arutha

iTrader: (2)

Hello,

I was at Summit Point Main this past weekend (first time) and the whole car was sliding some in turn 3, 7 and once in 10 if I remember right. Understeer between 6-7 but that sounded normal.

Curious if camber could help this issue or something else I need to look at? Believe the alignment is set for Pettit's recommended settings, maybe -1 camber. Seemed like all 4 tires were losing grip.

The car I was keeping up with was doing 1:30ish times if that helps at all.

Setup is below.
FD with Ohlins. 11kg front, 9kg rear, stock sways both front and rear. 255/40/17 front 275/40/17 rear, running Toyo RA1, not shaved and they have a good bit of tread. Tire pressure hot was 35PSI all around.

I am relatively new to this but absolutely don't want to do anything else!

TomU

iTrader: (11)

staggerd tires cause understeer

A lot can be learned from this...

https://www.rx7club.com/suspension-w...-setup-723617/

Also google understeer/oversteer

I tracked a completely stock FD (at SP) and it hugged the corners, that is till i blew my o-rings. Hope you aren't running the stock cooling system. You need at least an upgraded radiator and a 2nd oil cooler

Welcome to the club

arutha

iTrader: (2)

Thanks Tom,

All four tires were sliding, understeer was only between 6 and 7 which according to my instructor and other drivers seems to be very common at that point of the track.

And yes, have a v-mount setup, dual oil coolers etc. Seems to keep the temps down pretty good. I'll check that link as well.

Thanks

Mahjik

iTrader: (1)

Non-shaved RA1's will squirm when they heat up. In most cases, r-comp's will want more camber than a street setup. However, to know what's going on with your car for sure, you'd need to take temps of the tires to see how evenly spread the temps are....

When you say sliding, do you mean sort of a power drift or the rear starting to come around on you?

evo_koa

iTrader: (2)

what is your ride height set at? what is the dampening set at on the coilovers? 35 psi hot is to high for the rear, you typically want 3 less psi in rear,

arutha

iTrader: (2)

Power slide, the whole car is moving side ways. I'll need to look into a pyrometer for next season.

I feel the squirm when breaking and turning in, certainly a strange feeling.

All in all the car seems pretty neutral, just seems like I don't have enough grip when taking some corners at speed and thought it might be the alignment or something else. Seems the tires should be holding better.

I'll need to check how many clicks the Ohlins have, ride height is around 25.25 inches

sa22rally

i would think 35 psi is to much if i run 35 psi on my 1 gen rallycar with tarmac rallytires they overheat in the middle of third lap

arutha

iTrader: (2)

The 35 psi is the hot measurement, probably around 29psi cold.

Oh and I am wrong with the powerslide comment, all 4 tires seem to be losing grip, not just the rear, I didn't fully understand the meaning of powerslide. Sorry

Fritz Flynn

iTrader: (263)

<<<@!1!@>>>

For a street/track car with 275 40 17s I'd recommend:
F 1.8 camber 6.5 caster 1/16 total toe
R 1.6 camber zero toe

I'd start with 27 psi pressure and try not to go over 34 hot when you get out of your car in the paddock. By the time you cruise in, park and get out of your car, the pressures have probably dropped 1 or 2 pounds.

T3, T9 and T10 are fast HUGE 4 wheel slide/drift turns which is perfectly normal and if that's happening it means you're doing it right. A 1.30 is pretty good

Once you are comfortable or have good car control there won't be any corners you aren't sliding in.

Here's a vid from a time trial at spr I'm slowing down at different points to get some space but after the second time through t10 the hammer is down.

Fritz Flynn

iTrader: (263)

Here's another VID from SPR that really shows just how much the car slides all the time when you are at speed.

arutha

iTrader: (2)

What would you recommend if the car doesn't see the street much? This past year I probably only have 100 street miles on it.

And thanks for responding Fritz, knew you go there. :-)

Fritz Flynn

iTrader: (263)

F 2.4c 5.8 caster 1/16 total toe

R 2.2c slight toe in like 1/32

The above is pretty much my setup but there are #s all over the map. Some people like negative front toe and more positive rear etc..... which is actually a more traditional track setup but IMO the FD doesn't need help turning which allows me to be pretty conservative.

wrankin

Pardon if this is a stupid question but isn't "the whole car is moving side ways" more an indicator that you've simply exceeded the grip capacity of your tires? You can start tweaking your suspension in an attempt to give you more overall grip, but I would be cautious about major changes - it sounds like you are set up pretty neutral right now and you probably want to avoid introducing any unwanted under (or over) steer into the car.

