Understeer help

[gungo]

I went to Bedford aurodrome the other day and-

In the wet morning the Clio was very tail happy and a whole lot of fun. :lol:

As the track started to dry the car became amazing. As the front started to slide, a very slight lift would bring the back end gently into line with no real danger of big oversteer, 8)

Although the track never dried completly, when it was at its driest I couldn't get the rear end to move at all. All understeer and no oversteer doesn't feel that that fast but more importantly (i am not racing) it isn't as much fun. :?

I am running R888's (approx 31 front 30 rear) on the track and have never checked the geometry.

Should I be looking to increase the negative camber on the front or could I change the balance with tyre pressures alone.

I have spent a few hours trawling through this site trying to find some standard numbers for the cars geometry so that I can get it checked as a start point.

I have come up with
Standard Front = 0.17 negative camber / 0.25 toe out
Standard Rear = 1.75 negative camber / 0.2 toe in

Best Mod Front = 2.0 negative camber / 0.15 toe out (requires new camber bolt)
Best Mod Rear = Standard

Do these numbers sound right to people and is there any other advice for getting less understeer.

Thanks for any help.

P.S From reading so many posts on the subject it sounds like most of these cars should have the geometry checked as the factory setup is fairly unreliable. I couldn't find the standard numbers anywhere and the numbers I have written is my best guess from reading so many posts. Should this (not mine but the correct) setup info be a sticky.

 

[hoolio]

Not had mine sorted and i'd like a definitive answer to this as well.

Fairly certain what you've posted is the correct mod, not sure what they were meant to be originally as like you say they all seem to be all over the place. i'm sure George etc will be along to sort this soon.

 

[vamos]

I am also interested in this

The traditional remedies for curing understeer would involve a combination of softening up front (tyres, dampers, ARBs) and stiffening up rear (tyres, dampers, ARBs). The Trophy has tyres and front dampers available for tweaking straight away, so I would try that and see what hapens.

A low cost mod would be a stiffer (adjustable) rear ARB, such as the one made by Whiteline. Adjustable rear dampers and/or stiffer rear springs are more costly.

One observation I would make now, is that you seem to be running quite high pressures in your R888s - the extremely stiff sidewalls should enable you to go lower (cca F24, R22 cold IIR) and then play around with increasing rear, or dropping front.

I look forward to gettig my own Trophy to put these theoretical musings into practice.

PS: On a related note, does anyone know if the adjustable front damper is adjusted for low speed bump, or low speed rebound (or both in combination)?

 

[George K]

Agree with best mod settings. (I might experiment wiht running front wheels at parallel this year). Track tyre pressures are much lower Kumho recommended 26/24 (which I find fine) - some run even lower. Rear arb won't help much as rear wheel lifts very easily any way!!

Always run with TC off.

Softening front dampers will not help as that will spoil turn in and create a forward weight transfer - which is counter productive.

There is a big temptation to go stiffer all round, after all the racers run springs about four times stiffer, but it would probably spoil the car for the wet and for the road. Mark Fish apparently has developed a set which are a compromise.

 

[g40steve]

George is this what i should be looking at??

Standard Front = 0.17 negative camber / 0.25 toe out
Standard Rear = 1.75 negative camber / 0.2 toe in


Getting mine set up next week as pulling to right?

 

[gungo]

I agree I am probably running the pressures too high, but this was the first time I have used these tyres and I had no info on pressures.

When on track when should I measure the pressure.
I started at 32/31, after 25 minutes on track they were 38/37.
Dropped them to 32/31. After another session they were up around the high 30's again.

I assume the pressures I am after should be with the tyres hot. So I should expect to be letting the air out for a while at the start of a day.

 

[George K]

G40 steve - as far as I can remember those are the standard settings or close to them - can't check my files until the weekend - however I would have expected the front ot be more like 0.5 (30') negative and 0.25 (15 minutes)toe-out.

You need to get a 4 wheel alignment check if you have a pulling to one side problem.

Gungo -I only do short runs so i do not have a pressure change problem - would guess they should be reset when hot - this is why in racing OFN (Oxygen free nitrogen) is used as it is much more temperature stable.

 

[Cue]

on track you should check your tyres pressures immediately after your first proper run as they will increase.... R888's can go from 30 psi to 55psi after only a few laps, this will hinder the cornering ability.

I'd start with 30 run for 5 or 6 laps then drop them back to 30. Makes sure you take a pump with you to increase them back as surface water has a marked effect on tyre temp.

 

[vamos]

So the best way to reduce understeer with the Trophy is to increase front negative camber? Is there a camber kit commercially available (i guess yes) and where from and how much?

 

[George K]

It is probably the first and cheapest thing to do. You can buy camber adjusting bolts, or use aircraft grade 12 mm bolts and nuts, or elongate by 2mm the top hole in the the flanges at the bottom of the strut which connect onto the hub carrier.

Cue, I am quite surprised by you running as high as 30 psi - have you checked with Toyo?

 

[Cue]

The 888's i'm currently running are called Trampio, they are manufactured by Toyo but they are 55's not the usual 50's and have re-enforced sidewalls, so can take a lot more pressure and hence less wear... i think they are for endurance use.

Recommended psi is 32 when hot but i run them slightly down as i find that higher psi has the rear end squirming under turn in.

 

[Steve]

You seemed to be doing alright when I saw you!

 

[Steve]

..and some others from the day. Nice to meet you guys, you were both very quick when I was on track, couldn't keep up at all, had to let one of you past at one point I seem to remember.

I'll be back with some fresh tyres (and a tiny bit more talent) for a rematch!

 

[amm]

George is this what i should be looking at??

Standard Front = 0.17 negative camber / 0.25 toe out
Standard Rear = 1.75 negative camber / 0.2 toe in


Getting mine set up next week as pulling to right?

the trophy has got more than 0.17 deg neg camber it is around 1 to 1.5 deg neg camber

 

[amm]

i have done 10 track days with r888 i run 24 psi front and 30 psi rear i still think that my front tyre pressures are to high tho and +0.1 tow out .

i am also running -2.5 deg camber on the front and i have taken it up to -3 deg camber when i was at spa last year with Renault sport

 

[Cue]

i think i might only get another day, maybe two out of my tyres so will be switching to the slightly stickier UK spec R888's come spring/summer time.

 

[Matt X2C]

without taking the piss, could it be something as simple as just a right foot that is too heavy.

the easist way to make a FWD car understeer is a heavy right foot!

 

[g40steve]

Destroying tyres is easy, preserving is where it's at :-w

Also driving beyond the cars /owners (poke) capabilities won't help :roll:

 

[g40steve]

Had tracking set at parallel, car seems more stable & now don't wander (tup)

 

[amm]

Had tracking set at parallel, car seems more stable & now don't wander (tup)

glad to hear it m8 we have just got to get you on track now :wink: