Wheel diameter question

hey all a quick question on wheel sizes, im new to c class and ive noticed a lot of the rwd cars in this weeks ghost league are running large diameter fronts and stock rears.

is it a new forza fashion? or is there a genuine reason? i race b class and a class and have played all forzas and never seen this before

It reduces the PI of the car by quite a bit on some cars, so you can add an extra engine part or upgrade the tire width slightly, it does weigh the car down a bit but you get an extra upgrade so its worth it. That’s if you’re talking about the RIM size and not the Tyre Width

I notice it when downloading tunes for lower class cars mainly.

Altering the rim size may also make those tyres more responsive, but I haven’t tested this myself as I usually leave rim sizes stock.

As both posters above have mentioned, Large rimsize decreases PI of the car cause of weoght increase, And in some cases it is preferrable.

Also low profile tires alter the responsiveness, or should I say it laters the behavior of grip.
Generally low profile tire is more sharper on it’s response, but it might have “snappy” grip, which means that when you lose the grip, it’s very sudden and countering it is hard.
While on hhigh profile tires the response is slow,but when you lose grip, it happens slowly and is easy to contorol.

Therefore low profile front tires and high prfile rear tires mean sharper steering response, and low chance for understeer. and smooth, easy to control oversteer.


A good explanation.

In the lower classes where handling upgrades are limited, having a more responsive front tyre could make up for the fact that you don’t have upgraded Springs, Tyres or Roll-Bars, while also leaving enough PI for some power upgrades. If upping the rim size provides that responsiveness, then it’s a handy shortcut.

thanks for the explanation i changed mine on my 65 stang to 17s and it turns in better…i thought it was a fashion craze like the stance craze lol i used even diameter tho i like my cars to look good to, these cars with large front and small rears look horrible!

Paint them black so that it’s harder to notice :wink:

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Just last night I was trying to see if Holden Monaro (D314?) could be made into a E300. Could not do it without increasing the rim size. Makes the car look unsightly but it’s been degraded E class.

So no, it’s not for looks; it’s mostly to gain few extra PIs in lower class cars.

I upgrade size for the reasons explained above as well, with primary support of (1) stay with PI limits, (2) turn-in response, and, (3) if I need additional features I would sacrifice by increasing the rim size since it will open up some PI for me.

p.s. I have several cars in the lower classes with maxed front & rear.

Personally I try to aim for tire profile 40-45 when bulding a car. I have found that there is the “sweet spot” Grip loss isn’t snappy but it gives rather good response, although if I have really wide tires on back, and skinny up front, I might go outside that profile gap, mainly lower profile at the back. This happens mainly on muscle cars, due very wide tires, and the tire width counters the snappy behavior of low profile of the tires.
On FWD I might go for lower profile, Same with low PI builds as I often can add something else to the car, (Cars like E class Mazda Cosmo and so on)

I build my drag cars that way. Usually leave my rear tire stock diameter and make my fronts a couple sizes bigger. Some for looks and also to keep the tire itself smaller. Not really sure the actual performance effect on drag, if any. But I’m sure you’re talking circuit.

On drag I could think large diameter front tires being waste, unless you can get some other part with lower PI.
As how I think you want to have car that has seasonably light front end, and therefore small rims, but on rear you might want to have bit more weight and possibly got that reason larger tires.
Then again I have built only 1 drag car ever, and that was in FM4 so I might be wrong…

Having spent my youth around the dragstrip, I can shed some thoughts on what’s “the norm” as far as usual tyre set ups go.

You run a taller ( larger diameter) front tyre rime set up that’s stock or thinner.

Reason being, the lights need a broader access to the start of the tyre wall before the pre-stage light illuminates, you roll " slightly" forward so it then engages the “staged” light. Having a broader tyre wall allows the car to roll ever so much before the light hits the rim, thus giving a foul light.

So fronts need to be tall tyre walls, narrow rim/wheel widths. Second reason for this is less friction and very quick steering response to keep car in one direction - dead straight. Tyre pressure needs to be 30+ psi.

Rear rim width needs to be as wide as available, and be as tall in diameter as possible as an upgrade allows. The Rim diameter however, needs to be as standard as possible, as drag slicks rely on tyre growth to increase top end gear ratio changes.

