John V's STS GTUs build thread
01-07-10, 01:17 PM
#101
Initial plan was to run 15x7.5's and 225/45/15 shaved Hankook RS-3 in the dry with 225/45/15 Toyo R1Rs in the wet. Mostly because they are the shortest 225s that will be competitive.
New thought is 16x7.5s so I can run the toyo, hankook, dunlop, bridgestone, yoko or falken. Lots more options, just messes with my gearing a bit.
New thought is 16x7.5s so I can run the toyo, hankook, dunlop, bridgestone, yoko or falken. Lots more options, just messes with my gearing a bit.
The RS-3 is a really capable tire and right up there with yoko, dunlop, bridgestone, and kumho. I think it's definitely worth staying with smaller 15s.
the 225/45/15s are 8.2% faster than the 225/50/16s which is almost twice the benifit you get from your 4.3 final drive... (4.8% faster)
I think any tire brand benefit you get from a different tire won't be worth the extra gearing. Of course this is all assuming you won't run out of second gear...
EDIT: something to keep an eye on is falken is coming out with a new compound for the RT-615 (the RT-615K), I'm not sure if they're coming out with new sizes or not though.
also, the 15s will make your car lower without affecting suspension geometry which is always nice.
01-07-10, 02:53 PM
#102
Doubtful I will run out of second gear with the 15s. 8,000 RPM in 2nd with the 15s is almost 62MPH unless I've done my math incorrectly, and worst comes to worst I can overrev a couple hundred RPM.
But having six tire options is a big benefit. It's unlikely there are going to be new fast tires introduced in 15" sizes moving forward. If I'm paying to have custom wheels made (which is going to be the case whether I go with 15s or 16s) I may as well keep them for a while.
I still have some time to decide. One big thing to consider is the powerband of the motor. Two things. One, if the car is really struggling to get above 7500 RPM because of the stock ports, then a taller tire could be a benefit. Two, with the 15s, a pull out of a 30MPH corner is about 4,000 RPM. With the 16's, that same pull is 3600 RPM. That could be a big difference in available torque - the torque peak of the motor is probably around 4000 RPM.
Between the two, I'd rather lose power revving out at the top end and stay in the meat of the powerband more often.
Did I just make an argument for the 15's? Damnit.
But having six tire options is a big benefit. It's unlikely there are going to be new fast tires introduced in 15" sizes moving forward. If I'm paying to have custom wheels made (which is going to be the case whether I go with 15s or 16s) I may as well keep them for a while.
I still have some time to decide. One big thing to consider is the powerband of the motor. Two things. One, if the car is really struggling to get above 7500 RPM because of the stock ports, then a taller tire could be a benefit. Two, with the 15s, a pull out of a 30MPH corner is about 4,000 RPM. With the 16's, that same pull is 3600 RPM. That could be a big difference in available torque - the torque peak of the motor is probably around 4000 RPM.
Between the two, I'd rather lose power revving out at the top end and stay in the meat of the powerband more often.
Did I just make an argument for the 15's? Damnit.
01-07-10, 03:16 PM
#103
Doubtful I will run out of second gear with the 15s. 8,000 RPM in 2nd with the 15s is almost 64MPH unless I've done my math incorrectly.
But having six tire options is a big benefit. It's unlikely there are going to be new fast tires introduced in 15" sizes moving forward. If I'm paying to have custom wheels made (which is going to be the case whether I go with 15s or 16s) I may as well keep them for a while.
I still have some time to decide.
But having six tire options is a big benefit. It's unlikely there are going to be new fast tires introduced in 15" sizes moving forward. If I'm paying to have custom wheels made (which is going to be the case whether I go with 15s or 16s) I may as well keep them for a while.
I still have some time to decide.
and now with MR-Ss and NB miatas in STR I wouldn't be surprised if more 15" sizes start popping up.
RS-3 reviews: http://sccaforums.com/forums/thread/366738.aspx
01-07-10, 04:17 PM
#104
There's more to it than that. Yes, some of the guys like the RS-3. It also hasn't won anything yet. They also don't have an autocross contingency program anymore. Nobody has tried the tire on a heavy car yet as far as I know, and the FC is very heavy for the width of tire that is legal to run.
Bridgestone and Toyo have great contingency programs. That alone is almost enough to make me want to run them. But the Toyo is too soft for the RX-7, so that one is out.
Bridgestone and Toyo have great contingency programs. That alone is almost enough to make me want to run them. But the Toyo is too soft for the RX-7, so that one is out.
01-07-10, 06:45 PM
#105
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I agree with sticking to the smaller wheels. i hate getting caught in the bottom end of second out of a slow corner.
better to be falling off of the back side of the powerband than not reaching it. the fall off after peak is going to be a lesser slope than the torque curve leading to it.
better to be falling off of the back side of the powerband than not reaching it. the fall off after peak is going to be a lesser slope than the torque curve leading to it.
