibre “Soft Weave” chassis and the long top deck is the same with optimised flex. This is all designed towards providing more grip… you will see as this review goes on that I talk about grip and steering and how the changes made for the Mi4cxl mean you have bags of both.

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The next stage is to start screwing the black 7075-T6 alloy bulkheads onto the chassis. Schumacher supply tools for doing this but seriously if you are building a kit of this quality it is worth investing in some decent tools. As I said before Schumacher do a range of red EDS tools and they are worth getting as they will last a long time and you will want quality tools for maintenance etc. after the build.

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The bulkheads attached;

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And a close up just to show you the quality and the reminder that they are 7075-T6.

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Believe it or not, by this stage I am up to Page 3 and step 4 (it’s a 37 page manual!). Next is the centre pulley and Schumacher have included an alloy pulley which was an option on previous kits. The 85 tooth spur gear screws on to it nicely using four screws and sandwiching a bearing in between it and the pulley.

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Another change to the cx kit is the use of a bridged layshaft mount – on the cx the layshaft ‘floated’ in that it only went through from one side and did not connect to the other bulkhead. This has changed in the cxl and there is a connection to the other side. The picture below shows the short side screwed into the bulkhead.

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The picture below then shows the long layshaft that screws through the other bulkhead, through the pulley and spur gear and meets up with the other side of the layshaft. Believe me a lot harder to describe than to build! Taking the layshaft out allows easy removal of the spur gear and pulley.

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And here is the layshaft in place along with the belts – remember to put it together as per the option you have chosen dependent on your electrics etc.

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If you look closely at the picture above you can see a washer to the right of the chassis… I did play about with whether the layshaft needed shimmed slightly to stop it moving side to side but in the end decided I was happy with it without anything.

On to the rear diff now and a lot of people questioned Schumacher supplying a ball diff rather than a gear diff for the rear of the car. Nobody questions Schumacher’s quality diff but most other manufacturers are now supplying a gear diff and spool in the kit.

The picture below shows the parts for the diff and I use Schumacher diff lube and Associated black grease when building diffs (for any car). Schumacher supply a ‘bag’ of black grease and diff lube.

The diff uses a cir clip to hold the thrust race etc. in the outdrive so if you have not got a pair of circlip pliers I would recommend you get a set – Schumacher do a pair, part no. HW010 I believe, and it just makes life so much easier.
Once the diff is built you then add a plastic sleeve and then over that a 7075-T6 metal sleeve. Quick tip here is that there is a rubber O-ring that goes on before the sleeves – just wet it ever so slightly and gently push the sleeve over it – once in place the sleeve will not simply fall off.

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And the completed ball diff…nice… and very smooth. Remember to put the grub screw in opposite the diff screw and the end and ensure that it is tight to stop the diff loosening.

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Having built up and run the diff with the kit and found that it was so much easier to drive in 10.5t on carpet I am more than happy with Schumacher supplying a ball diff in the kit – I have a gear diff already bought and built up but it has never made it into the car yet.

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The picture above shows the diff fitted. I like the fact that the diff holder for adjusting the diff height and the belt tension has high and low written on it to make it easy for people like me to ensure that the diff is definitely at the desired height on both sides.

You can also see the new ‘holders’ for the diffs and this is, for those of you who haven’t got the long top deck conversion on your cx, the rear attachment for the top deck. It does mean that you have to remove the top deck to take the diff out but for the difference in grip levels that the new layout makes to the car I don’t mind at all.

So next on to the spool and belts… The spool is a work of art made from one piece of 7075-T6 alloy;

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Schumacher supply you with the two options for the sliders that go over the outdrives for both the spool and rear diff which come in two levels of hardness. The also provide you with a separate sheet describing the different characteristics;

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I went with black on the front and rear and to date have had no issues.

The spool built up and ready to go into the car;

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Fitting the spool is the same as the rear diff and again you can use the pin in the diff mount to set the belt tension. I ended up on pin level with the silver dot on the rear and the dot one down on the front.

