Rear tires heating up...
 

Rear tires heating up.

Indoor. 80x36 feet Ozite. Medium grip.

ARC chassis. 5.5T motor. Traction compound full rear and 90% front. Intermediate level driver.

If driving the car like I'm borrowing someone's car to test and don't want to hit anything and I tip toe around the track, the car turns and rotates great, super fast acceleration and straight speed, good brakes and no traction roll. Somewhat competitive car.

If I'm pushing the car harder, rear end is lose like crazy and after a 5 minute run, the rear tires are like 15-20F degrees hotter than the front.

I'm thinking too much front grip and not enough rear. What would you guys try and in what order would you try them? Things like roll centres (rear higher?), sway bars (harder front softer rear?), rear toe in (more?), camber (leave at 1.5?), saucing technique (longer rear and less front?), springs (softer rear?), shock oil (no clue), shock angle (rear more angled?), etc.

Or maybe I'm not smooth on the throttle and work on that? Play with throttle exponential?

Thanks for any insights,

Ivan

There are probably some gurus out there far more guru than me, however I downloaded the Hagberg app on my iPhone, it's a well designed up with plenty of info and I just played around with it and learnt a lot.

After checking your ride height

Start with droop, check that front and back, sounds like you're not getting enough weight distribution to the back of the car, the heat is likely coming as a result of the sliding around.

Weight distribution is really important and plays a big factor in these things.
That comes from droop and shock settings

Whats your secret?I'm running a pan car at a local parking lot and I can't get the rears to warm up.Any way,I used to race a Yoke.I'm no pro but I would run a 0 degree rear toe and work your way up from that.You didn't say where it's at now but I would say you've got to much friction going on.

Try posting your complete setup here
http://www.rctech.net/forum/electric...10-2015-a.html.
You will get some help there. Kody Knutson runs mod on carpet/asphalt and can get you sorted.

Is the 'loose' part of the handling when on or off power, is it the same all the way through the run, or fine at first then gets worse etc?

Have you tried full rear and 50% front yet?

For some reason I can't download that app in Canada. :confused:

Increasing front droop for more rear weight transfer is on the list to try.

It's not my secret it's my problem!

Unfortunately I've still got the original first generation R10. I'm looking for more what setup changes I could make to cure a specific problem so I thought I'd ask the masses. However, the R10 2016 whenever it comes out maybe my next car. :)

Sorry i didn't give that info. It's perfect off power, turns and rotates well and is planted and not spinning out but on power out of the corner is the problem. Smooth acceleration works but that's so hard to do and it's not as fast!

On the list to try. I'm still thinking there's needs to be more rear weight transfer but I need to do it without compromising steering!

Thanks for everyone's input. It is much appreciated and looking for more insights to my dilemma.

Ivan

I,m having the same problem with jaco blues the rear are about 15 deg warmer and 2 min in and the rear becomes unstable . No problem with sorex 28 they do warm up the rear but it doesn't,t skip out

Try adding more droop to the front. Loose on power usually means not enough weight transfer to the rear. Adding droop to the front will allow this. But do .5 mm amounts at a time. Also raising the front ride hieght by .5mm could help as well.

But... If you tires are heating up like that it could come from two reasons. 1. The rear is loose and you are spinning causing exces heat build up and trying the things above could help. Or 2. There is already too much weight transfer to the rear causing the heat. In which none of the tuning aids listed above will help. In fact the opposite would be needed.

The issue could be coming from a third sometimes over looked problem. Too much rearward weight transfer combined with a rear suspension that is too soft causing the chassis to bottom out on hard acceleration. When this happens the car becomes extremely loose as chassis now supports the weight, not the tires. The tires then spin, heat up, and get greasy causing the issue to get worse as the race progresses.

Little can be deduced from the information you have provided. :(

What's your rear toe? Could be as simple as that. What's your front and rear camber?

You need to measure and give us your setup information.

What I did to help cure such an issue.

1 - More rear toe -3.0 / front 0.5 degree
2 - Roll centers - Raised front inner link / lowered rear inner link.
3 - -1.5 front / -2.0 rear camber

Whilst you're giving us the info ;);

What springs and oil are you using, what gear diff oil and droop settings

Too loose front belt
 

I have experienced similar behavior. After elaborating with angles etc. without any significant improvement, it turned out the front belt was too loose, so it started skipping when full trottle out of the corner was applied. Changing the belt as the teeth were eaten by the skipping and tightening it properly resolved the issue.

