Excessive grip roll

[Simion Wabs]

All,
this is probably a well covered topic, but week in week out as the indoor carpet track grip improves over the course of the night so does the frequency of grip roll occurs. Now just a couple of basic questions...

Will stiffer/softer front springs reduce grip roll?
Will stiffer/softer rear pod springs reduce grip roll?
Will more weight bias towards front of car reduce grip roll?
Will having a torsional bar across the wishbones reduce grip roll?

I have super glued the tyre edges (Med Japs pinks) and reduced the EPA for steering and also slowed the DR of the servo. Super glueing the tyres brings on masses of understeer but as the super glue fades grip roll increases. The front tyres are trued to have approx 3-4mm of tread.

Rear pod droop is approx 1-2mm. I seem to get it set up well one week then the track changes and the problems reoccur.

Any help suggestions would be appreciated

Si

[Chequered Flag Racing]

are you using foam tyre additive?

is the chassis nose down as you look from the side?

[Simion Wabs]

CFR,
chassis is pretty flat (horizontal with floor) ride height about 4mm (not got car with me at the moment so thats a guess). With excessive understeer I have used additive in the past but not when suffering with grip roll.
Grip roll occurs when not using additive.
Could it be down to weight distribution as the car does it more so when turning left??
Motor mounted on RHS motor pod looking at car from the rear... got me thinking, can I use hard spring on one side of the car and soft on the other??

Si

[gaza121]

Will stiffer/softer front springs reduce grip roll?
The stiffer the front spring the less grip you get and less grip roll

Will stiffer/softer rear pod springs reduce grip roll?
I have always used the kit MED springs, its all about tyres and compunds try mardave hard fronts and V53 med/sort on the rears (med is best!)

Will more weight bias towards front of car reduce grip roll?
more weight on the front would increase grip roll, due to the motor being mounted to one side try to balance the weight by moving speedo/reciever slightly

Will having a torsional bar across the wishbones reduce grip roll?
No this will give give more consistent handling as the wishbones wont flex

If you get your set-up spot on you should not need grip additive on the fronts at all

[KJR]

I'm not sure what rating pink med fronts are but if they are too hard a compound they could bite more and make the car grip roll. I normally run 46 or 48 fronts on my car and if the grip is really up then I will run 44 shore fronts. Make sure the edges of the tyre have been rounded off as well so there is not an edge to bite into the carpet and apply superglue to the outside edge. You should only have to do this once.

I normally run pink med rears although recently discovered gecko 30 and 35 shore rears which are excellent. I run the tyres at 48mm starting on the rear and 46mm starting on the front although most of my tyres are a lot smaller than this as they have been run a lot. I've never needed to use addative.

A harder spring will make the car understeer but it will also make the inital bite stronger, the car will feel twitchy and this can cause grip roll.

Make sure that your front steering blocks move easily over the kingpin and will drop on their own weight. I normally polish the kingpins to help with this. If the pin is bent or the steering block catches then this can also cause the car to grip roll.

Finally is how you drive into the corner. If you approach at high speed and then turn in aggresively the car will go over. If the grip/bite is high you need to try and smooth out your corner entry as much as possible to stop it falling over.

[mcjjordan]

i had this a few times i found i had to align the steering so no toe in or toe out and true tyres down alot on the front also lower the whole thing down to just above 2mm ground clearance then even now depending on which track limit the steering with the controller depending on which you use .....
i too run jap med on front and pinks on rear only ever needed addative on rears when tracks cold.
also found that i was 'cocking' front inside wheel on fast corners which sometimes led to a roll so fitted hard front springs -after experimenting with washers on king pins to stiffen front up suspension and also foam pads under rear plate to try to limit amound of roll.



hope this helps if only a little

[maky]

Turning down servo speed will help aswell will stop it turning in as hard.

Stiffer spring in theory takes away front grip but due to beinging stiffer it has no give. it will turn in harder and prob make it worse. A softer spring gives a little.

Weight over front end helps. We ran the heavy plastic front bumper it adds around 30g as far forward as u can get it.

46 48 or 50s front and 54ps rear is what most people use on our track

I usually run rear Med springs with a front Med spring in the middle of it in the rear. Few people been running it now with good results

[Chequered Flag Racing]

@ Simion

have you got approx 2mm of washers/spacers under the front of the wishbone to produce some castor for the king pin?

[Simion Wabs]

@ CFR,

to confirm I have 2-3 washers under both wishbones to add castor. Would more or less castor angle reduce grip roll? I could try less washers?

Si

[maky]

Putting couple mm under the pivot ball on the rear helps with grip roll aswell

[Simion Wabs]

Thanks to all for the advice on this grip roll subject. I replaced the front springs with harder springs and this really improved the handling of the car and I no longer suffer with grip roll :-). However at the same time I also had to change the diff spur gear as i'd inadvertantly stripped the existing gear during my last race. This has resulted in an even higher gear ratio than previous but I am now experiencing a "hopping" motion during initial accelleration? Now is this due to the ridculously high gear ratio 16/72=4.5 from previous 16/80=5 or is it due to the reduced /changed weight transfer due to the harder front springs? Or is it just the tyres losing grip/spinning up due to low traction from cold? I can say the "hopping" effect happened at the end of the race as well as off the line so maybe nothing to do with cold tyres.
Do I need to stiffen the rear springs now to compensate for the stiffer front springs? Or should i just put traction additive on the rears to improve grip?

Any comments welcomed

[teamorsum96]

i would run hard springs up front with jap pinks tires and medium springs on rear with pink mediums tires on rear
we found that to work well :thumbsup:

[Chequered Flag Racing]

but I am now experiencing a "hopping" motion during initial accelleration? Now is this due to the ridculously high gear ratio 16/72=4.5 from previous 16/80=5

Sound's like cogging, which would be unsensored motor & esc

Are you running sensored or unsensord motor & esc?

Post esc & motor type

What's the diameter of your foams?

[stegger]

Grip roll normally on a mardave is due to the front outside tyre wall collapsing. What i used to do and you see this on the 1/12th scale cars and at the petit race this year was to superglue the side wall to stiffen it up ;) This also takes the grip off of the side wall ;)

[teamorsum96]

Grip roll normally on a mardave is due to the front outside tyre wall collapsing. What i used to do and you see this on the 1/12th scale cars and at the petit race this year was to superglue the side wall to stiffen it up ;) This also takes the grip off of the side wall ;)

+1 :)

[Chippy96]

It would help also if you "shaved up" your tyres before you use them,I run Shore 48 on the front and true them to 48mm and put a small radius on the outside edge.Some competitors go even thinner than this,I guess its what works for you.If you look at Chris`s Mardave website and look about generally you will see wheel adverts and different pictures of different models he sells and some of the tyres resemble rubber bands!!cheers Pete Chapman.

[mcjjordan]

Sound's like cogging, which would be unsensored motor & esc

Are you running sensored or unsensord motor & esc?

Post esc & motor type

What's the diameter of your foams?



check your axle hasnt bent by rolling on a sheet of glass