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The picture below shows the diffs in place and belt fitted;

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The top deck is put in place with some pretty long screws front and rear (M3 x 30mm!) that go right down through the diff mounts, two shorter M3 screws at the motor and four short M4 screws front and rear. Make sure that, before fitting the top deck your chassis is perfectly flat by putting it on a piece of glass or other flat setup board. And then when you are fitting the top deck keep the chassis flat and screw the screws in triangle sequence; so front left screw first, then rear right, front right, rear left the move on to the M4 screws in a similar way and finally the two motor screws.

With the top deck in place the car looks like it is really coming together;

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The top deck that is supplied with the kit is a tarmac one as shown above and I purchased the U3914 carpet spec one as well as I planned my first run to be on carpet.

Next we come to the upper link mounts that screw into the front and rear bulkheads. There are different places to put washers to makes changes to the front and rear suspension link and again there are some details on this in the manual, in the setup section at the back. The kit comes with the 3 groove 39mm links but I know that some of the team drivers have been using the optional U3799 4 groove 37mm link instead and this is the version that is on Chris Grainger’s carpet setup detailed in the manual.

The mount in place along with the ball studs in place;

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From the rear;

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The steering part is another new piece with slightly different geometry which is designed to give the car more steering which is something that people struggled with when using the cx.
The steering in the car is built up from a nice piece of purple alloy with washers fitted to give different ackerman (simple and it works!). This all rotates on two bearings on a metal post and finally attached to this is a piece of carbon fibre to allow you to attach the steering to your servo horn and servo of choice.

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In the picture below I built the steering up as per the instructions with 3mm of spacers for ackerman but it is far too much and makes the steering far too aggressive – the team drivers have gone to 1.5mm but I settled on 2mm. Something to play about with.

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The rears are step 19 in the build and the minor change here, to the previous car, is the moulded connection on the arm – this is to connect the roll bars to in their new configuration.

The Schumacher excellent driveshafts are still here with the rear measuring in at 44mm and the front 45.70mm.

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All the parts go together very smoothly and I did not have to ream out any of the arms etc. to get them to rotate on the hinge pins.

You may also notice that I use alloy washers to space the arms on the hinge pins – the car comes with plastic clips but the washers are just a personal preference.
And here are the arms all ready to go onto the car, complete with turnbuckles;
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And nicely fitted to the car;

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The side view;

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The turnbuckles are nice gold coloured items and Schumacher supply a carbon fibre tool for building the turnbuckles. I used one of the EDS turnbuckle tools to turn the turnbuckle while holding the ball end with the carbon fibre tool.

Schumacher also do a full set of purple titanium turnbuckles (U3516) and this is on my shopping list – a bit lighter and fits in well with the overall purple look!

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Next in the build is the front arms;

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All the parts including driveshafts, bearings and hubs;

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The kit comes with the flex front yokes (hub carriers). In the past I have found that these give a lot of steering/grip almost to the point were it can feel like the car is digging in when cornering. I have already bought a set of the medium flex ones (U3748) still in four degrees. Again personal preference but something that is worth trying.

Built up ready for the turnbuckles and hinge pins etc.;

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And all ready to go on the car;

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All fitted and connected to the steering;

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Front view just before the shocks go on;

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Now at step 31 the front shock tower is fitted. I already had one of the front shock towers with the additional hole for a third body post so I decided to fit that. You can see the difference in the two in the picture below;

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And fitted with the third post in place;

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The rear shock tower is also screwed into place;

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It is amazing how many parts go to make up two pairs of shocks;

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The shock build was very good and for those of you that have built shocks from different cars I would say that the Schumacher ones are up there with the best. Some people swear by Tamiya shocks and I think that Schumacher’s are easily as good. Schumacher even go as far as providing a bottle of 35wt shock oil although I went with 50wt for my initial carpet setup;

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A great purchase is a shock pump which speeds up getting all the air out of your shocks when doing the build;

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The shocks all completed and set to 25% rebound;

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I bought two sets of the SpecR spring sets part number G882 when buying the car – these are nice black springs and are the ones that are named in Chris Grainger’s carpet and tarmac setup in the manual. They are a good price for four sets of springs in each set costing around £10.99.

