Mjk Tyres - Thoughts

[Caddo]

Hi all

 

A recent change of events in the local club racing scene has got me thinking about tyres. For years I have avoided MJK's/urethanes, and pushed for classes to run rubber tyres with shoulder/air rims.

 

The laptime gain using rubber tyres comes at a cost though. Slot It N22's are more difficult to true, deteriorate more quickly, and are treatable with oils etc.

 

I was an enthusiast for these rubber tyres, but have come full circle and now find myself pushing to use MJK's.

 

Main reasons being MJK's are:

 

Aussie made

untreatable

easier to true

longer lasting, with wider performance window

supplying a wide range of tyre profiles

slightly lower traction level slows cars to more realistic speeds and forces drivers to drive well or lose time with sliding

 

 

Most of our classes are 1/32 12V mag free with maximum 23000rpm motors.

 

I am wondering how many clubs regularly use MJK's without track goo etc, the benefits observed and the reasons for adopting them initially.

 

Cheers

 

Caddo

[kart.68]

Hi, I race at Way2fast Canberra no goo 1/32 with MJK tyres with good results and Paul Gage are good as well.

Edited May 7, 2017 by kart.68

[mattcrackers]

At WASCRG (West Australian Slot Car Racing Group) we have used MJK's for all classes except for the NSR GT's and NSR Le Mans classes which use the standard NSR tyres.

 

We run on a 4 lane timber track painted with Ferrodore, no goo or other additives allowed.

 

This year is the first time that the rules state that all classes must use MJK's only, no other tyres are allowed.

 

I have noticed that the lap times have slowed a little in the NSR Le Mans class, there used to be a few of us getting in the 5.7 sec per lap but now the quickest is around 6.2 sec.

 

The NSR cars now have to be driven a little different to before due to some loss of traction, you don't seem to be able to go as hard as you could using NSR's own tyres.

 

Personally I would have liked to of stuck with the NSR's on the NSR cars but it's no real loss, everyone is using the same tyres so no one is disadvantaged anyway.

 

The owner of the track, Syd, has said that by using the same type of tyre for all classes that the traction should not differ between classes as it can going from different tyre types.

 

cheers

 

Matt

[kalbfellp]

If you are now using treated runber tyres, you may have trouble convincing the racers to change especially on the faster cars. We run eurethane on the lower powered cars, but find that they are have much less grip on the faster cars than treated rubber.

[shadow_rusty]

MJK's are my go to tyre.

Yes they typically have less grip than the 'correct' rubber, but as every surface type seems to have a different correct rubber, they play the averages well.

Also, they are great on Scaley track where most rubber does not work well.

 

And yes, in high torque, high rpm cars, rubber will usually be quicker.

[Caddo]

At WASCRG (West Australian Slot Car Racing Group) we have used MJK's for all classes except for the NSR GT's and NSR Le Mans classes which use the standard NSR tyres.bunch of racers Pity you guys are 4000km away, good to find another like minded bunch of racers though

We run on a 4 lane timber track painted with Ferrodore, no goo or other additives allowed. Should have mentioned, our tracks are gloss or satin finish, no goo either.

This year is the first time that the rules state that all classes must use MJK's only, no other tyres are allowed.

I have noticed that the lap times have slowed a little in the NSR Le Mans class, there used to be a few of us getting in the 5.7 sec per lap but now the quickest is around 6.2 sec.

The NSR cars now have to be driven a little different to before due to some loss of traction, you don't seem to be able to go as hard as you could using NSR's own tyres.

 

Personally I would have liked to of stuck with the NSR's on the NSR cars but it's no real loss, everyone is using the same tyres so no one is disadvantaged anyway. Good point, lap times are only relative to other racers

The owner of the track, Syd, has said that by using the same type of tyre for all classes that the traction should not differ between classes as it can going from different tyre types. KISS, not the band, the simplicity. We have also found mixing urethane with rubber tyres can result in varying grip levels from heat to heat.

