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Old 09-14-2015, 09:50 AM   #6106
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This is due to the non Newtonian properties of silicon oil.
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Old 09-14-2015, 04:58 PM   #6107
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Originally Posted by EDWARD2003 View Post
Has anyone had issues with the 2013-2014 differentials "gumming up" like slightly locking up after a run? Or even after a fresh build?

I've recently built three differentials with fresh orings, greased properly, oil (mugen differential oil). All meticulously done. When sitting at a cool state the differential is smooth and free moving. However, a couple days ago I was testing my motors boost settings and decided to hold one of the tires to act as a bit of a load for the motor. After a few burps of the throttle, I noticed the differential would start to gum up feeling. It's only when the differential is worked hard.

I decided to take apart and rebuild the differential again. I thought I might have been too conservative with the grease on the outdrives and orings. Once again, under a cool state it's butter smooth, then once I burp the throttle while holding the tire it would do it again.

Do you think the differential is building up some internal pressure when it's getting warm? Thus putting pressure on the outdrives?

What are your thoughts?

I build and measure the weights of each differential. Currently at 1,000 mugen with 15.0g on digital scales.

Or should I just stoping doing burping the throttle while holding the tire? Lol
I think you are just experiencing thermal expansion. When you blip the throttle, you make the differential work way more and faster than it would under normal situation. Friction makes heat build up, therefore the "sticky" feeling. I wouldn't worry about it. If it were really a problem, you'd see it pop on the forums quite a bit, and while yokomo's diff aren't the best in the business, they're still pretty good.

Martin Paradis

Last edited by rhodopsine; 09-14-2015 at 05:02 PM. Reason: Darn auto correction...
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Old 09-14-2015, 11:21 PM   #6108
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Default tyre wear

Does anyone have any pics or knowledge about when tyres have gone past or are going past there grip points

what should a tyre look like when it still has good grip or rubber left. Jst need some sort of gauge so I can try and get this understeer lack of traction under control
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Old 09-14-2015, 11:39 PM   #6109
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Originally Posted by rhodopsine View Post
I think you are just experiencing thermal expansion. When you blip the throttle, you make the differential work way more and faster than it would under normal situation. Friction makes heat build up, therefore the "sticky" feeling. I wouldn't worry about it. If it were really a problem, you'd see it pop on the forums quite a bit, and while yokomo's diff aren't the best in the business, they're still pretty good.

Martin Paradis
Thank you for your input. I figured it was something along those lines. Much appreciated for your input.
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Old 09-15-2015, 06:20 AM   #6110
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I gave you some info on helping you with your bad handling BD7 over the page BruceCampbell
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Old 09-15-2015, 06:32 AM   #6111
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Does anyone have any pics or knowledge about when tyres have gone past or are going past there grip points

what should a tyre look like when it still has good grip or rubber left. Jst need some sort of gauge so I can try and get this understeer lack of traction under control
I run them till the death ring shows up on the inside contact patch. Pros run them once or twice and toss them. Comes down to how endless your budget is I guess.
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Old 09-15-2015, 06:41 AM   #6112
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Sadly, practice and build setup and car performance experience from mainly running on used tires are not optimal when going to a big race on new tires.
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Old 09-15-2015, 06:45 AM   #6113
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Speed 6, try removing the front motor mount screws underneath the chassis and put a long grub screw to secure the mount so it has no chance of coming loose in a heavy impact, Tamiya often run there cars like this with the 419, they have options by just removing screws though
Front motor mount screws? not sure I understand what u mean here
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Old 09-15-2015, 02:09 PM   #6114
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Front motor mount screws? not sure I understand what u mean here
4 motor mount screws hold the motor mount in place from underneath, taking the front two out increases flex in that area and the grub screw just keeps it secure
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Old 09-15-2015, 11:39 PM   #6115
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Heya guys, looking for a bit of help. My first weekend with a touring car the other week and I was running setup as described below.
Car was very pointy into the corners (so much so that for the first lap or two I would clip apexes), and a little pushy on the way out.
What should I be looking to do in order to calm the steering down on the way in and gain a little from mid corner out?

