ACR steve
Enthusiast
Just curious if any of you ACR curous guys are using 315's Hoosier's on the front and how the car reacts to the wider rubber up front?
Thanks
Thanks
ACR guys have you used 315's on the front?
- Thread starter ACR steve
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This past NARRA event at Hastings I started out on Saturday with Hoosier R6 scrubs, 345/30-19 on the rear and 295/30-18 on the front. The car seemed very well balanced judging by my limited experience. No drama. On Sunday I switched over to fresh Hoosier R6's, 335/30-18 rear and 315/30-18 front. Definitely noticed extra front end grip. Could have been due to the fact that they were new though. The rear end came around on me twice. Both left hand turns. I was nearly 1 second faster with the 18's all around though. Kept hot tire pressures the same all weekend. Only change I made was I added a notch of rear wing after the two oversteers. Thought about tire pressure but decided to play with the wing first. Had no problems after that.
Experts feel free to chime in.
Experts feel free to chime in.
David Pintaric
Viper Owner
Viperless: the 345s are about 4% taller than the 335s, so your effective gear ratio is changed. Whe I ran T1, at every track not called Road America, the shorter tire was preferred. In STO, because I can use any rear gear, I use the taller and wider 345-35.
My tire combination is 315 front and 345 rear. I have toyed with the idea of throwing 335s on the front, but haven't got around to buying new wheels.
In T1 I used 315/335s mostly, and the car always pushed for me. Now, with the ability to change so much more (springs, sway bars etc), the car is VERY neutral. In fact we had the opposite problem at last year's Run Offs in that the car was loose as hell and scared the crap out of me. Now it's pretty much perfect, which bodes well for me in 2 1/2 weeks.
My tire combination is 315 front and 345 rear. I have toyed with the idea of throwing 335s on the front, but haven't got around to buying new wheels.
In T1 I used 315/335s mostly, and the car always pushed for me. Now, with the ability to change so much more (springs, sway bars etc), the car is VERY neutral. In fact we had the opposite problem at last year's Run Offs in that the car was loose as hell and scared the crap out of me. Now it's pretty much perfect, which bodes well for me in 2 1/2 weeks.
SoCal Rebell
Enthusiast
I know Dan (ViperX) uses 315 up front and loves them, when I get my next Gen IV ACR I am definitely going to mount 18 x 12 rims with 315s on front. In my 10+ years of tracking Vipers the one thing I've always known is Vipers want to "push", give me as much front grip as possible.
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I've run through about 8K track miles worth of 315 R6's up front (on 18 x 11" rims) and love them. I have also run 335 x 30 x 18 at the rear and 345 x 35 x 18 at the rear. The 335's seem to work well on the "shorter" tracks as they give you a bit of gear ratio help. The down side is that they are not very forgiving near the limit.
A couple of our local guys have tried 335's up front but they will rub on the fenders at smooth track ride height and on bumpy tracks - just not worth the trouble IMHO.
After some testing, I prefer the 345 x 35 x 18 at the rear (on 18 x 13" rims) overall as they offer more grip and are a bit more forgiving in high speed corners, so that's what I've settled on.
If you go to the R6's, 315 F / 345 R x 18 set up, you will want to increase spring rates front and rear and increase front negative camber to about -2.5 or more, depending on the track.
FYI, the "smooth" track ride height is plenty low, IMHO, if you run multiple tracks and don't wish to mess with your set up at each track.
You can get the Gen IV ACR's to be very neutral handling and achieve excellent tire wear with a bit of testing and tuning.
Good luck,
Dan
A couple of our local guys have tried 335's up front but they will rub on the fenders at smooth track ride height and on bumpy tracks - just not worth the trouble IMHO.
After some testing, I prefer the 345 x 35 x 18 at the rear (on 18 x 13" rims) overall as they offer more grip and are a bit more forgiving in high speed corners, so that's what I've settled on.
If you go to the R6's, 315 F / 345 R x 18 set up, you will want to increase spring rates front and rear and increase front negative camber to about -2.5 or more, depending on the track.
FYI, the "smooth" track ride height is plenty low, IMHO, if you run multiple tracks and don't wish to mess with your set up at each track.
You can get the Gen IV ACR's to be very neutral handling and achieve excellent tire wear with a bit of testing and tuning.
Good luck,
Dan
kdaviper
Enthusiast
I don't see how 20 mm of extra width would do much at all to improve traction without also switching to a softer compound. Even with the extra width, your contact patch would be the same area with the same tire
pressure, albeit more rectangular. I guess you could possibly see an improvement in thermal performance tread life and maybe the wider tire deforms less in the corners too. The wider/taller tire would also have more
rotating mass further from the axis of rotation, which theoretically would reduce your straight line acceleration a bit. As with many things though, I'd imagine it comes down to exactly what you need your tires for and what you're willing to sacrifice in order to gain what you need.
pressure, albeit more rectangular. I guess you could possibly see an improvement in thermal performance tread life and maybe the wider tire deforms less in the corners too. The wider/taller tire would also have more
rotating mass further from the axis of rotation, which theoretically would reduce your straight line acceleration a bit. As with many things though, I'd imagine it comes down to exactly what you need your tires for and what you're willing to sacrifice in order to gain what you need.
