Help! Overloading outside front on track in our Mk1

Hi all,

I really hope y`all can offer some sound advice from experience.

Help!

My son and I have a Mk1 with ABF on 15" 195/45 T1R`s

VX 256 brakes good pads uprated fluid so it stops fine, rear discs, Hi-Con GT coilovers, standard ARB`s front and rear.

Bedford (dry but cold) a month ago

0.5 degrees camber and 0 degrees toe

26 psi all around (warm)

Heavy sidewall wear on the offside front (Bedford is primarily left handers) and all tyres had some heat in them (even marbling)

Great balance, easily driven, self correcting on lift off no vices and with reasonable turn in but inside rear lifting and understeer due to overloading the outside front!!!

Bedford (dry but cold) yesterday

1.5 degrees camber and 15' toe out

Much better turn in and even wear (ironically appears less heat in the fronts - less marbling) at 26 psi and set 29 psi at the rear to let the rears move a bit as I wondered if they were digging in too much but they still had heat in them.

But........................ its still overloading the front and lifting the rear so understeering particularly on tight bends - its like washing out until it finally scrubs off and digs in then it snaps back on line. The new Febi mount on the offside front shows a bit of a gap from the top plate to the rubber so its taking a hell of a beating.

I think it needs stronger springs at the front (softer rears as its stripped out?) but I would welcome any suggestions and in particular spring rates that people are using successfully as it does have potential.

 

Hi there.
I think the best set-up to go for would be the classic 'Slick 50' one. They used road tyres too, and the trouble is getting rid of the understeer - like you say.
I did a few trackdays with this set-up on road tyres (exactly as it came from the championship) and it works very well.

The spring rates are usually soft on the front and solid on the back - say around 250-300 front - 500-800 rear
They have 28mm rear anti roll bars too, and sometimes remove the front one altogether.

How much tread is on the tyres too? Road tyres dont like taking abuse if the tread blocks are still tall - they lean over and the tyres get very hot like you are saying. You get a lot of beading along the blocks. You can get them buffed (shaved) to 3mm, and they will work much better.
Or buy used ones?

Your front tyre pressures sound a bit low when hot (26psi?). This will also mean the tyre is folding under a bit more, and generating more heat. Try setting them more like 30-32 when hot I would say.

What do you think?

 

I agree with samfish's approach of a stiff rear setup but I do it slightly differently. The kw rates are 342lb/in front and 280lb/in rear. With that I run a front arb but I also run loads of rear bar instead of a very high rear spring rate.

Even with these rates, the front needs the arb to keep the front planted.

I can never run below 2.5 degrees camber even on road Tyres (T1-R's) and actually run about 3 degrees for and even wear across the tyre.

I start off 25/26 psi cold all round and normally end up with 30/31 psi hot.

The rear wheel in the air isn't an issue as long as it's only just off the floor and not a foot high!

Anyway, what are your spring rates and arb specs?

Gurds

 

Great advice so far, I used to run my road tyres at similar psi mentioned above, but after having some tuition the tutor advices running the tyres higher because they are road tyres they do not have a strong side wall and they flex during braking and cornering. So we put the fronts up to 35-38 hot and rears were around 33. It did make a noticeable difference during braking, the car held it's line better, and it felt just as good in the corners.

Inroad tyres like T1 R I would experiment with different psi until it feels right to you! I know on slow tracks such as Curby people run lower psi to try and get more grip, there are less forces acting because the track is small and slower than Combe say. So the track you are on will affect your setup too.

 

Raising the rear suspension a touch can help turn-in too. Doesn't look great, but it works and may relieve the outside tyre of a bit of work when initially winding on some steering lock.

 

Hi Samfish, thanks for the input.

The tyres are 3/4 worn T1R`s, I did get beading a month ago with 0.5 degrees camber but less heat yesterday with only slight beading but beading on the rears.

I`ll try and up the warm pressures and see what happens - to be honest a missed opportunity as I should have experimented a bit more as they were 26 psi cold and went to 31 hot so I dropped them to 26-27 hot

That seems very high to me on such a light car, my Westfield ran 14 - 18 psi on track.

