The Official "RX8 in DSP" Thread
09-23-2013, 11:59 AM
#27
^^not too bad for aluminum sheet metal
started pulling the stereo components out last night, also removed the steering wheel/air bag assembly
a bit discouraging that everything from the factory is already near minimum weight :-/
started pulling the stereo components out last night, also removed the steering wheel/air bag assembly
a bit discouraging that everything from the factory is already near minimum weight :-/
09-23-2013, 01:05 PM
#31
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I'll let Mark answer the tire question as he can probably articulate it better than I. I will add however that I do believe there is a tire/wheel limit that is opitimal per car/chassis/power/torque and what seems to work really well is 255 on an 18x9 wheel and a 285 sized tire on a 18x10 wheel. Heat generation on the tire and outside temperature also plays a roll in this as well.
With the front splitter, I'll get more in-depth pictures soon but if you look at their FB page it has the whole build process and setup of it. It's non-adjustable however. Per the class rules we're limited with what we can do anyways.
With the front splitter, I'll get more in-depth pictures soon but if you look at their FB page it has the whole build process and setup of it. It's non-adjustable however. Per the class rules we're limited with what we can do anyways.
09-24-2013, 05:03 AM
#33
Autox is much more transitionally intense (or violent in some respects) than road racing. Despite the higher speeds and longer duration loads, for track things happen in much smoother and slower timing. That said, there's a point the weight and diameter starts to work against the chassis/engine so it can come down to available wheel and tire choices. I have a good set of 17x9 wheels that I'll try at least 245/40-17 (225/40-17 seems like a stretch) and I'm working on a set of 17x 10.5 wheels to also try the 275/35-17. Despite also having 18" wheels I prefer to focus on using 17" to start.
09-24-2013, 03:14 PM
#34
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Howdy,
How come? Do you want the slightly shorter diameter as opposed to the 285/30-18? Or more sidewall?
Mark
Autox is much more transitionally intense (or violent in some respects) than road racing. Despite the higher speeds and longer duration loads, for track things happen in much smoother and slower timing. That said, there's a point the weight and diameter starts to work against the chassis/engine so it can come down to available wheel and tire choices. I have a good set of 17x9 wheels that I'll try at least 245/40-17 (225/40-17 seems like a stretch) and I'm working on a set of 17x 10.5 wheels to also try the 275/35-17. Despite also having 18" wheels I prefer to focus on using 17" to start.
Mark
09-27-2013, 07:51 AM
#37
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09-27-2013, 08:12 AM
#38
There are a lot of factors involved, but were obviously good enough to win by a substantial margin regardless. Having the widest tires is no guarantee of anything, assuming they are actually wider where it counts or in actual use given the application parameters, like a sub-11" wheel on a 2600# car
09-27-2013, 02:21 PM
#39
Looking forward to seeing more RX-8's in DSP next year. After some further thought I'm confident the car will have a chance. Marc's car has shown great potential. It will take $$'s I don't have though to build my car further. If only the budget allowed I would be for sure.
Running the widest wheels possible that do not extend outside the body is a good start. If pursuing the 275 route, a 275/35-15 could potentially fit in the rear. It would eliminate the need for a final drive change and possibly allow the rear to work better by not screwing the roll center as much.
Running the widest wheels possible that do not extend outside the body is a good start. If pursuing the 275 route, a 275/35-15 could potentially fit in the rear. It would eliminate the need for a final drive change and possibly allow the rear to work better by not screwing the roll center as much.
09-27-2013, 05:05 PM
#40
An informative post by Team on wheel fitments:
https://www.rx8club.com/series-i-whe...9/#post4150593
A 10" wide wheel is the max width you can use that sticks close to the factory offset and takes advantage of all the inboard wheel space @ 50 - 52mm offset. With a fat tire (285 or 295) it will fill out the fender and also look mean as hell with all that rubber under there. You also aren't going to experience handling and driveability issues that result from wheel offsets lower than factory.
If you want to run wider than 10" then you have no choice but to start lowering the offset because there is no more inboard space available without extreme mods like tubbing and major suspension relocation/redesign. With every width increment above a 10" width @ +50-52mm offset you'd have to move the offset out by half that amount.
So for 1/2" increase above 10" width (10.5") half that amount is 1/4" = 6.3mm or 7mm for practical purposes. At each 1.5" increase you could subtract 1mm to account for the fractions adding up to a whole number, but there aren't too many RX8s using 11.5" wide wheels let alone 13" wide, lol. At anything past 10.5" wide using this basis the fender will need pulling or flaring for an equally wide tire not to rub because it will be sticking too far outboard of the factory fender lip to clear. So the resulting size/offsets would be:
10.0" @ +50 to +52mm
10.5" @ +43 to +45mm
11.0" @ +36 to +38mm
11.5" @ +30 to +32mm
12.0" @ +23 to +25mm
Otherwise running undersize tires to accomplish this fails on several accounts. To make the tire sidewall lean for fender clearance means that it has to lean both on the inside and the outside. A ridiculously narrow tire is required the further outboard the wheel lip sits outside the fender lip. Way back when tire sidewalls lacked good support but todays performance tires are designed such that a wheel wider than the tread width/contact patch width accomplishes no performance benefit. So a wide wheel with a high positive offset just to put a skiny tire on it is pointless and silly. Some wheel width/tire size reference points are:
9" wheel @ 245 to 255 tire
10" wheel @ 275/285 tire
11" wheel @ 305/315 tire
12" wheel @ 335 tire
Some change in offset from the original +50mm (S1 models) is not going to have much impact, but as you continue to push it out the resulting scrub radius moment arm is creating a force that makes the tires want to turn out, putting the steering components in constant tension while driving in a straight line. As such a setup encounters uneven pavement, bumps, water puddles etc. that moment arm is going to try and rip the steering wheel out of your hand position. Even moreso for these conditions under braking because this same scrub radius moment arm is going to magnify the braking deceleration forces against the steering wheel as well.
