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Old 07-05-2014, 01:16 AM   #1
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Default Front spool dif on Touring Car racer, why / why not?

Hi,

I have a mildly modified Tamiya TT-01 to race in the Dutch Tamiya Cup Challenge. I can only use Tamiya parts, of course. Now I still have a spool 'dif' and axles from when I used the car as a drifter, I used it in the rear axle. I read a lot of racers use a spool in the front. I don't understand why. So, two questions:
What does it do in terms of handling?
Would it make sense to use it in a relatively slow class like the Top Stock, on my TT-01 with a Carson Cup Machine motor?

Thanks!

Hugo
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Old 07-05-2014, 01:42 AM   #2
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A spool helps you get power down quickly out of the corner. The main issue is that it can reduce the amount of initial steering of the car as opposed to a diff as both front wheels rotate at the same rate.

You will notice a difference in any class, a spool is also usually a little lighter which helps.

A compromise used to be a one way, this gives you free wheeling front wheels on the way into a corner and a spool effect out of the corner. The issue is that you only have the rear wheels that you can use to brake, which can unsettle the car.

An option which is a good alternative is to get a diff and place some 1000,000 weight diff oil in it. This gives you a very stiff diff, providing a good amount of pull out of a corner but with a little diff action to help the initial corner entry.

I have done the above on my TT02 and it works well, especially as thinner oils wil just leak out of the diff as it is not a sealed oil diff.

Another tip is to change the diff internals to the TT02 plastic gears. They are much lighter than the TT01 steel gears and reduce weight on the drive train making acceleration and throttle response much better.
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Old 07-05-2014, 01:48 AM   #3
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Aha, thanks. I have TT-02 difs in there, and I could make the front one very stif using Tamiya anti ware grease. I just found my spool is actually a one-way, I now remember glueing the stock dif shut (I found the old dif) for the rear, and using the one-way in the front. This helps unsettle the rear for drifting, not something for racing.

Thanks,

Hugo
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Old 07-05-2014, 12:02 PM   #4
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I am not familiar with what motors are allowed in the Tamiya cup but if you're just running 21.5 (even boosted) I would say the spool won't help you much at all. For low power motors, I would recommend a one way (in diff configuration) front and make sure you're not lifting the inside wheel (keep front droop over roll). This is because the one way will basically make your car a three wheel drive around corners with the outside front wheel freewheeling and the inside doing the pulling. This means your inside wheel will spin at max revs, not giving away spin through a normal diff. The outer wheel will be freewheeling because it will spin faster than the diff, hence it won't be under power. This is what gives you better pull out of corners with a one way. A spool will force the front wheels to fight each other and the wheel with less grip will lose. This of course will be the unloaded inside wheel, so the outside will drive, but being on the outside it has to travel further, hence lower speed.

In stock (17.5), superstock (13.5) or mod this is not a problem because there is so much more power available, but still a compromise (and mod cars have very little roll anyway). On the other hand a one way in such a car would be drivable only if you have the reflexes of a young squirrel on speed.
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Old 07-05-2014, 02:57 PM   #5
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I run yokomo bd5 and bd7 for vta and usgt, both lower power motors and it's faster with a spool out of the corners than running a diff up front.
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Old 07-05-2014, 02:59 PM   #6
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I prefer a Diff in the front with thick oil. Spools never "felt" right to me. I still use a one way diff on very large tracks.
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Old 07-05-2014, 09:39 PM   #7
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Quote:
Originally Posted by b20btec View Post
I run yokomo bd5 and bd7 for vta and usgt, both lower power motors and it's faster with a spool out of the corners than running a diff up front.
Are we talking 21.5? Or 17.5? Boosted or not? Have you tried a one way?
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Old 07-06-2014, 03:03 PM   #8
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21.5 and 25.5 pretty rare I would run any type of diff up front. Yes I have tried a one way when I was running a evo5 chassis, swapped it out to a tb03 spool.
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Old 07-07-2014, 12:29 AM   #9
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Hi everyone,

for 1:10 on-road modified class, what putty is the best: RIDE Diff putty hardness #45 or RIDE Diff putty hardness #70?

Thanks for answering,
G-rem
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