[Home | Mail Archive | Join the mail archive | Photo Gallery ]

Mazda Rotary Pickup Forum
you are logged in as
profile | register | faq | search (active threads) | memberlist
Sponsored by:
Index > @ the Pickup Bed (General Topics) > Thread: My first REPU autocross
Thread: My first REPU autocross [' This thread is 2 pages long: (1) 2 ']
Tom93R1


Redlining
Posts: 458
posted January 16, 2005 06:41 PM

My first REPU autocross

Autocrossing the REPU is lots of fun! I think I enjoyed it more than I ever did in the FD. Driving was alot better because I actually fit with a helmet, and for some reason REPU racing just seemed funny to me and I laughed practically the entire time through each run.

Anybody ever have success in reducing the wheel spin on the inside rear wheel? I was trying to figure out if lowering, another set of wheels/tires, or anything else would significantly help and be worth the effort.

        Click here to send Tom93R1 an ICQ message. Click here to add 16640317 to your ICQ list. Click here to visit Tom93R1's homepage. Click here to send Tom93R1 an AIM message. 
View IP (Administrators only)
Tom93R1


Redlining
Posts: 458
posted January 18, 2005 10:07 AM

Got a few pictures from the autocross. Wish the guy I had taking pictures when I was out used the zoom a bit more.

http://bud.homeunix.net:8080/imgs/SOLO2_Jan05/index.htm
____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

        Click here to send Tom93R1 an ICQ message. Click here to add 16640317 to your ICQ list. Click here to visit Tom93R1's homepage. Click here to send Tom93R1 an AIM message. 
View IP (Administrators only)
klaus42


Rotorhead
Posts: 1877
posted January 18, 2005 10:44 AM
Edited By: klaus42 on 18 Jan 2005 13:47

Got racing rubber?

That's your biggest bang-for-buck autocross nessecity; can't tell for sure from those pic's...

Nice & sticky, wide as will fit, with likely significantly higher psi in the front than in the rear...
(I ran 43+ front, 28 rear in a set of 205/50/15 Goodyear R-1's)

:)

Next is that pesky lack of limited slip, and lowering, and bigger sway bars...

It IS incredibly fun, sliding around those tight turns, isn't it? Just be careful not to smash your elbow on the door... or your helmet off the back window!

       
View IP (Administrators only)
Brad


Rotorhead
Posts: 1672
posted January 18, 2005 03:45 PM
Edited By: Brad on 18 Jan 2005 18:50

I auto-x'd my REPU @ JGTC last month

When I met you Tom! It slid like a mother, LOTS of wheel spin and general lack of traction. It was funny, I laughed some too. Afterwards people were yelling ROTARY POWER!!! at me and one guy gave me a beavis and butthead headbang while yelling ROTARY POWER!!! :)

The rear really slides around a lot. I just this week put some fatty 245/50/15 Dunlop SP8000's on 15x8" rims on the rear. It SHOULD stick a LOT better. And the freeway offramps I've been taking at speed seem to agree. I can't afford the 225/50/15's 15x7's on the front right now but I have measured and they will fit nicely.

I'll auto-x it this Sunday and will let you know how the new shoes work out.

I would LOVE a LSD, that would be excellent. I've got some ideas, T][ or 3rd gen might work and I'm looking @ aftermarket stuff for Mazda's and mabye even 70's Fords.
But I need a REPU complete 3rd member to take apart and test with, so my REPU will remain operational during research.

Thanks for the tire pressure reccomendations Klaus!!!!!
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
View IP (Administrators only)
Tom93R1


Redlining
Posts: 458
posted January 18, 2005 09:26 PM

I will definately have to think about bigger rubber on the back. I think I should be able to get some wheels pretty cheap that will fit. I think Discount tires has the cheap steel truck wheels in black or white for about $30 each. They arent too heavy so I think that would be fine. Probably have a better offset than the things I have sticking way out the sides and rubbing the front fender. I just need to come up with a place to store them.

Definately let us know how much of a change you see next time you hit the autocross.
____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

        Click here to send Tom93R1 an ICQ message. Click here to add 16640317 to your ICQ list. Click here to visit Tom93R1's homepage. Click here to send Tom93R1 an AIM message. 
View IP (Administrators only)
klaus42


Rotorhead
Posts: 1877
posted January 19, 2005 08:26 AM

For what it's worth...

...you're welcome, Brad! Dunno how much of that'll cross over to your somewhat more prepared REPU, with different tire brand, compound, size, etc...
It really IS a matter of the specific compound --and the newness of the rubber-- that makes a world of difference, Tom! I wouldn't worry so much about the weight of your wheels, (though lighter is of course better), as I would carefully consider which width/offset will work best for your REPU under the extremes of body roll/chassis movement.
Age and heat cycles will take their toll on the stickiness... and, there's a case to be made for being able to rotate front-to-rear, if you wish to get the most life out of your set...
And yes, of course tire pressures can play a key role!

I think you guys might soon be thinking about tuning the truck to the rubber, rather than the other way around... :)

To borrow a phrase from the classic two-stroke triple MC 'crowd': 'Power without control is... interesting!'