The "squirming under braking and turn in" could certainly be related to your toe settings, so that's definitely worth a look.

Also remember that full-tread RA1's can and will overheat quickly on a higher power car like an FD. I would recommend that you get them shaved to at least 6/32nds (or even 4/32nds) for your next set. They will actually last longer that way. I love the tire - I run them on my FC, but at full tread they will squirm some and have quite a bit more slip angle. In my experience once you wear through the tread blocks, the tire is much more predictable.

Finally, while they are a very good lapping tire remember that they are no where near as soft and sticky as say, a Hoosier R6 or similar. Especially if they still have tread on them. For similarly set up cars, in general the Hoosier will be faster through the turns. Now whether or not the driver can capitalize on that advantage is a *very* different question. ;-)

Hope this helps,

-bill

Mahjik

iTrader: (1)

arutha, I'm not sure I'd take Fritz's video as atypical. Not to say track cars don't slide, but Fritz seems to be more on the extreme side of the dial when it comes to sliding.

However, it's likely the tire isn't heating properly with your current alignment. The RA1's are going to want more camber than a street setup. Add in that they are unshaved, and you are probably only getting partial potential of those tires. The hot pressures look good for RA1's but I've seen the Miata guys run those at higher hot pressures (38-40 PSI on a warm day, and 35-38 PSI on a cool day). I don't think I would target more than 36 PSI hot myself, but you might try.

Unfortunately, a lot of tuning will require an investment with some tools like a pyrometer to get your tire temps. You will likely need to tune your suspension (outside of alignment) as well. A basic guide is embedded above, but you can find more detailed diagrams around the web. The most helpful thing would be in-car video so we can see the behavior of the car.

arutha

iTrader: (2)

I guess my complaint was that I expected to be stuck to the road better and therefore quicker. Sounds like a tire change and possibly an alignment might help.

As for Fritz sliding a lot, thinking he likes to push the car to it's limits, which I can see myself liking as well. I'd be lying if I said sliding wasn't fun. I just knew my car shouldn't be at it's limits yet and since it was, why.

Thanks guys

Fritz Flynn

iTrader: (263)

Next time get some video

Fresh RA1s and a good driver in a bone stock FD on stock size rubber will be running 1.26 laps at SPR so I doubt you were over driving the car or near it's limits.

Squirming under braking and turn in can be a multitude of things but in general it's a driver who is squeezing the brakes harder and harder as the car slows which leads to more squirming because the rear is unloaded under braking and the car enters the corner with the nose down.

Ideally the driver should squeeze crazy hard initially and progressively/slowly raise the pedal balancing the car before entry or entering with a level nose. I always say it's not when you hit the brakes but when you release them that really counts. Many drivers even advanced drivers brake too deep blowing the entry because they turn too late and the car isn't balanced. More importantly it's a hell of lot safer to brake early which allows enough time to balance the car for a safe and fast turn in.

Fritz Flynn

iTrader: (263)

Here's another lapping SPR vid


Note the S2k at about the 3 min mark. I think that's Rob Robinette who may still hold the lap record at SPR for the S2k. He's the long time FD owner who has the really cool tutorial site. My tires were completely gone so a big slide following the pass on the S2k in t10 and another one following that in t5. If the car is in control you are not going fast enough LOL

gracer7-rx7

iTrader: (16)

IME, RA1s provide best grip around 38 PSI hot. Less than 36 and you can't get max grip out of them. More than 40 and they feel greasy. Cold or hot days only determine what cold pressures to start with in order to achieve my goal of 38 PSI hot. To take that measurement, I don't run a cool down lap - I push it during the cool down lap to keep tire temps and corresponding pressures at what they'd be on a hot lap of a race. Its pretty amazing how different the tire feels with just a couple of PSI pressure difference.