01-08-10, 02:19 PM
#108
Either I go with Bridgestones or I suck it up, pay for tires, and go with the Hankooks. The issue with THAT is that the Hankooks are not good rain tires, so I'll have to have something (Toyos?) for rain events. Which screws up contingency if it rains.
I am so used to racing on Hoosiers and winning tires that I will really miss not having that. But I guess to win tires you first have to win... decisions decisions...
I am so used to racing on Hoosiers and winning tires that I will really miss not having that. But I guess to win tires you first have to win... decisions decisions...
01-08-10, 05:16 PM
#109
well I'm about to buy a set of 225/50/16 star specs for my summer tires, you can borrow them at an auto-x if you want (they'll be on stock wheels) you can compare them to a set of 225/45/15s if you can find one 
I'll be taking them off to switch on r-comps anyway.
I'll be taking them off to switch on r-comps anyway.
01-08-10, 07:45 PM
#110
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I agree with your reasoning on the 15s, but from what I've seen the 16s, especially the Bridgestones, tend to run a bit wider than their size suggests.
For example: Tire Rack says the section width for the RS3 in the 225/45/15 is 8". The RE11 in the 225/50/16 has a much more manly 8.3" section width. That may not be a huge difference, but on a heavy car I'd want all the rubber on the ground that I could get. To further back this up, my old RE01s in 225/50/16 looked like they were stuffed on 8" rims when I ran them. While the gearing advantage of the 15s would help alot on a smaller local course, I don't feel that the taller tire has hurt me in my limited national experience.
For example: Tire Rack says the section width for the RS3 in the 225/45/15 is 8". The RE11 in the 225/50/16 has a much more manly 8.3" section width. That may not be a huge difference, but on a heavy car I'd want all the rubber on the ground that I could get. To further back this up, my old RE01s in 225/50/16 looked like they were stuffed on 8" rims when I ran them. While the gearing advantage of the 15s would help alot on a smaller local course, I don't feel that the taller tire has hurt me in my limited national experience.
01-12-10, 07:48 AM
#111
Well this is turning into a major cluster. I cannot find any 15x7.5 or 16x7.5 wheels in remotely close to the right fitment. Do I really have to spend $2200 on custom wheels to compete in STS? Not sure why the wheel width was chosen as being 7.5" maximum. 8" would have allowed some of the heavier cars a bit of extra competitiveness. The CRX and Miata guys can't fit an 8 under the rules anyway. /rant
Main problem I'm struggling with right now is Ground Control's rear shock mounts. They incorporated a spherical bearing into the lower shock mount. No issue there. The problem is the I.D. of the eyelet on the Konis they used is too small, so the spherical bearing has only a 12mm I.D.. The boss on the trailing arm is like .. 16-17mm. So clearly that doesn't work so hot. We're trying to find a solution but I really don't know what they were thinking when they sent this out.
The front suspension is all together. I'll try to snag some pictures tonight. Freshened calipers, SS brake lines, new wheel bearings, new tie rod ends, poly bushings in the control arms... it's all gradually coming together.
Main problem I'm struggling with right now is Ground Control's rear shock mounts. They incorporated a spherical bearing into the lower shock mount. No issue there. The problem is the I.D. of the eyelet on the Konis they used is too small, so the spherical bearing has only a 12mm I.D.. The boss on the trailing arm is like .. 16-17mm. So clearly that doesn't work so hot. We're trying to find a solution but I really don't know what they were thinking when they sent this out.
The front suspension is all together. I'll try to snag some pictures tonight. Freshened calipers, SS brake lines, new wheel bearings, new tie rod ends, poly bushings in the control arms... it's all gradually coming together.
01-12-10, 09:33 PM
#116
A lot of the 17X8 mustang wheels are around 20 lbs, and I know most of the 16s were lighter.
I'm sure you can find some on craigslist locally and check them out. They are dirt cheap.
01-13-10, 09:59 AM
#119
I'm also not really terribly suprised by the GC coilovers not fitting. I don't think they actually make full coilovers for the FC so you probably get a set that they just threw together with some measurements they had taken.
01-13-10, 10:01 AM
#120
They do make full coilovers for the FC. I don't understand why they sent rear shocks with a 1/2" ID spherical bearing when the factory shock mounting boss is 20mm. Doesn't make sense.
They're sending me new rear shocks that will work with the stock mounts so it's all good, but I'm slightly annoyed that I didn't get to put the car back on its wheels this weekend.
They're sending me new rear shocks that will work with the stock mounts so it's all good, but I'm slightly annoyed that I didn't get to put the car back on its wheels this weekend.
01-13-10, 10:06 AM
#121
They do make full coilovers for the FC. I don't understand why they sent rear shocks with a 1/2" ID spherical bearing when the factory shock mounting boss is 20mm. Doesn't make sense.
They're sending me new rear shocks that will work with the stock mounts so it's all good, but I'm slightly annoyed that I didn't get to put the car back on its wheels this weekend.
They're sending me new rear shocks that will work with the stock mounts so it's all good, but I'm slightly annoyed that I didn't get to put the car back on its wheels this weekend.
