Grip Roll
 

Can anyone offer any additional advice on how to reduce grip roll on high traction surfaces? I am currently driving a B44.1 and am suffering from a lot of grip roll.....

As a newcomer to the game I have raced three times outdoors, once at Stotfold, once at Hinckley and once at Silverstone. So twice on astro and once on grass.

The first time was at Stotfold and simply cutting off the two outside rows of spikes on the fronts pretty much cured the problem there so the grip must be a bit lower than the other two.

Then I went to Hinckley and found that it was still grip rolling every time. I then proceded to cut of a row of spikes off of the outside and inside of the rears as well as the inside row on the fronts. I was then advised to change the springs to blues (front) and silvers (rear) to stiffen it up a bit, and also to add some weight. I added 60g of stick on weights to the central battery stay beneath the driveshaft and this again seemed to help. It didnt eliminate it but it raised the breaking point so I could go a little faster before it rolled.

I then raced at Silverstone on Tuesday and the problem was there in abundance again. Everybody was saying how much grip there was so I wasnt alone, but when I observed the other 4wd cars they seemed a lot more planted.

I know that I am not as good as the more experienced guys, so that will make a difference. But even allowing for that, I was still grip rolling on less technical areas such as the sweeping bends into and out of the straight where the other cars were hammering it through these bends significantly quicker than I could before I was losing it and grip rolling.

So Im scratching my head a little now. There has been massive improvement from where I started, of that there is no doubt. But its still not quite there in terms of keeping it planted and reducing the grip roll as much as is physically possible.

So my set up is :
FRONT
20mm ride height
Blue Springs
40wt oil
Worn yellow minispikes (2 outer rows cut off, 1 inner row cut off)
2 x 5g weight added (one either side of servo)

REAR
20mm ride height
Silver Springs
30wt oil
Worn yellow minispikes (1 inner and 1 outer row cut off)
60g weight added under rear driveshaft

All of the other settings are untouched since I built the car to the kit manual instructions.

I know this is something that cant be eliminated completely but having watched the other 4wd cars closely on Tuesday night I did observe that they were able to carry much much more speed into a bend without it rolling. At the moment I feel like I am driving on the edge as several times tuesday night I had it on two wheels round a bend, and many more times it broke free and ended up on its roof.

If anyone has had similar experiences and managed to cure it, or if you drive the same car and manage to keep it glued to the track then any advice would be much appreciated!

Many Thanks! :thumbsup:

Limiting droop can help cure grip roll but at the expense of bump handling. Try adding 1-2 1mm spacers underneath the piston and see if that improves matters.

Also, try a front roll bar if you've got one.

HTH

Can you explain how you mean please? A couple of months ago I knew zero on setting up a car so am having to learn fast, but dont know quite what you mean by this? Thanks!

If you picture the shock shaft and the piston running inside the shock body, you would put some spacers on the shaft under the piston (below the E clip) and inside the body so that you are limiting down travel. This helps limit roll at the expense of bump handling (as you don't have as much downtravel/droop).

grip roll
 

We had the same problems with our B44 & BJ4 cars in the past.

One thing we tried was to remove the inside & outside row of spikes & also use a harder foam in the front, we also nearly always ran rear anti roll & hard front springs.

If in extreme cases Stotfold (astro) we restorted to running (2wd) Slim mini spikes on the front.

If I can answer on his behalf, you open up the shocks and put the spacers on the shaft under the piston, this will limit the downtravel. AE sell packs of 30thou spacers for that purpose.

Personally speaing, from looking at your setup I wonder whether you are running the car too low. The geometry is designed around a certain ride height (more like 23/24mm), and by dropping it down low you are making the roll centre quite a bit lower which increases the likelihood of grip roll, you are also more likely to bottom the suspension out, which will cause a sudden roll.

You already know about trimming spikes, so aside from that I would suggest decreasing your steering lock a little, and just advise you to try and be as gentle in your steering movements as you can be. Try and keep the car running straight unless you absolutely have to be steering, use the brakes to slow the car down rather than scrubbing the speed off with steering input.

Thanks Guys, some good ideas to try out (not all at once though! :p)

Sosidge, I was surprised by your comment ride height. I would have thought a lower ride height and lower centre of gravity would have helped reduce the grip roll? You almost certainly know more than me though so I will certainly give it a try! :thumbsup:

I am already having to be quite heavy on the brakes as if I try to scrub speed off by sliding it just goes over. When I was watching the other 4wd they were entering the corner at the end of the straight faster and were sliding a little in the corners where my car would just bite and roll if I tried to do that.

Are you running the kit locations for shocks and camber links?

I had a similar problem first time out at Silverstone and was advised to use softer oil in my shocks (as well as all the spike trimming). I had 45wt in the front and changing to 35wt helped no end.

Yes I am, would you advise changing these?

I will try this next time I am at Silverstone and see how I get on. :thumbsup:

You could try moving the rear shocks to the outer hole on the wishbone to see if this helps.

The kit positions are normally pretty good TBH.

Would you only change them to the outside on the rear and not the front?

Really? Softer oil? How does that work?

If you are not on the outside hole on the wishbone at the front, make that your first change..! I thought kit setting was outer on the front wishbone :confused:

Im not sure as I am at work at the mo and cant be 100% certain from memory, but I thought it was on the inner. :eh?:

Just read it again, Im not paying attention..... :blush:

On the wishbone it is on the outer, I was thinking of the shock tower. Would moving it to the outer on the tower make a difference by standing the shocks a little more vertical?

I don't really know tbh, that's just what I was advised and it seemed to work for me.

I assume it has something to do with the shocks absorbing more of the shifting weight as the car turns.

I could be wrong as I made quite a few other changes to the car before I went back again, they may have made the difference.

Is the car staying flat then flipping suddenly or is the car rolling into the full suspension travel and then flipping? Both scenarios require different solutions

Try this setup....
Silver roll bar fromt and rear
40wt oil, no.2 piston in front, silver or blue spring
35wt oil no.1 piston in rear, silver spring
22/23mm ride height
Get some weight in the back if you dont have any, the centre weight 87g for the b44.1 is perfect, for lipos.

Trim your rear wing down a bit.
Start with minipins, and a firm foam. You might find that the thinner carcass minispike tyre is collapsing.
I would cut the inside and outside row off the front tyres. If the grip roll is still there, cut another outside row off both front and rear tyres.

Hope this helps.
Mark

Latest setups on the B44.1's use the silver roll bars both front and back. That'll help no end, all the other things that have been mentioned are also all good advice!

Use bigger/harder inserts in the tyres, I've been using the KWF foams that P-Dub racing sell, much bigger than the standard schumacher foams, so fill the tyres more making them harder and the side walls more stable and grip more consistent.

Failing that...I know some people have used cut staggers on the front of their 4wd's too.

Anyone got a front roll bar kit they want to sell me?

before you can cure grip roll you need to know how and why it happens.

Im not 100% sure to be honest. Visibly it appears to stay flat then flip suddenly. But having seen a slight improvement when I changed the springs from silver/green to blue/silver then this would lean towards supporting the theory of the car rolling into the full travel position wouldnt it?

Thanks Mark, thats excellent. There are some points in there that I would never have thought of, I will try this set up for definate. :thumbsup:

Thanks very much, I would never had considered bigger/firmer foams. I will get some ordered tonight and give them a whirl as part of Marks set up(above).

And there lies my problem, as a novice I dont have that kind of experience to know why it is happening!?

Hence being here picking the brains of some of RC racings finest minds!! :thumbsup:

grip roll happens when the side of the front tire digs and causes the car to flip (sidebite) the only way to stop this is to remove side bite by laying shocks down on the tower out on the lower arm flatterning front top link softer spring thinner shock oil cutting spikes off tires front anti roll bars less steering lock more camber more caster we are tallking about making the car more progressive as you turn in to first part of the corner.

stu

Or just run 2wd staggered ribs up front, works for me but not saying it's right :blush:

like i said sidebite. dibble your avantar still looks the nuts.

stu

Thanks Stu, that's a lot of advice! Some of it I understood but the bits I didn't understand fully I have left above. If you are able to translate it into an idiots guide that would be greatly appreciated! :thumbsup:

yep, can't bring myself to change it!

I'd look at your tyres before messing about with the car setup to much, Silverstone is too bumpy to comprimise the setup too much to deal with grip roll. I've found that if you use yellow minispikes at Stotfold when they start to get too worn and go off they are then about ideal for Silverstone, even the stagger ribs on my 2wd have done a couple of runs at moto arena to take the edge off them.

What would you suggest then mate specifically for Silverstone?

Try slackening the front diff off slightly.

hi skye

ok sidebite happens on intial turn in, when the shocks are stood up more ie further out on tower inner on the lower arm the car will react faster to steering input so as you turn the car will pitch on to the outside wheel much faster and more sudden and make the front reaction less progressive (sharper).

softer spring and softer shock oil gives a simular effect to laying the shocks but doing it this way you will not compromise the direction change or the way the car rides the jumps and high frequency bumps as much you can usaly leave the shock locations the same.

again the more angled or shorter the top link is the quicker the car will change direction though the roll centers so if you lengthen or level out the front top link again you will make the car more progressive on initial turn in

again sidebite is generated fom the side wall or edge spikes of the tire if you use more camber as the car leans will use more of the top of the tire rather the edge spikes it will tend to give a smoother feel. using more camber the car will tend to have less forward traction as the tire is leaning over more to start with.

caster is very simular to the effects of camber without as much compromise on forward traction with more caster when you turn the front tires are lent over more as if the car has more camber. caster and camber need to work in conjunction with each other ie less caster less camber more caster more camber.

a lot of drivers think stiffing the front of the car up will stop grip roll this will make it worse yes it will make the car have less steering but it will also make the car react faster on inital turn in which is where grip roll is generated from.


i agree with trimming tires to keep a ballance without compromise to bump handling, all the factors ive mentioned have pros and cons you will need to have a play and see what works for you.

stu

Yellow minispikes are fine, it's just they need to be at least half worn out and with the outer row of spikes cut off front and rear, these will then work untill they are pretty much bald on a 4wd.
A set of tyres that have done 2 -3 meetings at Stotfold are about right.
Oh yes the other thing worth trying is adding weight towards the rear of the car, this seems to slow the reactions of the car down which helps

I'm not experienced but I run on a super high grip track so grip roll on 4wd is an issue.
I didn't find it useful to run too stiff oil/springs as it could harm long sweeper and overall stability so I keep a relatively soft shocks but outside on wishbones, inside on tower. Then low ride height, as low as possible to still clear the jumps. Then a bit more camber overall, shorter rear link and it greatly reduce grip roll without compromising too much the rest.

In grip roll situation the first thing i'd try is a bit more Camber after trimming spikes... but never any more than 2 deg negative on buggys.

Rather than just snipping spikes of.... using a dremel to slick smooth off the area trimmed helps a lot too.

something else worth trying is toe in on front wheels as this will reduce initial turn in and help stop the outside tyre digging in under sudden load

ride height is critical to how the weight moves and induces roll in corners.

I always start with front wishbones horiziontal and rear driveshafts horizontal under race weight conditions with 2WD cars.

:thumbsup:

Thanks for all the replies! :thumbsup:

I think its very much going to be trial and error to see which suggestions work but at least I have plenty of food for thought now!

Thanks for the info regarding Silverstone Chalkie, always good to get information specific to a track. When I get a set of tyres 'in the zone' for Silverstone I will take them off and keep them for Silverstone only.