4wd front tyres on rear

[millzy]

I’ve heard talk of this, but don’t fully understand why and when its done

this BRCA national legal right? as the rules states that we have to run a mini spike or BB spike at national events but not the size of the tyre

[RogerM]

Do the national rules not give part numbers for applicable tires any more??? Not really looked at this years rule book yet

[millzy]

thats a good question I dont know. im sure some one like northy ...cue Mr G will know

I really would like to know why and when its done first.

[Northy]

Originally Posted by millzy

thats a good question I dont know. im sure some one like northy ...cue Mr G will know

I really would like to know why and when its done first.

No part numbers specified

G

[millzy]

See knew you was Da man for that Question Boss

now who can answer my main question

Greenwood knows somthing about this im sure

[Northy]

Cue captain understeer

G

[_sleigh_]

I never profess to be a mad science guy, but wouldn't the reduced contact area actually increase the force applied downward on each spike. As the weight would be distributed evenly across less spikes. Bit like ice racing with them skinny tyres. ?? more forward drive, but less side-bite ??

I seem to remember a Tiverton winter series with people trying Step-Pin 4WD "width" fronts on narrow rear wheels to get more drive.

Perhaps a mad science type guy can confirm my great theory, or better still shoot it to bits.

[DaveG28]

Generally the lower the grip levels the more worthwhile it may be, could be a wet weather option!?

Used a set of skinny rears in the wet when I used to do kart racing growing up, in the dry I'd be 4th or 5th usually, in the wet with those bad boys destroyed everyone every time (I was the only person with a set, they were a bit "unusual")! Till they banned them, bastards!!

In wet/snow it helps cut through the surface moisture by having more weight per contact area, but not sure how applicable it would be to any conditions rc runs in? Can't see it helping in grippy conditions as the extra rubber on the track helps as long as the track top surface is as grippy as the ground immediately underneath (unless you want to decrease rear grip?)

Would also decrease friction so reduce battery use and help acceleration (if not wheelspinning).

[millzy]

I remember on the b3 there was an option of a slim rear wheel or a wide rear wheel and you could fine tune the grip level you wanted- i got the impression at the Belgium GP that they ran 4wd fronts on the rear as the grip level was high

Have to say Sleigh; in all the years I ran at tivy winter I never tried the slim rear option. was this with a losi step pin 4wd front on the rear?

[warped]

Tried this on a fireblade evo with minispikes on grass a few years back.

Gave less forward traction but better side bite.

Main problem was that the car would roll over very easily if the car caught the slightest bump.

A small tyre will fit into ruts and hollows where a big wide tyre will roll over the top.

Also when a wide tyre reaches a certain camber angle it lifts most of the tread off the ground, loses traction and the car slides instead of rolling. With a narrow tyre - particularly one with a rounded profile such as a minispike the tyre can reach a much more extreme camber angle before it starts sliding.


Might be worth trying in the wet, if you have a layer of mud / standing water , as the tyre will cut through the surface better.

[janus_77]

Originally Posted by millzy

i got the impression at the Belgium GP that they ran 4wd fronts on the rear as the grip level was high

[discostu]

would a narrower rear tyre work on polished floor when we ran tc on polished floor the slim yellow pins were much better than the wide pins could this be the same for a buggy

[millzy]

Originally Posted by janus_77

yeah thats the pic ive seen, why was this done?

[bender]

Many years ago in Australia, when I used to race an old Fireblade, mounting front Cat rims with Losi stud tyres on the back was fairly common practise for me.

It certainly seemed to give the car more forward traction and sidebite on our standard bumpy low-grip dirt tracks. I did notice that it only seemed to work with mini-spike type tyres, as I tried the same thing with holeshot type tyres and it didn't work too well.

[super__dan]

Chris Long and I ran then in Belgium last year (as did others) but unknown to us Janus had done this before). Basically you get too much grip with full rear mini pins so it's either trim some rows off or (as we decided we preferred) run 4wd fronts on the back, cutting the inner rib off the wheels.

I liked the balance better, they gave slightly less drive (less as in not quite ultimate drive) which helped with steering on staggers. However when the track dusts up we both preferred the normal rears with outside or in and out row off.

I'd never consider it on minispikes.

[millzy]

Originally Posted by super__dan

Chris Long and I ran then in Belgium last year (as did others) but unknown to us Janus had done this before). Basically you get too much grip with full rear mini pins so it's either trim some rows off or (as we decided we preferred) run 4wd fronts on the back, cutting the inner rib off the wheels.

I liked the balance better, they gave slightly less drive (less as in not quite ultimate drive) which helped with steering on staggers. However when the track dusts up we both preferred the normal rears with outside or in and out row off.

I'd never consider it on minispikes.

can you tell me more on the inner rib off the wheels

[super__dan]

You know how on staggers on the front you cut the outer rib (where the bead usually sits on normal tyres) and glue to the edge of the middle 'rib'? We'' it's just eh same on the rears.

So leave the outer edge alone and trim the inside edge further into the wheel to account for the reduction in width.

[millzy]

Has any one got a pic of this . id like to see where you glue the inside of the tyre

[super__dan]

Here you go slick, Narrows on the left obviosuly.

Glue to the outer edge obviously, just need to make sure th tyre is pulled across and seated properly.

Why all the interest?

[Lars Alex]

For the Belgium GP its not allowed to cut off rows on the tire so it will be low profile. It takes about 1 sec off the laptimes with low profile. Then we are taking 2wd front tires in front on the 4wd, and front 4wd tires in rear on the 4wd. Its wery hard to glue!!!! Use strong tape to do it.
Im from denmark so hope Im understandable
Lars Alex - Yokomo B Max