 

cheers

 

Matt

If you are now using treated runber tyres, you may have trouble convincing the racers to change especially on the faster cars. We run eurethane on the lower powered cars, but find that they are have much less grip on the faster cars than treated rubber Copy that Phil, it's like asking them to cut off a limb! I've done scale calcs based on lap times on my small 16m track, and we are doing 410km/hr scale speeds with GT3 cars on rubber tyres. MJK's bring this down to 330km/hr, a little more realistic, with the added bonus you can catch a glimpse of the car as it passes by. Also makes for longer racing battles with fewer offs.

MJK's are my go to tyre.

Yes they typically have less grip than the 'correct' rubber, but as every surface type seems to have a different correct rubber, they play the averages well. Great point SR, they also stay consistent from meet to meet with little change in performance. Maybe need a light sand and off they go again.

Also, they are great on Scaley track where most rubber does not work well.

 

And yes, in high torque, high rpm cars, rubber will usually be quicker.As Matt mentioned, if all are on MJK, does it really matter?

Hi, I race at Way2fast Canberra no goo 1/32 with MJK tyres with good results and Paul Gage are good as well.

Thanks Kart, what is the track surface? Happy to stay with MJK though, made locally

[difinity]

On mostly semigloss routed tracks, I run a mix of MJK, Paul Gage XPG and sometimes slot.it rubber.

I find the NSR prep and truing beyond my ken for now.

The urethanes seem more forgiving, with MJK better on Ferradore. (Don't know anybody who still uses that though - most of our ferradore tracks have been redone in a semigloss - improves grip, clean with a damp rag, can run any tyre incl foam if needed.

The rubber tend to slide around a bit until the track is 'rubbered in'.

Don't mix silicone though, and lubricants like WD40 tend to turn urethanes to mush very quickly.

[ZeGas]

Grip is like for like.

A rubbered up track will grip better with rubber.

I have coated my track with Cabots floor clear urethane and guess what, the MJK's are just fine as are other urethanes.

Rubber not as good.

[GAS41T]

Rubber is best on my track suede with cabots clear...

But eurathane is great for restricted slow motor class cars

I tried mjk on my IPS proxy car but the ninco rubber was quicker & nicer to drive consistently

Rubber is my preference

 

Rossko

Edited May 8, 2017 by GAS41T

[jphanna]

IN my Monday night club, we use MJK for all motors under 18K. they are fine with lower performance motors. over that in grunt, we use F22 or N22. its not much fun having a high performance motor, with MJK style tyres. just fishtailing constantly on some of the tracks. weights dont seem to help that much either.

[munter]

What shore rating are MJK?

 

There are a few choices of hardness when casting tires.

[Caddo]

Probably my last multi quote, relax

 

I find the NSR prep and truing beyond my ken for now You and me both Difinity, life is too short!

Grip is like for like.

A rubbered up track will grip better with rubber.

I have coated my track with Cabots floor clear urethane and guess what, the MJK's are just fine as are other urethanes.

Rubber not as good. Interested if your track surface is ultra smooth, we've found the same thing on a high gloss, smooth track. Rubber starts off very quick, but as the rubber builds on the track, the lap times slow. Found urethanes much more consistent from start to finish.

IN my Monday night club, we use MJK for all motors under 18K. they are fine with lower performance motors. over that in grunt, we use F22 or N22. its not much fun having a high performance motor, with MJK style tyres. just fishtailing constantly on some of the tracks. weights dont seem to help that much either That is part of the attraction of MJK for me, there is no real advantage in overpowering them.

We ran a host class with Nissan R390+30K IL Shark, Audi R8+21K AW King, and Audi R8+22K AW SHark and all on MJK with air/double shoulder rims. Most of us were circulating all 3 cars within a tenth of each other. John, curious if you are using air/double shoulder rims?

Rubber is best on my track suede with cabots clear.., gday Ross, satin or gloss, smooth or rough finish? I've coated my Cabot's satin clear with gloss to improve the traction for MJK's

But eurathane is great for restricted slow motor class cars

I tried mjk on my IPS proxy car but the ninco rubber was quicker & nicer to drive consistently

Rubber is my preference Agree that generally MJK's a little slower and not quite as grippy as rubber, but have other good points rubber doesn't.

