Mjk Tyres - Thoughts

[GAS41T]

Jphanna

Ring Ian his a great bloke....

I got a sponsorship of him for a proxy & wow the goodies I got.... the cola tyres for wrp 5/6 pairs, rims vintage tyres galore raid tyres aswell as I said his a gentleman

Ps you could probably be that guy with 25shore 😁

Rossko

Edited May 15, 2017 by GAS41T

[Slotspeed]

What material are MJK tyres made from? I'm seeing one site describing them as rubber, and another as Urethane. I see good reports on this thread here on regarding Carrera track, what are they like on the bumps and inconsistencies? I had NSR supergrip rubber tyres on one of my cars, it was very smooth running on the Carrera track. Another car (same make and model, similar mods) had Paul Gage Urethanes and was noisy as, could hear every track section as it went over the junctions. I kind of didn't like it. Performance between the two tyres was about the same.

[munter]

IIRC MJK tires were urethane...not sure on hardness(shore) but they will be harder than the NSR supergrips.

 

Most factory urethanes are round about 30-40 shore hardness.

 

My home cooked urethanes are 40 shore.

[Peter Gunn]

Slotspeed been running on a large Carrera track for 5 years now and of all the tyres i have used my main tyre is now MJK's was introduced to them 4 years ago and find them the best , also they are made well you can find a tyre to fit most wheels , use their 20x10 on my slot it group C's and they are great, most of the time i don't have to true them , and they are urethane

[kalbfellp]

It is not the material but the hardness that makes the NSR smooth. MJK I think are 40 shore. NSR have tyres down to 25 shore, depending on what sort you are using. I think the supergrips are around 35. But they are rubber.

Paul Gauge make different hardess tyres, normal are 40 and the XPG seem to be around 30. Although someone mentioned 20 but they are not that soft. They test around the same as my 30s

Edited June 30, 2018 by kalbfellp

[munter]

I bought some PG tires for my Cox Cheetah....when I asked he told me they were 20 shore hardness.

[SlotsNZ]

Just caught up with this thread- it started while we were overseas

I had MJK pegged as 40 shore. I was making 40 and experimenting with either 30 or 25, or both. I forget

As for treating - you CAN treat urethanes and they will go faster- so the no-treat simplicity isn’t reliable. The treating though will kill them in a couple of months

 

NSR supergroup is 25, ultragrip 18 or 16 depending on who you believe, and the Slot.it tyres are of course as they describe.

Sideways do roughly 40, 30 22

Scaleauto range from 40 to 20

 

I suspect MJK especially suit tracks with textured surfaces and unlike “rubber” tyres, scrub dust and their own “sheddings” well, especially on such textured surfaces so hold grip better through a race in dusty environments .

Of rubber tyres Slot.its N22 seem to be about the easiest to true, having a feel on the lathe similar to Urethanes

-I can do a single tyre in 10 to 15 minutes reliably

[kalbfellp]

Pig tyres certainly do not measure 20 Shore A.

Measuring actual tyres is very difficult owing to the size and shape,even with a special Durometer.

20 Shore Eurethanes are very soft more like the NSR Extremes to feel.

Making Eurethane tyres is not an exact art.

The small batches that they are made in can lead to variations is hardness, MJK are probably the most consistent.

Slight variations in mix, pigment and cure time all make a difference.

Shelf life and heat also cause variations..

 

[ZeGas]

The way I measure shore rating is with a durometer, the way to do it is to take the tyre from the package and do not mount on a rim.

Use the durometer with tyre upright, depress into the tyre until the durometer needle base is fully depressed onto the tyre.

I am getting very consistent readings that way.

MJK's come out between 38-42 shore so 40 average.

Ortmann's (urethane) are pretty good and are a bit softer than MJK at around 30-35 shore, I've had some good results with them.

Slot.its are within 1 shore either way of their official rating.

NSR are usually spot on their rating with the occasional deviation of 1 or 2 shore.

 

I agree with Mark regarding MJK's being better suited for textured track.

If you have a smooth track and cover your track from dust or clean thoroughly and regularly and are serious about racing then go with the NSR or Slot.it rubber tyres.

If you are wanting consistency but not necessarily speed, like if you are mucking around with the kids etc. then urethane are the way to go.

They aren't that much slower

 

Just remember the softer they are the quicker they wear out.

[kalbfellp]

I am surprised that you manage to get good consistent readings. Even on large diameter rollers I have found that the readings vary from roller to roller by as much as 3 Shore.with rollers from the same batch.

Ottomans are not a normal Eurethane ,if you believe the manufacturer! Supposed to be a special mix.From what I can find out they seem to contain a small amount of silicon.

[Slotspeed]

Interesting comments, and it seems the MJK tyres are very popular here. I've never used them, but I already like that they list the full dimension of the tyres, and not just a howdy doody half cocked measurement system like most manufacturers, but I guess that's because they aren't trying to sell you a tyre and wheel package, rather they are trying to see you something that will fit what you already have. I will try them at some point. I have some rubber tyres on order so that will be my entertainment in the meantime. The PG tyres that I was using were XXD.

