G'day, I am now going to sort out some good tyres to use on the grass tracks and the question is do I go wide or narrow!
My logic is a wide tyre has more grip surface but spreads the vehicle's weight over a larger area also. A narrow tyre would have less grip surface but spread the weight over a smaller surface and therefore might dig in a bit better.
I am interested in acceleration grip and cornering grip, so anyone who can offer some experience with this Id like to hear what you have to say.
I have some old morris minor tyres here, 165r14 which I am considering using but before going to the effort of changing tyres around on the rims I thought it would be better to get some other opinions. Here is the tread pattern: http://i264.photobucket.com/albums/ii200/morrisman1/_MG_8198.jpg
A 165r14 is as large as I can go realistically underneath the wheel arches
joanie32,
Feb 5, 1:25am
In a nut shell, narrow compared to height. Too wide on grass givesa effect similar to aqua-planeing. experiencetalking here not science.
woki,
Feb 5, 1:28am
Narrow tyre , low tyre pressure.
morrisman1,
Feb 5, 1:55am
The morry tyres are 620mm in diameter, 165mm wide. Will these tyres fit on a modern steel rim! Im happy to put a tube in if necessary. The modern rim is a 14x5.5"
clark20,
Feb 5, 2:25am
The science is no matter how wide, the contact patch is the same size for the same pressure, its just wider instead of longer. I liked about 185s and a good pattern to dig, with good cross patterns. Not high performance tyres as they have plenty of channels to stop aquaplanning which does not help you.
mugenb20b,
Feb 5, 2:44am
For grass, you want narrow, but deep "tractor" type tyres. Which only leaves SAT tyres, but they don't come in 14 inch rims, let alone 165 width. In my opinion, your best solution is to get some 12 inch quad bike rims and tyres, and alter the stud pattern to suit.
mugenb20b,
Feb 5, 2:44am
For grass, you want narrow, but deep "tractor" type tyres. Which only leaves SAT tyres, but they don't come in 14 inch size, let alone 165 width. In my opinion, your best solution is to get some 12 inch quad bike (or those mini type 4WD Suzuki or Daihatsu Hijet ute things) rims and tyres, and alter the stud pattern to suit.
morrisman1,
Feb 5, 3:02am
Sorry should have mentioned, the rules basically say they need to be road tyres; we cannot have offset outer blocks, more than 8.5mm tread depth, more than 8mm between outside blocks and the tyres mustn'tfit into these categories: ??? tyres designed primarily for gravel surface rallying ??? tyres designed for mud surface rallying ??? tyres designed for off road use ??? tyres designed for snow surfaces, or ??? tyres designed for use on light or medium trucks.
mugenb20b,
Feb 5, 3:09am
Ah, OK, in that case, stick with what you've got, fit some inner tubes and run the pressures at 10 to 12 psi. But, the more tread depth, the better, and the more spacings bewteen the blocks helps. Wheel spinning at high rpm is a good thing (off road) as the centrifugal force will unclog the tread from any clay and mud and shit. Spitting out 'rooster tails' is awesome fun.
mugenb20b,
Feb 5, 3:09am
Ah, OK, in that case, stick with what you've got, fit some inner tubes and run the pressures at 10 to 12 psi. But, the more tread depth, the better, and the more spacings bewteen the blocks helps. Wheel spinning at high rpm is a good thing (off road) as the centrifugal force will unclog the tread from any clay and mud and shit. Spitting out 'rooster tails' is awesome fun. Oh, and if you are allowed, you could also weld the diff, but that will limit your steering,
morrisman1,
Feb 5, 3:30am
Sweet, Ill do some tyre swapping on tuesday when everything opens again. How do you think these will go on the gravel sprint too! Ill try to get some gravel tyres if I can (we are allowed those for the gravel sprint)
Do you think wheel spin would still be advantageous even on a surface which doesnt fill up the grooves, like green grass with a hard sandy base underneath!
mugenb20b,
Feb 5, 3:39am
Sorry morrisman, I'm not an expert when it comes to gravel roads. But, hopefully someone will show up and tell you what's best. I think pollymay would know a fair bit.
saki,
Feb 5, 1:15pm
Higher pressures, treat grass the same as a wet track.
moosie_21,
Feb 5, 4:02pm
When the German's first invaded Soviet Russia, they're Mark II, II's and IV's Panzers had narrow tracks which had a very tough time putting up with the rasputa (mud) and winter conditions of the Eastern Front. The Soviet T-34's outmaneuvered them for the first 2 years of war because of their much broader tracks. Go the Soviet way I'd say!
mugenb20b,
Feb 5, 4:08pm
I don't think the tracks were the problem. The Panzers were unreliable and thirsy, but more importantly, the Germans couldn't operate their tanks in freezing temperatures due to oil coagulation. The Russians used very low viscosity oils their transmissions and hydraulic systems. Besides Russian T series tanks were far superior than German Panzers in my opinion. The only advantage Panzers had then, was their speed, they were fast in their day.
tonyrockyhorror,
Feb 5, 4:10pm
That's a different scenario though. Low ground pressure on the T-34s due to the greater distribution of weight preventing them sinking so far - like a barge - Archimedes. Whereas the OP is talking about grip on a slippery but solid surface - the narrow tyre will cut through more easily to the solid ground just below the short grasses.
moosie_21,
Feb 5, 4:19pm
Hmmm, granted the Germans were far from their supply lines and couldn't start their tanks even when they lit fires under them during the first winter, but the muddy conditions of autumn proved that the wider tracks were better. What T-34's suffered from were poor gunsights and a lack of communication; German tanks could call in airstrikes ifthey couldn't pierce the much thicker armour of Russian tanks. The Russians also lacked tactical skill. Many lives were lost attacking over the same ground many times, trying to achieve a breakthrough where simple maneuverability and outflanking would have overcome obstacles.
But that's a bit off topic, I guess thinner wheels are better in this case!
msigg,
Feb 5, 4:34pm
Germans were running out of fuel. Simple answer is narrow.
pfemstn,
Feb 5, 10:33pm
you have to remember when competing on grass that it will be dirt and no grass after a couple of laps! wide tyres and low pressures work for me! and Yes 0 camberHa Ha
morrisman1,
Feb 6, 1:43am
After much stuffing around with the tyre levers I got the tyres on tonight. they feel better, I can swing the car around well at low speed with the handbrake because I have the traction to keep up momentum. The lush grass in the paddock is hard for anything to get traction on so not the ideal testing arena. I have a practice round this sunday at the track so will be a good chance to make comparison then
saki,
Feb 6, 1:48am
PF you have a thing about camber
matthew_129,
Feb 6, 2:05am
After playing around doing a few grass gymkhanas and autocrosses wide tyres are junk as are 'high performance' tyres. Go get a set of cheap ling longs or triangles and as narrow as you can get and theyll grab ok
saki,
6 days, 13 hours
the old firestone enduros used to be a favourite
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