CZ 400 tyres

[Ji Gantor]

What is the best tyre for VMX.
Grass in the morning, moist dirt just before lunch and bull dust with exposed tree roots in the afternoon.

These vastly changing conditions make our sport exceptionally difficult to set a bike up for. Does a rider have intermediates on in the morning and change to soft tyres come lunch, certainly no tyre manufacturer could design rubber to match the cow paddocks we race on.

Tyre pressure is equally important for both front and rear traction on the moving target that is our play ground. A rider may start out with 12 psi front and 10 psi rear in the morning and drop down 2 psi after lunch depending on rocks and roots.

Do riders even care, or are most VMXers more interested in the social gathering between races to bother finding a pressure gauge. This lack of concern about traction is fine for those that do not want to be up at the pointy end but it could be dangerous as the course becomes more like a skating rink as the day goes on. After all how many riders visited their local Orthopaedic surgeons last season.
 
I have seen broader rear tyres used that are so wide the knobs touch the chain in an attempt to transfer power from engine to dirt. I have also seen fellow riders turn up on race day with flat tyres and spend the first few hours changing out tubes with borrowed tools from other racers. This is all great stuff and leaves one with fire side stories that will make any bike rider laugh.

My question is directed to those that have won a major event, ridden for a factory race team and can tell the difference between one tyre and the next or the average racer that has tested heaps of different tyre brands on one bike on a cow paddock. All opinions are subjective but if some of you feel that one tyre is head and shoulders above all else I and others like me would love to hear your experiences.

What is the best tyre for VMX on a cow paddock?

[mike1948]

I've had good results with Bridgestone intermediates, seem to hold on quite well on baked hard surfaces, yet ok for the loamy berms.  I just lower the tyre pressure as the track chops up. Having said that, the tracks in north Qld tend to bake up and rarely get that deep moist consistancy requiring a mud tyre, even when wet.

[Ji Gantor]

Thanks Mike,
What tyre pressure do you run?
What model Bridgies do you use and on what bike?
What other tyres have you used to compare?

Ji

[mike1948]

I currently run:

front - 80/100 x 21   M601 (though I've been told this one is being superceded)

rear - 110/100 x 18   M22  - I previously used M602, but this is a softer compound

These are fitted to my Montesa 77model VB360.  I went with 601s & 602s 0n the previous - Montesa VR250 1974 & a Bultaco MK3 250 Pursang 1969.  I originally ran a Dunlop (model unknown) on the pursang, but it was a mudder, and moved around too much on the hard dirt.
I start each meeting with 14lb front & 12lb rear, then go from there. 
The montesas were basket cases when bought, and still had old rock hard pirellis, so I've no experience with other modern tyres, though I've been tempted to try a set of maxxis, they're popular with the modern guys, and look a bit old school.

I've been happy enough to not bother experimenting with other brands.

[Ji Gantor]

Have you any pictures of your bikes?

[eno]

I've raced mine for several seasons on Michelin S12 130/80 rear, cant remember front size but an S12 it is. I changed to a Mitas 130/80 at the end of last season, think I like it better than the Michelin. CZ's run the chain quite close to the edge of tyre so you gotta keep an eye on that, I've got about 3-4mm clearance & not much more on the other swingarm side. I've been known to take to the edge knobs with the grinder if it looks too close. You don't want any sideways wobble/warp on the rim either so it pays to roll the wheel thru one full rotation & check chain to tyre clearance.
Kiwi conditions may vary from Oz, but generally soft terrain tyre is best, if the conditions were hard to start with you can gaurantee it'll be getting real soft as the day progresses. Only time I've ever felt any need to go to hard type tyre has been on my own home track in Summer where it has hard base but soft powder on top.
Tyre pressure: about 12 PSI, I don't guage them but press firmly with my palm, looking for a hard tennis ball sort of feel, tending towards higher pressures these days, maybe drop if it's slop to ride on, or failing that park it up & watch the pigs wallow. 
Those S12's wear really well too, I got about 3 seasons out of it, I'd look at it & just couldn't justify changing it. I change the front when it washes out one too many times & I've busted a clutch lever - I hate that.