If you want to run wider than 10" then you have no choice but to start lowering the offset because there is no more inboard space available without extreme mods like tubbing and major suspension relocation/redesign. With every width increment above a 10" width @ +50-52mm offset you'd have to move the offset out by half that amount.
So for 1/2" increase above 10" width (10.5") half that amount is 1/4" = 6.3mm or 7mm for practical purposes. At each 1.5" increase you could subtract 1mm to account for the fractions adding up to a whole number, but there aren't too many RX8s using 11.5" wide wheels let alone 13" wide, lol. At anything past 10.5" wide using this basis the fender will need pulling or flaring for an equally wide tire not to rub because it will be sticking too far outboard of the factory fender lip to clear. So the resulting size/offsets would be:
10.0" @ +50 to +52mm
10.5" @ +43 to +45mm
11.0" @ +36 to +38mm
11.5" @ +30 to +32mm
12.0" @ +23 to +25mm
Otherwise running undersize tires to accomplish this fails on several accounts. To make the tire sidewall lean for fender clearance means that it has to lean both on the inside and the outside. A ridiculously narrow tire is required the further outboard the wheel lip sits outside the fender lip. Way back when tire sidewalls lacked good support but todays performance tires are designed such that a wheel wider than the tread width/contact patch width accomplishes no performance benefit. So a wide wheel with a high positive offset just to put a skiny tire on it is pointless and silly. Some wheel width/tire size reference points are:
9" wheel @ 245 to 255 tire
10" wheel @ 275/285 tire
11" wheel @ 305/315 tire
12" wheel @ 335 tire
Some change in offset from the original +50mm (S1 models) is not going to have much impact, but as you continue to push it out the resulting scrub radius moment arm is creating a force that makes the tires want to turn out, putting the steering components in constant tension while driving in a straight line. As such a setup encounters uneven pavement, bumps, water puddles etc. that moment arm is going to try and rip the steering wheel out of your hand position. Even moreso for these conditions under braking because this same scrub radius moment arm is going to magnify the braking deceleration forces against the steering wheel as well.
09-27-2013, 10:56 PM
#41
lol, i forget posting things like this ...
Wish I could find a set if 17x10.5 +45 SSR Type C or C-RS wheels @ 17.2# each. Supposedly they made at least one run production along the way, but I've yet to ever see a 2nd hand set up for sale ever ....
Wish I could find a set if 17x10.5 +45 SSR Type C or C-RS wheels @ 17.2# each. Supposedly they made at least one run production along the way, but I've yet to ever see a 2nd hand set up for sale ever ....
10-08-2013, 10:22 AM
#42
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A little late on the post, but I finally did a nice digest of my thoughts on the aero.. When I was dealing with a dying fuel pump! Check out the post and feel free to leave comments or post your thoughts on here.
RE-Zelse: Aero Testing @ Renegade
The overall verdict? Get it. With some minor alignment changes, I know that it will make the car pretty unstoppable. I was able to carry a lot more speed into various elements, flat foot slaloms for the most part, and get on the throttle a lot earlier. I had to brake earlier now however, because of the push it creates, but it's a very different type of push than say.. A car pushing because of alignment settings. You can feel the difference too.
Anyways, thats my two cents!
RE-Zelse: Aero Testing @ Renegade
The overall verdict? Get it. With some minor alignment changes, I know that it will make the car pretty unstoppable. I was able to carry a lot more speed into various elements, flat foot slaloms for the most part, and get on the throttle a lot earlier. I had to brake earlier now however, because of the push it creates, but it's a very different type of push than say.. A car pushing because of alignment settings. You can feel the difference too.
Anyways, thats my two cents!
10-10-2013, 01:52 PM
#44
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:P Your car will be whole again soon though. Take some pics of it in pieces! Tell us what you're working on! Stop being a shadowy figure in the dark and share some goodies. 
10-10-2013, 07:27 PM
#46
well I already have a number of items from STX prep, but the things done so far
audio system out
steering wheel & air bag out
AC system out
most emissions components out
radiator/fan/shroud assy out
interior torn apart
front bumper cover and undertray are off
next thing on the list is pulling the engine/trans, but have to help member WBTRotary! install his Daryl Drummond built engine starting this weekend before getting to this step
a bunch of stuff on order, don't really care to go into it all for now, but pretty much in keeping with my usual thought process & prep level
.
audio system out
steering wheel & air bag out
AC system out
most emissions components out
radiator/fan/shroud assy out
interior torn apart
front bumper cover and undertray are off
next thing on the list is pulling the engine/trans, but have to help member WBTRotary! install his Daryl Drummond built engine starting this weekend before getting to this step
a bunch of stuff on order, don't really care to go into it all for now, but pretty much in keeping with my usual thought process & prep level
.
Last edited by TeamRX8; 10-11-2013 at 03:47 AM.
10-18-2013, 06:05 PM
#48
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10-18-2013, 08:15 PM
#49
I have one planned, but it's my understanding that this is not as much of an issue as it is sometimes made out to be. There are a lot of different clutch suppliers out there, a wide array of materials, as well as the quality and expertise level of either. They're not all created equal, that's for sure. I suppose only time will tell though.
picked up a used S2 6 spd transmission today ...
picked up a used S2 6 spd transmission today ...
10-21-2013, 12:00 PM
#50
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Oooh decided to go with the S2 Tranny, hmmm? Doing the rear end as well or just the transmission? I've wondered what the car would be like with 4.44 but S2 tranny instead. Definitely would be a bit slower but able to stay in 2nd in the powerband no problem...