I was just drawing up my extended weld in pins for roll centre correction and wanted to check fit so just as well might show you why you NEED Dallas uprights for larger roll centre correction. On stock uprights the ball joint pin sits in the upright at 10 deg angle. So if you just extend it, after some extension it will just hit the disc. This is with 32 mm extension and some 18 mm sphericals inside a 43 mm OD cup.... relatively tight..

 

Its not secret I'm heavily against large extensions on ball joints and tie rods.

First the taper that I see all the time, it doesn't help anything because the peak stress is still at the thinner shaft area where it meets the upright. To have the taper work, it needs a preload on its face which you cant really do on stock uprights.

Its also a big spring inline with the system to add softness in the response, especially the tie rod extensions people run. Steering sees over 500lbs of load in heavy steering moments. The ball joint regularly sees >1000 lbs load and moments upwards of 2000lbs.

In my very first control arms that people ran, I used normalized 4140 steel to machine them. Those come out to be about 29-30hrc hardness. Its a balance of hardness and brittleness and machinability and I wanted the ball joints to bend if there was an issue and not break. I did have a customer hit a wall and break a bunch of stuff including the wheels but uprights and control arms were reusable other than the ball joint. That part bent without breaking. But we did find the locking bolt could dent the shaft overtime.

The newer current versions are lightly hardened to 34-35hrc and zinc plated along with the 0, +5mm, and +10mm adjustment rings.

 

I need to get some street tires so I can get my car inspected. I was going to go with a 285/30 RE71R but then saw that Yokohama makes the A052 in a 295/30. The 295 has 0.9" more tread width but they were measured on a 10.5" vs. a 10". Anyone have firsthand experience between the two? Only real complaint I have with RE71R is heat tolerance and the resulting wear.

 

The 295 Yoks want an 11" wheel. I have them on a 10.5 and they're a touch stretched. The thing Yoks really dont tolerate is significant stretching or camber limited cars. If you're going on a 10" I would probably do a 265 A052 or 285 RE71. The Yoks will still be faster and the RE71s will last longer.

Both are competitive for XSA but the PAX is really tough in that class right now if you're battling other strong PAX drivers.

 

thanks for the tips.. The taper in the pic is for welding.. they will be welded onto the upright.

 

Ahh, yes.. If you weld it then that certainly changes things.

 

I've got 10.5" wide NT03s, would you buy the 295s for the 10.5 again or go back to the 285 RE71R?

 

Would still go 295s on the 10.5 but I wouldnt do them on a 10.

 

Sweet, thanks Dallas. Yokohamas are ordered. I also received a new SpoolinUp harness today to replace the one that's been giving me issues. Still need to check factory wiring when installing it but at least it's here. Parts are starting to stack up!

 

Whats the other harness set?

Did you have a Spoolinup COP setup and just need to replace the harness or did you make your own and fixing it?

 

Hm. Sounds like a fun time attack/HPDE tire.
Looking at TireRack, thread and section width listed for the 295 is crazy wide (and may not fit my car) but then the 275 only shows a 9.8" tread width. Doesn't help they are measured on different wheels, but still. Nothing in between.

 

A walbro 450 will do ~580-600whp with 1650 injectors and a Hobbs switch activated hi/lo voltage rewire. I ran this set up for track use a lot using an STM rewire kit but setting it up for the Hobbs switch, and never had issues.

The Hobbs switch is just a pressure switch, if you by a quality one it's not going to fail. Especially if you use it to switch the relay, which it will then never see any real load.

 

Dallas et al,

Am trying NOT TO pull/stretch rear quarters too much, to lave as close to OEM as reasonably possible.
Have RPF1 18x10.5 +38, and rear trailing arms to fit deep in rear.

So rear is the limiting factor.

What tire to run for best laptimes over 25 minutes sessions on track?

Hoosier makes a 255/35x18 that is uncommonly wide,

255 has 10.3 thread width
10.8" section width and 24.8" height

275/40x17 has 10.3" thread width
11" section width, 25.5" height

275/30x18 has 10.3" thread width
10.7" section width and 25.5" height

285/30x18 has 10.6" thread width
11.6" section width, and 24.9" height

295/30x18 has 10.7" thread width
11.6" section width, and 25.3" height

Yokohama 052

295/30x18 has 11.2" thread width
11.8" Section siwth, 25.1" height

Bridgestone RE71R

285/30x18 has 10.3" thread width,
11.4" section width and 24.8" height


Toyo RR

275/40x17 has 10.5" thread width
10.9" section width and 25.7" hieght

285/30x18 also has 10.6" thread width
11.3" section width height is shown as 24.8"

295/30x18 has 10.9" thread width
11.8" section width height 25"


Obviously wide(er) thread, narrower section width, making it fit under the rear quarters..
What to pick to go fast and last the session?


Thanks for your input.

 

Some notes:

Larger diameter = long thread patch
Larger diameter tire=more weight of the carcass
Shorter diameter tire= easier fit under fenders
Smaller diameter wheel= lighter wheel/tire package=less gyroscopic and inertia=more performance

Shorter sidewall= less heat build up and more response

Large diameter tire/wheel package are challenging to fit under rear quarters. Such as 275/35x18 & some 275/40x17 (25.5" ->25.7")

Also there is the play with 6" long springs, to fit strut spring-perch over the tire/wheel in front, to be able to lower the car easier, without resorting to big spacer.


Which do you think will give most performance for least fitment trouble?

 

I have had a homemade COP using his parts for years. I've also chased some bull**** intermittent spark issue for years. I've experienced everything from torqued spark plugs loosening up to a bent spring inside a coil losing contact. Replacing all COP springs seemed to have settled the issue for good then I blew a coolant hose and haven't been able to get rid of it. I couldn't put factory parts back on because in a genius move I did a mini-wire tuck a number of years ago and moved the passenger side plug to the driver's side. Speaking of which, do I have to undo that to meet the rulebook?

Aren't these 18x10?