Front shocks in place;

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And the rear;

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Over half way through the manual and the new roll bars are ready to go on;

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A lot has been said in the past (mostly bad) about the roll bars – I never really had an issue with them but some people complained because they could not be adjusted up and down at the mount points on the arms to allow for tweak etc. This has been addressed in the new version with the arm mount points made up of two ball ends and a long grub screw;

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They go together nicely with the supplied spacers in between;

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And they are mounted to the bulkheads with a screw and a grub screw to stop too much movement;

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Top view of the rear roll bar;

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Front bumper parts ready to be build up;

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With the bumper you can raise and lower the body posts by loosening off a grub screw, moving the posts up or down and retighten. Great for a quick bodyshell change;
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I also had an alloy servo mount (U3571) lying around so more purple bling for the car;

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And next up is one of the features that I think is the most innovative on the Mi4 family of cars and makes the car really easy to spot in the pits; the motor mount. Schumacher made a great clamping system that allows the motor to move in and out of the car (remember the two belt options I described earlier) and it also allows you to move the motor forward and back on the car. This is great during a race day when you want to take the motor out without changing the pinion and gear mesh – you simple unscrew a screw at the bottom of the motor clamp and the motor, with pinion attached, can be taken out of the car. Bearings etc. in the motor checked you simply slide the motor back in and the mesh is the same and you just tighten up the screw again.
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The bottom screw for tightening the motor in place;

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And that sadly is the car nearly complete, just electrics and tyres to go;

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Front steering and roll bars again;

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Rear showing the other side of the layshaft mount;

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And a nice top down view showing the two slots for the battery tape allowing you to move the batteries forward or backwards depending on the grip required;

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Servo and electrics wise I use a KO 2413ICS servo – bought a few years ago and still going strong. I don’t use the servo saver option that is supplied with the kit and designed to give a bit in a crash. Instead I use the non-saver version that is also supplied in the kit. You do risk damaging the servo in a heavy crash but I just prefer the feel of it. My speedo of choice is the Speed Passion GT v2.0 in carbon look (SPEXT98802PRO) and I use the 323STOCK version of the Speed Passion software on it and a 10.5T Speed Passion version 3 motor (SP1C105V3) – a nice fast package and easy to program and setup.

I also installed the U3513 Lipo nest to hold my batteries in place. I don’t use the lipo strap and just tape my cells in.

Setup wise for my first days racing which was at the UMCC’s indoor meeting at Bangor I put Chris Grainger’s carpet setup on it exactly as per the manual. This did involve me installing the 4 grove upper link mount 37mm (U3799) front and rear and I went with 2mm on the steering ackerman (slightly more aggressive that team setting of 1.5mm). I had the gear diff built but went with the ball diff to start. The car was very good – it generated a lot of grip and the steering is amazing. At one point I overshot a corner going too fast and when I turned in the car rotated very nicely, gripped and turned in. It is hard to describe the grip and the steering compared to the older CX – it could be the setup but I believe that it is down to the chassis, top deck and the new steering.

For may second days racing I went to the medium flex yoke (hub carrier) as it allowed me to carry more corner speed. I had an ok day and ended up in the B final but my fastest lap of the day was an 11.82 second lap and if I had managed to put together 25 of those I would have made the A. So the car is very capable and the driver is capable for at least one lap so we shall see what comes in the future… watch this space.

Thanks again to Chris Ashton at Schumacher for sorting me out with a kit and to Chris Grainger, Martin Hofer and all the team at Schumacher for another great car. As I finish this article Chris Grainer has just finished 7th overall at the latest round of the RedRC ETS competition in modified and Martin Hofer 2nd in the Pro Stock.