My concern is the huge amount of understeer, its not what I`m used to in past cars (Westfield, Ginetta G27V8, Porsche 944 Turbo) and its putting me off developing it further if this is a common issue with Mk1`s.

Hi Gurds

I have researched and cant seem to find definitive answers which I find puzzling - even you two have differing opinions

I dont know what the spring rates are (I`ll reseaerch what the WEitec Hi-con coilovers are rated at (red srings rear and yellow fronts) but its got standard rear and front ARB`s

I keep thinking harder front springs and softer rears with a bigger rear ARB but I cant believe there`s no general concensus (that I can find repeating itself across the web)

Its on T1R`s and the last two outings have been at Bedford on the GT circuit which is a bl**dy fast 3.8 mile circuit that tests hi speed, hi speed and slow speed cornering. Hi speed corners are manageable and its competitive but on the slower ones its slow to exit and put its power down.

Its really pi**ing me off in fact as I normally work through a solution with experience and a bit of common knowledge from those who`ve been there before.

In my view the best way is to make the rear independent so mulling over whether I could adapt a torsion bar rear suspension to make it a bit more independent as the OEM rear beam is a mahoosive arb anyway when you think about it.

Alternatively you could make the rear beam flex less by boxing in part of it.

 

There was a general consensus in the slick 50 paddock, I have been lead to believe.
Stiff rear, soft front.
I haven't changed that fundamental set-up on my race car and it works well.

If you stiffen the front spring rates, it will try to wash wide. If you let weight transfer across the front axle (by using softer springs), it will help bite and grip.

I have been around FWD race cars all my life, and they have always been absolutely solid on the rear, and relatively soft on the front. Although, I am sure that starts to change when you develop the chassis to touring car spec with custom geometry.

Have a look at this video. It is interesting to see the car swap from over-to-understeer

[YOUTUBE]nV1ccPmVqyk[/YOUTUBE]

The car seems to be set-up to oversteer on entry, to help turn-in I guess.
Then understeers through the corner. That front left tyre must get hammered! But then they are restricted on set up.

 

This one is the same:

[YOUTUBE]mnb-zK4Gsow[/YOUTUBE]


Nice to see the brakes being tapped to get the pads back on the discs after hitting the kerbs.

 

You cannot compare a 500kg (or what ever it is) west field to a 800kg FD golf on the same tyres, to much difference going on! There is a lot of info suggested on this thread to try, see how you get next time with some testing.

 

Understood entirely so I was surprised to see that front pressures were suggested as to be so high

Will definitely do some `tweaks` other than tyre pressures rather than hooning about next time.

Will also research 'slick 50' which I assume was a one make golf championship or series based on cars of that era

Cheers

 

Bedford

I havent inserted the photos as I dont know if copyright is an issue.

Slow tight and understeering like mad

Flat out high speed bend

Medium speed corner and understeering like a b*st*rd all the way

 

Some more for the mix ... I`m basically in line with `sam` but with a `twist`from personal experience.

Have you changed / tested / monitored your tyre pressures before & after sessions ... comparing cold to hot figures and the resulting `feel` ... especially the rear end behaviour ?

With your set up and road tyres you need to run the rear pressures much higher ... 40# COLD, to dial the back end out. If this appears rather drastic then just try it ... increase the pressures gradually, work your way up there. I used to start from cold ... do do a session ... record the hot pressure ... let the tyre cool back ... then increase again.

I have not run the T1-R but my experience of other Toyo road tyres tells me that the sidewall is too soft, even for the road ... for me. If that is the case with the T1-R then that may be much of your issue.

Fronts could stay standard at ~ 24 / 26 COLD but with the ABF being a little heavier and standard ARB maybe a few # higher. How is the front end under heavy braking ?

I have always liked Yokohama`s and with a fast road set up initially used the 520 but then moved to the `worlds apart` AO32R ...

Geometry settings were always 1` to 1.5` hegative camber with 0` toe.

HTH`s ...

 

Hi JamesA

Thanks for your input.

