Camber for semi slicks

[Slugoid]

Just wondering what are suitable camber settings for semi slicks?

Currently I'm running around -1.6 deg of camber all round and wondering if I should bump it up to say around -2.0 deg to stop the outer edges wearing out faster. However, I won't be running semi's off track, so -2.0 might be too much on the road.

Any suggestion?

[kula]

i run -3 on the road all round.
no problems.

[StanTheMan]

I'n not quiteas bad as Kula.
-2.5 front -2.25 rear.
but its been about a year since mylast allignment.
so it could be anything.

[Slugoid]

Well the \"proper\" alignment place was fully booked today and yesterday, and I'll be heading down Winton Sunday night

Guess I have to run with a little less camber than I had wanted and hope it won't shred the outer edges to bits.

Another question, what sort of pressures are you running with semi on track? I'm trying 30 psi cold (due to less camber) and maybe keep it under 35 psi hot. Is that too much or too little?

[rhysk]

I run -2.7 camber

Street tyres are RT615, they are wearing evenly
Track tyres are Kumho V700
Both at 36 hot.

[Cal]

Both at 36 hot.

You might want to try bringing the semis down to more like 29-30 hot.

Cal.

[Slugoid]

Both at 36 hot.

You might want to try bringing the semis down to more like 29-30 hot.

Cal.

That's interesting. I ran with my current settings (-1.6 deg all round) and I was around 35 hot, 30 psi cold. Felt fine most of the time I was at Winton, and I wasn't going all over the place. Or maybe I just wasn't pushing it enough

I noticed that my outer edges came out much better than expected, considering my low camber for semi's. I followed the Toyo Pit Lane for my pressure and it said to add "3 - 6psi to recommended cold and hot inflation pressures usually prevents the outside tread shoulder over-heating". Seems to work, but I think I will definitely try more camber and a tad lower pressure for even more grip.

PS: I find that pressure a personal preference and trial and error as well. 29-30 hot would be nice if you had at least -2 deg of camber or more, or else I can image the outer edges would be gone before the inside even gets a working. I'm no "real" expert in this field, and I'm sure Cal is more experienced on track than me, but that's just the way I see it.

[Boags]

I have read that lower pressures will give you more initial grip, but turn off like a light when they do go. Higher pressure will have less initial grip but be more progressive. Setting your pressures higher for beginners would seem to be a good idea, and lowering them as you get better.

I run 28-30 cold in my R888s and find that is nice and progressive when hot, but still sticky enough to hold in the corner. I don't carry enough corner speed though, so if I was pushing it harder it might be a different story.

Please correct me if you know otherwise.

Boags

[Cal]

There are loads of variables. Obviously we are running -3 degrees or more camber if we can get it. Very agressive caster and bushes with little or no compliance. We would also get less chassis flex with the side intrusion bars and diagonal cockpit bar. Boags is correct in that the higher the pressure the more progressive they are, but they wear quicker too. I start at about 24psi cold and bring them up to about 30psi hot. As the day gets hotter I may need to let a little more out at some point. Very different from a road tyre in the pressure department.

Cal.

[Slugoid]

I have another quick question. What's the maximum camber you can get with a NA6?

I had a nice chat on the phone with someone at Meridian Motorsport today and I was informed that the NA's had a limit to the maximum negative camber it can have. I forgot the number, but it's no more than -2 deg or something.

If I wanted to have even more camber (say -3 deg) how would I go about it?

[StanTheMan]

you could get an adjustabble camber bush kit.


talk to boy racer.

[Cal]

Yep Stan is onto it. We use offset lower control arm bushes. They only seem to give about -3 though. There are ways to get more again, but I've not tried them.

Cal.

[Charlie Brown]

Very interested reading the above comments following my first outing on DOT tyres on Monday.

I started with 26psi cold and found the tyres were warmed up after almost a lap of Wakefield.
I used this first series of laps to test out the limits of the tyres and to see what happened when they let go. I found them to be very progressive with plenty of time to dial in steering changes to correct any slip.

The second session I had a bit of a go and managed to record what ended up my FTD. I didn’t check pressures thinking that I had the balance just right.

Third session I managed to get myself out first in the group and thought I had the hang of the tyres so really put the boot in but the times didn’t reflect the expended effort. So I checked the pressures. The rears were running 33 hot and the front left 38+psi and the right 36psi. Obviously more work was being done on the left side because it’s a clockwise circuit and the car tended to understeer due to my tyre size combination.

So I dropped the fronts to 33psi and went out for the six lap regularity. Track temperature had risen by this time and my times were still slower than the second session.

For the last run of the day I dropped the pressures to 30psi rear and 31psi front. The tyres complained on some corners, and I’m not sure if DOT tyres are supposed to squeal or not, however the times were quicker and apart from the first lap the next three were within 0.3 second of my best lap. Maybe someone can let me know if DOT tyres squeal.

For the record I‘m running 2 degrees negative F & R with 16x8 rims fitted with old, well used 205 V700 Kumho’s on the front and 225 Dunlop D01Js on the rear.
Next time out I hope to have some fronts to match the rears. Then with a bit of tweaking maybe this almost stock NC can loose half a second and drop into the 1:12s

[Cal]

Yeah they can squeal, but really shouldn't. I found they did on the green car because it didn't have enough negative camber. Was about -2 like yours. Also an indication that the pressures might be a psi or 2 too low. From memory, i think they'll squeal if over inflated a LOT (like 40psi) too.

Cal.

[Charlie Brown]

Thanks Cal, next time I'll try 32 hot and see what happens.