Speed Runners, Diff Oil..??

[BashingBrian]

Wasn't sure where to post this as I wanted maximum coverage for answers..?

Question..
Limitless or Infraction running a spool what weight diff oil are you using F & R..??

Also on 6s vs 8s do you run thicker/thinner oils..??

I'm going to tag a few people here to get their attention and help out with this one..? @phildogg @Mr.Duke @LibertyMKiii @jondilly1974
Thx in advance..??

Edit: Tagged a couple more people in... @GMballistic @Turbobrick

 

[Mr.Duke]

I’m running 10k front and rear and will probably keep it that way as long as the car continues to run/track straight and drama free during full throttle passes.
I’m still tweaking details and only in the high 1-teens so that may change as I work my way up into the 120’s - 130’s

 

[phildogg]

I haven't touched mine. completely stock oils.

 

[jondilly1974]

Wow I am surprised by some answers here. I go way thicker. In my Typhon 3S I have been running 100k f/r but just upped to 500k.

In my Typhon 6S I’m running 100k f/r as well but haven’t ran it enough to settle on anything. Would probably go 500k as well on next rebuild.

Reason being that I don’t actually want diff action in most cases. I really want locked diffs all around. Having one wheel diff out means blown tires. And I don’t really need to turn much either so understeer is fine.

 

[LibertyMKiii]

I don't know that I have enough runs in to give valid input.
For the Typhon I was running silly puddy…. so basically locked. It ran straight as an arrow on GRP Tires. On BSR purple foams the rear was fish tailing very badly. (likely only needed more rear downforce as the front was doing great)
I have since moved the rear to 500k and moved back to GRP rubber tires. Still trying to figure this out myself. I know the long wheelbase of the Limitless is a bit more forgiving than the short wheelbase Typhon

 

[BashingBrian]

Well so far those answers were not what I expected..?
Especially @phildogg 's stock 10k..!! on cars that you run into the 150's..!! No change with 8s or 6s either..??

I was thinking at first 60k F & R then thought I might be better off with 100k, but now I'm total clueless..????

Tyre wise, I'll be mainly running GRP's, I did buy some Contact 35 foams to maybe tryout..

 

[bicketybam]

Under what scenario would your front or rear diffs be diffing out during a speed run?

 

[jondilly1974]

Well so far those answers were not what I expected..?
Especially @phildogg 's stock 10k..!! on cars that you run into the 150's..!! No change with 8s or 6s either..??

I was thinking at first 60k F & R then thought I might be better off with 100k, but now I'm total clueless..????

Tyre wise, I'll be mainly running GRP's, I did buy some Contact 35 foams to maybe tryout..

I believe Raz blew his Contacts at a rather low speed. Just a warning.

 

[LibertyMKiii]

Under what scenario would your front or rear diffs be diffing out during a speed run?

It blows my mind that in a straight line run you would want the possibility of the left or right tire to turn faster than the other side.
I suppose many roads are not perfectly flat.

Either way I think 500k or 1 Mill is ideal. This allows some wiggle room, but close to locked.
The buyer of my Unlimited project has many 1/8 scale cars doing 158-159 mph running 1 mill front and 500k rear.

 

[bicketybam]

It blows my mind that in a straight line run you would want the possibility of the left or right tire to turn faster than the other side.
I suppose many roads are not perfectly flat.

Either way I think 500k or 1 Mill is ideal. This allows some wiggle room, but close to locked.
The buyer of my Unlimited project has many 1/8 scale cars doing 158-159 mph running 1 mill front and 500k rear.

I was just asking the question. I don't speed run. But when a guy who runs well into the triple digits says he uses the stock 10k, you would think that's ok to do. Again, I was just curious how it could happen in a straight line run. I've really only seen a f/r diff out in a hard turn in dirt or when doing donuts.

 

[parcou]

@BashingBrian

Good pos/topic!!!. I have an Infraction and I research this for weeks and many PM's to find an answer. I never got the answer but enough info to put me in a direction. I run 2x 3S lipo and I like the Hoons tires better over the others....I live in the HOT delta of Memphis,TN so the asphalt can cook and it's in the 90's already running silver/white hoons.

I might not fit your post with my response. I care nothing for speed runs (like to see others show me what it can do) for me the catch and selling point that hooked me to the Infraction was the drifting ability. My runs with the Infr are in large parking lots where I can drift wide, fast...run straight and drift it again for about 2-3 house lengths of skidding....that's my rush right there...seeing those tires & letters spin on how Arrma advertised it.

Here are the recommendations I got for the style I wanted:

50/100/40 f/c/r JayTee on YT
50/200/30 f/c/r PM friend here
60/100/30 f/c/r Amain video (tech on diff fluid change)

I went with 60/100/30 f/c/r after watching a video someone posted here by a guy who really explained the science about diffs & oils and how they work together. I can't remember who posted it...20min of education and was good. Helped me to fill in the gaps of all I had read.

For drift, I like this setup because the rig pulls in the direction I want it to go since I want front power to pull out my skids. Good post and my answer will not come close to speed runs but maybe help some like me who will ask this question again If I do change and I do not plan to....only be 200w in the center since I bought it. I'm in no rush my current diff setup fits me.