 

Rossko

What shore rating are MJK I had in my head ~40, but not 100% sure. They do feel firm, the double shoulder rims help cushion the ride abit

 

There are a few choices of hardness when casting tires. Would be interested in having a crack at making my own, is it difficult? Any tips?

[Lloyd Lucas]

Slightly on topic, slightly off. What are MJK's like on a carrera track? I've been using silicone and its ok, but some cars they just dont grip at all.

[Peter Gunn]

Hi Lloyd i have a 2 lane circuit built out of Carrera track and also have experiance of racing on a 4 lane Carrera track and the MJK's are my choice of tyre on nearly all my cars , they are round to start with which helps and only need a little truing in the odd case, i have them on cars ranging from 16k to 35 k motors and really find them very good , don't forget the Carrera track is very grippy so you get a fair bit of wear with those tyres. don't recommend mixing silicone with urethane though

[jphanna]

What shore rating are MJK?

 

There are a few choices of hardness when casting tires.

 

As far as i know we just get one shore here. it feels like 30.....i cant be sure of the shore!

[munter]

Sure thing.....

 

30 should be quite a softy.

 

I have made a few using a 40 mixture which seem to work fine.

 

To be sure, to be sure.

[kalbfellp]

John the MJK,s that I have here measure 40 shore A, do not know if that is the only harness they use.

[munter]

Thanks Phil. I have used MJK before and thought they were about that. Mark Burgess experimented with softer mixtures and gave me a set(4) to try.

They worked well.

[kalbfellp]

I find that 30 is a bit soft for most cars on our tracks,so mix to get 35 Shore A, we only use Eurethane on a few classes and they are all high profile.

[Lloyd Lucas]

Hi Lloyd i have a 2 lane circuit built out of Carrera track and also have experiance of racing on a 4 lane Carrera track and the MJK's are my choice of tyre on nearly all my cars , they are round to start with which helps and only need a little truing in the odd case, i have them on cars ranging from 16k to 35 k motors and really find them very good , don't forget the Carrera track is very grippy so you get a fair bit of wear with those tyres. don't recommend mixing silicone with urethane though

 

 

Thanks Peter, when/if i change over I'll change all my tyres to mjk's.

[kart.68]

Hi, Testing today fly Lancia 037 no mag on Carrera track Paul Gauge XPG 9.57 MJK 9.39.

[espsix]

We use either MJK or Ortmanns, I've found that the Ortmanns are a couple of tenths quicker over a approximately 6 second lap, but the MJK's are smoother, and don't go out of round like the Ortmanns do when the cars are not being used. ( not sitting on the rear tyres )

 

In 24th scale the BRM Group C wheels with MJK ( to suit ) rear tyres are unbeatable on any rubber tyre class car you can fit them on.

And they're stretchy, I've see a 24th tyre with a 12 mm hole go on a 17/18 mm rim many a time, and haven't heard of any splitting.

 

And you can always find a tyre to fit a rim.

 

Only ever had one set of Paul gage tyres, and they're were way to big for the rim they were supposed to fit, so never bought any more.

Edited May 10, 2017 by espsix

[shadow_rusty]

From Paul Gauge, his XPG's are 20 shore, and PPG's are 40 shore.

As MJK's are somewhere in the middle of those in terms of grip, I'd estimate that they are approximately 30 shore.

[jphanna]

John the MJK,s that I have here measure 40 shore A, do not know if that is the only harness they use.

 

the dealer for MJK in adelaide, i only saw him thurs night.....did i ask him what SHORE he supplies? of course not.......

 

i am under the assumption that whatever MJK classes we run, we all get the same type. i would be pissed if i got 40, and the guy next to me was running a special 'back door' batch of 25 or so!!!

[shadow_rusty]

I have received the WRP 'Brown' extra soft tyres in a pack off of the wall of tyres before, so it can happen.

Not normal, sure, but it can happen.

 

PS. I went back, but that was the only pack out of the batch of SCX Rally tyres that was the WRP 'Brown'... :(

Edited May 15, 2017 by shadow_rusty