 

My brother is a specialist in OEM and aftermarket automotive Urethane products, both in mould tooling and has experience in different types of Urethane mixes. I know through this connection that Urethane's aint Urethanes. There have been a lot of advances in all sorts of properties for the automotive applications market. I suggested to him ages ago (before I even got back into slotcars) that he should consider making slot car tyres, but not much point now since there are many options anyway.

 

Cheers.

[munter]

some great typos in this thread...

Pig tyres certainly do not measure 20 Shore A.

 

Well Mr Gage did say they were A20shore. Maybe when he mixed and made them they were 20 shore but then somehow got harder.

[kalbfellp]

I have compared PG XPG to my 20 shore and they are harder than mine. The readings are around 28 to 32 shore on my Durometer..

My 20 Shore narrow tyres are just too soft for the Tasman cars and tend to roll in the corners 30 shore seem to be about the limit for the Tasman cars.We were running 35 this year and that seems good.

As we know any slight variation in the mix or pigment percentage can make a difference.

Paul may use a different pigment that make the cured product harder.

[munter]

so do you reckon the pigment hardens or softens the final result?

[kalbfellp]

John I can only speak about what I use. Too much pigment seems to slow the curing and soften the tyres,but it also may be the curing time/ temperature.The pigment is very hard to measure in the quantities I tend to use.

My experience is more with industrial quantities of Rubber,Eurethane and combinations, used in rollers.

I will get my Durometer recalibrated later this week and try and do some more testing.

 

[dangermouse]

The grapevine says different pigment levels and colours can effect the overall properties of the tyre. Apparently a drop of red dye in the mixture results in a slightly softer tyre. I haven't tried it myself because a) I am happy with my current tyres and I am too tight to cough up $$ for some red dye just to find out if it makes a difference that I may not want anyway

[Slo]

Mjks are a good choice for rally it seems Caddo, and they might be a good, but forgotten tyre choice, for lower power planted cars too without goo, just good ol' water (H2 0)

 

Back to the Hijack.......?

 

I too asked Paul back in 2012 and told XPG 20 shore, PG or whatever his PG was called then, 30 shore

Maybe its a thing to protect the manufacturers. ie, Flexicast 20 might be higher shore to ensure it does not go under 20. That probably varies from manufacturer to manufacturer??

Also, how does the durometer work? Does it vary in readings from a tyre pulled taut over a larger rim to that of one not so taut on a smaller rim?

I've run the same size urethane tyre on a correct to scale rim and it was not taut and handled much like a low PSI tyre with plenty of roll, as Phils Tasman reference, and feathering wear on the sides of the tyres. Do mjk's use a green pigment? PG tyres seem to have a red tinge.

[kalbfellp]

Stu measuring a slot car tyre is very hard as the sample material should be 1/4 inch thick and the Durometer held on the sample at a persisting pressure and for a given time.

Field testing with a small Durometer is only an indication, proper testing needs to be done in a lab. I have done some lab testing at a roller factory and then retested once the rollers were here with a Durometer, the readings varied by about 3 Duro.

The Durometer works by pushing a special shaped cone into the rubber at a specific pressure the amount of penetration relates to the hardness.

 

[Slo]

Not many tyres in 1/32 would be 1/4" thick, unless tested on the sidewall.

Sounds like the taut tight tyre will give a higher (harder) reading? I wonder if it's those anomalies that ZeGas was getting to with testing unmounted...

 

The old feel for tac or thumb nail test might not be a reliable yardstick but its what most of us use I guess.

I would imagine the way the tyre is trued could effect the shore rating, especially if the tyre changes temperature ( with in a range) ?

[Slotspeed]

I'm no scientist or tyre expert but I would have thought the internal molecular or atomic structure (I really should have listened in science class!) of the different materials would affect the way a tyre works as there are more properties than just hardness. I know the full scale racers on the club level love to stick their thumbnails into tyres! Sorry for the hijack. Its an interesting topic!

[r377]

I personally dislike MJK tyres, I would take paul gage any day over MJK tyres.  The Yanks have tested them and paul gage come out on top.

 

If you run ferrodore go paul gage, if you run on wood any silicone tyre would be better, usually around 0.3 faster per lap vs MJK

 

MJk are harder to true and leave rubbish all over your track

[gref]

never had an issue with MJK, always served me well. All my race cars are fitted with MJK. Run on Ferrodor, and other surfaces. Tyre truer or or by hand and they come out good everytime

[Wobble]

5 hours ago, r377 said:

MJk are harder to true 

Who told you that? They true up pretty easy for me.

[mattcrackers]

We use MJK on all 10 classes at WASCRG.

No problem with truing them, actually the easiest to true in my opinion.

Australian made too.

[dangermouse]

Not quite the record for old thread revival - funny to revive a thread to bag MJK tyres

I use a heap of different tyres - my own home made Shore 40 urethanes - Paul Gage standard and XPG (never again with XPG) MJK, Frankenslot, Ortmanns, Slot Invasion, Supertyres and probably one or two others as well.

MJK are fine tyres - they are nice and round and you can run them straight out of the packet no problem. They true up well and are comparable in performance to any of the other Urethane tyres out there. We run on MDF routed wood tracks and they hook up fine.

cheers

DM