If you are a real CZ freak, Mitas bought out Barrum, so now you can still have the pedigree.

I'll also add that I'm less & less competitive as time goes by, guess it just doesn't matter anymore, aint never gonna be a champ nor want it.
It always amazes me when I see (usually a newbie) turn up with crap tyres & look in dispair as he smokes me around a corner, I must be under estimating the available traction but then I also hate falling off. Thats why I use good tyres.

[Ji Gantor]

Hi Eno,
That is all great stuff.
What is the bike that you are running these tyres on?
Our conditions are grass in morning then lose dirt or a fine silt dust in the afternoon.
Your conditions in NZ would be mud most of the time would I be right in saying that?
Are the Mitas better than the S12 in relationship to traction?

Thanks mate

[eno]

Mine is a type 981.4 380cc, it's 1.0mm O/S so more like 390cc but yeah a 400.
We have been having quite a dry run this year, it's all at the mercy of the weather gods.
The Mitas has a slightly more aggresive knob pattern, kind of looks like it would hurl more roost.  My kid was trained by riding in that roost he learned fast that it was best to get in front or get pummelled by it. 

Here's an action shot - if you trawl thru these pages you'll see a lot more pics of mine & others:



Look & weep:

[Ji Gantor]

Hi Eno,
Is that your bike No 18
Your tracks are beautiful.
Do you have some more images of your 1973 CZ400?

When your tracks chop up do they become dusty or is the dirt under the grass moist?

Thanks I am looking forward to riding in NZ soon.

[Ji Gantor]

Hi Eno,
So is that in the Taupo area.
Is that Mt Ruapehu or Tongariro. in the background?
We visit Turangi every year for the fly fishing and snow boarding at Mt Ruapehu.
My wife and I wish to retire in Turangi.
Paradice on earth...

[eno]

Hawkes Bay is the area.
Don't be fooled by the photogenics of the landscape, it cuts up just as bad as anywhere else on earth, especially when the big bore linkage boys are unleashed.
Depends if you had rain recently if so, moist underneath & no dust, if no rain oh yeah it's gonna be a dust up.
I'm # 18.

Here's a youtube link of one of our dusty rounds, Hawkes Bay at its worst, you'll see me baulk at the wall of dust:
http://uk.youtube.com/watch?v=_G1rL4ZP0nE
DJ Racing is the camera pilot.

I don't feel like spamming this thread with any more shots of my bike, check out the title "the 73's".

Most of our series is Manawatu & Wanganui based & generally one round in Taupo.

[Ji Gantor]

Hi Eno,
That Youtube film is great, very much like our tracks. Was the track grass when you started that day or is it a designated track?

The 73's has a fantastic bunch of images, Thanks.

Hawks Bay, how is the footy team going? 

[eno]

It was brown stubble grass that some hungry sheep were gnawing on to start with, it was an unusually dry summer that lead up this one.  Hawkes Bay is notorious for getting like that, they moved the event to spring time this year which is that picture of beauty you saw earlier.

Dunno how the teams going, I'm alergic to rugby. 

a still shot from the day:

[Ji Gantor]

Hi Eno,
Yep when NZ does not get rain it is just like the Western Island.

Nice shot of you plowing the earth.
Between the dry day and the green day did you feel traction differences?

[eno]

Dude you got it bad... Yeah a little more grip when there's some moisture bonding those little grains of dirt together. The green day was still fairly dry underneath.

Wanganui soil is largely clay based & is very stable when it comes to getting a beating from dirt bikes, like concrete if it's dry & turd when it's wet.
Hawkes bay is a lighter soil type but overall it's a nice medium to ride on.
Taupo is very volcanic based, light, sandy & will dust up easy but is extremely free draining & can stand shit loads of rain, well up to the day before, but if it pisses down on the day - slop like anywhere else.

Signing off now - I'm getting no work done here, nice talking to ya.