The tyre pressure should be low, lower than 20psi. This allows the slick to grow rapidly, increasing the tyres diameter and at the same time, giving maximum grip by the extreme width it has. The slick needs to grab the Tarmac as fast as possible, and have the largest footprint of adhesion at top revs, both off the line, and in each gear as possible

Google some funny car or pro car drag pre staging but outs or blips. You’ll see the rear tyres grow dramatically, and you’ll also notice that the tyre walls are crimmpled due to lowest tyre pressure possible. In fact, many heavy hitters have their tyres bolted to the rims due to extremely low tyre pressures at idyl etc. mainly the “big boys” do that however.

The main idea is to stage correctly, have some wiggle room when staged incase the car rolls slightly, which can happen if the clutch is pre-engaged properly and ready to unleash the rear tyres which should grab as fast as possible, and grow taller straight off the line.

Sadly, in Forza, when you upgrade to drag slicks, both front and rear tyres are given the same compound type.

When in fact, the rear tyres should be the only tyres that gain the slick compound, or, fronts only in FWD, and naturally, all 4 in 4WD. Get low in a view perspective of your car when you’re upgrading and watch the front tyres widen when you select drag slicks. Ideally, they should stay standard.

Many cars we raced back-in-the-day with slicks, had as little as 15psi, but that grew to 30psi once they were hot due to burnouts and pre stage set up.

The only reason you’d have standard tyre/rim widths on rear (in RWD) is to simply do massive burn outs… While these are entertaining, they certainly do not get you faster trap times or higher trap speeds.

Check out some of my Gallery Pics of my Nova, '53Vette, 510 Datsun drag versions… (Feel free to ‘like’ if moved to do so) and you’ll notice huge tyre rim differences and ‘attitude’ that earlier drag cars took. Many pre-raised the front of the car so as to shift weight directly to rear wheel asap while keeping the front ‘skinnier’ pointed straight ahead with as little friction as possible.

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Well, some of how I tune/build has some aesthetic reasons behind it. Sadly, we don’t have proper drag tire and wheel combinations in the game. Rear rims are like 14-15" diameter, at least when I have looked at drag tire sizes online. Fronts are stock size or so, but very narrow if possible, like 4.5" and not a very tall sidewall. Rear tire isnt right either, even at the biggest the Forza rear drag tire diameter is around 28.5 -29"ish, regardless of width. That barely makes it a “small tire”. Most should be 29.5-33".

So, like I said, when I build a drag car, I use the stock rear rim, then if the front is a stock 14", i will usually go to a 16", maybe a 17". Whatever looks right on the car. I dont know if there is any benefit from drive tire flex on launch in forza, but would think the more meat on the sidewall, the more flex and grip. But it’s forza so I am sure it’s mostly all about tire pressure.

As far as the weight, I use the really light racing rims that are as close to drag rims as Forza gets, so any added weight of the 2-3" of rim diameter is minor.

This looks best on cars with really narrow stock rim size, like the Bel Air and '40 Ford, about 17" front with stock width and a 345 rear width stock diameter. That looks nice and Hotrod/drag-ish to me. It’s my humble opinion and I don’t really know how much it matters for drag racing.

I will add that when I tune circuit cars I will also increase diameter, but only by a little. Again, more for looks. I dont like that barely any rubber DUB look. Usually on a muscle car I won’t go bigger than 18". The small increase makes it feel a little more responsive in the turns, but doesn’t make bumps and curbs harsh. So I suppose for circuit there’s a nice benefit, but I’m sure extremes will get ya in trouble.

I mostly just babble, sorry. Haha

If you want to test the difference, i have a bunch of drag tunes shared. Compare and contrast.

Even as I was reading that, I can’t help wishing that drag racing was proper in this game! I didn’t know about the reason behind the front rim size. With the back, I have been looking at rim diameter and the largest I have found is I think a 28.7" tire which if I’m not wrong doesn’t even make it a “small tire” which I think is 29.5" tall with the bigger tires being 33" plus. Oh well, maybe someday it’ll all be in the game, for now at least we have what we have, lol.

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I have achieved some great launching cars that keep their max revs, with just a few hundred revs drop at gear changes, the '69 Nova as one example, plus the '53 Vette as a close follow up.

Keeping the original rim size, choosing the widest rear tyre, and then selecting slicks, lifting the front suspension to high, and dropping rear to almost lowest setting.

Then, selecting the stiffest springs on rear, softest on front but strongest rebound on front, so shocks stay extended and weight stats transferred to rear.

Dropping tyre pressure to 15psi, keeping stock wheels and tyres on front, allowed for maximum adhesion of rear slicks, kept weight on rear, stopped front from dropping dos, and revs keeping engine loaded on rear wheels.

Give it a try…

Check my psi jobs out in my Gallery, see if you like…

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