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Just recently was able to snag a Yokomo MR-4BC and MX-4 off of eBay for very little, and got a couple of questions as it relates to the two - specifically, has anyone tried to use any MR-4BX parts on these - front arms/hubs, rear arms/hubs, or universals/cvd's? A lot of the newer 4WD's (TRF501X, B44/BJ4, D4) have very similar front A-arm/rear arm configs - has anyone tried these either? Specifically, I'm looking at trying to start using the standard Losi rear rims and/or front rims (not as critical).

Also, semi-related, has anyone tried using the MR-4TC low-friction universal (CVD) ends/axles on the MR-4BC low-friction universals? Or, has anyone tried MIP CVD axles to match up to the standard MX-4 MIP CVD's (making a bearing change in the hubs) - possibly the RS4 rear axles? This would theoretically allow you to use 12 mm (and width some modification, 14 mm - Schumacher) rims. I did some rough tinkering with spare parts I have lying around, and you can use Tamiya rear axles for the DF03/TG10 and 5X10 bearings in the rear and this will mate up to the standard dogbones on the MR-4BC. This allows the use of 12 mm style adapters. Using a set of standard 5-star/dish 2.2 Tamiya rims, this widens the rear by ~2 mm per side (very rough measurement).

I've got a similar situation on my hands and found the exact same for the DF03 parts.
12mm hexes all around are my goal: don't have the imperial wheels.

MR-4TC parts don't mix with the original CVD's: the cup is on the wrong end or the pins and internals are a wrong size
Don't remember exactly what was the problem, just know I didn't succeed using the MR-4mini axles on the buggy.


For losi rear wheels:
- I think you'd have to use a losi rear axle carrier and drill the hinge-pin holes to imperial size.
-Maybe you can use parts of the kyosho cvd's for the ZX5 (proline wheel conversion),
- or durga axles with df03 dogbones and 4 5x10 bearings will do the trick?

Do you have the MR-4BC SP? That buggy used the same rims and hubs that later went on the mr-4bx.
MR-4bc was pretty much a cost reduced MX-4: ommiting some bearings, lots of carbon, slipper; The chassis was the same a st the mr-4tc and thus the wheelbase rather short: good for short indoor tracks but twitchy for the real work.

I actually have both a MR-4BC (std) and recently got a hold of a MR-4BC SP off of eBay (with, surprisingly, quite a selection of tires, rims, parts) – so I’ll take a look at the rims. But at quick glance, as far as I can tell they are specific (use a different adapter than the std MR-4BC) and don’t match what is used on the MR-4BX (I think).

However, that being said, I may have found some other potential solutions to the 12 mm adaptation using “stock” arms, hub carriers, etc. If you can find them – Yokomo made some “low friction” universals for the BC-series. These are the reverse-MIP-style of CVD’s that are used by Tamiya. Since the config is the same, this should let you use 12 mm hexes. I was able to procure a rear set off of eBay a little while back, but have not found a front set. I have also not been able to get a hold of just the MR-4TC L.F. axles, although complete sets are available (although I’m not keen on the idea of purchasing a set just for the axles). I spent some time trying to find an inexpensive alternative that may work, but the axle portion for this style is often not sold separately. The DF03 CVD axles “may” work and while searching the ‘net, I found this style of axle for the RS4 Pro3/Pro4. So these may work as well… (although that’s kind of a leap of faith)

This leads to option 2, which is finding an MIP axle. I know that most MIP axles use a similar configuration/components, and have seen others mix-and-match (adapting B4 rims to a CAT 3000, etc.), so theoretically it should be possible. The only two companies that use 12 mm hexes that are readily available from MIP are Traxxas and HPI. Originally I thought that RS4-MT rear MIP axles would work, but after looking at the rear hub carriers for the Pro2 and MT, I think this axle would be a bit too long. However, the Pro3/Pro4 looks very similar to the Yokomo hub carrier in size/depth, and I was able to get a set of MIP axles very inexpensively. So, I plan to combine these with a set of MX-4 MIP bones (along with some 5x10 bearings), and we’ll see if it works.

I’ll let you know how it goes when the parts arrive (along with possibly some pics).

Well, I got the parts in and I have good news, and I've got bad news. The bad news is it looks like it won't work for rear axles. I made the incorrect assumption that the 5x10 bearing would have the same thickness as the 6x10 - when in reality, the 6x10 is 3 mm thick and the 5x10 is 4 mm. Blatant oversight on my part - but this additional thickness basically causes the axle to be too short (so, possibly the RS4 MT axle will work in the rear...need to get one to verify). I do not know if 5x10 (3 mm thick) bearings exist, but a quick search did not yield anything too promising.

