Wheel widths..why?

[c0sie]

Is there any specific reason that 4WD 1/10th offroad cars seem to run smaller width front wheels than the rears?

Thanks :)

[RogerM]

All a question of balance Chris.....

[c0sie]

Wasnt the most helpful of answers....anyone else?

An explanation would be ideal thanks!

[RogerM]

It was a perfectly acceptable answer .... it was tea time after all and between diner and a long winded answer diner was always going to win!!!

There is another way to view the question ... why would they be the same?

As I said it's all about balance of grip, my porker has different width wheels and tyres front and rear as it requires a different balance of grip front to rear to give the handling qualities desired by the designers.

Right I know that you come from a mirco background and that you've done 8th rallycross (worked out who I am yet mate???) and that both of those classes often use equal width wheels front to rear, but they also have different drive characteristics , namely fixed 4wd.

As most 1/10th off-raod cars run a one-way drive to the front they don't transfer braking force to the front wheels so all they have to do in a corner is steer until you get back on the throttle. That means that they are required to produce less grip and thus need less rubber.

The main reason though is exactly as my first response, a question of balance. Weight transfer fore-aft, side-side and diagonal also drive tyre configuration as well as the drive characteristics.
The weight distibution and weight transfer is very different between 10th and 8th off-road and again with touring cars.

When you consider than a lot of people are cutting extra rows of the front tyres as part of their standard set-ups is why whould they want them wider in the first place?
I have often seen people use 2wd fronts on their 4wd cars and looking back at my old Pred set-ups my old kiddy dry set-up was 2wd Ballistic Buggy pins fronts with 1 row off the outside edge or 4wd BB pins with 2 rows off the inside and 3 off the outside!!

Does that help more mate? We can get into chassis dynamics if you like but to do that to any great degree you'd have to let us know which car(s) your interested in.

[jimmy]

My smart car has skinny front tyres to stop me spinning out or rolling it I think :p


The only time I raced micro, I used a FTX blaze and Schumacher mini pins - The fronts were skinny and the rears wider- to give me a nice predictable steering. A nice 'balance' I guess you'd call it. I tried it with same width front and rear and it was too aggressive / twitchy

[c0sie]

Bloody hell! Its Roger Mills!!

Long time no speak! Hope your well mate :)

My question was primarily aimed at the 4WD micro that I run..my problem being this..
I use 1/10th touring car foams..that come as standard at 26mm wide. I currently true the width down to 22mm as I 'thought' that the smaller contact patch combined with the low castor I run would give me a small, but grippy contact area that would not require a huge force to turn ie the car would grip but be fast in its response.

I dont have a 'reliable' club to test on..with additives and ever changing track layouts..but wondered if running 26mm front and back on the 4WD car would offer more or less corner grip than 22mm wide foams, more or less chance of traction roll than 22mm wide foams and more or less 'tyre' slide/slip than 22mm foams?

Any advice on the above would be greatly recieved!

[losixxx]

if your questions aimed primarily at micro then perhaps you need to reword the question rather than say any specific reason that 4WD 1/10th offroad and put it in micro section!:D;)

[Northy]

There are really two types of grip generated by tyres though, if the spikes have something to dig into, then you would expect more spiles to give more grip.

What if there is nothing to dig into? Then the smae 'mass' on less spikes should give more grip. Rally cars (real ones) use skinny wheels/tyres on ice/snow don't they?

One of the things I don't like about my 1/8th is the fact that the front tyres are as wide as the rear, I'd like to use narrower fronts tbh.

G

[c0sie]

Northy thanks for the reply.

So, are you from the same train of thought as I that same mass onto smaller contact patch = more grip?

I forgot that 1/10th uses one-ways etc so yeah, the reason for 10th using thinner fronts probably wouldnt apply to my cause..but the info you lot are posting is useful nevertheless :)

[Northy]

I really think its a hard call that one tbh, its conplicated by the spikes actually digging in. In offroad on grass lets say, we cut spikes off the front to decrease the steering.

But would you do that on a flat floor like Worksop? There's nothing really to dig into there.

What about touring cars? I don't know about those. Does a narrower front tyre give more or less grip? Does a larger surface area give more grip than a smaller one with more mass on it?

I don't think this one is clear cut, like most things :(

G

[RogerM]

Chris,

now you've gone and complicated things!!!!

Foam tyres and rubber tyres (slicks) and then spiked tyres are completly different animals!!!

Foam tyres work essentially on frictional coefficients (lower shore and addatives increasing this coefficient) with the surface being run on. Now we get into talking about friction couples, slip angles, contact patch presentation yada yada yada. As most cars that run foams have very little roll induced camber change (is this the case with the Blaze being an off-roader .... can the camber links be set to acheive this?) the contact patch presentation is fairly consistent. In this case wider should = more grip.
If we are going to get technical the construction of the foams (how open celled the foam is) also has an effect as the edge of the "pockets" in the foams surface will increase available grip due to it providing more frictional couples.

Slicks (rubber) again are relliant on surface area and frictional coefficients, again softer rubber = higher friectional coefficients therefore it should equal = more grip.

Spiked tyres are slightly different though.

The rubber compound and contact area (combined area of all contacting spikes) is responsible for the grip level on hard pack surfaces ..... however if the spikes are soft and long they will fold over with lateral load and thus their characteristics will change (and they are likely to wear like crazy!).

The spike pattern is responsible for grip in softer conditions (ie. when there is little hard surface to contact) such as sandy soils, long grass / astro as they dig in / drag through. Here the stiffness of the spikes, due to compound AND construction will make a difference.

Hopefully that helps a little mate.

[Lee]

When your talking about narrow foams up front on a tourer it will reduce mid corner steering but make it very aggressive entering the corner and slightly more steering exiting. Back in the old M1 Striker days i ran foams cut down to 12mm wide up front and 24mm at the rear on tarmac to achieve a balance. They didnt last long @12mm:D

[Richard Lowe]

Back in the old M1 Striker days i ran foams cut down to 12mm wide up front
Were you running on snow or something?! :D

Thats very skinny :o