Thursday, July 19, 2012

TBs TechReview 15 – 9398, 4x4 Crawler (Addendum)

After one review mainly dedicated to the 9398 4x4 Crawler as a set, it comes now the time to see how it behaves with other tires then the original ones included in the box (54120 - 94,8 x 44R Balloon).
We will be using either LEGO and non-LEGO tires.

So we have selected two additional tire sets, as seen in the picture below.

  • The LEGO Power Puller (PP) tires (32298) for 62mm D. x 46mm wheels, used at the old 8466 and 8475 sets released in the early 2000's.

  • Ansmann tires for 1:10 Wheels Crawler (211000224) - The diameter is 108mm and the width is 40mm, or 4,25"x1,45"- 1,9".
    These have an Inside Diameter of 1.9" (48mm), and their width (35mm) is very close to matching the outermost rim's width (34mm).
    We have here used the breadlock version detached from the original rims, because other versions are supplied with the tires glued into the respective steel rims.
    These tires were brought to the Technic fans attention, by Efferman at EuroBricks. Meanwhile there have been some hype about the 3rd party tires topic and several other RC hobby tires have been reported to fit with LEGO wheels.

Before going forward let me explain something about real car wheels that also reflect in hobby models and naturally in LEGO models as well - Wheel Offsets.

The offset of a wheel is what locates the tire and wheel assembly in relation to the suspension. More specifically, it is the measured distance between the hub mounting surface and the center line of the rim. It can thus be either positive or negative, and is typically measured in millimeters. Offset has a significant effect on many elements of a vehicle's suspension, including suspension geometry, clearance between the tire and suspension elements, etc. If the offset of the wheel is not correct for the car, the handling can be adversely affected.
Visually, the width of the wheel also determines how much of it protrudes relative to the car's bodywork.

Below is an explanation of the various types of offsets which are pictured in the above graphic.

  • Positive Offset: A positive offset occurs when the hub mounting surface is on the street side (the side you see) of the center line of the rim. Most factory rims will have this type of offset.

  • Zero Offset: The hub mounting surface is event with the center line of the rim.

  • Negative Offset: If the hub mounting surface is on the brake side of the center line of the rim, it is considered a negative offset or "deep dish".

Given the high suspension of the Crawler, the first natural thing is to look for larger tires that better fit the wheel space, thus decreasing the suspension travel... This is where the well known LEGO Power Puller tires come to scene.

Equipped with the Power Puller tires, the Crawler gets a more proportional look and the tires also fit very nicely on the model from the aesthetics point of view.

The larger the tires are, the shorter the suspension travel is. Although the difference doesn't seem to be that large. On the contrary, the ground clearance gets significantly improved, even below the axles.

The Power Puller wheels (22969) are asymmetric, consequently they can be assembled either with Positive or Negative Offset.
However in case of Positive Offset, the wheels touch the steering arms generating a lot of friction, hence the crawler performance gets dramatically decreased as you will see from the videos ahead.

To address this problem the correct alternative is to mount them in a Negative Offset setup.

You can see from the image that the deepest wheel side is now faced outwards. Fortunately this option solves the problem and the Power Puller tires get now enough space between them and the steering arms.

With the Power Puller tires correctly mounted, it rolls very nicely but doesn’t perform well as a crawler, despite the softer rubber compound these are made of – Guess the large tires diameter requires more torque which is not available in excess. This is mostly visible in the videos at the end of this post.
Also with such larger, wider and protruding wheels (even more, mounting them on the Negative Offset side), it turns almost impossible to tip over this beast... This is an advantage though!

Now trying with the Ansmann tires!
These are ones from the many tires available in the market for the RC hobby cars, with 1,9" internal diameter. Under certain conditions this is the perfect dimension to fit LEGO 44772 wheels. They do not fit into to mounting grooves at the faces of the LEGO wheels, but given the smaller width of the tires when compared to their LEGO "equivalents" they will fit inner and deeper at the wheels hub profile. Although you need some practice to make them to fit nicely.

If you're looking for some other type of tires to apply on the same LEGO wheels, please notice the inner diameter you should look for might be different. For instance if you're looking for some street or race circuit tires, these will have a different and lower profile which needs to fit the wheel grooves. Thus you need to find a more precise width match and larger inner diameter.

Bellow you can see how the Ansmann crawler tires fit in our model.

These tires use internal foam inserts to be able to sustain the models' weight. Otherwise they would collapse and turn useless.
They have a diameter almost identical to the Power Puller tires, but have almost half the width. Because of this they also allow the suspension travel to remain a bit closer to the original.

The Ansmann tires are also made from a much softer rubber compound and have a tread with a deeper profile which significantly increases the crawling performance.
Another important factor might be that despite these having a comparable diameter with the Power Pullers, they are almost twice lighter, thus having smaller inertia and requiring less momentum to spin..

For reference here we have the weight of each tires (with wheels inserted)
  • Original LEGO 94,8 x 44R Balloon: 56g
  • Ansmann 4,25"x1,45"- 1,9: 96g
  • LEGO Power Puller: 186g

And finally a couple of videos where you can see the custom tires in action.

Indoors performance,

And outdoors,

Notice that all the footage with Power Puller tires, in this video, was recorded with Positive Offset mounted wheels, which is a non-sense because of the increased friction... My bad!

From the final rock track crossing attempts in the second video, it turns out that it should have been easier to try it using the PF IR Speed Remote Control (8879) for better steering and more precise control.

For a reference with the standard tires, you may look at the videos in the Crawler's original review article.

Although we have achieved some fairly good performance with the custom tires (better with Ansmann tires then with Power Pullers), the weakest point for a better crawling and play experience continues to be the differentials used in both axles. Once a wheel gets off the ground, the fun gets suspended as well...
Sariel have tried a modded Crawler version, by replacing these with knob wheels and got some promising results (apart the squeaky sounds), as you can see from his video (notice ha also changed the gear ratio used on the portal axle hubs).

Read this set main review, here.


GuiliuG said...

Thanks for these wonderfull reviews and explanations !

Dave said...

Your detailed analyses explain things so well! TBs is the best at that! :)

Blakbird said...

Thanks for this thorough comparison.

Why do your Power Puller wheels look like they are chrome? I thought these only existed in metallic silver.

TechnicBRICKs said...


You're right they exist in metallic silver only. These look chrome because they were chromed! :)

It took me a thousand e-mails to convince ChromeBricks to chrome them long ago (almost when he started to sell chrome parts).

Unknown said...

I have been looking for the ansmann tires, but in vain. I couldn't seem to find the correct 1.9" diameter. Could you provide a link to the right set. Thanks in advance.

TechnicBRICKs said...

I've bought mine, here:

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