+1 on the RA1 being a better tire once shaved. 6/32nds is a good compromise if you are exposed to wet driving. If not, start at 4/32nds. It makes a big difference in tire feel and greatly decreases tire squirm.

Different brands and models of tires will behave differently depending on tire pressures so you can't make blanket statements or recommendations on tire pressure w/o taking that into account.

gracer7-rx7

iTrader: (16)

Good points here. Different drivers are comfortable with varying amounts of slip angle. Part of that is also how much risk you want to take.

+1 on not making many alignment changes just yet but you may benefit from a little more camber.

The only real way to tell how much camber you need is by using a pyrometer. Anything else is just trial and error w/ some guessing thrown in based on subjective feel. Try searching for some old posts from John Magnuson (or does it end in en...?). He was fast and had done some pyro testing on alignment settings. I vaguely remember him saying something about Pettit specs but how much heat you are putting in the tires will vary depending on driving style and how hard you are pushing.

Squirming under braking definitely sounds like toe. The FD and Miata don't really like 0 toe in the front. They seem to need a wee bit of toe in or toe out to eliminate that hunting feel. A wee bit of toe in at the rear helps high speed stability. You tend to feel tire squirm on corners more than braking iirc... Also, re-bleed your brakes just in case. inconsistent hydraulic pressure at the calipers due to air will also cause squirm under braking.

If you aren't able to drive hard enough to get RA1s into their tire temp and corresponding pressure happy zone, I'd suggest not jumping into something stickier just yet.

My .02 cents...

arutha

iTrader: (2)

I agree Fritz, I am not experienced or fast yet, so trying to figure it all out. I am definitely slow in turn 5 and the understeer between 6 and 7 was slowing me, a new cayman s pulled on me coming out of 6 but I was back on them by turn 8.

And the squirming was most noticeable at turn 1 and 5 so that makes sense

arutha

iTrader: (2)

I think I am driving hard at this point but have no problem sticking with these tires, there are other places for me to get quicker. First I have to get the car running again but wanted to have this discussion prior to me forgetting everything that happened.

gracer7-rx7

iTrader: (16)

^Understood. Analysis is a good thing

j9fd3s

iTrader: (3)

the Ra1's seem to like more slip angle than most tires, or they don't punish you for sliding around. most other tires we've tried don't like to slide around as much. with the FWD honda, we can ruin an R6 in 1 turn...

we've also found that front toe does nothing to lap times, but it does make a big difference in feel, so i'd start at zero, and try 1/16th in, and 1/16th out and use whichever felt best. don't spend a lot of time here.

rear toe is really really important though. the honda and the FC are really picky, the miata less so. again start at zero, and add toe in.

its been a while since we ran Ra1's, but they like a lot of negative camber. if it was my car i'd just max the negative camber out, it'll still probably want more than that....

23Racer

One of the hardest things when you are starting out is filtering the advice. Unless you are getting the tires in their operating temp and pressure ranges, you are really chasing smoke. Fine alignment adjustments may help but as soon as you go faster the requirements change. If you are doing 1:30 and Fritz is 4 seconds faster, that's huge and your needs mat be different.

I ran Toyo RA1's and RR's and R 888 ' s this year and the only consistent thing was that they all wanted big camber to work well. I was at 4.5 in the front and 2.5 in the rear. The only way I could tell was by checking tire temps as I came off the track. They all want to be in the 200 degree range to work properly. Also, I run at very fast tracks mostly and I shoot for 38 - 40 lb hot pressures to control sidewall deflection on the RA1's. The RR'S liked about 34 and I haven't found the sweet spot on the R888 yet.

When I changed over to some Conti slicks, I burned off the inner edges in 1 day at those camber settings. Tire temps and manufacturers recommendations are key. If you aren't at the temps yet, drive harder.

Eric

gracer7-rx7

iTrader: (16)

Yep, RA1s tolerate slip angle quite well. They aren't the grippiest tires out there but they are consistent and tolerant and last a good 20-30 heat cycles in SM use on a Miata. I run ~-3.1* up front and a similar amount in the rear of the Miata and get even wear. I've never checked tire temps using these.

Not entirely sure what you guys mean when you say the tires "like" lots of negative camber...

Agreed on your toe comments.




Yep. Agree with your comments also. Especially the topics in the first paragraph.