I think the issue is that I am so used to RWD cars that this is a learning curve but I still cannot get over the huge amount of understeer

I was with friends with Clio 172`s (one was 190bhp) and they had understeer but still turned in better on a tighter line even with their wheels in the air.

I run the car at 26 psi cold on the road (this may be too low)

At the first track day I had 0.5 to 1 degree camber and 0 toe and the tyres went up to about 30 hot all around so I dropped them to 26 hot all around. I noticed beading on fronts and rears at the end of the day but they were nearly new tyres so I expected a bit of heat but there was wear outside the tread edge on the offside front suggesting the tyre was rolling in a bit but I assumed a bit more camber would cure this.

At the second track day it had 1.5 degrees camber and 5 minutes toe out (to help turn in) and I had the tyres at 27 cold. The fronts went to 32 hot and 29 hot at the rear so I dropped the fronts to 27 hot and left the rears as I wanted them to be a bit more loose.

On track you could feel the rear moving a touch which I hoped would allow the car to swing and reduce the understeer a bit but the difference wasnt particularly noticeable however the wear on both tyres is even and it doesnt roll off past the tread on the front offside anymore but there was a lack of beading on the fronts and the rears had beading only on the outer edges so I assumed they might be a tad too hard

The car is absolutely stable when coming into a corner and the brakes are very very good (having tested them many times with full on panic stops from 120mph to a standstill) and it pulls up straight without issue with the rears just locking as you come to a standstill.

I also tried trail braking and found that it helped a little but I have also found that the car also benefits from a dab of brake to settle it just before medium fast corners.

I am going to get it corner weighted soon to see if that dials it out a little.

So with the Yoko`s what is your experience? Is it that they are stiffer so tuck under less and obviously grippier but is it still all down to the front outside tyre in a corner ie: massive weight transfer? What suspension are you running and what spring rates?



Also I need a track that has lots of right handers to even up the tyre wear

 

My comments refer to the time when the spec was:

- Koni Sport (fast road, non coil over) kit with top adjustable front & rear dampers, no idea of spring rates but `soft`
- Eibach front and rear ARB`s
- No rollcage at that time
- 1800 8v @ 140bhp
- Quaife ATB
- Uprated bushes all round and some engine mounts

Damper settings were at `max stiffness` all the time.

The Yoko 520`s were a recommendation from a `few racers` as I was running in the road class for hillclimbing & sprints. I also did the VAG Combe trackdays.

The recommendation for tyre pressures came from discussions with Yokohama Motorsport.

I see that you have been adjusting the pressures when they are hot, I don`t do that as you lose the base cold set that you started with. When you reduced your hot 32# front to hot 27# you underinflated the tyre ... hence contributing to your problem.

The rears take an age to heat up hence me running a cold 40# ... this increases their rate of rise time. (Rover 216GTI racers used to run 80# ... not sure what tyres though).

If I were you I would forget about running road tyres and get some of the track based, road legal rubber ... of which there is much experience on the forum. AO32 / 48R Yoko - Federal - Toyo 888 - Dunlop etc ... their sidewalls are much stiffer hence help to offset soft springing. They don`t stop you `rolling` over on the edges though as this is ultimately dictated by how commited you drive. Be aware that they come in various compounds and pick what suits the events that you do, not as a whole but by the duration of the sessions that you run.

Uprating your ARB`s is also (as noted by others) worth doing.

I hope that this makes some sense , more than happy to chat if you dare

The Mk1 will never be a Clio, it will still understeer with an ATB ... just have to be a clever driver ... which I am not !

 

As above, tyre pressures sound a bit low, as a general rule. There are a lot of variables, but I'd go up around 30 hot and experiment from there. I'd also think you want a bit more negative camber on that setup, unless you're running modified geometry to give you more castor.

As already said, stiffer rear springs are the way to go - or at least a stiffer ARB. I'd expect the car to lift the inside rear wheel. I find that helps get the car to turn, although you don't want to overdo it on fast bends, as it makes the car a little less stable. For a pure track car, on smooth tracks, I'd think you want around 300lb front springs, and 500lb rears. A stiffer front will give you more understeer.