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ACR Steve,
Compared with the OE size 295 x 30 x 18 front R6 on 10 inch rims;
Tread with of the R6 315 x 30 x 18 is 1 inch greater which gives you a larger footprint and does equal more traction, especially at the limit.
Section width is .9 inch greater which is a bit more forgiving at the limit.
Height is .3 inch taller, which still allows you go get the car to the "smooth track setting and give you a bit larger footprint.
Weight is 3 lbs heavier, slightly heavier tire, more "rotational" mass but also helps with durability of the tires.
Normal rim width is 1 inch wider, which gives you a wider front track and helps with stability.
If you know any of the ACR-X racers, ask any of them about the smallish front tires that have to run per their spec series rules. They will all tell you they'd love to have more front tire.
Vipers are large, powerful, heavy cars that need a bunch of tire to stop and turn up front and get the power down at the rear.
Simply put, all else being equal, you will be able to stop and turn better with a bit more front tire and you'll be able to get to the gas sooner and harder, which is what we live for!
Dan
Compared with the OE size 295 x 30 x 18 front R6 on 10 inch rims;
Tread with of the R6 315 x 30 x 18 is 1 inch greater which gives you a larger footprint and does equal more traction, especially at the limit.
Section width is .9 inch greater which is a bit more forgiving at the limit.
Height is .3 inch taller, which still allows you go get the car to the "smooth track setting and give you a bit larger footprint.
Weight is 3 lbs heavier, slightly heavier tire, more "rotational" mass but also helps with durability of the tires.
Normal rim width is 1 inch wider, which gives you a wider front track and helps with stability.
If you know any of the ACR-X racers, ask any of them about the smallish front tires that have to run per their spec series rules. They will all tell you they'd love to have more front tire.
Vipers are large, powerful, heavy cars that need a bunch of tire to stop and turn up front and get the power down at the rear.
Simply put, all else being equal, you will be able to stop and turn better with a bit more front tire and you'll be able to get to the gas sooner and harder, which is what we live for!
Dan
What He Said.......... you will sandblast the fenders and sills a bit more, but understeer ***** worse....
i would just be happy to go as fast as those x-driversI'm running 315/30-18 Kumho XS in the front for the street and days when I feel lazy (don't want to hassle changing tires) at the track. No rub and pretty well balanced but car still pushes a bit at 10/10th. Here's a picture:
I also run 335/30-18 Hoosier A6's once in a while, and boy even though the wheel (not tire) rubs against the sway bar at lock, the 335's at the front totally transforms the car and I think I can pick up an easy 1 second on an average autox run over the Kumho XS or V700 at 315 or 305. I don't find the rubbing issue bothersome as I only use the 335 for the track and since one never have to enter full lock while on track, I only need to be concern with making u turns while on the way to the track.
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I also run 335/30-18 Hoosier A6's once in a while, and boy even though the wheel (not tire) rubs against the sway bar at lock, the 335's at the front totally transforms the car and I think I can pick up an easy 1 second on an average autox run over the Kumho XS or V700 at 315 or 305. I don't find the rubbing issue bothersome as I only use the 335 for the track and since one never have to enter full lock while on track, I only need to be concern with making u turns while on the way to the track.
im thinkin a wide tire in front may be overkill and could possibly hurt the effect, a happy meadium like a 295 will do the trick- there is no miracle tire out there to get you along... too much tire can acually hurt you in the front, it can get in its own way so to speak, if some of you are pushing in the front, maybe try to lower the ass end a smidge to loosen the car up and kill some of the push
SoCal Rebell
Enthusiast
You are wrong, wrong, wrong. I will repeat myself, "you can never have too much front tire on a Viper" on the race track! At the Open Track Challenge "7 tracks in 7 days" we were required to run street tires at 220+ treadwear rating and putting 335s on the front gave our Gen II the fastest times.....period!
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Care to explain how a tire can get in it's own way???
Was it after 5:00 PM where you are when you wrote this? i.e. What were you drinking?
How would a wider front tire, all else being the same equal more front "push"?
shooter_t1
Has Left the Room!
Absolutely wrong as has already been said.. Stick to the alley...oh wait, your banned there.
1HOTV10
Enthusiast
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Glenn,
Hope you can make it out again this year as our Fall track season kicks off in October at Willow Springs.
It was fun watching you improve and enjoy yourself.
Steph did really well too.
Dan
Hope you can make it out again this year as our Fall track season kicks off in October at Willow Springs.
It was fun watching you improve and enjoy yourself.
Steph did really well too.
Dan