       
View IP (Administrators only)
Brad


Rotorhead
Posts: 1672
posted January 19, 2005 11:13 AM
Edited By: Brad on 19 Jan 2005 14:14

Yeah, these trucks need more control. I got 1 1/8" front swaybar in front, and am considering the ADDCO rear sway bar, that is a complete bolt in kit. Saw one @ SS7 on the green turbo repu. Besides that, have no idea what to do with springs, shocks, alignment, etc........ to get these things to auto-x.

I think I'll try 35psi front (max pressure for the dunlop gt qualifiers i have in front) and 33 for the back fatty dunlop sp8000's.

If anyone has a handeling recepie please post!
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
View IP (Administrators only)
klaus42


Rotorhead
Posts: 1877
posted January 21, 2005 12:41 PM

Ditch the street meats !

Then, soften the springing in back, and maybe cut the fronts a bit, increasing the front spring rate as well as lowering... also drop the back a few inches... bigger front bar, for sure ! ... back one good too... contemplate different bushing material... get LSD in rear... figure out how to best move more weight to back end, forward of the rear axle or just over it... ditch the back bumper... ditch the spare... balance the truck corner by corner to equalize... lighten entire REPU further any way possible... stiffen chassis by building roll bar/cage out from thru the bed, straight off the frame...

But start by getting state-of-the art racing rubber, and don't be shy about inflation pressures!!!

Stiff sidewalls work wonders up front.

Are you plowing the turns before the back cuts loose yet?

       
View IP (Administrators only)
Brad


Rotorhead
Posts: 1672
posted January 21, 2005 04:57 PM

quote:
Then, soften the springing in back, and maybe cut the fronts a bit, increasing the front spring rate as well as lowering... also drop the back a few inches... bigger front bar, for sure ! ... back one good too... contemplate different bushing material... get LSD in rear... figure out how to best move more weight to back end, forward of the rear axle or just over it... ditch the back bumper... ditch the spare... balance the truck corner by corner to equalize... lighten entire REPU further any way possible... stiffen chassis by building roll bar/cage out from thru the bed, straight off the frame...

But start by getting state-of-the art racing rubber, and don't be shy about inflation pressures!!!

Stiff sidewalls work wonders up front.

Are you plowing the turns before the back cuts loose yet?


Thanks Klaus. I'd like R compounds but can't justify having 3 sets for the racecar which has sat in the driveway the last 2 years except for 2 trips to the track, and buy more R compounds for the truck. Budget says Z rated street tires for the auto-x RotorTruck.
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
View IP (Administrators only)
klaus42


Rotorhead
Posts: 1877
posted January 22, 2005 02:21 PM

In that case,

inflating 'em to a really stiff psi --at least up front-- is even more crucial, to decrease sidewall flex, and to keep the tread down where it matters! I know you know what I mean...

       
View IP (Administrators only)
Brad


Rotorhead
Posts: 1672
posted January 24, 2005 10:02 AM
Edited By: Brad on 24 Jan 2005 13:06

245 rear meats really helped out

Truck did not fishtail like in December JGTC. Only time the rears broke loose was when I was either carrying too much speed thru the turn or after the front end plowed and the front broke traction first.

I inflated the fronts up to their max pressure cold (35psi) and that really made a difference. I marked the edge of the tread with shoe whitener and saw that the fronts still did fold over some and wore mabye 2mm onto the sidewall edge of the tread up front, and wore just fine on the rear.

It was a 2nd gear redline course. 1st run got acclimated to course in 2nd gear with buzzer going off. 2nd run tried 3rd gear but it bogged and didn't jump out of corners. Dropped 3 seconds. 3rd run kept it in 2nd gear and kept eye on tach, lots of buzzer but couldn't eyeball tach and focus on course at same time. Drove harder but cooked front tires on a 90* turn and esses, only dropped .26 seconds. 72.76 seconds best time.

Chevy Silverado (competetor in sport truck class) did a 64.00 best. FTD was 55.00 Dodge Ram Magnum V8 truck was quick but didn't catch time. I got 3rd in class out of 3 trucks :( But that's to be expected.

Truck was faster this month. Rear tires and front ^ in psi biggest contributor. Replacing thin REPU steering wheel with thick rx7 4 spoke also helped so I could grab the wheel better. Now I need a MSD 6al so I can set have a rev limiter and not have to worry about spinning bearings. Then front z rated 225/50/15's, shift lite, rear sway bar, new front end and alignment, better intake manifold, dyno time, weekend at streets of willow to tune suspension.....................

Have to see if Arnold and George owe me any $$ :-)


____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
View IP (Administrators only)
klaus42


Rotorhead
Posts: 1877
posted January 25, 2005 12:38 PM
Edited By: klaus42 on 25 Jan 2005 15:41

Nice!

