johnsopa

Used to race a Spec Racer Ford decently. Usually finished top 10 at regional races. Only did that about five years. Mostly DE since then with normal street cars.

Picked up an old (2004) Radical SR4 last year. Local shop got it prepped over the winter (replaces uprights and similar due to time, base alignment, new tires, etc.).

This weekend will be my first time driving the car on the track and I'm looking for some insights on what to expect with respect to slicks and the introduction of some aero.

Definitely not planning to push real hard. Will probably do a lap or two just to make sure everything is good mechanically then come in. The shop is sending a guy with me to do trackside support, he suggested starting relatively high on the tire pressure for three laps after the first two shake down laps and then come in and let him adjust pressure.

This is my first time ever using slicks on a car and I'm not really sure what to expect. I've heard that audible feedback from the tires will basically be nonexistent but honestly that's not something I used much before, at least not consciously.

Any insights or advice will be appreciated.

I'm naturally pretty cautious in working up to speed. Have a high sense of self preservation. Haha.

seanseidman

I do't know the sr4.
I went from a spec boxster to the sr3 1340.
The aero works at high speed, not so much at low speed.
It took (still taking) me time to trust the aero.
you are right, slicks are quiet, have tons of grip, and drop off quickly.
Watch lots of footage onboard.
Enjoy the ride!

CharleyH

Check out this post over on the Radical Sportscar Registry Forum. https://radicalsportscarregistry.com...radical-owner/. That is a good place to ask Radical specific questions. You can also send an IM to Radical Registry member GrahamD who’ owns a similar car.

The short answer to your question:
1) make sure the engine is up to operating temp before hitting the track. Make sure it does not go over 100 PSI or you risk blowing your oil cooler.
2) make sure your tires are up to temperature before you push the car. It takes a couple of laps.
3) These cars require smooth front to rear balance changes or they will spin. If / when you spin it I see essential to get the clutch to the floor immediately or you risk blowing the starter and ending your day.
4). If your car has an Aim dash, bring your laptop and review data between sessions. Use the color map showing lateral G’s and use the information to recalibrate your brain to what Downforce is capable of.
5) Have fun!

Charley

924RACR

Where's the pics???

ProCoach

Radicals are fun. Sports racing cars are fun. Congrats. Capabilities way beyond SRF Gen 1 and Gen 2.

Biggest difference to me is not aero (although that helps in a few places on faster Eastern tracks), but tires.

I would not scrimp on tires. If you don't know the age or the history, buy new ones. It'll be awhile before you're up to speed enough to burn through them quickly, but don't scrimp.

Warm them up before you lean on them. Be aware the level of stick varies more than the old spec tires on the SRF between out lap and up to temp. Best way is brake-gas-brake-gas, not side to side.

First, maximize longitudinal axis commitment. When the wheel is straight or near straight, commit to full throttle and full brake. Make clean, quick and decisive transitions.

Then, focus on progressively quicker progress from throttle tip-in to WOT. If you have to wait too long, or heaven forbid, back off, you finished braking too early or you held the brake too long (overslowed).

Finally, work up incrementally the vehicle speed at which you finally release the brakes. This last part is hard, because you'll drive to what you think the car will accept, as opposed to what it WILL accept.

How you ask it (or rather, TELL it) is a key ingredient to the chassis accepting the input. Have fun! We had two dozen at David Murry yesterday and the day before, always fun!

seanseidman

ProCoach, great insightful comments
"Finally, work up incrementally the vehicle speed at which you finally release the brakes. This last part is hard, because you'll drive to what you think the car will accept, as opposed to what it WILL accept."
Are you implying that with time and confidence, you can trail less in slow corners, carrying more mid corner speed?

924RACR

Wow, Peter!

I know all that stuff, yet I still feel a need to print that out, frame it, and hang it on a wall...

ProCoach

Just so we're on the same page...

Imply:

1) strongly suggest the truth or existence of (something not expressly stated).

synonyms: implicit, indirect, hinted, suggested, insinuated, deducible, inferred, understood

2) (of a fact or occurrence) suggest (something) as a logical consequence.

Both of the above. I've seen it as drivers accumulate experience and confidence, and the OP's experience in SRF's will help.

In these cars (and others, as I've said before), the braking and corner entry phases can be broken down to five zones or areas of control input timing (how fast) and amplitude (how much).

I prefer to think that you'll trail more effectively, more perfectly blending the end of slowing to the point where throttle can begin to immediately progress to WOT again.

Whether that takes quicker brake pressure release because the grip capability, rotation and/or steering scrub "takes the rest of the speed off," allowing progressively higher entry speeds while still being deadly accurate in car placement at the apex, or...

Whether that allows the addition into the equation of later brake application, because the higher speed and quicker release of the brakes at the end allow NO WASTED TIME approaching and at the apex, it's ALL good...

That's why we keep doing it, right?

I had another long dinner with Ross Bentley last night and we would have kept talking ABOUT THIS, if we hadn't had to go to work or learn more today...

seanseidman

[QUOTE=ProCoach;15785205]Just so we're on the same page...

Peter, thank you for your detailed explanation.
As always, you are bang on!
Time is gained by earliest to wot; which requires accurate placement at apex.

ProCoach

Yeah, very true, but...

Sitting in the Oak Tree corner spectator bleachers with Ross Thursday watching everyone from Spec Miata and DE drivers out there with Daniel Morad, Greg Liefooghe, Colin Braun and Ryan Dalziel, we were struck by how MANY cars went BACK to throttle prematurely, requiring either a substantial delay to WOT or an outright fix (backing off, then going back to the progression to WOT).

Most of these folks who did this (and I saw some rough driving by some of the "pros," not only in car placement, but in best practices of technique) were overslowing going in, NOT tracking out from the exit of T11 (the turn before) and felt like they HAD to go back to power, resulting in NOT being "earliest to wot," as you correctly state is the goal, commensurate with proper and accurate car placement.

There were some dicey moments as some of the more accomplished and well disciplined drivers pushed their speed up through T11 into the braking, final downshift and turn in for T12 (Oak Tree, leading onto the nearly mile long back "straight"), but when they hit it right, it was a pleasure to behold! Their speed trace was a perfect "V," with the turning moment very short in time and distance. THEN, they were able to really have pretty good "throttle speed" to WOT.

Fun stuff.

seanseidman

I can listen to Peter all day!

What is an SR4?

ProCoach

Old. 2004-5, IIRC.

https://www.topspeed.com/cars/radica...-ar102728.html

DOUGLAP1

These guys can give you way better technical advice than I can. But, I will say that for me learning to trust the aero grip of a real race car with wings (and in your case ground effects), is a rather difficult and eye popping experience. Learning that you really can stay flat through turn X,Y,Z takes some effort, and should be approached in stages. It is good to follow someone in a similar car to re-calibrate your senses.

seanseidman

+1
Even knowing flat is doable in corner x, it's still tough to keep your foot pinned!

CharleyH

I found the exact same thing. I would look at the data and I could clearly see that I could be flat out through Turn 8 at willow Springs (~135mph). My brain would tell my foot to stay flat on the floor... but my foot wouldn’t listen. It took several sessions before my brain could convince my foot that staying flat was survivable

Charley