 

[LibertyMKiii]

I was just asking the question. I don't speed run. But when a guy who runs well into the triple digits says he uses the stock 10k, you would think that's ok to do. Again, I was just curious how it could happen in a straight line run. I've really only seen a f/r diff out in a hard turn in dirt or when doing donuts.

I agree, and from what I have gathered things are drastically different on 1/8 cars and smaller versus the long wheelbase limitless.
My guess is that much of it depends on the road. I have been 119 with GRPs on the Typhon and it drove perfectly straight (no steering input required).
BSR foams were a different story. No changes to the car and it went off the road.

 

[bicketybam]

By the way, this was the business that I owned before we sold it in 2013. 28 acres of asphalt. There were plenty of places to set up a speed run ?

 

[Mr.Duke]

Running 10k front and rear,
I’ve never experienced a diff-out situation while running a spool even when geared slightly below 100mph doing drag launches from a standstill. Every time it would spin all 4 if it ever broke traction, which was dependent on how aggressive the throttle was applied.
It’s mechanically impossible to spin just one wheel faster than the other three when the front and rear are locked in the center with a spool. A spike in rpm on any one wheel would require a spike in rpm from one of the wheels on the opposite end of the car. You can only spin one front and one rear wheel simultaneously or all 4, never 1 or 3.

 

[BashingBrian]

So since I posted this original post I've been having a look around the internet etc trying to get more info on this diff thing, and I've come to the conclusion that I've no idea what's best for me to run..?

The more I seem to look into it the more opposite answers I get..?
And the extremes of... "oh I only run 10k" right through to "1000000K is the best" makes no sense to me..!!

One weight has to be better than the other surely, maybe driver skill plays a lot into the weight choice or must be the deciding factor..!!

In my tool box I've currently got 10k 100k 200k 500k 1000000k, I think I might just toss a coin to decide..?

 

[parcou]

So since I posted this original post I've been having a look around the internet etc trying to get more info on this diff thing, and I've come to the conclusion that I've no idea what's best for me to run..?

The more I seem to look into it the more opposite answers I get..?
And the extremes of... "oh I only run 10k" right through to "1000000K is the best" makes no sense to me..!!

One weight has to be better than the other surely, maybe driver skill plays a lot into the weight choice or must be the deciding factor..!!

In my tool box I've currently got 10k 100k 200k 500k 1000000k, I think I might just toss a coin to decide..?

Funny

My post few above I said the same in all my research....it was all over the place on answers. You are doing speed runs so it might be a bit harder for you to lock numbers.

For me since I like to drift I could stay within OEM numbers and add more or less to dial in the right feel...

Good luck but share what you did settle with on the speed runs for diffs.

 

[bpl]

Running 10k front and rear,
I’ve never experienced a diff-out situation while running a spool even when geared slightly below 100mph doing drag launches from a standstill. Every time it would spin all 4 if it ever broke traction, which was dependent on how aggressive the throttle was applied.
It’s mechanically impossible to spin just one wheel faster than the other three when the front and rear are locked in the center with a spool. A spike in rpm on any one wheel would require a spike in rpm from one of the wheels on the opposite end of the car. You can only spin one front and one rear wheel simultaneously or all 4, never 1 or 3.

Whether or not that's true (not saying it isn't), wouldn't thicker F/R diff oil make the steering inputs a little more muted, thus lending to stability?

 

[LibertyMKiii]

I am in the same boat. I have tried locked and seemed ok for me.
I see others indicate 10k is fine. I think maybe so for long chassis cars, but short wheelbase chassis like the Typhon seem to be more sensitive to this.

The best reference I have is real drag cars which always run locked/spools in the differentials.

It is also worth mentioning that this guy run locked diffs and knew what he was doing. I am really stunned that his world record still holds all these years later.

 

[GMballistic]

Imho the reason it doesn't really matter for speed running whether you're running 10K or 1Million etc is because and this is the caveat, if you're driving the car correctly for a speed run; being progressive with the throttle, going in a straight line, running on a decent surface with good traction/from the surface & your tyres then the differentials should be doing nothing other than supplying equal power to all four of your wheels.


However, our cars have open/standard differentials, so if one wheel was to loose traction because for example it was on a slippery surface whereas the opposite wheel on the same axle still had good traction due to the way the differential works more power would be supplied to the wheel that has lost traction which just makes things worse in that scenario.
If we use thicker diff fluids or lockers then you can limit or stop altogether the differential working in that way meaning that power is supplied to both wheels on the same axle more evenly or as a constant regardless of surface conditions.

Personally I run 100K in my 6S Typhon front and rear differentials which has worked great for me thus far so I'm sticking to that. My Limitless which is as yet untested I have decided to go a lot thicker at 500K for the front and rear differentials.

Overall this is down to driver preference, ...what works for me with the cars I run, the set ups I have and the roads I run on may not work for the next person. That's why practice and testing is so important.

 

[Mr.Duke]

I don’t understand where the idea that only 1 wheel can lose traction when running a center spool comes from. Can we all acknowledge that its not mechanically possible as long as the front and rear center driveshafts are locked together and turning the same rpm? The only way you can experience a spike in rpm from the left or right side of the vehicle is for the opposing axle to lose traction on one side or the other at the same. There’s never a time where only 1 wheel diffs out (spikes in rpm in relation to the other 3).