Now, I would likely proceed in the manner you've outlined as well, if I had the funds... my main point being that the R compound will make the biggest difference of all, even if you don't improve/mod anything else... (but, you won't be enjoying the benefits on the street, as you will if you proceed as you've planned...)
Keeping the front stuck down to avoid plowing might be more crucial than decreasing rear sway further... might softening the rear actually increase cornering power?
Also, when comparing times, gotta wonder who had limited slip, nevermind the sticky R compunds on... nice thing being about ST class, it's WIDE open to any and all mods you might care to make! Gotta love that... :)

       
View IP (Administrators only)
Brad


Rotorhead
Posts: 1672
posted January 25, 2005 01:39 PM
Edited By: Brad on 25 Jan 2005 16:48

Yes, I'm considering taking a leaf out of each rear spring but I need to put better tires on the front first. Wish I could afford & justify R compounds, but won't happen this year. I think good z street fronts with 1* negative camber will help the front grab. I'll have pictures from the auto-x this friday.

The other 2 trucks in my class did have big front and rear sway bars; with front bar larger than rear. Need to think about that. Like you said, more rear bar transfers more lateral load to tires which causes tires to slip more...............

I'd love a LSD and would like to buy a spare 4.625 pumpkin, preferably complete rear, to take apart, measure, and compare to T][ & 3rd gen. As well as other old Ford LSD options.

Thanks for the feedback Klaus, any and all help appreciated.
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
View IP (Administrators only)
paulsrepu


Hauling
Posts: 107
posted January 25, 2005 07:46 PM

Greetings everyone, from the owner of the green turbo repu at ss7. I have autocrossed this truck quite alot, and one thing to be careful of is not to use steel wheels with sticky tires. I bought a set of Chevy Blazer rims 15x8 and mounted R compound tires on them and the truck was lightning fast, BUT the wheels flexed and caused the lug studs to seize. With the left thread studs about nonexistant do not take a chance. Use an alloy rim. I even had problems with very sticky street tires. Everyone want's an LSD I hope someone gets one to work without much effort. I am going to start some research into installing a LSD into the back of my truck since wheelspin is a huge problem with 250hp.

       
View IP (Administrators only)
Tom93R1


Redlining
Posts: 458
posted January 25, 2005 10:42 PM

Good point on the steel wheels. I hadnt thought of that, there go my hopes and dreams of having a complete set of wheels to autocross on for $100. Actually, the crappy mag wheels I have might be good autocross wheels and I could bet a cheap set of steelies for the daily driving duities. I think my wheels are only 14" though, how would a 205/55-14 be for gearing on an autocross course? Would I be wanting to go for 3rd all the time?
____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

        Click here to send Tom93R1 an ICQ message. Click here to add 16640317 to your ICQ list. Click here to visit Tom93R1's homepage. Click here to send Tom93R1 an AIM message. 
View IP (Administrators only)
klaus42


Rotorhead
Posts: 1877
posted January 26, 2005 03:51 PM

That's odd...

...since I've seen lots and lots of autocrossers in all classes run R compounds on steel wheels... even lightweight steels... (!?!) Perhaps it's a question of specific ones/combinations/ sizes ?

Tom, consider how low our REPU's are already geared... and that you may wish to retain overall outside total wheel/tire diameter... (Hence my switch to 205/50/15's; they approximate stock diameter.)

       
View IP (Administrators only)
Brad


Rotorhead
Posts: 1672
posted January 27, 2005 10:41 AM
Edited By: Brad on 27 Jan 2005 14:06

Pictures:

http://www.shinobibmw.com/autocross/2005/01-23_CSCC_1/image.htm?autox_65.jpg

http://www.shinobibmw.com/autocross/2005/01-23_CSCC_1/image.htm?course_65.jpg

http://www.shinobibmw.com/autocross/2005/01-23_CSCC_1/image.htm?course_72.jpg
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
View IP (Administrators only)
klaus42


Rotorhead
Posts: 1877
posted January 28, 2005 08:38 AM

Have you tried

...ditching your back bumper? It's quite heavy --and you do need some weight in back-- but, it hangs too far out there!
Since truck class is wide open, you'd be better off adding the same amount of weight right over or just forward of the rear axle... I've seen some guys put sand bags in a 4x4 frame to kep 'em in place between the wheel wells...

       
View IP (Administrators only)
Brad


Rotorhead
Posts: 1672
posted January 28, 2005 10:00 AM

I'd like to ditch the rear bumper for auto-x but I like to drive on the street with that bumper on. It's solid and can take a hit. Seen what happens when a pickup with no rear bumper gets rearended..... tailgate, pan, tail lites are crushed; bed floor and bed rails bent....

I'm considering removing that bumper for auto-x, but last time it took me 15 minutes, floor jack, and girlfriend to put it back on. And it is right next to the painted pan that I don't want to scratch.

Is there a lighter rear bumper?
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
View IP (Administrators only)
Brad


Rotorhead
Posts: 1672
posted August 23, 2005 10:19 PM

has anyone autocrossed their REPU lately

and how did you do?

any new suspension setup ideas?

how do we get a REPU to handle on the autcross course?

anyone have good alignment settings?

thanks,
brad
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
View IP (Administrators only)
All times are PST (US) [' This thread is 2 pages long: (1) 2 ']
Post New Poll   Post New Topic    Post New Reply
Rate Topic:
Powerd By: BlazeBoard

[Home | Mail Archive | Join the mail archive | Photo Gallery ]
0.042777061462402 seconds processing time