However, a 300/500 setup is almost undriveable on a bumpy track like the Nurburgring, or on the public road. I change rear springs at some track days before I go out, as I can't drive to the track on the 500 lb rears, and still walk when I get there.


If you do it by adding stiffer ARBs, you also have the option of detaching the ends in the wet, depending on the ARB design, to give you a softer wet setup. That way you might leave the springs a bit softer.

 

Whilst I wouldn't want to disagree with anyone (as everybody has their own tried and tested way to set a car up), I wouldn't say you need to put lots of pressure in the rear.

A good slap of front camber will help, as mentioned. And the spring rates Mike just said sound good. Along with the biggest rear ARB you can get.

You should be able to get heat into the rear tyres after a couple of laps - they rear feel hot enough after 1.5 laps racing and a warm-up lap.

I am always tempted to put road tyres back on my car for trackdays, just because you don't have to be driving at ten-tenths to feel the car moving around.

The Slick 50 Championship (search 'slick 50' on Club Gti) ran with Yoko A549's (Well my car came with a load) in 14 inch. When 3/4 worn out, they are great on track - taking a real punishment. Now replaced with Parada Spec 2 - I think.

I would also say that it could come down to driving style (not suggesting you are to blame, you sound pretty experienced from your list of cars ). Carrying too much into the corner will obviously give the front tyres alot of work. And I think it is always going to be hard to get away from understeer out of the corner when you have your foot nailed.

Although, I am certain my lap times would be better if I wasn't as precious about my outside front tyre! It looks like I am driving at 8-tenths in retrospect I need to use 6500rpm++ more, then it really starts shifting.

[YOUTUBE]q9U38OwpFqk[/YOUTUBE]

 

Thanks James I appreciate the input but I am surprised re your comments on tyre pressures as the heat inflates the air inside the tyre and adds internal pressure so I assume a hot reading is an accurate indication of the internal tyre pressure in my view.

As the air cools it will lose pressure so only when cold the tyre will be underinflated. I kept them down to ensure even tread contact with the track surface as the higher the pressure the more round the tyre is as too high will wear out the tyre centre and conversely too low will wear out the edges - both scenarios reduce contact.

I still think a much bigger front ARB is key as is more camber and can see that a MUCH larger rear ARB will counter the front end lean.

Always happy to chat - I will have to experiment

I have driven many cars on track and have had instruction on occasion and am told that I am a very smooth driver and have been used to hunting down Porsche GT`s and M3`s etc in my little 944T so am used to very high speed late braking (which incidentally the Golf is fantastic at as it is so light) - no absurd flinging it in and riding the really rough bits for me but even with a little dab to pre-settle it it wont quite carry on the initial turn in which is frustrating having eased and not braked in some corners whereas others are braking it still wants to run too wide.

Its not slow in the corners I just want to straighten them a bit as any advantage is lost in levelling up and getting the power down on the lighter wheel.

 

27 cold = 32 hot ... 27 hot when cold = ?

Fair enough ... experiment away and good luck

 

Just to echo something jamesa said, for tight twisty short stuff like Curby, I've experimented a lot with higher rear pressures, and it does seem to help the car turn in - well in reality the back is sliding more. I also found that with only 12-14 PSI in the rear, it gave a similar effect, but I think this is less safe as it's really just the tyre flexing more. (on R888s in both cases)

On longer faster circuits, I run around 25psi all round, but I think this needs more experimentation to find the right setting. I'm generally running softer rear springs on these as well, as it's just track day fun, rather than racing.

 

I have a 22mm front ARB or you could just run over 450lb/in front springs and keep the factory front bar in place. Just so you know what I mean by a BIG rear arb, I run 2x rear bars together. A 28mm bar along with this:





It's my 38mm torsion bar that I had made. It makes the car turn in and keep it's line very well. Also by keeping the rear spring rate reasonable, it's such a smooth drive that it doesn't even feel like a track car when cruising!

Without it, the car pushes on tight corners but with it, the rears work harder taking some of the work away from the front tyres.

Gurds