Funny cause those are the tires I’m using. Actually I’m the only one using these tires at the club as they are old tires (2-5 years old and free) so why not! Since it’s open tires at my club, everyone else is using Sorex 28’s or equivalent. No big deal to me. I’d rather have a car that drives well and I’m happy.

Droop. On the list.

Thanks for all the scenarios. Never thought of the 3rd scenario but makes sense. I don’t think I have any rear chassis gunk but the front bottom edge of the bumper has some gunk after a run or 2. I do clean that up with brake cleaner.

Sorry. I thought giving less info would be better. My Bad.

3 degrees rear toe in, maybe 0.5-1 degree front toe out? Front lowest roll center possible, rear not as low with shimmed up from the bulkheads 1 mm. Front camber 1.5 and rear 2.0. Same in my 17.5 blinky car. That car actually works pretty good except my complaint there is it doesn’t rotate into the corner as good for some reason against an Awesomatix but I can deal with that for now. On a side note, the got to test the faster driver's Awesomatix at a recent big race event with a 44 car field in 17.5 blinky. It was open tires too and I was about 0.5 seconds faster in his car in 5 practice laps than I was in my car for the entire weekend. I did come in 4th with my Jaco Blues so that's not bad. :D

I was thinking about trying 3.5 rear toe in next.

lol. Springs are ARC green ones so that translates to 0.28kgf/mm. They are the second softest springs. I think oil is associated 30. Haven't changed them in 3 years cause they don't leak.

Sad to say but I actually don't know exactly. As I didn't build them when I bought the 2 cars used (one for 17.5 blinky and one for mod) and it wasn't written down. Front is either 2.5 or 1.0 million is rear is either 1000 or 2000. But if I had to guess my blinky would be 2.5 front and 1000 rear and mod would be 1.0 front and 2000 rear. They don't leak either so I have never changed them.

I don’t think that’s happening.

But you bring up a good point of discussion. Every since I started driving Touring Cars, I was told to have the front belt slightly tigher than the rear. Do the push down test on the belt to check. No problem in my 17.5 blinky car as I havent’ changed the front or rear belts or any drive train parts for 3 years at least. But in my 5.5T mod car, I’ve stripped the center pulley and rear belt 2 times already in the middle of a run making essentially it drive like a front wheel drive car. I’ve tightened the rear belt even more not after the 2nd time it stripped and it’s on a bit tighter than the front. Maybe that’s causing a problem? I don’t know. So should I tighten the front even more to compensate the extra power in the rear?

Thanks for all the feedback,

Ivan

Ok I think you found your own problem. Your tires are old. Get new ones. Tires that old may look like they are in good shape wear wise, but they are actually pretty messed up. I had tires that were actually fairly new, and looked to be in great shape. But my car was violently traction rolling no matter what I did. I got a whole new car, used old electronics and tires. First lap, violent reaction roll. Fought it all day. Then another driver let me borrow a set of his tires. Instant change. Car became very drivable.

Try new tires

Alright.

First thing - Just because it doesn't leak doesn't mean you don't have to change the oil. At club level you should be looking at changing the oil 1-2 times a month. It's important to freshen up the oils to maintain consistency.

Gear diff oil - 7k-10k
Shock oil - 450 oil
Roll centers - 1.0 mm front inner link and (1.0 mm rear inner link 0.5 mm on outer hub)
These shim settings should reduce the amount of camber gain on the front and increase the amount of camber gain on the rear. I would even go lower on the rear and try no shims on the rear inner link. Leave the outer hub shim as it is.
Springs. You have one of two options
1) Go one spring rate harder on the front and leave the rear.
2) Keep the same springs, but move one hole out on the front and or one hole in on the rear.

What are your shock tower positions?

Droop - 2.0mm front 2.5 mm rear

New Tires!!!!!!

Also type of wheel plays a big role in how the car is planted. A multi-spoke rim will flex more and make the car more forgiving. I've found it really plants the car down on the track. Perfect for low-medium grip situations. A dish rim is stiff and will make the car more reactive and I would say is ideal for medium-high grip situations.

The hot ticket at my track is 5 spoke wheel, Sweep Blue insert, and Sorex 28's.