Front to rear tire width balance

[next69]

I read on the DSE website that the maximum tire sizes for a 69 are 245/45R17 on the front and 275/40R17 on the rear. I seen on Wayne Dues site that Mark Stielow put 275/40R17's on the front of the Mule and 335/35R17's on the rear, obviously Mark obtained these larger sizes by mini tubbing the rear and narrowing the front subframe. My question is I really like the look of the 335's on the rear, but can not afford a new front subframe, if you run the 335's on the rear and 245's on the front will this cause the vehicle grip to be disproportioned, also is there any way to modify the factory subframe to handle a wider tire.

[zbugger]

Yeah, you will notice a "push" in the turns. You want to keep the sizes balanced. Otherwise, there is a lot of tuning you'd have to do. You could run the sizes as stated, but stiffer rear springs and/or a large rear swaybar would be needed to tune in a balance. I think someone else can say more....

[next69]

I am curious, first of all is there any modifications that could be made to the stock subframe to achieve the 275/40R17 or at least larger than the 245/45R17 mentioned by DSE, and secondly is there a science to calculating this balance I see on the DSE configuration the front tire is 30mm narrower than the rear and 5mm taller, on the Mule the front tire is 60mm narrower but still 5mm taller.

[zbugger]

It's not 5mm taller. That number is the percentage that the sidewall is in relation to the width of the tire. I believe they are the same diameter. You may be able to get a 275 in front, but you'd have to notch the frame. I'm a second gen guy, but I know some first genners will jump in to help out soon.

[baz67]

The Mule used a WD subframe. You can get those tire widths with a WD sub. On DSE's Twister Kyle redesigned the whole spindle to get the 275 on his car. As far as I know he does not plan on marketing that mod. Other than that a stock subframe you are stuck with a 245. You could get a 255 without using the inner wheel tubs and some rubbing on the framerail at full lock.
Brian

[Ralph LoGrasso]

Like Brian said, you can go as big as 255, and have some minor rubbing. Some people have and do run 265s, on a stock subframe, and I think Vince is going to be notching his subframe to run a 275. I'll be running atleast a 265 on my full DSE suspended subframe, without a notch, and if I decide to notch, it'll be a 275. Two things though, the car won't be slammed, so the outside edge of the tire will sit flush with the fender lip, it won't be tucked at all (this is much easier to do on a 67/68 due to the fender shape). Also, I'm prepared to deal with rubbing at full lock, since I'll almost never see full lock on a road course. - For these sizes to work, you'll need to experiment with rim size and get creative with backspacing.

[next69]

Thanks for all the info. You say I can run up to a 255 on the front with minimal rubbing only at full lock as long as my backspacing and wheel selection are optimal, based on this front tire size what size rear tire should I use to achieve a good balance. I really like the 335's for the rear but if the car is not going to handle well due to the large tire size difference from front to rear then it is not a reasonable selection.

[Ralph LoGrasso]

Well, it's very highly opinionated, as well as a techincal question, in my experience (what I've read). Some people say you should keep 30mm max size difference between front and rear tires, so your rear tire in this situation would optimally be a 285. However, the 96-02 Vipers run 275/335 combos, that is a 60mm difference. The 03+ Vipers run 275/345 combos. That is a 70mm difference, which is what I'll most likely be running 265/335. HOWEVER, there is no doubt that the cars are designed like this due to weight distribution, and suspension design. I plan on extinsively tuning my suspension with the help of some very experienced individuals like Mean69 and Chicane67, who are very well versed in suspension and race techonology. My suspension is also highly adjustable. I can adjust spring rates very quickly with the 4 wheel coil overs, and will also be doing a custom front sway bar(after the car is on the road). The car will also be very light and the 3-link is VERY adjustable, and this will help to prevent the car from pushing.

edit: I'm not going to recommend a rear tire size simply because I know very little about suspension design, and I'm just going on what others have told me, and basically repeating what they said. Someone more experienced will hopefully chime in here.

[next69]

Does anyone have any experience with this, I am curious if you just need to notch the frame where it would obstruct the tire and then probably box it in with a little heavier metal to maintain structural integrity, or are there other things to consider?

[nkopper]

According to Stacy Tucker, a 245 front tire and a 315 rear are ideal for all-around performance and handling on a 1st gen Camaro. If you have any doubts about the efficacy of this tire combo, read up on Craig Boone's car. The 335 tire will not heat up enough on the track (too much surface area) and will actually decrease traction compared to a smaller tire.

I have spoken with Stacy about the Twister having 275's on the front. The mods required to do this are extensive and require new mounting points for the control arms, custom upper control arm, sectioned lower control arm, a custom spindle, and extensive inner fender mods (moved up and reshaped). The control arm and mounting point mods were to required to change the arc in which the tire moves when turned. The ball joints were moved outward and if I remember right, a little to the rear. They could not create a bolt-on package to do this, so with the stock subframe, you're stuck with 245's. She said the work to add a 275 to the front is not really worth all the work for anything less than an all-out race car.

[next69]

Thanks,

That is very valuable information, I like the look of the 335's but I really want to focus my money on function, now that I know how much time and money it will cost to get the extra tire, and the fact that I will not benefit from it on the street I can focus that time and money on front end geometry. Thanks again.

[next69]

I am curious would that be a 245/45R17 on the front or a 245/40R17? Does it make that big of a difference?