50/50 power split vs. other

CMS-GT4

CMS-GT4

Active member
Stock alltrac/gt4 power dist. is 50/50. To reduce nose plow, and make the car handle better in the tighter turns (short course), over steer needs to be induced in the alltrac.

As much can be done to the suspension and rear lsd can be added to help in this, but I feel the alltrac can use more.
I was looking into having the gear ratio in the center diff modified to change the power split. Not sure how much it would cost, but I am sure it would not be cheap.

I was thinking F35/R65.
Since this is going to be a track car (mostly autox) the reliability issues on the center diff are not as much of an issuse. The fluid in the center diff can also be upgraded to handle more stress like the trd units.


I was thinking about the tire size difference on some cars in the gt4 hyper rev mag. They run wider/ larger dia. tires in the front vs. the rear.
I see this as a cheap way to change the front to rear rolling ratio to act simular to adjusting the power split.

For exaple.
I am running 205/40/17 on a 17x7" wheel. (This is the same ratio as stock) Split is 50/50

Here is a tire/wheel size listed in Hyper rev.
This is the garage cruise gt4
Wheels (17x9.5)
Tires F(225/40/17) R(245/45/17)
Since the dia. of the rear tire is larger the wheel is moving at a faster rate.

Here is a link for reference.
http://www.miata.net/garage/tirecalc.html

I think I am catching on to this correctly, but give me an idea of what you guys think. This may be one of the key secrets to making the gt4 handle. This may also explain why Bob has larger tires in the rear.
 
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alltracman78

Active member
I'm not too well versed in trans/diff stuff yet, so I might be wrong on this, but what the hell :shrug:

What if you loosened the front diff plates (do we have those?), and tightened the center and rear? Wouldn't that send more power to the rear? Of course you would have to disasemble the diffs. :|
 
CMS-GT4

CMS-GT4

Active member
Do you mean as in a clutch type diff?

The front diff is an open diff, and the center is a viscous lock.
The rear is either torsen or open.

A clutch type from a MR2 can be modified for the front, and cusco makes a clutch type for the rear of a gt4, so it may be a possible mod. I have heard that using a clutch type in the front of an awd car causes understeer, and can whip the wheel out of your hands.

You idea may work, but it would be a matter of how much oversteer could be added in relation to the added understeer.
 
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InitialD93

New member
didnt u say that my rear diff was a clutch type at PF.

and stock diameter for a 17" rim is 215/40/17 according to the miata calculator i believe havnt checked in a while.
 
CMS-GT4

CMS-GT4

Active member
You may have had larger tires on your stock rims.

Stock tire size is 215/50/15
The tire calc says that 205/40/17 is the correct size. I wish I went with a wider tire. These were too narrow for the weight of the car.

The open diff concist of a center gear that is turned and has to gears on the side that rotate with it, and turn when the is a speed difference.

Here is a great piece on all diffs.
http://auto.howstuffworks.com/differential.htm
 
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illGT4

New member
Hey Coldiron,

I was able to get more oversteer by simply adding H&R spacers to the rear. Further oversteer was added by increasing the dampening in the rear.

I now have the ability to throttle oversteer.. Something that I just LOVE! :)

Nothing like an immediate U turn with a good press of the accelerator.

Keep up the Excellent (suspension) work,
 
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illGT4

New member
AWDios":358j1r6x said:
yeah, and shouldn't spacers give you understeer?
Click to expand...

Not that I noticed.

Why do you believe it will add understeer? I'm open for debate. ;)

I'm thinking a widening track in the rear to contribute to oversteer.. a.k.a. rear skid.

In the dirt anyway.. this is what I've felt. At the time I had whiteline stb front and rear.

After installing the DMS I was able to add even more oversteer by increasing the dampening in the rear.

Tha alltrac is very big understeering pig from the factory.. I don't believe widening the track in the rear will add more understeer a.k.a. front skid.

Regards,
 
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AWDios

New member
It just seems like with a wider wheel base in the rear it would be harder to cause the rear to break loose. And I've heard from others that they have experienced more understeer, and to me it makes more sense than what you're saying. However I can't argue with results.
 
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AWDios

New member
I notice that, and I don't know if it's a typo, but they say to lessen oversteer you only bring in the front.
 
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illGT4

New member
I'm def. not saying that I am right.. I'm reading things for both ends of the arguement now...

Either way, I love the "looks" of the rear with the spacers. But we all agree on that. :)

I would much rather have wheels with different offset to fill the rear .. but that leads to other problems like tire rotation. And the fact that I have a different sets of wheels and tires.. and I want them to fill the rear all the time.. not just with one set...
 
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illGT4

New member
AWDios":10ogsseb said:
I notice that, and I don't know if it's a typo, but they say to lessen oversteer you only bring in the front.
Click to expand...

Which would be the same as having a wider rear track, no?
 
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edv-tek

New member
To reduce nose plow, and make the car handle better in the tighter turns (short course), over steer needs to be induced in the alltrac.
Click to expand...

I think you are talking about an anti-lift kit. With a kit on the St165 you can go into a controllable drift with ease. And it has little or no understeer. It was most likely why they used the ST165 for racing right up to 1992.
 
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turbo4wd

Moderator
AWDios":1j51el63 said:
It just seems like with a wider wheel base in the rear it would be harder to cause the rear to break loose. And I've heard from others that they have experienced more understeer, and to me it makes more sense than what you're saying. However I can't argue with results.
Click to expand...

This is true and what I experienced myself. Widening the rear track does nothing to help induce oversteer. My rear swaybar did that when I installed that.
 
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