However, the good news is that with the additional thickness, it looks like the axles will work in the front. The only drawback being that the Yokomo wheel offset does not match up with a standard 12 mm hex - by about the tune of 2-4 mm wider - so may have to play around with thicker/thinner ones to get the appropriate overall width.

Also, the other bit of good news is that it looks like rear bones, combined with these axles will work in the Tomy Intruder. So for those who own an Intruder, this provides a viable alternative to the old school Yokomo setup.

Anyways, for those interested, the HPI PN is 80824 for a set of 2 axles. Tower Hobbies has them http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXAFM4&P=7, and they can be found on eBay as well (depending on where purchased can be as low as $5.50.

when you put those knuckles in the C-carrier: don't the axle cup edges interfere with the carrier when you steer?
I tried several different ones but found nothing that worked well.

I think it would still work - as the interference is very small (1 mm at the extremes) - as the ball of the CVD is the same; nothing that a little dremeling couldn't relieve. I haven't installed and taken it up to speed yet, as I'm waiting on the rebuild components.

I've also found that there was a CVD kit made by MIP for the MR-4TC series - MIP PN 1339 - rear, 134X - front (not sure of the final digit), and the axles out of these would be a direct fit with 6x10 without the need for modification.

The most "readily" available option would be to take the L.F. shafts for the BC, and use L.F. axles for the TC series.

So, it's been a while...but finally got the RS4MT rear MIP CVD axles. This was purchased for another project - but I thought I'd go back and take a look at this again. These are a perfect fit for the rear hub carriers (when 5 X 10 bearings are used in the hub carriers). They are 1 mm thicker, but the additional axle length for the RS4MT matches - so, you can now use 12 mm style hex adapters. You could also try some 14 or 17 mm adapters intended for rim adaptation on the Rustler/Stampede (14 mm is the Schumacher size and 17 mm is the older Intruder style). Need to play around with different wheel manufacturers to see if I can find one that puts the track width the same - but very happy these match. The HPI PN for these is 80818.

Sasha8066 wrote:...
The most "readily" available option would be to take the L.F. shafts for the BC, and use L.F. axles for the TC series.

I think I understood what you refer to, but ifso; it won't work. The cup-shaped part of the cvd is not on the same side between the BC and CT: one has the cup on the bone, the other on the axle.

For the RS4MT CVD's: did you use the rear cvd's or fornt? and whre do you use them: in the front of the yok or in the back?

You are correct about the cup location - but, there are CVD's which Yokomo branded/made for the MR-4BC which they refer to as "Low Friction" universals. These have the cup on the axle/outboard side. I purchased a set of these off eBay to finish out the rear of an MR4-BC Special - so they do exist, but are very difficult to find. They also sell the axles separate but this has proven difficult to find as well. I may end up just purchasing a set of TC CVD's to get the axles. I have not had any luck finding the front version. I suspect that the front CVD's for the Hot Bodies D4/HPI Cyber 10B may be pretty close in length - anyone with one may want to take a look. If you can leverage the MR-4TC components for the axles, this is the most plug-n-play.

For the RS4MT CVD's, you can use the rear axles with the MIP CVD's (the ones that came with the MX4 for example), which has the cup on the main dogbone. These will match up the rear and allow you to use the pin style. For the front, you need to use the 80824 axles, which are shorter than the 80818's.

I've been playing around with the yokomo for replacement axles and shafts to use hex drives and modern wheels. These were for a buggy(870c), but the same principles apply.

I've found that TC5 CVA assemblies work very well in the 870c hubs, and judging by your pictures, look extremely similar to what you have. They are also 6mm in diameter, so you wouldn't need to change the bearings to a smaller size.I've found that these will probably be the best investment, although I will have to stretch the dogbone ends, and utilize 6x10mm flanged bearings in my case.

I know that the tc5 dogbone fits very nicely in the 870c drive cup, it appears to be made for it. If the bone length is correct, this should be practically bolt in affair, as long as yokomo didn't change the drive cup.

If you'd like some dimensions or anything, let me know. The CVA cup part is on the axle, and this assembly seems to have the smallest diameter cvd I've seen yet. smaller than standard MIP, which is smaller than what I think is an hpi cvd(non-mip). I have what I beleive to be HPI parts, but I cannot seem to find another pair like them.

How do you "Stretch" a dogbone? I was at New Era today, and we figured out that you can put the HPI axle (pn103361) in the hubs both front and back, but you need a dogbone from 66-68mm in length, pin to pin, with a 6mm ball, and 2mm wide pins. Sounds easy, but who makes dog bones that length. Can't find anything "listed" at that length....