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rc_square24

front
shocks, 450 cst, 3 holes 1.1, 20% rebound, pink spring, black bladder.
standard toe blocks, camber 1.5, toe out 1, droop 6mm (under block)
No roll center shims, short camber links
0.5 bumper steer, 1 mm ackerman
Ride height 5.2mm
Spool, 4 degree c hubs

Rear
shocks, 450 cst, 3 holes 1.1, 20% rebound, blue spring, black bladder.
standard toe blocks, camber 1.5, toe out 3, droop 5mm (under block)
No roll center shims, short camber links
3000 cst in the rear diff
Ride height 5.4mm

Body, mazda 6 speed
Tires, sorex 28 with black insert
All plastic parts are grafite, and I am using roche dcj in front
Esc Muchmore ETS, Motor MuchMore 17.5T timming 20, Ratio 4.5


Thanks
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Would go for a slightly different setup. 500 shock oil all round (no bumps on carpet) and if you feel you need front to be less aggressive go for Blue spring fronts as well.

Front and rear 0.5mm or even 1mm spacer under camber both ends.

Rear camber 2 degrees

5mm front ride height

5.2mm rear ride height

4.5 rear droop
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Old 09-15-2015, 11:54 PM   #6116
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Originally Posted by Glarke View Post
Heya guys, looking for a bit of help. My first weekend with a touring car the other week and I was running setup as described below.
Car was very pointy into the corners (so much so that for the first lap or two I would clip apexes), and a little pushy on the way out.
What should I be looking to do in order to calm the steering down on the way in and gain a little from mid corner out?
Is this on carpet or asphalt?
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Old 09-16-2015, 12:04 AM   #6117
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Sorry - On carpet. No traction additive and theyve found that schumacher mini-pins or rally tires work best. I ran yellow pins rear and yellow rallys front. Im going to try some green pins on front next time around too.
The car was quick. I was able to post a fastest lap. It was just awkward to drive which resulted in a few mistakes which cost me.
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Old 09-16-2015, 05:45 AM   #6118
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Does anyone have a spring chart for the yokomo springs with the correct rates?
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Old 09-16-2015, 02:53 PM   #6119
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Quote:
Originally Posted by EDWARD2003 View Post
Has anyone had issues with the 2013-2014 differentials "gumming up" like slightly locking up after a run? Or even after a fresh build?

I've recently built three differentials with fresh orings, greased properly, oil (mugen differential oil). All meticulously done. When sitting at a cool state the differential is smooth and free moving. However, a couple days ago I was testing my motors boost settings and decided to hold one of the tires to act as a bit of a load for the motor. After a few burps of the throttle, I noticed the differential would start to gum up feeling. It's only when the differential is worked hard.

I decided to take apart and rebuild the differential again. I thought I might have been too conservative with the grease on the outdrives and orings. Once again, under a cool state it's butter smooth, then once I burp the throttle while holding the tire it would do it again.

Do you think the differential is building up some internal pressure when it's getting warm? Thus putting pressure on the outdrives?

What are your thoughts?

I build and measure the weights of each differential. Currently at 1,000 mugen with 15.0g on digital scales.

Or should I just stoping doing burping the throttle while holding the tire? Lol
This is from filling the diffs with too much oil. The diff will hydro lock if it gets too hot, hotter than just sitting on the bench. I'd recommend filling the diffs with less oil and see if you get the same result. I would also put a little grease on the shaft of the outdrive before you assemble the diff. If that fixes your issue then you'll probably need to go to higher cst oil to compensate for the lighter feel.
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Old 09-16-2015, 07:41 PM   #6120
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Edward2003-

This is also because you are using too thin of an oil. Go up much higher in viscosity and use less oil. The operating temperature of the diff is much higher than bench testing so you will have to do a little trial and error on the feel that you are pursuing. A warm diff will be a more accurate indicator of diff action. Generally people prefer 5k-7k these days.
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