Thank you for your help so far, this n00b appreciates it.

usually you take a sleeve that is a tight fit on the dogone shaft, cut the dogbone, and add the sleeve in the middle. Adjust to the right length, then glue/solder/braze/weld together.

jwscab wrote: I've found that TC5 CVA assemblies work very well in the 870c hubs, and judging by your pictures, look extremely similar to what you have. They are also 6mm in diameter, so you wouldn't need to change the bearings to a smaller size.I've found that these will probably be the best investment, although I will have to stretch the dogbone ends, and utilize 6x10mm flanged bearings in my case.

I'm pretty slow, but I am starting to understand here...

jwscab wrote:I know that the tc5 dogbone fits very nicely in the 870c drive cup, it appears to be made for it. If the bone length is correct, this should be practically bolt in affair, as long as yokomo didn't change the drive cup.

I'm pretty sure this is an earlier model so I think this would apply

jwscab wrote:If you'd like some dimensions or anything, let me know. The CVA cup part is on the axle, and this assembly seems to have the smallest diameter cvd I've seen yet.

As a matter of fact, I would love some. I am at this point right now:

Chris at New Era and one of the other guys (can't remember who it was, but it wasnt Frank) took apart the hub and saw that HPI part 103361 (rear axle) will fit in the carrier. In order to moke it work, you need a 66-68mm dogbone with 6mm ball and 2mm pins for the drive cup.

This was a cool break through, but as far as I can see, there are no 66-68mm dogbones.

Now, that being said, if the Associated cva kit (part#asc31226) will fit in the hub, with no change of bearings, and the dogbone is from 66-68mm, then I am in business.

I have no idea how to weld/sleeve and make straight a dog bone, and would have to pay to have that done. If I'm going to continue to throw money at this car, I might as well have them make me one off 2.2 buggy wheels with the Yokomo square fitting. I don't want to do that.....

Suggestions?

Can I be frank? You're attacking something very tricky and complicated.
I have done this type of conversion to Hex wheels on a later yokomo than your 870C and it really is not worth all the trouble and money unless you have a stack of wheels and tires already and will use those different tires regularly. If you just want one set of new wheels or even just new tires;
- the smaller innerdiameter tires are still plenty available and very good for bashing.
- used sets of wheels show up regularly for the 870C and would alllways end upo being a lot cheaper than a conversion to 4CVDs plus new wheels, hexes, collars, pins, tires, nuts...

A relatively easier option is to go for the 2.2 yokomo wheels with the same adapter indeed. If you decide to do that you should be able to do all this with less investment and get the correct width.
The TC5 option mentioned here above is not going to work for an 870C: it is suggested for an MX-4=total diferent dimensions.
The dogbone instead of U-J's or CVD's: cheaper but will be tricky with the diffs of the 870C; the bone can slide in to deep and thus cause damage or fall out at the axle side.

Mr. ED wrote:Can I be frank? You're attacking something very tricky and complicated.

yes, I figured this one out. But now, in for a penny, in for a pound.

Mr. ED wrote:I have done this type of conversion to Hex wheels on a later yokomo than your 870C and it really is not worth all the trouble and money unless you have a stack of wheels and tires already and will use those different tires regularly.

I don't have a stack, but I certainly would like the option, this isn't going to be a shelf queen.

Mr. ED wrote:If you just want one set of new wheels or even just new tires;
- the smaller inner diameter tires are still plenty available and very good for bashing.

OK, so I must be searching in the wrong places for 2.15" tires and 2" tires. I have found Losi tires for the rear, but nothing for the fronts. I have found Traxxas tires for the rear that are too wide, but are 2.15". Where should I be looking.

Mr. ED wrote:- used sets of wheels show up regularly for the 870C and would always end up being a lot cheaper than a conversion to 4CVDs plus new wheels, hexes, collars, pins, tires, nuts...

Used sets of 2.2"? As far as expenses:

HPI part 103361 11.95 per set of 2
ACME Buggy Spare Parts: Part# 30048 67mm 1.75 each

If I am wrong, I am out $31. I'm willing to bet one off wheels from New Era, as much as they like me there, are going to cost me 4X that number.

Mr. ED wrote:A relatively easier option is to go for the 2.2 yokomo wheels with the same adapter indeed. If you decide to do that you should be able to do all this with less investment and get the correct width.

Where can I find said wheels? Do you mean getting new ones made? It is still an option however, pricier....

Mr. ED wrote:The TC5 option mentioned here above is not going to work for an 870C: it is suggested for an MX-4=total diferent dimensions.
The dogbone instead of U-J's or CVD's: cheaper but will be tricky with the diffs of the 870C; the bone can slide in to deep and thus cause damage or fall out at the axle side.

Look, I'm new here, and to RC's. My biggest problem is, once I get locked in, I'm locked in. I thought I had quoted a response that was talking about the 870c that JWScab had posted. I'm pretty sure, in fact that I did. Sorry for my n00bness.